全文获取类型
收费全文 | 6216篇 |
免费 | 480篇 |
国内免费 | 1篇 |
出版年
2023年 | 30篇 |
2022年 | 52篇 |
2021年 | 152篇 |
2020年 | 89篇 |
2019年 | 148篇 |
2018年 | 193篇 |
2017年 | 187篇 |
2016年 | 278篇 |
2015年 | 309篇 |
2014年 | 387篇 |
2013年 | 454篇 |
2012年 | 474篇 |
2011年 | 495篇 |
2010年 | 334篇 |
2009年 | 249篇 |
2008年 | 378篇 |
2007年 | 317篇 |
2006年 | 269篇 |
2005年 | 283篇 |
2004年 | 223篇 |
2003年 | 239篇 |
2002年 | 183篇 |
2001年 | 87篇 |
2000年 | 89篇 |
1999年 | 73篇 |
1998年 | 54篇 |
1997年 | 37篇 |
1996年 | 31篇 |
1995年 | 32篇 |
1994年 | 25篇 |
1993年 | 31篇 |
1992年 | 51篇 |
1991年 | 31篇 |
1990年 | 32篇 |
1989年 | 45篇 |
1988年 | 45篇 |
1987年 | 22篇 |
1986年 | 33篇 |
1985年 | 23篇 |
1984年 | 13篇 |
1983年 | 20篇 |
1982年 | 18篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 21篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1974年 | 18篇 |
1973年 | 13篇 |
1967年 | 7篇 |
排序方式: 共有6697条查询结果,搜索用时 15 毫秒
31.
Characterization of Neurospora crassa cyclic AMP phosphodiesterase activated by calmodulin. 总被引:2,自引:1,他引:1
Activation of cyclic AMP phosphodiesterase I by brain or Neurospora calmodulin was studied. The stimulation required micromolar concentrations of Ca2+, and it was observed at cyclic AMP concentrations between 0.1 and 500 microM. Activation was blocked by EDTA and some neuroleptic drugs such as chlorpromazine and fluphenazine. These drugs inhibit the elongation of N. crassa wild-type aerial hyphae. These results reinforce the evidence towards the recognition of Ca2+-calmodulin as one of the systems controlling cyclic nucleotide concentrations in Neurospora. 相似文献
32.
Dion tomasellii sp. nov. occurs with an interrupted distribution from Guerrero to central Sonora. It is characterized by falcate to subfalcate leaflets. The populations from Sonora and northern Sinaloa are segregated asD. tomasellii var.sonorense on the basis of their narrower and glaucous leaflets. 相似文献
33.
The activity of antidromically identified abducens nucleus motoneurons and inter-nuclear neurons has been recorded during saccadic eye movements in the alert cat. The activity of these neurons has been demonstrated to be the sum of a velocity component proportional to eye velocity plus a position component proportional to instantaneous eye position during the movement. Results are discussed in relation to proposed models about the generation of saccadic eye movements. 相似文献
34.
35.
Isolation of yeast with killer activity and its breeding with an industrial baking strain by protoplast fusion 总被引:5,自引:0,他引:5
Adela Bortol Clara Nudel Elda Fraile Ramon de Torres Ana Giulietti J. F. T. Spencer Dorothy Spencer 《Applied microbiology and biotechnology》1986,24(5):414-416
Summary Wild strains of Saccharomyces cerevisiae were isolated from dairy products, bakery goods, fresh fruit and vegetables, and tested for killer activity. Four isolates out of 238 strains possessed killer activity. The best of these was converted to the petite form and hybridized with an industrial strain of Saccharomyces cerevisiae by protoplast fusion. Thirty-eight out of 104 isolates had killer activity, and some of these had good dough-raising activity as well. 相似文献
36.
Summary An isochromosome of 15(q12) was found in a mentally retarded patient with behaviour disorders which included hyperactivity, short attention span, aggression, and autistic behaviour. There were only minor physical anomalies; he did not have the Prader-Willi syndrome. 相似文献
37.
Jan Lindgren Magdalena Blaszczyk Barbara Atkinson Zenon Steplewski Hilary Koprowski 《Cancer immunology, immunotherapy : CII》1986,22(1):1-7
Summary Over 600 hybridomas were derived from the immunization of mice with live cells and aqueous extracts of the human prostatic carcinoma cell line PC3. A total of 26 hybridomas with restricted reactivities were selected, subcloned and antibodies tested on a variety of tumor and normal cells. Seven monoclonal antibodies showed reactivity for prostate cancer and other tumor cell lines, including breast carcinomas. Three of the antibodies obtained after immunization with live cells reacted with live cells only and three of the four antibodies obtained after immunization with cell extract reacted with cell extracts and spent culture media. The fourth antibody in the latter group was reactive only in the immunoperoxidase staining assay. Antibody PrS5 recognized a 90,000 molecular weight molecule from 125I-surface-labeled cells in immunoprecipitation analysis. Antibodies PrE3 and PrD8 detected a nonacid glycolipid pentasaccharide from PC3 cells and meconium, and a glycoprotein of 115,000 molecular weight from 125I-surface-labeled red blood cells. The similar patterns of reactivity in RIAs and antigen analysis suggest that antibodies PrE3 and PrD8 recognize the same molecule. The results emphasize the usefulness of immunohistochemistry in the testing of monoclonal antibodies and the impact of the form in which the antigen is presented on the resultant antibody specificity 相似文献
38.
Stability of plasmids R1-19 and R100 in hyper-recombinant Escherichia coli strains and in Salmonella typhimurium strains. 总被引:2,自引:1,他引:1
Plasmids R1-19 and R100 dissociate in hyper-recominant Escherichia coli strains in a way that is similar to but slower than dissociation in Salmonella typhimurium. The results presented suggest that the molecular mechanism for plasmid dissociation in hyper-recombinant E. coli strains is different than that in S. typhimurium strains. 相似文献
39.
Luis Molina y Vedia Mónica Torruella Ricardo Attar Ernesto Podesta Juan A. Reig Mirtha M. Flawia Héctor N. Torres 《Biochemical and biophysical research communications》1983,113(3):778-783
A monoclonal antibody against soluble adenylate cyclase was obtained. The antibody inhibits cyclase activities from several lower eucaryotic organisms but not activities associated to testicular cytosol or turkey erythrocyte membranes. 相似文献
40.
Andrew M. Torres 《American journal of botany》1968,55(5):582-589
The karyotypes of the three diploid (n = 10) species of the subg. Diplothrix (Zinnia—Compositae) were compared to determine whether there were any demonstrable differences which could then be sought in their polyploid derivatives. Because many of the chromosomes in a set were too similar to distinguish confidently between them, a method of analysis was developed which measures the similarity of whole sets of chromosomes rather than individual ones. The method consists of measuring the distances between graph-plotted vertices representing arm lengths of chromosomes of real or paper hybrids and then comparing these distances by means of U tests with those similarly derived for the “parents.” This procedure obviates the need of attempting to identify morphologues (morphologically similar chromosomes) in a somatic diploid root-tip cell and to equate corresponding pairs of chromosomes from different cells of a single plant or from different species or hybrids. No demonstrable differences in the karyotypes of diploid cespitose zinnias were found. Analysis of previously published data by this method indicated that there has been a general non-objectivity and non-operationalism in the determination of homologous chromosomes, and a general but unwarranted assumption that morphologues are in reality genologues (genetically corresponding chromosomes). 相似文献