全文获取类型
收费全文 | 624篇 |
免费 | 21篇 |
国内免费 | 2篇 |
出版年
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2018年 | 7篇 |
2017年 | 18篇 |
2016年 | 13篇 |
2015年 | 8篇 |
2014年 | 13篇 |
2013年 | 20篇 |
2012年 | 30篇 |
2011年 | 35篇 |
2010年 | 27篇 |
2009年 | 23篇 |
2008年 | 20篇 |
2007年 | 27篇 |
2006年 | 24篇 |
2005年 | 19篇 |
2004年 | 24篇 |
2003年 | 18篇 |
2002年 | 22篇 |
2001年 | 19篇 |
2000年 | 13篇 |
1999年 | 22篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 5篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 26篇 |
1991年 | 22篇 |
1990年 | 20篇 |
1989年 | 11篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1975年 | 4篇 |
1972年 | 2篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1967年 | 3篇 |
排序方式: 共有647条查询结果,搜索用时 31 毫秒
1.
Iu A Belaia V M Bondarenko V G Petrukhin I E Deev 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1982,(8):38-42
Genetic and immunoelectrophoretic studies confirm earlier data on the presence of 2 specific antigens of acidic nature in S. newcastle; one of them is a specific thermolabile K-antigen responsible for type IV specificity of these bacteria. The data concerning the differences in the genetic determinants controlling the synthesis of O- and K-antigens in S. newcastle have been obtained. S. newcastle O- and K-antigens did not react with S. flexneri in the group serum system 3, 4, which indicates that S. newcastle are serologically isolated and form a separate taxonomic group of dysentery bacteria. The existence of cross reactions between S. flexneri and S. newcastle due to the presence of neutral R-core antigens common to these 2 species has been shown . Immunoelectrophoresis in agar is the most promising and informative method in genetic and chemical studies of the antigenic structure of bacteria. 相似文献
2.
In intact Wistar pubertal male rats held on LD 8:16 (winter) and 16:8 (summer) pineal melatonin (M) production and other pineal indoles content serotonin (S), 5-methoxytriptamine (5-MT), N-acetylserotonin (N-aS), 5-hydroxyindoleacetic acid (5-HIAA) and 5-methoxyindoleacetic acid (5-MIAA) were investigated in basic conditions and after 10-days T4 administration. The results suggest, that intact control in winter comparing with summer demonstrates high M, N-aS, 5-HIAA and 5-MIAA level, but low 5-MT concentrations, S level was not changed. T4 administration in winter produced a pronounced augmentation of all parameters (excluding serotonin), in summer M production not only increased, but appears to be dependent on the active metabolism of his precursors (S, 5-MT, N-aS). The experimental data favour more profound comprehension to the mechanisms of pineal activity regulation. 相似文献
3.
A histochemical method is described for localizing xanthine oxidase--the key enzyme in the purine catabolic pathway. The above method is based on the reduction of p-Nitroblue tetrazolium during hypoxanthine enzymatic oxidation, phenazine methosulfate being an intermediate electron acceptor. The patterns of the reaction product distribution suggest that the Kupffer cells and the sinusoidal endothelium possess the highest xanthine oxidase activity. 相似文献
4.
The attitude of outbred white male rats to alcohol was determined by means of two behavioural methods--the method of free choice of alcohol or water and of reaction of preference of place (PP) connected with taking of alcohol. Conclusion is made about greater adequacy of PP application for determination of alcohol motivation in animals. 相似文献
5.
6.
The consequences of sterol deficiency in feeding of adult Drosophila females have been studied. Feeding of Drosophila on nys 1 mutant strain yeast leads to significant increase of non-developed eggs in Drosophila females. The effect of sterol deficiency on oogenesis in virgin and fertilized females has been estimated using different regimens of feeding. Possible mechanisms of arising of fertility defects are discussed. 相似文献
7.
Autotrophic picoplankton in southern Lake Baikal: abundance, growth and grazing mortality during summer 总被引:5,自引:0,他引:5
Nagata Toshi; Takai Kenji; Kawanobe Kyoko; Kim Dong-Sup; Nakazato Ryoji; Guselnikova Nina; Bondarenko Nina; Mologawaya Oliga; Kostrnova Tatyana; Drucker Valentine; Satoh Yasuhiro; Watanabe Yasunori 《Journal of plankton research》1994,16(8):945-959
Autotrophic picoplankton were highly abundant during the thermalstratification period in late July in the pelagic area (waterdepth 5001300 m) of southern Lake Baikal; maximum numberswere 2 x 106 cells ml1 in the euphotic zone ({small tilde}15m). Unicellular cyanobacteria generally dominated the picoplanktoncommunity, although unidentified picoplankton that fluorescedred under blue excitation were also abundant (maximum numbers4 x 105 cells ml1) and contributed up to {small tilde}40%of the total autotrophic picoplankton on occasions. Carbon andnitrogen biomasses of autotrophic picoplankton estimated byconversion from biovolumes were 1484 µg C l1and 3.621 µg N l1. These were comparableto or exceeded the biomass of heterotrophic bacteria. Autotropicpicoplankton and bacteria accounted for as much as 33% of paniculateorganic carbon and 81% of nitrogen in the euphotic zone. Measurementsof the photosynthetic uptake of [l4C]bicarbonate and the growthof picoplankton in diluted or size-fractionated waters revealedthat 80% of total primary production was due to picoplankton,and that much of this production was consumed by grazers inthe <20 µ.m cell-size category. These results suggestthat picoplankton-protozoan trophic coupling is important inthe pelagic food web and biogeochemical cycling of Lake Baikalduring summer. 相似文献
8.
The ATP-binding-cassette transmembrane transporters (ABC transporters)
known from vertebrates belong to four major subfamilies: (1) the P-
glycoproteins (Pgp); (2) the cystic fibrosis transmembrane conductance
regulators (CFTR); (3) the Tap proteins encoded with the major
histocompatibility complex of mammals; and (4) the peroxisomal membrane
proteins. Both Pgp and CFTR have a structure suggesting a past internal
gene duplication; a phylogenetic analysis indicated that these duplications
occurred independently, while an independent tandem gene duplication
occurred in the case of the Tap family. Both the Pgp and Tap proteins show
evidence of relationship to bacterial ABC transporters lacking internal
duplication, and both are significantly more closely related to the HlyB
and MsbA families of transporters from purple bacteria than they are to ABC
transporters from nonpurple bacteria. The simplest hypothesis to explain
this observation is that eukaryotic Pgp and Tap genes are descended from a
mitochondrial gene or genes that were subsequently translocated to the
nuclear genome. The Pgp genes of eukaryotes are characterized by a
remarkable degree of convergent evolution between the ATP-binding cassettes
of their N- terminal and C-terminal halves, whereas no such convergence is
seen between the two halves of CFTR genes or between the duplicated Tap
genes. Exon 13 of the CFTR gene, which encodes a putative regulatory domain
not found in other ABC transporters apart from CFTR, showed high levels of
both synonymous and nonsynonymous difference in comparisons among different
mammalian species, suggesting that this region is a mutational hot spot.
相似文献
9.
10.
X Xiao G Hintermann AL Demanin J Piret 《Journal of industrial microbiology & biotechnology》1996,16(4):261-262
Streptomyces glaucescens is shown to possess -lactamase activity which is inhibitable by clavulanate. This is important in regard to its use as a cloning host for enzymes of \-lactam biosynthesis. 相似文献