全文获取类型
收费全文 | 1006篇 |
免费 | 2篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 13篇 |
理论与方法论 | 5篇 |
现状及发展 | 259篇 |
研究方法 | 100篇 |
综合类 | 567篇 |
自然研究 | 66篇 |
出版年
2018年 | 4篇 |
2016年 | 4篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 31篇 |
2011年 | 98篇 |
2010年 | 6篇 |
2008年 | 39篇 |
2007年 | 37篇 |
2006年 | 36篇 |
2005年 | 37篇 |
2004年 | 34篇 |
2003年 | 31篇 |
2002年 | 34篇 |
2001年 | 20篇 |
2000年 | 44篇 |
1999年 | 16篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 18篇 |
1991年 | 10篇 |
1990年 | 19篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 14篇 |
1986年 | 19篇 |
1985年 | 12篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 16篇 |
1978年 | 19篇 |
1977年 | 20篇 |
1976年 | 15篇 |
1975年 | 20篇 |
1974年 | 23篇 |
1973年 | 17篇 |
1972年 | 20篇 |
1971年 | 31篇 |
1970年 | 44篇 |
1969年 | 15篇 |
1968年 | 27篇 |
1967年 | 26篇 |
1966年 | 22篇 |
1965年 | 10篇 |
1964年 | 8篇 |
1963年 | 2篇 |
1961年 | 2篇 |
排序方式: 共有1010条查询结果,搜索用时 15 毫秒
61.
D. A. S. Smith 《Cellular and molecular life sciences : CMLS》1978,34(7):845-846
Summary
Danaus chrysippus grows faster and attains significantly greater size when fed as a larva on several species of Asclepiadaceae (milkweeds) containing cardiac glycosides than on one which does not.Acknowledgment. I thank Professor D. Schneider and Dr M. Boppré for sending me a sample of butterflies of Kenya stock reared in the Federal Republic of Germany. 相似文献
62.
Summary Complexes of pyridine-2-carbothioamide with diethyltin dichloride, dibenzyltin dichloride and phenyltin trichloride are described. In each case, the chelating agent is bound to the tin(IV) atom by the pyridine nitrogen and the carbothioamide sulphur, giving support to proposals that certain organotin compounds cause enzyme deactivation via the formation of tin-sulphur bonds.Acknowledgment. We thank the Tin Industry (Research and Development) Board, Kuala Lumpur, for financial support. 相似文献
63.
64.
Carbohydrate movement between the symbionts of lichens 总被引:5,自引:0,他引:5
65.
66.
67.
Bird AW Yu DY Pray-Grant MG Qiu Q Harmon KE Megee PC Grant PA Smith MM Christman MF 《Nature》2002,419(6905):411-415
68.
Vetter DE Li C Zhao L Contarino A Liberman MC Smith GW Marchuk Y Koob GF Heinemann SF Vale W Lee KF 《Nature genetics》2002,31(4):363-369
Urocortin is a member of the corticotropin-releasing hormone peptide family and is found in many discrete brain regions. The distinct expression pattern of urocortin suggests that it influences such behaviors as feeding, anxiety and auditory processing. To better define the physiological roles of urocortin, we have generated mice carrying a null mutation of the urocortin gene. Urocortin-deficient mice have normal basal feeding behavior and stress responses, but show heightened anxiety-like behaviors in the elevated plus maze and open-field tests. In addition, hearing is impaired in the mutant mice at the level of the inner ear, suggesting that urocortin is involved in the normal development of cochlear sensory-cell function. These results provide the first example of a function for any peptidergic system in hearing. 相似文献
69.
Crumbs, the Drosophila homologue of human CRB1/RP12, is essential for photoreceptor morphogenesis 总被引:3,自引:0,他引:3
The apical transmembrane protein Crumbs is a central regulator of epithelial apical-basal polarity in Drosophila. Loss-of-function mutations in the human homologue of Crumbs, CRB1 (RP12), cause recessive retinal dystrophies, including retinitis pigmentosa. Here we show that Crumbs and CRB1 localize to corresponding subdomains of the photoreceptor apical plasma membrane: the stalk of the Drosophila photoreceptor and the inner segment of mammalian photoreceptors. These subdomains support the morphogenesis and orientation of the photosensitive membrane organelles: rhabdomeres and outer segments, respectively. Drosophila Crumbs is required to maintain zonula adherens integrity during the rapid apical membrane expansion that builds the rhabdomere. Crumbs also regulates stalk development by stabilizing the membrane-associated spectrin cytoskeleton, a function mechanistically distinct from its role in epithelial apical-basal polarity. We propose that Crumbs is a central component of a molecular scaffold that controls zonula adherens assembly and defines the stalk as an apical membrane subdomain. Defects in such scaffolds may contribute to human CRB1-related retinal dystrophies. 相似文献
70.
Chimaeric sounds reveal dichotomies in auditory perception 总被引:18,自引:0,他引:18
By Fourier's theorem, signals can be decomposed into a sum of sinusoids of different frequencies. This is especially relevant for hearing, because the inner ear performs a form of mechanical Fourier transform by mapping frequencies along the length of the cochlear partition. An alternative signal decomposition, originated by Hilbert, is to factor a signal into the product of a slowly varying envelope and a rapidly varying fine time structure. Neurons in the auditory brainstem sensitive to these features have been found in mammalian physiological studies. To investigate the relative perceptual importance of envelope and fine structure, we synthesized stimuli that we call 'auditory chimaeras', which have the envelope of one sound and the fine structure of another. Here we show that the envelope is most important for speech reception, and the fine structure is most important for pitch perception and sound localization. When the two features are in conflict, the sound of speech is heard at a location determined by the fine structure, but the words are identified according to the envelope. This finding reveals a possible acoustic basis for the hypothesized 'what' and 'where' pathways in the auditory cortex. 相似文献