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   558651篇
  免费   52033篇
  国内免费   1549篇
  2018年   17347篇
  2017年   16243篇
  2016年   14205篇
  2015年   9139篇
  2014年   10114篇
  2013年   13511篇
  2012年   20608篇
  2011年   30746篇
  2010年   24321篇
  2009年   19769篇
  2008年   25423篇
  2007年   28030篇
  2006年   13921篇
  2005年   14371篇
  2004年   14303篇
  2003年   13676篇
  2002年   12996篇
  2001年   19253篇
  2000年   19136篇
  1999年   15105篇
  1998年   5656篇
  1997年   5669篇
  1996年   5395篇
  1995年   5156篇
  1994年   4863篇
  1993年   4888篇
  1992年   12494篇
  1991年   12491篇
  1990年   12204篇
  1989年   11681篇
  1988年   10849篇
  1987年   10223篇
  1986年   9736篇
  1985年   9501篇
  1984年   7890篇
  1983年   6856篇
  1982年   5150篇
  1981年   4629篇
  1980年   4313篇
  1979年   7349篇
  1978年   5966篇
  1977年   5293篇
  1976年   4964篇
  1975年   5781篇
  1974年   6302篇
  1973年   6124篇
  1972年   6072篇
  1971年   5653篇
  1970年   4281篇
  1969年   4202篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
111.
John L. Graner 《CMAJ》1985,133(9):855-857,880
In 1849 Thomas Addison described the clinical entity now known as pernicious anemia. In 1855 he reported several cases of adrenal insufficiency, or Addison''s disease. Considering the importance of these works, there remains a great deal of confusion about them. Contrary to what many historians have written, a review of Addison''s original publications demonstrates a firm appreciation of the distinction between pernicious anemia and adrenal insufficiency, based particularly on the discoloration of the skin in these conditions. Three major sources of possible confusion for historians who are attempting to understand Addison''s views include Addison''s early attempts to link pernicious anemia with disease of the supra-renal capsules, Addison''s redefinition of pernicious anemia in his monograph on adrenal disease, and several confusing statements made by Wilks and Daldy in the first reprint of Addison''s monograph.  相似文献   
112.
Binomial parameters of transmitter secretion were calculated on the basis of analysis of synaptic potentials in the frog sartorius muscle. Negative values of the parameter p were found in some synapses. This happened most often in low Ca2+ concentrations and with low amplitude of miniature end-plate potentials. The results were interpreted in terms of a model assuming spatial heterogeneity of probability of transmitter quantum release at different release points. Simulation of transmitter secretion by computer showed that the appearance of negative values of the parameter p and incorrect estimates of n experimentally are connected with the form of distribution of probability of transmitter quantum release in the synapse and with the amplitude of miniature potentials.S. V. Kurashov Kazan' Medical Institute, Ministry of Health of the RSFSR. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 182–189, March–April, 1984.  相似文献   
113.
Forty-two white-rot fungi isolated in South America were incubated with long fibre sugar cane bagasse (LFB). The residual composition of LFB was determined after white-rot decay at 30 and 60 days. The ratio of residual lignin to residual lignin to residual cellulose (RL/RC) of untreated material (LFB) was 0.48. After white-rot-decay, the residual material with lower RL/RC ratios indicated that mainly lignin was degraded. In only 30 days, Phlebia sp. MVHC 5535, Athelia sp. MVHC 5509 and Spongipellis pachyodon MVHC 5019 caused a decrease in the RL/RC ratio to 0.36, 0.37 and 0.38, respectively, while it took 60 days for Ganoderma applanatum MVHC 5347, Hyphodontia sp. MVHC 5544, Panus tigrinus MVHC 5400, Stereum sp. MVHC 5113, Phellinus punctatus MVHC 5346 and MVHC 6388 to reach a ratio lower than 0.40. No correlation was found between the amount of some ligninolytic enzymes secreted and the residual composition of bagasse after white-rot fungi fermentation. Most of the fungal strains caused an increase in the relative amount of residual cellulose, indicating that hemicellulose was the preferred energy source.  相似文献   
114.
Extensibility, contractile function and resistance to excess calcium of the right atrium myocardium were studied in normotensive Wistar-Kyoto and August rats and in spontaneously hypertensive rats (SHR). It was shown that long-term stress results in a decrease in the measured parameters in normotensive animals. SHR do not show any stress-induced disturbances. It was discovered that in intact SHR rats, the myocardium has a greater resistance to excess calcium, indirect evidence for higher efficiency of the Ca-pump of the sarcoplasmic reticulum in cardiomyocytes of SHR animals, which is apparently a constituent part of the mechanism of such animals' heart increased resistance to stress-induced damage.  相似文献   
115.
THE TIMING OF DIVISION IN CHLAMYDOMONAS   总被引:3,自引:2,他引:1  
  相似文献   
116.
The neutrophil-stimulating properties of 38 S. aureus strains and 32 S. epidermidis strains were studied in the reaction of luminol-mediated chemiluminescence. All S. aureus strains and 29 S. epidermidis strains were found to possess neutrophil-stimulating activity, the mean activity index for S. aureus being significantly higher. The stimulating activity of the strains varied within a wide range (the variation coefficient was 120.0 +/- 21.9%) and did not correlate with the content of protein A in bacterial cells and the degree of their hydrophoby. The opsonization of staphylococci with normal human serum enhanced the neutrophil reaction 1.5- to 100-fold and simultaneously leveled out the chemiluminescence indices in experiments with different strains (the variation coefficient was 8.0 +/- 1.5%). The nature of the neutrophil-stimulating effect of staphylococci and its relationship to the exploratory reactions of phagocytes are discussed.  相似文献   
117.
118.
119.
120.
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