全文获取类型
收费全文 | 286篇 |
免费 | 4篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 7篇 |
理论与方法论 | 4篇 |
现状及发展 | 99篇 |
研究方法 | 36篇 |
综合类 | 145篇 |
自然研究 | 1篇 |
出版年
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 11篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 16篇 |
2012年 | 23篇 |
2011年 | 31篇 |
2010年 | 6篇 |
2009年 | 2篇 |
2008年 | 12篇 |
2007年 | 30篇 |
2006年 | 24篇 |
2005年 | 16篇 |
2004年 | 17篇 |
2003年 | 15篇 |
2002年 | 11篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1992年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1967年 | 3篇 |
1966年 | 2篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1957年 | 4篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1947年 | 1篇 |
1946年 | 2篇 |
排序方式: 共有292条查询结果,搜索用时 15 毫秒
41.
42.
The post-perovskite phase of (Mg,Fe)SiO3 is believed to be the main mineral phase of the Earth's lowermost mantle (the D' layer). Its properties explain numerous geophysical observations associated with this layer-for example, the D' discontinuity, its topography and seismic anisotropy within the layer. Here we use a novel simulation technique, first-principles metadynamics, to identify a family of low-energy polytypic stacking-fault structures intermediate between the perovskite and post-perovskite phases. Metadynamics trajectories identify plane sliding involving the formation of stacking faults as the most favourable pathway for the phase transition, and as a likely mechanism for plastic deformation of perovskite and post-perovskite. In particular, the predicted slip planes are {010} for perovskite (consistent with experiment) and {110} for post-perovskite (in contrast to the previously expected {010} slip planes). Dominant slip planes define the lattice preferred orientation and elastic anisotropy of the texture. The {110} slip planes in post-perovskite require a much smaller degree of lattice preferred orientation to explain geophysical observations of shear-wave anisotropy in the D' layer. 相似文献
43.
44.
E. E. Müller A. Panerai Daniela Cocchi L. A. Frohman P. Mantegazza 《Cellular and molecular life sciences : CMLS》1973,29(7):874-876
Riassunto Il 2-desossi-d-glucosio somministrato nel ventricolo laterale del cervello del ratto provoca iperglicemia, inibizione della secrezione di insulina, iperfagia ed ipotermia a dosi che sono inefficaci per via sistemica.
MissesF. Ferrari, S. Bianchi andL. Scapellato provided skilful technical assistance. This investigation was supported by Grant No. 70.01788.04115.2380 of the Consiglio Nazionale delle Richerche, Italy. 相似文献
MissesF. Ferrari, S. Bianchi andL. Scapellato provided skilful technical assistance. This investigation was supported by Grant No. 70.01788.04115.2380 of the Consiglio Nazionale delle Richerche, Italy. 相似文献
45.
F. Arcamone L. Bernardi B. Patelli P. Giardino A. Di Marco A. M. Casazza C. Soranzo G. Pratesi 《Cellular and molecular life sciences : CMLS》1978,34(10):1255-1257
Summary A new synthetic procedure for the preparation of daunorubicin and adriamycin analogues bearing different substituents on ring D, has been developed. The new compounds display outstanding efficacy against experimental tumours of mice. 相似文献
46.
D. Cavallini C. de Marco B. Mondovì G. F. Azzone 《Cellular and molecular life sciences : CMLS》1955,11(2):61-62
Riassunto L'aminoetilcisteina, composto intermedio ipotetico di transulfurazione tra cisteina e etanolamina, è stata preparata cristallina sotto forma di monocloridrato, trattando la cisteina con bromoetilamina in ambiente alcalino. 相似文献
47.
Riassunto È stata messa in evidenza nel liquido amniotico di donne a termine di gravidanza la presenza di alcuni enzimi glicolitici. Sono riportati i dati quantitativi ottenuti per l'attività della fosforiboso-isomerasi, aldolasi, fosfoesoso-isomerasi e lattico-deidrogenasi. È stato determinato inoltre il contenuto proteico dei campioni di liquido amniotico presi in esame. 相似文献
48.
49.
The Amazon basin in transition 总被引:7,自引:0,他引:7
Davidson EA de Araújo AC Artaxo P Balch JK Brown IF C Bustamante MM Coe MT DeFries RS Keller M Longo M Munger JW Schroeder W Soares-Filho BS Souza CM Wofsy SC 《Nature》2012,481(7381):321-328
Agricultural expansion and climate variability have become important agents of disturbance in the Amazon basin. Recent studies have demonstrated considerable resilience of Amazonian forests to moderate annual drought, but they also show that interactions between deforestation, fire and drought potentially lead to losses of carbon storage and changes in regional precipitation patterns and river discharge. Although the basin-wide impacts of land use and drought may not yet surpass the magnitude of natural variability of hydrologic and biogeochemical cycles, there are some signs of a transition to a disturbance-dominated regime. These signs include changing energy and water cycles in the southern and eastern portions of the Amazon basin. 相似文献
50.