全文获取类型
收费全文 | 1554篇 |
免费 | 10篇 |
国内免费 | 42篇 |
专业分类
系统科学 | 26篇 |
丛书文集 | 2篇 |
教育与普及 | 4篇 |
理论与方法论 | 16篇 |
现状及发展 | 263篇 |
研究方法 | 252篇 |
综合类 | 986篇 |
自然研究 | 57篇 |
出版年
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 18篇 |
2017年 | 22篇 |
2016年 | 14篇 |
2015年 | 20篇 |
2014年 | 26篇 |
2013年 | 27篇 |
2012年 | 119篇 |
2011年 | 197篇 |
2010年 | 56篇 |
2009年 | 31篇 |
2008年 | 104篇 |
2007年 | 130篇 |
2006年 | 94篇 |
2005年 | 115篇 |
2004年 | 87篇 |
2003年 | 99篇 |
2002年 | 92篇 |
2001年 | 42篇 |
2000年 | 44篇 |
1999年 | 20篇 |
1997年 | 5篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1975年 | 9篇 |
1974年 | 5篇 |
1973年 | 9篇 |
1971年 | 9篇 |
1970年 | 9篇 |
1969年 | 7篇 |
1968年 | 5篇 |
1967年 | 7篇 |
1966年 | 5篇 |
1965年 | 7篇 |
排序方式: 共有1606条查询结果,搜索用时 805 毫秒
201.
W. M. Ellis D. M. Calder B. T. O. Lee 《Cellular and molecular life sciences : CMLS》1970,26(10):1156-1156
Résumé On décrit une population diploide dePoa annua L. d'Australie. Elle se montre différente des «mphihaploides» qui ont été trouvées en Californie. La signification de cette population en rapport avec l'origine supposée deP. annua est considerée.
Acknowledgement. This work was supported by a grant from the Nuffield Foundation. 相似文献
Acknowledgement. This work was supported by a grant from the Nuffield Foundation. 相似文献
202.
203.
Lee L. Bernardis M. Bahorsky Luise Bohacek 《Cellular and molecular life sciences : CMLS》1966,22(10):671-673
Zusammenfassung Im Gegensatz zu weiblichen Ratten zeigen männliche Tiere mit Läsionen des N. ventromedialis hypothalami im Alter von 26, 59, 75 und 140 Tagen kurz nach der Ablaktation keinen unmittelbaren Einfluss auf die Futteraufnahme, Erwachsene nie die in den gleichaltrigen weiblichen Ratten beobachtete Hyperphagie. Männliche Ratten erreichen das Kontrollniveau schon nach 5 Wochen, während die weiblichen Tiere noch ausgeprägte Hyperphagic zeigen.
This investigation was supported by U.S.P.H.S. Grant No. HE 06975 of the National Heart Institute. 相似文献
This investigation was supported by U.S.P.H.S. Grant No. HE 06975 of the National Heart Institute. 相似文献
204.
L-Asparaginase activity in human and animal sera 总被引:1,自引:0,他引:1
205.
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
206.
Chee JL Guan XL Lee JY Dong B Leong SM Ong EH Liou AK Lim TM 《Cellular and molecular life sciences : CMLS》2005,62(2):227-238
Many have hypothesized that cell death in Parkinsons disease is via apoptosis and, specifically, by the mitochondrial-mediated apoptotic pathway. We tested this hypothesis using a mouse dopaminergic cell line of mesencephalic origin, MN9D, challenged with the Parkinsonism-causing neurotoxin MPP+ (1-methyl-4-phenylpyridinium ion). Apoptosis was the main mode of cell death when the cells were subjected to MPP+ treatment under serum-free conditions for 24 h. Caspase-3 and caspase-9, however, were not activated, thus indicating the existence of alternate or compensatory cell death pathway(s) in dopaminergic neuronal cells. Using caspase inhibitors, we demonstrated that these pathways involve caspase-2, –8, –6 and –7. A time-course study indicated that activation of caspase-2 and –8 occurred upstream of caspase-6 and caspase-7. Upon MPP+ challenge, the apoptosis-inducing factor was translocated from the mitochondria into the MN9D cytosol and nucleus. These results suggest the existence of alternative apoptotic pathways in dopaminergic neurons.Received 20 September 2004; received after revision 5 November 2004; accepted 22 November 2004 相似文献
207.
