全文获取类型
收费全文 | 491558篇 |
免费 | 54679篇 |
国内免费 | 775篇 |
专业分类
547012篇 |
出版年
2018年 | 4855篇 |
2017年 | 4716篇 |
2016年 | 6805篇 |
2015年 | 9912篇 |
2014年 | 11398篇 |
2013年 | 15261篇 |
2012年 | 18137篇 |
2011年 | 18446篇 |
2010年 | 12062篇 |
2009年 | 10721篇 |
2008年 | 16076篇 |
2007年 | 16544篇 |
2006年 | 15610篇 |
2005年 | 14882篇 |
2004年 | 14858篇 |
2003年 | 13877篇 |
2002年 | 13539篇 |
2001年 | 20147篇 |
2000年 | 20186篇 |
1999年 | 16134篇 |
1998年 | 6033篇 |
1997年 | 5973篇 |
1996年 | 5687篇 |
1995年 | 5452篇 |
1994年 | 5158篇 |
1993年 | 5151篇 |
1992年 | 13132篇 |
1991年 | 13055篇 |
1990年 | 12803篇 |
1989年 | 12245篇 |
1988年 | 11402篇 |
1987年 | 10679篇 |
1986年 | 10211篇 |
1985年 | 9949篇 |
1984年 | 8282篇 |
1983年 | 7211篇 |
1982年 | 5478篇 |
1981年 | 4954篇 |
1980年 | 4566篇 |
1979年 | 7776篇 |
1978年 | 6299篇 |
1977年 | 5556篇 |
1976年 | 5185篇 |
1975年 | 6085篇 |
1974年 | 6594篇 |
1973年 | 6409篇 |
1972年 | 5771篇 |
1971年 | 5355篇 |
1970年 | 4500篇 |
1969年 | 4452篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
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
82.
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
83.
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
84.
L S Katkova 《Biulleten' eksperimental'no? biologii i meditsiny》1985,99(4):413-415
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
85.
THE TIMING OF DIVISION IN CHLAMYDOMONAS 总被引:3,自引:2,他引:1
86.
A L Nevmiatullin O N Vorob'eva A N Maianski? 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1985,(7):67-71
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
87.
88.
89.
Samples of marine pleuston were collected from the sea-surface along considerable sections of the track of Eye of the Wind during its 2-year circumnavigational expedition 'Operation Drake' from November 1978 to October 1980. One hundred and eleven of the tow samples contained insects of the genus Halobates . They were assigned to four oceanic species: H. micans, H. sericeus, H. germanus and H. splendens; two coastal species: H. maculatus, H. princeps, and one undescribed species. Various development stages of the oceanic species were found. The locations, time of collection and surface temperatures where sea-skaters were collected are tabulated. Distributional boundaries and population densities of the oceanic species collected are discussed. 相似文献
90.