全文获取类型
收费全文 | 1503篇 |
免费 | 25篇 |
国内免费 | 13篇 |
专业分类
化学 | 891篇 |
晶体学 | 6篇 |
力学 | 23篇 |
数学 | 308篇 |
物理学 | 313篇 |
出版年
2021年 | 19篇 |
2020年 | 26篇 |
2019年 | 15篇 |
2018年 | 13篇 |
2016年 | 24篇 |
2015年 | 16篇 |
2014年 | 25篇 |
2013年 | 58篇 |
2012年 | 58篇 |
2011年 | 69篇 |
2010年 | 24篇 |
2009年 | 31篇 |
2008年 | 48篇 |
2007年 | 69篇 |
2006年 | 58篇 |
2005年 | 63篇 |
2004年 | 48篇 |
2003年 | 46篇 |
2002年 | 47篇 |
2001年 | 32篇 |
2000年 | 42篇 |
1999年 | 19篇 |
1998年 | 31篇 |
1997年 | 13篇 |
1996年 | 36篇 |
1995年 | 18篇 |
1994年 | 22篇 |
1993年 | 34篇 |
1992年 | 30篇 |
1991年 | 22篇 |
1990年 | 35篇 |
1989年 | 25篇 |
1988年 | 26篇 |
1987年 | 25篇 |
1986年 | 13篇 |
1985年 | 23篇 |
1984年 | 23篇 |
1983年 | 20篇 |
1982年 | 17篇 |
1981年 | 27篇 |
1980年 | 10篇 |
1979年 | 19篇 |
1978年 | 24篇 |
1977年 | 19篇 |
1976年 | 21篇 |
1975年 | 19篇 |
1974年 | 18篇 |
1973年 | 16篇 |
1969年 | 8篇 |
1968年 | 10篇 |
排序方式: 共有1541条查询结果,搜索用时 312 毫秒
1.
2.
Convective heat transfer from an array of small, cylindrical bodies of arbitrary shape in an unbounded, two-dimensional domain is a singular perturbation problem involving an infinite logarithmic expansion in the small parameter ε, representing the order of magnitude of the size of the bodies. Using the method of matched asymptotic expansions, we formulate a hybrid asymptotic-numerical method to solve for the dimensionless, steady-state temperature. We assume that the velocity field of the fluid surrounding the bodies is arbitrary but known. From our asymptotic solution for an arbitrary velocity field, we present the results for two special cases: a uniform flow field and a simple shear flow field. We demonstrate the asymptotic results of the hybrid method through a number of examples and, in a particular case, we compare these results to an exact analytical solution. 相似文献
3.
CV Tomy D Pal SS Banerjee S Ramakrishnan AK Grover S Bhattacharya MJ Higgins G Balakrishnan McK Paul 《Pramana》2002,58(5-6):925-935
The weakly pinned single crystals of the hexagonal 2H-NbSe2 compound have emerged as prototypes for determining and characterizing the phase boundaries of the possible order-disorder
transformations in the vortex matter. We present here a status report based on the ac and dc magnetization measurements of
the peak effect phenomenon in three crystals of 2H-NbSe2, in which the critical current densities vary over two orders of magnitude. We sketch the generic vortex phase diagram of
a weakly pinned superconductor, which also utilizes theoretical proposals. We also establish the connection between the metastability
effects and pinning. 相似文献
4.
A band-dominant function on the Euclidean sphere embedded in R q+1 is the restriction to this sphere of an entire function of q+1 complex variables having a finite exponential type in each of its variables. We develop a method to represent such a function using finitely many bits, using the values of the function at scattered sites on the sphere. The number of bits required in our representation is asymptotically the same as the metric entropy of the class of such functions with respect to any of the L p norms on the sphere. 相似文献
5.
Thomas M. F. Case G. S. Bland J. Herring A. D. F. Stirling W. G. Tixier S. Boni P. Ward R. C. C. Wells M. R. Langridge S. 《Hyperfine Interactions》2002,141(1-4):471-476
Hyperfine Interactions - Multilayers of Ce/Fe and U/Fe were fabricated by sputtering and studied by X-ray diffraction and reflectivity, Mössbauer spectroscopy and polarised neutron... 相似文献
6.
7.
Don Hadwin K. J. Harrison J. A. Ward 《Proceedings of the American Mathematical Society》2006,134(8):2169-2178
We obtain necessary and sufficient conditions for the existence and the uniqueness of rank-one completions of a partial matrix, and we verify a conjecture of Hadwin and Larson concerning the nature of completely rank-nonincreasing linear functionals defined on pattern subspaces.
8.
Francis J. Narcowich Joseph D. Ward Holger Wendland. 《Mathematics of Computation》2005,74(250):743-763
In this paper we discuss Sobolev bounds on functions that vanish at scattered points in a bounded, Lipschitz domain that satisfies a uniform interior cone condition. The Sobolev spaces involved may have fractional as well as integer order. We then apply these results to obtain estimates for continuous and discrete least squares surface fits via radial basis functions (RBFs). These estimates include situations in which the target function does not belong to the native space of the RBF.
9.
L. Ward 《Optics & Laser Technology》1993,25(6):393-395
The well-known equations for the optical functions of reflectance, transmittance and phase changes on reflection and transmission for a solid material have been rearranged into the form of simple geometric figures in the u, v (n, k) plane. The curves for Fp show a singularity on the n-axis. 相似文献
10.
Summary Laser ablation inductively coupled plasma-source mass spectrometry has been used to determine thirty elements (Na, Mg, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, As, Rb, Sb, Cs, Ba, La, Ce, Nd, Sm, Eu, Dy, Ho, Yb, Hf, Ta, W, Th, U) in seven Chinese reference soils. The Surrey prototype spectrometer was employed with sample ablation by a free-running ruby laser. Concentrations in the soils (GSS-2 to GSS-8) were calculated from elemental responses and sensitivities derived from another soil in the series, namely GSS-1. Comparisons with previous neutron activation analyses are made. Rapid semiquantitative analyses are proved feasible. About eighty percent of the LA-ICP-MS determined concentrations were within a factor of two of the concentrations measured by INAA, and many were considerably closer than this. Precisions were typically in the range 2–10% RSD, but some were considerably poorer for elements present at trace levels. 相似文献