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   3544篇
  免费   310篇
  国内免费   133篇
耳鼻咽喉   15篇
儿科学   27篇
妇产科学   60篇
基础医学   476篇
口腔科学   83篇
临床医学   226篇
内科学   533篇
皮肤病学   16篇
神经病学   163篇
特种医学   75篇
外科学   215篇
综合类   468篇
预防医学   612篇
眼科学   60篇
药学   383篇
  19篇
中国医学   456篇
肿瘤学   100篇
  2024年   16篇
  2023年   36篇
  2022年   112篇
  2021年   198篇
  2020年   125篇
  2019年   112篇
  2018年   137篇
  2017年   132篇
  2016年   154篇
  2015年   131篇
  2014年   213篇
  2013年   295篇
  2012年   184篇
  2011年   236篇
  2010年   169篇
  2009年   164篇
  2008年   163篇
  2007年   179篇
  2006年   168篇
  2005年   124篇
  2004年   113篇
  2003年   104篇
  2002年   88篇
  2001年   80篇
  2000年   57篇
  1999年   63篇
  1998年   45篇
  1997年   51篇
  1996年   37篇
  1995年   45篇
  1994年   44篇
  1993年   28篇
  1992年   23篇
  1991年   20篇
  1990年   15篇
  1989年   7篇
  1988年   7篇
  1987年   12篇
  1986年   8篇
  1985年   15篇
  1984年   9篇
  1983年   17篇
  1982年   8篇
  1981年   12篇
  1980年   10篇
  1979年   7篇
  1978年   4篇
  1977年   3篇
  1975年   2篇
  1972年   2篇
排序方式: 共有3987条查询结果,搜索用时 31 毫秒
41.
Policy-makers face pressures to improve lives and safeguard public finances sustainably. In this analysis, we estimate the economic importance of the health-care sector in 19 European national economies.We use input–output tables for the year 2010 and sectoral data to estimate a set of multipliers: simple, total, truncated, type I and type II multipliers for output, income, value-added, employment and import multiplier.The analysis reveals similarities in the economic importance of the health-care sector for the national economies of the observed countries. Results suggest prevailing positive effects on national economies (value-added, employment and household income) when spending on health-care sector products and services increases, especially in comparison to the effects of increases in spending in other sectors. The importance of the health-care sector is connected to countries’ levels of development; the benefits are especially promising in countries with lower levels of gross domestic product (GDP) per capita, where changes in the health-care sector have a larger impact on employment in the national economy than similar changes in more developed countries. The health-care sector therefore can play an important role as an instrument of economic policy.  相似文献   
42.
43.
The discovery of a human myeloma protein comprising a kappa L-chain with an increased mol. wt of 30,000) (Bouvet et. al., 1980) prompted investigations on the incidence of such heavier L-chains among other human myeloma proteins. In 105 samples examined, 34 were found to have L-chains heavier than normal (23,000-24,000), ranging from 25,000 up to 31,000, and five of lighter mol. wt (21,000-22,000). These mol. wt abnormalities were detected by electrophoresis in sodium dodecyl sulfate 10% polyacrylamide gels (SDS-PAGE) after reduction with 2-mercaptoethanol. The mol. wt of three of the heavier kappa or lambda chains was also estimated by filtration through a Sephadex G100 column and by sedimentation equilibrium. All three methods indicated a mol. wt increase of about 15-25% as compared with the usual mol. wt. The distribution of the high mol. wt chains among all L-chains examined was found to be 11 out of 62 kappa chains (17.7%) and 23 out of 43 lambda chains (53%) (P less than 0.001). A preferential association of such L-chains with H-chains producing multiple bands in SDS-PAGE (P less than 0.01) and an association between multiple L-chain and multiple H-chain band (P less than 0.05) were also observed. In contrast, no abnormal L-chain was found in immunoglobulins from normal subjects. Spontaneous degradation of the normal H-chains sometimes yielded fragments of 30,000 mol. wt. These fragments were easily distinguishable from abnormal L-chains. The nature of extra mol. wt in heavy L-chains was investigated for the presence of carbohydrate moiety. Four large and three normal size L-chains were examined for amino-sugar and sialic acid content. A small amount (one residue per molecule) of amino-sugar was detected only in two normal and two heavy L-chains, whereas sialic acid was only found in the heaviest (27,000-30,000) L-chains (Lh) and in small percentage (one or two residues per molecule). Total sugar estimation in one Lh chain indicated a proportion not exceeding three or four residues per L-chain (mol. wt 1,000) and this is insufficient to explain the 15-25% (3,600-6,000) mol. wt increase. It is therefore possible that, at least in some heavy myeloma L-chains, an additional peptide is expressed. Whatever the nature of the increase it would be of interest to elucidate whether this is a marker of malignant process or of an intermediate step of normal Ig synthesis.  相似文献   
44.
