全文获取类型
收费全文 | 2146篇 |
免费 | 300篇 |
专业分类
2446篇 |
出版年
2023年 | 22篇 |
2022年 | 49篇 |
2021年 | 81篇 |
2020年 | 45篇 |
2019年 | 65篇 |
2018年 | 62篇 |
2017年 | 39篇 |
2016年 | 95篇 |
2015年 | 111篇 |
2014年 | 113篇 |
2013年 | 143篇 |
2012年 | 168篇 |
2011年 | 165篇 |
2010年 | 92篇 |
2009年 | 74篇 |
2008年 | 94篇 |
2007年 | 68篇 |
2006年 | 62篇 |
2005年 | 78篇 |
2004年 | 68篇 |
2003年 | 45篇 |
2002年 | 53篇 |
2001年 | 44篇 |
2000年 | 38篇 |
1999年 | 36篇 |
1998年 | 20篇 |
1997年 | 15篇 |
1996年 | 25篇 |
1995年 | 19篇 |
1994年 | 14篇 |
1993年 | 19篇 |
1991年 | 28篇 |
1990年 | 23篇 |
1989年 | 14篇 |
1988年 | 16篇 |
1987年 | 21篇 |
1986年 | 19篇 |
1985年 | 17篇 |
1983年 | 12篇 |
1982年 | 19篇 |
1981年 | 14篇 |
1980年 | 21篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 19篇 |
1976年 | 12篇 |
1975年 | 13篇 |
1973年 | 20篇 |
1969年 | 12篇 |
1966年 | 13篇 |
排序方式: 共有2446条查询结果,搜索用时 0 毫秒
11.
Rotary shadowing of extended molecules dried from glycerol 总被引:77,自引:0,他引:77
12.
Howard R. Morris Maria Panico Michael Barber Robert S. Bordoli Robert D. Sedgwick Andrew Tyler 《Biochemical and biophysical research communications》1981,101(2):623-631
We have studied a selection of peptides using a new mass spectrometric ionisation technique - fast atom bombardment (FAB). We define the fragmentation pathways observed and comment on the utility in sequence analysis. A simple acetylation experiment is shown to aid rapid sequence assignment. 相似文献
13.
We have developed two procedures which allow the very rapid purification of glutamine synthetase (GS) from a diverse variety of bacteria. The first procedure, based upon differential sedimentation, depends upon the association of GS with deoxyribonucleic acid in cell extracts. The second procedure, derived from the method of C. Gross et al (J. Bacteriol. 128:382-389, 1976) for purifying ribonucleic acid polymerase by polyethylene glycol (PEG) precipitation, enabled us to obtain high yields of GS from either small or large quantities of cells. We used the PEG procedure to purify GS from Klebsiella aerogenes, K. pneumoniae, Escherichia coli, Salmonella typhimurium, Rhizobium sp. strain 32H1, R. meliloti, Azotobacter vinelandii, Pseudomonas putida, Caulobacter crescentus, and Rhodopseudomonas capsulata. The purity of the GS obtained, judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was high, and in many instances only a single protein band was detected. 相似文献
14.
L C Nuti B C Wenthworth H J Karavolas W J Tyler O J Ginther 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1975,149(4):877-880
Progesterone concentrations in milk were not significantly different when quantitated by different methods (RIA vs. GLC). There was a significant day effect (P less than 0.05) on milk progesterone level due apparently to gradually decreasing values as pregnancy advanced over days 30, 120 and 210. The means for the percent fat content were different (P less than 0.05) for all comparisons among four times of collection (immediately premilking, milking pool, immediately postmilking, and 3 hr postmilking). For progesterone concentration, the main effect of time and the three-way interaction (time times antiserum times purification method) were significant (P less than 0.005); all other main effects and interactions were not significant. Within each of 4 assay groups (2 antisera times 2 purifications), the concentration of progesterone was greater (P less than 0.05) for the samples which were collected immediately postmilking than for any of the other times of collection. The three-way interaction seemed due primarily to difference in progesterone determinations among the four assay groups in the samples which were taken immediately postmilking. Over all milk samples within each assay group, the percent fat content and the concentration of progesterone were positively correlated (r = 0.71, P less than 0.01). 相似文献
15.
16.
17.
Human p38 mitogen-activated protein kinase inhibitor drugs inhibit Plasmodium falciparum replication
Brumlik MJ Nkhoma S Kious MJ Thompson GR Patterson TF Siekierka JJ Anderson TJ Curiel TJ 《Experimental parasitology》2011,128(2):170-175
We recently demonstrated that human p38 mitogen-activated protein kinase (MAPK) inhibitors reduced in vitro and in vivo replication of the protozoan parasites Toxoplasma gondii and Encephalitozoon cuniculi. In this study, we assessed the efficacy of five p38 MAPK inhibitors to block the replication of Plasmodium falciparum in human erythrocytes cultured ex vivo and demonstrate that the pyridinylimidazole RWJ67657 and the pyrrolobenzimidazole RWJ68198 reduced P. falciparum replication, yielded trophozoites that were greatly diminished in size at 24 h, and that these two agents interfered with stage differentiation. Interestingly, the chloroquine-resistant strain W2 was significantly more sensitive to these drugs than was the chloroquine-sensitive strain HB3. These results suggest that pyridinylimidazoles and pyrrolobenzimidazoles designed to inhibit human p38 MAPK activation can be developed to treat malaria. 相似文献
18.
19.
Florida manatees (Trichechus manatus latirostris) inhabit coastal regions because they feed on the aquatic vegetation that grows in shallow waters, which are the same areas where human activities are greatest. Noise produced from anthropogenic and natural sources has the potential to affect these animals by eliciting responses ranging from mild behavioral changes to extreme aversion. Sound levels were calculated from recordings made throughout behavioral observation periods. An information theoretic approach was used to investigate the relationship between behavior patterns and sound level. Results indicated that elevated sound levels affect manatee activity and are a function of behavioral state. The proportion of time manatees spent feeding and milling changed in response to sound level. When ambient sound levels were highest, more time was spent in the directed, goal‐oriented behavior of feeding, whereas less time was spent engaged in undirected behavior such as milling. This work illustrates how shifts in activity of individual manatees may be useful parameters for identifying impacts of noise on manatees and might inform population level effects. 相似文献
20.
Juan Ignacio Ruiz Kaamel Nuhu Justin Tyler McDaniel Federico Popoff Ariel Izcovich Juan Martin Criniti 《PloS one》2015,10(10)