首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4459篇
  免费   423篇
  国内免费   51篇
耳鼻咽喉   40篇
儿科学   145篇
妇产科学   95篇
基础医学   581篇
口腔科学   72篇
临床医学   558篇
内科学   768篇
皮肤病学   44篇
神经病学   373篇
特种医学   228篇
外科学   621篇
综合类   72篇
一般理论   3篇
预防医学   480篇
眼科学   49篇
药学   438篇
  1篇
中国医学   3篇
肿瘤学   362篇
  2021年   52篇
  2020年   33篇
  2019年   44篇
  2018年   48篇
  2017年   39篇
  2016年   58篇
  2015年   54篇
  2014年   93篇
  2013年   154篇
  2012年   210篇
  2011年   218篇
  2010年   121篇
  2009年   100篇
  2008年   159篇
  2007年   203篇
  2006年   170篇
  2005年   168篇
  2004年   148篇
  2003年   154篇
  2002年   174篇
  2001年   128篇
  2000年   153篇
  1999年   154篇
  1998年   101篇
  1997年   82篇
  1996年   89篇
  1995年   84篇
  1994年   61篇
  1993年   61篇
  1992年   114篇
  1991年   113篇
  1990年   94篇
  1989年   103篇
  1988年   100篇
  1987年   110篇
  1986年   102篇
  1985年   104篇
  1984年   51篇
  1983年   48篇
  1982年   37篇
  1981年   37篇
  1980年   35篇
  1979年   64篇
  1978年   38篇
  1977年   32篇
  1976年   41篇
  1975年   28篇
  1974年   42篇
  1973年   36篇
  1967年   29篇
排序方式: 共有4933条查询结果,搜索用时 31 毫秒
101.
AIMS: To define outcome measures for auditing the clinical care of children and adolescents with insulin dependent diabetes mellitus (IDDM) and to assess the benefit of appointing a dedicated paediatric trained diabetes specialist nurse (PDSN). METHODS: Retrospective analysis of medical notes and hospital records. Glycaemic control, growth, weight gain, microvascular complications, school absence, and the proportion of children undergoing an annual clinical review and diabetes education session were assessed. The effect of the appointment of a PDSN on the frequency of hospital admission, length of inpatient stay, and outpatient attendance was evaluated. RESULTS: Children with IDDM were of normal height and grew well for three years after diagnosis, but grew suboptimally thereafter. Weight gain was above average every year after diagnosis. Glycaemic control was poor at all ages with only 16% of children having an acceptable glycated haemoglobin. Eighty five per cent of patients underwent a formal annual clinical review, of whom 16% had background retinopathy and 20% microalbuminuria in one or more samples. After appointing the PDSN the median length of hospital stay for newly diagnosed patients decreased from five days to one day, with 10 of 24 children not admitted. None of the latter was admitted during the next year. There was no evidence of the PDSN affecting the frequency of readmission or length of stay of children with established IDDM. Non-attendance at the outpatient clinic was reduced from a median of 19 to 10%. CONCLUSIONS: Outcome measures for evaluating the care of children with IDDM can be defined and evaluated. Specialist nursing support markedly reduces the length of hospital stay of newly diagnosed patients without sacrificing the quality of care.  相似文献   
102.
OBJECTIVES: The amount of adipose tissue influences pubertal development and fertility in girls. A candidate for mediating this is the hormone leptin, derived from adipocytes. This work was carried out to determine whether the leptin concentration in serum is regulated during pubertal development. SUBJECTS AND METHODS: Serum concentrations of leptin were determined by radioimmunoassay in a sample of 252 healthy children representing all pubertal stages. RESULTS: Serum leptin concentrations correlated directly with age (r = 0.53), body mass index (BMI) (r = 0.71), and weight for height SD score (r = 0.44) in girls and with BMI (r = 0.33) and weight for height SD score in boys (r = 0.36). Leptin concentrations increased with pubertal development in girls, resulting in significantly higher concentrations at pubertal stages 4 and 5 than at the prepubertal stage, whereas there was no change in the boys. CONCLUSIONS: Serum leptin concentrations increased during pubertal development in the girls, but remained constant in the boys. Whether the increase in serum leptin concentrations in girls is of importance for, or a consequence of, pubertal development is still to be determined.  相似文献   
103.
104.
