全文获取类型
收费全文 | 13637篇 |
免费 | 767篇 |
国内免费 | 1313篇 |
专业分类
化学 | 1284篇 |
晶体学 | 1篇 |
力学 | 443篇 |
综合类 | 123篇 |
数学 | 8001篇 |
物理学 | 1265篇 |
综合类 | 4600篇 |
出版年
2024年 | 16篇 |
2023年 | 167篇 |
2022年 | 204篇 |
2021年 | 202篇 |
2020年 | 289篇 |
2019年 | 341篇 |
2018年 | 312篇 |
2017年 | 368篇 |
2016年 | 316篇 |
2015年 | 332篇 |
2014年 | 656篇 |
2013年 | 925篇 |
2012年 | 651篇 |
2011年 | 798篇 |
2010年 | 661篇 |
2009年 | 824篇 |
2008年 | 871篇 |
2007年 | 934篇 |
2006年 | 788篇 |
2005年 | 769篇 |
2004年 | 620篇 |
2003年 | 593篇 |
2002年 | 508篇 |
2001年 | 439篇 |
2000年 | 386篇 |
1999年 | 381篇 |
1998年 | 346篇 |
1997年 | 330篇 |
1996年 | 236篇 |
1995年 | 200篇 |
1994年 | 175篇 |
1993年 | 149篇 |
1992年 | 124篇 |
1991年 | 148篇 |
1990年 | 119篇 |
1989年 | 89篇 |
1988年 | 83篇 |
1987年 | 49篇 |
1986年 | 38篇 |
1985年 | 43篇 |
1984年 | 30篇 |
1983年 | 21篇 |
1982年 | 26篇 |
1981年 | 32篇 |
1980年 | 20篇 |
1979年 | 27篇 |
1978年 | 25篇 |
1977年 | 17篇 |
1976年 | 16篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
We consider some Sobolev-type spaces and obtain a necessary and sufficient condition for their embedding in a Lebesgue space. 相似文献
22.
We extend the matrix version of Cochran's statistical theorem to outer inverses of a matrix. As applications, we investigate the Wishartness and independence of matrix quadratic forms for Kronecker product covariance structures. 相似文献
23.
Suppose μ is a Radon measure on ℝ
d
, which may be non doubling. The only condition assumed on μ is a growth condition, namely, there is a constant C0>0 such that for all x∈supp(μ) and r>0, μ(B(x, r))⪯C0rn, where 0<n⪯d. We prove T1 theorem for non doubling measures with weak kernel conditions. Our approach yields new results
for kernels satisfying weakened regularity conditions, while recovering previously known Tolsa’s results. We also prove T1
theorem for Besov spaces on nonhomogeneous spaces with weak kernel conditions given in [7]. 相似文献
24.
Jeannette H. C. Woerner 《商业与工业应用随机模型》2005,21(1):27-44
In the framework of stochastic volatility models we examine estimators for the integrated volatility based on the pth power variation (i.e. the sum of pth absolute powers of the log‐returns). We derive consistency and distributional results for the estimators given high‐frequency data, especially taking into account what kind of process we may add to our model without affecting the estimate of the integrated volatility. This may on the one hand be interpreted as a possible flexibility in modelling, for example adding jumps or even leaving the framework of semimartingales by adding a fractional Brownian motion, or on the other hand as robustness against model misspecification. We will discuss possible choices of p under different model assumptions and irregularly spaced data. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
25.
给出了多种交叉方式遗传算法的模式定理及相关的证明.该定理避免了遗传算法模式理论的不足,使模式理论更加准确、严格. 相似文献
26.
27.
28.
For an arbitrary bounded closed set E in the complex plane with complement Ω of finite connectivity, we study the degree of convergence of the lemniscates in Ω. 相似文献
29.
林正炎 《数学物理学报(B辑英文版)》2003,23(3)
Let {X_n, n≥1} be a strictly stationary sequence of random variables, whichare either associated or negatively associated, f(·) be their common density. In this paper,the author shows a central limit theorem for a kernel estimate of f(·) under certain regularconditions. 相似文献
30.
Sulfate-reducing bacteria (SRB) were isolated from anaerobic sludge of yeast factory wastewater treatment plant by cultivation on Postgate C medium. Microcalorimetry was used to monitor the anaerobic digestion processes and to measure the growth rates of sulfate-reducing bacteria. The maximum growth rates determined by microcalorimetry and ATP analysis were different—μmax(dQ/dt) = 0.165 ± 0.008 h−1 and μmax(NATP) = 0.207 ± 0.013 h−1. Experiments on the cultivation of SRB from yeast industry wastewater treatment plant in batch culture showed that during the first 20 h the concentration of sulfate decreased from 78.3 mM down to 62.2 mM while the increase of sulfide production was negligible. Perceptible amount of sulfide (7.82 mM) appeared on the 33.5 h of fermentation together with a peak on the power–time curve and considerable increase in the cell count (1.26 × 109). First steps of sulfate metabolism (activation of sulfate by ATP sulfurylase, production of H2) are accompanied by endothermic heat effects, therefore the values of thermal power remain moderate until the evolution of sulfide starts. The influence of green microalgae Chlorococcum sp. (preparation Biotreat 100) on the growth characteristics of microorganisms was also studied. Identification of one SRB strain was started by sequencing of PCR-amplified 16S rRNA gene. Two sets of primers were used for PCR amplification, both specific for domain Bacteria but giving different gene fragments. PCR-products were purified with JETQUICK kit according to the manufacturer instructions. 相似文献