全文获取类型
收费全文 | 17804篇 |
免费 | 1767篇 |
国内免费 | 738篇 |
专业分类
化学 | 1721篇 |
晶体学 | 77篇 |
力学 | 882篇 |
综合类 | 174篇 |
数学 | 7124篇 |
物理学 | 3479篇 |
无线电 | 6852篇 |
出版年
2024年 | 36篇 |
2023年 | 158篇 |
2022年 | 267篇 |
2021年 | 318篇 |
2020年 | 335篇 |
2019年 | 315篇 |
2018年 | 300篇 |
2017年 | 482篇 |
2016年 | 487篇 |
2015年 | 499篇 |
2014年 | 840篇 |
2013年 | 1249篇 |
2012年 | 893篇 |
2011年 | 1048篇 |
2010年 | 918篇 |
2009年 | 1411篇 |
2008年 | 1553篇 |
2007年 | 1398篇 |
2006年 | 1190篇 |
2005年 | 905篇 |
2004年 | 712篇 |
2003年 | 680篇 |
2002年 | 612篇 |
2001年 | 539篇 |
2000年 | 419篇 |
1999年 | 406篇 |
1998年 | 393篇 |
1997年 | 287篇 |
1996年 | 236篇 |
1995年 | 191篇 |
1994年 | 184篇 |
1993年 | 128篇 |
1992年 | 104篇 |
1991年 | 90篇 |
1990年 | 83篇 |
1989年 | 59篇 |
1988年 | 55篇 |
1987年 | 54篇 |
1986年 | 42篇 |
1985年 | 78篇 |
1984年 | 55篇 |
1983年 | 34篇 |
1982年 | 51篇 |
1981年 | 41篇 |
1980年 | 32篇 |
1979年 | 41篇 |
1978年 | 25篇 |
1977年 | 18篇 |
1976年 | 20篇 |
1974年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
51.
基于相对论平均场理论,研究了各种相互作用参数组(NL1、NL3、NLSH、TM1和GL-97)对中子星物质的性质和中子星整体结构的影响.发现参数组NL1、NL3和NLSH所给出的中子星内部的介子场强度、物质的组成比例、物态方程和中子星的整体特点基本相同,但与TM1和GL-97之间有较大的差别.相对于其他参数组,GL-97给出的介子场强度最弱,中子星的相对数密度最大,物态方程也最软,同时采用GL-97参数组计算的中子星的最大质量也最小. 相似文献
52.
Dominique Fourdrinier William E. Strawderman 《Annals of the Institute of Statistical Mathematics》2003,55(4):803-816
We consider estimation of loss for generalized Bayes or pseudo-Bayes estimators of a multivariate normal mean vector, θ. In
3 and higher dimensions, the MLEX is UMVUE and minimax but is inadmissible. It is dominated by the James-Stein estimator and by many others. Johnstone (1988,
On inadmissibility of some unbiased estimates of loss,Statistical Decision Theory and Related Topics, IV (eds. S. S. Gupta and J. O. Berger), Vol. 1, 361–379, Springer, New York) considered the estimation of loss for the usual
estimatorX and the James-Stein estimator. He found improvements over the Stein unbiased estimator of risk. In this paper, for a generalized
Bayes point estimator of θ, we compare generalized Bayes estimators to unbiased estimators of loss. We find, somewhat surprisingly,
that the unbiased estimator often dominates the corresponding generalized Bayes estimator of loss for priors which give minimax
estimators in the original point estimation problem. In particular, we give a class of priors for which the generalized Bayes
estimator of θ is admissible and minimax but for which the unbiased estimator of loss dominates the generalized Bayes estimator
of loss. We also give a general inadmissibility result for a generalized Bayes estimator of loss.
Research supported by NSF Grant DMS-97-04524. 相似文献
53.
C. H. Hesse 《Statistical Inference for Stochastic Processes》2007,10(1):75-95
In this work the Cauchy problem for the one-dimensional heat equation is considered. In contrast to existing literature it
is assumed that the initial state f is unknown and that information regarding f is obtained by some process of measurement. To enhance realism, both measurement errors and missing data are allowed for.
Under assumptions on f in the Fourier-domain first an approximation to f is derived from the data by means of a novel uncertainty principle. Then, it is studied how this perturbation in the initial
state propagates with time.
相似文献
54.
A time discrete scheme is used to approximate the solution toa phase field system of PenroseFife type with a non-conservedorder parameter. An a posteriori error estimate is presentedthat allows the estimation of the difference between continuousand semidiscrete solutions by quantities that can be calculatedfrom the approximation and given data. 相似文献
55.
Lihong Wang 《Annals of the Institute of Statistical Mathematics》2004,56(2):251-264
The purpose of this paper is to investigate the asymptotic properties of the least squares estimates (L
2-estimates) and the least absolute deviation estimates (L
1-estimates) of the parameters of a nonlinear regression model subject to a set of equality and inequality restrictions, which
has a long-range dependent stationary process as its stochastic errors. Then we will compare the asymptotic relative efficiencies
of the above estimators. 相似文献
56.
Sebastián López Gustavo M. Callicó Félix Tobajas Valentín de Armas José F. López Roberto Sarmiento 《ETRI Journal》2008,30(6):862-864
This letter presents a novel approach for organizing computational resources into groups within H.264/AVC motion estimation architectures, leading to reductions of up to 75% in the equivalent gate count with respect to state‐of‐the‐art designs. 相似文献
57.
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
58.
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
59.
光纤荧光传感器衰减寿命的加权对数拟合法 总被引:2,自引:0,他引:2
荧光寿命的检测是荧光光学传感器的核心内容,国际上尝试了多种方法来拟合这种理论上为单指数衰减信号的荧光衰减曲线。这些方法包括非线性函数标准拟合方法。即Levenburg-Marquardt方法,以及Prony方法、FFT方法,对数拟合法等等。为了克服在实际应用中发生的信号退化,需要在测量信号衰减寿命的同时测量信号的初始强度。文章介绍了一种加权的对数拟合法,经计算机仿真及实际数据测试均可以得到和Levenburg-Marquardt方法非常接近的结果,且拟合时间大大缩短,测量稳定性大大提高。仿真测试及具体实验测试结果显示了这种方法的有效性。该方法不仅与Levenburg-Marquardt方法的偏差曲线非常相似,而且实验测得的荧光寿命与Levenburg-Marquardt方法偏差在0.2%以内。 相似文献
60.