全文获取类型
收费全文 | 517991篇 |
免费 | 4099篇 |
国内免费 | 1177篇 |
专业分类
化学 | 244750篇 |
晶体学 | 7817篇 |
力学 | 28149篇 |
综合类 | 14篇 |
数学 | 75323篇 |
物理学 | 167214篇 |
出版年
2021年 | 4201篇 |
2020年 | 4436篇 |
2019年 | 5138篇 |
2018年 | 12621篇 |
2017年 | 13179篇 |
2016年 | 12471篇 |
2015年 | 5866篇 |
2014年 | 9383篇 |
2013年 | 20796篇 |
2012年 | 18807篇 |
2011年 | 27303篇 |
2010年 | 19231篇 |
2009年 | 19517篇 |
2008年 | 24488篇 |
2007年 | 26750篇 |
2006年 | 16095篇 |
2005年 | 17892篇 |
2004年 | 15098篇 |
2003年 | 14023篇 |
2002年 | 12840篇 |
2001年 | 13914篇 |
2000年 | 10498篇 |
1999年 | 7994篇 |
1998年 | 6819篇 |
1997年 | 6575篇 |
1996年 | 6257篇 |
1995年 | 5490篇 |
1994年 | 5390篇 |
1993年 | 5273篇 |
1992年 | 5647篇 |
1991年 | 6068篇 |
1990年 | 5813篇 |
1989年 | 5788篇 |
1988年 | 5476篇 |
1987年 | 5654篇 |
1986年 | 5298篇 |
1985年 | 6689篇 |
1984年 | 6755篇 |
1983年 | 5703篇 |
1982年 | 5789篇 |
1981年 | 5494篇 |
1980年 | 5300篇 |
1979年 | 5783篇 |
1978年 | 5924篇 |
1977年 | 5889篇 |
1976年 | 5994篇 |
1975年 | 5606篇 |
1974年 | 5543篇 |
1973年 | 5734篇 |
1972年 | 4264篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
Dr. Felipe L. Coelho Eduarda S. Gil Dr. Paulo F. B. Gonçalves Dr. Leandra F. Campo Dr. Paulo H. Schneider 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(34):8157-8162
In this work, a series of 2-chalcogenylindoles was synthesized by an efficient methodology, starting from chalcogenoalkynes, including a previously unreported tellurium indole derivative. For the first time, these 2-substituted chalcogenylindoles were obtained in the absence of metal catalyst or base, under thermal conditions only. In addition, the results described herein represent a methodology with inverse regioselectivity for the chalcogen functionalization of indoles. 相似文献
104.
105.
Galia Pozina Elizaveta I. Girshova Konstantin M. Morozov Konstantin A. Ivanov Anton Yu. Egorov Mikhail A. Kaliteevski 《Annalen der Physik》2019,531(6)
Enhancement of spontaneous emission in a resonant Bragg quantum well (QW) structure with 60 periods of triple InAs monolayers embedded in a GaAs matrix is studied experimentally and theoretically. From measurements of the time‐resolved photoluminescence, besides the QW exciton at 1.47 eV, a specific super‐radiant (SR) emission demonstrating nonlinear properties is found. The SR mode shows a near‐quadratic dependence of intensity on excitation power, while its energy position follows the Bragg condition. It is revealed that the SR mode shows a peculiar non‐monotonic dependence of intensity on direction, with a maximum observed at approximately 40°. The enhancement in the SR emission at a specific direction is correlated well with suggested theoretical consideration of the modal Purcell factor for periodic quantum well structures. 相似文献
106.
107.
108.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films
were investigated using a number of techniques. A high saturation magnetic induction up to B
s
= 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed,
which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of
the composition.
The text was submitted by the authors in English. 相似文献
109.
N. I. Golovina G. N. Nechiporenko G. G. Nemtsev G. P. Dolganova V. P. Roshchupkin D. B. Lempert G. B. Manelis 《Russian Journal of Applied Chemistry》2007,80(1):24-30
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined. 相似文献
110.
Paul S. Wesson 《General Relativity and Gravitation》2003,35(1):111-119
Results from 5D induced-matter and membrane theory with null paths are extended to show that a particle obeys the 4D Klein-Gordon equation but with a variable mass. The Dirac equation also follows, but raises concerns about 4D quantization in the two natural 5D gauges, and reopens the question of a Regge-like trajectory for the spin angular momenta and squared masses of gravitationally-dominated systems. 相似文献