全文获取类型
收费全文 | 2797篇 |
免费 | 245篇 |
国内免费 | 8篇 |
出版年
2021年 | 40篇 |
2020年 | 23篇 |
2019年 | 31篇 |
2018年 | 43篇 |
2017年 | 22篇 |
2016年 | 52篇 |
2015年 | 121篇 |
2014年 | 125篇 |
2013年 | 146篇 |
2012年 | 196篇 |
2011年 | 199篇 |
2010年 | 111篇 |
2009年 | 98篇 |
2008年 | 141篇 |
2007年 | 136篇 |
2006年 | 160篇 |
2005年 | 149篇 |
2004年 | 141篇 |
2003年 | 109篇 |
2002年 | 81篇 |
2001年 | 83篇 |
2000年 | 83篇 |
1999年 | 69篇 |
1998年 | 32篇 |
1997年 | 28篇 |
1996年 | 20篇 |
1995年 | 23篇 |
1994年 | 22篇 |
1993年 | 19篇 |
1992年 | 58篇 |
1991年 | 36篇 |
1990年 | 38篇 |
1989年 | 43篇 |
1988年 | 29篇 |
1987年 | 29篇 |
1986年 | 31篇 |
1985年 | 35篇 |
1984年 | 20篇 |
1983年 | 31篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 21篇 |
1978年 | 11篇 |
1977年 | 18篇 |
1976年 | 12篇 |
1975年 | 11篇 |
1974年 | 10篇 |
1972年 | 21篇 |
1971年 | 16篇 |
排序方式: 共有3050条查询结果,搜索用时 468 毫秒
41.
C K Chou T S Su C M Chang C P Hu M Y Huang C S Suen N W Chou L P Ting 《The Journal of biological chemistry》1989,264(26):15304-15308
The human hepatoma Hep3B cells contain integrated hepatitis B viral genome and continually secret hepatitis B surface antigen (HBsAg). The production of HBsAg (but not alpha-fetoprotein) was suppressed by addition of low concentrations (0.1-1 nM) of insulin into serum-free medium. In addition, the suppression of HBsAg production by insulin was paralleled with the decrease in HBsAg mRNA abundance. Insulin also cause a rapid rate of disappearance of HBsAg mRNA (t 1/2, 2 h) in Hep3B cells. The Hep3B cells carry specific receptor with high affinity for insulin (Kd = 1.8 nM). The receptor showed an insulin-dependent protein tyrosine kinase activity. The half-maximal insulin concentration for the activation of the receptor kinase was about 5 nM. Only very high concentrations of insulin-like growth factor I and human proinsulin can compete for the insulin receptor binding and suppress HBsAg production, this suggests that insulin may act through its receptor binding to suppress HBsAg expression in human hepatoma Hep3B cells. 相似文献
42.
43.
亚洲薄荷的两个化学型 总被引:2,自引:0,他引:2
周荣汉 《植物资源与环境学报》1994,3(3):58-59
亚洲薄荷的两个化学型桂新,周荣汉(安徽中医学院中药系合肥230038)(中国药科大学植物化学分类研究室南京210038)TwochemotypesofMenthaasiaficaBoriss¥ChouGui-Xin(AnhuiCollegeofTra... 相似文献
44.
Murine monoclonal antibodies specific for conserved and non-conserved antigenic determinants of the human and murine Ku autoantigens 总被引:5,自引:0,他引:5
45.
周荣汉 《植物资源与环境学报》1993,2(3):55-57
兴安薄荷(Mentha dahurica Fisch.ex Benth.)为唇形科薄荷属(Mentha L.)多年生草本植物,产于我国黑龙江、吉林、内蒙古东北部。俄罗斯远东地区以及日本北方也有分布。在我国东北有作中药薄荷入药的。其化学成分研究甚少,仅俄国Pulatova报道其含有香豆素类成分。为开发利用我国薄荷植物资源,作者对全国薄荷属植物进行了野外调查,并对其资源、生物学性状、孢粉学和化学等进行了较系统的研究,现仅就兴安薄荷挥发油中化学成分分析结果作一报道。 相似文献
46.
