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   20879篇
  免费   2176篇
  国内免费   1099篇
耳鼻咽喉   154篇
儿科学   722篇
妇产科学   308篇
基础医学   2332篇
口腔科学   342篇
临床医学   2764篇
内科学   2994篇
皮肤病学   232篇
神经病学   1057篇
特种医学   814篇
外国民族医学   6篇
外科学   2610篇
综合类   3173篇
现状与发展   3篇
一般理论   3篇
预防医学   1664篇
眼科学   415篇
药学   2066篇
  17篇
中国医学   962篇
肿瘤学   1516篇
  2024年   67篇
  2023年   263篇
  2022年   625篇
  2021年   999篇
  2020年   743篇
  2019年   644篇
  2018年   768篇
  2017年   690篇
  2016年   615篇
  2015年   915篇
  2014年   1101篇
  2013年   1033篇
  2012年   1486篇
  2011年   1533篇
  2010年   1085篇
  2009年   836篇
  2008年   1081篇
  2007年   1033篇
  2006年   1038篇
  2005年   938篇
  2004年   729篇
  2003年   678篇
  2002年   615篇
  2001年   538篇
  2000年   406篇
  1999年   369篇
  1998年   208篇
  1997年   211篇
  1996年   149篇
  1995年   120篇
  1994年   136篇
  1993年   103篇
  1992年   198篇
  1991年   175篇
  1990年   147篇
  1989年   139篇
  1988年   155篇
  1987年   115篇
  1986年   129篇
  1985年   121篇
  1984年   103篇
  1983年   67篇
  1982年   57篇
  1981年   66篇
  1979年   97篇
  1978年   56篇
  1974年   57篇
  1973年   73篇
  1972年   58篇
  1971年   62篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
The most popular techniques for assessing color vision, the pseudoisochromatic tests, have been found to differ widely in their sensitivity to changes in viewing conditions. A significant number of color-normal subjects will be misdiagnosed as color defective by some of the standard tests with even relatively minor variations from standardized viewing conditions. These results appear to have strong implications for the use of the tests in many applied settings which precise control over viewing conditions is difficult. In particular, as the consequences of a misdiagnosis become very serious, the tests must be used with special caution. If we were to recommend one test for use, our findings point to the Ishihara, which appears impervious to variation in viewing conditions.  相似文献   
72.
A Monte Carlo calculation for the initial electron energy spectra produced in semi-infinite and finite water phantoms irradiated by photons of energies up to 2 MeV and photons from 60Co are presented incorporating successive Compton scattering, photoelectric absorption and Auger effect. The backscattering of photons through the top of the phantom and transmission of photons out of the finite phantom through the sides also are considered. The results are compared with the earlier calculation for infinite water phantom of Turner et al. who assumed that all the photons remained in the water until they were absorbed. It is found that inclusion of backscattering in a semi-infinite phantom yields significantly different results from those of Turner et al. for the infinite phantom. It is also found that backscattering and transmission of the photons through the sides of the finite phantom further alter the initial energy spectra of electrons, as well as the average number of electrons per photon at different photon incident energies.  相似文献   
73.
M W Long  N Williams 《Blood》1981,58(5):1032-1039
Three types of immature megakaryocytes, detected by their morphological properties, have been characterized in bone marrow of normal C57BL/6 mice. Morphological classification of these cells was carried out by determining (1) presence and relative amount of acetylcholinesterase, (2) cell size, (3) nuclear/cytoplasm ratio, and (4) nuclear shape. The immature megakaryocytes were classified as: (A) cells distinguished by a round nucleus (10.6 +/- 1.1 mu diameter; mean +/- SEM), which had the highest nucleus / cytoplasm ratio and lowest content of acetylcholinesterase; (B) cells with an indented nucleus (13.0 +/- 1.9 mu diameter), which had increased acetylcholinesterase content and reduced nucleus/cytoplasm ratio compared to the round-nucleus cell type; and (C) lobed-nucleus cells (14.5 +/- 2.9 mu diameter), which showed further increase in acetylcholinesterase content and reduction in nucleus/cytoplasm ratio. Increased numbers of immature megakaryocytes were detected, indicating that a proportion of these cells are undetected using conventional staining techniques. Based on the observed alterations in size, acetylcholinesterase content, and nuclear complexity, it was concluded that these cells constitute part of a progressive maturation sequence intermediate between the progenitor cell (CFU-Mk) and mature easily recognizable megakaryocytes.  相似文献   
74.
