全文获取类型
收费全文 | 922篇 |
免费 | 117篇 |
国内免费 | 1篇 |
出版年
2022年 | 8篇 |
2021年 | 11篇 |
2018年 | 13篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 25篇 |
2014年 | 27篇 |
2013年 | 52篇 |
2012年 | 32篇 |
2011年 | 45篇 |
2010年 | 22篇 |
2009年 | 40篇 |
2008年 | 45篇 |
2007年 | 37篇 |
2006年 | 47篇 |
2005年 | 37篇 |
2004年 | 45篇 |
2003年 | 41篇 |
2002年 | 39篇 |
2001年 | 12篇 |
2000年 | 14篇 |
1999年 | 18篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 13篇 |
1995年 | 13篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 29篇 |
1991年 | 45篇 |
1990年 | 35篇 |
1989年 | 27篇 |
1988年 | 22篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 16篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 12篇 |
1973年 | 8篇 |
1970年 | 6篇 |
1969年 | 7篇 |
排序方式: 共有1040条查询结果,搜索用时 31 毫秒
971.
972.
973.
974.
Manal Abdel Dayem Yannick Fleury Ginette Devilliers Eddy Chaboisseau robert Girard Pierre Nicolas Antoine Delfour 《FEMS microbiology letters》1996,138(2-3):251-259
Abstract Immunity proteins are thought to protect bacteriocin-producing bacterial strains against the bactericidal effects of their own bacteriocin. The immunity protein which protects the lactic acid bacterium Leuconostoc mesenteroides against mesentericin Y10537 bacteriocin was detected and localized by immunofluorescence and electron microscopy, using antibodies directed against the C-terminal end of the predicted immunity protein. The antibodies recognized the immunity proteins of various strains of Leuconostoc , including Leuconostoc mesenteroides and Leuconostoc gelidum . This study demonstrated that immunity proteins produced by Leuconostoc mesenteroides accumulated in the cytoplasmic compartment of the bacteria. This is in contrast with other known immunity proteins, such as the colicin immunity proteins, which are integral membrane proteins possessing three to four transmembrane domains. 相似文献
975.
The results of the present study indicate first that in the microsomal preparation, the components of the P-450 reduction system are heterogeneously distributed, comprising dissociable and nondissociable parts. Second, the P-450 reduction curve can be adequately described by a sum of two exponential functions, indicating two concurrent first-order reactions. Third, the two phases can be altered independently. The addition of the substrate increased the extent of the fast phase while it had little or no effect on that of the slow phase. Changes in the interaction of the dissociable and nondissociable components affected the extent of the slow phase while they were without effect on that of the fast phase. Experiments with different steroids indicated that the independence of the two phases is not due to functionally different P-450's and that the cytochrome reduced in both phases is essentially P-450C-21. The results are interpreted as follows: Transformation of P-450 from the low- to the high-spin state controls the total P-450 reduced. The rate and the biphasicity of the reduction are functions of the interaction of P-450 and the reductase. 相似文献
976.
Vicki L. Schweickart Carol J. Raport Ronald Godiska Mary G. Byers Roger L. Eddy Jr. Thomas B. Shows Patrick W. Gray 《Genomics》1994,23(3)
A lymphoid-specific member of the G-protein-coupled receptor family has been identified by PCR with degenerate oligonucleotides. We have determined that this receptor, also reported as the Epstein-Barr-induced cDNA EBI1, is expressed in normal lymphoid tissues and in several B- and T-lymphocyte cell lines. While the function and the ligand for EBI1 remain unknown, its sequence and gene structure suggest that it is related to the receptors that recognize chemoattractants, such as interleukin-8, RANTES, C5a, and fMet-Leu-Phe. Like the chemoattractant receptors, EBI1 contains intervening sequences near its 5′ end; however, EBI1 is unique in that both of its introns interrupt the coding region of the first extracellular domain. The gene is encoded on human chromosome 17q12-q21.2. None of the other G-protein-coupled receptors has been mapped to this region, but the C-C chemokine family has been mapped to 17q11-q21. The mouse EBI1 cDNA has also been isolated and encodes a protein with 86% identity to the human homolog. 相似文献
977.
978.
Acrosomal constituents identified with a monoclonal antibody are modified during late spermiogenesis in the mouse 总被引:1,自引:0,他引:1
Monoclonal antibody 1D4, a mouse immunoglobulin M raised against CD-1 mouse spermatogenic cell membranes, recognizes acrosomal constituents in the mouse, rabbit, and guinea pig. In the mouse, acrosomes of round and condensing spermatids were labeled with 1D4 by indirect immunofluorescence on isolated cells and by immunohistochemistry on paraffin sections. During the terminal steps of spermiogenesis, however, acrosomal labeling in mouse germ cells was lost. Little or no 1D4 immunoreactivity was detected by enzyme-linked immunosorbent assays in prepubertal testes, Sertoli cells, or several somatic tissues. To identify antigens recognized by 1D4, mouse spermatogenic cell proteins were separated by one- (1D) and two-dimensional (2D) polyacrylamide gel electrophoresis, transferred to nitrocellulose, and immunostained. Multiple antigens larger than 200,000 relative molecular weight (Mr) were resolved on 1D immunoblots from round and condensing spermatids isolated by sedimentation velocity at unit gravity. A smaller antigen (Mr 85,000 isoelectric point approximately 5.7) was also detected on 1D and 2D immunoblots of round spermatid proteins. These antigens can be labeled biosynthetically with [3H] glucosamine and immunoprecipitated, suggesting that they are a set of glycoconjugates that share a common epitope recognized by 1D4. This determinant is no longer detectable in late spermatids, indicating that biochemical modifications of acrosomal constituents occur during the terminal steps of germ cell differentiation. 相似文献
979.
Brian Dennis Laila Assas Saber Elaydi Eddy Kwessi George Livadiotis 《Theoretical Ecology》2016,9(3):323-335
Allee effects, or positive functional relationships between a population’s density (or size) and its per unit abundance growth rate, are now considered to be a widespread if not common influence on the growth of ecological populations. Here we analyze how stochasticity and Allee effects combine to impact population persistence. We compare the deterministic and stochastic properties of four models: a logistic model (without Allee effects), and three versions of the original model of Allee effects proposed by Vito Volterra representing a weak Allee effect, a strong Allee effect, and a strong Allee effect with immigration. We employ the diffusion process approach for modeling single-species populations, and we focus on the properties of stationary distributions and of the mean first passage times. We show that stochasticity amplifies the risks arising from Allee effects, mainly by prolonging the amount of time a population spends at low abundance levels. Even weak Allee effects become consequential when the ubiquitous stochastic forces affecting natural populations are accounted for in population models. Although current concepts of ecological resilience are bound up in the properties of deterministic basins of attraction, a complete understanding of alternative stable states in ecological systems must include stochasticity. 相似文献
980.