Rui Yan Mark Ottenbreit Bharati Hukku Michael Mally Sharong Chou Joseph Kaplan 《In vitro cellular & developmental biology. Animal》1996,32(10):656-662
Summary Methods for monitoring cell line identification and authentication include species-specific immunofluorescence, isoenzyme
phenotyping, chromosome analysis, and DNA fingerprinting. Most previous studies of DNA fingerprinting of cell lines have used
restriction fragment length polymorphism analysis. In this study, we examined the utility of an alternative and simpler method
of cell line DNA fingerprinting—polymerase chain reaction (PCR) amplification of fragment length polymorphisms. Fourteen human
cell lines previously found by other methods to be either related or disparate were subjected to DNA fingerprinting by PCR
amplification of selected fragment length polymorphism loci. Cell identification patterns by this method were concordant with
those obtained by isoenzyme phenotyping and restriction fragment length polymorphism-DNA fingerprinting, and were reproducible
within and between assays on different DNA extracts of the same cell line. High precision was achieved with electrophoretic
separation of amplified DNA products on high resolution agarose or polyacrylamide gels, and with fragment length polymorphism
(FLP) loci-specific “allelic ladders” to identify individual FLP alleles. Determination of the composite fingerprint of a
cell line at six appropriately chosen fragment length polymorphism loci should achieve a minimum discrimination power of 0.999.
The ability of PCR-based fragment length polymorphism DNA fingerprinting to precisely and accurately identify the alleles
of different human cell lines at multiple polymorphic fragment length polymorphism loci demonstrates the feasibility of developing
a cell line DNA fingerprint reference database as a powerful additional tool for future cell line identification and authentication. 相似文献
47.
48.
H. B. Lee J. Guillaume R. Chou G. Cuzon H. H. Heng J. Fuchs 《Zeitschrift fur angewandte Ichthyologie》1995,11(3-4):302-308
This paper describes the effort of the Marine Aquaculture Section of the Primary Production Department in Singapore and the Institut Francais de Recherche pour l'Exploitation de la Mer in developing adequate facilities for fish nutritional requirement studies in Singapore, and in introducing appropriate nutritional methodology so that results are reliable and accurate. One of the first achievements was the demonstration of homogeneous fish (tropical seabass, Lates calcarifer Bloch) growth response in a newly established tank system before any nutritional experiments were initiated. The application of statistical procedures that take into consideration the power of a test and number of replications required has allowed for more accurate interpretation of results. This can be seen in the results of the first nutritional requirement experiment on the optimal dietary protein level of the seabass at constant energy. 相似文献
49.
Comparison of Germline Mosaics of Genes in the Polycomb Group of Drosophila Melanogaster 总被引:7,自引:0,他引:7 下载免费PDF全文
The genes of the Polycomb group (PcG) repress the genes of the bithorax and Antennapedia complexes, among others. To observe a null phenotype for a PcG gene, one must remove its maternal as well as zygotic contribution to the embryo. Five members of the PcG group are compared here: Enhancer of Polycomb [E(Pc)], Additional sex combs (Asx), Posterior sex combs (Psc), Suppressor of zeste 2 [Su(z)2] and Polycomblike (Pcl). The yeast recombinase (FLP) system was used to induce mitotic recombination in the maternal germline. Mutant embryos were analyzed by staining with antibodies against six target genes of the PcG. The loss of the maternal component leads to enhanced homeotic phenotypes and to unique patterns of misexpression. E(Pc) and Su(z)2 mutations had only subtle effects on the target genes, even when the maternal contributions were removed. Asx and Pcl mutants show derepression of the targets only in specific cell types. Psc shows unusual effects on two of the targets, Ultrabithorax and abdominal-A. These results show that the PcG genes do not act only in a common complex or pathway; they must have some independent functions. 相似文献
50.
A link between increased transforming activity of lymphoma-derived MYC mutant alleles, their defective regulation by p107, and altered phosphorylation of the c-Myc transactivation domain. 总被引:5,自引:4,他引:1 下载免费PDF全文
A T Hoang B Lutterbach B C Lewis T Yano T Y Chou J F Barrett M Raffeld S R Hann C V Dang 《Molecular and cellular biology》1995,15(8):4031-4042