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541.
用非笛卡儿张量分析螺旋状矩形管的流动特性 总被引:1,自引:0,他引:1
利用基于带有物理基的非笛卡儿张量分析的广义矩阵法,在非正交的螺旋线坐标系中。推导出了连续性方程和Navier-Stokes方程组.并利用有限元法.解出了上述偏微分方程组.借以分析研究了螺旋状矩形管在定带、充分发展的层流流动中,管的曲率、挠率和横截面倾斜角对流动特性的种种影响,并适当地与环状矩形管作了比较,从中探索出流动参数的变化对流动特性变化影响的规律。 相似文献
542.
543.
The Newtonian gravitational constantG is determined by means of the swing time method at the Cave Laboratory of Center for Gravitational Experiment of Huazhong
University of Science and Technology. The result value ofG is (6.669 0 ± 0.001 6) × 10-11 m3·kg-1·s-2, which is consistent with the CODATA value of G obtained by Cohen and Taylor in 3σ.
Project supported by the National Natural Science Foundation of China (Grant Nos. 19425008 and 49674246). 相似文献
544.
本以裂纹的翘曲位移间断为基本未知函数,把带裂纹圆柱体的扭转问题化为求解一组强奇性积分方程,并利用数值法,对星形及其不同形状裂纹圆柱体的抗扭刚度和应力强度因子作了数值计算,计算结果令人满意。 相似文献
545.
球面各向同性圆锥其顶端受力时的弹性力学解 总被引:1,自引:1,他引:0
本文在文[9]的基础上,研究球面各向同性圆锥顶端作用集中力,集中力矩时的位移和应力分布。最后讨论了空心锥顶端受力的问题。 相似文献
546.
Andrew Ranicki 《K-Theory》1987,1(2):115-170
The algebraic K-theory product K
0(A) K
1
B K
1(A B) for rings A, B is given a chain complex interpretation, using the absolute torsion invariant introduced in Part I. Given a finitely dominated A-module chain complex C and a round finite B-module chain complex D, it is shown that the A B-module chain complex C D has a round finite chain homotopy structure. Thus, if X is a finitely dominated CW complex and Y is a round finite CW complex, the product X × Y is a CW complex with a round finite homotopy structure. 相似文献
547.
Several mechanisms have been considered as principal factors in enhancing the catalytic reaction velocity of enzymes: approximation, covalent catalysis, general acid-based catalysis, and strain. Among them, the strain on the substrate and/or the enzyme is often found to be brought about on association of the substrate and the enzyme. If this strain is released in the transition state, it contributes to enhancing the k(cat) value, although it does not change the k(cat)/K(m) value. In aspartate aminotransferase, however, we found by analysis of the Schiff base pK(a) values that the unliganded enzyme carries a strain in the protonated Schiff base formed between the coenzyme pyridoxal phosphate and a lysine residue. This bond is cleaved in most of the reaction intermediates, including the transition state. As a result, the activation energy between the free enzyme plus substrate and the transition state is decreased by 16 kJ/mol, equal to the value of the strain energy. The net effect of this strain is enhancement (10(3)-fold) of the catalytic efficiency in terms of k(cat)/K(m), the more important indicator of the catalytic efficiency at low concentration of the substrate. 相似文献
548.
Parsons J Holmes JB Rojas JM Tsai J Strauss CE 《Journal of computational chemistry》2005,26(10):1063-1068
Many applications require a method for translating a large list of bond angles and bond lengths to precise atomic Cartesian coordinates. This simple but computationally consuming task occurs ubiquitously in modeling proteins, DNA, and other polymers as well as in many other fields such as robotics. To find an optimal method, algorithms can be compared by a number of operations, speed, intrinsic numerical stability, and parallelization. We discuss five established methods for growing a protein backbone by serial chain extension from bond angles and bond lengths. We introduce the Natural Extension Reference Frame (NeRF) method developed for Rosetta's chain extension subroutine, as well as an improved implementation. In comparison to traditional two-step rotations, vector algebra, or Quaternion product algorithms, the NeRF algorithm is superior for this application: it requires 47% fewer floating point operations, demonstrates the best intrinsic numerical stability, and offers prospects for parallel processor acceleration. The NeRF formalism factors the mathematical operations of chain extension into two independent terms with orthogonal subsets of the dependent variables; the apparent irreducibility of these factors hint that the minimal operation set may have been identified. Benchmarks are made on Intel Pentium and Motorola PowerPC CPUs. 相似文献
549.
A. Predoi-Cross R. M. Lees H. Lichau M. Winnewisser J. R. Drummond 《International Journal of Infrared and Millimeter Waves》1997,18(11):2047-2061
The rotational millimeter-wave spectrum of CH3
18OH has been revisited, and 162 transitions of botha- andb-types have been measured in the 119–165 GHz spectral range. The spectrum was recorded using the frequency-modulated millimeter-wave
spectrometer at the Justus-Liebig-Universit?t in Gie?en. The CH3
18OH transition assignments were based on energy levels obtained from the far-infrared analysis of S. Zhao (Ph.D. thesis, University
of New Brunswick, 1993) using the "Ritz" program of G. Moruzziet al. (J. Mol. Spectrosc.167, 156 (1994)) for direct energy level fitting. The relatively low residuals between calculated and observed frequencies highlight
the good quality of the results from this program. The newly measured transitions combined with those existent in the literature
have been included in least-squares fits to improve the set of rotational, torsional and centrifugal distortion constants
for O-18 methanol. 相似文献
550.
Ya-nan LIN & Lin XIN Department of Mathematics Xiamen University Xiamen China Department of Mathematics Fujian Normal University Puzhou China 《中国科学A辑(英文版)》2007,50(1):13-26
Motivated by the concept of a torsion pair in a pre-triangulated category induced by Beligiannis and Reiten, the notion of a left (right) torsion pair in the left (right) triangulated category is introduced and investigated. We provide new connections between different aspects of torsion pairs in one-sided triangulated categories, pre-triangulated categories, stable categories and derived categories. 相似文献