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   170092篇
  免费   9740篇
  国内免费   425篇
耳鼻咽喉   2223篇
儿科学   5560篇
妇产科学   3570篇
基础医学   23036篇
口腔科学   7501篇
临床医学   12409篇
内科学   38132篇
皮肤病学   4327篇
神经病学   14155篇
特种医学   5261篇
外国民族医学   26篇
外科学   20974篇
综合类   1386篇
现状与发展   1篇
一般理论   60篇
预防医学   17777篇
眼科学   3146篇
药学   10283篇
中国医学   688篇
肿瘤学   9742篇
  2023年   882篇
  2022年   1933篇
  2021年   3605篇
  2020年   2418篇
  2019年   3410篇
  2018年   4811篇
  2017年   3610篇
  2016年   3350篇
  2015年   3924篇
  2014年   5390篇
  2013年   6807篇
  2012年   10615篇
  2011年   11094篇
  2010年   5597篇
  2009年   5035篇
  2008年   8577篇
  2007年   9190篇
  2006年   8515篇
  2005年   8798篇
  2004年   8295篇
  2003年   7572篇
  2002年   5630篇
  2001年   4942篇
  2000年   4941篇
  1999年   4340篇
  1998年   1535篇
  1997年   1282篇
  1996年   1270篇
  1995年   1077篇
  1994年   1069篇
  1993年   975篇
  1992年   2648篇
  1991年   2565篇
  1990年   2336篇
  1989年   2335篇
  1988年   2107篇
  1987年   1955篇
  1986年   1833篇
  1985年   1751篇
  1984年   1254篇
  1983年   1009篇
  1982年   565篇
  1981年   512篇
  1980年   492篇
  1979年   919篇
  1978年   604篇
  1977年   474篇
  1975年   542篇
  1974年   539篇
  1973年   540篇
排序方式: 共有10000条查询结果,搜索用时 24 毫秒
991.
Mouse peritoneal M phi and human blood monocytes were assayed for their antitumor activity in vitro with a cytolysis, a cytostasis and a cytotoxicity test performed in parallel. Both natural and stimulus-induced M phi antitumor capacities were assessed. Results indicate that natural cytolytic activity of unstimulated M phi is generally unable to restrict final tumor cell growth, since it is not coupled with cytostatic capacity. In contrast, exposure of M phi in vitro to either MAF or IFN-beta, besides augmenting M phi cytolytic capacity, induced a very significant cytostatic activity and thus efficiently restricted the survival of tumor cells.  相似文献   
992.
Trisomy 6qter   总被引:2,自引:0,他引:2  
A previously reported patient with trisomy for the distal part of 6q was shown by R-banding to be trisomic for 6q26qter, due to a t(6;22)(q26;p12) mat. Altogether nine patients with 6qter trisomy have been reported. The main features of the 6qter trisomy syndrome are: severe mental and growth retardation; acrocephaly and brachycephaly; a carp-shaped mouth; micrognathia; a very short neck with unusual anterior webbing; joint contractures; the absence of severe inner organ malformations; and survival into adulthood.  相似文献   
993.
A 4-year-old boy had hemolytic uremic syndrome (HUS) associated with depression of serum C3 level, a B-hemolytic streptococcal throat infection, and an elevated level of antistreptolysin O titer. In addition to the characteristic histologic changes associated with this syndrome, substantial infiltration of polymorphonuclear leukocytes and nodular deposits of C3 globulin were seen in the glomeruli of the first biopsy specimen. Two months after clinical remission, he had a recurrence of hemolytic anemia, thrombocytopenia, and acute renal failure. The serum C3 concentration had decreased again, and serum C3NeF was detected in the serum. The typical changes associated with HUS were still present on electron microscopy. Bilateral nephrectomy and renal transplantation were done because of the development of uncontrollable severe hypertension and increasing azotemia. This patient had three manifestations of HUS, but because of several differences, such as hypocomplementemia, serum C3NeF, a recurrence, and persistent glomerular deposits of C3 globulin, he appears to have had a different form of the syndrome.  相似文献   
994.
