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   3217409篇
  免费   229971篇
  国内免费   8670篇
耳鼻咽喉   43306篇
儿科学   107434篇
妇产科学   88804篇
基础医学   455451篇
口腔科学   89377篇
临床医学   293855篇
内科学   629046篇
皮肤病学   75869篇
神经病学   262714篇
特种医学   123661篇
外国民族医学   1010篇
外科学   479122篇
综合类   67463篇
现状与发展   5篇
一般理论   1270篇
预防医学   248784篇
眼科学   72359篇
药学   234522篇
  11篇
中国医学   6568篇
肿瘤学   175419篇
  2019年   25105篇
  2018年   35522篇
  2017年   27336篇
  2016年   31450篇
  2015年   35435篇
  2014年   48766篇
  2013年   73975篇
  2012年   97954篇
  2011年   103752篇
  2010年   62404篇
  2009年   59594篇
  2008年   97005篇
  2007年   102882篇
  2006年   104855篇
  2005年   100458篇
  2004年   97156篇
  2003年   93812篇
  2002年   90485篇
  2001年   153081篇
  2000年   156822篇
  1999年   132330篇
  1998年   38095篇
  1997年   33970篇
  1996年   34036篇
  1995年   32959篇
  1994年   30383篇
  1993年   28328篇
  1992年   103645篇
  1991年   100197篇
  1990年   97371篇
  1989年   94045篇
  1988年   85976篇
  1987年   84771篇
  1986年   79381篇
  1985年   76049篇
  1984年   56699篇
  1983年   48062篇
  1982年   28601篇
  1981年   25609篇
  1979年   50558篇
  1978年   35945篇
  1977年   30477篇
  1976年   28403篇
  1975年   30162篇
  1974年   35906篇
  1973年   34196篇
  1972年   31847篇
  1971年   29643篇
  1970年   27304篇
  1969年   26053篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Dimensional measurement of seasonal variation in mood and behavior.   总被引:1,自引:0,他引:1  
Recent epidemiologic studies have found that the behaviors that characterize seasonal affective disorder (SAD) show seasonal variation in 92%-95% of the general population, suggesting that seasonal variation in behavior and mood is a continuous, dimensional variable extending throughout the general population, defined at the upper extreme by SAD. Research into population seasonality will require a dimensional measure of seasonal variation in mood and behavior that produces a broad, finely graded distribution of seasonality scores sensitive to individual differences throughout the entire range of scores. Accordingly, the Inventory of Seasonal Variation (ISV) was developed as such a measure. This study demonstrated that the ISV has high internal structural validity and is highly sensitive to individual differences in seasonality across its entire range of scores in the normal population. This latter characteristic is not shared by other existing measures of seasonality. Initial external validity of the ISV was supported in that the mean of ISV scores of a SAD sample was found to lie at the 97th percentile of the normal population of scores. Analysis of ISV scores revealed that a winter pattern of seasonality was reported by over 95% of subjects, a pattern that was more pronounced in women than men, while a summer type of seasonality was reported by only 0.6% of the general population.  相似文献   
962.
963.
This paper is an attempt to assess the relevance of the inhibitors of fibrinolysis for clot lysis in selected disease states and to discuss the mechanisms leading to acquired abnormal levels of such inhibitors. When compared to 20 control subjects the 30 hypertriglyceridemic patients (14 with type IIb and 16 with type IV) displayed significantly (p less than 0.001) increased plasma plasminogen activator inhibitor (PAI) activity (221 +/- 88% and 290 +/- 104% respectively; mean +/- SD), moderately (p less than 0.01) increased alpha 2 antiplasmin (alpha 2AP) level (112 +/- 11% and 115 +/- 16%) and accordingly an obviously prolonged dilute blood clot lysis time (DBCLT). Neither PAI activity and alpha 2AP level nor DBCLT were significantly different from controls in the 10 patients with hyperlipoproteinemia type IIa. The 18 patients with severe hepatic cirrhosis had low alpha 2AP level (59 +/- 19.7%) and accelerated clot lysis, while mean PAI activity (160 +/- 87%) was slightly (p less than 0.05) increased. In the 17 nephrotic patients alpha 2AP was increased (115 +/- 12%) while PAI activity was similar to controls and DBCLT rather shorter. Two liver secretion enzymes, namely serum cholinesterase and plasma protein C, were found to be decreased in cirrhotic patients, similar to control values in hyperlipoproteinemia type IIa and obviously increased in nephrotic patients as well as in hypertriglyceridemic subjects. The relevance of PAI and alpha 2AP for clot lysis was considered in relation to data in the literature concerning the behaviour of t-PA and factor XIII.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
964.