Jeon YH Heo YS Kim CM Hyun YL Lee TG Ro S Cho JM 《Cellular and molecular life sciences : CMLS》2005,62(11):1198-1220
Phosphodiesterases (PDEs) are essential regulators of cyclic nucleotide signaling with diverse physiological functions. Because of their great market potential and therapeutic importance, PDE inhibitors became recognized as important therapeutic agents in the treatment of various diseases. Currently, there are seven PDE inhibitors on the market, and the pharmacological and safety evaluations of many drug candidates are in progress. Three-dimensional (3D) structures of catalytic domains of PDE 1, -3, -4, -5 and -9 in the presence of their inhibitors are now available, and can be utilized for rational drug design. Recent advances in molecular pharmacology of PDE isoenzymes resulted in identification of new potential applications of PDE inhibitors in various therapeutic areas, including dementia, depression and schizophrenia. This review will describe the latest advances in PDE research on 3D structural studies, the potential of therapeutic applications and the development of drug candidates.Received 30 November 2004; received after revision 24 January 2005; accepted 5 February 2005 相似文献
208.
Proteins with polyglutamine (polyQ) expansions accumulate in the nucleus and affect gene expression. The mechanism by which mutant huntingtin (htt) accumulates intranuclearly is not known; wild-type htt, a 350-kDa protein of unknown function, is normally found in the cytoplasm. N-terminal fragments of mutant htt, which contain a polyQ expansion (>37 glutamines), have no conserved nuclear localization sequences or nuclear export sequences but can accumulate in the nucleus and cause neurological problems in transgenic mice. Here we report that N-terminal htt shuttles between the cytoplasm and nucleus in a Ran GTPase-independent manner. Small N-terminal htt fragments interact with the nuclear pore protein translocated promoter region (Tpr), which is involved in nuclear export. PolyQ expansion and aggregation decrease this interaction and increase the nuclear accumulation of htt. Reducing the expression of Tpr by RNA interference or deletion of ten amino acids of N-terminal htt, which are essential for the interaction of htt with Tpr, increased the nuclear accumulation of htt. These results suggest that Tpr has a role in the nuclear export of N-terminal htt and that polyQ expansion reduces this nuclear export to cause the nuclear accumulation of htt. 相似文献
209.
Mehrabian M Allayee H Stockton J Lum PY Drake TA Castellani LW Suh M Armour C Edwards S Lamb J Lusis AJ Schadt EE 《Nature genetics》2005,37(11):1224-1233
210.
Ménétrey J Bahloul A Wells AL Yengo CM Morris CA Sweeney HL Houdusse A 《Nature》2005,435(7043):779-785
Here we solve a 2.4-A structure of a truncated version of the reverse-direction myosin motor, myosin VI, that contains the motor domain and binding sites for two calmodulin molecules. The structure reveals only minor differences in the motor domain from that in plus-end directed myosins, with the exception of two unique inserts. The first is near the nucleotide-binding pocket and alters the rates of nucleotide association and dissociation. The second unique insert forms an integral part of the myosin VI converter domain along with a calmodulin bound to a novel target motif within the insert. This serves to redirect the effective 'lever arm' of myosin VI, which includes a second calmodulin bound to an 'IQ motif', towards the pointed (minus) end of the actin filament. This repositioning largely accounts for the reverse directionality of this class of myosin motors. We propose a model incorporating a kinesin-like uncoupling/docking mechanism to provide a full explanation of the movements of myosin VI. 相似文献