全文获取类型
收费全文 | 879610篇 |
免费 | 100708篇 |
国内免费 | 567篇 |
专业分类
980885篇 |
出版年
2018年 | 8115篇 |
2017年 | 7674篇 |
2016年 | 11100篇 |
2015年 | 15080篇 |
2014年 | 17572篇 |
2013年 | 25276篇 |
2012年 | 28328篇 |
2011年 | 28821篇 |
2010年 | 19384篇 |
2009年 | 17900篇 |
2008年 | 25306篇 |
2007年 | 26172篇 |
2006年 | 24127篇 |
2005年 | 23434篇 |
2004年 | 23162篇 |
2003年 | 22059篇 |
2002年 | 21219篇 |
2001年 | 42254篇 |
2000年 | 42381篇 |
1999年 | 33516篇 |
1998年 | 11438篇 |
1997年 | 12057篇 |
1996年 | 11392篇 |
1995年 | 10454篇 |
1994年 | 10357篇 |
1993年 | 10207篇 |
1992年 | 26923篇 |
1991年 | 25799篇 |
1990年 | 24975篇 |
1989年 | 24545篇 |
1988年 | 22296篇 |
1987年 | 21169篇 |
1986年 | 19651篇 |
1985年 | 19278篇 |
1984年 | 16098篇 |
1983年 | 13619篇 |
1982年 | 10428篇 |
1981年 | 9457篇 |
1980年 | 8908篇 |
1979年 | 15167篇 |
1978年 | 11592篇 |
1977年 | 10723篇 |
1976年 | 9824篇 |
1975年 | 10683篇 |
1974年 | 11571篇 |
1973年 | 11297篇 |
1972年 | 10261篇 |
1971年 | 9421篇 |
1970年 | 8007篇 |
1969年 | 7680篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
973.
The genetic diversity at the ELA DQβ locus was investigated using polymerase chain reaction and DNA sequencing. Based upon serological methods 16 class II homozygous animals were selected and their genomic DNA was used. A DQβ gene from an equine cDNA library was also sequenced. Our methology and the similarity between the genomic and the cDNA sequences suggest that the studied locus is expressed on equine lymphocytes. In the predicted amino acid sequence the most extensive variation is located at residues 56–60. The pattern of these five amino acids is strongly correlated to the serological ELA class II specificities (W13, W22, W23, Be200). The alleles corresponding to the W23 specificity are the most divergent among the equine DQβ alleles and also from other mammalian DQβ sequences. 相似文献
974.
C M Woolf 《The Journal of heredity》1991,82(2):167-169
Common white facial and leg markings have a multifactorial mode of inheritance in Equus caballus. Evidence for the complexity of the genetic component is the observation that chestnut (e/e) horses have more extensive white markings than do bay (E/-) horses. Computerized records obtained from the Arabian Horse Registry of America, Inc., were used to determine if heterozygous (E/e) bay horses have more extensive white facial markings than do homozygous (E/E) bay horses. Thirty-five sire families were analyzed. Each sire family consists of a sire, his foals, and the dams of those foals. The facial region was divided into five areas, and each horse was given a score from 0 to 5 according to the number of areas with whiteness. Since dams and foals with E/E genotypes cannot be identified in these sire families, mean facial scores were compared in dams and foals that were E/e and E/-. It was assumed that if a difference exists between E/e and E/E horses, the presence of E/E horses in the E/- group would reduce the mean of the E/- group. The results show that Arabian horses with the genotype E/e have more white markings than do horses with the genotype E/-, leading to the conclusion that horses with the genotypes e/e, E/e, and E/E vary as to the quantitative expression of white facial markings, with heterozygotes having an intermediate expression. 相似文献
975.
976.
The effects of Heterosigma akashiwo on juvenile Oncorhynchus tshawytscha and its implications for fish culture 总被引:2,自引:0,他引:2
E. A. Black J.N. C. Whyth J. W. Bagshaw N. G. Ginther 《Zeitschrift fur angewandte Ichthyologie》1991,7(3):168-175
The effects of natural blooms of Heterosigma akashiwo on freshwater-and saltwater-acclimated juvenile chinook salmon were assessed. Rates of fish mortality in the blooms were independent of acclimation of fish to seawater and the ambient oxygen levels, but were dependent on concentration of algae and ambient water temperatures. No pathological abnormality to gills or other internal organs in the fish were evident. Aeration or oxygenation of fish cages did not enhance or inhibit fish survival in a H. akashiwo bloom. Cause of death was considered to be due to a labile ichthyotoxic agent. 相似文献
977.
A psychological test battery comprising reasoning ability, name and number checking, letter cancellation and associative recall was administered to a group of 70 student nurses at 2-hr intervals from 0800 to 2000 to determine if their performance varied at different times of day. Simultaneously, their oral temperature was recorded. A 7 x 7 latin square design was utilized, and latin square repeated measure analysis of variance was employed. The results indicated variations in oral temperature as the day advanced. While accuracy of performance in cognitive tasks was found to be superior during the early morning, noon or early evening hours, the speed of performance was highest during the period from late-morning to late-evening. 相似文献
978.
New gene assignments using a complete, characterized sheep-hamster somatic cell hybrid panel 总被引:4,自引:0,他引:4
The generation and characterization of new sheep-hamster cell hybrids is reported from the fusion of sheep white blood cells with six different hamster auxotrophs. Selection from these and previously generated cell hybrids has led to the production of a panel of 30 hybrids covering the complete sheep genome of 28 chromosomes. Over half of the cell hybrids in this panel contain single sheep chromosomes. By complementation, the following new assignments have been made using the panel: phosphoribosyl N-formylglycinamide amidotransferase (PRFGA) to sheep chromosome (chr) 11; adenylosuccinate synthetase (ADSS) to sheep chr 12; adenylosuccinate lyase (ADSL) to sheep chr 3q; 3-hydroxy-3-methylglutaryl-coenzyme A synthase (HMGCS) to sheep chr 16; dihydrofolate reductase (DHFR) to sheep chr 5; and adenine phosphoribosyltransferase (APRT) to sheep chr 14. The gene phosphoribosylaminoinidazole-carboxamide formyltransferase/Inosinicase (PRACFT) has now been regionally assigned to chr 2q. By isozyme analysis, phosphogluconate dehydrogenase (PGD) was assigned to sheep chr 12, anchoring the sheep syntenic group U1 to this chromosome, and mannose phosphate isomerase (MPI) was assigned to sheep chr 18. Furthermore, the chromosomal assignment of 110 microsatellites was confirmed using this cell panel. 相似文献
979.
The protein–nanomaterial interface 总被引:1,自引:1,他引:0
980.
Jeff A Johnson Heather RL Lerner Pamela C Rasmussen David P Mindell 《BMC evolutionary biology》2006,6(1):65-12