The hunt for genes influencing behavior may be aided by the study of intermediate phenotypes for several reasons. First, intermediate phenotypes may be influenced by only a few genes, which facilitates their detection. Second, many intermediate phenotypes can be measured on a continuous quantitative scale and thus can be assessed in affected and unaffected individuals. Continuous measures increase the statistical power to detect genetic effects (Neale et al., 1994), and allow studies to be designed to collect data from informative subjects such as extreme concordant or discordant pairs. Intermediate phenotypes for discrete traits, such as psychiatric disorders, can be neurotransmitter levels, brain function, or structure. In this paper we conduct a multivariate analysis of data from 111 twin pairs and 34 additional siblings on cerebellar volume, intracranial space, and body height. The analysis is carried out on the raw data and specifies a model for the mean and the covariance structure. Results suggest that cerebellar volume and intracranial space vary with age and sex. Brain volumes tend to decrease slightly with age, and males generally have a larger brain volume than females. The remaining phenotypic variance of cerebellar volume is largely genetic (88%). These genetic factors partly overlap with the genetic factors that explain variance in intracranial space and body height. The applied method is presented as a general approach for the analysis of intermediate phenotypes in which the effects of correlated variables on the observed scores are modeled through multivariate analysis.  相似文献   
995.
996.
997.
A patient with an interstitial deletion of the short arm of chromosome 6   总被引:1,自引:0,他引:1  
The clinical history and subsequent progress of a child with an interstitial deletion in the short arm of chromosome 6 is described. This abnormality coupled with a reduced Hageman factor (Factor XII) led to an earlier publication which suggested that this gene was localized to the breakpoint region involved. A review of similar phenotypes from the literature is presented.  相似文献   
998.
Three commercially available assays for the detection of human immunodeficiency virus (HIV) antibodies-Vironostika enzyme immunoassay (EIA), Wellcozyme competitive EIA, and JLC Allaman indirect immunofluorescence assay--were tested on 300 serum samples from African subjects with and without HIV-related conditions. Two experimental assays both rapid and simple to perform (Biotech dip stick and Cambridge Bioscience latex agglutination) were also evaluated on the same serum samples. The results were compared with those of a commercial Western blot (WB) (immunoblot) assay from Biotech, used as the reference technique. All assays were tested in the laboratory of the AIDS Project in Kigali, Rwanda. Calculated specificity ranged from 90.8% (dip stick) to 98.6% (Vironostika EIA, Wellcozyme competitive EIA, and Cambridge Bioscience latex agglutination). Sensitivity ranged from 95.2% (Cambridge Bioscience latex agglutination) to 98.0% (Vironstika EIA) and JLC indirect immunofluorescence assay). However, the sensitivity of the latex agglutination test improved to 98.6% after the prozone effect was controlled for by serial twofold dilution of latex agglutination-negative, WB-positive samples. In situations with a high prevalence of HIV infection, any one of these tests can be regarded as an alternative to the more expensive, time-consuming, and difficult WB assay.  相似文献   
999.
The left ventricular subendocardial and subepicardial layers of six perfused rabbit hearts were tested for enzymatic and non-enzymatic antioxidant defences and for lipid peroxidation. The subendocardium showed significantly lower catalase activity and contents of non-protein thiol compounds and vitamin E associated with a higher degree of lipid peroxidation. The activities of Cu,Zn- and Mn-superoxide dismutases, glutathione reductase, -glutamylcysteine synthetase and -glutamyl transpeptidase showed no significant transmural differences, and Se-independent glutathione peroxidase activity was not detectable in either layer. Comparable results were observed in another group of six unperfused rabbit hearts. In five H2O2-perfused rabbit hearts, lipid peroxidation was higher, and myocardial creatine phosphokinase activity lower, in the subendocarium than in the subepicardium. In this group, only the subendocardium had significantly higher lipid peroxidation levels than the control hearts. Thus, a lower antioxidant capacity and a greater oxidative stress are present in the rabbit subendocardium. These findings could provide insight into the problem of subendocardial vulnerability to free radical-mediated processes, such as occurs in ischaemia-reperfusion injury.  相似文献   
1000.
Clementi  M.  Testa  I.  Bagnarelli  P.  Festa  A.  Pauri  P.  Brugia  M.  Calegari  L.  de Martinis  C. 《Archives of virology》1984,81(1-2):177-184
Summary Although its action at the molecular level is not completely understood, insulin, as well as its antagonist glucagon, certaily plays an important role in the modulation of protein synthesis.In order to observe whether insulin is involved in virus gene expression, we studied its effect on PLC/PRF/5 human hepatoma cell line, which posses HBV DNA sequences integrated at several sites.While human insulin had no effect on cell growth and increased the production of two plasma proteins, a selective inhibitory effect on HBsAg production could be detected.This observation might be useful for further studies both on virus gene expression and insulin action at the molecular level.With 3 Figures  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