全文获取类型
收费全文 | 5024篇 |
免费 | 0篇 |
出版年
2012年 | 34篇 |
2011年 | 64篇 |
2010年 | 15篇 |
2008年 | 56篇 |
2007年 | 77篇 |
2006年 | 86篇 |
2005年 | 102篇 |
2004年 | 80篇 |
2003年 | 96篇 |
2002年 | 82篇 |
2001年 | 80篇 |
2000年 | 91篇 |
1999年 | 91篇 |
1998年 | 4篇 |
1992年 | 148篇 |
1991年 | 193篇 |
1990年 | 158篇 |
1989年 | 220篇 |
1988年 | 174篇 |
1987年 | 177篇 |
1986年 | 170篇 |
1985年 | 166篇 |
1984年 | 126篇 |
1983年 | 115篇 |
1982年 | 41篇 |
1981年 | 30篇 |
1980年 | 48篇 |
1979年 | 121篇 |
1978年 | 110篇 |
1977年 | 93篇 |
1976年 | 87篇 |
1975年 | 130篇 |
1974年 | 145篇 |
1973年 | 147篇 |
1972年 | 162篇 |
1971年 | 154篇 |
1970年 | 151篇 |
1969年 | 137篇 |
1968年 | 120篇 |
1967年 | 129篇 |
1966年 | 110篇 |
1965年 | 89篇 |
1959年 | 44篇 |
1958年 | 94篇 |
1957年 | 79篇 |
1956年 | 62篇 |
1955年 | 57篇 |
1954年 | 44篇 |
1953年 | 13篇 |
1952年 | 14篇 |
排序方式: 共有5024条查询结果,搜索用时 15 毫秒
81.
L B Pinchuk Ia I Serkiz N K Rodionova G G Pukhova N A Druzhina G N Koval' A I Lipskaia V N Maslenny? S T Malinari 《Radiobiologiia》1991,31(5):635-641
It has been shown that rats born during the first months after the Chernobyl A.P.S. disaster exhibit essential changes in the peripheral blood and bone marrow haemopoiesis throughout the entire lifetime. Rats brought up in Chernobyl from the age of three months on display even more pronounced changes. It is assumed that the changes in the haemopoiesis develop due to the continuous influence of low-level radiation of different quality and are attributed to the effect of the incorporated radionuclides. 相似文献
82.
Recovery cycles of the auditory brainstem responses were studied in the bottle-nosed dolphin, Tursiops truncatus, using paired acoustic clicks. The recovery time was longer if both clicks had identical spectra (50% recovery at 0.9 ms), as compared with that of different spectra (50% recovery at 0.35 ms). These results can explain a different recovery time of evoked responses after an artificial sound and after own locating one. 相似文献
83.
A Ia Avanov 《Bioorganicheskaia khimiia》1991,17(7):937-944
Theoretical conformational analysis of C-terminal fragments of tachykinin peptides with a common amino acid sequence Asx-Xaa-Phe-Yaa-Gly-Leu-Met-NH2 suggested the conformational states to be independent of the nature of Xaa and Yaa residues. It is shown that among plausible spatial forms of the C-terminal fragments an alpha-helix with the hydrophobic coat consisted of identically oriented side chains is energetically the most stable structure. The preference of this conformation for tachykinins functioning is discussed. 相似文献
84.
I V Smirnov G Ia Tseneva L A Mitrikova 《Molekuliarnaia genetika, mikrobiologiia i virusologiia》1991,(3):19-21
The dispersion of plasmid pYV associated virulence markers in 474 Yersinia strains isolated from people has been studied. The ability to autoagglutination, calcium dependence of growth and the specific antigens were identified in 157 strains of traditionally pathogenic Yersinia enterocolitica serovars 03, 09, Yersinia pseudotuberculosis serovar I. They were not found in 223 strains of other 12 serovars of Yersinia enterocolitica, in 40 strains of Yersinia frederiksenii, Yersinia kristensenii, Yersinia intermedia. The proportion of virulent clones in the population of Yersinia is noted to depend on the conditions of its existence in vivo or in vitro. Identification of virulence markers is acknowledged to be expedient in epidemiological and ethiological estimation of the role of isolated Yersinia strains. 相似文献
85.
