全文获取类型
收费全文 | 1254篇 |
免费 | 54篇 |
出版年
2023年 | 7篇 |
2022年 | 14篇 |
2021年 | 31篇 |
2020年 | 18篇 |
2019年 | 20篇 |
2018年 | 40篇 |
2017年 | 32篇 |
2016年 | 48篇 |
2015年 | 68篇 |
2014年 | 70篇 |
2013年 | 113篇 |
2012年 | 91篇 |
2011年 | 109篇 |
2010年 | 63篇 |
2009年 | 50篇 |
2008年 | 58篇 |
2007年 | 78篇 |
2006年 | 64篇 |
2005年 | 53篇 |
2004年 | 45篇 |
2003年 | 56篇 |
2002年 | 48篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1970年 | 4篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1966年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有1308条查询结果,搜索用时 390 毫秒
61.
Dzierzewicz Z Szczerba J Weglarz L Swiatkowska L Jasinska D Wilczok T 《FEMS microbiology letters》2003,222(1):69-74
Fifteen (soil and intestinal) strains of Desulfovibrio desulfuricans species were typed by PCR method with the use of primers specific for repetitive extragenic palindromic (REP) and enterobacterial repetitive intergenic consensus (ERIC) sequences. As a result, characteristic DNA fingerprints for the strains were obtained. Moreover, the genetic profiles were found to be useful for typing and distinguishing the strains of D. desulfuricans. According to cluster analysis, PCR with primers complementary to the sequences REP appeared to be slightly more discriminatory than PCR with ERIC primers for the investigated strains. Distinct fingerprint patterns of two isolates derived from the same patient pointed to the different origin of both strains. 相似文献
62.
The S. cerevisiae SCF(Cdc4) is a prototype of RING-type SCF E3s, which recruit substrates for polyubiquitination by the Cdc34 ubiquitin-conjugating enzyme. Current models propose that Cdc34 ubiquitinates the substrate while remaining bound to the RING domain. In contrast, we found that the formation of a ubiquitin thiol ester regulates the Cdc34/SCF(Cdc4) binding equilibrium by increasing the dissociation rate constant, with only a minor effect on the association rate. By using a F72VCdc34 mutant with increased affinity for the RING domain, we demonstrate that release of ubiquitin-charged Cdc34-S - Ub from the RING is essential for ubiquitination of the SCF(Cdc4)-bound substrate Sic1. Release of ubiquitin-charged E2 from E3 prior to ubiquitin transfer is a previously unrecognized step in ubiquitination, which can explain both the modification of multiple lysines on the recruited substrate and the extension of polyubiquitin chains. We discuss implications of this finding for function of other ubiquitin ligases. 相似文献
63.
Divergent effects of leptin on luteinizing hormone and insulin secretion are dose dependent 总被引:1,自引:0,他引:1
Zieba DA Amstalden M Maciel MN Keisler DH Raver N Gertler A Williams GL 《Experimental biology and medicine (Maywood, N.J.)》2003,228(3):325-330
We have shown recently that fasting permits leptin to modulate both luteinizing hormone (LH) and insulin secretion in cows. In rodents, leptin causes divergent effects on LH and insulin release that are dose dependent. To test the hypothesis that leptin effects on LH and insulin secretion in fasted cows are dose related, we examined the effects of various doses of recombinant ovine leptin (oleptin) in mature cows. Twenty ovariectomized beef cows, each bearing an estradiol implant to maintain basal estradiol concentrations, were used. All cows were fasted for 60 hr with free access to water and were assigned randomly to one of four groups (n = 5/group): 1) saline control; 2) leptin, 0.2 microg/kg; 3) leptin, 2.0 microg/kg; and 4) leptin, 20 microg/kg body wt. Blood samples were collected at 10-min intervals for 6 hr on Days 0 and 2, with saline or oleptin injected intravenously immediately after the first intensive sample on Day 2 (54 hr). Leptin caused a dose-related increase (P < 0.001) in mean concentrations of circulating LH. Stimulation of LH release by leptin was significant at the lowest (141% of control) and middle (122% of control) doses used, but no increase was observed for the highest dose. Increased mean concentrations of LH appeared to result from an augmentation of basal secretion, as pulse characteristics were not affected. After 54 hr of fasting, plasma insulin concentrations were lowered (P < 0.01) in all treatment groups compared to Day 0. After leptin injections, plasma insulin concentrations increased (P < 0.01) and reached highest concentrations during the first hour of sampling. However, this increase was sustained for several hours only in the intermediate (2.0 microg/kg) dose group. Collectively, our results show that leptin has potent positive effects on both LH and insulin secretion in fasted cows, but the anterior pituitary and endocrine pancreas appear to become downregulated in the presence of excess ligand. 相似文献
64.
