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   4549篇
  免费   427篇
  国内免费   25篇
耳鼻咽喉   42篇
儿科学   239篇
妇产科学   107篇
基础医学   560篇
口腔科学   134篇
临床医学   479篇
内科学   1152篇
皮肤病学   78篇
神经病学   293篇
特种医学   573篇
外科学   464篇
综合类   119篇
一般理论   1篇
预防医学   270篇
眼科学   42篇
药学   227篇
中国医学   3篇
肿瘤学   218篇
  2022年   18篇
  2021年   39篇
  2020年   44篇
  2019年   51篇
  2018年   66篇
  2017年   56篇
  2016年   70篇
  2015年   66篇
  2014年   88篇
  2013年   154篇
  2012年   166篇
  2011年   172篇
  2010年   195篇
  2009年   158篇
  2008年   158篇
  2007年   186篇
  2006年   192篇
  2005年   162篇
  2004年   157篇
  2003年   130篇
  2002年   109篇
  2001年   100篇
  2000年   121篇
  1999年   127篇
  1998年   183篇
  1997年   154篇
  1996年   161篇
  1995年   135篇
  1994年   110篇
  1993年   123篇
  1992年   107篇
  1991年   80篇
  1990年   75篇
  1989年   112篇
  1988年   92篇
  1987年   111篇
  1986年   80篇
  1985年   86篇
  1984年   66篇
  1983年   59篇
  1982年   49篇
  1981年   41篇
  1980年   54篇
  1979年   37篇
  1978年   43篇
  1977年   40篇
  1976年   38篇
  1975年   41篇
  1973年   16篇
  1971年   19篇
排序方式: 共有5001条查询结果,搜索用时 15 毫秒
61.
62.
63.
Expression of the human T cell receptor V beta repertoire.   总被引:5,自引:0,他引:5  
We have used a sensitive assay, based on amplification of cDNA by the polymerase chain reaction, to determine in a variety of human tissues the relative levels of expression of the genes coding for each of the twenty families of human TcR V beta. We have determined the diversity of the expressed TcR V beta repertoire early in the development of the immune system. We have shown that the full TcR V beta repertoire is expressed early into the second trimester; the expressed repertoire is as diverse at this point, in both fetal thymus and spleen, as it is in mature thymus and peripheral blood lymphocytes. In addition the relative expression in the fetal thymus of each V beta gene is conserved to a large extent in the fetal spleen.  相似文献   
64.
65.
In 16 guinea pigs the pulmonary circulation was isolated from the pulmonary systemic circulation and perfused with Tris buffer or with Tris buffer containing cromolyn sodium. The lungs were first ventilated with 100% O2 and then 100% N2 to induce alveolar hypoxia. The effluent was collected from the aorta and assayed for histamine by the fluorometric method. In all seven animals perfused with Tris alone (no cromolyn) a marked elevation of the effluent histamine was demonstrated. In the group perfused with buffer containing cromolyn there was a substantial diminution in the response to hypoxia. Therefore, cromolyn sodium partially blocked hypoxia-mediated histamine release.  相似文献   
66.
Increased antiphospholipid antibody prevalence has been demonstrated by a number of recent studies in in-vitro fertilization (IVF) patients but the potential effects of antiphospholipid antibodies on the different components of the reproductive process and the consideration of whether to test IVF patients for antiphospholipid antibodies are controversial. The present study was undertaken to investigate the possible association between the presence of circulating antiphospholipid antibodies (namely the lupus anticoagulant and anticardiolipin antibodies), among a series of 21 consecutive IVF patients having a clinical spontaneous abortion after their first embryo transfer. As a control group (n=42), the nearest IVF cycle resulting in an ongoing pregnancy before and after each miscarried IVF cycle (i.e. the closest cycles in temporal relationship to the index cycle) was used. One patient (4.8%) in the study group and two women (4.8%) among controls were seropositive for antiphospholipid antibodies. These low and similar seropositivity rates found in the two groups studied lead us to conclude that antiphospholipid antibodies testing in IVF patients should be considered only in those women having repeated failures of implantation/clinical abortion after embryo transfer but not in an infertile general population reaching an IVF programme.   相似文献   
67.