Diwan  BA; Anderson  LM; Ward  JM 《Carcinogenesis》1997,18(10):2009-2014
Tamoxifen (TAM) is widely used as adjuvant breast cancer therapy after surgery and as a chemopreventive agent in women of child-bearing age. However, TAM therapy has been shown to result in an increased incidence of endometrial carcinoma in women. The present study was designed to investigate the effects of TAM (5 mg/kg and 7.5 mg/kg body wt) given i.g. to pregnant CD-1 mice (1x/day, days 12 through 18 of gestation) on their female offspring. Progressive proliferative hyperplasia of the oviduct was frequently seen in TAM-exposed offspring, reaching 100% incidence by 52 weeks in both treatment groups. These females also developed progressive proliferative uterine lesions, including moderate/severe cystic endometrial hyperplasia (34-50%) and polypoid adenomas (27-30%) between 53 and 78 weeks. Deciduomas (15%) occurred at young ages (12 and 24 weeks) while leiomyomas (14%), a malignant leiomyosarcoma, and ovarian granulosa cell tumors (14%), were found between 72 and 78 weeks. Our findings thus suggest a strong association between transplacental TAM and reproductive tract abnormalities in female CD-1 mice.   相似文献   
105.
OBJECTIVE: The ketogenic diet is a high-fat, low-protein, low-carbohydrate diet developed in the 1920s for the treatment of children with difficult to control seizures. Despite advances in both the pharmacotherapy and the surgery of epilepsy, many children continue to have difficult-to-control seizures. This prospective study sought to determine the ketogenic diet's effectiveness and tolerability in children refractory to today's medications. METHODS: One hundred fifty consecutive children, ages 1 to 16 years, virtually all of whom continued to have more than two seizures per week despite adequate therapy with at least two anticonvulsant medications, were prospectively enrolled in this study, treated with the ketogenic diet, and followed for a minimum of 1 year. Seizure frequency was tabulated from patients' daily seizure calendars and seizure reduction calculated as percentage of baseline frequency. Adverse events and reasons for diet discontinuation were recorded. RESULTS: The children (mean age, 5.3 years), averaged 410 seizures per month before the diet, despite an exposure to a mean of 6.2 antiepileptic medications. Three months after diet initiation, 83% of those starting remained on the diet and 34% had >90% decrease in seizures. At 6 months, 71% still remained on the diet and 32% had a >90% decrease in seizures. At 1 year, 55% remained on the diet and 27% had a >90% decrease in seizure frequency. Most of those discontinuing the diet did so because it was either insufficiently effective or too restrictive. Seven percent stopped because of intercurrent illness. CONCLUSIONS: The ketogenic diet should be considered as alternative therapy for children with difficult-to-control seizures. It is more effective than many of the new anticonvulsant medications and is well tolerated by children and families when it is effective.  相似文献   
106.
Two girls (a 5 year old and a 21 month old) experiencing mononucleosis syndrome with coincidental human herpesvirus (HHV)-7 and Epstein-Barr virus (EBV) infections are described. One patient had primary HHV-7 infection and reactivated EBV infection. The other had primary HHV-7 and EBV infections. These cases indicated that HHV-7 is capable of inducing infectious mononucleosis-like illness. Multiple herpesvirus infection in one of the patients also suggests that interaction among herpesviruses can occur in vivo. The consequence of this interaction may have clinical implications.  相似文献   
107.
Between November 1993 and May 1996, 51 patients with a hypopharyngeal diverticulum were treated by endoscopic stapled diverticulotomy. Normal swallowing was resumed within 36 h of surgery in 73%, and in 93% by 72 h. Two patients required nasogastric feeding for 5–7 days. There were no operative deaths or serious operative morbidity, and there have been no recorded cases of clinical recurrence of pouches to date (maximum follow-up 562 days: 46 cases over 12 months). The low morbidity, short hospital stay and early return to normal feeding, combined with a relative absence of complications or pouch recurrence, make endoscopic stapled diverticulotomy the treatment of choice for the majority of patients.  相似文献   
108.
