全文获取类型
收费全文 | 34892篇 |
免费 | 1269篇 |
国内免费 | 267篇 |
专业分类
化学 | 24671篇 |
晶体学 | 280篇 |
力学 | 686篇 |
综合类 | 1篇 |
数学 | 5989篇 |
物理学 | 4801篇 |
出版年
2023年 | 167篇 |
2022年 | 324篇 |
2021年 | 430篇 |
2020年 | 611篇 |
2019年 | 599篇 |
2018年 | 418篇 |
2017年 | 389篇 |
2016年 | 943篇 |
2015年 | 833篇 |
2014年 | 1007篇 |
2013年 | 1715篇 |
2012年 | 2180篇 |
2011年 | 2464篇 |
2010年 | 1330篇 |
2009年 | 1181篇 |
2008年 | 2277篇 |
2007年 | 2094篇 |
2006年 | 2117篇 |
2005年 | 1968篇 |
2004年 | 1687篇 |
2003年 | 1384篇 |
2002年 | 1335篇 |
2001年 | 489篇 |
2000年 | 471篇 |
1999年 | 408篇 |
1998年 | 399篇 |
1997年 | 420篇 |
1996年 | 450篇 |
1995年 | 317篇 |
1994年 | 368篇 |
1993年 | 335篇 |
1992年 | 305篇 |
1991年 | 279篇 |
1990年 | 244篇 |
1989年 | 214篇 |
1988年 | 210篇 |
1987年 | 221篇 |
1986年 | 180篇 |
1985年 | 376篇 |
1984年 | 333篇 |
1983年 | 280篇 |
1982年 | 342篇 |
1981年 | 278篇 |
1980年 | 291篇 |
1979年 | 241篇 |
1978年 | 227篇 |
1977年 | 219篇 |
1976年 | 208篇 |
1975年 | 188篇 |
1974年 | 160篇 |
排序方式: 共有10000条查询结果,搜索用时 688 毫秒
181.
We provide a new approach to filter products of C0-semigroups and prove a spectral theorem for the generator and its filter product. In a similar fashion, we construct ultraproducts of strongly continuous unitary representations of locally compact groups and study spectral theoretic connections between the representations and their ultraproducts. In the case of Lie groups, our investigations are extended to the infinitesimal representation. 相似文献
182.
Michael Szydlo 《Journal of Number Theory》2004,104(1):75-99
Kodaira and Néron classified and described the geometry of the special fibers of the Néron model of an elliptic curve defined over a discrete valuation ring with a perfect residue field. Tate described an algorithm to determine the special fiber type by manipulating the Weierstrass equation. In the case of non-perfect residue fields, we discover new fiber types which are not on the Kodaira-Néron list. We describe these new types and extend Tate's algorithm to deal with all discrete valuation rings. Specifically, we show how to translate a Weierstrass equation into a form where the reduction type may be easily determined. Having determined the special fiber type, we construct the regular model of the curve with explicit blow-up calculations. We also provide tables that serve as a simple reference for the algorithm and which succinctly summarize the results. 相似文献
183.
184.
Andrey Semichaevsky Markus E. Testorf Robert V. McGahan Michael A. Fiddy 《Waves in Random and Complex Media》2004,14(2):S415-S434
A linear spectral estimation technique, the PDFT algorithm, is used as part of a nonlinear iterative reconstruction scheme to obtain improved radar images. The iterative PDFT algorithm is used to address the limited resolution problem inherent to imaging objects buried in soil and hidden under foliage. This is achieved by subsequent application of two properties of the PDFT algorithm: the energy parameter of the PDFT algorithm is used to determine the target shape, while the shape information in turn is used to obtain super-resolved images. We describe algorithms able to exploit both properties automatically and without manual intervention. Two methods are investigated in particular, one iteratively optimizing the constraints by monitoring the energy parameter, the other method computing energy values for all points, from which a weighted prior function is determined. In addition, we discuss variants of both algorithm which provide an optimized trade-off between computation time and performance. Additional attention is given to situations, where a known target is embedded in an unknown background. Imaging results are presented for both synthetic and measured data. 相似文献
185.
Let G be a d‐regular graph G on n vertices. Suppose that the adjacency matrix of G is such that the eigenvalue λ which is second largest in absolute value satisfies λ = o(d). Let Gp with p = α/d be obtained from G by including each edge of G independently with probability p. We show that if α < 1, then whp the maximum component size of Gp is O(log n) and if α > 1, then Gp contains a unique giant component of size Ω(n), with all other components of size O(log n). © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 2004 相似文献
186.
187.
Microemulsions are becoming increasingly complex systems by containing more sophisticated surfactants, polymers, biomolecules, inorganic nanoparticles, etc. The detailed understanding of such more complex systems requires increasingly more refined and comprehensive characterisation. This is typically done by the combination of complementary techniques and is aided by the fact that several experimental methods have been improved (such as electron microscopy) in recent times, new ones have become available (such as fluorescence correlation spectroscopy), and the theoretical understanding of structural data is advancing. 相似文献
188.
Michael C. W. Chan Dr. 《化学:亚洲杂志》2008,3(1):18-27
The notion of weak attractive ligand–polymer interactions is introduced, and its potential application, importance, and conceptual links with “cooperative” ligand–substrate interactions are discussed. Synthetic models of weak attractive ligand–polymer interactions are described, in which intramolecular weak C? H???F? C interactions (the existence of which remains contentious) have been detected by NMR spectroscopy and neutron and X‐ray diffraction experiments. These C? H???F? C interactions carry important implications for the design of catalysts for olefin polymerization, because they provide support for the practical feasibility of ortho‐F???Hβ ligand–polymer contacts proposed for living Group 4 fluorinated phenoxyimine catalysts. The notion of weak attractive noncovalent interactions between an “active” ligand and the growing polymer chain is a novel concept in polyolefin catalysis. 相似文献
189.
190.
Let Hn be an n-dimensional Haar subspace of
and let Hn−1 be a Haar subspace of Hn of dimension n−1. In this note we show (Theorem 6) that if the norm of a minimal projection from Hn onto Hn−1 is greater than 1, then this projection is an interpolating projection. This is a surprising result in comparison with Cheney and Morris (J. Reine Angew. Math. 270 (1974) 61 (see also (Lecture Notes in Mathematics, Vol. 1449, Springer, Berlin, Heilderberg, New York, 1990, Corollary III.2.12, p. 104) which shows that there is no interpolating minimal projection from C[a,b] onto the space of polynomials of degree n, (n2). Moreover, this minimal projection is unique (Theorem 9). In particular, Theorem 6 holds for polynomial spaces, generalizing a result of Prophet [(J. Approx. Theory 85 (1996) 27), Theorem 2.1]. 相似文献