全文获取类型
收费全文 | 21346篇 |
免费 | 1692篇 |
国内免费 | 90篇 |
专业分类
耳鼻咽喉 | 251篇 |
儿科学 | 660篇 |
妇产科学 | 348篇 |
基础医学 | 2852篇 |
口腔科学 | 286篇 |
临床医学 | 2291篇 |
内科学 | 5265篇 |
皮肤病学 | 276篇 |
神经病学 | 1727篇 |
特种医学 | 786篇 |
外国民族医学 | 10篇 |
外科学 | 3144篇 |
综合类 | 283篇 |
一般理论 | 10篇 |
预防医学 | 1548篇 |
眼科学 | 666篇 |
药学 | 1258篇 |
中国医学 | 51篇 |
肿瘤学 | 1416篇 |
出版年
2023年 | 102篇 |
2022年 | 151篇 |
2021年 | 322篇 |
2020年 | 205篇 |
2019年 | 399篇 |
2018年 | 439篇 |
2017年 | 344篇 |
2016年 | 359篇 |
2015年 | 393篇 |
2014年 | 586篇 |
2013年 | 852篇 |
2012年 | 1228篇 |
2011年 | 1172篇 |
2010年 | 741篇 |
2009年 | 722篇 |
2008年 | 1207篇 |
2007年 | 1299篇 |
2006年 | 1298篇 |
2005年 | 1216篇 |
2004年 | 1181篇 |
2003年 | 1134篇 |
2002年 | 1045篇 |
2001年 | 405篇 |
2000年 | 382篇 |
1999年 | 355篇 |
1998年 | 241篇 |
1997年 | 214篇 |
1996年 | 170篇 |
1995年 | 215篇 |
1994年 | 177篇 |
1993年 | 145篇 |
1992年 | 273篇 |
1991年 | 236篇 |
1990年 | 249篇 |
1989年 | 234篇 |
1988年 | 243篇 |
1987年 | 204篇 |
1986年 | 202篇 |
1985年 | 181篇 |
1984年 | 184篇 |
1983年 | 192篇 |
1982年 | 172篇 |
1981年 | 140篇 |
1980年 | 130篇 |
1979年 | 136篇 |
1978年 | 128篇 |
1977年 | 134篇 |
1976年 | 101篇 |
1975年 | 87篇 |
1974年 | 93篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
R. M. Niven A. M. Fletcher C. A. Pickering D. Fishwick C. J. Warburton J. C. Simpson H. Francis L. A. Oldham 《Thorax》1997,52(1):22-27
BACKGROUND: Exposure to cotton is known to produce a specific occupational disease known as byssinosis. A large population of textile workers was investigated to determine whether such exposure was also associated with chronic bronchitis once other possible aetiological factors had been accounted for. METHODS: A total of 2991 workers were investigated for the presence of symptoms compatible with chronic bronchitis. An MRC adapted respiratory questionnaire and MRC definition of chronic bronchitis were used for diagnostic labelling. Current and lifetime exposure to dust was estimated by personal and work area sampling, and the use of records of retrospective dust levels previously measured over the preceding 10 years. Airborne endotoxin exposure was measured using a quantitative turbidometric assay. Lung function tests were performed to measure forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). A control group of workers exposed to man-made fibre textiles was identified. The comparative prevalence of chronic bronchitis in the two populations was assessed, allowing for sex, age, smoking habit, and ethnic origin. Two case referent studies were also performed; cases of chronic bronchitis were separately matched with controls from the cotton and control populations to determine the effect of the symptomatic state on lung function. RESULTS: After controlling for smoking (pack years), workers in a cotton environment were significantly more likely to suffer from chronic bronchitis and this was most marked in workers over 45 years of age (odds ratio 2.51 (CI 1.3 to 4.9); p < 0.01). Regression analysis of all possible influencing parameters showed that cumulative exposure to cotton dust was significantly associated with chronic bronchitis after the effects of age, sex, smoking, and ethnic group were accounted for (p < 0.0005). In the intra-cotton population case control study a diagnosis of chronic bronchitis was associated with a small decrement in lung function compared with controls: percentage predicted FEV1 in cases 81.4% (95% CI 78.3 to 84.6), controls 86.7% (84.9 to 88.5); FVC in cases 89.9% (95% CI 87.0 to 92.9), controls 94.6% (92.8 to 96.4). After controlling for cumulative past exposure and pack years of smoking the effect of the diagnostic state remained significant for both FEV1 (p < 0.01) and FVC (p < 0.05). CONCLUSIONS: Chronic bronchitis is more prevalent in cotton workers than in those working with man-made fibre and exposure is additive to the effect of smoking. The diagnosis of chronic bronchitis is associated with a small but significant decrement in lung function.
