全文获取类型
收费全文 | 35068篇 |
免费 | 3713篇 |
国内免费 | 3413篇 |
专业分类
化学 | 18913篇 |
晶体学 | 593篇 |
力学 | 2409篇 |
综合类 | 333篇 |
数学 | 6654篇 |
物理学 | 13292篇 |
出版年
2023年 | 242篇 |
2022年 | 687篇 |
2021年 | 775篇 |
2020年 | 789篇 |
2019年 | 747篇 |
2018年 | 753篇 |
2017年 | 936篇 |
2016年 | 1068篇 |
2015年 | 963篇 |
2014年 | 1250篇 |
2013年 | 2282篇 |
2012年 | 1815篇 |
2011年 | 1869篇 |
2010年 | 1687篇 |
2009年 | 2434篇 |
2008年 | 2457篇 |
2007年 | 2481篇 |
2006年 | 2349篇 |
2005年 | 1682篇 |
2004年 | 1539篇 |
2003年 | 1391篇 |
2002年 | 1352篇 |
2001年 | 1132篇 |
2000年 | 1079篇 |
1999年 | 1005篇 |
1998年 | 925篇 |
1997年 | 775篇 |
1996年 | 603篇 |
1995年 | 557篇 |
1994年 | 491篇 |
1993年 | 395篇 |
1992年 | 483篇 |
1991年 | 340篇 |
1990年 | 291篇 |
1989年 | 222篇 |
1988年 | 229篇 |
1987年 | 187篇 |
1986年 | 139篇 |
1985年 | 137篇 |
1984年 | 145篇 |
1983年 | 85篇 |
1982年 | 145篇 |
1981年 | 199篇 |
1980年 | 206篇 |
1979年 | 201篇 |
1978年 | 182篇 |
1977年 | 116篇 |
1976年 | 121篇 |
1974年 | 42篇 |
1973年 | 85篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
81.
Alessandro Conflitti 《Finite Fields and Their Applications》2003,9(4):423-431
We propose a probabilistic algorithm to reduce computing the greatest common divisor of m polynomials over a finite field (which requires computing m−1 pairwise greatest common divisors) to computing the greatest common divisor of two polynomials over the same field. 相似文献
82.
V. Balek T. Mitsuhashi I.M. Bountseva H. Haneda Z. Malek J. Šubrt 《Journal of Sol-Gel Science and Technology》2003,26(1-3):185-189
The diffusion structural analysis (DSA) was used to characterize microstructure changes of hydrous titania gel films under in situ conditions of heating. TG and DTA were used in order to elucidate the processes controlling the formation of anatase film during heating of hydrous titania gel film. The annealing of porosity and near surface structure defects of the dehydrated titania films was indicated by DSA in the temperature range 255–700°C as the decrease of radon release rate. It was demonstrated that the annealing was enhanced on heating in oxygen in comparison with heating in argon. The DSA experimental results were compared with model curves describing the radon diffusion mobility and the annealing of radon diffusion paths. 相似文献
83.
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
84.
A locally convex space is said to be a Gateaux differentiability space (GDS)provided every continuous convex function defined on a nonempty convex open subset D of the space is densely Gateaux differentiable in D.This paper shows that the product of a GDS and a family of separable Frechet spaces is a GDS,and that the product of a GDS and an arbitrary locally convex space endowed with the weak topology is a GDS. 相似文献
85.
Burn‐in is a widely used method to improve the quality of products or systems after they have been produced. In this paper, we consider the problem of determining the optimal burn‐in time and optimal work size maximizing the long‐run average amount of work saved per time unit in the computer applications. Assuming that the underlying lifetime distribution of the computer has an initially decreasing or/and eventually increasing failure rate function, an upper bound for the optimal burn‐in time is derived for each fixed work size and a uniform (with respect to the burn‐in time) upper bound for the optimal work size is also obtained. Furthermore, it is shown that a non‐trivial lower bound for the optimal burn‐in time can be derived if the underlying lifetime distribution has a large initial failure rate. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
86.
The measuring elements of both dry‐ and wet‐type gas meters are composed of a diaphragm and rotary drum. In this article an explanation on the principle of measuring and the structure of the gas meter for each of these two types was discussed. Such applications were made as follows: synthetic rubber was used for the measuring diaphragm, engineering plastic was employed instead of metal for the measuring drum, and poly(butylene terephthalate) (PBT) was used for the casing, respectively. As a result, an improvement in the gas resistance performance and productivity, which led to a lighter weight, more compactness and a lower cost of productions was achieved. Also the influence of the solubility of the measured gas to the plastic on the measured valve was discussed. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
87.
88.
Kurt Majewski 《Queueing Systems》2005,50(2-3):199-230
We consider multiclass feedforward queueing networks under first in first out and priority service disciplines driven by long-range dependent arrival and service time processes. We show that in critical loading the normalized workload, queue length and sojourn time processes can converge to a multi-dimensional reflected fractional Brownian motion. This weak heavy traffic approximation is deduced from a deterministic pathwise approximation of the network behavior close to constant critical load in terms of the solution of a Skorokhod problem. Since we model the doubly infinite time interval, our results directly cover the stationary case.AMS subject classification: primary 90B15, secondary 60K25, 68M20 相似文献
89.
有限循环群的Fuzzy子群的等价类数 总被引:4,自引:2,他引:2
有限循环群G的F子群可以有无数个.但是.若当两个F子群的水平集构成的集合相等就称其等价的话,那么其等价类数是有限的。通过研究群的合成群列、商群列以及数的因数列和极大因数列找出了有限循环群的极大F子群和F子群的等价类数的求解公式.并给出二者之间的关系式. 相似文献
90.
Christopher J. Nichols 《Tetrahedron letters》2004,45(40):7469-7473
A number of new functionalised bridged indolocarbazole systems have been prepared by ring-opening reactions of a key cyclic sulfate intermediate, prepared from the corresponding diol by the action of sulfuryl diimidazole and DBU. The same cyclic sulfate also undergoes an unprecedented asymmetric rearrangement to a chiral ketone, on treatment with a chiral lithium amide base. 相似文献