全文获取类型
收费全文 | 6995篇 |
免费 | 696篇 |
国内免费 | 2篇 |
出版年
2022年 | 44篇 |
2021年 | 121篇 |
2020年 | 69篇 |
2019年 | 74篇 |
2018年 | 90篇 |
2017年 | 65篇 |
2016年 | 140篇 |
2015年 | 283篇 |
2014年 | 281篇 |
2013年 | 427篇 |
2012年 | 510篇 |
2011年 | 470篇 |
2010年 | 288篇 |
2009年 | 227篇 |
2008年 | 397篇 |
2007年 | 408篇 |
2006年 | 344篇 |
2005年 | 305篇 |
2004年 | 296篇 |
2003年 | 301篇 |
2002年 | 306篇 |
2001年 | 94篇 |
2000年 | 72篇 |
1999年 | 86篇 |
1998年 | 104篇 |
1997年 | 62篇 |
1996年 | 59篇 |
1995年 | 48篇 |
1994年 | 62篇 |
1993年 | 51篇 |
1992年 | 56篇 |
1991年 | 48篇 |
1990年 | 58篇 |
1989年 | 57篇 |
1988年 | 53篇 |
1987年 | 41篇 |
1986年 | 50篇 |
1985年 | 68篇 |
1984年 | 57篇 |
1983年 | 70篇 |
1982年 | 67篇 |
1981年 | 57篇 |
1980年 | 47篇 |
1979年 | 41篇 |
1976年 | 47篇 |
1975年 | 47篇 |
1974年 | 45篇 |
1973年 | 44篇 |
1971年 | 40篇 |
1969年 | 42篇 |
排序方式: 共有7693条查询结果,搜索用时 78 毫秒
1.
Transcriptive expression during sea urchin embryogenesis 总被引:2,自引:0,他引:2
2.
3.
Cysteine-proteinase activity was observed in homogenates of human-cadaver renal cortex. This activity co-purified with renin enzymic activity until separation by aminohexyl-Sepharose--pepstatin affinity chromatography. The cysteine proteinase was purified 1780-fold after the following successive chromatographic procedures: Sephadex G-75, DEAE-cellulose DE-52, and an organomercurial affinity resin. The proteinase activity was dependent upon activation by thiol-containing compounds such as dithiothreitol, as well as by EDTA, and was inhibited by the thiol-group-specific alkylating reagents iodoacetic acid and N-ethylmaleimide. DE-52 cellulose chromatography resolved the cysteine proteinase into two components. On the basis of molecular size (26 000 daltons), activity as a function of pH, stability as a function of pH, substrate specificity and thermal lability, the major component (95%) has been identified as cathepsin B. The DE-52 cellulose elution pattern of the minor component (5%) is suggestive of cathepsin H [Schwartz & Barrett (1980) Biochem. J. 191, 487-497] Enzymic activity was determined with synthetic substrates, in particular alpha-N-benzoyl-DL-arginine 2-naphthylamide (Bz-Arg-NNap), thus precluding the detection of cathepsin L [Kirschke, Langner, Wiederanders, Ansorge, Bohley & Broghammer (1976) Acta Biol. Med. Germ. 35, 285-299]. Inhibition by dimethyl sulphoxide was observed in the determination of Km = 7.0 +/- 0.4 mM for the substrate Bz-Arg-NNap, and care must therefore be taken in the preparation of substrate solutions. 相似文献
4.
5.
6.
Effect of sulphydryl-combining compounds on the activity of the succinic oxidase system 总被引:4,自引:2,他引:2
下载免费PDF全文
![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Slater EC 《The Biochemical journal》1949,45(2):130-142
7.
Jin Wei Mia Madel Alfajaro Peter C. DeWeirdt Ruth E. Hanna William J. Lu-Culligan Wesley L. Cai Madison S. Strine Shang-Min Zhang Vincent R. Graziano Cameron O. Schmitz Jennifer S. Chen Madeleine C. Mankowski Renata B. Filler Neal G. Ravindra Victor Gasque Fernando J. de Miguel Ajinkya Patil Huacui Chen Craig B. Wilen 《Cell》2021,184(1):76-91.e13
- Download : Download high-res image (212KB)
- Download : Download full-size image
8.
9.
Ruth C. Paul B. Rainey Brian J. Sheehan Orla M. Keane Charles J. Dorman 《Current biology : CB》1999,9(24)
The relationship between environment and mutation is complex [1]. Claims of Lamarkian mutation [2] have proved unfounded [3], [4] and [5]; it is apparent, however, that the external environment can influence the generation of heritable variation, through either direct effects on DNA sequence [6] or DNA maintenance and copying mechanisms [7], [8], [9] and [10], or as a consequence of evolutionary processes [11], [12], [13], [14], [15] and [16]. The spectrum of mutational events subject to environmental influence is unknown [6] and precisely how environmental signals modulate mutation is unclear. Evidence from bacteria suggests that a transient recombination-dependent hypermutational state can be induced by starvation [5]. It is also apparent that chnages in the mutability of specific loci can be influenced by alterations in DNA topology [10] and [17]. Here we describe a remarkable instance of adaptive evolution in Salmonella which is caused by a mutation that occurs in intermediate-strength osmotic environments. We show that the mutation is not ‘directed’ and describe its genetic basis. We also present compelling evidence in support of the hypothesis that the mutational event is constrained by signals transmitted from the external environment via changes in the activity of DNA gyrase. 相似文献
10.