全文获取类型
收费全文 | 225篇 |
免费 | 0篇 |
专业分类
系统科学 | 2篇 |
现状及发展 | 61篇 |
研究方法 | 27篇 |
综合类 | 134篇 |
自然研究 | 1篇 |
出版年
2018年 | 1篇 |
2016年 | 1篇 |
2013年 | 3篇 |
2012年 | 9篇 |
2011年 | 15篇 |
2010年 | 2篇 |
2009年 | 1篇 |
2008年 | 4篇 |
2007年 | 5篇 |
2006年 | 3篇 |
2005年 | 15篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1996年 | 1篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1972年 | 9篇 |
1971年 | 9篇 |
1970年 | 8篇 |
1969年 | 6篇 |
1968年 | 6篇 |
1967年 | 4篇 |
1966年 | 6篇 |
1965年 | 2篇 |
1959年 | 1篇 |
1958年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有225条查询结果,搜索用时 15 毫秒
31.
The lin-3 gene is necessary for induction of the Caenorhabditis elegans vulva by the anchor cell. It encodes a molecule similar to epidermal growth factor and to transforming growth factor-alpha and acts through the epidermal growth factor receptor homologue let-23. Expression of lin-3 in the anchor cell stimulates vulval induction; lin-3 may encode the vulval inducing signal. 相似文献
32.
Iodine-131 in human thyroids in Britain following Chernobyl 总被引:1,自引:0,他引:1
33.
Zusammenfassung Bestimmung der Auswirkung von artefiziellen Refraktionsanomalien auf die Aktivität von Neuren in primären Sehzentren.
This work was supported by U.S.P.H.S. Grant No. EY00576. 相似文献
This work was supported by U.S.P.H.S. Grant No. EY00576. 相似文献
34.
Summary A comparison of antagonism by bicuculline or strychnine of the effects of GABA or etomidate on rat isolated superior cervical ganglia, frog isolated hemisected spinal cords and rat central neurones in vivo indicates that etomidate has GABA-mimetic actions.Acknowledgments. This work was supported by the Medical Research Council and etomidate was provided by Janssen Pharmaceutica. 相似文献
35.
Summary A discrete middle band of tonic fibers in the claw closer muscles of lobsters functions as a sub-unit of the slow motor unit in maintaining dactyl posture at a low frequency of firing due to its synaptic properties and strategic location.Supported by National Institute of Health Grant to Dr A. G. Humes and the late Fred Lang.Supported by National Sciences and Engineering Research Council and Muscular Dystrophy Association of Canada. 相似文献
36.
Zusammenfassung Nachweis, dass rezeptive Kortexfelder der Kaninchen (70% der visuellen Zellen) auf Lichtstimuli bzw. Schärfe-Unschärfe-Änderung mit Amplitudenabfall reagieren.
This work was supported by U.S.P.H.S. Grant No. EY00576. 相似文献
This work was supported by U.S.P.H.S. Grant No. EY00576. 相似文献
37.
Clarke JT Gérard JC Grodent D Wannawichian S Gustin J Connerney J Crary F Dougherty M Kurth W Cowley SW Bunce EJ Hill T Kim J 《Nature》2005,433(7027):717-719
It has often been stated that Saturn's magnetosphere and aurorae are intermediate between those of Earth, where the dominant processes are solar wind driven, and those of Jupiter, where processes are driven by a large source of internal plasma. But this view is based on information about Saturn that is far inferior to what is now available. Here we report ultraviolet images of Saturn, which, when combined with simultaneous Cassini measurements of the solar wind and Saturn kilometric radio emission, demonstrate that its aurorae differ morphologically from those of both Earth and Jupiter. Saturn's auroral emissions vary slowly; some features appear in partial corotation whereas others are fixed to the solar wind direction; the auroral oval shifts quickly in latitude; and the aurora is often not centred on the magnetic pole nor closed on itself. In response to a large increase in solar wind dynamic pressure Saturn's aurora brightened dramatically, the brightest auroral emissions moved to higher latitudes, and the dawn side polar regions were filled with intense emissions. The brightening is reminiscent of terrestrial aurorae, but the other two variations are not. Rather than being intermediate between the Earth and Jupiter, Saturn's auroral emissions behave fundamentally differently from those at the other planets. 相似文献
38.