The Flinders Sensitive Line (FSL) of rats has been selectively bred to have increased sensitivity to cholinergic agonists. However, these rats exhibit altered responsiveness to a number of noncholinergic agents, such as apomorphine, buspirone and ethanol. This study compared the FSL and control Flinders Resistant Line (FRL) rats in terms of their hyperthermic response to the phencyclidine (PCP) receptor agonist, MK-801 (0.2 mg/kg SC) and their MK-801 binding characteristics. We have found that FSL rats react with a delayed hyperthermia, having a significantly lower hyperthermia for the first 120 min of observation. Thereafter the response does not differ in FSL and FRL rats. Both groups had similar affinities and numbers of [3H]MK-801 binding sites in the hippocampus/cerebral cortex. Pretreatment with scopolamine (1 mg/kg SC) failed to affect MK-801-induced hyperthermia in either line of rats. These findings suggest that selective breeding of FSL rats attenuated the secondary mechanisms involved in the PCP receptor-mediated hyperthermic response. However, by itself cholinergic supersensitivity does not appear to be a major factor in the blunted responsiveness of FSL rats to MK-801.  相似文献   
965.
Abstract— Biomedical determinants of dental caries have been more extensively investigated than psychosocial factors and their impact on caries prevalence and incidence seems to be greater. However, a majority of these investigations relate to children and adolescents. An implementation of social and psychologic variables may be more relevant regarding dental caries in adults. In addition, a multidisciplinary approach might improve our understanding of dental caries as a multifactorial disease and bridge the gap between a biomedical concept and a more holistic approach to dental health.  相似文献   
966.
967.
968.
969.
Trypsin and Zymosan induce an increase in respiration activity of cultivated endothelial cells. These effects are not due to the production of oxygen radicals. The effect of trypsin will be explained by interfering with the cellular homeostasis of calcium. The stimulated respiration after incubation with zymosan may be connected with the increased phagocytosis.  相似文献   
970.
We have previously shown that the colon carcinoma (LS174T) xenografts that emerged shortly after radioimmunotherapy with 90Y-labeled anti-CEA monoclonal antibody (MAb) ZCE025 lacked significant expression of CEA in comparison with the untreated tumors. The present study was designed to establish if the immunophenotype of the treated tumors was the result of CEA specific therapy and if the effect was permanent. Athymic mice bearing LS174T tumors were treated either with 120 mu Ci of 90Y-ZCE025, an equal dose of 90Y-96.5 (nonspecific MAb), or received no treatment. When the treated tumors grew to approximately 1.5 cm in diameter (6 weeks after therapy), they were resected and aliquoted to be transplanted to other mice, plated in tissue culture, fixed in formalin, and homogenized for CEA quantitation. The procedure was repeated 3 times (a total of 4 months after treatment). The CEA content was evaluated 2 and 6 weeks after therapy and when the tumors were transplanted. We confirmed a 4-fold decrease of CEA in the resurgent tumors 6 weeks after specific 90Y-ZCE025 therapy, which was twice the decrease experienced by the tumors treated with nonspecific 90Y-96.5, indicating substantial and specific killing of CEA-expressing cells. The CEA content slowly but progressively increased with each new pass of the tumor in the mice, reaching approximately one-half the value of the controls at the end of the study. The resurgent tumors were also studied by immunohistochemistry with MAbs detecting different epitopes of CEA, keratin, TAG-72, and epithelial membrane antigen to evaluate possible additional immunophenotypic changes induced by radioimmunotherapy. Only the expression of TAG-72 (recognized by MAb B72.3) increased immediately after therapy, but it returned to the original levels by the end of the study. These results suggest that: (a) specific radioimmunotherapy with 90Y-ZCE025 selectively kills cells that express higher levels of CEA; (b) the immunophenotype of the surviving fraction of the tumor appears to slowly revert to its original form; and (c) other tumor markers unrelated to CEA can also be affected. These observations have important implications for the design of radioimmunotherapy trials.  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