全文获取类型
收费全文 | 4925篇 |
免费 | 598篇 |
国内免费 | 3篇 |
专业分类
耳鼻咽喉 | 24篇 |
儿科学 | 358篇 |
妇产科学 | 150篇 |
基础医学 | 873篇 |
口腔科学 | 95篇 |
临床医学 | 485篇 |
内科学 | 1079篇 |
皮肤病学 | 57篇 |
神经病学 | 325篇 |
特种医学 | 173篇 |
外科学 | 497篇 |
综合类 | 140篇 |
一般理论 | 2篇 |
预防医学 | 543篇 |
眼科学 | 88篇 |
药学 | 364篇 |
中国医学 | 16篇 |
肿瘤学 | 257篇 |
出版年
2021年 | 63篇 |
2020年 | 51篇 |
2019年 | 74篇 |
2018年 | 107篇 |
2017年 | 63篇 |
2016年 | 53篇 |
2015年 | 89篇 |
2014年 | 103篇 |
2013年 | 152篇 |
2012年 | 237篇 |
2011年 | 240篇 |
2010年 | 119篇 |
2009年 | 97篇 |
2008年 | 202篇 |
2007年 | 202篇 |
2006年 | 199篇 |
2005年 | 216篇 |
2004年 | 220篇 |
2003年 | 197篇 |
2002年 | 194篇 |
2001年 | 177篇 |
2000年 | 166篇 |
1999年 | 157篇 |
1998年 | 86篇 |
1997年 | 55篇 |
1996年 | 72篇 |
1995年 | 50篇 |
1994年 | 56篇 |
1993年 | 42篇 |
1992年 | 128篇 |
1991年 | 116篇 |
1990年 | 104篇 |
1989年 | 114篇 |
1988年 | 118篇 |
1987年 | 98篇 |
1986年 | 97篇 |
1985年 | 81篇 |
1984年 | 60篇 |
1983年 | 44篇 |
1980年 | 37篇 |
1979年 | 52篇 |
1978年 | 46篇 |
1977年 | 35篇 |
1976年 | 38篇 |
1974年 | 37篇 |
1973年 | 41篇 |
1972年 | 38篇 |
1971年 | 46篇 |
1969年 | 36篇 |
1967年 | 40篇 |
排序方式: 共有5526条查询结果,搜索用时 0 毫秒
81.
Stevenson VL Parker GJ Barker GJ Birnie K Tofts PS Miller DH Thompson AJ 《Journal of the neurological sciences》2000,178(2):81-87
OBJECTIVE: To investigate the variation in T1 and T2 relaxation times of normal appearing white matter (NAWM) and lesions in multiple sclerosis (MS) throughout the brain. BACKGROUND: The magnetic resonance imaging (MRI) sequence fast FLAIR (fluid attenuated inversion recovery) has demonstrated overall increased lesion detection when compared to conventional or fast spin echo (FSE) but fewer lesions in the posterior fossa and spinal cord. The reasons for this are unknown, but may be due to variations in the T1 and T2 relaxation times within NAWM and MS lesions. METHOD: Ten patients and 10 controls underwent MRI of the brain which involved FSE, fast FLAIR and the measurement of T1 and T2 relaxation times. RESULTS: Of 151 lesions analysed (22 infra-tentorial, 129 supra-tentorial), eight were missed by the fast FLAIR sequence. T1 and T2 relaxation times in normal controls were longer in the infra-tentorial, than supra-tentorial, region. Patient NAWM relaxation times were prolonged compared with control values in both regions. Lesions demonstrated longer relaxation times than either control white matter or patient NAWM in both regions, however this difference was less marked infra-tentorially. The eight posterior fossa lesions not visible on the fast FLAIR sequence were characterised by short T1 and T2 relaxation times which overlapped with the patient NAWM for both T1 and T2 and with control values for T2 relaxation times. CONCLUSION: Both lesion and NAWM relaxation time characteristics vary throughout the brain. The T1 and T2 relaxation times of infra-tentorial lesions are closer to the relaxation times of local NAWM than supra-tentorial lesions, resulting in reduced contrast between posterior fossa lesions and the background NAWM. Consequently the characteristics of some lesions overlap with those of NAWM resulting in reduced conspicuity. By utilising this information, it may be possible to optimise fast FLAIR sequences to improve infra-tentorial lesion detection. 相似文献
82.
