首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   812篇
  免费   12篇
  国内免费   9篇
化学   368篇
晶体学   4篇
力学   19篇
数学   279篇
物理学   163篇
  2021年   9篇
  2020年   11篇
  2019年   9篇
  2018年   16篇
  2017年   10篇
  2016年   15篇
  2015年   15篇
  2014年   23篇
  2013年   47篇
  2012年   30篇
  2011年   37篇
  2010年   30篇
  2009年   27篇
  2008年   30篇
  2007年   35篇
  2006年   36篇
  2005年   23篇
  2004年   19篇
  2003年   20篇
  2002年   20篇
  2001年   13篇
  2000年   9篇
  1999年   10篇
  1996年   7篇
  1994年   9篇
  1993年   6篇
  1989年   8篇
  1988年   7篇
  1987年   6篇
  1986年   6篇
  1985年   9篇
  1984年   5篇
  1983年   7篇
  1982年   7篇
  1981年   5篇
  1980年   5篇
  1979年   9篇
  1978年   7篇
  1977年   6篇
  1976年   9篇
  1974年   5篇
  1973年   6篇
  1959年   5篇
  1932年   12篇
  1931年   6篇
  1930年   5篇
  1928年   9篇
  1927年   6篇
  1926年   5篇
  1893年   13篇
排序方式: 共有833条查询结果,搜索用时 0 毫秒
91.
The magnetic properties of two amorphous Fe?Ni?Zr alloys, Fe89.7Ni0.03Zr10 and Fe70Ni20Zr10, both in the “as cast” and neutron irradiated states were investigated by Mössbauer spectroscopy and dc magnetic susceptibility measurements. The upper magnetic ordering temperatures of Fe89.7Ni0.03Zr10 are 232K and 246K for the “as cast” and irradiated samples, respectively. The magnetic ordering temperature for Fe70Ni20Zr10 was about 478K for both the “as cast” and irradiated samples. Both compositions yield magnetic hyperfine spectra, which show a considerable relaxation effect that must be explicitly considered in the calculation of the average local Fe moments. When this is done, these values derived from Mössbauer spectra are in good agreement with the dc susceptibility values. The effects of neutron irradiation on the magnetic properties of these alloys are small.  相似文献   
92.
The densities of the pure organic liquids: cyclohexane, nitrobenzene, 1-hexanol, 1-octanol, 1-decanol, and 1-dodecanol have been measured with an accuracy of 10–5 g/cm3 using the mechanical oscillator technique. The results were compared to the values given in the literature. From the measured densities the coefficients of thermal expansion were calculated.

Mit 1 Abbildung  相似文献   
93.
94.
Tertiary amine oxides catalyze a variety of phase transfer reactions, primarily by insitu deoxygenation to form the tertiary amine or derived catalyst.  相似文献   
95.
In this article we give a complete global classification of the class QSess of planar, essentially quadratic differential systems (i.e. defined by relatively prime polynomials and whose points at infinity are not all singular), according to their topological behavior in the vicinity of infinity. This class depends on 12 parameters but due to the action of the affine group and re-scaling of time, the family actually depends on five parameters. Our classification theorem (Theorem 7.1) gives us a complete dictionary connecting very simple integer-valued invariants which encode the geometry of the systems in the vicinity of infinity, with algebraic invariants and comitants which are a powerful tool for computer algebra computations helpful in the route to obtain the full topological classification of the class QS of all quadratic differential systems.  相似文献   
96.
97.
The frequency of radiation from Ta(superconducting)-Al(normal) point contacts has been measured as a function of temperature. The dependence agrees with the Bardeen-Cooper-Schrieffer (BCS) gap equation for Ta.  相似文献   
98.
We study the parity-violating neutral current effects in muonic atoms which might result from an interference between E1 and E2 amplitudes in 3D → 1S transitions. We conclude that polarization asymmetries may be measurable in heavy atoms (Z ~ 70) exhibiting large nuclear deformations.  相似文献   
99.
Characteristics of p-terphenyl and PBD, the most efficient uv dyes, have been investigated under high intensity pumping by a multi-atmosphere KrF1 discharge laser at 248 nm wavelength. Energy conversion efficiencies, spectral features and temporal behaviour of the dyes were studied parametrically. A maximum powerof 2 MW uv emission with a bandwidth of ~2×10-2 nm was obtained for PBD. It was found that a mixture of both dyes provided higher (by a factor of 1.3) output in the range 348–366 nm than either of the dyes alone. Significant pump intensity dependent conversion efficiency and pulse shape variations were observed for the most efficient uv dye, p-terphenyl and were related to triplet-triplet adsorption processes in the dye.  相似文献   
100.
An important 13C NMR shielding effect on carbons bearing a heavy chalcogen is demonstrated. This effect is parallel to that induced by iodine, but to a lesser extent. For acyclic compounds and for partially saturated heterocycles, there is an excellent linear correlation between the 13C chemical shifts of carbons bearing a chalcogen and carbons bearing a halogen atom in the corresponding compound. The linearity of the relationship is less satisfactory with heteroaromatic compounds.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号