全文获取类型
收费全文 | 62197篇 |
免费 | 4641篇 |
国内免费 | 3184篇 |
出版年
2024年 | 38篇 |
2023年 | 698篇 |
2022年 | 854篇 |
2021年 | 1360篇 |
2020年 | 1410篇 |
2019年 | 1868篇 |
2018年 | 1864篇 |
2017年 | 1290篇 |
2016年 | 1520篇 |
2015年 | 2140篇 |
2014年 | 3223篇 |
2013年 | 4368篇 |
2012年 | 2302篇 |
2011年 | 3303篇 |
2010年 | 2624篇 |
2009年 | 3323篇 |
2008年 | 3537篇 |
2007年 | 3637篇 |
2006年 | 3355篇 |
2005年 | 3252篇 |
2004年 | 2882篇 |
2003年 | 2580篇 |
2002年 | 2332篇 |
2001年 | 1540篇 |
2000年 | 1311篇 |
1999年 | 1375篇 |
1998年 | 1292篇 |
1997年 | 1033篇 |
1996年 | 857篇 |
1995年 | 1097篇 |
1994年 | 1018篇 |
1993年 | 872篇 |
1992年 | 771篇 |
1991年 | 567篇 |
1990年 | 467篇 |
1989年 | 421篇 |
1988年 | 431篇 |
1987年 | 380篇 |
1986年 | 306篇 |
1985年 | 382篇 |
1984年 | 522篇 |
1983年 | 359篇 |
1982年 | 352篇 |
1981年 | 220篇 |
1980年 | 205篇 |
1979年 | 165篇 |
1978年 | 96篇 |
1977年 | 58篇 |
1976年 | 52篇 |
1975年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Mark P.G. van der Linden Janet Vonck Klaas A. Sjollema Wolfgang Keck 《FEMS microbiology letters》1992,99(2-3):117-123
Accumulation of either native membrane-bound or soluble variants of PBP5 over-expressed in the cytoplasm was investigated by electron microscopy of ultra-thin sections. One of the soluble forms of PBP5 (PBP5s353) formed well-ordered crystals inside the cells. Cells sectioned perpendicular to their long axis showed a diamond-shaped crystal whereas cells cut parallel to their long axis contained a long, narrow crystal. In both sectioning directions an ordered ultrastructure was visible as shown by optical diffraction. Computer processing was used to enhance the crystal images. From this the unit cell parameters were calculated as a = 7.6 nm, b = 4 nm, c = 4.2 nm, gamma = 75 degrees. The calculated unit-cell volume of 120 nm3 is large enough to contain one protein molecule. 相似文献
32.
《Current biology : CB》2020,30(13):2433-2445.e3
Media player
33.
35.
36.
Joshua Seaberg Nicholas Flynn Amanda Cai Joshua D. Ramsey 《Biotechnology and bioengineering》2020,117(8):2504-2515
Therapeutic proteins are utilized in a variety of clinical applications, but side effects and rapid in vivo clearance still present hurdles. An approach that addresses both drawbacks is protein encapsulation within in a polymeric nanoparticle, which is effective but introduces the additional challenge of destabilizing the nanoparticle shell in clinically relevant locations. This study examined the effects of crosslinking self-assembled poly(l -lysine)-grafted-poly(ethylene glycol) nanoparticles with redox-responsive 3,3′-dithiobis(sulfosuccinimidyl propionate) (DTSSP) to achieve nanoparticle destabilization in a reductive environment. The polymer-protein nanoparticles (DTSSP NPs) were formed through electrostatic self-assembly and crosslinked with DTSSP, which contains a glutathione-reducible disulfide. As glutathione is upregulated in various cancers, DTSSP NPs could display destabilization within cancer cells. A library of DTSSP NPs was formed with varying copolymer to protein (C:P) and crosslinker to protein (X:P) mass ratios and characterized by size and encapsulation efficiency. DTSSP NPs with a 7:1 C:P ratio and 2:1 X:P ratio were further characterized by stability in the presence proteases and reducing agents. DTSSP NPs fully encapsulated the model protein and displayed 81% protein release when incubated with 5 mM dithiothreitol for 12 hr. This study contributes to understanding stimulus-responsive crosslinking of polymeric nanoparticles and could be foundational to clinical administration of therapeutic proteins. 相似文献
37.
38.
《Current biology : CB》2020,30(11):2166-2174.e3
39.
40.