Premature treatment termination by angry patients with combat-related post-traumatic stress disorder
Angry patients with conjoined post-traumatic stress disorder often direct their anger at health care providers during the course of treatment. Such misplaced anger can interfere with treatment. Emerging treatments for trauma-related anger are effective. However, even in the course of psychotherapy for trauma-related anger, these patients direct anger at their therapists, compromising the treatment alliance and increasing the likelihood of premature termination. A case example is presented to illustrate the effect of anger on the treatment alliance. A therapeutic strategy is proposed to reduce the likelihood of premature treatment termination in these high-risk patients. This strategy may also be helpful in primary care contexts. 相似文献
83.
R Francavilla VL Miniello L Brunetti ME Lionetti L Armenio 《Acta paediatrica (Oslo, Norway : 1992)》2003,92(S441):101-104
A major complication of cholestasis is fat malabsorption related to decreased intestinal bile acids, which leads to malnutrition and fat-soluble vitamin deficiency. The impaired excretion of bile acids leads to a low intraluminal micellar concentration that causes long-chain triglyceride lipolysis and absorption to be ineffective. Medium-chain triglycerides (MCTs) are more readily absorbed when there are low concentrations of bile acids and therefore are a good source of fat calories; MCTs can be administered as MCT-containing formulas. In those children who are unable to take sufficient calories by mouth, it is important to start nocturnal enteral feeding to improve nutritional status. In infants with cholestasis, the absorption of fat-soluble vitamins (A, D, E and K) that require bile acids is also impaired, and supplementation is mandatory. Vitamin K deficiency may be responsible for hypoprothrombinaemia, which may lead to bleeding diathesis, Vitamin K (phytomenadione) should therefore be promptly administered intravenously, at a dose of 1 mg. Chronic vitamin E (α-tocopherol) deficiency is associated with a progressive neuromuscular syndrome that can cause cerebellar ataxia, areflexia and peripheral neuropathy. Supplements are given orally in doses of 3–5 times the normal requirement if cholestasis is incomplete. In complete cholestasis, supplements must be given intramuscularly at monthly intervals. In infants who fail to thrive, dietary supplements of carbohydrate polymers and MCTs are required. 相似文献
84.
Exposure to perfluorooctane sulfonate during pregnancy in rat and mouse. I: maternal and prenatal evaluations. 总被引:1,自引:0,他引:1
Julie R Thibodeaux Roger G Hanson John M Rogers Brian E Grey Brenda D Barbee Judy H Richards John L Butenhoff Lisa A Stevenson Christopher Lau 《Toxicological sciences》2003,74(2):369-381
The maternal and developmental toxicities of perfluorooctane sulfonate (PFOS, C8F17SO3-) were evaluated in the rat and mouse. PFOS is an environmentally persistent compound used as a surfactant and occurs as a degradation product of both perfluorooctane sulfonyl fluoride and substituted perfluorooctane sulfonamido components found in many commercial and consumer applications. Pregnant Sprague-Dawley rats were given 1, 2, 3, 5, or 10 mg/kg PFOS daily by gavage from gestational day (GD) 2 to GD 20; CD-1 mice were similarly treated with 1, 5, 10, 15, and 20 mg/kg PFOS from GD 1 to GD 17. Controls received 0.5% Tween-20 vehicle (1 ml/kg for rats and 10 ml/kg for mice). Maternal weight gain, food and water consumption, and serum chemistry were monitored. Rats were euthanized on GD 21 and mice on GD 18. PFOS levels in maternal serum and in maternal and fetal livers were determined. Maternal weight gains in both species were suppressed by PFOS in a dose-dependent manner, likely attributed to reduced food and water intake. Serum PFOS levels increased with dosage, and liver levels were approximately fourfold higher than serum. Serum thyroxine (T4) and triiodothyronine (T3) in the PFOS-treated rat dams were significantly reduced as early as one week after chemical exposure, although no feedback response of thyroid-stimulating hormone (TSH) was observed. A similar pattern of reduction in T4 was also seen in the pregnant mice. Maternal serum triglycerides were significantly reduced, particularly in the high-dose groups, although cholesterol levels were not affected. In the mouse dams, PFOS produced a marked enlargement of the liver at 10 mg/kg and higher dosages. In the rat fetuses, PFOS was detected in the liver but at levels nearly half of those in the maternal counterparts, regardless of administered doses. In both rodent species, PFOS did not alter the numbers of implantations or live fetuses at term, although small deficits in fetal weight were noted in the rat. A host of birth defects, including cleft palate, anasarca, ventricular septal defect, and enlargement of the right atrium, were seen in both rats and mice, primarily in the 10 and 20 mg/kg dosage groups, respectively. Our results demonstrate both maternal and developmental toxicity of PFOS in the rat and mouse. 相似文献
85.