Zuberek J Jemielity J Stepinski J Lewdorowicz M Niedzwiecka A Haber D Stolarski R Rhoads RE Darzynkiewicz E 《Nucleosides, nucleotides & nucleic acids》2003,22(5-8):1703-1706
Studies on the interaction of the murine translation initiation factor 4E with two new-synthesized cap-analogues, modified at C2' of 7-methylguanosine, have been performed by means of the fluorescence titration method. No difference in the binding affinity for eIF4E was observed compared with the "anti reversed" cap analogues, possessing the analogous modifications at C3'. Potential significance of the novel caps as research tools for examination of the nuclear cap binding complex CBC80/20 has been discussed. 相似文献
65.
66.
67.
68.
Predictions of matrix‐assisted refolding of α‐lactalbumin: Process efficiency versus batch dilution method 下载免费PDF全文
Protein refolding is an important technique to produce active recombinant proteins from inclusion bodies. Because of the complexity of the refolding process, a trial‐and‐error method is usually used for its design, which is ineffective and time consuming. Therefore, an efficient method for the process prediction is indispensable to optimize the operating conditions. In this article, we suggest a design procedure for matrix‐assisted protein refolding. Three different chromatographic techniques were considered exploiting hydrophobic interaction chromatography, ion‐exchange chromatography, and SEC media. The procedure consisted of quantification of refolding kinetics, analysis of the retention behavior of all protein forms involved in refolding, construction of a dynamic model, and the process simulation. Denatured bovine α‐lactalbumin was used as model protein. The refolding rate was measured for different protein concentration using the batch dilution method. A kinetic scheme for the protein refolding was suggested and incorporated into a dynamic model of chromatographic column and used for predicting the refolding performance. The productivity, yield, and buffer consumption were used as performance indicators for the refolding techniques considered. The matrix‐assisted protein refolding process outperformed batch dilution method with respect to all indicators provided that efficient method for the process design was used. 相似文献
69.
Lisa Warren Maciej Murawski Karolina Wilk Dorota A Zieba Pawel M Bartlewski 《Experimental biology and medicine (Maywood, N.J.)》2015,240(5):576-584
This study was conducted to determine if correlations exist between the numbers of microscopic follicles comprising ovarian follicular reserve (OFR) and antral follicle counts (AFCs), and to assess the usefulness of computerized analyses of ovarian ultrasonograms and magnetic resonance (MR) images for estimating OFR in excised porcine, ovine and bovine ovaries. As a pre-requisite to these analyses, we characterized and compared ovarian cortical histomorhpology and follicle populations in the three species varying in prolificacy and overall reproductive longevity, and hence the total number of microscopic and antral follicles. Ultrasonographic and MR images were obtained at the scanner settings optimized to provide opposing contrasts between antral follicles and the ovarian stroma. Commercially available ImageProPlus® analytical software was used to calculate numerical pixel values (NPVs) and pixel heterogeneity (standard deviation of the pixel values) along the computer-generated lines (4–6) placed in the area corresponding to the ovarian cortex. The numbers of primordial (r = 0.38, P < 0.01) and intermediate follicles (r = 0.37, P < 0.01) were correlated with the numbers of antral follicles in bovine ovarian sections. The numbers of primordial (r = 0.28, P < 0.05), intermediate (r = 0.31, P < 0.01) and primary follicles (r = 0.27, P < 0.05) correlated directly with mean NPVs of the ultrasonographic ovarian images in cattle. There was a negative correlation between primary follicle numbers and NPVs of MR images (3D FAST-SPOILED GRADIENT ECHO) of the porcine ovarian cortex (r = −0.31, P < 0.05). To summarize, the numbers of primordial and intermediate follicles could only be estimated from AFCs in cows. Using ultrasound NPVs, the numbers of primordial, intermediate and primary follicles could be directly estimated in bovine ovaries and the quantitative image attributes of MR images were useful for quantifying porcine primary follicles. The bovine ovarian model is compatible with human situation and hence future studies should be undertaken to ascertain the usefulness of AFCs and ultrasonographic image analyses for estimating OFR in women. 相似文献
70.
Wioletta Wujcicka Edyta Paradowska Miros?awa Studzińska Zuzanna Gaj Jan Wilczyński Zbigniew Le?nikowski Dorota Nowakowska 《PloS one》2015,10(4)