全文获取类型
收费全文 | 282篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 1篇 |
丛书文集 | 1篇 |
教育与普及 | 3篇 |
理论与方法论 | 1篇 |
现状及发展 | 51篇 |
研究方法 | 33篇 |
综合类 | 161篇 |
自然研究 | 33篇 |
出版年
2021年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2013年 | 1篇 |
2012年 | 9篇 |
2011年 | 42篇 |
2010年 | 2篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 16篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 5篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 1篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1972年 | 7篇 |
1971年 | 6篇 |
1970年 | 7篇 |
1969年 | 1篇 |
1968年 | 5篇 |
1967年 | 7篇 |
1966年 | 7篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有284条查询结果,搜索用时 12 毫秒
191.
Résumé Chez la rate, la dose de tryptophan pyrrolase fut augmentée du douxième au quinzième jour de gestation. L'activité de ces rates gravides ne changea pas quand leur nourriture fut modifiée. 相似文献
192.
在阐述大学生素质教育的内涵及其意义的基础上,分析了高校图书馆在大学生素质教育中的地位和作用以及所具有的优势,从加强藏书建设、营造良好环境、提高馆员素质等方面提出了高校图书馆开展大学生素质教育的措施。 相似文献
193.
194.
Mary E. Clark 《Cellular and molecular life sciences : CMLS》1964,20(5):292-293
Zusammenfassung Eine kritische Untersuchung verschiedener Methoden für anaerobe Gewebskultur zeigte, dass in den meisten Einrichtungen die Anwesenheit von Sauerstoff nicht ausgeschlossen werden kann. Eine Modifikation des standardisierten Kulturgefässes wurde entwickelt, die das Halten der Kulturen unter völligem Luftabschluss möglich macht. 相似文献
195.
196.
M J Chen B Holskin J Strickler J Gorniak M A Clark P J Johnson M Mitcho D Shalloway 《Nature》1987,330(6148):581-583
Tumour necrosis factor alpha (ref. 1), synthesized primarily by monocytes in response to various invasive agents, induces a wide variety of biological effects relevant to regulating cell growth and differentiation, including the selective killing of some tumour cells and the growth stimulation of some normal fibroblasts. As tumour necrosis factor (TNF) appears to kill tumour cells preferentially, we asked whether TNF sensitivity correlates with the expression of specific oncogene(s). If so, by examining the cellular target(s) of the oncogene product, it might be possible to identify specific factor(s) which mediate TNF action. By using an in vitro cytotoxicity assay with NIH 3T3 and Fisher BRK-derived cells expressing exogenously introduced oncogenes, we found that adenovirus E1A proteins induce susceptibility to TNF killing. 相似文献
197.
Production of pharmaceutical proteins in milk 总被引:2,自引:0,他引:2
I Wilmut A L Archibald M McClenaghan J P Simons C B Whitelaw A J Clark 《Experientia》1991,47(9):905-912
There is every reason to expect that it will be possible within the next few years to begin to use farm animals to produce large quantities of some of the human proteins that are needed for the treatment of disease. Revolutionary new opportunities for the production of novel proteins in milk have been created by the development of methods for gene transfer. Exploitation of these opportunities depends upon selection and cloning of milk protein genes and identification of the sequences that govern tissue specific hormonally induced expression in the mammary gland. Studies with three genes, ovine beta-lactoglobulin, rat beta-casein and whey acidic protein of rat and mouse, suggest that they may all meet this requirement. Fragments of the ovine beta-lactoglobulin, murine whey acidic protein and rabbit beta-casein genes have directed production of novel proteins in the milk of transgenic mice, sheep, rabbits and pigs. The proteins were biologically active and usually co-migrated with authentic proteins. In early experiments, protein concentration was low, but our recent observations suggest that fusion genes containing genomic clones direct production of concentrations of protein that are suitable for commercial exploitation. In the longer term, two approaches may offer the potential of more reliable expression. Control elements capable of directing expression that is independent of site of insertion of the gene, but dependent on the number of copies of the gene, have been identified for a small number of genes. The availability of such elements for the milk protein genes would increase the reliability of gene expression considerably. Alternatively, targeted mutation of genes may allow the insertion of coding sequences within an existing gene so avoiding position effects. 相似文献
198.
199.
Kile BT Hentges KE Clark AT Nakamura H Salinger AP Liu B Box N Stockton DW Johnson RL Behringer RR Bradley A Justice MJ 《Nature》2003,425(6953):81-86
Now that the mouse and human genome sequences are complete, biologists need systematic approaches to determine the function of each gene. A powerful way to discover gene function is to determine the consequence of mutations in living organisms. Large-scale production of mouse mutations with the point mutagen N-ethyl-N-nitrosourea (ENU) is a key strategy for analysing the human genome because mouse mutants will reveal functions unique to mammals, and many may model human diseases. To examine genes conserved between human and mouse, we performed a recessive ENU mutagenesis screen that uses a balancer chromosome, inversion chromosome 11 (refs 4, 5). Initially identified in the fruitfly, balancer chromosomes are valuable genetic tools that allow the easy isolation of mutations on selected chromosomes. Here we show the isolation of 230 new recessive mouse mutations, 88 of which are on chromosome 11. This genetic strategy efficiently generates and maps mutations on a single chromosome, even as mutations throughout the genome are discovered. The mutations reveal new defects in haematopoiesis, craniofacial and cardiovascular development, and fertility. 相似文献
200.