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   6018篇
  免费   495篇
  国内免费   76篇
耳鼻咽喉   46篇
儿科学   133篇
妇产科学   222篇
基础医学   883篇
口腔科学   101篇
临床医学   616篇
内科学   1318篇
皮肤病学   167篇
神经病学   425篇
特种医学   394篇
外国民族医学   5篇
外科学   789篇
综合类   80篇
一般理论   5篇
预防医学   522篇
眼科学   52篇
药学   374篇
中国医学   4篇
肿瘤学   453篇
  2021年   77篇
  2019年   71篇
  2018年   80篇
  2017年   64篇
  2016年   73篇
  2015年   77篇
  2014年   120篇
  2013年   169篇
  2012年   250篇
  2011年   275篇
  2010年   162篇
  2009年   158篇
  2008年   269篇
  2007年   316篇
  2006年   235篇
  2005年   247篇
  2004年   251篇
  2003年   249篇
  2002年   213篇
  2001年   215篇
  2000年   227篇
  1999年   168篇
  1998年   126篇
  1997年   117篇
  1996年   92篇
  1995年   74篇
  1994年   85篇
  1993年   68篇
  1992年   151篇
  1991年   118篇
  1990年   132篇
  1989年   131篇
  1988年   135篇
  1987年   131篇
  1986年   94篇
  1985年   108篇
  1984年   82篇
  1983年   67篇
  1981年   46篇
  1980年   38篇
  1979年   60篇
  1978年   51篇
  1977年   43篇
  1975年   43篇
  1974年   50篇
  1973年   51篇
  1972年   43篇
  1971年   48篇
  1969年   38篇
  1967年   45篇
排序方式: 共有6589条查询结果,搜索用时 15 毫秒
21.
From a series of 50 patients with acute decompensation of chronic obstructive lung disease (38 of whom were treated by mechanical ventilation), the authors demonstrate the prognostic value of an easily obtained parameter of respiratory function: the vital capacity restitution curve (VCRC). From daily measurements of vital capacity, beginning on the day of admission, a graph is constructed which shows an initial period of increase in the degree of restitution, followed by stabilization of the values. An analysis of the various parameters embodied in this graph provides information about the prognosis. Such graphs can be divided into 3 zones of prognostic value: a favourable zone, an intermediate zone (mediocre survival with or without mechanical ventilation) and an unfavourable zone (death during the acute phase). Although a favourable prognosis can be made after 4 days of observation and almost always by the 10th day, an unfavourable prognosis cannot be made before the 21st day.  相似文献   
22.
The role of the human histocompatibility complex (HLA) in the pathogenesis of schizophrenia has been suggested in previous reports. We conducted a genetic study in 33 new families. Our linkage analysis, which used the affected sib-pair method, did not provide evidence for nonrandom assortment. Moreover, the results of an association study using the "haplotype relative risk" method failed to confirm the positive association between HLA A9 and schizophrenia. Taken together, our data did not support any relationship of HLA type to schizophrenia.  相似文献   
23.
Hypophosphatasia is a rare inherited disorder characterized by defective bone mineralization and deficiency of serum and tissue liver/ bone/kidney tissue alkaline phosphatase (L/B/K ALP) activity. We report the characterization of tissue-nonspecific alkaline phosphatase (TNSALP) gene mutations in a series of 9 families affected by severe hypophosphatasia. Fourteen distinct mutations were found, 3 of which were previously reported in the North American or Japanese populations. Seven of the 11 new mutations were missense mutations (M45L, R119H, G145V, C184Y and H154Y, D289V, E459K), the four others were 2 single nucleotide deletions (544delG and 1172delC), a mutation affecting donor splice site (862 + 5A) and a nonsense mutation (R411X).  相似文献   
24.
25.
26.
Human polymorphonuclear leukocytes (PMNL) metabolize the potent chemotaxin leukotriene B4 (LTB4) by omega-oxidation to 20-hydroxyl-LTB4 and 20-carboxy-LTB4. The ability of unstimulated human PMNL to metabolize exogenous LTB4 was found to be inhibited by pyocyanin, a phenazine derivative produced by Pseudomonas aeruginosa, in a dose-dependent manner. 1-Hydroxyphenazine (1-OHP), a metabolite of pyocyanin, was not inhibitory under identical conditions. The initial enzymic step in the conversion of LTB4 is catalyzed by an NADPH-dependent cytochrome, P-450. Reduction of the phenazine derivatives by NADPH was measured spectrophotometrically. Pyocyanin was reduced by NADPH in vitro in a pH-dependent manner, while 1-OHP was poorly or negligibly reduced under similar conditions. Formation of NADP+ was 20.3 +/- 1.8 nmol min-1 for pyocyanin (10 microM) at pH 5.5, compared with 0.6 +/- 0.2 nmol min-1 for 1-OHP (10 microM), while at pH 7.5 a value of 2.2 +/- 1.3 nmol min-1 was obtained for pyocyanin, with no detectable activity for 1-OHP. This indicates that inhibition of LTB4 omega-hydroxylase activity by pyocyanin might be achieved by competition for NADPH. Incorporation of exogenous 5-hydroxyeicosatetraenoic acid by PMNL into lipid pools was not affected by either phenazine derivative. The ability of bacterial pyocyanin to limit the omega-oxidation of LTB4 may have important implications for PMNL LTB4 receptor status and chemotaxis in vivo.  相似文献   
27.
Early time course of the acute phase protein response in man.   总被引:3,自引:3,他引:3       下载免费PDF全文
The rate at which the acute phase protein response occurred after both major and minor surgery was explored. Increases in the plasma concentration of C-reactive protein (CRP), alpha-1-acid glycoprotein (alpha 1 AG) and fibrinogen were not detected until 6-8 h after the initial incision. The peak concentration of CRP occurred at 48 h and that of fibrinogen at 96 h; alpha 1 AG concentrations rose rapidly until 48 h followed by little change until about 120 h. Although there was widespread variation in the concentrations of individual proteins in patients, severity of injury did not seem to have a significant effect on the time course of the change. Plasma cortisol concentration and the total white blood cell count (WBC) reached their peaks before the acute phase proteins, cortisol at 6 h and WBC at 12 h.  相似文献   
28.
29.
30.
Glomerular visceral epithelial cells (GVEC) from normal human glomeruli were grown in tissue culture. Cell surface markers were studied by immunofluorescence microscopy using antibodies against lymphohaemopoietic differentiation antigens which are known to be present early (BA-1, OKB2, BA-2) and late (J5, anti CR1) in renal ontogenesis. Like foetal human glomerular epithelium, the cultured cells reacted with BA-1 and OKB2 (identifying an antigen expressed on B cells and polymorphonuclear leucocytes), and BA-2 (leukaemia-associated antigen), but were consistently negative for CR1 (C3b receptor); J5 which identifies the common acute lymphoblastic leukaemia antigen (CALLA) stained variably. Reactivity with antimyosin or anti factor VIII were absent. The cells produced an extracellular matrix containing laminin, type IV collagen, and fibronectin. This study supports the notion that GVEC undergo dedifferentiation as shown by the acquisition of lymphohaemopoietic differentiation antigens present early in renal ontogeny. In addition, the production of extracellular matrix constituents in vitro may be useful for the investigation of human glomerular basement membranes.  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