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   362380篇
  免费   36891篇
  国内免费   283篇
  2018年   3421篇
  2016年   4606篇
  2015年   5859篇
  2014年   6756篇
  2013年   10101篇
  2012年   10810篇
  2011年   11239篇
  2010年   7694篇
  2009年   6942篇
  2008年   10095篇
  2007年   10162篇
  2006年   9674篇
  2005年   9218篇
  2004年   9110篇
  2003年   8830篇
  2002年   8480篇
  2001年   15534篇
  2000年   15358篇
  1999年   12070篇
  1998年   4306篇
  1997年   4514篇
  1996年   4297篇
  1995年   3850篇
  1994年   3799篇
  1993年   3831篇
  1992年   9984篇
  1991年   9991篇
  1990年   9695篇
  1989年   9414篇
  1988年   8696篇
  1987年   8353篇
  1986年   7629篇
  1985年   7833篇
  1984年   6467篇
  1983年   5489篇
  1982年   4217篇
  1981年   3939篇
  1980年   3640篇
  1979年   6255篇
  1978年   4830篇
  1977年   4629篇
  1976年   4309篇
  1975年   4837篇
  1974年   5307篇
  1973年   5283篇
  1972年   4741篇
  1971年   4376篇
  1970年   3901篇
  1969年   3857篇
  1968年   3519篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
E Dux  I Tóth  L Dux  F Joó 《Histochemistry》1978,56(3-4):239-244
An electron histochemical study was undertaken to localize calcium with ammonium oxalate precipitation technique in soleus muscle of rat in normal cases and in myopathy induced experimentally by a prolonged treatment of 2,4-dichlorophenoxyacetate (2,4-D). The calcium content of precipitates was detected by energy-dispersive X-ray microanalysis. In normal cases, the electron dense precipitates containing calcium were mainly found in the vesicles of sarcoplasmic reticulum, whereas in 2,4-D induced myopathy the deposits were shifted near the Z line into the myofibrils. Calcium, because the uptake into sarcoplasmic vesicles was inhibited by 2,4-D, could attach to other binding sites, such as to the troponin-C.A long-lasting binding of calcium might lead to a prolonged activation of the actin-myosin system.  相似文献   
992.
After 30 years of continuous research into the mechanisms of human hypertension, we summarize the results obtained by the members of the multidisciplinary research group on hypertension of the Clinical Research Institute of Montreal on the disturbances of minerlocorticoid activity in a rigorously selected group of patients with early, mild essential hypertension. We attempt to integrate these findings with those of many other groups working on other aspects of hypertensive cardiovascular diseases. On the assumption that the increased peripheral resistance responsible for hypertension results from an imbalance or a disturbance of the equilibrium between the sympathetic nervous system and norepinephrine on one hand, and the vascular tone, sensitivity and responsiveness of the arterial smooth muscle to norepinephrine and to angiotensin II on the other hand, three models that fit the experimental and clinical facts as known at present are described.  相似文献   
993.
994.
995.
996.
Retroviral infections are accompanied by immunosuppression in a variety of species. For feline leukemia virus, the immunosuppression has been ascribed to the transmembrane envelope protein, p15E, which suppresses the proliferative responses of cat, mouse, and human lymphocytes. A similar suppressive effect has been shown for a lysate of human immunodeficiency virus (HIV), strain HTLV-IIIB. Here we determined that detergent-disrupted HTLV-IIIB lystate exerted a strong suppressive effect on PHA-stimulated lymphocytes. Preparations of whole virions, a lysate of a local HIV isolate grown on MP-6 cells, and a commercially obtained UV and psoralene-inactivated lysate were examined and demonstrated to have a similar suppressive effect. The HIV lysate was not directly cytotoxic to lymphocytes and did not contain tumor necrosis factor or lymphotoxin. The HIV lysate specifically suppressed the proliferation of a range of hemopoietic cell lines from man and mouse including three EBV transformed CD4- and IL-2 receptor-negative B-cell lines. The lysate also suppressed the formation of human bone marrow colonies, whereas the lysate had only a slight or no effect on fibroblasts. The suppression of lymphocyte proliferation was not abrogated by addition of IL-2 or IL-1 and the HIV lysate inhibited the expression of IL-2 receptors on suboptimal PHA-stimulated mononuclear cells. The suppressive factor(s) has not been characterized in molecular terms, but suppressive activity was recovered in fractions with a molecular weight of about 67,000 and in both the glycoprotein fraction and in the glycoprotein-depleted fraction of the HIV lysate. Sera from one-third of a small series (N = 13) of individuals with antibodies to HIV seem to be able to neutralize the suppressive properties of HIV lysate in cultures.  相似文献   
997.
998.
999.
1000.
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