全文获取类型
收费全文 | 521791篇 |
免费 | 5289篇 |
国内免费 | 1696篇 |
专业分类
化学 | 265650篇 |
晶体学 | 7486篇 |
力学 | 24392篇 |
综合类 | 14篇 |
数学 | 72580篇 |
物理学 | 158654篇 |
出版年
2020年 | 2829篇 |
2019年 | 2810篇 |
2018年 | 11501篇 |
2017年 | 12375篇 |
2016年 | 9440篇 |
2015年 | 5546篇 |
2014年 | 6348篇 |
2013年 | 19562篇 |
2012年 | 19060篇 |
2011年 | 30308篇 |
2010年 | 18640篇 |
2009年 | 18603篇 |
2008年 | 27058篇 |
2007年 | 30464篇 |
2006年 | 17073篇 |
2005年 | 22387篇 |
2004年 | 17340篇 |
2003年 | 15333篇 |
2002年 | 13213篇 |
2001年 | 13795篇 |
2000年 | 10778篇 |
1999年 | 8300篇 |
1998年 | 6632篇 |
1997年 | 6449篇 |
1996年 | 6579篇 |
1995年 | 5965篇 |
1994年 | 5590篇 |
1993年 | 5313篇 |
1992年 | 5951篇 |
1991年 | 5814篇 |
1990年 | 5352篇 |
1989年 | 5219篇 |
1988年 | 5516篇 |
1987年 | 5125篇 |
1986年 | 4946篇 |
1985年 | 7202篇 |
1984年 | 7244篇 |
1983年 | 5903篇 |
1982年 | 6357篇 |
1981年 | 6300篇 |
1980年 | 6090篇 |
1979年 | 6176篇 |
1978年 | 6240篇 |
1977年 | 6120篇 |
1976年 | 6049篇 |
1975年 | 5918篇 |
1974年 | 5716篇 |
1973年 | 5973篇 |
1972年 | 3467篇 |
1971年 | 2481篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Athanassios G. Bratsos 《Numerical Algorithms》2007,46(1):45-58
A predictor–corrector (P-C) scheme is applied successfully to a nonlinear method arising from the use of rational approximants
to the matrix-exponential term in a three-time level recurrence relation. The resulting nonlinear finite-difference scheme,
which is analyzed for local truncation error and stability, is solved using a P-C scheme, in which the predictor and the corrector
are explicit schemes of order 2. This scheme is accelerated by using a modification (MPC) in which the already evaluated values
are used for the corrector. The behaviour of the P-C/MPC schemes is tested numerically on the Boussinesq equation already
known from the bibliography free of boundary conditions. The numerical results are derived for both the bad and the good Boussinesq
equation and conclusions from the relevant known results are derived.
相似文献
992.
Bernhard G. Bodmann Vern I. Paulsen Soha A. Abdulbaki 《Journal of Fourier Analysis and Applications》2007,13(3):285-307
We study the performance of finite frames for the encoding of vectors by applying standard higher-order sigma-delta quantization
to the frame coefficients. Our results are valid for any quantizer with accuracy ε > 0 operating in the no-overload regime.
The frames under consideration are obtained from regular sampling of a path in a Hilbert space. In order to achieve error
bounds that are comparable to results on higher-order sigma-delta for the quantization of oversampled bandlimited functions,
we construct frame paths that terminate smoothly in the zero vector, that is, with an appropriate number of vanishing derivatives
at the endpoint. 相似文献
993.
Yu. K. Dem’yanovich 《Journal of Mathematical Sciences》2007,144(6):4548-4567
On a sequence of embedded nonuniform grids, chains of embedded spaces of minimal splines (not necessarily polynomial) are
constructed. The wavelet decomposition is given. The basis wavelets are compactly supported and admit simple analytic representation.
The corresponding decomposition and reconstruction formulas are derived. The variety of spaces under consideration is identified
with the variety of complete sequences of points of the direct product of an interval and a projective plane. Bibliography:
20 titles.
__________
Translated from Problemy Matematicheskogo Analiza, No. 35, 2007, pp. 15–31 相似文献
994.
995.
A base of the universal multiplicative envelope of the free Malcev superalgebra ℳ on one odd generator is constructed. Some
corollaries for skew-symmetric functions and central elements in free Malcev and free alternative algebras are obtained. Moreover,
a base of the Poisson-Malcev superalgebra of ℳ is constructed. As a corollary, a set of elements that spans the free alternative
superalgebra on one odd generator is obtained.
__________
Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 10, No. 4, pp. 97–106, 2004. 相似文献
996.
997.
It is demonstrated theoretically that the initial (both elastic and viscous) magnetic susceptibility components for nanocrystalline
magnets caused by the processes of rotations (in the region of linear response) have resonant rather than relaxation character
typical already for the susceptibility component caused by displacements of domain boundaries.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 88–92, June, 2007. 相似文献
998.
999.
We observe that a term of the WZW-type can be added to the Lagrangian of the Poisson σ-model in such a way that the algebra of the first class constraints remains closed. This leads to a natural generalization of the concept of Poisson geometry. The resulting “WZW–Poisson” manifold M is characterized by a bivector Π and by a closed three-form H such that 1/2[Π,Π]Schouten=H,ΠΠΠ. 相似文献
1000.
MDF materials are chemically bonded ceramic materials free of the macrodefects typical of hydraulic cement-based materials. MDF materials arising through reactions of sulfo-aluminate-ferrite belitic (SAFB) clinkers and/or Portland cements (PC) with two types of water-soluble polymer (hydroxy-propylmethyl cellulose {HPMC}, polyphosphate glass {poly-P}) are discussed. Mixes of low energy SAFB clinkers with Portland cement, HPMC and, especially poly-P comprise promising cross-linked compositions additional to the better known MDF materials formed from high alumina cement with polyvinylalcohol/acetate. The principles of co-ordination of P and C atoms (of the polymer) with Al and Fe atoms (originating from the cement) are highlighted from spectroscopic information on next-nearest-neighbour interactions, along with the effects of second co-ordination spheres. Polymers modify the interface through functional bonding/grafting of polymer chains onto the surfaces of cement grains. Both the cross-linked atomic structure and the interface coincide well with the model of functional polymers and represent a new type of atomic-level structure in polymer-modified cements. Interpretation is based on previous magnetic resonance and thermal analysis studies. The compactness of Al(Fe)-O-P cross-links reduces transport through the interfaces, increasing the interfacial interactions and resisting the unfavourable uptake of moisture and carbonation. 相似文献