全文获取类型
收费全文 | 6962篇 |
免费 | 777篇 |
国内免费 | 4篇 |
专业分类
7743篇 |
出版年
2021年 | 62篇 |
2018年 | 61篇 |
2017年 | 51篇 |
2016年 | 104篇 |
2015年 | 167篇 |
2014年 | 189篇 |
2013年 | 254篇 |
2012年 | 323篇 |
2011年 | 357篇 |
2010年 | 238篇 |
2009年 | 208篇 |
2008年 | 333篇 |
2007年 | 315篇 |
2006年 | 319篇 |
2005年 | 307篇 |
2004年 | 354篇 |
2003年 | 308篇 |
2002年 | 303篇 |
2001年 | 95篇 |
2000年 | 106篇 |
1999年 | 139篇 |
1998年 | 122篇 |
1997年 | 71篇 |
1996年 | 67篇 |
1995年 | 80篇 |
1994年 | 72篇 |
1993年 | 71篇 |
1992年 | 108篇 |
1991年 | 99篇 |
1990年 | 101篇 |
1989年 | 93篇 |
1988年 | 77篇 |
1987年 | 80篇 |
1986年 | 84篇 |
1985年 | 89篇 |
1984年 | 78篇 |
1983年 | 77篇 |
1982年 | 92篇 |
1981年 | 79篇 |
1980年 | 89篇 |
1979年 | 81篇 |
1978年 | 68篇 |
1977年 | 86篇 |
1976年 | 73篇 |
1975年 | 66篇 |
1974年 | 92篇 |
1973年 | 82篇 |
1972年 | 49篇 |
1969年 | 55篇 |
1968年 | 47篇 |
排序方式: 共有7743条查询结果,搜索用时 0 毫秒
101.
A mass-spectrometric sequence study of the enzyme ribitol dehydrogenase from Klebsiella aerogenes 总被引:10,自引:6,他引:4
Howard R. Morris Dudley H. Williams Graeme G. Midwinter Brian S. Hartley 《The Biochemical journal》1974,141(3):701-713
The first detailed results of the application of a low-resolution mixture analysis approach to the sequence analysis of an enzyme, ribitol dehydrogenase, are given. Examples of the interpretation of the spectra of peptide mixtures derived from this protein are described. Evidence for new fragmentation patterns observed is reported, together with an explanation of the generation of ambiguous sequences by use of a low-specificity enzyme, thermolysin. The overall sequencing strategy evolved is assessed. 相似文献
102.
Howard R. Morris Karen E. Batley Nigel G. L. Harding Richard A. Bjur John G. Dann Rodney W. King 《The Biochemical journal》1974,137(2):409-411
An elastase digest of a protein of unknown structure, dihydrofolate reductase, was studied by mass spectrometry. This soluble digest contained a large number of small peptides in different yields, within the ideal molecular-weight range (200-1200) for mixture-analysis mass spectrometry. Sequences of the major component peptides in the digest are reported. 相似文献
103.
Fluorescence microscopy of Douglas fir foliage epiflora 总被引:2,自引:0,他引:2
104.
105.
A cytological and cytochemical examination of Saprolegnia terrestris Cookson was undertaken to resolve the conflict of opinion regarding the life cycle of fungi in the Saprolegniaceae, i.e., whether meiosis is zygotic or gametic. Microspectrophotometric analysis reveals that pre-divisional oogonial and antheridial nuclei are 4C; a subsequent reduction division in the sex organs produces 1C male and female gametes. These division products coexist in the developing oospore and presumably fuse to produce the diploid zygote. Analysis of the somatic hyphal nuclei shows a 2C DNA content, with the characteristic skew and bimodal character indicative of predominantly G1, and some S-period and G2 types. The evidence is completely consistent with gametic meiosis, i.e., a predominant diploid vegetative phase and short haploid phase, and refutes the notion of zygotic meiosis. Further ramifications of the work are discussed along with preliminary results of related work in progress. 相似文献
106.
107.
Papaya lysozyme. Terminal sequences and enzymatic properties 总被引:4,自引:0,他引:4
108.
109.
110.
Origin of the Thymidine Kinase Induced by Polyoma Virus in Productively Infected Cells 总被引:13,自引:4,他引:9 下载免费PDF全文
Cells of the 3T3 mouse line efficiently supported the multiplication of polyoma virus, and the infectious process was accompanied by a marked increase in thymidine kinase (TK) activity. Two lines of 5-bromodeoxyuridine-resistant 3T3 cells have been isolated. As expected, these cells incorporated practically no exogenous thymidine into their deoxyribonucleic acid (DNA) and contained negligible TK activity. Like the parental 3T3 cells, TK(-) lines were susceptible to productive infection by polyoma virus, but infection did not lead to an increase in TK activity. Since kinase activity did appear after infection with another virus (vaccinia) known to contain the gene(s) for that enzyme, it is concluded that TK is not one of the gene products of polyoma virus. As induction of cellular DNA synthesis by polyoma virus occurs normally when the TK(-) cells are infected in the stationary phase, TK cannot play a role in the determination of this phenomenon. 相似文献