全文获取类型
收费全文 | 246404篇 |
免费 | 22557篇 |
国内免费 | 260篇 |
专业分类
269221篇 |
出版年
2018年 | 2649篇 |
2017年 | 2586篇 |
2016年 | 3448篇 |
2015年 | 3696篇 |
2014年 | 4616篇 |
2013年 | 6696篇 |
2012年 | 7277篇 |
2011年 | 7962篇 |
2010年 | 5416篇 |
2009年 | 4825篇 |
2008年 | 6931篇 |
2007年 | 7154篇 |
2006年 | 6778篇 |
2005年 | 6473篇 |
2004年 | 6381篇 |
2003年 | 6219篇 |
2002年 | 6064篇 |
2001年 | 12046篇 |
2000年 | 12018篇 |
1999年 | 9190篇 |
1998年 | 2685篇 |
1997年 | 2758篇 |
1996年 | 2703篇 |
1995年 | 2489篇 |
1994年 | 2432篇 |
1993年 | 2331篇 |
1992年 | 7213篇 |
1991年 | 7014篇 |
1990年 | 7086篇 |
1989年 | 6879篇 |
1988年 | 6390篇 |
1987年 | 6045篇 |
1986年 | 5373篇 |
1985年 | 5690篇 |
1984年 | 4475篇 |
1983年 | 3871篇 |
1982年 | 2683篇 |
1981年 | 2501篇 |
1980年 | 2311篇 |
1979年 | 4125篇 |
1978年 | 3148篇 |
1977年 | 2896篇 |
1976年 | 2841篇 |
1975年 | 3281篇 |
1974年 | 3505篇 |
1973年 | 3532篇 |
1972年 | 3064篇 |
1971年 | 2850篇 |
1970年 | 2534篇 |
1969年 | 2307篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
911.
912.
N G Rambidi 《Bio Systems》1992,27(4):219-222
A new version of computing and information processing devices may result from major principles of information processing at molecular level. Non-discrete biomolecular computers based on these principles seems to be capable of solving problems of high computational complexity. One of the possible ways to implement these devices is based on biochemical non-linear dynamical systems. Means and ways to materialize biomolecular computers are discussed. 相似文献
913.
Mapping of the silver fox genes: assignments of the genes for ME1, ADK, PP, PEPA, GSR, MPI, and GOT1
T B Nesterova N B Rubtsov S M Zakian V G Matveeva A S Graphodatsky 《Cytogenetics and cell genetics》1991,56(2):125-127
Evidence is presented for the assignment of seven fox genes on the basis of the segregation data for chromosomes and enzymes of fox x Chinese hamster somatic cell hybrids. The chromosomal loci of the following enzyme genes were determined: ME1, VFU1; ADK and PP, VFU4; PEPA, VFU5; GSR, VFU7; and MPI and GOT1, VFU15. The localization of these genes now extends the fox genetic map to 22 mapped genes. Based on comparative analysis of mammalian genetic maps, karyotype evolution in Carnivora is discussed. 相似文献
914.
Rearrangement of Fusarium oxysporum retro- transposon skippy was induced by growth in the presence of potassium chlorate. Three fungal strains, one sensitive to chlorate (Co60) and two resistant to chlorate and deficient for nitrate reductase (Co65 and Co94), were studied by Southern analysis of their genomic DNA. Polymorphism was detected in their hybridization banding pattern, relative to the wild type grown in the absence of chlorate, using various enzymes with or without restriction sites within the retrotransposon. Results were consistent with the assumption that three different events had occurred in strain Co60: genomic amplification of skippy yielding tandem arrays of the element, generation of new skippy sequences, and deletion of skippy sequences. Amplification of Co60 genomic DNA using the polymerase chain reaction and divergent primers derived from the retrotransposon generated a new band, corresponding to one long terminal repeat plus flanking sequences, that was not present in the wild-type strain. Molecular analysis of nitrate reductase-deficient mutants showed that generation and deletion of skippy sequences, but not genomic amplification in tandem repeats, had occurred in their genomes. 相似文献
915.
916.
I V Bogdashin S N Udintsev N I Suslov 《Biulleten' eksperimental'no? biologii i meditsiny》1990,110(10):409-411
In experiments on Wistar rats the cytotoxic activity of NK on the 1, 2, 10 days after partial hepatectomy (PH) and the application of Rodiola extract (RE) was studied. After 5 injections of RE the NK activity in gut increased by 112%, and after 12 ones (towards the end of experiment) by 222% in the spleen. The decreasing of this index in a first day after PH in lung, liver and gut was shown to restore in these tissues to the end of experiment. The absence of NK cytotoxicity diminishing just after PH in all the tissues was shown in operated animals, receiving RE and the decreasing of this index was found only in the lungs (by 335%). 相似文献
917.
918.
J Chae M J Kim J H Goo S Collier D Gubb J Charlton P N Adler W J Park 《Development (Cambridge, England)》1999,126(23):5421-5429
The tissue polarity genes control the polarity of hairs, bristles and ommatidia in the adult epidermis of Drosophila. We report here the identification of a new tissue polarity gene named starry night (stan). Mutations in this essential gene alter the polarity of cuticular structures in all regions of the adult body. The detailed polarity phenotype of stan on the wing suggested that it is most likely a component of the frizzled (fz) pathway. Consistent with this hypothesis, stan appears to be downstream of and required for fz function. We molecularly cloned stan and found that it encodes a huge protocadherin containing nine cadherin motifs, four EGF-like motifs, two laminin G motifs, and seven transmembrane domains. This suggests that Stan functions in signal reception, perhaps together with Fz. 相似文献
919.
S. N. Perova 《Inland Water Biology》2008,1(4):371-379
The macrozoobenthos taxonomic composition in small karst lakes of Vladimir oblast is studied for the first time. In the structure
of bottom communities, 149 taxa one rank below the genus have been found. Chironomid larvae and other amphibiotic animals,
as well as oligochaetes, prevail. Most of them are species widely distributed in the surface waters of European Russia. The
highest macrozoobenthos species diversity was recorded in neutral lakes, and the lowest diversity was in lakes with weakly
acidic waters. 相似文献
920.
Yu. S. Ravkin S. M. Tsybulin S. G. Livanov K. V. Toropov V. N. Kuranova V. P. Starikov S. V. Chesnokova 《Contemporary Problems of Ecology》2008,1(5):568-573
For the entire territory of West Siberia, including its plain and mountainous parts, two maps were constructed for populations of amphibians together with reptiles, and of birds. Communities of these classes of vertebrates differ from one another in their spatial differentiation. The differences are demonstrated for the plain and mountainous territories considered jointly and separately. 相似文献