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   4560篇
  免费   406篇
  国内免费   17篇
耳鼻咽喉   82篇
儿科学   145篇
妇产科学   84篇
基础医学   574篇
口腔科学   75篇
临床医学   606篇
内科学   858篇
皮肤病学   158篇
神经病学   355篇
特种医学   359篇
外科学   557篇
综合类   83篇
一般理论   4篇
预防医学   430篇
眼科学   59篇
药学   290篇
中国医学   16篇
肿瘤学   248篇
  2023年   25篇
  2021年   66篇
  2020年   35篇
  2019年   55篇
  2018年   86篇
  2017年   63篇
  2016年   65篇
  2015年   81篇
  2014年   103篇
  2013年   157篇
  2012年   203篇
  2011年   206篇
  2010年   154篇
  2009年   167篇
  2008年   181篇
  2007年   164篇
  2006年   175篇
  2005年   165篇
  2004年   159篇
  2003年   136篇
  2002年   140篇
  2001年   121篇
  2000年   107篇
  1999年   110篇
  1998年   89篇
  1997年   90篇
  1996年   99篇
  1995年   75篇
  1994年   68篇
  1993年   78篇
  1992年   100篇
  1991年   73篇
  1990年   117篇
  1989年   123篇
  1988年   111篇
  1987年   104篇
  1986年   108篇
  1985年   96篇
  1984年   77篇
  1983年   47篇
  1982年   51篇
  1981年   40篇
  1979年   41篇
  1978年   29篇
  1977年   41篇
  1976年   41篇
  1975年   38篇
  1973年   32篇
  1971年   28篇
  1970年   29篇
排序方式: 共有4983条查询结果,搜索用时 16 毫秒
61.
We have recently shown using dansyl-L-lysine exclusion studies that the release of human chorionic gonadotrophin (HCG) in conjunction with L- lactate dehydrogenase (LDH) from first trimester villi during organ culture is symptomatic of syncytiotrophoblast degeneration. The purpose of this study was to examine chorionic villi at the ultrastructural level in order to determine events occurring during organ culture. The tissue was sampled after 0, 24, 48 and 120 h in culture and processed for electron microscopy. In addition to confirming the previously recorded syncytial degeneration, the electron micrographs showed clearly the generation of a new syncytiotrophoblast layer. The new layer, derived from differentiating cytotrophoblast cells, was largely formed by 48 h and was maintained for at least 120 h in culture. This study demonstrates a model which provides an opportunity to study the differentiation of cytotrophoblast cells whilst they retain their anatomical relationships within the villous structure.   相似文献   
62.
In a double-blind trial comparing two thrombolytic agents as treatment for acute myocardial infarction, we randomized 270 consecutive patients an average (+/- SD) of 2.5 +/- 0.6 hours after the onset of chest pain from a first myocardial infarction--135 to receive intravenous streptokinase (1.5 million units over 30 minutes) and 135 to receive intravenous recombinant tissue plasminogen activator (rt-PA) (100 mg over three hours). The primary end point was left ventricular function as assessed by cineangiography performed three weeks after infarction. The effects of the two agents on left ventricular function were similar. The ejection fraction was identical (58 +/- 12 percent) in both groups. The end-systolic volume was 61 +/- 29 ml in the streptokinase group and 66 +/- 31 ml in the rt-PA group (P not significant). Patency rates at three weeks for the infarct-related artery were also similar (75 percent in the streptokinase group and 76 percent in the rt-PA group). Reinfarction rates at 30 days were the same (5 percent) in both groups. One patient had a fatal intracerebral hemorrhage 13 hours after receiving rt-PA, and another had a fatal cerebellar hemorrhage 21 hours after receiving rt-PA for reinfarction nine days after treatment with streptokinase. An intention-to-treat analysis revealed that mortality at 30 days was 3.7 percent in the rt-PA group as compared with 7.4 percent in the streptokinase group (P greater than 0.2). Follow-up for a mean of 9.0 months revealed no significant difference in survival; we observed 12 deaths (8.9 percent) in the streptokinase group and 8 deaths (5.9 percent) in the rt-PA group (P = 0.34). We conclude that rt-PA and streptokinase, in the doses given, have similar effects on left ventricular function after a first myocardial infarction. Because of the small number of deaths, it is not possible to determine whether their effects on mortality are similar.  相似文献   
63.
64.
HotSpots     
  相似文献   
65.

Background  

The purpose of the present investigation was to determine if the salivary counts of 40 common oral bacteria in subjects with an oral squamous cell carcinoma (OSCC) lesion would differ from those found in cancer-free (OSCC-free) controls.  相似文献   
66.
In each of 10 mongrel dogs anesthetized with alpha chloralose, strain-gauge arches were sutured to five epicardial and three endocardial locations. Comparisons of contractile force responses during stimulation of the left and right roots of the same segmental level revealed several differences dependent upon the particular myocardial area observed. Of the three left ventricular endocardial areas studied, the interventricular septum was the most responsive, particularly during stimulation of the right roots. The basal free wall and posterior papillary muscle were more responsive to left-root than to right-root stimulations. Epicardial responses were consistent with those previously reported. Generally, all areas responded to the greatest degree during stimulation of the second roots with the third and first next in order of effectiveness. Although stimulation of each level of preganglionic outflow activated all epicardial and endocardial segments of the myocardium, the magnitude of the changes in contractile force were highly variable dependent upon the specific level of preganglionic outflow and the location of the strain-gauge arch.  相似文献   
67.
68.
Widespread interest in global health issues is a common characteristic of students and faculty in schools of public health and schools of medicine. Building on strong university-based and community-based programs in global health, the University of Washington has created a unique Department of Global Health that is housed jointly in its School of Public Health and Community Medicine and its School of Medicine. The creation of this department has generated significant enthusiasm throughout the university and the Seattle community as a new paradigm for addressing global health education, research, and service. Placing the new Department of Global Health in two university schools and finding the appropriate niche for the department among the university's many global health initiatives presented challenges, as well as opportunities. This article describes the goals of the department, the process by which it was created, and what it expects to accomplish.  相似文献   
69.
70.
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