全文获取类型
收费全文 | 1423篇 |
免费 | 194篇 |
专业分类
1617篇 |
出版年
2021年 | 20篇 |
2020年 | 12篇 |
2018年 | 16篇 |
2016年 | 22篇 |
2015年 | 42篇 |
2014年 | 54篇 |
2013年 | 63篇 |
2012年 | 75篇 |
2011年 | 80篇 |
2010年 | 48篇 |
2009年 | 46篇 |
2008年 | 60篇 |
2007年 | 59篇 |
2006年 | 53篇 |
2005年 | 59篇 |
2004年 | 60篇 |
2003年 | 51篇 |
2002年 | 60篇 |
2001年 | 13篇 |
2000年 | 16篇 |
1999年 | 16篇 |
1998年 | 28篇 |
1997年 | 18篇 |
1996年 | 12篇 |
1995年 | 12篇 |
1994年 | 17篇 |
1992年 | 14篇 |
1991年 | 20篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 17篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1984年 | 15篇 |
1983年 | 17篇 |
1982年 | 17篇 |
1981年 | 25篇 |
1980年 | 18篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1976年 | 17篇 |
1974年 | 14篇 |
1973年 | 16篇 |
1971年 | 14篇 |
1970年 | 13篇 |
1969年 | 15篇 |
1968年 | 18篇 |
1967年 | 12篇 |
1964年 | 16篇 |
1963年 | 15篇 |
排序方式: 共有1617条查询结果,搜索用时 0 毫秒
1.
2.
Dorothy Trainor 《CMAJ》1982,126(10):1235-1237
3.
The 13C NMR spectra of geosmin, selina-4(14),7(11)-diene-99-ol and two dihydroeudesmol isomers have been obtained and the individual resonances assigned. Several different empirical correlations developed by others have been combined in simple calculations to predict chemical shift values for sesquiterpenols of the eudesmane group. 相似文献
4.
5.
p82H identifies sequences at every human centromere 总被引:7,自引:3,他引:4
Carmen Aleixandre Dorothy A. Miller Arthur R. Mitchell Dorothy A. Warburton Steven L. Gersen Christine Disteche Orlando J. Miller 《Human genetics》1987,77(1):46-50
Summary A cloned alphoid sequence, p82H, hybridizes in situ to the centromere of every human chromosome. After washing under stringent conditions, no more than 8% of the grains are located on any specific chromosome. p82H thus differs from other centromeric sequences which are reported to be chromosome specific, because it detects sequences that are conserved among the chromosomes. Two experimental approaches show that the p82H sequences are closely associated with the centromere. First, p82H remains with the relocated centromeres in an inv(19) and an inv(6) chromosome. Second, p82H hybridizes at the centromere but not to the centromeric heterochromatin of chromosomes 1, 9 and 16 that have elongated 1qh, 9qh and 16qh regions produced by short growth in 5-azacytidine. The only noncentromeric site of hybridization is at the distal end of the 9qh region. 相似文献
6.
Chromosome-specific subsets of human alphoid DNA identified by a chromosome 2-derived clone 总被引:3,自引:0,他引:3
Mariano Rocchi Antonio Baldini Nicoletta Archidiacono Shabnam Lainwala Orlando J. Miller Dorothy A. Miller 《Genomics》1990,8(4):705-709
We have cloned an alphoid DNA fragment, pBS4D, from the DNA of a human-hamster hybrid cell line containing chromosome 2 as its only cytologically detectable human component. Under high stringency conditions, pBS4D hybridized in situ mostly to chromosome 2 and to a lesser extent to chromosomes 18 and 20. Restriction analysis using the DNA from selected somatic hybrid cell lines revealed that the genomic organization of this alphoid DNA differs on each of these three chromosomes. 相似文献
7.
Mitochondrial DNA from the fall armyworm, Spodoptera frugiperda (J.E. Smith), was cloned and characterized using restriction enzyme mapping. Genome size is approximately 16.3 kilobase (Kb), consistent with that of most animals. Three fragments, 8.1 Kb, 6.2 Kb, and 2.0 Kb, were produced by digestion with restriction enzyme Xbal and cloned into a pUC19 vector. Twenty-nine restriction enzymes were used to generate a detailed physical restriction enzyme map of the three cloned fragments. These data represent the first detailed characterization of a lepidopteran mitochondrial genome. © 1992 Wiley-Liss, Inc. 相似文献
8.
We used reagents specific for serine-dependent proteinases to verify that a proteinase of this class is necessary for natural cytotoxicity (NK). NK was inhibited by phenylmethylsulfonylfluoride (PMSF), by diisopropylfluorophosphate (DFP), and by the plasma antiproteinase alpha-1-antichymotrypsin (alpha-1-X), all of which are specific for serine-dependent proteinases. Substrate specificity was then determined on the basis of the specificity of the plasma and fungal anti-proteinases and synthetic alternate substrates that affected NK. alpha-1-X, which inhibits only serine proteinases with aromatic amino acid specificity, blocked NK. Chymostatin, but not other fungal inhibitors, also blocked NK activity. Furthermore, the only synthetic substrates that effectively reduced NK were those derived from aromatic amino acids. The ester derivatives of these substrates inhibited NK better than the amides. NK inhibition with these alternate substrates was also stereospecific, with the L forms twofold more active than the D forms. These reagents did not block initial lymphocyte-target cell binding. Therefore we propose that the "NK-proteinase" is involved in either the initiation of cytolysis, perhaps as part of stimulus and secretion of cytolytic molecules, or in the cascade of events that may lead to the formation of final lytic substance. 相似文献
9.
James W. Truman Dorothy B. Rountree Shirley E. Reiss Lawrence M. Schwartz 《Journal of insect physiology》1983,29(12):895-900
The relationship between the ecdysteroid titre and eclosion hormone was explored for the pupal and adult ecdyses of Manduca sexta. Ecdysteroid treatment late during either moult caused a dosedependant delay in the time of ecdysis. Sensitivity to exogenous steroid treatment dropped off as the respective moults neared completion and in both cases coincided with the time of the low point in the endogenous ecdysteroid titre. It was concluded that an ecdysteroid decline is a normal prerequisite for the ecdyses of both stages. The steroid drop is important for two aspects of the eclosion hormone system: it causes target tissues to become sensitive to the peptide and it is a prerequisite for the subsequent release of eclosion hormone itself. Thus, the dual action of the declining ecdysteroid titre insures that when eclosion hormone is released, the tissues will be competent to respond to it. 相似文献
10.
The presence of serum in suspensions of Sendai-induced human leukocytes is necessary for the synthesis of significant amounts of interferon. Very little interferon is obtained from serum-free suspensions. Cow's milk or milk casein can substitute for serum in the production of high yields of human leukocyte interferon. 相似文献