全文获取类型
收费全文 | 3392篇 |
免费 | 623篇 |
国内免费 | 124篇 |
专业分类
化学 | 300篇 |
晶体学 | 30篇 |
力学 | 202篇 |
综合类 | 74篇 |
数学 | 693篇 |
物理学 | 2840篇 |
出版年
2024年 | 2篇 |
2023年 | 23篇 |
2022年 | 69篇 |
2021年 | 97篇 |
2020年 | 85篇 |
2019年 | 70篇 |
2018年 | 69篇 |
2017年 | 145篇 |
2016年 | 179篇 |
2015年 | 126篇 |
2014年 | 397篇 |
2013年 | 268篇 |
2012年 | 197篇 |
2011年 | 241篇 |
2010年 | 203篇 |
2009年 | 230篇 |
2008年 | 222篇 |
2007年 | 252篇 |
2006年 | 198篇 |
2005年 | 170篇 |
2004年 | 129篇 |
2003年 | 111篇 |
2002年 | 90篇 |
2001年 | 79篇 |
2000年 | 61篇 |
1999年 | 68篇 |
1998年 | 61篇 |
1997年 | 45篇 |
1996年 | 40篇 |
1995年 | 41篇 |
1994年 | 23篇 |
1993年 | 24篇 |
1992年 | 21篇 |
1991年 | 16篇 |
1990年 | 17篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有4139条查询结果,搜索用时 15 毫秒
1.
Eva Lesanska 《Applications of Mathematics》2002,47(5):411-426
The problem is to determine nonsensitiveness regions for threshold ellipsoids within a regular mixed linear model. 相似文献
2.
David B. Wilson 《Random Structures and Algorithms》2002,21(2):182-195
There has been much recent interest in the satisfiability of random Boolean formulas. A random k‐SAT formula is the conjunction of m random clauses, each of which is the disjunction of k literals (a variable or its negation). It is known that when the number of variables n is large, there is a sharp transition from satisfiability to unsatisfiability; in the case of 2‐SAT this happens when m/n → 1, for 3‐SAT the critical ratio is thought to be m/n ≈ 4.2. The sharpness of this transition is characterized by a critical exponent, sometimes called ν = νk (the smaller the value of ν the sharper the transition). Experiments have suggested that ν3 = 1.5 ± 0.1. ν4 = 1.25 ± 0.05, ν5 = 1.1 ± 0.05, ν6 = 1.05 ± 0.05, and heuristics have suggested that νk → 1 as k → ∞. We give here a simple proof that each of these exponents is at least 2 (provided the exponent is well defined). This result holds for each of the three standard ensembles of random k‐SAT formulas: m clauses selected uniformly at random without replacement, m clauses selected uniformly at random with replacement, and each clause selected with probability p independent of the other clauses. We also obtain similar results for q‐colorability and the appearance of a q‐core in a random graph. © 2002 Wiley Periodicals, Inc. Random Struct. Alg., 21: 182–195, 2002 相似文献
3.
本文提出从高分辨电子显微像中,利用光学、全息和部分相干等方法,提取传递函数,制作相位和振幅滤波器,实现解卷,提高高分辨电子显微像的分辨率. 相似文献
4.
5.
在均匀颜色空间的颜色差别计箅中,亮度和色彩的作用是相关且不同的,尤其是在目标尺度对人眼张角(亦称视角)小于30角度分的条件下观察,由于亮度差和色彩差受视角变化的影响程度不同步,使得人眼颜色差别分辨阈亦不确定。本文通过一定的试验和计算,探讨了在不同的亮度差和色彩差的情况下,颜色差别阈受视角影响的变化规律。 相似文献
6.
The major goal of this paper is to examine the hypothesis that stock returns and return volatility are asymmetric, threshold nonlinear, functions of change in trading volume. A minor goal is to examine whether return spillover effects also display such asymmetry. Employing a double-threshold GARCH model with trading volume as a threshold variable, we find strong evidence supporting this hypothesis in five international market return series. Asymmetric causality tests lend further support to our trading volume threshold model and conclusions. Specifically, an increase in volume is positively associated, while decreasing volume is negatively associated, with the major price index in four of the five markets. The volatility of each series also displays an asymmetric reaction, four of the markets display higher volatility following increases in trading volume. Using posterior odds ratio, the proposed threshold model is strongly favored in three of the five markets, compared to a US news double threshold GARCH model and a symmetric GARCH model. We also find significant nonlinear asymmetric return spillover effects from the US market. 相似文献
7.
8.
9.
10.
A set of vertices is shattered in a hypergraph if any of its subsets is obtained as the intersection of an edge with the set. The VC dimension is the size of the largest shattered subset. Under the binomial model of k‐uniform random hypergraphs, the threshold function for the VC dimension to be larger than a given integer is obtained. The same is done for the testing dimension, which is the largest integer d such that all sets of cardinality d are shattered. © 2006 Wiley Periodicals, Inc. Random Struct. Alg., 2007 相似文献