全文获取类型
收费全文 | 27876篇 |
免费 | 4588篇 |
国内免费 | 2878篇 |
专业分类
化学 | 18442篇 |
晶体学 | 268篇 |
力学 | 1934篇 |
综合类 | 217篇 |
数学 | 3427篇 |
物理学 | 11054篇 |
出版年
2024年 | 106篇 |
2023年 | 593篇 |
2022年 | 1072篇 |
2021年 | 1106篇 |
2020年 | 1106篇 |
2019年 | 1045篇 |
2018年 | 975篇 |
2017年 | 926篇 |
2016年 | 1354篇 |
2015年 | 1309篇 |
2014年 | 1542篇 |
2013年 | 2064篇 |
2012年 | 2433篇 |
2011年 | 2450篇 |
2010年 | 1640篇 |
2009年 | 1601篇 |
2008年 | 1743篇 |
2007年 | 1498篇 |
2006年 | 1374篇 |
2005年 | 1162篇 |
2004年 | 865篇 |
2003年 | 694篇 |
2002年 | 623篇 |
2001年 | 526篇 |
2000年 | 523篇 |
1999年 | 631篇 |
1998年 | 530篇 |
1997年 | 526篇 |
1996年 | 490篇 |
1995年 | 466篇 |
1994年 | 388篇 |
1993年 | 349篇 |
1992年 | 287篇 |
1991年 | 251篇 |
1990年 | 238篇 |
1989年 | 186篇 |
1988年 | 145篇 |
1987年 | 125篇 |
1986年 | 93篇 |
1985年 | 94篇 |
1984年 | 63篇 |
1983年 | 50篇 |
1982年 | 52篇 |
1981年 | 22篇 |
1980年 | 12篇 |
1979年 | 4篇 |
1976年 | 1篇 |
1959年 | 1篇 |
1957年 | 7篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
We study the large-sample properties of a class of parametric mixture models with covariates for competing risks. The models allow general distributions for the survival times and incorporate the idea of long-term survivors. Asymptotic results are obtained under a commonly assumed independent censoring mechanism and some modest regularity conditions on the survival distributions. The existence, consistency, and asymptotic normality of maximum likelihood estimators for the parameters of the model are rigorously derived under general sufficient conditions. Specific conditions for particular models can be derived from the general conditions for ready check. In addition, a likelihood-ratio statistic is proposed to test various hypotheses of practical interest, and its asymptotic distribution is provided. 相似文献
62.
63.
本利用矩阵给出了几类数列的通项公式的求法,把数列通项公式的求法转化为矩阵幂的计算,思路简单、计算简便,并能判别其敛散性。 相似文献
64.
THE ASYMPTOTIC SOLUTION FOR A CLASS OF SINGULARLY PERTURBED PROBLEM FOR SEMILINEAR SINGULAR EQUATION
The singularly perturbed boundary value problem for a class of semilinearsingular equation is considered. Using a simple and special method the asym-ptotic behavior of solution is studied. 相似文献
65.
66.
We present a review of our recent measurements of total cross sections (Q
T's) for the scattering of positrons by Na, K, and Rb, and positronium-formation cross sections (Q
Ps's) for Na and K. For our total cross section measurements, a beam transmission technique has been used. For ourQ
Ps measurements, our approach involves setting upper and lower limits onQ
Ps using a combination of (1) measuring the transmission of the positron beam with the angular discrimination of the apparatus made as poor as possible, and (2) measuring the 511 keV annihilation gamma rays in coincidence produced by the decay of para-Ps formed in the scattering cell. Comparison with theoretical calculations shows that our measuredQ
T's andQ
Ps's for Na and K agree reasonably well with a close coupling approximation (CCA) calculation which takes into account the formation of Ps in then=1 andn=2 states. In the 3–10 eV energy range, this calculation predicts a peak in theQ
T's andQ
Ps's for K which also appears in our measurements. The absence of such a peak in our measuredQ
T's andQ
Ps's (preliminary) for Na in this energy range is also consistent with the same theory. Comparisons with five-state CCA calculations ofQ
T which do not take Ps-formation into account also show good agreement with our positron-Na, K, and RbQ
T measurements for energies above 20 eV, but show dramatic departures from our measurements below 10 eV for K and Rb. 相似文献
67.
旋转带电体磁矩计算的若干法则与算例 总被引:2,自引:0,他引:2
本文在文献 [1]、[2 ]等的基础上给出关于旋转带电体的磁矩计算的若干法则 ,均以定理形式表达 ,并列表枚举其相关算例 相似文献
68.
In the present paper, we prove that the Bernstein-Kantorovič operators have the ability of preserving translation property
in both C and Lp norms.
Supported (in part) by the NSFC(10471130,10371024) of PRC and the Natural Science Foundation (Y604003) of Zhejiang Province. 相似文献
69.
Chongyi Wan Shiming Liu Rongqing Tan Jin Wu Jinwen Zhou Yan Lv Yanning Yu Hua Yang 《Optics & Laser Technology》2004,36(8):2389-649
A high average power, high-repetition-rate TEA CO2 laser employing printed-circuit-board preionizer is described. The power scaling of this preionization configuration has been demonstrated. The average output power reaches 3.6 kW at pulse repetition rate of 180 pps. Furthermore, the scaling-up ability of the rotating spark gap as high-voltage switch for high-average-power gas laser has been validated. 相似文献
70.
Felipe Cucker Steve Smale Ding-Xuan Zhou 《Foundations of Computational Mathematics》2004,4(3):315-343
We describe a model for the evolution of the languages used by the agents of a
society. Our main result proves convergence of these languages to a common
one under certain conditions. A few special cases are elaborated in more
depth. 相似文献