全文获取类型
收费全文 | 17268篇 |
免费 | 2045篇 |
国内免费 | 1112篇 |
专业分类
化学 | 2086篇 |
晶体学 | 79篇 |
力学 | 845篇 |
综合类 | 144篇 |
数学 | 4303篇 |
物理学 | 3933篇 |
综合类 | 9035篇 |
出版年
2024年 | 42篇 |
2023年 | 158篇 |
2022年 | 278篇 |
2021年 | 389篇 |
2020年 | 410篇 |
2019年 | 442篇 |
2018年 | 404篇 |
2017年 | 542篇 |
2016年 | 580篇 |
2015年 | 577篇 |
2014年 | 839篇 |
2013年 | 1131篇 |
2012年 | 1010篇 |
2011年 | 1045篇 |
2010年 | 867篇 |
2009年 | 971篇 |
2008年 | 1020篇 |
2007年 | 1073篇 |
2006年 | 990篇 |
2005年 | 869篇 |
2004年 | 774篇 |
2003年 | 785篇 |
2002年 | 712篇 |
2001年 | 650篇 |
2000年 | 573篇 |
1999年 | 521篇 |
1998年 | 387篇 |
1997年 | 408篇 |
1996年 | 291篇 |
1995年 | 264篇 |
1994年 | 213篇 |
1993年 | 166篇 |
1992年 | 159篇 |
1991年 | 154篇 |
1990年 | 124篇 |
1989年 | 126篇 |
1988年 | 96篇 |
1987年 | 84篇 |
1986年 | 54篇 |
1985年 | 55篇 |
1984年 | 31篇 |
1983年 | 18篇 |
1982年 | 27篇 |
1981年 | 24篇 |
1980年 | 9篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
用气相色谱的分析方法研究了理想非线性单组分不同温度下的流出曲线,用"特征点"法回归出了各组分的物理常数G和b,代入理论模型公式,并与实验结果进行子比较。 相似文献
63.
本文以一座大型厂矿文化宫建筑设计实例,扼要论述了多功能厅堂的设计要点,结合我国目前多功能厅堂使用状况,提出以电声为主的设计原则和实施办法,以改善多功能厅堂的音质效果。 相似文献
64.
本文把Weiss等发展的计算平均第一通过时间(简称MFPT)的新方法推广到由非马尔科夫多值噪声驱动的过程.为了简化,本文只限于研究矩形分布这一情形.通过一个重要实例,对MFPT进行了具体计算,并得到了显式解析表示. 相似文献
65.
研制出了用于计算氚投料量在FEB聚变堆各个子系统中的分布及其随时间变化的数值模拟程序包SWITRIM。通过近5年的使用,表明其运行良好、计算结果可靠。用SWITRIM数值模拟研究了聚变堆起动过程中的“氚坑深度和氚坑时间”新现象。简单介绍了SWITRIM程序包的组成和用户使用说明以及最新的运用等。 相似文献
66.
Europium (Eu+) ions were confined in a Paul trap and detected by non-destructive method. Storage time of Eu+ ions achieved in vacuum was improved by orders of magnitude employing buffer gas cooling. The experimentally detected signal
was fitted to the ion response signal and the total number of ions trapped was estimated. It is found that the peak signal
amplitude as well as the product of FWHM and the peak signal amplitude is proportional to the total number of trapped ions.
The trapped ion secular frequency was swept at different rates and its effect on the absorption line profile was studied both
experimentally and theoretically. 相似文献
67.
Daria E. Lonsdale Geoffrey Johnston‐Hall Amanda Fawcett Craig A. Bell Carl N. Urbani Michael R. Whittaker Michael J. Monteiro 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3620-3625
In this work, we propose that retardation in vinyl acetate polymerization rate in the presence of toluene is due to degradative chain transfer. The transfer constant to toluene (Ctrs) determined using the Mayo method is equal to 3.8 × 10?3, which is remarkably similar to the value calculated from the rate data, assuming degradative chain transfer (2.7 × 10?3). Simulations, including chain‐length‐dependent termination, were carried out to compare our degradative chain transfer model with experimental results. The conversion–time profiles showed excellent agreement between experiment and simulation. Good agreement was found for the Mn data as a function of conversion. The experimental and simulation data strongly support the postulate that degradative chain transfer is the dominant kinetic mechanism. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3620–3625, 2007 相似文献
68.
Robert J. Rubin 《Journal of statistical physics》1991,65(5-6):1207-1216
A one-dimensional lattice random walk in the presence ofm equally spaced traps is considered. The step length distribution is a symmetric exponential. An explicit analytic expression is obtained for the probability that the random walk will be trapped at thejth trapping site. 相似文献
69.
We consider queuing systems where customers are not allowed to queue, instead of that they make repeated attempts, or retrials, in order to enter service after some time. We obtain the distribution of the number of retrials produced by a tagged customer, until he finds an available server. 相似文献
70.
Many recent algorithmic approaches involve the construction of a differential equation model for computational purposes, typically
by introducing an artificial time variable. The actual computational model involves a discretization of the now time-dependent differential system, usually
employing forward Euler. The resulting dynamics of such an algorithm is then a discrete dynamics, and it is expected to be
“close enough” to the dynamics of the continuous system (which is typically easier to analyze) provided that small – hence
many – time steps, or iterations, are taken. Indeed, recent papers in inverse problems and image processing routinely report
results requiring thousands of iterations to converge. This makes one wonder if and how the computational modeling process
can be improved to better reflect the actual properties sought.
In this article we elaborate on several problem instances that illustrate the above observations. Algorithms may often lend
themselves to a dual interpretation, in terms of a simply discretized differential equation with artificial time and in terms
of a simple optimization algorithm; such a dual interpretation can be advantageous. We show how a broader computational modeling
approach may possibly lead to algorithms with improved efficiency.
AMS subject classification (2000) 65L05, 65M32, 65N21, 65N22, 65D18 相似文献