相似文献
相似文献
52.
T Abu-Nema K Ayyash L Berntman Y Matani G H Sigurdsson I Francis C Hellekant 《Circulatory shock》1988,24(1):55-62
Two groups (n = 10 in each) of adult sheep were exposed to hemorrhagic shock resulting in mean arterial pressure (MAP) below 25 mmHg for 10 min. Following that, group A received crystalloids (8% of body wt) during one hr together with supraceliac intraaortic balloon tamponade during the first 30 min, while group B (controls) received crystalloids only. The central circulation was rapidly restored in group A, as indicated by increased MAP and increased systemic vascular resistance (SVR). After deflation of the balloon MAP dropped to the same value as in the control group, while cardiac index increased gradually with volume replacement and was significantly higher at the end of the resuscitation period (60 min) than in the control group (P less than 0.05). Despite a more rapid restoration of central hemodynamics in group A, lactic acidosis was more severe, acute renal failure and neurological complications more frequent, and mortality higher than in the control group. It was concluded that continuous supraceliac aortic occlusion for 30 min had deleterious effects on organs dependent on aortic blood flow distal to the aortic tamponade and may contribute to the development of multiple organ failure after resuscitation from hemorrhagic shock. Further studies are needed to evaluate the effects of intermittent intraaortic balloon tamponade in hemorrhagic shock. 相似文献
53.
D Macfoy J Hewitt E Barker W A Francis 《European journal of obstetrics, gynecology, and reproductive biology》1992,43(1):35-37
Over a 13-month period in a newly opened assisted conception unit at the Women's Hospital, Liverpool, gamete intra-fallopian transfer using donor semen, GIFT (D) was offered to eighteen couples who had failed to conceive after numerous cycles of treatment with artificial insemination by donor semen (AID). The indication for the use of donor semen was either azo- or severe oligoaesthenospermia, and, in addition, the female partners have been exhaustively investigated with no major cause found to account for the couple's infertility. Using a basic clomiphene citrate and human menopausal gonadotrophin protocol it was possible to achieve a pregnancy rate of 56% per GIFT (D) cycle. As a consequence of these results it is now our policy to treat couples whose infertility is due to an unresolvable male factor with AID for 12 cycles only. If they have been unsuccessful in achieving a pregnancy after this time, they are offered GIFT (D). 相似文献
54.
Magnetic resonance imaging of the adrenal glands was performed in 9 patients with Addison’s disease to evaluate the role of magnetic resonance (MR) in this entity. All patients had bilateral adrenal masses demonstrated by computed tomography (CT); etiologies included adrenal hemorrhage (2 patients), granulomatous disease (1 patient), adrenal lymphoma (3 patients), and adrenal metastases (3 patients). Spin-echo axial images were obtained at repetition times (TR) 0.5, 2.0 s and TE 28, 56 ms, using a Diasonics superconducting magnet operating at 0.35 T. In the patients with lymphoma, metastases, and granulomatous disease, the adrenal masses appeared hypointense or isointense with liver on the T1-weighted images (TR 0.5 s, TE 28 ms). In cases of adrenal hemorrhage, areas of hyperintensity were seen on TR 0.5, TE 56 ms sequences, due to shortening of T1 values. In both groups of patients the masses were hyperintense on T2 weighted sequences. Mean calculated T1 of the hemorrhagic glands was 449 ms, compared with a mean of 782 ms for mestastases and lymphoma. While MR is not capable of distinguishing between acute inflammatory and metastatic disases of the adrenal glands, it may be equally efficacious as CT in suggesting the diagnosis of adrenal hemorrhage in patients with Addison’s disease. 相似文献
55.
56.
The well established differential pulmonary handling of angiotensins I and II indicates the possibility that vascular receptors for the deca- and octa-peptides do not necessarily involve common sites in the renal vasculature either. Experimental findings involving haemodynamic changes within the kidney in anaesthetised and conscious sheep, with utilization of the angiotensins, and also of noradrenaline, are briefly presented; the implications of the intra-renal water and creatinine transfers are discussed, especially as they concern the possible location of angiotensin receptors in the renal blood vessels. Other aspects of the relationships between the peptides are also taken into account particularly with regard to a postulated angiotensin I [NaCl] dependent peritubular capillary antidiuretic action, angiotensin converting enzyme inhibition, Goldblatt clamp induced hypertension and blood flow through the hind-limbs. 相似文献
57.
