全文获取类型
收费全文 | 723608篇 |
免费 | 6333篇 |
国内免费 | 2065篇 |
专业分类
化学 | 365510篇 |
晶体学 | 10678篇 |
力学 | 36166篇 |
综合类 | 20篇 |
数学 | 96430篇 |
物理学 | 223202篇 |
出版年
2021年 | 6533篇 |
2020年 | 7007篇 |
2019年 | 7914篇 |
2018年 | 10609篇 |
2017年 | 10876篇 |
2016年 | 15141篇 |
2015年 | 8545篇 |
2014年 | 14184篇 |
2013年 | 33116篇 |
2012年 | 25478篇 |
2011年 | 30462篇 |
2010年 | 22591篇 |
2009年 | 22537篇 |
2008年 | 28417篇 |
2007年 | 28103篇 |
2006年 | 25760篇 |
2005年 | 22945篇 |
2004年 | 21301篇 |
2003年 | 19109篇 |
2002年 | 18979篇 |
2001年 | 20983篇 |
2000年 | 16021篇 |
1999年 | 12482篇 |
1998年 | 10637篇 |
1997年 | 10404篇 |
1996年 | 9744篇 |
1995年 | 8705篇 |
1994年 | 8651篇 |
1993年 | 8345篇 |
1992年 | 8954篇 |
1991年 | 9500篇 |
1990年 | 9063篇 |
1989年 | 8934篇 |
1988年 | 8553篇 |
1987年 | 8509篇 |
1986年 | 8117篇 |
1985年 | 10362篇 |
1984年 | 10784篇 |
1983年 | 9021篇 |
1982年 | 9310篇 |
1981年 | 8734篇 |
1980年 | 8425篇 |
1979年 | 9038篇 |
1978年 | 9276篇 |
1977年 | 9115篇 |
1976年 | 9041篇 |
1975年 | 8675篇 |
1974年 | 8511篇 |
1973年 | 8808篇 |
1972年 | 6321篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
Electron mobility has been calculated in a number of binary II–VI compound semiconductors using a displaced Maxwellian distribution function and taking the various scattering mechanisms into consideration at different lattice temperatures and for various amounts of ionized impurity concentrations. It is observed that the low field mobility values can be expressed by a cubic power relationship with lattice temperature and with ionized impurity concentration using a least mean square fit technique with an accuracy better than 5 per cent. Similarly, the field dependence of mobility can also be expressed as a power series of the applied electric field. It is suggested that these equations can be profitably used for a quick estimation of mobility values as a check on experiments and also as sufficiently accurate formulae for simulation and modelling purposes. 相似文献
182.
183.
V. A. Artamonov 《Journal of Mathematical Sciences》1991,57(2):2959-3009
A survey of the development of the theory of universal algebras in the years 1976–1988. Such basic directions of development of this theory as classes of universal algebras (varieties, quasivarieties, etc.), Mal'tsev conditions, congruences, sheaves, homomorphisms, subalgebras, products of algebras, clones of operations, completeness, systems of equations in algeberas, and connections with computer mathematics show up in it. Considerable attention is given to concrete classes of algebras (p-algebras, BCK-algebras, unary algebras, etc.).Translated from Itogi Nauki i Tekhniki, Seriya Algebra, Topologiya, Geometriya, Vol. 27, pp. 45–124, 1989. 相似文献
184.
185.
The drawbacks of our earlier report of preparing fuel cell catalyst arrays by borohydride reduction of inkjet prepared arrays of metal salts are discussed along with the need for inclusion of state-of-the-art metrics in all array screening. An alternative method for screening of hydrogen/air cathode catalysts, direct methanol fuel cell (DMFC) anode catalysts, and catalyst loading studies is provided. State-of-the-art Johnson Matthey catalysts were used in control experiments to demonstrate the utility of the array fuel cell for high throughput screening of fuel cell catalysts in the 3-4 mg/cm2 range. This report lays out hard learned rules for high throughput screening and demonstrates that the array fuel cell can be used for very precise screening of libraries of membrane electrode assembly (MEA) components without the pitfalls discussed in the introduction. 相似文献
186.
187.
A. L. Chistov 《Journal of Mathematical Sciences》2006,138(3):5733-5752
Consider a projective algebraic variety W which is an irreducible component of the set of all common zeros of a family of
homogeneous polynomials of degrees less than d in n + 1 variables over a field of zero characteristic. Consider a dominant
rational morphism from W to W′ given by homogeneous polynomials of degree d′. We suggest algorithms for constructing objects
in general position related to this morphism. They generalize some algorithms from the first part of the paper to the case
dim W > dim W′. These algorithms are deterministic and polynomial in (dd′)n and the size of the input. Bibliography: 12 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 325, 2005, pp. 181–224. 相似文献
188.
S. A. Nazarov 《Journal of Mathematical Sciences》2006,132(1):91-102
For the second order derivatives of eigenvectors in a thin anisotropic heterogeneous plate Ωh, we derive estimates of their weighted L2-norms with majorants whose dependence on the plate thickness h and on the eigenvalue number is expressed explicitly. These
estimates maintain the asymptotic sharpness throughout the entire spectrum, whereas inside its low-frequency band the majorants
remain bounded as h → +0. The latter is a rather unexpected fact, because for the first eigenfunction u1 of a similar boundary-value problem for a scalar second order differential operator with variable coefficients, the norm
‖∇
x
2
u0; L2(Ωh)‖ is of order h−1 and grows as h tends to zero. Bibliography: 35 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 308, 2004, pp. 161–180. 相似文献
189.
In a two-dimensional array of magnetic moments with planar magnetization and relatively weak anisotropy in the basal plane, a stepwise phase transition is induced by an external magnetic field parallel to the easy axis of the system. This transition is similar to the spin flop phase transition in weakly anisotropic Heisenberg antiferromagnets with the significant difference that it is accompanied by the rearrangement of the sublattice structure of the magnet; i.e., it can be interpreted as a topological transition. The transition should manifest itself for arrays of submicron magnetic particles (magnetic dots) on nonmagnetic substrates, which have recently become the object of intensive research. 相似文献
190.
S. K. Godunov V. T. Zhukov O. B. Feodoritova 《Computational Mathematics and Mathematical Physics》2006,46(6):971-982
An algorithm is constructed for calculating invariant subspaces of symmetric hyperbolic systems arising in electromagnetic, acoustic, and elasticity problems. Discrete approximations are calculated for subspaces that correspond to minimal eigenvalues and smooth eigenfunctions. Difficulties related to the presence of an infinite-dimensional kernel in the differential operator are successfully handled. The efficiency of the algorithm is demonstrated using acoustics equations. 相似文献