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   51821篇
  免费   3208篇
  国内免费   246篇
耳鼻咽喉   650篇
儿科学   1187篇
妇产科学   1232篇
基础医学   7182篇
口腔科学   1505篇
临床医学   5697篇
内科学   11130篇
皮肤病学   815篇
神经病学   5095篇
特种医学   1816篇
外科学   6581篇
综合类   334篇
一般理论   44篇
预防医学   3669篇
眼科学   842篇
药学   3510篇
  1篇
中国医学   60篇
肿瘤学   3925篇
  2023年   325篇
  2022年   636篇
  2021年   1157篇
  2020年   757篇
  2019年   993篇
  2018年   1219篇
  2017年   1079篇
  2016年   1267篇
  2015年   1326篇
  2014年   1760篇
  2013年   2532篇
  2012年   3844篇
  2011年   4045篇
  2010年   2393篇
  2009年   2187篇
  2008年   3351篇
  2007年   3640篇
  2006年   3255篇
  2005年   3323篇
  2004年   3051篇
  2003年   2847篇
  2002年   2600篇
  2001年   474篇
  2000年   404篇
  1999年   525篇
  1998年   579篇
  1997年   470篇
  1996年   421篇
  1995年   362篇
  1994年   313篇
  1993年   320篇
  1992年   265篇
  1991年   244篇
  1990年   222篇
  1989年   243篇
  1988年   216篇
  1987年   180篇
  1986年   188篇
  1985年   218篇
  1984年   189篇
  1983年   173篇
  1982年   193篇
  1981年   162篇
  1980年   139篇
  1979年   120篇
  1978年   126篇
  1977年   133篇
  1976年   98篇
  1975年   112篇
  1974年   89篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
In many cases of suspected child sexual abuse, there may be no diagnostic clinical findings that provide direct evidence of penetrating trauma. However, the missing evidence from genital findings does not exclude sexual abuse. The difficulties in interpreting clinical findings in infancy, e.g. the difference between genital injuries and normal anatomical changes in hymenal morphology, the hormonal influence on hymenal appearance and differentiation from accidental or disease related anogenital changes will be demonstrated by case reports and discussed. The cases described confirm the outstanding importance of forensic examinations and emphasize the responsibility and value of forensic medicine in the network involving the clinic and the investigating authorities.  相似文献   
102.
103.
 The objective of the present study was to determine the role of mast cells and histamine in leukocyte-endothelium interactions in mesenteric venules of four rat strains: Brown Norway, Lewis, Sprague-Dawley and Wistar. Intravital microscopy showed that the mast cell stabilizer cromoglycate (5 mg/kg i.v. just before exteriorization of the mesentery) did not affect the baseline level and velocity of leukocyte rolling in any of the four strains. This finding is in agreement with the observation that cromoglycate pretreatment only slightly influenced mast cell degranulation in all strains except the Brown Norway. After mast cell stabilization, only in Sprague-Dawley did topical administration of histamine (10–4 M) result in a significant increase in the level of leukocyte rolling and a decrease in the rolling velocity compared with the time control. Histamine induced leukocyte adhesion only in the Brown Norway strain. In conclusion, the hypothesis presented in other studies, that degranulation of mast cells, and more specifically the release of histamine, is of major importance for the induction of leukocyte-endothelium interactions in rat mesenteric venules is not generally applicable; the present study shows a clear strain dependency. Received: 18 July 1997 / Received after revision: 17 November 1997 / Accepted: 13 March 1998  相似文献   
104.
105.
