全文获取类型
收费全文 | 118359篇 |
免费 | 8368篇 |
国内免费 | 12711篇 |
专业分类
化学 | 71266篇 |
晶体学 | 1153篇 |
力学 | 2462篇 |
综合类 | 847篇 |
数学 | 12923篇 |
物理学 | 19633篇 |
无线电 | 31154篇 |
出版年
2024年 | 339篇 |
2023年 | 1447篇 |
2022年 | 2603篇 |
2021年 | 2572篇 |
2020年 | 2985篇 |
2019年 | 2890篇 |
2018年 | 2687篇 |
2017年 | 3861篇 |
2016年 | 3884篇 |
2015年 | 3737篇 |
2014年 | 4749篇 |
2013年 | 8109篇 |
2012年 | 7956篇 |
2011年 | 7034篇 |
2010年 | 5644篇 |
2009年 | 7268篇 |
2008年 | 7620篇 |
2007年 | 8120篇 |
2006年 | 7518篇 |
2005年 | 6404篇 |
2004年 | 5831篇 |
2003年 | 4773篇 |
2002年 | 5723篇 |
2001年 | 3428篇 |
2000年 | 3084篇 |
1999年 | 2828篇 |
1998年 | 2502篇 |
1997年 | 2001篇 |
1996年 | 1713篇 |
1995年 | 1638篇 |
1994年 | 1400篇 |
1993年 | 1134篇 |
1992年 | 1043篇 |
1991年 | 743篇 |
1990年 | 585篇 |
1989年 | 545篇 |
1988年 | 399篇 |
1987年 | 311篇 |
1986年 | 290篇 |
1985年 | 230篇 |
1984年 | 249篇 |
1983年 | 144篇 |
1982年 | 214篇 |
1981年 | 181篇 |
1980年 | 197篇 |
1979年 | 185篇 |
1978年 | 169篇 |
1977年 | 123篇 |
1976年 | 109篇 |
1973年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
本文在一类 Lp位势V(x)下建立了广义Schrodinger算子H=(-Δ)m+V(x)在C∞0(Rn)上的本质自伴性,给出了H的本质谱的分布. 相似文献
73.
Let T and S be invertible measure preserving transformations of a probability measure space (X, ℬ, μ). We prove that if the group generated by T and S is nilpotent, then exists in L
2-norm for any u, v∈L
∞(X, ℬ, μ). We also show that for A∈ℬ with μ(A)>0 one has . By the way of contrast, we bring examples showing that if measure preserving transformations T, S generate a solvable group, then (i) the above limits do not have to exist; (ii) the double recurrence property fails, that
is, for some A∈ℬ, μ(A)>0, one may have μ(A∩T
-n
A∩S
-
n
A)=0 for all n∈ℕ. Finally, we show that when T and S generate a nilpotent group of class ≤c, in L
2(X) for all u, v∈L
∞(X) if and only if T×S is ergodic on X×X and the group generated by T
-1
S, T
-2
S
2,..., T
-c
S
c
acts ergodically on X.
Oblatum 19-V-2000 & 5-VII-2001?Published online: 12 October 2001 相似文献
74.
Balázs Szendröi 《Mathematische Zeitschrift》2002,240(2):233-241
This note shows that a certain toric quotient of the quintic Calabi-Yau threefold in provides a counterexample to a recent conjecture of Cox and Katz concerning nef cones of toric hypersurfaces.
Received: 8 February 2001; in final form: 17 September 2001 / Published online: 1 February 2002 相似文献
75.
meso-Tetra(n-hexyloxycarbonyl)porphyrin was found to be converted into porphine, the mother compound of porphyrins, in a 77% yield when heated in aqueous sulfuric acid at 180 °C over 30 min under an inert atmosphere. The observation demonstrates that the substituted porphyrin serves as a novel and useful precursor for porphine. 相似文献
76.
We obtain upper bounds for the tail distribution of the first nonnegative sum of a random walk and for the moments of the overshoot over an arbitrary nonnegative level if the expectation of jumps is positive and close to zero. In addition, we find an estimate for the expectation of the first ladder epoch. 相似文献
77.
78.
Kasper K. Berthelsen Jesper Møller 《Bulletin of the Brazilian Mathematical Society》2002,33(3):351-367
This primer provides a self-contained exposition of the case where spatial birth-and-death processes are used for perfect
simulation of locally stable point processes. Particularly, a simple dominating coupling from the past (CFTP) algorithm and
the CFTP algorithms introduced in [13], [14], and [5] are studied. Some empirical results for the algorithms are discussed.
Received: 30 June 2002 相似文献
79.
80.
Let G=(V(G),E(G)) be a graph. A (n,G, λ)‐GD is a partition of the edges of λKn into subgraphs (G‐blocks), each of which is isomorphic to G. The (n,G,λ)‐GD is named as graph design for G or G‐decomposition. The large set of (n,G,λ)‐GD is denoted by (n,G,λ)‐LGD. In this work, we obtain the existence spectrum of (n,P3,λ)‐LGD. © 2002 Wiley Periodicals, Inc. J Combin Designs 10: 151–159, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10008 相似文献