全文获取类型
收费全文 | 77776篇 |
免费 | 5290篇 |
国内免费 | 3470篇 |
出版年
2024年 | 172篇 |
2023年 | 1182篇 |
2022年 | 1881篇 |
2021年 | 2411篇 |
2020年 | 2279篇 |
2019年 | 2578篇 |
2018年 | 2582篇 |
2017年 | 1852篇 |
2016年 | 1856篇 |
2015年 | 2366篇 |
2014年 | 4473篇 |
2013年 | 5785篇 |
2012年 | 3373篇 |
2011年 | 4547篇 |
2010年 | 3495篇 |
2009年 | 3943篇 |
2008年 | 4050篇 |
2007年 | 4131篇 |
2006年 | 3651篇 |
2005年 | 3315篇 |
2004年 | 2944篇 |
2003年 | 2508篇 |
2002年 | 2192篇 |
2001年 | 1539篇 |
2000年 | 1283篇 |
1999年 | 1375篇 |
1998年 | 1255篇 |
1997年 | 1101篇 |
1996年 | 1041篇 |
1995年 | 968篇 |
1994年 | 906篇 |
1993年 | 797篇 |
1992年 | 722篇 |
1991年 | 670篇 |
1990年 | 534篇 |
1989年 | 518篇 |
1988年 | 455篇 |
1987年 | 442篇 |
1986年 | 395篇 |
1985年 | 541篇 |
1984年 | 752篇 |
1983年 | 555篇 |
1982年 | 625篇 |
1981年 | 447篇 |
1980年 | 444篇 |
1979年 | 373篇 |
1978年 | 287篇 |
1977年 | 222篇 |
1976年 | 192篇 |
1975年 | 152篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
63.
《Developmental cell》2022,57(18):2221-2236.e5
- Download : Download high-res image (185KB)
- Download : Download full-size image
64.
The distribution of vitamin K epoxidase activity in rough and smooth microsomes has been studied and compared to the prothrombin precursor and vitamin K-dependent carboxylase activity. All three activities were high in rough microsomes as compared to the low levels found in smooth microsomes. The results are in agreement with the suggestion that there might be a linkage between the vitamin K-dependent carboxylation and epoxidation reaction in vivo. 相似文献
65.
《Bioscience, biotechnology, and biochemistry》2013,77(10):1763-1765
We previously isolated a Serratia marcescens O5: HI Z-54 strain which produces a new reddish-violet pigment, a peptide- ferropyrimine complex. This study showed that polymyxin B enhances the formation of the pigment about threefold. This occurs because polymyxin B in the medium causes the formation of an iron-polymyxin B complex which imposes a low iron stress on the bacteria and, in turn, enhances pigment production. This shows that polymyxin B is both a membrane-disrupting and ionophoric antibiotic. 相似文献
66.
《Cell reports》2020,30(6):1835-1847.e9
- Download : Download high-res image (127KB)
- Download : Download full-size image
67.
Harry Le Vine Pedro Cuatrecasas 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,672(3):248-261
A cytosolic, macromolecular factor required for the cholera toxin-dependent activation of pigeon erythrocyte adenylate cyclase and cholera toxin-dependent ADP-ribosylation of a membrane-bound 43 000 dalton polypeptide has been purified 1100-fold from horse erythrocyte cytosol using organic solvent precipitation and heat treatment. This factor, 13 000 daltons, does not absorb to anionic or cationic exchange resins, is sensitive to trypsin or 10% trichloroacetic acid and is not extractable by diethyl ether. Activation of adenylate cyclase by cholera toxin requires the simultaneous presence of ATP (including possible trace GTP), NAD+, dithiothreitol, cholera toxin, membranes and the cytosolic macromolecular factor. Reversal of cholera toxin activation of adenylate cyclase, and of the toxin-dependent ADP-ribosylation, requires the presence of the cytosolic factor. The ability of the purified cytosolic factor to influence the hormonal sensitivity of liver membrane adenylate cyclase may provide clues to its physiological functions. 相似文献
68.
69.
Low rates of iridoid glycoside hydrolysis in two Longitarsus leaf beetles with different feeding specialization confer tolerance to iridoid glycoside containing host plants
下载免费PDF全文
![点击此处可从《Physiological Entomology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Susanne Dobler 《Physiological Entomology》2015,40(1):18-29
Iridoid glycosides are plant defence compounds that are deterrent and/or toxic for unadapted herbivores but are readily sequestered by dietary specialists of different insect orders. Hydrolysis of iridoid glycosides by β‐glucosidase leads to protein denaturation. Insect digestive β‐glucosidases thus have the potential to mediate plant–insect interactions. In the present study, mechanisms associated with iridoid glycoside tolerance are investigated in two closely‐related leaf beetle species (Coleoptera: Chrysomelidae) that feed on iridoid glycoside containing host plants. The polyphagous Longitarsus luridus Scopoli does not sequester iridoid glycosides, whereas the specialist Longitarsus tabidus Fabricius sequesters these compounds from its host plants. To study whether the biochemical properties of their β‐glucosidases correspond to the differences in feeding specialization, the number of β‐glucosidase isoforms and their kinetic properties are compared between the two beetle species. To examine the impact of iridoid glycosides on the β‐glucosidase activity of the generalist, L. luridus beetles are kept on host plants with or without iridoid glycosides. Furthermore, β‐glucosidase activities of both species are examined using an artificial β‐glucosidase substrate and the iridoid glycoside aucubin present in their host plants. Both species have one or two β‐glucosidases with different substrate affinities. Interestingly, host plant use does not influence the specific β‐glucosidase activities of the generalist. Both species hydrolyse aucubin with a much lower affinity than the standard substrate. The neutral pH reduces the β‐glucosidase activity of the specialist beetles by approximately 60% relative to its pH optimum. These low rates of aucubin hydrolysis suggest that the ability to sequester iridoid glycosides has evolved as a key to potentially preventing iridoid glycoside hydrolysis by plant‐derived β‐glucosidases. 相似文献
70.
Andrew Leask 《Journal of cell communication and signaling》2010,4(1):73-74
Connective tissue growth factor (CTGF/CCN2) is overexpressed in diabetes. Diabetic rats possess myocardial and cardiomyocyte hypertrophy. In a recent report, Wang and colleagues (Am J Physiol Cell Physiol. 2009 Jul 22. [Epub ahead of print]) show that CCN2 directly mediates cardiomyocyte hypertrophy as well as that induced by high glucose and fatty acid. CCN2 acted via the TrkA receptor. These data are the subject of this commentary, and emphasize that CCN2 may be an excellent target for therapy in diabetes. 相似文献