两种剂量氟碳部分液体通气治疗犬吸入伤的比较研究   总被引:1,自引:0,他引:1  
目的:对比研究两种剂量氟碳(PFC)部分液体通气(PLV)对蒸气吸入性损伤犬的血气和血流动力学的影响,方法:将健康犬15条随机分面两组,即PFC6ml/kg组(PFC-6)和PFC 12ml/kg(PFC-12)组,采用蒸气吸入造成吸入性损伤模型后经气管内注入PFC实施部分液体通气(PLV)治疗,观察治疗后30min,60min,90min血气,血流动力学参数的变化,结果:PFC-6组PaO2在PLV治疗30min后明显升高(P<0.05),在治疗60min,90min生的PaO2与致伤值比较无统计学意义,而PFC-12组的PaO2在PLV治疗后30min,60min,90min均明显升高(P<0.05),与PFC-6组相比,PFC-12组的PaO2,PvO2均呈上升趋势,但未达显著水平(P>0.05),在PLV治疗后各时间点的PaCO2HR,MAP,CVP 致伤值相比均无明显变化(P>0.05),两组之间比较,各对应时间点的PaCO2,HR,MAP,CVP也均无明显变化(P>0.05),结论:氟碳部分液体通气是一种新的通气技术,它能明显改善蒸气入伤犬的氧合作用,对血液动力学参数无不良影响,两种剂量氟碳部分液体通气治疗蒸气吸入性损伤未呈现明显剂量一效应关系。  相似文献   
75.
Two elderly patients, involved in separate motor vehicle accidents, sustained blunt chest injury resulting in rupture of their thoracic aortas. The initial chest radiographs showed the presence of a calcified ring fractured in two places with lateral displacement of a calcified fragment by haematoma. This ‘broken halo sign’ is a radiographic sign not previously well described in the literature. The presence of a disrupted aortic ring in the elderly patient, associated with the appropriate mechanism of injury, should alert the clinician to the potential diagnosis of traumatic rupture of the thoracic aorta (TRTA).  相似文献   
76.
Nitric oxide (NO), originally identified as the mediator of endothelial-dependent relaxation of vascular smooth muscle, is now known to also have cytotoxic effects under certain conditions. Thus, we have investigated the effects of inhibition of NO synthesis on ischemia/reperfusion injury in the rabbit rectus femoris muscle. Three and a half hours of ischemia and 24 hours of reperfusion resulted in a 56% loss of viability. In muscles receiving an infusion of the nitric oxide synthase inhibitor, L-NIO (30 μM), the loss of viability was reduced to 15%. Post-ischemic blood flow was increased in muscles receiving a saline infusion, whereas there was a marked decrease in blood flow for at least the first 60 minutes of reperfusion in muscles treated with L-NIO (30 μM). The increase in myeloperoxidase levels (indicative of neutrophil accumulation) following 24 hours of reperfusion was attenuated with L-NIO infusion by approximately 50% and the reperfusion-induced edema was also attenuated in L-NIO treated muscle. These findings suggest that endogenous NO production during ischemia/reperfusion injury may be deleterious to muscle survival. © 1994 Wiley-Liss, Inc.  相似文献   
77.
用PCR—RFLP和16SrDNA指纹图法分析幽门螺杆菌基因型   总被引:1,自引:1,他引:0  
本文建立了PCR-RFLP和16srDNA指纹图法.对19株幽门螺杆菌(HP)进行基因型分析:HP尿素酶C基因的PCR扩增产物.分别用HindⅢ、HaeⅢ、AluⅠ酶切,结果显示:每个酶均将19株HP分为3种RFLP图谱.综合HindⅢ,HaeⅢ和AluⅠ酶切结果,19株HP分为10个酶切带型;PCR扩增HP标准株16SrRNA基因,地高辛标记制备550bp探针,19株HPDNA分别经HaeⅢ和EcoRⅠ酶切、电泳后,通过Southern杂交获16SrDNA指纹图,结果显示:HaeⅢ酶切分为14个杂交带型,EcoRⅠ酶切19株HP杂交带型均不同。本实验表明:上述两种方法重复性好,分群力高,可准确有效地对HP作出鉴定并将其分型。19株HP株间存在基因型差异。  相似文献   
78.
用二甲苯所致的急性炎症模型观察了神效止痛膏的抗急性炎症作用.用扭体法、热板法观察了神效止痛膏对小鼠的镇痛作用.结果表明,神效止痛膏有很好的镇痛作用.  相似文献   
79.
80.
微创手术治疗高血压脑出血   总被引:10,自引:0,他引:10  
目的 探讨微创手术治疗高血压脑出血的临床疗效。方法 132例高血压脑出血分成微创手术组(68例)和传统开颅手术组(64例),分析两组手术的特点和手术时机,比较两组手术治疗的疗效。结果 微创组术后GOS良好23例、中残24例、重残9例、植物生存3例、死亡9例;传统组术GOS良好16例、中残15例、重残12例、植物生存6例、死亡15例。两组超早期或早期手术均有良好的预后,而微创组效果更佳。结论 微创手术治疗高血压脑出血能明显提高临床疗效,降低病死率。  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