全文获取类型
收费全文 | 33408篇 |
免费 | 2877篇 |
国内免费 | 120篇 |
专业分类
36405篇 |
出版年
2021年 | 439篇 |
2020年 | 284篇 |
2019年 | 431篇 |
2018年 | 503篇 |
2017年 | 410篇 |
2016年 | 641篇 |
2015年 | 1024篇 |
2014年 | 1140篇 |
2013年 | 1610篇 |
2012年 | 1786篇 |
2011年 | 1682篇 |
2010年 | 1241篇 |
2009年 | 983篇 |
2008年 | 1465篇 |
2007年 | 1405篇 |
2006年 | 1373篇 |
2005年 | 1210篇 |
2004年 | 1269篇 |
2003年 | 1210篇 |
2002年 | 1255篇 |
2001年 | 1078篇 |
2000年 | 978篇 |
1999年 | 898篇 |
1998年 | 459篇 |
1997年 | 432篇 |
1996年 | 356篇 |
1995年 | 345篇 |
1994年 | 279篇 |
1993年 | 331篇 |
1992年 | 602篇 |
1991年 | 590篇 |
1990年 | 548篇 |
1989年 | 473篇 |
1988年 | 421篇 |
1987年 | 386篇 |
1986年 | 372篇 |
1985年 | 439篇 |
1984年 | 403篇 |
1983年 | 352篇 |
1982年 | 274篇 |
1981年 | 274篇 |
1980年 | 251篇 |
1979年 | 312篇 |
1978年 | 267篇 |
1977年 | 308篇 |
1976年 | 290篇 |
1975年 | 283篇 |
1974年 | 290篇 |
1973年 | 260篇 |
1972年 | 235篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
111.
112.
Identification of neurophysin producing cells 总被引:2,自引:0,他引:2
113.
114.
Cyclophosphamide, given in widely spaced doses, was used in the treatment of a patient with pemphigus vulgaris and a patient with bullous pemphigoid. To our knowledge, this form of therapy has not previously been reported in these two diseases. The distinct advantages of the larger intermittent dose method of cyclophosphamide therapy over the more conventional daily dose regimen are discussed. 相似文献
115.
C De Lisi 《Biopolymers》1973,12(8):1713-1728
We report the results of semi-empirical calculations describing thermodynamic properties of transfer RNA conformations. The most important new features of the procedure are: (1) the use of parameters obtained from model oligoribonucleotides to evaluate the free energy of helical regions and small hairpin loops, and (2) the use of a model which is somewhat more realistic than the freely jointed chain for evaluating internal loops and intermediate size hairpin loops. The new parameters lead to important quantitative and qualitative differences from predictions which would have been made in the past and lead to a priori predictions of tRNA melting temperatures which are within about 6°C of the experimental values. The results suggest the following conclusions: (1) The early melting transition observed in several tRNA's is partly the result of tertiary unfolding, and partly the result of the loss of some secondary structure. (2) The part of the secondary structure which melts during the early transition is different for different tRNA's. For fMet and Tyr from E. coli, the calculations predict that the dihydrouradiene arm melts out early. For yeast Phe the acceptor stem and anticodon helix melt first. (3) The results also suggest the possibility that tertiary unfolding and early secondary structural melting do not occur independently but are coupled, so that the two types of structure are probably mutually stabilizing. 相似文献
116.
Oxidative metabolism of carbon disulphide by the rat. Effect of treatments which modify the liver toxicity of carbon disulphide 总被引:1,自引:0,他引:1
The liver toxicity of a standard dose of CS2 was increased by phenobarbitone pre-treatment and by fasting and decreased by prior administration of a small dose of CS2; it was less marked in female than in male rats.Rats were given an intraperitoneal dose of 14CS2 to study its in vivo conversion to 14CO2 under conditions which modify the liver toxicity of CS2. The radioactive CO2 exhaled was found to be linearly related to the amount of cytochrome P-450 present in the liver at the time of administering 14CS2; it was also found to be related to the severity of the toxic changes caused in the liver, but here the relationship was not linear and was more complex.When liver microsomes were incubated with CS2, a marked loss of cytochrome P-450 was observed only when NADPH was present. In contrast with the loss of the cytochrome observed with NADPH alone, which is associated with the formation of malonaldehyde, that due to CS2 still occurred in the presence of EDTA, even though the formation of malonaldehyde was largely prevented.These results are compatible with the hypothesis that CS2 requires metabolism for its liver toxicity. 相似文献
117.
118.
119.
120.