首页 | 官方网站   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   21910篇
  免费   2566篇
  国内免费   807篇
医药卫生   25283篇
  2024年   62篇
  2023年   293篇
  2022年   721篇
  2021年   942篇
  2020年   887篇
  2019年   866篇
  2018年   881篇
  2017年   967篇
  2016年   1030篇
  2015年   987篇
  2014年   1520篇
  2013年   1565篇
  2012年   1574篇
  2011年   1593篇
  2010年   1268篇
  2009年   936篇
  2008年   1106篇
  2007年   1087篇
  2006年   1019篇
  2005年   769篇
  2004年   669篇
  2003年   581篇
  2002年   469篇
  2001年   438篇
  2000年   359篇
  1999年   294篇
  1998年   198篇
  1997年   224篇
  1996年   186篇
  1995年   224篇
  1994年   187篇
  1993年   155篇
  1992年   135篇
  1991年   113篇
  1990年   105篇
  1989年   84篇
  1988年   67篇
  1987年   88篇
  1986年   60篇
  1985年   122篇
  1984年   101篇
  1983年   87篇
  1982年   73篇
  1981年   58篇
  1980年   45篇
  1979年   28篇
  1978年   21篇
  1977年   8篇
  1976年   9篇
  1973年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
目的 定量研究血液灌流对有机磷农药硫线磷和其解毒药阿托品的吸附作用.方法 模拟临床血液灌流装置,对含硫线磷和硫酸阿托品的血样进行灌流吸附,分别用毛细管气相色谱法和高效液相色谱法测定硫线磷和硫酸阿托品的残留量.结果 吸附剂用量为0.5、1.0和1.5 g,包膜活性炭在灌流2.0 h后硫线磷的清除率均能达到90%以上,硫酸阿托品的清除率依次为61.9%、84.9%和88.9%;HA230树脂在灌流1.5 h后硫线磷清除率都达到90%以上,硫酸阿托品的清除率也依次高达88.0%、97.2%和98.4%;包膜活性炭灌流3.0h后,硫酸阿托品与硫线磷的比值最高为灌流前的10.1倍,而HA230树脂灌流后,此比值最高为灌流前的6.7倍.结论 包膜活性炭和HA230吸附树脂血液灌流1.5~2.0 h均能清除血中大部分硫线磷,而且均能增加血中硫酸阿托品和硫线磷浓度的比值.  相似文献   
112.
The structural basis of the high affinity interleukin-2 receptorwhich was previously reconstituted in a cultured murine T cellline, EL4 by expressing either wild-type Tac antigen complementaryDNA (cDNA) or a chimeric cDNA was characterized. The chimericcDNA encodes a membrane portion whose extracellular portionconsists of that of Tac antigen whereas transmembrane and cytoplasmicportions consists of those the human insulin beta chain. TheTac antigen/anti-Tac antibody complex was treated by chemicalcrosslinking reagents, purified by goat anti-mouse immunoglobulin(lg), and was analysed by SDS–PAGE. We here demonstrated the presence in mouse EL4 transfectantsof a novel membrane protein which is closely associated withthe products of transfected cDNAs in the absence of interleukln-2.The protein is 75 kDa in size and is detected in cells whichexpress high affinity interieukln-2 receptor but not in cellswhich only express low affinity interleukin-2 receptor. Thetransmembrane region and the cytoplasmic region of Tac antigenis not necessary for the formation of the complex consistingof Tac antigen and 75 kDa molecule, indicating that a murine75 kDa molecule associates with Tac antigen extra-cellularly.  相似文献   
113.
