全文获取类型
收费全文 | 2910篇 |
免费 | 108篇 |
国内免费 | 14篇 |
专业分类
化学 | 1979篇 |
晶体学 | 22篇 |
力学 | 43篇 |
数学 | 450篇 |
物理学 | 538篇 |
出版年
2021年 | 26篇 |
2020年 | 58篇 |
2019年 | 40篇 |
2018年 | 32篇 |
2017年 | 27篇 |
2016年 | 85篇 |
2015年 | 65篇 |
2014年 | 69篇 |
2013年 | 117篇 |
2012年 | 120篇 |
2011年 | 113篇 |
2010年 | 106篇 |
2009年 | 98篇 |
2008年 | 121篇 |
2007年 | 112篇 |
2006年 | 133篇 |
2005年 | 117篇 |
2004年 | 104篇 |
2003年 | 87篇 |
2002年 | 108篇 |
2001年 | 55篇 |
2000年 | 61篇 |
1999年 | 64篇 |
1998年 | 50篇 |
1997年 | 60篇 |
1996年 | 68篇 |
1995年 | 55篇 |
1994年 | 59篇 |
1993年 | 46篇 |
1992年 | 45篇 |
1991年 | 41篇 |
1990年 | 35篇 |
1989年 | 53篇 |
1988年 | 29篇 |
1987年 | 19篇 |
1986年 | 29篇 |
1985年 | 32篇 |
1984年 | 33篇 |
1983年 | 38篇 |
1982年 | 22篇 |
1981年 | 25篇 |
1980年 | 32篇 |
1979年 | 37篇 |
1978年 | 36篇 |
1977年 | 25篇 |
1976年 | 23篇 |
1975年 | 21篇 |
1974年 | 20篇 |
1973年 | 24篇 |
1971年 | 23篇 |
排序方式: 共有3032条查询结果,搜索用时 46 毫秒
111.
112.
The European Physical Journal H - This is a tutorial for the many-worlds theory by Everett, which includes some of my personal views. It has two main parts. The first main part shows the emergence... 相似文献
113.
114.
Róbert Bordás Volker John Ellen Schmeyer Dominique Thévenin 《Theoretical and Computational Fluid Dynamics》2013,27(3-4):253-271
The droplet size distribution in a turbulent flow field is considered and modeled by means of a population balance system. This paper studies different numerical methods for the 4D population balance equation and their impact on an output of interest, the time-space-averaged droplet size distribution at the outlet, which is known from experiments. These methods include different interpolations of the experimental data at the inlet, various discretizations in time and space, and different schemes for computing the coalescence integrals. It will be shown that noticeable changes in the output of interest might occur. In addition, the computational efficiency of the studied methods is discussed. 相似文献
115.
116.
117.
An algebraic variational multiscale–multigrid method is proposed for large-eddy simulation of turbulent variable-density flow at low Mach number. Scale-separating operators generated by level-transfer operators from plain aggregation algebraic multigrid methods enable the application of modeling terms to selected scale groups (here, the smaller of the resolved scales) in a purely algebraic way. Thus, for scale separation, no additional discretization besides the basic one is required, in contrast to earlier approaches based on geometric multigrid methods. The proposed method is thoroughly validated via three numerical test cases of increasing complexity: a Rayleigh–Taylor instability, turbulent channel flow with a heated and a cooled wall, and turbulent flow past a backward-facing step with heating. Results obtained with the algebraic variational multiscale–multigrid method are compared to results obtained with residual-based variational multiscale methods as well as reference results from direct numerical simulation, experiments and LES published elsewhere. Particularly, mean and various second-order velocity and temperature results obtained for turbulent channel flow with a heated and a cooled wall indicate the higher prediction quality achievable when adding a small-scale subgrid-viscosity term within the algebraic multigrid framework instead of residual-based terms accounting for the subgrid-scale part of the non-linear convective term. 相似文献
118.
Michael Veith Charu Mathur Volker Hugh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):489-492
The synthesis of the new heteroleptic heterotrimetallic cluster, [(C5H5)Sn(μ-OBut)2Ge(OBut)Mo(CO)5] (1) has been achieved by a thermally induced CO substitution of the transition metal derivative, Mo(CO)6, by the basic germanium atom of the cyclopentadienyl heterobimetallic alkoxide, [(C5H5)Sn(μ-OBut)2Ge(OBut)]. The microanalysis, molecular weight (monomer in benzene), IR and multinuclear NMR data and X-ray diffraction study is consistent with the formulation of 1. The Sn atom has a trigonal pyramidal coordination environment formed by a aysmmterically π-bonded terminal C5H5 ring and two symmetrically bridged tert-butoxy groups. The four-coordinate Ge atom lies at the centre of a distorted tetrahedron and is terminally attached to a tert-butoxy group and a Mo(CO)55? fragment. 相似文献
119.
Pablo J. Bruna Volker Krumbach Sigrid D. Peyerimhoff 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract Large-scale multi-reference single and double-excitation configuration interaction (MRD-CI) calculations are employed for the study of the isovalent compounds H2CNH, HLSiNH, hLCPH and H2SiPH in their ground state equilibrium geometry. The dipole moments and charge distributions are given. The vertical excitation energies to the intravalence states 3,1 (n, π*) and 3,1(π,π*) and to the first members of the Rydberg series originating from n and - MO's respectively are predicted; the first two ionization potentials and the Rydberg term values are also calculated. In H2CNH, mixing of Rydberg and valence-shell states with CN stretching is analyzed. The trends in relative stability of electronic and ionized states can be directly related to increased orbital stability of n relative to π as soon as a first-row constituent is replaced by a second-row atom. The calculations explain the diffuse character of the uv spectrum of imines; they treat the molecules H2SiNH and H2SiPH for the first time and present a large number of data for all four molecules which can serve as a basis for future experimental investigations on these and related compounds. 相似文献
120.
Abstract The hydrated salts of the acid H6P6O12, Rb6P6O·aq and M3P6O12·aq (M = Ca, Sr, Ba), that have so far been unknown, have been prepared and studied by X-ray methods, thermal analysis and molecular spectroscopy. It has been found that the anion structure exhibits a chair form with the D3d symmetry. All the salts are stable at laboratory temperature and are completely decomposed on prolonged heating to 80°C prior to complete dehydration. The newly prepared salts of the acid H4P4O10 involve Cs4P4010·1.5 H2O, Tl4P4O10, M2P4O10·x H2O (M = Cu, Ni, Co; x = 10, 2, 6, respectively), Na2MP4O10·x H2O (M = Cu, Ni, Co; x = 8, 8, 4, respectively). They have been studied using X-ray methods, thermal analysis, molecular and reflectance spectra and the magnetic susceptibility. The dehydration of the salts starts at 30 to 40°C and ends by complete decomposition before the completion of dehydration at 150°C. The anion structure for the salt CS4P4O10 in the crystalline state has a chair form with C2 symmetry. However, the anion structure in aqueous solutions approaches a planar arrangement with the D2h symmetry. 相似文献