Early discharge for patients with exacerbations of chronic obstructive pulmonary disease: a randomized controlled trial 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Thorax》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Cotton MM Bucknall CE Dagg KD Johnson MK MacGregor G Stewart C Stevenson RD 《Thorax》2000,55(11):902-906
BACKGROUND: We have previously reported the use of a hospital based respiratory nurse service (Acute Respiratory Assessment Service, ARAS) to support home treatment of patients with exacerbations of chronic obstructive pulmonary disease (COPD). A controlled trial was undertaken to compare early discharge with home treatment supported by respiratory nurses with conventional hospital management of patients admitted with exacerbations of COPD. METHODS: Patients with COPD admitted as emergencies were identified the next working day. They were eligible for inclusion in the study if the differential diagnosis included an exacerbation of COPD, but were excluded if other medical conditions or acidotic respiratory failure required inpatient investigation or management. Of 360 patients reviewed, 209 were being assessed for other active medical problems and were excluded, 33 potential participants were already involved in research studies and so were ineligible, and 37 did not wish to participate in the study. Eighty one patients were randomised to receive conventional inpatient care (n=40) or to planned early discharge the next working day (n=41). Those discharged early continued treatment at home under the supervision of specialist respiratory nurses. Outcome measures were readmission, additional hospital days, and deaths within 60 days of initial admission. Process measures included number of visits, duration of follow up by the respiratory nurse, and additional treatment provided to support early discharge. RESULTS: On an intention to treat basis, a policy of early discharge reduced inpatient stay from a mean of 6.1 (range 1-13) days with conventional management to 3.2 (1-16) days with an early discharge policy. Twelve patients (30% conventional management, 29.3% early discharge) were readmitted in each group giving a mean difference in readmission of 0.7% (95% CI of the difference -19.2 to 20.6). In the conventional management group readmitted patients spent a mean of 8.75 additional days in hospital compared with 7.83 days in the early discharge group, giving a mean difference of 0.92 days (95% CI of the difference -6.5 to 8.3). There were two deaths (5%) in the conventional management group and one (2.4%) in the early discharge group, a mean difference of 2.6% (95% CI of the difference -5.7 to 10.8). CONCLUSIONS: Patients with acute exacerbations of COPD uncomplicated by acidotic respiratory failure or other medical problems can be discharged home earlier than is current practice with support by visiting respiratory nurses. No difference was found in the subsequent need for readmission. 相似文献
86.
