全文获取类型
收费全文 | 21126篇 |
免费 | 1666篇 |
国内免费 | 1178篇 |
专业分类
化学 | 755篇 |
晶体学 | 77篇 |
力学 | 2743篇 |
综合类 | 195篇 |
数学 | 3889篇 |
物理学 | 3307篇 |
综合类 | 13004篇 |
出版年
2024年 | 97篇 |
2023年 | 254篇 |
2022年 | 371篇 |
2021年 | 467篇 |
2020年 | 479篇 |
2019年 | 391篇 |
2018年 | 420篇 |
2017年 | 525篇 |
2016年 | 560篇 |
2015年 | 641篇 |
2014年 | 956篇 |
2013年 | 1110篇 |
2012年 | 1166篇 |
2011年 | 1289篇 |
2010年 | 955篇 |
2009年 | 1200篇 |
2008年 | 1198篇 |
2007年 | 1493篇 |
2006年 | 1316篇 |
2005年 | 1204篇 |
2004年 | 1043篇 |
2003年 | 938篇 |
2002年 | 829篇 |
2001年 | 750篇 |
2000年 | 690篇 |
1999年 | 551篇 |
1998年 | 503篇 |
1997年 | 421篇 |
1996年 | 342篇 |
1995年 | 297篇 |
1994年 | 265篇 |
1993年 | 205篇 |
1992年 | 202篇 |
1991年 | 170篇 |
1990年 | 170篇 |
1989年 | 117篇 |
1988年 | 89篇 |
1987年 | 59篇 |
1986年 | 56篇 |
1985年 | 36篇 |
1984年 | 26篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1955年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
本文讨论延迟微分方程单支方法的非线性稳定性 .对于 Kα,β,γ类非线性延迟微分方程 ,我们证明带有线性插值的 G( c,p,q) -代数稳定的单支方法当 c≤ 1时是 GR( p/2 ,q/2 ) -稳定及弱 GAR( p/2 ,q/2 ) -稳定的 ,当 c<1时是 GAR( p/2 ,q/2 ) -稳定的 .最后的数值试验表明了上述结论的正确性 . 相似文献
92.
Ioannis K. Argyros 《Journal of Mathematical Analysis and Applications》2004,298(2):374-397
We provide a local as well as a semilocal convergence analysis for two-point Newton-like methods in a Banach space setting under very general Lipschitz type conditions. Our equation contains a Fréchet differentiable operator F and another operator G whose differentiability is not assumed. Using more precise majorizing sequences than before we provide sufficient convergence conditions for Newton-like methods to a locally unique solution of equation F(x)+G(x)=0. In the semilocal case we show under weaker conditions that our error estimates on the distances involved are finer and the information on the location of the solution at least as precise as in earlier results. In the local case a larger radius of convergence is obtained. Several numerical examples are provided to show that our results compare favorably with earlier ones. As a special case we show that the famous Newton-Kantorovich hypothesis is weakened under the same hypotheses as the ones contained in the Newton-Kantorovich theorem. 相似文献
93.
硅色敏器件对复色光色差辨识能力的数值分析 总被引:3,自引:2,他引:1
对复色光的光谱功率分布和色敏器件光谱响应的实验曲线进行了函数拟合,采用Mathematica 4.2计算了具有不同峰值波长和半高宽的高斯分布的复色光在色敏器件中产生的电流比.计算结果表明,待测复色光的峰值波长和半高宽变化对两种典型的色敏器件的输出信号影响的权重比分别为100:1和10:1。权重比说明色敏器件的输出电流比随峰值波长和半高宽的变化非常灵敏,但两者权重不同,其中峰值波长的变化影响更为显著,是影响复色光颜色变化的主要因素.数值分析的结果表明,硅双结色敏器件对复色光色差有良好的辨识能力.两种器件权重比的差异说明了器件制作工艺与其辨识能力的关系,为器件合理设计提供了理论依据. 相似文献
94.
Mechanics of Composite Materials - A three-dimensional ply-level modeling of multiple matrix cracking near an open hole in a quasi-isotropic composite laminate was performed. A mesh-independent... 相似文献
95.
Keith Jonathan M. Kroese Dirk P. Bryant Darryn 《Methodology and Computing in Applied Probability》2004,6(1):29-53
A recent development of the Markov chain Monte Carlo (MCMC) technique is the emergence of MCMC samplers that allow transitions between different models. Such samplers make possible a range of computational tasks involving models, including model selection, model evaluation, model averaging and hypothesis testing. An example of this type of sampler is the reversible jump MCMC sampler, which is a generalization of the Metropolis–Hastings algorithm. Here, we present a new MCMC sampler of this type. The new sampler is a generalization of the Gibbs sampler, but somewhat surprisingly, it also turns out to encompass as particular cases all of the well-known MCMC samplers, including those of Metropolis, Barker, and Hastings. Moreover, the new sampler generalizes the reversible jump MCMC. It therefore appears to be a very general framework for MCMC sampling. This paper describes the new sampler and illustrates its use in three applications in Computational Biology, specifically determination of consensus sequences, phylogenetic inference and delineation of isochores via multiple change-point analysis. 相似文献
96.
研究了Banach空间中拟-似变分包含解的存在与逼近问题.给出了一种寻求解的新的迭代算法,建立了具混合误差的Ishikawa型迭代序列强收敛到解的充要条件.所得结果推广了一些相关的结果. 相似文献
97.
This paper deals with the analysis of an M/M/c queueing system with setup times. This queueing model captures the major characteristics of phenomena occurring in production
when the system consists in a set of machines monitored by a single operator. We carry out an extensive analysis of the system
including limiting distribution of the system state, waiting time analysis, busy period and maximum queue length.
AMS subject classification: 90B22, 60K25 相似文献
98.
99.
Dot pattern is a type of pattern defined by specific spatial relationship among some dots. As a compensation for concrete and meaningful visual stimuli, meaningless dot pattern can be used as stimuli in learning tasks. We performed an experiment for exploring the perceptual learning process of dot pattern against random-dot background. Participants were required to learn two types of dot patterns (9-dot and 11-dot). They were assigned to two groups: participants in Group 1 learned 9-dot pattern first and 11-dot pattern later, while those in Group 2 learned 11-dot pattern first and 9-dot pattern later. The results showed that participants could acquire the spatial relationship of dot pattern through perceptual learning in relatively short learning time. In comparison with 9-dot pattern, learning time of 11-dot pattern was slightly longer and its accuracy rate lower, but there was significant positive transfer effect from 11-dot pattern learning to 9-dot learning. 相似文献
100.
步进电机细分技术在经济型数控机床中的应用 总被引:1,自引:0,他引:1
本文叙述了步进电机细分原理及微机控制系统,并将其应用于经济型数控铣床的横向进给伺服系统,有效提高了开环数控系统的定位精度。 相似文献