全文获取类型
收费全文 | 5831篇 |
免费 | 592篇 |
出版年
2022年 | 34篇 |
2021年 | 108篇 |
2020年 | 52篇 |
2019年 | 70篇 |
2018年 | 72篇 |
2017年 | 78篇 |
2016年 | 125篇 |
2015年 | 230篇 |
2014年 | 256篇 |
2013年 | 275篇 |
2012年 | 343篇 |
2011年 | 341篇 |
2010年 | 203篇 |
2009年 | 194篇 |
2008年 | 294篇 |
2007年 | 320篇 |
2006年 | 253篇 |
2005年 | 265篇 |
2004年 | 256篇 |
2003年 | 250篇 |
2002年 | 241篇 |
2001年 | 126篇 |
2000年 | 121篇 |
1999年 | 108篇 |
1998年 | 82篇 |
1997年 | 52篇 |
1996年 | 49篇 |
1995年 | 56篇 |
1994年 | 44篇 |
1993年 | 61篇 |
1992年 | 90篇 |
1991年 | 82篇 |
1990年 | 78篇 |
1989年 | 73篇 |
1988年 | 73篇 |
1987年 | 66篇 |
1986年 | 47篇 |
1985年 | 57篇 |
1984年 | 72篇 |
1983年 | 49篇 |
1982年 | 40篇 |
1981年 | 36篇 |
1980年 | 43篇 |
1979年 | 43篇 |
1978年 | 47篇 |
1977年 | 40篇 |
1976年 | 51篇 |
1975年 | 45篇 |
1974年 | 41篇 |
1973年 | 46篇 |
排序方式: 共有6423条查询结果,搜索用时 31 毫秒
991.
992.
993.
994.
Enzymatic synthesis of cytidine diphosphate diglyceride 总被引:15,自引:0,他引:15
Evidence is presented for the enzymatic formation of cytidine diphosphate diglyceride in microsomal preparations from guinea pig liver according to the reaction: CTP + phosphatidic acid right harpoon over left harpoon CDP-diglyceride + p-O-P. Conditions have been found in which the incorporation of labeled CTP into CDP-diglyceride is almost entirely dependent upon added phosphatidic acid. The incorporation of CMP into lipid is very slight. A substantial net synthesis of CDP-diglyceride takes place under these conditions. Some properties of the enzyme system are described. 相似文献
995.
996.
Allison J. Santos Alyssa R. Frederick Benjamin A. Higgins Andres Carrillo Ariel L. Carter Kathryn A. Dickson Donovan P. German Michael H. Horn 《Journal of fish biology》2018,93(2):282-289
Apparent egg cannibalism was investigated in the beach‐spawning California grunion Leuresthes tenuis. Three hypotheses were tested to determine whether L. tenuis regularly consumes and efficiently digests conspecific eggs. First, examination of the gut contents of adults collected at four spawning sites over two seasons showed that the intestines of most fish from all the sites (57–87%, n ≥ 30, each site) contained L. tenuis eggs. The two other hypotheses focused on digestion of the eggs. First, the force required to crush cannibalized eggs was significantly less than that for uncannibalized eggs (fertilized or unfertilized), indicating that ingestion weakens the egg chorions. Second, conspecific eggs fed to fish held in the laboratory visibly degraded as they passed through the gut. The eggs lost c. half of their protein content and about two‐thirds of their lipid content as they passed from proximal to distal regions of the gut, indicating that digestion occurred. Digestive enzyme activities of the gut further confirmed that L. tenuis can break down the contents of ingested eggs. Trypsin activity decreased and aminopeptidase activity increased posteriorly along the gut, whereas amylase and lipase activities exhibited less clear patterns by gut region. As far as is known, this study is the first to show that L. tenuis is an egg cannibal. 相似文献
997.
Marc Potempa Sook-Kyung Lee Nese Kurt Yilmaz Ellen A. Nalivaika Amy Rogers Ean Spielvogel Charles W. Carter Celia A. Schiffer Ronald Swanstrom 《Journal of molecular biology》2018,430(24):5182-5195
Retroviral proteases (PRs) have a unique specificity that allows cleavage of sites with or without a P1′ proline. A P1′ proline is required at the MA/CA cleavage site due to its role in a post-cleavage conformational change in the capsid protein. However, the HIV-1 PR prefers to have large hydrophobic amino acids flanking the scissile bond, suggesting that PR recognizes two different classes of substrate sequences. We analyzed the cleavage rate of over 150 combinations of six different HIV-1 cleavage sites to explore rate determinants of cleavage. We found that cleavage rates are strongly influenced by the two amino acids flanking the amino acids at the scissile bond (P2–P1/P1′–P2′), with two complementary sets of rules. When P1′ is proline, the P2 side chain interacts with a polar region in the S2 subsite of the PR, while the P2′ amino acid interacts with a hydrophobic region of the S2′ subsite. When P1′ is not proline, the orientations of the P2 and P2′ side chains with respect to the scissile bond are reversed; P2 residues interact with a hydrophobic face of the S2 subsite, while the P2′ amino acid usually engages hydrophilic amino acids in the S2′ subsite. These results reveal that the HIV-1 PR has evolved bi-functional S2 and S2′ subsites to accommodate the steric effects imposed by a P1′ proline on the orientation of P2 and P2′ substrate side chains. These results also suggest a new strategy for inhibitor design to engage the multiple specificities in these subsites. 相似文献
998.
The role of glutamate signaling in incentive salience: second‐by‐second glutamate recordings in awake Sprague‐Dawley rats
下载免费PDF全文
![点击此处可从《Journal of neurochemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Seth R. Batten Francois Pomerleau Jorge Quintero Greg A. Gerhardt Joshua S. Beckmann 《Journal of neurochemistry》2018,145(4):276-286
999.
1000.