The objective was to demonstrate bioequivalence between s.c. and i.m. administration of Humegon (FSH/LH ratio 1:1) and Normegon (FSH/LH ratio 3:1). In two randomized, single-centre, cross-over studies, 18 healthy volunteers on each formulation were assigned to one of the two administration sequences. Subjects were given single doses of one of the above gonadotrophins after endogenous gonadotrophin production had first been suppressed using high-dose oral contraceptive. Subsequently, rate (Cmax, tmax) and extent (AUC) of absorption of follicle stimulating hormone (FSH) and luteinizing hormone (LH) were determined for 14 days. For Cmax and AUC, analysis of variance (ANOVA) was performed on log-transformed data and for tmax ANOVA was performed on ranks. Intramuscular and s.c. injections of Humegon were bioequivalent with respect to the main pharmacokinetic parameters, being AUC and Cmax of FSH absorption. Intramuscular and s.c. injections of Normegon were bioequivalent with respect to the AUC of FSH and not bioequivalent with respect to the Cmax of FSH. For tmax of FSH as well as for most LH variables of both preparations, bioequivalence could not be proven due to the high intra- and interindividual variability and/or concentrations being close to the detection limit. Thus, the main pharmacokinetic FSH variables after i.m. and s.c. administration of Humegon and Normegon were bioequivalent.   相似文献   
68.
A pilot study was designed to examine whether the outcome of embryo transfer in women with a hydrosalpinx might be improved by surgical drainage of the hydrosalpinx at the time of oocyte collection for in- vitro fertilization treatment. A comparative, controlled but retrospective analysis of the results was performed of all women with infective tubal damage aged <40 years old, who had ovulatory cycles, a normal uterus and a partner with normal spermatozoa. A standardized treatment regimen was used. A maximum of three embryos were transferred. Hydrosalpinx was defined by prior hysterosalpingography and/or laparoscopy with transcervical dye injection. A total of 237 embryo transfer cycles in women with hydrosalpinges (tubal distension not visible in 151, visible but not drained in 30 and drained in 56) were compared with 705 embryo transfer cycles in women with tubal disease but no hydrosalpinx. Results were analysed in the first three cycles but also separately in the first cycle to check for bias. Success rates were higher in the first cycle, but did not significantly influence overall differences. Implantation rates were significantly reduced overall in the hydrosalpinx group (8.0 versus 13.2% for controls; P < 0.001), being 8.3% (P < 0.01) in the subgroup without evident tubal distension and 7.5% (not significant) in the drained hydrosalpinx group. This study shows that tubal damage with distal occlusion is associated with a marked reduction in embryo implantation, even in the absence of obvious fluid distension. Surgical drainage of distended hydrosalpinges appears to offer no benefit.   相似文献   
69.
70.
The aims of this work were to measure the accuracy of one continuous speech recognition product and dependence on the speaker's gender and status as a native or nonnative English speaker, and evaluate the product's potential for routine use in transcribing radiology reports. IBM MedSpeak/Radiology software, version 1.1 was evaluated by 6 speakers. Two were nonnative English speakers, and 3 were men. Each speaker dictated a set of 12 reports. The reports included neurologic and body imaging examinations performed with 6 different modalities. The dictated and original report texts were compared, and error rates for overall, significant, and subtle significant errors were computed. Error rate dependence on modality, native English speaker status, and gender were evaluated by performing ttests. The overall error rate was 10.3 +/- 3.3%. No difference in accuracy between men and women was found; however, significant differences were seen for overall and significant errors when comparing native and nonnative English speakers (P = .009 and P = .008, respectively). The speech recognition software is approximately 90% accurate, and while practical implementation issues (rather than accuracy) currently limit routine use of this product throughout a radiology practice, application in niche areas such as the emergency room currently is being pursued. This methodology provides a convenient way to compare the initial accuracy of different speech recognition products, and changes in accuracy over time, in a detailed and sensitive manner.  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