Ross AJ May-Simera H Eichers ER Kai M Hill J Jagger DJ Leitch CC Chapple JP Munro PM Fisher S Tan PL Phillips HM Leroux MR Henderson DJ Murdoch JN Copp AJ Eliot MM Lupski JR Kemp DT Dollfus H Tada M Katsanis N Forge A Beales PL 《Nature genetics》2005,37(10):1135-1140
The evolutionarily conserved planar cell polarity (PCP) pathway (or noncanonical Wnt pathway) drives several important cellular processes, including epithelial cell polarization, cell migration and mitotic spindle orientation. In vertebrates, PCP genes have a vital role in polarized convergent extension movements during gastrulation and neurulation. Here we show that mice with mutations in genes involved in Bardet-Biedl syndrome (BBS), a disorder associated with ciliary dysfunction, share phenotypes with PCP mutants including open eyelids, neural tube defects and disrupted cochlear stereociliary bundles. Furthermore, we identify genetic interactions between BBS genes and a PCP gene in both mouse (Ltap, also called Vangl2) and zebrafish (vangl2). In zebrafish, the augmented phenotype results from enhanced defective convergent extension movements. We also show that Vangl2 localizes to the basal body and axoneme of ciliated cells, a pattern reminiscent of that of the BBS proteins. These data suggest that cilia are intrinsically involved in PCP processes. 相似文献
39.
Gehrels N Sarazin CL O'Brien PT Zhang B Barbier L Barthelmy SD Blustin A Burrows DN Cannizzo J Cummings JR Goad M Holland ST Hurkett CP Kennea JA Levan A Markwardt CB Mason KO Meszaros P Page M Palmer DM Rol E Sakamoto T Willingale R Angelini L Beardmore A Boyd PT Breeveld A Campana S Chester MM Chincarini G Cominsky LR Cusumano G de Pasquale M Fenimore EE Giommi P Gronwall C Grupe D Hill JE Hinshaw D Hjorth J Hullinger D Hurley KC Klose S Kobayashi S Kouveliotou C Krimm HA Mangano V 《Nature》2005,437(7060):851-854
Gamma-ray bursts (GRBs) come in two classes: long (> 2 s), soft-spectrum bursts and short, hard events. Most progress has been made on understanding the long GRBs, which are typically observed at high redshift (z approximately 1) and found in subluminous star-forming host galaxies. They are likely to be produced in core-collapse explosions of massive stars. In contrast, no short GRB had been accurately (< 10') and rapidly (minutes) located. Here we report the detection of the X-ray afterglow from--and the localization of--the short burst GRB 050509B. Its position on the sky is near a luminous, non-star-forming elliptical galaxy at a redshift of 0.225, which is the location one would expect if the origin of this GRB is through the merger of neutron-star or black-hole binaries. The X-ray afterglow was weak and faded below the detection limit within a few hours; no optical afterglow was detected to stringent limits, explaining the past difficulty in localizing short GRBs. 相似文献
40.
B. E. Brooker A. J. Frost A. W. Hill 《Cellular and molecular life sciences : CMLS》1981,37(3):290-292
Summary Culture filtrate ofEscherichia coli produces changes in the bovine udder identical to those seen in experimental infections with the same organism.E. coli endotoxin produces an acute inflammatory response but none of the cell damage induced by culture filtrate. It appears therefore that at least 2 toxins are involved in the disease.Acknowledgments. We are grateful to Mrs K. Wells, Miss H. Meads and Miss A. Ashford for technical assistance. 相似文献