全文获取类型
收费全文 | 97篇 |
免费 | 1篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 5篇 |
教育与普及 | 1篇 |
现状及发展 | 28篇 |
研究方法 | 10篇 |
综合类 | 53篇 |
自然研究 | 3篇 |
出版年
2019年 | 3篇 |
2014年 | 1篇 |
2012年 | 5篇 |
2011年 | 9篇 |
2010年 | 3篇 |
2008年 | 2篇 |
2007年 | 5篇 |
2006年 | 4篇 |
2005年 | 10篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有100条查询结果,搜索用时 234 毫秒
51.
L. A. Mitscher A. B. Ray A. Chatterjee 《Cellular and molecular life sciences : CMLS》1971,27(1):16-17
Zusammenfassung RW-47 und Venoterpin sind identisch. Die absolute Konfiguration ist durch ORD-CD, Vergleiche mitl-(–)-actinidin ableitbar. 相似文献
52.
53.
54.
B Ray 《Experientia》1977,33(11):1439-1440
Human erythrocyte carbonic anhydrase B was purified and immobilized in polyacrylamide gel. As compared to the soluble enzyme, the immobilized enzyme was considerably more resistant to heat and sulphanilamide action. 相似文献
55.
56.
The emission of isoprene from the leaves of forest trees is a fundamental component of biosphere-atmosphere interactions, controlling many aspects of photochemistry in the lower atmosphere. As almost all commercial agriforest species emit high levels of isoprene, proliferation of agriforest plantations has significant potential to increase regional ozone pollution and enhance the lifetime of methane, an important determinant of global climate. Here we show that growth of an intact Populus deltoides plantation under increased CO2 (800 micromol x mol(-1) and 1,200 micromol x mol(-1)) reduced ecosystem isoprene production by 21% and 41%, while above-ground biomass accumulation was enhanced by 60% and 82%, respectively. Exposure to increased CO2 significantly reduced the cellular content of dimethylallyl diphosphate, the substrate for isoprene synthesis, in both leaves and leaf protoplasts. We identify intracellular metabolic competition for phosphoenolpyruvate as a possible control point in explaining the suppression of isoprene emission under increased CO2. Our results highlight the potential for uncoupling isoprene emission from biomass accumulation in an agriforest species, and show that negative air-quality effects of proliferating agriforests may be offset by increases in CO2. 相似文献
57.
58.
59.
Wendel HG De Stanchina E Fridman JS Malina A Ray S Kogan S Cordon-Cardo C Pelletier J Lowe SW 《Nature》2004,428(6980):332-337
Evading apoptosis is considered to be a hallmark of cancer, because mutations in apoptotic regulators invariably accompany tumorigenesis. Many chemotherapeutic agents induce apoptosis, and so disruption of apoptosis during tumour evolution can promote drug resistance. For example, Akt is an apoptotic regulator that is activated in many cancers and may promote drug resistance in vitro. Nevertheless, how Akt disables apoptosis and its contribution to clinical drug resistance are unclear. Using a murine lymphoma model, we show that Akt promotes tumorigenesis and drug resistance by disrupting apoptosis, and that disruption of Akt signalling using the mTOR inhibitor rapamycin reverses chemoresistance in lymphomas expressing Akt, but not in those with other apoptotic defects. eIF4E, a translational regulator that acts downstream of Akt and mTOR, recapitulates Akt's action in tumorigenesis and drug resistance, but is unable to confer sensitivity to rapamycin and chemotherapy. These results establish Akt signalling through mTOR and eIF4E as an important mechanism of oncogenesis and drug resistance in vivo, and reveal how targeting apoptotic programmes can restore drug sensitivity in a genotype-dependent manner. 相似文献
60.
Homozygous mutation of AURKC yields large-headed polyploid spermatozoa and causes male infertility 总被引:1,自引:0,他引:1
Dieterich K Soto Rifo R Faure AK Hennebicq S Ben Amar B Zahi M Perrin J Martinez D Sèle B Jouk PS Ohlmann T Rousseaux S Lunardi J Ray PF 《Nature genetics》2007,39(5):661-665
The World Health Organization conservatively estimates that 80 million people suffer from infertility worldwide. Male factors are believed to be responsible for 20-50% of all infertility cases, but microdeletions of the Y chromosome are the only genetic defects altering human spermatogenesis that have been reported repeatedly. We focused our work on infertile men with a normal somatic karyotype but typical spermatozoa mainly characterized by large heads, a variable number of tails and an increased chromosomal content (OMIM 243060). We performed a genome-wide microsatellite scan on ten infertile men presenting this characteristic phenotype. In all of these men, we identified a common region of homozygosity harboring the aurora kinase C gene (AURKC) with a single nucleotide deletion in the AURKC coding sequence. In addition, we show that this founder mutation results in premature termination of translation, yielding a truncated protein that lacks the kinase domain. We conclude that the absence of AURKC causes male infertility owing to the production of large-headed multiflagellar polyploid spermatozoa. 相似文献