全文获取类型
收费全文 | 27231篇 |
免费 | 2201篇 |
国内免费 | 1698篇 |
出版年
2024年 | 45篇 |
2023年 | 215篇 |
2022年 | 502篇 |
2021年 | 888篇 |
2020年 | 638篇 |
2019年 | 882篇 |
2018年 | 950篇 |
2017年 | 730篇 |
2016年 | 1089篇 |
2015年 | 1586篇 |
2014年 | 1917篇 |
2013年 | 1976篇 |
2012年 | 2569篇 |
2011年 | 2430篇 |
2010年 | 1527篇 |
2009年 | 1278篇 |
2008年 | 1786篇 |
2007年 | 1581篇 |
2006年 | 1358篇 |
2005年 | 1235篇 |
2004年 | 1116篇 |
2003年 | 963篇 |
2002年 | 855篇 |
2001年 | 567篇 |
2000年 | 514篇 |
1999年 | 416篇 |
1998年 | 223篇 |
1997年 | 177篇 |
1996年 | 111篇 |
1995年 | 103篇 |
1994年 | 93篇 |
1993年 | 60篇 |
1992年 | 122篇 |
1991年 | 85篇 |
1990年 | 77篇 |
1989年 | 70篇 |
1988年 | 44篇 |
1987年 | 41篇 |
1986年 | 37篇 |
1985年 | 36篇 |
1984年 | 21篇 |
1983年 | 23篇 |
1982年 | 18篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 15篇 |
1978年 | 18篇 |
1975年 | 19篇 |
1974年 | 16篇 |
1970年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
A single amino acid substitution in v-erbB confers a thermolabile phenotype to ts167 avian erythroblastosis virus-transformed erythroid cells. 总被引:18,自引:5,他引:13 下载免费PDF全文
A library of recombinant bacteriophage was prepared from ts167 avian erythroblastosis virus-transformed erythroid precursor cells (HD6), and integrated proviruses from three distinct genomic loci were isolated. A subclone of one of these proviruses (pAEV1) was shown to confer temperature-sensitive release from transformation of erythroid precursor cells in vitro. The predicted amino acid sequence of the v-erbB polypeptide from the mutant had a single amino acid change when compared with the wild-type parental virus. When the wild-type amino acid was introduced into the temperature-sensitive avian erythroblastosis virus provirus in pAEV1, all erythroid clones produced in vitro were phenotypically wild type. The mutation is a change from a histidine to an aspartic acid in the temperature-sensitive v-erbB polypeptide. It is located in the center of the tyrosine-specific protein kinase domain and corresponds to amino acid position 826 of the human epidermal growth factor receptor sequence. 相似文献
53.
Clastogen-induced chromosomal breakage as a marker for first trimester prenatal diagnosis of Fanconi anemia 总被引:5,自引:0,他引:5
Arleen D. Auerbach Zhang Min Rita Ghosh Eugene Pergament Yuri Verlinsky Henriette Nicolas Joëlle Boué 《Human genetics》1986,73(1):86-88
Summary Using cultured trophoblast cells obtained by chorionic villus biopsy, we diagnosed Fanconi anemia (FA) in two pregnancies and excluded it in eight pregnancies at risk for the syndrome. Baseline chromosomal breakage and breakage induced by diepoxybutane (DEB) were analyzed. Increased breakage was used as a marker for the syndrome. Our results were unambiguous and provide a reliable method for prenatal detection of FA in the first trimester of pregnancy. 相似文献
54.
The nucleotide sequence of the embryonic chicken beta-type globin genes 总被引:11,自引:0,他引:11
J B Dodgson S J Stadt O R Choi M Dolan H D Fischer J D Engel 《The Journal of biological chemistry》1983,258(20):12685-12692
55.
Low-molecular-weight nuclear RNAs 总被引:2,自引:0,他引:2
56.
A group of 16 German Landrace sows, nursing 155 piglets, was used for the demonstration of the effect of 20 mg of the progestogen megestrol acetate, administered orally from Day 8 to 21 post-partum, on milk production, milk composition and piglet weight. Eight sows remained untreated. Megestrol acetate treatment increased significantly milk yield by 35% and piglet weight at weaning (Day 35) by 30% over controls. A carryover effect after cessation of drug treatment was dtected, which kept milk production at an increased level for 8 more days. 相似文献
57.
Strains of coagulase-positive staphylococci which were nontypable with the routine typing set of phages could be typed by lysogeny with phage-propagating strains as indicators and with ultraviolet induction. About 10% of the strains could be typed without induction. About 36% of them could be typed by this method when ultraviolet irradiation was used as an inducing agent. The phage groups from which the majority of the nontypable staphylococci originated were easily identified by this method of typing. 相似文献
58.
The assay of yeast ureidoglycolatase 总被引:6,自引:0,他引:6
59.
The work is concerned with the question of the effect of humic acids on the biological action of agropyrene, the effective substance from the rootstock of Agropyron repens (L.) P. BEAUV. The test organism was the alga Scenedesmus obliquus (TURP.) KRÜGER, cultivated in mineral solution. The basic biological test was the determination of the number and size of the cells of this alga. It was found that the way in which agropyrene acts on combined application with humus acids depends on which humus fraction is used. It can display a synergic action if humic acid is used, since this substance probably facilitates the penetration of agropyrene into the cells. On the other hand, fulvic acid counteracts the activity of agropyrene and this most probably by mutual binding and blocking of active groups and links. 相似文献
60.