A survey of the contribution to external dose from gamma rays originating from intertidal sediments in the vicinity of the British Nuclear Group Sellafield site showed that the major anthropogenic contributions were due to (137)Cs and (60)Co. At some sites, traces of other anthropogenic radionuclides were detected, namely (106)Ru, (125)Sb, and (154)Eu. The proportions of fine grained material (<63 microm) were used to improve model predictions of dose contribution due to external exposure to gamma rays, using the CUMBRIA77/DOSE77 model. Model dose predictions were compared to those directly measured in the field. Using the new proportions of fine grained material (1-17.5%) in conjunction with field gamma-ray spectra, model predictions were improved considerably for most sites. Exceptions were at Drigg Barn Scar and Whitehaven Coal Sands sites, which had their own unique characteristics. The highest (60)Co activity concentrations in this study were detected at Drigg Barn Scar. These relatively high activity concentrations of (60)Co were due to the presence of (60)Co in mussels and barnacles, hence upsetting the fine sediment relationships used in previous dose calculations. Whitehaven Coal Sands was unusual in that it contained higher levels of radionuclides than would be expected in sandy sediment. The mineralogy of these sediments was the controlling factor on (137)Cs binding, rather than the proportion of fine grained material. By adjusting the effective fine grained sediment proportions for calculations involving (60)Co and (137)Cs at Drigg Barn Scar and Whitehaven Coal Sands respectively, the CUMBRIA77/DOSE77 model predictions could be improved upon significantly for these sites. This work highlights the influence of particle size and sediment composition on external dose rate calculations, as well as the potential for external dose contributions from biota.  相似文献   
109.
The purpose of this study was to develop and evaluate an F-18 labeled choline tumor imaging agent.FCH was synthesized through the intermediate F-18 fluorobromomethane that was used to alkylate dimethylethanolamine. The isolated FCH was evaluated in PC-3 human prostate cancer cells, PC-3 human prostate cancer xenograft studies, and human prostate and brain tumor patients.FCH was accumulated at a slightly lower rate than FDG in the cultures of PC-3 cells. Inhibition of choline transport and phosphorylation by hemicholinium-3 resulted in a 90% decrease in FCH uptake without altering FDG uptake. FCH had a similar biodistribution as C-14 choline in mice, with the liver and kidneys being the primary sites of uptake. Tumor uptake of FCH and FDG were comparable at 45-60 mins after injections. The tumor:blood ratio was higher for FCH (5.3 +/- 2.4) than for FDG (3.2 +/- 0.3). Brain uptake of FCH was 10% that of FDG. FCH-PET studies were compared to FDG-PET studies. In the prostate cancer patients, more lesions have been seen on the FCH studies than on the FDG studies, and the standardized uptake values (SUV) have been higher with the FCH. Decreases in FCH-PET SUV have been noted in patients treated by androgen deprivation. Patients with suspected recurrent brain tumors have had more clearly defined abnormal accumulation on the FCH-PET scans than on the FDG-PET scans. The FCH is not accumulated by normal cortex.FCH is a promising imaging agent for the evaluation of metastatic prostate cancer and recurrent brain tumor.  相似文献   
110.
CONTEXT: Acute myocardial infarction (AMI) is a common and important cause of admission to US rural hospitals, as transport of patients with AMI to urban settings can result in unacceptable delays in care. PURPOSE: To examine the quality of care for patients with AMI in rural hospitals with differing degrees of remoteness from urban centers. METHODS: This cohort study used data from the Cooperative Cardiovascular Project (CCP), including 4,085 acute care hospitals (408 remote small rural, 893 small rural, 619 large rural, and 2,165 urban) with 135,759 direct admissions of Medicare beneficiaries ages 65 and older for a confirmed AMI between February 1994 and July 1995. Outcomes included use of aspirin, reperfusion, heparin, and intravenous nitroglycerin during hospitalization; use of beta-blockers, aspirin, and angiotensin-converting enzyme (ACE) inhibitors at discharge; avoidance of calcium channel blockers at discharge; and 30-day mortality. FINDINGS: Substantial proportions of Medicare beneficiaries in both urban and rural hospitals did not receive the recommended treatments for AMI. Medicare patients in rural hospitals were less likely than urban hospitals' patients to receive aspirin, intravenous nitroglycerin, heparin, and either thrombolytics or percutaneous transluminal coronary angioplasty. Only ACE inhibitors at discharge was used more for patients in rural hospitals than urban hospitals. Medicare patients in rural hospitals had higher adjusted 30-day post-AMI death rates from all causes than those in urban hospitals (odds ratio for large rural 1.14 [1.10 to 1.18], small rural 1.24 [1.20 to 1.29], remote small rural 1.32 [1.23 to 1.41]). CONCLUSIONS: Efforts are needed to help hospital medical staffs in both rural and urban areas develop systems to ensure that patients receive recommended treatments for AMI.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号