全文获取类型
收费全文 | 4834篇 |
免费 | 260篇 |
国内免费 | 17篇 |
专业分类
化学 | 4007篇 |
晶体学 | 19篇 |
力学 | 83篇 |
数学 | 497篇 |
物理学 | 505篇 |
出版年
2023年 | 60篇 |
2022年 | 165篇 |
2021年 | 210篇 |
2020年 | 154篇 |
2019年 | 143篇 |
2018年 | 73篇 |
2017年 | 71篇 |
2016年 | 202篇 |
2015年 | 201篇 |
2014年 | 188篇 |
2013年 | 273篇 |
2012年 | 383篇 |
2011年 | 409篇 |
2010年 | 237篇 |
2009年 | 201篇 |
2008年 | 330篇 |
2007年 | 286篇 |
2006年 | 282篇 |
2005年 | 213篇 |
2004年 | 215篇 |
2003年 | 184篇 |
2002年 | 145篇 |
2001年 | 37篇 |
2000年 | 35篇 |
1999年 | 32篇 |
1998年 | 25篇 |
1997年 | 26篇 |
1996年 | 29篇 |
1995年 | 26篇 |
1994年 | 22篇 |
1993年 | 9篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 20篇 |
1984年 | 20篇 |
1983年 | 16篇 |
1982年 | 21篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 16篇 |
1976年 | 11篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1973年 | 5篇 |
排序方式: 共有5111条查询结果,搜索用时 15 毫秒
21.
Demetrio Pitea Laura Bonati Elena Collina Ugo Cosentino Marina Lasagni Giorgio Moro Roberto Todeschini 《Fresenius' Journal of Analytical Chemistry》1994,348(1-2):111-120
Summary The role of multivariate analysis methods in evaluating, rationalizing, and working out complex environmental problems is discussed. The discussion is organized in two sections; a literature analysis of the application of chemometric methods to PCDD/PCDF data interpretation and source correlation and a review of the role of chemometric methods in analysing the results obtained by the Authors studying PCDD/PCDF formation and destruction mechanisms in MSW combustion processes. 相似文献
22.
In a recent paper [17] we proposed a stochastic algorithm which generates optimal probabilities for the decompression of
an image represented by the fixed point of an IFS system (SAOP). We show here that such an algorithm is in fact a non trivial
example of Generalized Random System with Complete Connections. We also exhibit a generalization which could represent the
solution to the inverse problem for an image with grey levels, if a fixed set of contraction maps is available.
Received: 1 July 2002 相似文献
23.
24.
25.
26.
A q × n array with entries from 0, 1,…,q − 1 is said to form a difference matrix if the vector difference (modulo q) of each pair of columns consists of a permutation of [0, 1,… q − 1]; this definition is inverted from the more standard one to be found, e.g., in Colbourn and de Launey (1996). The following idea generalizes this notion: Given an appropriate δ (-[−1, 1]t, a λq × n array will be said to form a (t, q, λ, Δ) sign-balanced matrix if for each choice C1, C2,…, Ct of t columns and for each choice = (1,…,t) Δ of signs, the linear combination ∑j=1t jCj contains (mod q) each entry of [0, 1,…, q − 1] exactly λ times. We consider the following extremal problem in this paper: How large does the number k = k(n, t, q, λ, δ) of rows have to be so that for each choice of t columns and for each choice (1, …, t) of signs in δ, the linear combination ∑j=1t jCj contains each entry of [0, 1,…, q t- 1] at least λ times? We use probabilistic methods, in particular the Lovász local lemma and the Stein-Chen method of Poisson approximation to obtain general (logarithmic) upper bounds on the numbers k(n, t, q, λ, δ), and to provide Poisson approximations for the probability distribution of the number W of deficient sets of t columns, given a random array. It is proved, in addition, that arithmetic modulo q yields the smallest array - in a sense to be described. 相似文献
27.
28.
Wolfgang H. Binder Laura Petraru Robert Sachenshofer Ronald Zirbs 《Monatshefte für Chemie / Chemical Monthly》2006,137(7):835-841
Summary. The surface modification of nanoparticles via azide/alkine-1,3-dipolar cycloaddition-reactions is described. Ligand exchange onto various nanoparticles was monitored by
1H NMR spectroscopy and formed the basis for the attachment of ligands onto the nanoparticles and their subsequent modification
by dipolar cycloaddition reactions. Nanoparticle-surfaces were monitored by binding onto self-assembled monolayers derivatized
with matching supramolecular interactions after derivatization. 相似文献
29.
Let X be a complex connected projective nonsingular algebraic surface endowed with an ample line bundle L, which is spanned by its global sections. Pairs (X, L) as above, with sectional genus g(X, L)=1+(L·(K
X
L))/2=3 are classified by means of the main techniques of adjunction theory. 相似文献
30.
Sunto Fissata una superficie algebrica liscia X sopra un campo algebricamente chiuso e di caratteristica 0, e una curva ridotta C su X, si introduce, per ogni -upla di numeri naturali m1,..., m, uno schema W=W(C, m1,..., m), parametrizzante le curve del sistema lineare ¦C¦ con punti multipli ordinari di molteplicità almeno m1,..., m. Si studia W in relazione con la configurazione delie singolarità e delle componenti irriducibili di C. Si prova in particolare un teorema di «virtuale connessione», che permette di stabilire l'esistenza di curve irriducibili in alcuni di tali schemi W.
Membro del G.N.S.A.G.A. del C.N.R. 相似文献
Membro del G.N.S.A.G.A. del C.N.R. 相似文献