全文获取类型
收费全文 | 244871篇 |
免费 | 22525篇 |
国内免费 | 253篇 |
出版年
2018年 | 2636篇 |
2017年 | 2579篇 |
2016年 | 3428篇 |
2015年 | 3663篇 |
2014年 | 4578篇 |
2013年 | 6556篇 |
2012年 | 7209篇 |
2011年 | 7902篇 |
2010年 | 5384篇 |
2009年 | 4789篇 |
2008年 | 6871篇 |
2007年 | 7081篇 |
2006年 | 6716篇 |
2005年 | 6414篇 |
2004年 | 6317篇 |
2003年 | 6153篇 |
2002年 | 6016篇 |
2001年 | 12007篇 |
2000年 | 11963篇 |
1999年 | 9146篇 |
1998年 | 2672篇 |
1997年 | 2745篇 |
1996年 | 2693篇 |
1995年 | 2479篇 |
1994年 | 2426篇 |
1993年 | 2317篇 |
1992年 | 7175篇 |
1991年 | 6978篇 |
1990年 | 7058篇 |
1989年 | 6841篇 |
1988年 | 6356篇 |
1987年 | 6009篇 |
1986年 | 5355篇 |
1985年 | 5661篇 |
1984年 | 4462篇 |
1983年 | 3862篇 |
1982年 | 2669篇 |
1981年 | 2493篇 |
1980年 | 2303篇 |
1979年 | 4107篇 |
1978年 | 3134篇 |
1977年 | 2881篇 |
1976年 | 2826篇 |
1975年 | 3268篇 |
1974年 | 3496篇 |
1973年 | 3524篇 |
1972年 | 3058篇 |
1971年 | 2842篇 |
1970年 | 2530篇 |
1969年 | 2299篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
S A Bitko L O Dynga A R Shikhman Z F Shmakova N I Briko 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1990,(4):3-7
The amino acid composition of cell walls and surface proteins, isolated from virulent (M+) and avirulent (M-) streptococcal strains (group A, type 29) has been determined by the method of E. H. Beachey et al. The kinetics of the lysis and proteolysis of streptococcal cell walls with muramidase and protease obtained from Actinomyces levoris and streptolysin has been studied. The constants describing the progress rates of these processes has been determined; their values in case of both lysis and proteolysis are higher in virulent strains than in avirulent ones. 相似文献
943.
Construction of isogenic gonococci with variable porin structure: effects on susceptibility to human serum and antibiotics 总被引:11,自引:2,他引:9
Protein I (PI) is the most abundant protein on the gonococcal cell surface and besides its porin function it may have important properties contributing to pathogenicity. By allelic exchange using cloned PI genes from FA19 (PIA) and MS11 (PIB) and a selectable marker introduced closely downstream of these genes, we constructed sets of isogenic gonococcal strains that differ only in their PI gene. Analysis revealed that PI has a major effect on stable resistance to normal human serum, and a slight effect on low-level resistance to antibiotics. All PIA/B hybrids were hypersusceptible to serum, suggesting a possible explanation for why such hybrids do not occur in nature. 相似文献
944.
945.
Scalp reconstruction with a prefabricated abdominal flap carried by the radial artery. 总被引:3,自引:0,他引:3
Custom prefabrication of free flaps provides an unlimited variety of applications, since flaps can be created with expendable tissues and without restriction to naturally occurring vascular territories. These principles also can be used to customize flaps that could not be completed by conventional means. We report a case of scalp reconstruction using a random-pattern abdominal flap in which a radial artery fascial flap was induced to serve as the vascular carrier. In addition to providing durable scalp coverage, the prefabricated free flap enabled salvage of an abdominal flap that would otherwise have been aborted after intermediate transfer to the forearm. 相似文献
946.
947.
948.
Journal of Ichthyology - The paper considers the effect of the Sea of Azov salinization on the food supply to anchovy Engraulis encrasicolus maeoticus as the level of salinity was rising from 12.7... 相似文献
949.
Relationships between the strongyloid nematodesRugopharynx delta, R. zeta, R. omega, R. longibursaris, R. mawsonae andR. sigma, all from macropodid marsupials, were investigated using allozyme data. The phylogenetic trees derived from the electrophoretic data set were congruent with those of the hosts and were consistent with the hypothesis that the species complex originated in pademelons of the genusThylogale and diversified in rock-wallabies (Petrogale spp.) and scrub wallabies of the subgenusNotamacropus. Host switching is evident only between closely related macropodid taxa. 相似文献
950.
G N Kryzhanovski? V G Kucherianu L S Godlevski? A D Mazarati 《Biulleten' eksperimental'no? biologii i meditsiny》1992,113(1):16-19
The effect of intranasal substance P injection on parkinsonian syndrome and the generator of pathologically enhanced excitation (GPEE) in caudate nuclei (CN) was investigated. MPTP or reserpine administration in old rats induced oligokinesia, rigidity and tremor followed by the high amplitude slow and rapid waves in both CN. The bilateral intranasal injection of substance P (25 micrograms/kg) resulted in an increase in motor activity and almost completely abolished the rigidity and tremor. The reduction of extrapyramidal symptoms was considered as a result of the inhibition of GPEE in CN. The possibility of substance P entry from nasal cavity into the brain was discussed. The changes of the substance P balance in nigrostriatal system was suggested to be on of the pathogenetic links of parkinsonian syndrome. 相似文献