The purpose of this study was to appraise the value of PET in the assessment of the effect of supposedly proangiogenic new therapies such as gene therapy with vascular endothelial growth factor (VEGF) gene and endomyocardial laser therapy. METHODS: Thirty-five patients with end-stage coronary artery disease and class III (Canadian Cardiovascular Society) angina were included. Myocardial ischemia was evaluated with dipyridamole PET scanning and exercise tolerance with bicycle ergometry. Ten patients were treated with naked plasmid DNA encoding for human VEGF165 (VEGF) and 12 patients were treated with laser therapy (direct myocardial revascularization [DMR]) using an electromechanical mapping system. Thirteen patients were treated with standard medical therapy (control). RESULTS: In both active treatment groups, angina was reduced in most subjects, except in 2 VEGF and 5 DMR patients. In the control group, no improvement in anginal classification was found, except in 3 subjects. On the PET scan, solely in the VEGF group, the stress perfusion was significantly improved (from 57 +/- 33 to 81 +/- 55 mL/min/100 g; P = 0.031). Furthermore, in the VEGF group, the number of ischemic segments was reduced from 274 +/- 41 to 234 +/- 48 segments (P = 0.004) but not in the DMR group (from 209 +/- 43 to 215 +/- 52 segments) or in the control group (from 218 +/- 18 to 213 +/- 28 segments). Bicycle exercise duration showed slight nonsignificant changes in the VEGF group (from 3.6 +/- 2.0 to 4.6 +/- 2.1 min), in the DMR group (from 5.1 +/- 1.5 to 4.7 +/- 1.3 min), and in the control group (from 3.3 +/- 1.8 to 3.5 +/- 2.3 min). CONCLUSION: PET showed that intramyocardial gene therapy with the human VEGF165 gene in contrast to laser DMR treatment effectively reduces myocardial ischemia.  相似文献   
106.
The capacity for short-term adaptation is a well-established property of the horizontal (H) and vertical (V) components of saccades. It allows these directional components, which clearly serve the goal of foveation, to maintain their precision even under changing circumstances. Torsional (T) saccade components, on the other hand, which deal with the orientation of the target on the fovea, have hardly been investigated in adaptation experiments. They appear to be severely restricted by Listing's law during fixations and saccades. The main purpose of Listing's law is far from obvious but could be visual or oculomotor. Better knowledge of the adaptive capacity of the saccadic system in the torsional direction could throw new light on the functional significance of this interesting neural strategy. To study short-term plasticity in the torsional components of saccades, binocular 3D-eye positions were measured, using magnetic search foils. Five normal human subjects were instructed to make uni-directional refixation saccades, while they viewed a large visual scene. To induce a change in the torsional component, the complete stimulus was rapidly rotated during these saccades. We thoroughly investigated the torsional responses of the saccadic system, to see if any short-term adaptive response in torsional direction was induced, in which case the notion of a visual purpose for Listing's law would be strengthened. In none of our experiments, however, did we find any clear adaptive response in torsional direction. To further investigate the reliability of this result and to ascertain that our experimental conditions allowed classical gain adaptation, we also did experiments designed to achieve a combination of torsional adaptation and classic gain shortening in one of the directional components. While gain adaptation was very obvious, none of the experiments provided evidence for a short-term effect in torsion. We conclude that our experiments do not support a purely visual basis for Listing's law.  相似文献   
107.
We have investigated Ca2+ mobilization in single T cells stimulated with their physiological ligand, i.e. antigenic peptide bound to major histocompatibility complex (MHC) molecules on antigen-presenting cells (APC). Fibroblasts expressing I-Ed class II molecules were pulsed with a peptide derived from the λ2315 immunoglobulin light chain. Onto such antigen-pulsed fibroblasts were sedimented cloned Th1 cells loaded with Fura-2. Changes in cytosolic Ca2+ concentration in single T cells were continually monitored by use of an imaging system based on fluorometry. Ca2+ mobilization was both peptide-specific and MHC-restricted. Within seconds of the initial APC-T cell contact, a Ca2+ spike could be observed. The Ca2+ response gradually declined over a 25-min period, during which oscillations were noted. Various parameters characterizing the magnitude of the Ca2+ response (latency, increase rate, max and mean Ca2+ increase, frequency and period of oscillations) all correlated with the amount of peptide used for pulsing the fibroblasts. Thus, Ca2+ mobilization in single T cells appears not to be an all or none phenomenon. Rather, activation is incremental (analog signaling), the degree of Ca2+ mobilization probably being related to the number of stimulatory peptide-MHC complexes on the surface of the APC. The extent of calcium mobilization and lymphokine production (interleukin (IL)-2, IL-3, interferon-γ) correlated, at least at the population level.  相似文献   
108.
Effective haemostasis during cardiac surgery   总被引:2,自引:0,他引:2  
  相似文献   
109.
110.
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