中国恒河猴(Macaca mulatta)外周血CD4+CD25+T淋巴细胞的研究   总被引:1,自引:1,他引:1  
目的:研究中国恒河猴外周血中CD4 CD25 T淋巴细胞亚群及其分布频率。方法:利用流式细胞术对50只中国恒河猴外周血CD4 CD25 T淋巴细胞进行了分析。结果:发现所有被检测的恒河猴个体中均存在明显的CD4 CD25 T淋巴细胞亚群;CD4 CD25 T淋巴细胞大约占CD4 T淋巴细胞的9.1%(变化范围为2.6%~18.1%);其中CD4 CD25highT淋巴细胞约占2.5%(0.3%~5.5%)。对不同年龄和性别个体中CD4 CD25 T淋巴细胞频率的初步分析未发现统计学上有年龄或性别差异。结论:中国恒河猴可用于与CD4 CD25 T细胞相关的人类疾病的研究中。  相似文献   
114.
Objective To study on adsorption effect of cadusafos and atropine sulfate by hemoperfusion.Method Hemoperfusions were performed for sheep blood samples with cadusafos and atropineby through imitated extracorporeal closed circulating perfusion apparatus.Residual cadusafos was determined by gas chromatography and residual atropine was determined by high performance liquid chromatography.Result Dose of adsorption agent was 0.5,1.0 and 1.5 g,respectively.Two hours after hemoperfusion with membrane coated activated charcoal,clearance rate of cadusafos in 3 groups all exceeded 90%.and clearance rate of atropine sulfate was 61.9%,84.9%,88.9%,respectively.One and a half hours after hemoperfusion with HA230 absorption resin,clearance rate of eadusafos in 3 groups all exceeded 90%,and clearance rate of atropine sulfate was 88.0%,97.2%,98.4%,respectively.Three hours after hemoperfusion with membrane coated activated charcoal,The concentration ratio of cadusafos and atropine sulfate in blood promoted to 10.1 times,and the ratio was 6.7 times after hemoperfusion with HA230 absorption resin.Conclusion It suggested that cadusafos were mostly removed from blood after 1.5~2.0hours hemoperfusion with membrane activated charcoal or HA230 absorption resin.The concentration ratio of cadusafos and atropine sulfate in blood will increased after hemoperfusion.  相似文献   
115.
The effects of two kinds of induction speed of sevoflurane anesthesia on the EEG pattern were compared in the same individual using medical student volunteers: a first exposure of 4% was given, followed after full recovery, by incremental doses of 1, 2 and 4% successively, each being administered for 10min. The arterial blood level of the anesthetic was measured using gaschromatograph. The changes of EEG pattern during fast induction with 4% were not represented by the abbreviation of those observed during the slow induction with the incremental doses. The administration of 4% induced a sudden appearance of high voltage, rhythmic slow waves of 2–3Hz at 1–3min when the arterial blood anesthetic level increased maximally, which was then followed by a pattern of faster activities of 10–14Hz mixed with 5–8Hz slow waves. In contrast, the administration of incremental doses induced an increase in frequency and amplitude of EEG activities in the light plane, followed by their decreases in deeper planes. The final EEG patterns were identical for both these methods of induction. These findings confirmed our previous hypothesis that not only the arterial blood level of anesthetics but the rate of its increase are important factors determining the EEG pattern of anesthesia.(Avramov MN et al.: Effects of different speeds of induction with sevoflurane on the EEG in man. J Anesth 1: 1–7, 1987)  相似文献   
116.
Summary The effect of recurrent periods of ischemia on the myocardium was investigated in 15 open-chest dogs. Ischemia was produced by 3 minutes of proximal occlusion of the left anterior descending coronary artery. Each occlusion was followed by reperfusion of 3 minutes duration. Forty occlusions with a total of 120 minutes of ischemia were performed, and regional function (sonomicrometry) as well as high energy phosphates (needle biopsies) were determined at the end of the 5th, 20th, and 40th period of ischemia and reperfusion. The first periods of ischemia had a cumulative effect both on regional postischemic function (44% and 59% respectively of preischemic control after 20 occlusions) and on the ATP content, but with increasing number of occlusions the additive effects became smaller (ATP reduction/mol/gww/per occlusion). The ATP breakdown per occlusion was diminished with increasing number of periods of ischemia, and no significant adenosine was measured in the ischemic myocardium. Higher than normal postischemic creatine phosphate levels (9.1 mol/g w w at the 40th reperfusion vs. 6.7 mol/gw w control) indicated a functioning oxidative phosphorylation in the presence of an ATP utilization problem at the sarcomere level, because indicators of the cellular energy level (energy charge, free energy change of ATP hydrolysis) quickly normalized during reperfusion. Stunned myocardium is therefore not a problem of energy supply but rather of energy utilization. Reduced ATP utilization and regional dysfunction are the expressions of the same cellular defect which resides either in the ATP-splitting contractile apparatus or in the electromechanical coupling. Contractile dysfunction during reperfusion protects the heart against subsequent periods of ischemia because ATP turnover is reduced.Parts of the results were presented at the 57th Sessions of the American Heart Association, Miami, Florida/U.S.A. 1984  相似文献   
117.