常温氧合血性心停搏液持续灌注心肌保护效应的实验研究   总被引:2,自引:0,他引:2  
目的 采用随机对比的实验研究方法从测定心肌酶学、氧自由基代谢产物及心肌特异性蛋白几个方面来探讨冷晶体心停搏液间断灌注及常温氧合血性心停搏液连续灌注两种灌注方法的心肌保护效应。方法14只犬随机分为①对照组:冷晶体心停搏液间断灌注;②实验组:常温氧合血性心停搏液连续灌注。采集不同时点的犬冠状静脉窦血为测定标本,测定心肌特异性酶CK-MB、心肌特异性钙蛋白T(cTn-T),氧自由基代谢产物丙二醛(MDA)。结果对照组在主动脉开放后,CK-MB、MDA、cTn-T明显升高,实验组升高幅度较小。两组间比较有显著差异(P<0.01)。结论常温氧合血性心停搏液连续灌注,可以充分保证心肌在常温停跳期间的血供和氧供,避免了心肌缺血缺氧,明显地减轻了心肌缺血再灌注损伤,是一种非缺血性、比较理想的心肌保护方法。  相似文献   
45.
To evaluate the role of thromboxane A2 (TXA2) in ischemic liver injury, the serum changes in thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-K-PGF1) following warm ischemia of the total canine liver were examined, and the protective effect of a TXA2 synthetase inhibitor was assessed. Total liver ischemia was performed for 60 min on two groups of dogs: a control group, in which ischemia alone was performed, and an OKY-046 group, which received a TXA2 synthetase inhibitor. A temporary active portacaval shunt was used to eliminate the effects of splanchnic venous stasis during clamping of the hepatic pedicle. Postoperative changes in liver function, assessed by the transaminase enzyme levels, and in prostaglandins were recorded and the histologic liver findings of both groups 1 week after ischemia were compared. The levels of 6-K-PGF1 increased after reperfusion in both groups, while those of TXB2 increased in the control group but maintained low levels in the OKY-046 group. Liver function was better and histologic changes less marked in the OKY-046 group than in the control group, suggesting the important role of TXA2 in ischemic liver injury and the usefulness of a TXA2 synthetase inhibitor for protecting the liver against ischemic injury.  相似文献   
46.
对 S O2-4 / Zr O2 超强酸体系作为重油催化裂化助剂进行了研究。结果表明,加入适量的 S O2-4 / Zr O2 可提高轻质油收率,并能降低催化剂生焦;在工业催化裂化高温水蒸汽流化的条件下, S O2-4 / Zr O2 超强酸体系中的 B 酸对重油催化裂化起着至关重要的作用。  相似文献   
47.
从伤寒的体质、病因、病理、诊法、辨证、治则、治法、方药及其临床等方面对《伤寒论》研究层面进行分析,对《伤寒论〗研究思路、方法及未来研究发展趋势进行了讨论。  相似文献   
48.
We present a undescribed condition in a girl who died at 8 years of hypertrophic cardiomyopathy. Muscle and endomyocardial biopsies disclosed a selective loss of thick filaments ultrastructurally. In muscle biopsy histochemical abnormalities of myofibrillar AT-Pase were confined to type 1 fibres. Gel electrophoresis of muscle homogenate showed no qualitative abnormalities of slow and fast myosin heavy chains (MHC) and light chains, and the amount of the different myosin isozymes was in agreement with histochemical myofibrillar ATPase findings. The pathogenetic mechanisms have not been elucidated in this case but we suspect an abnormality of the-cardiac MHC gene, the only gene expressed in the heart and in type 1 skeletal muscle fibres.  相似文献   
49.
防风种子中内源抑制物质活性的研究   总被引:19,自引:1,他引:19  
赵敏 《中草药》2004,35(4):441-444
目的 通过防风种子提取物对白菜、小麦、防风抑制活性的研究,探讨防风种子发芽率低,播种后出苗缓慢的原因。方法 制备防风种子粗提物并测定其对白菜、小麦、防风种子萌发和幼苗生长的抑制活性;制备粗提物的乙醚萃取液和乙醚萃取残余液并分别进行纸色谱分离,测定各区段的活性;用不同溶剂和温水(41℃、45℃)浸种,测定各批次浸泡液的抑制活性。结果 防风种子中存在活性较强的内源抑制物质,且其乙醚萃取液在Rf0.6区段对白菜种子萌发抑制活性最强;防风种子粗提物对防风种子萌发和幼根生长也有较强的抑制活性;防风种子粗提物对小麦幼苗的地上部分生长有较强抑制作用;温水浸种可除去大部分内源抑制物质。结论 防风种子内源抑制物质是导致防风种子发芽率低、播种后出苗缓慢的主要原因。  相似文献   
50.
浅谈王士雄对疫病的防治   总被引:1,自引:0,他引:1  
论述清代著名温病学家王士雄对疫病的防治思想,从环境卫生、住房、饮食及药物防治等方面作了总结,其经验对后世疫病防治具有一定的现实意义。  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