全文获取类型
收费全文 | 252122篇 |
免费 | 1585篇 |
国内免费 | 405篇 |
专业分类
化学 | 115578篇 |
晶体学 | 3469篇 |
力学 | 13582篇 |
综合类 | 7篇 |
数学 | 39716篇 |
物理学 | 81760篇 |
出版年
2019年 | 1173篇 |
2018年 | 10432篇 |
2017年 | 11288篇 |
2016年 | 6591篇 |
2015年 | 2422篇 |
2014年 | 2540篇 |
2013年 | 6439篇 |
2012年 | 9317篇 |
2011年 | 18802篇 |
2010年 | 11515篇 |
2009年 | 11636篇 |
2008年 | 16450篇 |
2007年 | 20082篇 |
2006年 | 5604篇 |
2005年 | 11977篇 |
2004年 | 7911篇 |
2003年 | 7315篇 |
2002年 | 5318篇 |
2001年 | 4488篇 |
2000年 | 3629篇 |
1999年 | 2613篇 |
1998年 | 2285篇 |
1997年 | 2203篇 |
1996年 | 2156篇 |
1995年 | 2001篇 |
1994年 | 1974篇 |
1993年 | 1804篇 |
1992年 | 2065篇 |
1991年 | 2197篇 |
1990年 | 1994篇 |
1989年 | 2003篇 |
1988年 | 1949篇 |
1987年 | 1848篇 |
1986年 | 1773篇 |
1985年 | 2284篇 |
1984年 | 2430篇 |
1983年 | 1993篇 |
1982年 | 2167篇 |
1981年 | 2056篇 |
1980年 | 1979篇 |
1979年 | 2136篇 |
1978年 | 2314篇 |
1977年 | 2098篇 |
1976年 | 2182篇 |
1975年 | 2072篇 |
1974年 | 2120篇 |
1973年 | 2155篇 |
1972年 | 1392篇 |
1971年 | 1235篇 |
1968年 | 1177篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
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
83.
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
84.
In this work the results of the statistical topometric analysis of fracture surfaces of soda-lime-silica glass with and without ionic exchange treatment are reported. In this case, the mechanism of substitution is K+-Na+. atomic force microscopy (AFM) was employed to record the topometric data from the fracture surface. The roughness exponent (ζ) and the correlation length (ξ) were calculated by the variable bandwidth method. The analysis for both glasses (subjected and non-subjected to ionic exchange) for ζ shows a value ∼0.8, this value agrees well with that reported in the literature for rapid crack propagation in a variety of materials. The correlation length shows different values for each condition. These results, along with those of microhardness indentations suggest that the self-affine correlation length is influenced by the complex interactions of the stress field of microcracks with that resulting from the collective behavior of the point defects introduced by the strengthening mechanism of ionic exchange. 相似文献
85.
Yu. V. Pokonova 《Russian Journal of Applied Chemistry》2007,80(12):2163-2164
Kinetic, sorption and selectivity properties of commercial adsorbents are improved by adding petroleum residues (tar asphaltene concentrates) 13% of whole mass. Obtained adsorbents can be used for selective extraction of nobel metals from multicomponent polymetallic solutions of heavy metals and fro sewages purification for removing arsenic. 相似文献
86.
The European Physical Journal E - The isothermal gas adsorption of two hexane isomers (n-hexane and cyclohexane) in the mesopores of MCM-41 silica have been investigated by small angle neutron... 相似文献
87.
G. Panina 《Central European Journal of Mathematics》2003,1(2):157-168
All 3-dimensional convex polytopes are known to be rigid. Still their Minkowski differences (virtual polytopes) can be flexible
with any finite freedom degree. We derive some sufficient rigidity conditions for virtual polytopes and present some examples
of flexible ones. For example, Bricard's first and second flexible octahedra can be supplied by the structure of a virtual
polytope. 相似文献
88.
89.
Planar laser-induced fluorescence visualisation is used to investigate nonuniformities in the flow of a hypersonic conical nozzle. Possible causes for the nonuniformity are outlined and investigated, and the problem is shown to be due to a small step at the nozzle throat. Entrainment of cold boundary layer gas is postulated as the cause of the signal nonuniformity.
PACS 47.80.Jk, 47.40.Ki, 47.60.+i 相似文献
90.
Investigated is the dependency of the crack tip opening displacement (CTOD) on the local microstructure of the heat affected zone in high-strength low-alloy (HSLA) microalloyed steel. Since the initiation of the crack tip location could not be controlled in fatigue, any possible correlation between heat iput in welding and fracture toughness could be smeared. Modified CTOD data are defined; they show that the fracture resistance of the weld joint decreased as the heat input increased. 相似文献