全文获取类型
收费全文 | 52088篇 |
免费 | 4697篇 |
国内免费 | 2482篇 |
出版年
2023年 | 449篇 |
2022年 | 563篇 |
2021年 | 2062篇 |
2020年 | 1338篇 |
2019年 | 1655篇 |
2018年 | 1598篇 |
2017年 | 1262篇 |
2016年 | 1873篇 |
2015年 | 2760篇 |
2014年 | 3234篇 |
2013年 | 3515篇 |
2012年 | 4110篇 |
2011年 | 3895篇 |
2010年 | 2286篇 |
2009年 | 2139篇 |
2008年 | 2523篇 |
2007年 | 2290篇 |
2006年 | 1956篇 |
2005年 | 1751篇 |
2004年 | 1513篇 |
2003年 | 1344篇 |
2002年 | 1169篇 |
2001年 | 1917篇 |
2000年 | 1658篇 |
1999年 | 1387篇 |
1998年 | 636篇 |
1997年 | 677篇 |
1996年 | 606篇 |
1995年 | 530篇 |
1994年 | 523篇 |
1993年 | 409篇 |
1992年 | 793篇 |
1991年 | 686篇 |
1990年 | 607篇 |
1989年 | 455篇 |
1988年 | 424篇 |
1987年 | 320篇 |
1986年 | 283篇 |
1985年 | 293篇 |
1984年 | 182篇 |
1983年 | 166篇 |
1982年 | 107篇 |
1981年 | 88篇 |
1980年 | 76篇 |
1979年 | 110篇 |
1978年 | 95篇 |
1976年 | 85篇 |
1975年 | 75篇 |
1973年 | 87篇 |
1972年 | 79篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
31.
Adenylate kinase (AKe) from E. coli is a small, single-chain, monomeric enzyme with no tryptophan and a single cysteine residue. We have constructed six single-Trp mutants of AKe to facilitate optical studies of these proteins and to specifically examine the interrelationship between their structure, function, dynamics, and folding reactions. In this study, the effects of hydrostatic pressure on the folding reactions of AKe were studied. The native structure of AKe was transformed to a non-native, yet pressure stable, conformation by hydrostatic pressure of about 300 MPa. This pressure lability of AKe is rather low for a monomeric protein and presumably may be attributed to substantial conformational flexibility and a correspondingly large volume change. The refolding of AKe after pressure-induced denaturation was reversible under ambient conditions. At low temperature (near 0 degrees C), the refolding process of pressure-exposed AKe mutants displayed a significant hysteresis. The observation of a slow refolding rate in the 193 region and a faster folding rate around the active site (86, 41, 73 regions) leads us to suggest that in the folding process, priority is afforded to functional regions. The slow structural return of the 193 region apparently does not hinder the more rapid return of enzymatic activity of AKe. Circular dichroism studies on the pressure-denatured Y193W mutant show that the secondary structure (calculated from far-UV spectra) returned at a rapid rate, but the tertiary structure alignment (calculated from near-UV spectra) around the 193 region occurred more slowly at rates comparable to those detected by fluorescence intensity. Denaturation of AKe mutants by guanidine hydrochloride and subsequent refolding experiments were also consistent with a much slower refolding process around the 193 region than near the active site. Fast refolding kinetic traces were observed in F86W, S41W, and A73W mutants using a fluorescence detection stopped-flow rapid mixing device, while only a slow kinetic trace was observed for Y193W. The results suggest that the differences in regional folding rates of AKe are not derived from the specific denaturation methods, but rather are inherent in the structural organization of the protein. 相似文献
32.
33.
34.
Ahmed Imrul Mosaddek Nadira Umme Aktari Cao Fangbin He Xiaoyan Zhang Guoping Wu Feibo 《Planta》2016,243(4):973-985
Planta - The drought-stimulated gene expression of NCED, SUS, and KS - DHN and ABA signal cross-talk with other phytohormones maintains barley root growth under drought stress at pH 4.0 plus... 相似文献
35.
<正>Structural variations (SVs) are mutations with large-scale changes (generally50 bp) in the genome. SVs are major sources of the genetic diversity of organisms and thus are of high relevance to phenotype variations, gene dosage and evolutionary genetics. Except detecting SVs through comparative genetic analyses, dozens of software had been developed based on the alignment of short-reads to a single linear genome in the past decades (Guan and Sung, 2016). 相似文献
36.
37.
The family of flaviviruses is one of the most medically important groups of emerging arthropod-borne viruses. Host cell cytoskeletons have been reported to have close contact with flaviviruses during virus entry, intracellular transport, replication, and egress process, although many detailed mechanisms are still unclear. This article provides a brief overview of the function of the most prominent flaviviruses-induced or-hijacked cytoskeletal structures including actin, microtubules and intermediate filaments, mainly focus on infection by dengue virus, Zika virus and West Nile virus. We suggest that virus interaction with host cytoskeleton to be an interesting area of future research. 相似文献
38.
Yan Xue Liu Jia Wu Ke-Xin Yang Nan Pan Li-Ben Song Ying Liu Yang Tang Zhong-Hua 《Journal of Plant Growth Regulation》2022,41(6):2421-2434
Journal of Plant Growth Regulation - Early-spring plants are a special type of plant that complete their life cycle promptly in cold, early spring. Very little effort has been made into researching... 相似文献
39.
Binding of B‐cell maturation antigen to B‐cell activating factor induces survival of multiple myeloma cells by activating Akt and JNK signaling pathways 下载免费PDF全文
Xianjuan Shen Yuehua Guo Jing Qi Wei Shi Xinhua Wu Shaoqing Ju 《Cell biochemistry and function》2016,34(2):104-110
B‐cell maturation antigen (BCMA) is expressed on normal and malignant plasma cells and represents a potential target for therapeutic intervention. In this study, we characterized the mechanism underlying the protein kinase B (Akt) and c‐Jun N‐terminal kinase (JNK) pathways and BCMA interactions in regulating multiple myeloma (MM) cell survival. It was found that the expression levels of B cell‐activating factor (BAFF) and BCMA were increased in MM cells as compared with those in normal controls. The proliferation of U266 cells was induced by recombinant human BAFF (rhBAFF) and could also be decreased by BCMA siRNA. The expression of Bcl‐2 protein was up‐regulated, and Bax protein was down‐regulated after rhBAFF treatment, which could be reversed by BCMA siRNA. Similarly, the protein p‐JNK and p‐Akt were activated by rhBAFF and could be changed by BCMA siRNA. In addition, the BCMA mRNA and protein expression levels were decreased after treatment with Akt and JNK pathway inhibitors. These results suggest that Akt and JNK pathways are involved in the regulation of BCMA. A novel BAFF/BCMA signalling pathway in MM may be a new therapeutic target for MM. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献