86.
Ia R Matsiuk 《Arkhiv anatomii, gistologii i émbriologii》1986,91(8):35-42
In 260 male white rats electron microscopically, cytochemically with biochemical estimation of proteolitic activity of gastric juice, it has been demonstrated that principle cells of the gastric glands, after injection of small doses of hydrocorticone, respond with a complex of adequate ultrastructural, cytochemical and functional changes directed to realization of the drugs stimulating effect. With increasing time of the experiment, or the doses, progressively developing distrophic processes, involving predominantly the protein-synthesizing apparatus and, to a less degree, the mitochondrial mechanism, are observed in the principle cells. This results in inhibition of the pepsinogene synthesis phase and in decreasing proteolytic activity of gastric juice. Reaction of the principle cells is independent on testosterone doses; the protein-synthesizing and mitochondrial (to a less degree) apparatuses develop; the pepsinogene extrusion phase is suppressed; it results in its deposition in cytoplasm and in decreasing proteolytic activity of gastric juice. When testosterone and hydrocortisone are injected simultaneously in small doses, the stimulating effect of hydrocortisone to the principle cells is abolished and at large doses it is sharply manifested and is not accompanied with destructive changes in the principle cells. 相似文献
87.
Various concentrations of exogenous L and D-tryptophan as well as of their analogue D,L-6-methyltryptophan were added to the growth medium of Penicillium sizovae during its inoculation and after the active growth of the fungus was over. The authors studied the effect of these compounds on the accumulation of exocellular alkaloids and biomass as well as on the synthesis of proteins, the content of free tryptophan in the cells, and the activity of tryptophan synthetase. As was shown in experiments using labeled tryptophan, this amino acid is a direct precursor of alkaloids in the culture. 相似文献
88.
89.
The study on the kanamycin resistance determinant (Kanr) in an oxytetracycline--producing strain of S. rimosus showed that it was capable of amplifying in the chromosome during selection for increasing the antibiotic resistance level. The amplification of the DNA fragment with a molecular weight of 10.3 MDa containing Kanr amounted to 300 copies per genome, which resulted in a more than 1000-fold increase in kanamycin resistance level. Cloning of the Kanr determinant on plasmid SLP1.2 in S. lividans strain 66 was performed. In Streptomyces lividans strain 66 the Kanr determinant preserved the capacity for amplification in the hybrid plasmid pSU10 integrated into the chromosome. The Kanr determinant in the strains of S. rimosus and S. lividans was characterized by transfers Kanr in equilibrium Kans with a frequency of 1 X 10(-3). It was shown that the mutation in S. lividans strain 66 resulting in phenotype Kans was not connected with the structural Kanr gene on plasmid pSU10 but was localized on the chromosome. Phenotype Kans was promoted by a decrease in the number of the copies of the regulatory genetic element designated RES1. The reverse to phenotype Kanr might be due to one of the following events: amplification to the initial level of RES1 and amplification up to 200 copies per the genome of the hybrid plasmid pSU10 containing the Kanr determinant. Amplification of the Kanr determinant with preserved initial level of RES1 element resulted in a more than 1000 times increase in the resistance level. 相似文献
90.
Temperature dependence of spin-spin proton relaxation times of DNA and bound water and the content of bound water in the samples of DNA, saturated with water in the atmosphere with different relative humidities from 0 to 100% were studied by means of pulsed NMR. It is shown that the temperature transition in the system of DNA-bound water in the interval 18-35 degrees is observed only when the relative humidity is more than 70% and the double-stranded structure of DNA exists. The transition of DNA from one conformation into another passes through some intermediate state more labile and probably less ordered. This transition is accompanied by changes in the structure of the hydration shell. In the case when relative humidity is greater than 80%, the partial dehydration of DNA stimulated by the transition is observed. This dehydration increases with the increase of relative humidity. 相似文献