全文获取类型
收费全文 | 368251篇 |
免费 | 36158篇 |
国内免费 | 196篇 |
专业分类
404605篇 |
出版年
2018年 | 3258篇 |
2017年 | 3266篇 |
2016年 | 5753篇 |
2015年 | 9785篇 |
2014年 | 10305篇 |
2013年 | 11838篇 |
2012年 | 12050篇 |
2011年 | 9659篇 |
2010年 | 7082篇 |
2009年 | 6885篇 |
2008年 | 7578篇 |
2007年 | 7718篇 |
2006年 | 7633篇 |
2005年 | 13249篇 |
2004年 | 11838篇 |
2003年 | 9965篇 |
2002年 | 7454篇 |
2001年 | 18117篇 |
2000年 | 17701篇 |
1999年 | 14426篇 |
1998年 | 4142篇 |
1997年 | 4252篇 |
1996年 | 3928篇 |
1995年 | 3611篇 |
1994年 | 3596篇 |
1993年 | 3634篇 |
1992年 | 11978篇 |
1991年 | 11969篇 |
1990年 | 11522篇 |
1989年 | 11319篇 |
1988年 | 10604篇 |
1987年 | 9896篇 |
1986年 | 8947篇 |
1985年 | 8823篇 |
1984年 | 6753篇 |
1983年 | 5791篇 |
1982年 | 3997篇 |
1981年 | 3542篇 |
1980年 | 3350篇 |
1979年 | 6286篇 |
1978年 | 4774篇 |
1977年 | 4268篇 |
1976年 | 3858篇 |
1975年 | 4557篇 |
1974年 | 4826篇 |
1973年 | 4758篇 |
1972年 | 4276篇 |
1971年 | 4004篇 |
1970年 | 3564篇 |
1969年 | 3480篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
The effects on a cloned DNA fragment carrying an actinomycin resistance determinant on physiological processes in strains of streptomycetes with various potencies in producing this antibiotic, their inactive mutants, and the model strain ofStreptomyces lividans66 were studied. This fragment was shown to modulate bacterial resistance to actinomycin and biosynthesis of antibiotics. 相似文献
72.
Construction of a human cytochrome c gene and its functional expression in Saccharomyces cerevisiae 总被引:1,自引:0,他引:1
Y Tanaka T Ashikari Y Shibano T Amachi H Yoshizumi H Matsubara 《Journal of biochemistry》1988,103(6):954-961
The nucleotide sequences of a partial cDNA and three pseudogenes of human cytochrome c were determined. The complete nucleotide sequences which encode human cytochrome c were constructed on the basis of one of the pseudogenes by in vitro mutagenesis. The constructed human cytochrome c was functionally expressed in Saccharomyces cerevisiae. The recombinant human cytochrome c was purified and characterized. 相似文献
73.
Auranofin affects early events in human polymorphonuclear neutrophil activation by receptor-mediated stimuli 总被引:1,自引:0,他引:1
I Hafstr?m B E Seligmann M M Friedman J I Gallin 《Journal of immunology (Baltimore, Md. : 1950)》1984,132(4):2007-2014
Auranofin, a new oral antirheumatic gold compound, in concentrations achieved therapeutically, inhibits neutrophil phagocytosis, chemotaxis, chemiluminescence, reduction of cytochrome c, and release of lysosomal enzymes. To further characterize the mechanism by which auranofin affects neutrophils, we studied the effects of auranofin on unstimulated properties and functions of neutrophils as well as on rapidly stimulated functions. When examined by electron microscopy, 4 micrograms/ml of auranofin significantly decreased the number of visualized centriole-associated microtubules in resting cells. Furthermore, auranofin inhibited neutrophil spreading on glass and caused a decrease in negative surface charge (electrophoretic mobility). In addition, auranofin inhibited several fmet-leu-phe-stimulated responses such as shape change, increases in centriole-associated microtubules, decreases in surface charge, and elicited membrane potential changes (di-O-C5(3) dye response). Auranofin (1 micrograms/ml) inhibited fmet-leu-phe-stimulated superoxide and hydrogen peroxide production by 80% (p less than 0.05), and also increased the affinity of receptors for fmet-leu-phe (from Ka 0.035 to Ka 0.48, p less than 0.001). Auranofin also affected neutrophil responses to phorbol myristic acetate (PMA). The total amount of PMA-stimulated superoxide production was suppressed by as little as 0.4 micrograms/ml of auranofin, but the lag time for activation was shortened by low concentrations of auranofin (0.5 to 1 microgram/ml). Four micrograms per milliliter of auranofin suppressed the decrease in surface charge induced by PMA. However, auranofin did not influence superoxide production elicited by the ionophore A23187. The results indicate that auranofin affects the earliest detected responses in neutrophil activation by certain receptor-mediated stimuli. 相似文献
74.
