全文获取类型
收费全文 | 25111篇 |
免费 | 2207篇 |
国内免费 | 20篇 |
出版年
2022年 | 170篇 |
2021年 | 340篇 |
2020年 | 174篇 |
2019年 | 251篇 |
2018年 | 314篇 |
2017年 | 270篇 |
2016年 | 489篇 |
2015年 | 859篇 |
2014年 | 942篇 |
2013年 | 1177篇 |
2012年 | 1553篇 |
2011年 | 1618篇 |
2010年 | 992篇 |
2009年 | 862篇 |
2008年 | 1262篇 |
2007年 | 1347篇 |
2006年 | 1247篇 |
2005年 | 1270篇 |
2004年 | 1215篇 |
2003年 | 1220篇 |
2002年 | 1185篇 |
2001年 | 288篇 |
2000年 | 200篇 |
1999年 | 293篇 |
1998年 | 349篇 |
1997年 | 256篇 |
1996年 | 222篇 |
1995年 | 250篇 |
1994年 | 235篇 |
1993年 | 222篇 |
1992年 | 244篇 |
1991年 | 195篇 |
1990年 | 183篇 |
1989年 | 166篇 |
1988年 | 190篇 |
1987年 | 179篇 |
1986年 | 163篇 |
1985年 | 205篇 |
1984年 | 229篇 |
1983年 | 178篇 |
1982年 | 252篇 |
1981年 | 269篇 |
1980年 | 257篇 |
1979年 | 169篇 |
1978年 | 180篇 |
1977年 | 159篇 |
1976年 | 184篇 |
1975年 | 132篇 |
1974年 | 160篇 |
1973年 | 165篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
21.
22.
Charles Romeo Naoko Moriwaki Kerry T. Yasunobu Irwin C. Gunsalus Hideo Koga 《Journal of Protein Chemistry》1987,6(3):253-261
The first 12 NH2-terminal amino acids of the Pseudomonas putida putidaredoxin reductase were shown to be Met-Asn-Ala-Asn-Asp-Asn-Val-Val-Ile-Val-Gly-Thr. Comparison of these data with the DNA sequence of the BamHI-HindIII 197-base fragment derived from the PstI 2.2-kb fragment obtained from the P. putida plasmid showed that the putidaredoxin reductase gene was downstream from the cytochrome P-450 gene and the intergenic region had the 24-nucleotide sequence TAAACACATGGGAGTGCGTGCTAA. The Shine-Dalgarno sequence GGAG was detected in this region. The initiating triplet for the reductase gene was GTG, which normally codes for valine, but in the initiating codon position codes for methionine. From the amino acid sequence and X-ray data comparisons with other flavoproteins, what appears to be the AMP binding region of the FAD can be recognized in the NH2-terminal portion of the reductase involving residues 5–35.This article was presented during the proceedings of the International Conference on Macromolecular Structure and Function, held at the National Defence Medical College, Tokorozawa, Japan, December 1985. 相似文献
23.
Charles B. Lindemann 《Biophysical journal》2009,97(11):2865-2866
24.
Chen Chen Raymond Dagnino Jr. Charles Q. Huang James R. McCarthy Dimitri E. Grigoriadis 《Bioorganic & medicinal chemistry letters》2001,11(24):3165-3168
Cyclizations of alkylhydrazines with N-acyl-S-methylisothioureas, readily synthesized from acyl chlorides, sodium thioisocyanate, dialkylamines then methyl iodide in a one-pot reaction, gave 1-alkyl-3-dialkylamino-5-phenyltriazoles 7 as major products. The regioisomers were assigned through the use of NOE NMR experiments. While bearing a N-bis(cyclopropyl)methyl-N-propylamino group, this series of compounds shows very good binding affinity on the human CRF1 receptor. Among them, 1-methyl-3-[N-bis(cyclopropyl)methyl-N-propylamino]-5-(2,4-dichlorophenyl)-1H-[1,2,4]triazole 7a had the best binding affinity for the CRF1 receptor (Ki=9 nM). 相似文献
25.
In many ecological situations, resources are difficult to find but become more apparent to nearby searchers after one of their numbers discovers and begins to exploit them. If the discoverer cannot monopolize the resources, then others may benefit from joining the discoverer and sharing their discovery. Existing theories for this type of conspecific attraction have often used very simple rules for how the decision to join a discovered resource patch should be influenced by the number of individuals already exploiting that patch. We use a mechanistic, spatially explicit model to demonstrate that individuals should not necessarily simply join patches more often as the number of individuals exploiting the patch increases, because those patches are likely to be exhausted soon or joining them will intensify future local competition. Furthermore, we show that this decision should be sensitive to the nature of the resource patches, with individuals being more responsive to discoveries in general and more tolerant of larger numbers of existing exploiters on a patch when patches are resource-rich and challenging to locate alone. As such, we argue that this greater focus on underlying joining mechanisms suggests that conspecific attraction is a more sophisticated and flexible tactic than currently appreciated. 相似文献
26.
27.
28.
Charles E. Wenner John C. Cheney L. David Tomei 《Journal of cellular biochemistry》1981,15(2):161-168
The introduction of either PGF2α (10?7 M) or TPA (10?7 M) stimulated, ouabain-sensitive 86Rb+ influx at 30 min in postconfluent 3T3-4 mouse fibroblast cultures by 117% and 124%, respectively. Both TPA and PGF2α at these concentrations stimulated the incorporation of 3H-TdR into DNA. TPA had the greatest stimulatory effect, which was similar to that obtained with 10% fetal calf serum. In accord with the idea that modulation of membrane processes such as Na+/K+ pump activity in fibroblasts may reflect important events related to the initiation of DNA synthesis, it was observed that in both 3T3-4 and C3H-1 0T½ cells there were parallel increases in 3H-TdR incorporation and ouabain-sensitive 86Rb+ influxes with 10?7 M TPA, whereas PGF2α stimulated a significant increase in 3H-TdR incorporation in 3T3-4 but not C3H-10T½ cells and only marginal increases in ouabain-sensitive 86Rb+ influx in both. Therefore, although there appears to be a close correlation between Na+/K+ pump activation and subsequent S-phase entry following TPA stimulation, a similar correlation for PGF2α cannot be confirmed. 相似文献
29.
30.