全文获取类型
收费全文 | 10654篇 |
免费 | 751篇 |
国内免费 | 472篇 |
专业分类
化学 | 3246篇 |
晶体学 | 35篇 |
力学 | 660篇 |
综合类 | 69篇 |
数学 | 5573篇 |
物理学 | 2294篇 |
出版年
2024年 | 18篇 |
2023年 | 168篇 |
2022年 | 265篇 |
2021年 | 319篇 |
2020年 | 417篇 |
2019年 | 354篇 |
2018年 | 365篇 |
2017年 | 399篇 |
2016年 | 353篇 |
2015年 | 322篇 |
2014年 | 566篇 |
2013年 | 1277篇 |
2012年 | 582篇 |
2011年 | 611篇 |
2010年 | 482篇 |
2009年 | 729篇 |
2008年 | 765篇 |
2007年 | 582篇 |
2006年 | 481篇 |
2005年 | 456篇 |
2004年 | 338篇 |
2003年 | 250篇 |
2002年 | 225篇 |
2001年 | 148篇 |
2000年 | 166篇 |
1999年 | 196篇 |
1998年 | 153篇 |
1997年 | 140篇 |
1996年 | 125篇 |
1995年 | 78篇 |
1994年 | 67篇 |
1993年 | 57篇 |
1992年 | 52篇 |
1991年 | 28篇 |
1990年 | 20篇 |
1989年 | 25篇 |
1988年 | 17篇 |
1987年 | 18篇 |
1986年 | 17篇 |
1985年 | 45篇 |
1984年 | 52篇 |
1983年 | 20篇 |
1982年 | 26篇 |
1981年 | 26篇 |
1980年 | 17篇 |
1979年 | 16篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
罗尔定理证明一类存在性问题 总被引:1,自引:0,他引:1
提出罗尔定理证明一类存在性问题的方法,采用拉格朗日中值定理或柯西中值定理来证明这类问题往往需要构造精巧的辅助函数,我们还指出了这种方法的一般性. 相似文献
42.
D.L. Skuratov Yu.L. Ratis I.A. Selezneva J. Pérez P. Fernández de Córdoba J.F. Urchueguía 《Applied Mathematical Modelling》2007
This paper deals with modelling the workpiece temperature field produced during the grinding process. The proposed model is given in terms of a two-dimensional boundary-value problem where the interdependence among the grinding wheel, the workpiece and the coolant is described by two variable functions in the boundary condition. An explicit integral form solution is constructed using the Laplace and Fourier transforms and the Green’s function method. 相似文献
43.
Kwang Seok Oh 《Applied Surface Science》2007,254(3):677-681
Catalytic decomposition of NO over Cu-Os/13X has been carried out in a tubular fixed bed reactor at atmospheric pressure and the results were compared with literature data performed by high-throughput screening (HTS). The activity and durability of Cu-Os/13X prepared by conventional ion-exchange method have been investigated in the presence of H2O and SO2. It was found that Cu-Os/13X prepared by ion-exchange shows a high activity in a wide temperature range in selective catalytic reduction (SCR) of NO with C3H6 compared to Cu/13X, proving the existence of more NO adsorption site on Cu-Os/13X. However, Cu-Os/13X exhibited low activity in the presence of water, and was quite different from the result reported in literature. SO2 resistance is also low and does not recover its original activity when the SO2 was blocked in the feed gas stream. This result suggested that catalytic activity between combinatorial screening and conventional testing should be compared to confirm the validity of high-throughput screening. 相似文献
44.
Djamel Meraghni Abdelhakim Necir 《Methodology and Computing in Applied Probability》2007,9(4):557-572
The characteristic exponent α of a Lévy-stable law S
α
(σ, β, μ) was thoroughly studied as the extreme value index of a heavy tailed distribution. For 1 < α < 2, Peng (Statist. Probab. Lett. 52: 255–264, 2001) has proposed, via the extreme value approach, an asymptotically normal estimator for the location parameter μ. In this paper, we derive by the same approach, an estimator for the scale parameter σ and we discuss its limiting behavior.
相似文献
45.
J. MALINEN O. NEVANLINNA V. TURUNEN Z. YUAN 《数学学报(英文版)》2007,23(4):745-748
Let T be a bounded linear operator in a Banach space, with σ(T)={1}. In 1983, Esterle-Berkani' s conjecture was proposed for the decay of differences (I - T) T^n as follows: Eitheror lim inf (n→∞(n+1)||(I-T)T^n||≥1/e or T = I. We prove this claim and discuss some of its consequences. 相似文献
46.
可允许集上的广义向量拟均衡问题 总被引:2,自引:0,他引:2
主要讨论可允许集上的广义向量拟均衡问题,推广L in的一些结果. 相似文献
47.
牛顿弦截法预估校正迭代格式的收敛阶 总被引:2,自引:0,他引:2
研究如下形式的牛顿弦截法的预估校正(P.C.)格式:P(预估):~xk+1=xk-(xk-xk-1)f(xk)f(xk)-f(xk-1)C(校正):xk+1=xk-(~xk+1-xk)f(xk)f~(xk+1)-f(xk)证明了它的收敛阶为2.618. 相似文献
48.
Stanislav Volkov 《Journal of Theoretical Probability》2006,19(3):691-700
Vertex-reinforced random walk is a random process which visits a site with probability proportional to the weight w
k
of the number k of previous visits. We show that if w
k
∼ k
α, then there is a large time T
0 such that after T
0 the walk visits 2, 5, or ∞ sites when α < 1, = 1, or > 1, respectively. More general results are also proven.
相似文献
49.
N. Ponpandian A. Narayanasamy D. Prabhu K. Ganesan M. Manivel Raja K. Chattopadhyay 《Journal of magnetism and magnetic materials》2006
The Fe73.5Cu1Nb3Si13.5B9 FINEMET alloy has been prepared by the rapid solidification technique. The critical behaviour of this alloy in the amorphous as well as in its nanocrystalline states has been studied near their respective Curie temperatures. From the values of the critical exponents one can conclude that the alloy behaves like a 3D Heisenberg ferromagnet in the amorphous and nanocrystalline states. But there exists a slight increase in the value of β for the alloy annealed at 823 K (the nanocrystalline state) as observed in most of the amorphous alloys. 相似文献
50.
The phase boundary theory and the contact rule of phase regions are compared, and some weaknesses of the latter are manifested.
The comparison between the Gupta’s method and the boundary theory method for constructing multicomponent isobaric sections
is also presented. 相似文献