Neil E Martin Thomas B Brunner Krystina D Kiel Thomas F DeLaney William F Regine Mohammed Mohiuddin Ernest F Rosato Daniel G Haller James P Stevenson Debbie Smith Barnali Pramanik Joel Tepper Wesley K Tanaka Briggs Morrison Paul Deutsch Anjali K Gupta Ruth J Muschel W Gillies McKenna Eric J Bernhard Stephen M Hahn 《Clinical cancer research》2004,10(16):5447-5454
PURPOSE: Preclinical and clinical studies have demonstrated that inhibition of prenylation can radiosensitize cell lines with activation of Ras and produce clinical response in patients with cancer. The aim of this study was to determine the maximally tolerated dose of the dual farnesyltransferase and geranylgeranyltransferase I inhibitor L-778,123 in combination with radiotherapy for patients with locally advanced pancreatic cancer. EXPERIMENTAL DESIGN: L-778,123 was given by continuous intravenous infusion with concomitant radiotherapy to 59.4 Gy in standard fractions. Two L-778,123 dose levels were tested: 280 mg/m2/day over weeks 1, 2, 4, and 5 for dose level 1; and 560 mg/m2/day over weeks 1, 2, 4, 5, and 7 for dose level 2. RESULTS: There were no dose-limiting toxicities observed in the eight patients treated on dose level 1. Two of the four patients on dose level 2 experienced dose-limiting toxicities consisting of grade 3 diarrhea in one case and grade 3 gastrointestinal hemorrhage associated with grade 3 thrombocytopenia and neutropenia in the other case. Other common toxicities were mild neutropenia, dehydration, hyperglycemia, and nausea/vomiting. One patient on dose level 1 showed a partial response of 6 months in duration. Both reversible inhibition of HDJ2 farnesylation and radiosensitization of a study patient-derived cell line were demonstrated in the presence of L-778,123. K-RAS mutations were found in three of the four patients evaluated. CONCLUSIONS: The combination of L-778,123 and radiotherapy at dose level 1 showed acceptable toxicity in patients with locally advanced pancreatic cancer. Radiosensitization of a patient-derived pancreatic cancer cell line was observed. 相似文献
87.
David Crook Lecturer Ian F. Godsland Senior Lecturer Jane Hull Research Nurse John C. Stevenson Director 《BJOG : an international journal of obstetrics and gynaecology》1997,104(3):298-304
Objective To assess serum lipid and lipoprotein concentrations and oral glucose tolerance in postmenopausal women treated with 17β-oestradiol (2 mg/day) and cyclical dydrogesterone (10 mg/day for 14 days per 28 day cycle).
Design A 24 month prospective study of 29 women acting as their own controls. On-treatment samples were taken during the combined (oestrogen–progestogen) phase of therapy.
Setting Metabolic research unit in London.
Population Postmenopausal women with no previous exposure to hormone replacement therapy attending a menopause clinic in a London hospital.
Methods Fasting serum sampling and oral glucose tolerance testing.
Main outcome measures Serum lipids and lipoprotein concentrations and plasma glucose, insulin and C-peptide responses to an oral glucose load.
Results Restricting the analysis to the 17 women who completed the study, no effect was seen on serum triglyceride concentrations. There was a mean fall of 5.9% (95% CI 1.2 to −13.0) in concentrations of serum total cholesterol, reflecting the balance of a 10.7% fall (95% CI 4.3 to −25.8) in low density lipoprotein cholesterol concentrations and a 16.3% increase (95% CI 7.3 to −25.3) in those of high density lipoproteins. Fasting glucose concentrations and glucose tolerance test responses were unchanged. Fasting insulin concentrations fell substantially (–41.6%, 95% CI −23.4 to −59.8) with falls also being seen in insulin responses to glucose. Fasting C-peptide concentrations increased by 36.2% (95% CI 9.17 to 63.3), with no consistent effect on C-peptide responses to glucose.
Conclusions Dydrogesterone did not appear to oppose the potentially beneficial effects of oestradiol on insulin or either low or high density lipoproteins, making the combination with 17β-oestradiol a potentially useful option for postmenopausal women particularly those at risk of cardiovascular disease or diabetes mellitus. 相似文献
Design A 24 month prospective study of 29 women acting as their own controls. On-treatment samples were taken during the combined (oestrogen–progestogen) phase of therapy.
Setting Metabolic research unit in London.
Population Postmenopausal women with no previous exposure to hormone replacement therapy attending a menopause clinic in a London hospital.
Methods Fasting serum sampling and oral glucose tolerance testing.