Clinical methods in psychiatric genetics. II. The high risk approach   总被引:2,自引:0,他引:2  
The study of individuals at "high" risk for developing psychiatric disorders is useful in confirming that a biological trait marker identified in patient populations is also present in genetically susceptible individuals who have never been ill, and predicts the future onset of illness. We outline a systematic method for deciding which variables to choose and how many individuals are required in order for a study to have sufficient power. We demonstrate how these decisions depend on the assumptions that can be made with regard to the mode of inheritance of the biological trait, the relationship of the biological trait to illness, and the magnitude of the mean difference observed between patients and controls. We also quantify the increased power of studying offspring of two affected parents rather than offspring of one affected parent.  相似文献   
118.
Hyperhidrosis and its surgical treatment   总被引:2,自引:0,他引:2  
Summary 111 sections of high thoracic sympathectomies in 60 cases suffering from primary palmar hyperhidrosis are reported. Surgical results and postoperative complications are discussed in detail. Complications were few in number and were of a transitory nature. No mortality occurred in our series. Various surgical and nonsurgical procedures of treatment are reviewed. Surgical intervention remains the treatment of ehoice in essential idiopathic hyperhidrosis.  相似文献   
119.
作者用“点值法”对成都市内和郊区842例从事轻、中、重劳动的健康工人、农民和战士作了MEFV曲线和常规肺功能测定,发现工人和农民在低肺容积时流量增加,在高、中肺容积时流量下降,并以农民最明显,重劳动工人次之,轻、中劳动工人较不明显,战士则相反。揭示不同的体力活动方式及生活条件可导致不同肺容积时的流量改变,以适应其代谢增强时的耗氧需求。  相似文献   
120.
目的调查泸州市中老年男性艾滋病疫情高发的原因,为制订有针对性的干预策略提供依据。方法采用整群抽样的方法,2019年对473例新报告的泸州市50岁及以上中老年男性艾滋病感染者/病人展开性伴、安全套使用及商业性行为等主要内容的问卷调查,采用卡方检验进行差异性分析,检验水准α=0.05。结果分别有81.6%、62.8%和10.1%的人有商业性行为、固定性伴/配偶和临时性伴,除固定性伴比例随年龄增长呈下降趋势(χ2趋势=6.934,P=0.008)外,其余性伴类型没有统计学差异。与不同性伴发生性关系,近1年从未使用安全套比例均超过90%。无配偶(35.8%)、配偶不在身边(30.8%)、诱惑/好玩(22.4%)是寻找商业性伴的前3位原因;性交易对象以本地为主,本乡镇占56.0%。固定场所(46.3%)和接头拉客(43.7%)是最主要的寻找商业性伴方式。多数性交易价格低于50元,年龄越大,<50元的占比越大(50岁~59岁、60岁~69岁、≥70岁分别为52.1%、78.0%和80.0%),差异有统计学意义(χ2=22.061,P<0.001)。结论中老年男性通过寻找商业性伴满足其性需求,交易价格偏低。该群体存在多性伴行为、基本不使用安全套行为等现象,是其艾滋病疫情快速增长的重要原因。  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-23

京公网安备 11010802026262号