75.
Victoria V. Hargreaves Scarlet S. Shell Dan J. Mazur Martin T. Hess Richard D. Kolodner 《The Journal of biological chemistry》2010,285(12):9301-9310
Indirect evidence has suggested that the Msh2-Msh6 mispair-binding complex undergoes conformational changes upon binding of ATP and mispairs, resulting in the formation of Msh2-Msh6 sliding clamps and licensing the formation of Msh2-Msh6-Mlh1-Pms1 ternary complexes. Here, we have studied eight mutant Msh2-Msh6 complexes with defective responses to nucleotide binding and/or mispair binding and used them to study the conformational changes required for sliding clamp formation and ternary complex assembly. ATP binding to the Msh6 nucleotide-binding site results in a conformational change that allows binding of ATP to the Msh2 nucleotide-binding site, although ATP binding to the two nucleotide-binding sites appears to be uncoupled in some mutant complexes. The formation of Msh2-Msh6-Mlh1-Pms1 ternary complexes requires ATP binding to only the Msh6 nucleotide-binding site, whereas the formation of Msh2-Msh6 sliding clamps requires ATP binding to both the Msh2 and Msh6 nucleotide-binding sites. In addition, the properties of the different mutant complexes suggest that distinct conformational states mediated by communication between the Msh2 and Msh6 nucleotide-binding sites are required for the formation of ternary complexes and sliding clamps. 相似文献
76.
77.
A L Nevmiatullin O N Vorob'eva A N Maianski? 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1985,(7):67-71
The neutrophil-stimulating properties of 38 S. aureus strains and 32 S. epidermidis strains were studied in the reaction of luminol-mediated chemiluminescence. All S. aureus strains and 29 S. epidermidis strains were found to possess neutrophil-stimulating activity, the mean activity index for S. aureus being significantly higher. The stimulating activity of the strains varied within a wide range (the variation coefficient was 120.0 +/- 21.9%) and did not correlate with the content of protein A in bacterial cells and the degree of their hydrophoby. The opsonization of staphylococci with normal human serum enhanced the neutrophil reaction 1.5- to 100-fold and simultaneously leveled out the chemiluminescence indices in experiments with different strains (the variation coefficient was 8.0 +/- 1.5%). The nature of the neutrophil-stimulating effect of staphylococci and its relationship to the exploratory reactions of phagocytes are discussed. 相似文献
78.
T Smith 《BMJ (Clinical research ed.)》1984,289(6449):909-910
79.
80.
Intraperitoneal stimulation of adoptively sensitized rats with bacterial antigen promotes the localization of lymphoblasts at the site of antigen deposition. Lymphoblast extravasation activity (LEA) is generated only when specifically immune donor lymphocytes and the recipients of these cells share at least on Ag-B haplotype. However, if the specificity criteria for its formation are satisfied, LEA promotes the local development of lymphoblasts of all available specificities and irrespective of their Ag-B genotype. Allogeneic lymphoblasts do not participate actively in the delayed inflammatory reaction even when they are passively recruited into exudates. The results suggest that LEA is a T cell-derived mediator that amplifies the delayed type hypersensitivity reaction by directing recently activated lymphocytes into lesions. 相似文献