Main outcome measures Serum lipids and lipoprotein concentrations and plasma glucose, insulin and C-peptide responses to an oral glucose load.
Results Restricting the analysis to the 17 women who completed the study, no effect was seen on serum triglyceride concentrations. There was a mean fall of 5.9% (95% CI 1.2 to −13.0) in concentrations of serum total cholesterol, reflecting the balance of a 10.7% fall (95% CI 4.3 to −25.8) in low density lipoprotein cholesterol concentrations and a 16.3% increase (95% CI 7.3 to −25.3) in those of high density lipoproteins. Fasting glucose concentrations and glucose tolerance test responses were unchanged. Fasting insulin concentrations fell substantially (–41.6%, 95% CI −23.4 to −59.8) with falls also being seen in insulin responses to glucose. Fasting C-peptide concentrations increased by 36.2% (95% CI 9.17 to 63.3), with no consistent effect on C-peptide responses to glucose.
Conclusions Dydrogesterone did not appear to oppose the potentially beneficial effects of oestradiol on insulin or either low or high density lipoproteins, making the combination with 17β-oestradiol a potentially useful option for postmenopausal women particularly those at risk of cardiovascular disease or diabetes mellitus. 相似文献
88.
This study aims to evaluate the use of the United States National Center for Health Statistics (NCHS) weight-for-height centiles (WHC) in screening children with cerebral palsy (CP) for depleted body fat and to identify an alternate screening method. Growth data from 276 children aged from 3 to 12 years with CP were analyzed retrospectively. Height or a proxy for height, mid-upper arm circumference, weight, and skinfold thicknesses were recorded. Mid-upper arm fat area was calculated for each participant. The sensitivities and specificities of WHC and a number of alternative anthropometric screening methods for identifying participants with severely depleted fat stores were determined. WHC <10th centile failed to identify 45% of children with severely depleted fat stores. Triceps skinfold thickness <10th centile identified 96% of malnourished children. WHC standards lack adequate sensitivity for identification of severely depleted fat stores in children with CP. Use of triceps skinfold thickness, using cut-off value of <10th centile for age and sex, is recommended to screen for suboptimal fat stores in children with CP. 相似文献
89.
广州、南宁市汽车安全带佩戴状况调查 总被引:3,自引:0,他引:3
目的 调查广州、南宁市汽车安全带佩戴情况。方法 采用随机抽样的方法,按照3种不同类型的道路选取观察点,在4个不同时间段对目标车辆进行观察。结果 司机安全带正确佩戴率南宁市(63.8%)高于广州市(49.3%),而不正确佩戴率广州市(22.9%)高于南宁市(8.1%);乘客安全带佩戴率广州市高于南宁市,包括正确佩戴率和不正确佩戴率;安全带佩戴率受道路类型、时间、性别和车型等的影响,正确佩戴率高速路高于其他道路、白天高于晚上、女性高于男性、小型汽车高于其他车型,不正确佩戴率工作151高于周末。结论 广州市男性出租车司机安全带不正确佩戴率高;两地区周末和晚上佩戴安全带率较低,应加大执法力度;加强宣传教育,提高司乘人员佩戴安全带的意识。 相似文献
90.
The HOPA Gene Dodecamer Duplication Is Not a Significant Etiological Factor in Autism 总被引:3,自引:0,他引:3
Michaelis RC Copeland-Yates SA Sossey-Alaoui K Skinner C Friez MJ Longshore JW Simensen RJ Schroer RJ Stevenson RE 《Journal of autism and developmental disorders》2000,30(4):355-358
A recent study has suggested that a dodecamer duplication in the HOPA gene in Xq13 may occur in a significant portion of male patients with autism. We have determined the incidence of this duplication in 202 patients from the South Carolina Autism Study. The incidence of the duplication was not significantly different between patients and controls. Three of the female patients inherited the duplication from nonautistic fathers. In addition, there was no systematic skewing of X inactivation in the female patients with the duplication, or in nonautistic mothers and sisters with the duplication. These findings suggest that the dodecamer duplication in the HOPA gene does not play a significant role in the etiology of autism. 相似文献