全文获取类型
收费全文 | 10883篇 |
免费 | 353篇 |
国内免费 | 33篇 |
专业分类
化学 | 7465篇 |
晶体学 | 25篇 |
力学 | 170篇 |
综合类 | 1篇 |
数学 | 2113篇 |
物理学 | 1495篇 |
出版年
2020年 | 79篇 |
2019年 | 92篇 |
2016年 | 200篇 |
2015年 | 185篇 |
2014年 | 240篇 |
2013年 | 424篇 |
2012年 | 297篇 |
2011年 | 308篇 |
2010年 | 251篇 |
2009年 | 234篇 |
2008年 | 319篇 |
2007年 | 312篇 |
2006年 | 318篇 |
2005年 | 299篇 |
2004年 | 286篇 |
2003年 | 286篇 |
2002年 | 306篇 |
2001年 | 199篇 |
2000年 | 186篇 |
1999年 | 124篇 |
1998年 | 121篇 |
1997年 | 140篇 |
1996年 | 143篇 |
1995年 | 131篇 |
1994年 | 138篇 |
1993年 | 152篇 |
1992年 | 161篇 |
1991年 | 118篇 |
1990年 | 136篇 |
1989年 | 141篇 |
1988年 | 139篇 |
1987年 | 150篇 |
1986年 | 117篇 |
1985年 | 230篇 |
1984年 | 197篇 |
1983年 | 128篇 |
1982年 | 173篇 |
1981年 | 166篇 |
1980年 | 203篇 |
1979年 | 198篇 |
1978年 | 201篇 |
1977年 | 230篇 |
1976年 | 190篇 |
1975年 | 180篇 |
1974年 | 139篇 |
1973年 | 189篇 |
1972年 | 94篇 |
1971年 | 90篇 |
1970年 | 70篇 |
1933年 | 67篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Robin F. Weitkamp Beate Neumann Hans‐Georg Stammler Berthold Hoge 《Angewandte Chemie (International ed. in English)》2020,59(14):5494-5499
We report on the first examples of isolated silanol–silanolate anions, obtained by utilizing weakly coordinating phosphazenium counterions. The silanolate anions were synthesized from the recently published phosphazenium hydroxide hydrate salt with siloxanes. The silanol–silanolate anions are postulated intermediates in the hydroxide‐mediated polymerization of aryl and alkyl siloxanes. The silanolate anions are strong nucleophiles because of the weakly coordinating character of the phosphazenium cation, which is perceptible in their activity in polysiloxane depolymerization. 相似文献
2.
Let A be a symmetric matrix of size n×n with entries in some (commutative) field K. We study the possibility of decomposing A into two blocks by conjugation by an orthogonal matrix T∈Matn(K). We say that A is absolutely indecomposable if it is indecomposable over every extension of the base field. If K is formally real then every symmetric matrix A diagonalizes orthogonally over the real closure of K. Assume that K is a not formally real and of level s. We prove that in Matn(K) there exist symmetric, absolutely indecomposable matrices iff n is congruent to 0, 1 or −1 modulo 2s. 相似文献
3.
D.W. Mueller JrA.L. Crosbie 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,74(1):43-68
Three-dimensional radiative transfer in an anisotropic scattering medium exposed to spatially varying, collimated radiation is studied. The generalized reflection function for a semi-infinite medium with a very general scattering phase function is the focus of this investigation. An integral transform is used to reduce the three-dimensional transport equation to a one-dimensional form, and a modified Ambarzumian's method is applied to formulate a nonlinear integral equation for the generalized reflection function. The integration is over both the polar and azimuthal angles; hence, the integral equation is said to be in the double-integral form. The double-integral, reflection function formulation can handle a variety of anisotropic phase functions and does not require an expansion of the phase function in a Legendre polynomial series. Complicated kernel transformations of previous single-integral studies are eliminated. Single and double scattering approximations are developed. Numerical results are presented for a Rayleigh phase function to illustrate the computational characteristics of the method and are compared to results obtained with the single-integral method. Agreement between the two approaches is excellent; however, as the transform variable increases beyond five the number of quadrature points required for the double-integral method to produce accurate solutions significantly increases. A new interpolation scheme produces accurate results when the transform variable is large. 相似文献
4.
5.
6.
7.
8.
Hans Maaß 《Mathematische Annalen》1941,118(1):312-318
Ohne Zusammenfassung 相似文献
9.
Keller Teichmann Hans Pfeiffer W. Langenbeck A. Reid Heinrich Menzel Th. Höpner W. Mühlsteph M. Ulmann Geib R. E. Liesegang 《Colloid and polymer science》1939,87(1):100-104
Ohne Zusammenfassung 相似文献
10.
Erich Miersemann Hans D. Mittelmann W. Trnig 《Mathematical Methods in the Applied Sciences》1989,11(1):95-104
In this paper we generalize recent theoretical results on the local continuation of parameter-dependent non-linear variational inequalities. The variational inequalities are rather general and describe, for example, the buckling of beams, plates or shells subject to obstacles. Under a technical hypothesis that is satisfied by the simply supported beam, we obtain the existence of a continuation of both the solution and the eigenvalue with respect to a local parameter. A numerical continuation method is presented that easily overcomes turning points. Numerical results are presented for the non-linear beam. 相似文献