全文获取类型
收费全文 | 473667篇 |
免费 | 3831篇 |
国内免费 | 1182篇 |
专业分类
化学 | 226254篇 |
晶体学 | 7185篇 |
力学 | 25287篇 |
综合类 | 7篇 |
数学 | 67639篇 |
物理学 | 152308篇 |
出版年
2021年 | 3532篇 |
2020年 | 3718篇 |
2019年 | 4308篇 |
2018年 | 12189篇 |
2017年 | 12766篇 |
2016年 | 10968篇 |
2015年 | 5064篇 |
2014年 | 7781篇 |
2013年 | 17328篇 |
2012年 | 16942篇 |
2011年 | 25926篇 |
2010年 | 17570篇 |
2009年 | 17692篇 |
2008年 | 23216篇 |
2007年 | 25709篇 |
2006年 | 14183篇 |
2005年 | 17115篇 |
2004年 | 14010篇 |
2003年 | 13065篇 |
2002年 | 11632篇 |
2001年 | 11620篇 |
2000年 | 9090篇 |
1999年 | 6847篇 |
1998年 | 5923篇 |
1997年 | 5657篇 |
1996年 | 5550篇 |
1995年 | 4939篇 |
1994年 | 4905篇 |
1993年 | 4979篇 |
1992年 | 5067篇 |
1991年 | 5466篇 |
1990年 | 5152篇 |
1989年 | 5167篇 |
1988年 | 5032篇 |
1987年 | 4963篇 |
1986年 | 4646篇 |
1985年 | 6159篇 |
1984年 | 6331篇 |
1983年 | 5180篇 |
1982年 | 5523篇 |
1981年 | 5337篇 |
1980年 | 5042篇 |
1979年 | 5413篇 |
1978年 | 5674篇 |
1977年 | 5566篇 |
1976年 | 5753篇 |
1975年 | 5300篇 |
1974年 | 5247篇 |
1973年 | 5462篇 |
1972年 | 4072篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
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
192.
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
193.
194.
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
195.
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
196.
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
197.
198.
199.
An attempt is made to find out the suitable entrainment and exit boundary conditions in laminar flow situations. Streamfunction vorticity formulation of the Navier–Stokes equations are solved by ADI method. Two‐dimensional laminar plane wall jet flow is used to test different forms of the boundary conditions. Results are compared with the experimental and similarity solution and the proper boundary condition is suggested. The Kind 1 boundary condition is recommended. It consists of zero first derivative condition for velocity variable and for streamfunction equation, mixed derivative at the entrainment and exit boundaries. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
200.
The paper discusses the applicability of quasi-crystalline approximation to describing the thermal motion of water molecules in their normal and supercooled states. The problem is subjected to the critical analysis of experimental data on incoherent scattering of slow neutrons based on theories developed by Singwi-Sjolander [1] and Oskotsky [2] modified to duly take into account the limited applicability range of diffusion approximation. The applicability conditions of quasi-crystalline approximation are shown to be consistently satisfied only when water is in supercooled state and within a narrow temperature range above the melting temperature. 相似文献