全文获取类型
收费全文 | 133015篇 |
免费 | 1764篇 |
国内免费 | 519篇 |
专业分类
化学 | 73879篇 |
晶体学 | 2109篇 |
力学 | 5215篇 |
综合类 | 6篇 |
数学 | 13402篇 |
物理学 | 40687篇 |
出版年
2016年 | 1447篇 |
2015年 | 1127篇 |
2014年 | 1510篇 |
2013年 | 5179篇 |
2012年 | 3796篇 |
2011年 | 4896篇 |
2010年 | 2994篇 |
2009年 | 2736篇 |
2008年 | 4355篇 |
2007年 | 4405篇 |
2006年 | 4462篇 |
2005年 | 4378篇 |
2004年 | 3856篇 |
2003年 | 3422篇 |
2002年 | 3346篇 |
2001年 | 3659篇 |
2000年 | 2754篇 |
1999年 | 2266篇 |
1998年 | 1958篇 |
1997年 | 1965篇 |
1996年 | 1948篇 |
1995年 | 1855篇 |
1994年 | 1617篇 |
1993年 | 1630篇 |
1992年 | 1820篇 |
1991年 | 1828篇 |
1990年 | 1753篇 |
1989年 | 1743篇 |
1988年 | 1754篇 |
1987年 | 1729篇 |
1986年 | 1642篇 |
1985年 | 2249篇 |
1984年 | 2394篇 |
1983年 | 1980篇 |
1982年 | 2317篇 |
1981年 | 2135篇 |
1980年 | 2160篇 |
1979年 | 2140篇 |
1978年 | 2292篇 |
1977年 | 2193篇 |
1976年 | 2195篇 |
1975年 | 2119篇 |
1974年 | 1963篇 |
1973年 | 2160篇 |
1972年 | 1312篇 |
1971年 | 1011篇 |
1970年 | 948篇 |
1969年 | 954篇 |
1968年 | 1075篇 |
1967年 | 1124篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Yang T. L. Kao C. L. Kuo C. E. Yeh H. C. Li W. J. Li H. T. Chen C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the... 相似文献
2.
3.
Theoretical and Mathematical Physics - Dynamic systems acting on the plane and possessing the Wada property have been observed. There exist only two topological types, symmetric and antisymmetric,... 相似文献
4.
5.
Li Y. Shi W. H. Dong L. M. Xu S. X. Huang H. J. Yin J. R. 《Journal of Applied Spectroscopy》2022,89(3):534-541
Journal of Applied Spectroscopy - Sr3B2O6:Dy3+, Eu3+ single-matrix white-light-emitting materials are prepared using the high-temperature solid-state method. The microstructure, emission spectrum,... 相似文献
6.
Ajit Kumar Singh Seulgi Ji Baghendra Singh Chittaranjan Das Heechae Choi Prashanth W. Menezes Arindam Indra 《Materials Today Chemistry》2022
Herein, we report a Mott-Schottky catalyst by entrapping cobalt nanoparticles inside the N-doped graphene shell (Co@NC). The Co@NC delivered excellent oxygen evolution activity with an overpotential of merely 248 mV at a current density of 10 mA cm–2 with promising long-term stability. The importance of Co encapsulated in NC has further been demonstrated by synthesizing Co nanoparticles without NC shell. The synergy between the hexagonal close-packed (hcp) and face-centered cubic (fcc) Co plays a major role to improve the OER activity, whereas the NC shell optimizes the electronic structure, improves the electron conductivity, and offers a large number of active sites in Co@NC. The density functional theory calculations have revealed that the hcp Co has a dominant role in the surface reaction of electrocatalytic oxygen evolution, whereas the fcc phase induces the built-in electric field at the interfaces with N-doped graphene to accelerate the H+ ion transport. 相似文献
7.
Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.
相似文献8.
Pengjin Qin Li-An Wang Prof. Joseph M. O'Connor Prof. Kim K. Baldridge Yifan Li Burak Tufekci Jiyue Chen Prof. Arnold L. Rheingold 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(41):18114-18121
Triene 6π electrocyclization, wherein a conjugated triene undergoes a concerted stereospecific cycloisomerization to a cyclohexadiene, is a reaction of great historical and practical significance. In order to circumvent limitations imposed by the normally harsh reaction conditions, chemists have long sought to develop catalytic variants based upon the activating power of metal–alkene coordination. Herein, we demonstrate the first successful implementation of such a strategy by utilizing [(C5H5)Ru(NCMe)3]PF6 as a precatalyst for the disrotatory 6π electrocyclization of highly substituted trienes that are resistant to thermal cyclization. Mechanistic and computational studies implicate hexahapto transition-metal coordination as responsible for lowering the energetic barrier to ring closure. This work establishes a foundation for the development of new catalysts for stereoselective electrocyclizations. 相似文献
9.
10.
Su X. F. Zhang Y. L. Maximov A. L. Zhang K. Xin Q. Feng C. Q. Bai X. F. Wu W. 《Russian Journal of Applied Chemistry》2020,93(1):127-136
Russian Journal of Applied Chemistry - Nanoscale ZSM-5 (AlZ5-D) and Ga-substituted ZSM-5 zeolites ((Al,Ga)Z5-D and GaZ5-D) were synthesized by a green dry-gel conversion strategy. For comparison,... 相似文献