全文获取类型
收费全文 | 6204篇 |
免费 | 1829篇 |
国内免费 | 460篇 |
专业分类
化学 | 931篇 |
晶体学 | 45篇 |
力学 | 456篇 |
综合类 | 167篇 |
数学 | 2016篇 |
物理学 | 4878篇 |
出版年
2024年 | 14篇 |
2023年 | 44篇 |
2022年 | 180篇 |
2021年 | 229篇 |
2020年 | 214篇 |
2019年 | 204篇 |
2018年 | 200篇 |
2017年 | 255篇 |
2016年 | 296篇 |
2015年 | 271篇 |
2014年 | 440篇 |
2013年 | 526篇 |
2012年 | 403篇 |
2011年 | 509篇 |
2010年 | 404篇 |
2009年 | 383篇 |
2008年 | 375篇 |
2007年 | 512篇 |
2006年 | 421篇 |
2005年 | 344篇 |
2004年 | 275篇 |
2003年 | 280篇 |
2002年 | 243篇 |
2001年 | 202篇 |
2000年 | 217篇 |
1999年 | 159篇 |
1998年 | 102篇 |
1997年 | 119篇 |
1996年 | 101篇 |
1995年 | 76篇 |
1994年 | 57篇 |
1993年 | 58篇 |
1992年 | 46篇 |
1991年 | 37篇 |
1990年 | 41篇 |
1989年 | 33篇 |
1988年 | 35篇 |
1987年 | 27篇 |
1986年 | 18篇 |
1985年 | 30篇 |
1984年 | 14篇 |
1983年 | 4篇 |
1982年 | 18篇 |
1981年 | 18篇 |
1980年 | 17篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1974年 | 6篇 |
1936年 | 3篇 |
排序方式: 共有8493条查询结果,搜索用时 15 毫秒
61.
增长曲线模型中回归系数的广义根方估计 总被引:6,自引:0,他引:6
本文对增长曲线模型中的回归系数B提出了一种新的估计形式-广义根方估计的B(K),其中K=diag(k1,k2,…,kp)并证明了通过广义根方偏参数ki(i=1,2,…,p)的适当选取可使得该估计在均方误差矩阵的意义下优于已有的LS估计和根方估计,及广义根方估计是可容许估计,本文还给出了选取广义根方偏参数的两种方法,算法及一个应用实例。 相似文献
62.
本文研究非线性算子方程F(x)=y的解,结合最速下降法,Newton-Landweber迭代格式及正则化思想,在F满足适当的条件下,构造出新的双循环迭代格式。本文对格式的收敛性进行了严格论证,并估计出迭代格式的收敛精度。 相似文献
63.
The load-carrying capacity of circular plates made of a fiber-reinforced composite and loaded with axisymmetric transverse forces under axisymmetric boundary conditions is investigated. The plates can be freely supported or clamped along their contour. To the known yield condition used, in the plane of main bending moments, there correspond irregular hexagons, which depend on the mechanical properties of composite constituents and some characteristic geometrical parameters. It is shown that, depending on the ratio of ultimate radial and circumferential bending moments, in the plastic state, the circular plates (the central part of the clamped plates) take the form of a cone or a frustum of cone. For each of the cases, the limit load is found, which is a function of the above-mentioned mechanical parameters. The statically allowable fields of bending moments and the corresponding allowable fields of deflection rates are determined. The solutions found are exact. Special cases for the freely supported plates are analyzed, and the results obtained are presented in the form of graphs.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 2, pp. 177–192, March–April, 2005. 相似文献
64.
Cordula Grüttner Knut Müller Joachim Teller Fritz Westphal Allan Foreman Robert Ivkov 《Journal of magnetism and magnetic materials》2007
Bionized nanoferrite (BNF) particles with high specific power absorption rates were synthesized in the size range of 20–100 nm by high-pressure homogenization for targeted cancer therapy with alternating magnetic fields. Several strategies were used to conjugate antibodies to the BNF particles. These strategies were compared using an immunoassay to find optimal conditions to reach a high immunoreactivity of the final antibody–particle conjugate. 相似文献
65.
Following our investigation of the USA Standard and Poor index anti-bubble that started in August 2000 (Quant. Finance 2 (2002) 468), we analyze 38 world stock market indices and identify 21 “bearish anti-bubbles” and six “bullish anti-bubbles”. An “anti-bubble” is defined as a self-reinforcing price trajectory with self-similar expanding log-periodic oscillations. Mathematically, a bearish anti-bubble is characterize by a power law decrease of the price (or of the logarithm of the price) as a function of time and by expanding log-periodic oscillations. We propose that bearish anti-bubbles are created by positive price-to-price feedbacks feeding overall pessimism and negative market sentiment further strengthened by inter-personal interactions. Bullish anti-bubbles are here identified for the first time. The most striking discovery is that the majority of European and Western stock market indices as well as other stock indices exhibit practically the same log-periodic power law anti-bubble structure as found for the USA S&P500 index. These anti-bubbles are found to start approximately at the same time, August 2000, in all these markets. This shows a remarkable degree of worldwide synchronization. The descent of the worldwide stock markets since 2000 is thus an international event, suggesting the strengthening of globalization. 相似文献
66.
LIU Zhongkui 《数学年刊B辑(英文版)》2004,25(1):129-138
Let (S,≤) be an ordered set. Recall that (S,≤) is artinian if every strictly decreasingsequence of elements of S is ?nite, and that (S,≤) is narrow if every subset of pairwiseorder-incomparable elements of S is ?nite. Let S be a commutative monoid. Unl… 相似文献
67.
Silvia Lorenzo-Freire José M. Alonso-Meijide Balbina Casas-Méndez Ruud Hendrickx 《European Journal of Operational Research》2007
Calleja et al. [Calleja, P., Borm, P., Hendrickx, R., 2005. Multi-issue allocation situations. European Journal of Operational Research 164, 730–747] introduced multi-issue allocation situations with awards. In this paper, we extend the classical model of cooperative games with transferable utility to the cooperative games with transferable utility and awards. We define a run-to-the-bank rule for cooperative games with transferable utility and awards and characterise it in terms of a property of balanced contributions. We apply our main result to bankruptcy problems and multi-issue allocation situations with awards. 相似文献
68.
An efficient synthesis approach is developed which permits thecalculation of the steady-state frequency response of an assembly whichis comprised of linear components and nonlinear joints. Receptancematrices are used to characterize the linear components, which permitscondensation of the system to just the joint degrees-of-freedom.Furthermore, the calculated nonlinear joint forces are then used tostudy the power flow in the assembly, as well as detailed dynamicbehavior within the components. Integrated into the technique is acontinuation scheme which permits efficient parametric studies. 相似文献
69.
We consider the effects of quark masses to the perturbative thrust in e
+
e
− annihilation. In particular we show that perturbative power corrections resulting from non-zero quark masses considerably
alters the size of the non-perturbative power corrections and consequently, significantly changes the fitted value of αs. 相似文献
70.
This paper studies the problem of how changes in the design of the genetic algorithm (GA) have an effect on the results obtained in real-life applications. In this study, focused on the application of a GA to the tuning of technical trading rules in the context of financial markets, our tentative thesis is that the GA is robust with respect to design changes. The optimization of technical trading systems is a suitable area for the application of the GA metaheuristic, as the complexity of the problem grows exponentially as new technical rules are added to the system and as the answer time is crucial when applying the system to real-time data. Up to now, most of GAs applications to this subject obviated the question of possible “design dependence” in their results. The data we report, based on our experiments, do not allow us to refute the hypothesis of robustness of the GA to design implementation, when applying to technical trading systems tuning. 相似文献