全文获取类型
收费全文 | 1335篇 |
免费 | 33篇 |
国内免费 | 36篇 |
专业分类
化学 | 104篇 |
力学 | 48篇 |
数学 | 490篇 |
物理学 | 643篇 |
无线电 | 119篇 |
出版年
2024年 | 3篇 |
2023年 | 9篇 |
2022年 | 11篇 |
2021年 | 16篇 |
2020年 | 20篇 |
2019年 | 25篇 |
2018年 | 12篇 |
2017年 | 22篇 |
2016年 | 20篇 |
2015年 | 33篇 |
2014年 | 40篇 |
2013年 | 56篇 |
2012年 | 34篇 |
2011年 | 54篇 |
2010年 | 48篇 |
2009年 | 68篇 |
2008年 | 94篇 |
2007年 | 80篇 |
2006年 | 84篇 |
2005年 | 51篇 |
2004年 | 51篇 |
2003年 | 45篇 |
2002年 | 65篇 |
2001年 | 65篇 |
2000年 | 61篇 |
1999年 | 59篇 |
1998年 | 55篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 36篇 |
1994年 | 15篇 |
1993年 | 16篇 |
1992年 | 10篇 |
1991年 | 14篇 |
1990年 | 16篇 |
1989年 | 17篇 |
1988年 | 9篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1948年 | 1篇 |
排序方式: 共有1404条查询结果,搜索用时 556 毫秒
81.
This paper considers the estimate problem on the mean matrix of mixtureof normals. In order to evaluate estimators of the mean matrix, a fundamental frameof Ф-(general) decision problem is established. Under the frame, a class of Ф-minimax estimators are constructed. 相似文献
82.
Iva Franjić 《Mathematische Nachrichten》2015,288(17-18):2016-2027
This paper aims to contribute to the exploration of quadrature formulae by proving that the error of a quadrature formula has the Schur‐convexity property. The emphasis is on the quadrature formulae with the maximum degree of precision. The Schur‐convexity of the error has an interesting implication – the monotonicity of the error. Namely, it turns out that the absolute value of the error is always smaller on a smaller interval (of the two which share the same midpoint). 相似文献
83.
Since the (original) ghost fluid method (OGFM) was proposed by Fedkiw et al. in 1999 [5], a series of other GFM-based methods such as the gas–water version GFM (GWGFM), the modified GFM (MGFM) and the real GFM (RGFM) have been developed subsequently. Systematic analysis, however, has yet to be carried out for the various GFMs on their accuracies and conservation errors. In this paper, we develop a technique to rigorously analyze the accuracies and conservation errors of these different GFMs when applied to the multi-medium Riemann problem with a general equation of state (EOS). By analyzing and comparing the interfacial state provided by each GFM to the exact one of the original multi-medium Riemann problem, we show that the accuracy of interfacial treatment can achieve “third-order accuracy” in the sense of comparing to the exact solution of the original mutli-medium Riemann problem for the MGFM and the RGFM, while it is of at most “first-order accuracy” for the OGFM and the GWGFM when the interface approach is actually near in balance. Similar conclusions are also obtained in association with the local conservation errors. A special test method is exploited to validate these theoretical conclusions from the numerical viewpoint. 相似文献
84.
网络窃密对桌面系统的威胁越来越严重,现有的各种独立的安全产品无法提供完整、有效的解决方案。本文分析了通过网络窃取桌面信息的一般流程,有针对性地提出了一种防窃密桌面防御系统。该系统从整体防御的思想出发,对个人防火墙、入侵检测和文件保护三个子系统进行了集成。可以针对入侵和窃密的各个环节实施有效的整体防御。 相似文献
85.
M. Henkel D. Karevski 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):787-792
The effect of point defects on persistent currents in mesoscopic rings is studied in a simple tight-binding model. Using an
analogy with the treatment of the critical quantum Ising chain with defects, conformal invariance techniques are employed
to relate the persistent current amplitude to the Hamiltonian spectrum just above the Fermi energy. From this, the dependence
of the current on the magnetic flux is found exactly for a ring with one or two point defects. The effect of an aperiodic
modulation of the ring, generated through a binary substitution sequence, on the persistent current is also studied. The flux-dependence
of the current is found to vary remarkably between the Fibonacci and the Thue-Morse sequences.
Received: 4 March 1998 / Revised: 20 April 1998 / Accepted: 30 April 1998 相似文献
86.
In this paper we consider a collocation method for solving Fredholm integral equations of the first kind, which is known to be an ill-posed problem. An “unregularized” use of this method can give reliable results in the case when the rate at which smallest singular values of the collocation matrices decrease is known a priori. In this case the number of collocation points plays the role of a regularization parameter. If the a priori information mentioned above is not available, then a combination of collocation with Tikhonov regularization can be the method of choice. We analyze such regularized collocation in a rather general setting, when a solution smoothness is given as a source condition with an operator monotone index function. This setting covers all types of smoothness studied so far in the theory of Tikhonov regularization. One more issue discussed in this paper is an a posteriori choice of the regularization parameter, which allows us to reach an optimal order of accuracy for deterministic noise model without any knowledge of solution smoothness. 相似文献
87.
Arpi A. Stepanyan 《Journal of Contemporary Mathematical Analysis (Armenian Academy of Sciences)》2007,42(3):151-160
The paper proves that every almost everywhere finite measurable function is representable by an absolute convergent series in the Franklin systems generated by quasi-dyadic, weakly regular partitions. 相似文献
88.
Árpád Baricz 《Journal of Mathematical Analysis and Applications》2007,327(2):1202-1213
This paper is motivated by an open problem of Anderson, Vamanamurthy, and Vuorinen. We prove a chain of inequalities for hypergeometric functions, generalized and normalized Bessel functions, Kummer functions and for some general power series. Some particular cases and refinements are given. 相似文献
89.
赵晓强 《应用数学学报(英文版)》1995,11(3):263-267
ONTHEEXISTENCEOFGLOBALGENERALSOLUTIONSOF POLYNOMIALSYSTEMSZHAOXIAOQIANG(赵晓强)(InstituteofAppliedMathematics,theChineseAcademyo... 相似文献
90.
Chun-Li Chen Sen-Yue Lou Yi-Shen li 《Communications in Nonlinear Science & Numerical Simulation》2004,9(6):583-601
The possible solitary wave solutions for a general Boussinesq (GBQ) type fluid model are studied analytically. After proving the non-Painlevé integrability of the model, the first type of exact explicit travelling solitary wave with a special velocity selection is found by the truncated Painlevé expansion. The general solitary waves with different travelling velocities can be studied by casting the problems to the Newtonian quasi-particles moving in some proper one dimensional potential fields. For some special velocity selections, the solitary waves possess different shapes, say, the left moving solitary waves may possess different shapes and/or amplitudes with those of the right moving solitons. For some other velocities, the solitary waves are completely prohibited. There are three types of GBQ systems (GBQSs) according to the different selections of the model parameters. For the first type of GBQS, both the faster moving and lower moving solitary waves allowed but the solitary waves with“middle” velocities are prohibit. For the second type of GBQS all the slower moving solitary waves are completely prohibit while for the third type of GBQS only the slower moving solitary waves are allowed. Only the solitary waves with the almost unit velocities meet the weak non-linearity conditions. 相似文献