One case of schwannoma of the stomach diagnosed with ultrasound-guided biopsy puncture is reported. This diagnosis is usually not established with radiographic and endoscopic examinations. A preoperative diagnosis allows partly predicting the type of exeresis to be performed. On the other hand, guided biopsy puncture seldom allows establishing a prognosis, for which the criteria are based on the analysis of the whole tumor and the possible discovery of synchronous or metachronous metastases. 相似文献
58.
S Schlumberger A Ceddaha A Brusset L Raffin C Dubois D Guilmet M Fischler 《Annales fran?aises d'anesthèsie et de rèanimation》1992,11(4):405-409
The haemodynamic effects and the side-effects of anaesthesia using high doses of fentanyl were compared in two groups of 12 patients each. All the patients had poor left ventricular function and were scheduled for elective coronary artery bypass graft surgery or valvular replacement. Patients were randomly assigned to either group. In group EF, patients were given 5 micrograms.kg-1 of fentanyl, followed by 0.3 mg.kg-1 of etomidate. Once they had lost consciousness, they were given 15 mg of pancuronium and 25 micrograms.kg-1 of fentanyl over a 5 min period. Patients in group F received the full 30 micrograms.kg-1 dose of fentanyl over a 5 min period, followed by 15 mg of pancuronium. The patients were intubated 2 min after the end of the fentanyl infusion. They were mechanically ventilated with 100% oxygen. Anaesthesia was maintained with a continuous infusion of fentanyl (total dose 100 micrograms.kg-1). The usual haemodynamic parameters were monitored and calculated, as well as pain during injection of the drugs, myoclonia, chest wall rigidity and the time to loss of consciousness. The two groups were comparable with respect to age, weight, height and surgery. One third of the patients in group EF complained of pain during etomidate injection. The time required to loose consciousness was shorter in group EF (55 +/- 16 sec) than in group F (177 +/- 56 sec) (p < 0.001). The cardiac index decrease in group EF (2.0 +/- 0.4 l.min-1.m-2 vs. 1.9 +/- 0.4 l.min-1.m-2) (p < 0.05), respectively between the time just before tracheal intubation (T1), and 10 min after tracheal intubation (T3).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
59.
Shirley Kobar Coni C Francis Samantha MaWhinney Teresa Sharp 《Nutrition in clinical practice》2003,18(5):417-421
BACKGROUND: Development of an acclimation protocol for use when measuring resting energy expenditure (REE) would simplify and standardize data collection. The purpose of this study was to determine if our 2 metabolic carts could be used interchangeably and to determine if excluding the first 3 or 5 minutes of data collected as an acclimation period would significantly improve the coefficients of variation (CVs) for oxygen consumed (VO(2)) and carbon dioxide produced (VCO(2)) when performing REE assessments with our metabolic cart systems. METHODS: Thirteen healthy, nonsmoking adults ranging in age from 32 to 45 years, with activity levels ranging from sedentary to highly active, participated. Indirect calorimetry was performed twice in the morning after 30 minutes of supine resting. Subjects had fasted for 12 hours, and did not exercise within the last 24 hours. The system order for testing was randomized for the first measurement. When the first measurement was completed, subjects were crossed over for measurement using a second metabolic cart. RESULTS: The CVs for VO(2) and VCO(2) were significantly lower when excluding the first 3 (VO(2), p = .0005), (VCO(2), p = .0024) or 5 minutes (VO(2), p = .0001, VCO(2), p = .0021) of data compared with no exclusions. No significant differences in CVs between the 3- and 5-minute exclusions were found for VO(2) (p = .3224) or VCO(2) (p = .2255). CONCLUSIONS: Clearly, our machines cannot be used interchangeably within a study. An acclimation period improves CVs of VO(2) and VCO(2.) The similarities in CVs led us to adopt a 3-minute acclimation period for measuring REE. 相似文献
60.
A device called the Dex Frame has recently been marketed as an aid for children with specific learning difficulties. Using a test of reading speed and a test of reading accuracy we have attempted to evaluate the device. Two groups of children with learning difficulties were used, one having sole use of the device and being allowed to carry it with them and a second group who only used the device when attending for remedial tuition and assessment. The results show that no significant improvement occurred in reading performance of the groups with learning difficulties using the Dex Frame as compared with a control group. The teachers of the groups did, however, feel that on an individual basis some children (< 10%) expressed that they felt more comfortable using the device. 相似文献