全文获取类型
收费全文 | 632篇 |
免费 | 120篇 |
国内免费 | 2篇 |
专业分类
754篇 |
出版年
2021年 | 15篇 |
2020年 | 5篇 |
2019年 | 13篇 |
2018年 | 16篇 |
2017年 | 14篇 |
2016年 | 20篇 |
2015年 | 33篇 |
2014年 | 29篇 |
2013年 | 24篇 |
2012年 | 38篇 |
2011年 | 42篇 |
2010年 | 28篇 |
2009年 | 16篇 |
2008年 | 27篇 |
2007年 | 40篇 |
2006年 | 31篇 |
2005年 | 24篇 |
2004年 | 28篇 |
2003年 | 24篇 |
2002年 | 19篇 |
2001年 | 15篇 |
2000年 | 13篇 |
1999年 | 18篇 |
1998年 | 10篇 |
1997年 | 4篇 |
1996年 | 9篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 15篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 10篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1971年 | 4篇 |
1970年 | 4篇 |
1969年 | 5篇 |
1967年 | 4篇 |
排序方式: 共有754条查询结果,搜索用时 0 毫秒
91.
A Rettinger I Krupka K Grünwald V Dyachenko V Fingerle R Konrad H Raschel U Busch A Sing RK Straubinger I Huber 《BMC microbiology》2012,12(1):185
ABSTRACT: BACKGROUND: In this study mass spectrometry was used for evaluating extracted leptospiral protein samples and results were compared with molecular typing methods. For this, an extraction protocol for Leptospira spp. was independently established in two separate laboratories. Reference spectra were created with 28 leptospiral strains, including pathogenic, non-pathogenic and intermediate strains. This set of spectra was then evaluated on the basis of measurements with well-defined, cultured leptospiral strains and with 16 field isolates of veterinary or human origin. To verify discriminating peaks for the applied pathogenic strains, statistical analysis of the protein spectra was performed using the software tool ClinProTools. In addition, a dendrogram of the reference spectra was compared with phylogenetic trees of the 16S rRNA gene sequences and multi locus sequence typing (MLST) analysis. RESULTS: Defined and reproducible protein spectra using MALDI-TOF MS were obtained for all leptospiral strains. Evaluation of the newly-built reference spectra database allowed reproducible identification at the species level for the defined leptospiral strains and the field isolates. Statistical analysis of three pathogenic genomospecies revealed peak differences at the species level and for certain serovars analyzed in this study. Specific peak patterns were reproducibly detected for the serovars Tarassovi, Saxkoebing, Pomona, Copenhageni, Australis, Icterohaemorrhagiae and Grippotyphosa. Analysis of the dendrograms of the MLST data, the 16S rRNA sequencing, and the MALDI-TOF MS reference spectra showed comparable clustering. CONCLUSIONS: MALDI-TOF MS analysis is a fast and reliable method for species identification, although Leptospira organisms need to be produced in a time-consuming culture process. All leptospiral strains were identified, at least at the species level, using our described extraction protocol. Statistical analysis of the three genomospecies L. borgpetersenii, L. interrogans and L. kirschneri revealed distinctive, reproducible differentiating peaks for seven leptospiral strains which represent seven serovars. Results obtained by MALDI-TOF MS were confirmed by MLST and 16S rRNA gene sequencing. 相似文献
92.
Endophytic bacteria which are known to reside in plant tissues have often been shown to promote plant growth. Present study deals with the isolation of putative endophytes from the surface sterilized root nodules of pigeon pea (Cajanus cajan) designated as non-rhizobial (NR) isolates. Three of these non-rhizobial isolates called NR2, NR4 and NR6 showed plant growth promotion with respect to increase in plant fresh weight, chlorophyll content, nodule number and nodule fresh weight when co-inoculated with the rhizobial bioinoculant strain IC3123. The three isolates were neither able to nodulate C. cajan nor did they show significant plant growth promotion when inoculated alone without Rhizobium spp. IC3123. All the three isolates were gram positive rods with NR2 and NR4 showing endospore formation and formed one single cluster in Amplified Ribosomal DNA Restriction Analysis (ARDRA). Partial sequences of 16S rRNA genes of NR4 and NR6 showed 97% similarity to Bacillus megaterium. The Bacillus strains NR4 and NR6 were able to produce siderophores which the rhizobial bioinoculant IC3123 was able to cross-utilize. Under iron starved conditions IC3123 showed enhanced growth in the presence of the Bacillus isolates indicating that siderophore mediated interactions may be underlying mechanism of beneficial effect of the NR isolates on nodulation by IC3123. 相似文献
93.
Recently, agent techniques in electronic marketplaces (e-marketplaces) bring B-to-B trading into a new era. However, not much analysis on the behavior of agents has been reported. In this paper, based on the ant algorithm in network routing, we introduce a jumping (searching) model for agents in an e-marketplace network. However, we should be aware that if there are too many agents in the e-marketplace network, they will use up all communication bandwidth and computing resource. It is inevitable to investigate the behavior of agents, such as agent population. Based on the existing results in the ant algorithm in network routing, we present the behavior of agents in an e-marketplace network. Hence, we can control the agent population by setting the appropriate agent generation rate. 相似文献
94.
Phagocytosis of Yersinia pseudotuberculosis occurs through interaction of the bacterial protein invasin with beta1-integrins. Here we report that N-WASP plays a role in internalisation of an invasin-expressing, avirulent strain of Y. pseudotuberculosis. Ectopic expression of N-WASP mutants, which affect recruitment of the Arp2/3 complex to the phagosome, reduces uptake of Yersinia. In addition, expression of the Cdc42/Rac-binding (CRIB) region of N-WASP has an inhibitory effect on uptake. Using GFP-tagged Rho GTPase mutants, we provide evidence that Rac1, but not Cdc42, is important for internalisation. Furthermore, activated Rac1 rescues Toxin B, CRIB and Src family kinase inhibitor PP2-mediated impairment of uptake. Our observations indicate that invasin-mediated phagocytosis occurs via a Src and WASP family-dependent mechanism(s), involving the Arp2/3 complex and Rac, but does not require Cdc42. 相似文献
95.
96.
97.
A simple and effective cryogenic procedure for the extraction of glycolytic intermediates from whole Drosophila has been developed. This procedure gives consistent results when a measure (µM/liter/OD260) is adopted which corrects for differences in extraction efficiency. Using this measure and a homozygous strain of D. mercatorum, there are no significant differences among extracts for the levels of any of the 15 glycolytic intermediate or energy molecules considered. The profile of means is consistent across experimental designs and instrument types. Coefficients of variation are well below 50% for most variables. The methodology presented has the statistical power to detect a mean change of 10 to 50% using an experimental design which requires as few as 32 observations. The estimated energy charge for resting Drosophila from these studies is the expected value of 0.86. 相似文献
98.
99.
These studies demonstrated that continuous morphine treatment from implantation of a 75 mg morphine pellet for 3 days potentiated pentobarbital narcosis and enhanced pentobarbital hypothermia. In the morphine implant mice, sleeping time after two different doses of pentobarbital was greater than 2.5 × the sleeping time in placebo pellet implant animals and also greater than sleeping time in animals treated acutely with morphine prior to pentobarbital. Moreover, in the morphine implant mice both the degree and duration of pentobarbital induced hypothermia were enhanced. The above findings were due to slower rate of metabolism of pentobarbital as evidenced by inhibition of hepatic N-demethylation, and higher levels of brain and serum pentobarbital in the morphine implant mice compared to both placebo and acute morphine mice. 相似文献
100.