全文获取类型
收费全文 | 1555篇 |
免费 | 83篇 |
国内免费 | 3篇 |
出版年
2024年 | 4篇 |
2023年 | 18篇 |
2022年 | 42篇 |
2021年 | 76篇 |
2020年 | 37篇 |
2019年 | 41篇 |
2018年 | 78篇 |
2017年 | 47篇 |
2016年 | 58篇 |
2015年 | 77篇 |
2014年 | 101篇 |
2013年 | 92篇 |
2012年 | 102篇 |
2011年 | 77篇 |
2010年 | 54篇 |
2009年 | 54篇 |
2008年 | 78篇 |
2007年 | 79篇 |
2006年 | 56篇 |
2005年 | 51篇 |
2004年 | 60篇 |
2003年 | 43篇 |
2002年 | 31篇 |
2001年 | 23篇 |
2000年 | 35篇 |
1999年 | 21篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 16篇 |
1991年 | 15篇 |
1990年 | 17篇 |
1989年 | 18篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1977年 | 4篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有1641条查询结果,搜索用时 31 毫秒
31.
Microbial mineralization of organic phosphate in soil 总被引:35,自引:0,他引:35
Summary Phosphate-dissolving microorganisms were isolated from non-rhizosphere and rhizosphere of plants. These isolates included
bacteria, fungi and actinomycetes. In broth cultures, Gram-negative short rod,Bacillus andStreptomyces species were found to be more active in solubilizing phosphate thanAspergillus, Penicillium, Proteus, Serratia, Pseudomonas andMicrococcus spp. The sterile soils mixed with isolated pure culture showed slower mineralization of organic phosphate than that of non-sterile
soil samples at all incubation periods. Maximum amount of phosphate mineralization by isolated microorganisms were obtained
at the 60th and the 75th day of incubation in sterile and non-sterile soils respectively. The mixed cultures were most effective
in mineralizing organic phosphate and individuallyBacillus sp. could be ranked next to mixed cultures. Species ofPseudomonas andMicrococcus were almost the same as that of the control under both sterile and non-sterile conditions. 相似文献
32.
33.
Oxathiolanes and disulfonyl derivatives of steroids were tested for mutagenic activity in the Ames tester strains. The test compounds exhibited mutagenic activity without metabolic activation although metabolic activation markedly enhanced their activity. A significant decrease in the survival of the radiation-sensitive mutants recA, lexA and rer of E. coli was observed as compared to their wild-type counterpart in the presence of the test steroid. Structural features which appear to be crucial for the mutagenic activity in these steroidal drugs are: (i) an electron-donating group at position 3, and (ii) a bulky group anchored at the 5th and 6th positions. The test steroids appear to damage DNA which in turn initiates the SOS repair with the concomitant induction of mutation. 相似文献
34.
Genomic in situ hybridization to identify alien chromosomes and chromosome segments in wheat 总被引:15,自引:0,他引:15
T. Schwarzacher K. Anamthawat-Jónsson G. E. Harrison A. K. M. R. Islam J. Z. Jia I. P. King A. R. Leitch T. E. Miller S. M. Reader W. J. Rogers M. Shi J. S. Heslop-Harrison 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1992,84(7-8):778-786
Summary Genomic in situ hybridization was used to identify alien chromatin in chromosome spreads of wheat, Triticum aestivum L., lines incorporating chromosomes from Leymus multicaulis (Kar. and Kir.) Tzvelev and Thinopyrum bessarabicum (Savul. and Rayss) Löve, and chromosome arms from Hordeum chilense Roem. and Schult, H. vulgare L. and Secale cereale L. Total genomic DNA from the introgressed alien species was used as a probe, together with excess amounts of unlabelled blocking DNA from wheat, for DNA:DNA in-situ hybridization. The method labelled the alien chromatin yellow-green, while the wheat chromosomes showed only the orange-red fluorescence of the DNA counterstain. Nuclei were screened from seedling root-tips (including those from half-grains) and anther wall tissue. The genomic probing method identified alien chromosomes and chromosome arms and allowed counting in nuclei at all stages of the cell cycle, so complete metaphases were not needed. At prophase or interphase, two labelled domains were visible in most nuclei from disomic lines, while only one labelled domain was visible in monosomic lines. At metaphase, direct visualization of the morphology of the alien chromosome or chromosome segment was possible and allowed identification of the relationship of the alien chromatin to the wheat chromosomes. The genomic in-situ hybridization method is fast, sensitive, accurate and informative. Hence it is likely to be of great value for both cytogenetic analysis and in plant breeding programmes. 相似文献
35.
Anther culture responsiveness of three H. spontaneum derived spring barley lines, RS170-47(A), RS20-1(B) and 1B-152B(C) was investigated using only one type of culture medium and treatment. The line 1B-152B was identified as highly responsive producing 22.4 total and 12.4 green regenerants per 100 anthers plated. 74% of these green regenerants were spontaneous double haploids. A genetic analysis involving F1 and F2 plants derived from crosses A × B and B × C revealed that the factor(s) determining high anther culture responsiveness in line 1B-152B was heritable and behaved as dominant in the F1. There was an indication that genotypic responsiveness in anther culture for green plant regeneration was different from total or albino plant regeneration. 相似文献
36.
37.
38.
Human Genetics - In a sample of Bengali Muslems from Dacca, haptoglobin, group-specific component, haemoglobin, adenosine deaminase, adenylate kinase, 6-phosphogluconate dehydrogenase,... 相似文献
39.
40.
Islam MS Tasmin R Khan SI Bakht HB Mahmood ZH Rahman MZ Bhuiyan NA Nishibuchi M Nair GB Sack RB Huq A Colwell RR Sack DA 《Canadian journal of microbiology》2004,50(10):827-834
A total of 1500 environmental strains of Vibrio parahaemolyticus, isolated from the aquatic environment of Bangladesh, were screened for the presence of a major V. parahaemolyticus virulence factor, the thermostable direct haemolysin (tdh) gene, by the colony blot hybridization method using a digoxigenin-labeled tdh gene probe. Of 1500 strains, 5 carried the tdh sequence, which was further confirmed by PCR using primers specific for the tdh gene. Examination by PCR confirmed that the 5 strains were V. parahaemolyticus and lacked the thermostable direct haemolysin-related haemolysin (trh) gene, the alternative major virulence gene known to be absent in pandemic strains. All 5 strains gave positive Kanagawa phenomenon reaction with characteristic beta-haemolysis on Wagatsuma agar medium. Southern blot analysis of the HindIII-digested chromosomal DNA demonstrated, in all 5 strains, the presence of 2 tdh genes common to strains positive for Kanagawa phenomenon. However, the 5 strains were found to belong to 3 different serotypes (O3:K29, O4:K37, and O3:K6). The 2 with pandemic serotype O3:K6 gave positive results in group-specific PCR and ORF8 PCR assays, characteristics unique to the pandemic clone. Clonal variations among the 5 isolates were analyzed by comparing RAPD and ribotyping patterns. Results showed different patterns for the 3 serotypes, but the pattern was identical among the O3:K6 strains. This is the first report on the isolation of pandemic O3:K6 strains of V. parahaemolyticus from the aquatic environment of Bangladesh. 相似文献