全文获取类型
收费全文 | 5556篇 |
免费 | 768篇 |
国内免费 | 628篇 |
专业分类
化学 | 1917篇 |
晶体学 | 84篇 |
力学 | 794篇 |
综合类 | 97篇 |
数学 | 1340篇 |
物理学 | 2720篇 |
出版年
2024年 | 13篇 |
2023年 | 52篇 |
2022年 | 88篇 |
2021年 | 131篇 |
2020年 | 111篇 |
2019年 | 115篇 |
2018年 | 99篇 |
2017年 | 160篇 |
2016年 | 216篇 |
2015年 | 163篇 |
2014年 | 282篇 |
2013年 | 423篇 |
2012年 | 308篇 |
2011年 | 399篇 |
2010年 | 343篇 |
2009年 | 372篇 |
2008年 | 372篇 |
2007年 | 418篇 |
2006年 | 340篇 |
2005年 | 337篇 |
2004年 | 264篇 |
2003年 | 247篇 |
2002年 | 244篇 |
2001年 | 175篇 |
2000年 | 173篇 |
1999年 | 144篇 |
1998年 | 118篇 |
1997年 | 114篇 |
1996年 | 90篇 |
1995年 | 85篇 |
1994年 | 85篇 |
1993年 | 78篇 |
1992年 | 54篇 |
1991年 | 52篇 |
1990年 | 37篇 |
1989年 | 31篇 |
1988年 | 27篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 23篇 |
1984年 | 18篇 |
1983年 | 8篇 |
1982年 | 27篇 |
1981年 | 12篇 |
1980年 | 18篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 12篇 |
1974年 | 4篇 |
排序方式: 共有6952条查询结果,搜索用时 46 毫秒
861.
Zhouchao Wei 《Applied mathematics and computation》2010,217(1):422-429
In order to further understand a complex 3D dynamical system showing strange chaotic attractors with two stable node-foci near Hopf bifurcation point, we propose nonlinear control scheme to the system and the controlled system, depending on five parameters, can exhibit codimension one, two, and three Hopf bifurcations in a much larger parameter regain. The control strategy used keeps the equilibrium structure of the chaotic system and can be applied to degenerate Hopf bifurcation at the desired location with preferred stability. 相似文献
862.
F. Güngör 《Applied mathematics and computation》2010,217(8):4293-4294
We show that the group classification results of the article entitled “Group analysis of KdV equation with time dependent coefficients” which appeared in [A.G. Johnpillai, M.C. Khalique, Group analysis of KdV equation with time dependent coefficients, Appl. Math. Comput. 216 (2010) 3761-3771] can be obtained from those of a more general class by a change of variables. 相似文献
863.
Eric C.K. Cheung 《Insurance: Mathematics and Economics》2010,46(1):117-126
The structure of various Gerber-Shiu functions in Sparre Andersen models allowing for possible dependence between claim sizes and interclaim times is examined. The penalty function is assumed to depend on some or all of the surplus immediately prior to ruin, the deficit at ruin, the minimum surplus before ruin, and the surplus immediately after the second last claim before ruin. Defective joint and marginal distributions involving these quantities are derived. Many of the properties in the Sparre Andersen model without dependence are seen to hold in the present model as well. A discussion of Lundberg’s fundamental equation and the generalized adjustment coefficient is given, and the connection to a defective renewal equation is considered. The usual Sparre Andersen model without dependence is also discussed, and in particular the case with exponential claim sizes is considered. 相似文献
864.
This paper is devoted to a class of inverse coefficient problems for nonlinear elliptic hemivariational inequalities. The unknown coefficient of elliptic hemivariational inequalities depends on the gradient of the solution and belongs to a set of admissible coefficients. It is shown that the nonlinear elliptic hemivariational inequalities are uniquely solvable for the given class of coefficients. The result of existence of quasisolutions of the inverse problems is obtained. 相似文献
865.
本文研究了一个新的、基本的不含参量的Hilbert型不等式.应用改进的Euler-Maclaurin求和公式以估算权系数,证明了其常数系数为最佳值以及此不等式的等价式. 相似文献
866.
867.
高功率、长脉冲是高功率微波技术发展的趋势,提高微波器件的功率容量成为一项重要的任务,使用过模器件可以有效提高微波源的功率容量,然而却会带来微波源中同时存在多种模式的问题。为了识别一个X波段长脉冲过模高功率微波源的输出主模TM01模式,设计了一种在线选模定向耦合器,进行了理论分析和模拟优化设计。当频率范围为9.2~9.6 GHz时,模拟结果显示该选模耦合器对TM01模的耦合度为-54 dB,在400 MHz带宽内定向性大于35 dB,对TM02模的抑制度大于15 dB,功率容量可达到3 GW以上。 相似文献
868.
Unlike other natural network systems, assortativity can be observed in most human social networks, although it has been reported that a social dilemma situation represented by the prisoner’s dilemma favors dissortativity to enhance cooperation. We established a new coevolutionary model for both agents’ strategy and network topology, where teaching and learning agents coexist. Remarkably, this model enables agents’ enhancing cooperation more than a learners-only model on a time-frozen scale-free network and produces an underlying assortative network with a fair degree of power-law distribution. The model may imply how and why assortative networks are adaptive in human society. 相似文献
869.
The ideal gas has been reinvestigated in the framework of Tsallis nonextensive statistics, which can be called nonextensive gas. According to the modified thermodynamic relationships, and applying the nonextensive gas model to analyze actual gas, the relationship between the nonextensive parameter and the second virial coefficient can be deduced. On the other hand, this coefficient can also be expressed as the integration of interaction potential between the molecules of actual gas. This indicates that the nonextensive parameter may be related to the interaction potential. Our further analysis to the relation seems to imply that the nonextensive parameter is irrelevant to the thermodynamic temperature of the gas. 相似文献
870.
A vertical cylinder was applied as a heat source into a water pool; the vibrations were imposed into the heater with different heat fluxes, and the frequencies were adjusted at 10, 15, 20, and 25 Hz. An imaging system was employed to observe the produced bubbles around the cylindrical heat source. The results showed that the boiling heat transfer was enhanced under the vibrations with a shorter transient process, and the wall temperature also decreased. The best enhancement ratio was achieved at the frequency of 25 Hz and a heat flux value of 30 kW/m2 as a consequence of imposed vibrations. 相似文献