全文获取类型
收费全文 | 14181篇 |
免费 | 1695篇 |
国内免费 | 1751篇 |
专业分类
化学 | 5522篇 |
晶体学 | 105篇 |
力学 | 2109篇 |
综合类 | 228篇 |
数学 | 7204篇 |
物理学 | 2459篇 |
出版年
2024年 | 43篇 |
2023年 | 165篇 |
2022年 | 292篇 |
2021年 | 405篇 |
2020年 | 501篇 |
2019年 | 442篇 |
2018年 | 441篇 |
2017年 | 527篇 |
2016年 | 638篇 |
2015年 | 418篇 |
2014年 | 665篇 |
2013年 | 1268篇 |
2012年 | 797篇 |
2011年 | 783篇 |
2010年 | 685篇 |
2009年 | 856篇 |
2008年 | 909篇 |
2007年 | 958篇 |
2006年 | 781篇 |
2005年 | 692篇 |
2004年 | 640篇 |
2003年 | 557篇 |
2002年 | 558篇 |
2001年 | 453篇 |
2000年 | 428篇 |
1999年 | 442篇 |
1998年 | 339篇 |
1997年 | 291篇 |
1996年 | 257篇 |
1995年 | 239篇 |
1994年 | 185篇 |
1993年 | 164篇 |
1992年 | 119篇 |
1991年 | 123篇 |
1990年 | 87篇 |
1989年 | 64篇 |
1988年 | 53篇 |
1987年 | 48篇 |
1986年 | 38篇 |
1985年 | 52篇 |
1984年 | 46篇 |
1983年 | 24篇 |
1982年 | 31篇 |
1981年 | 26篇 |
1980年 | 28篇 |
1979年 | 21篇 |
1978年 | 10篇 |
1977年 | 17篇 |
1976年 | 7篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
UNIFORMBOUNDEDNESSANDUNIFORMSTABILITYOFAKINDOFDELAY──DIFFERENTIALEQUATIONS¥ZhengBunan(GuangxiNormalUniversity)Abstract:Thispa... 相似文献
972.
Nikolaos Halidias 《Journal of Mathematical Analysis and Applications》2002,276(1):13-27
In this paper we prove two existence theorems for elliptic problems with discontinuities. The first one is a noncoercive Dirichlet problem and the second one is a Neumann problem. We do not use the method of upper and lower solutions. For Neumann problems we assume that f is nondecreasing. We use the critical point theory for locally Lipschitz functionals. 相似文献
973.
In this paper, we consider a predator-prey system with stage structure and harvesting (where the predator population has two stages, an immature stage and a mature stage with harvesting, and the growth of the prey population is of Lotka-Volterra nature). We obtain the conditions of the globally asymptotic stability for three nonne-gative equilibria of this system. 相似文献
974.
975.
S. K. Zavriev 《Journal of Optimization Theory and Applications》1996,91(1):185-214
The steepest-descent technique dealing with the perturbed values of the objective function and its gradients and with nonexact line searches is considered. Attention is given to the case where the perturbations do not decrease on the algorithm trajectories; the aim is to investigate how perturbations at every iteration of the algorithm perturb its original attractor set.Based on the Liapunov direct method for attraction analysis of discrete-time processes, a sharp estimation of the attractor set generated by a perturbed steepest-descent technique with respect to the perturbation magnitudes is obtained. Some global optimization properties of finite-difference analogues of the gradient method are discovered. These properties are not inherent in methods which use exact gradients.The author is grateful to the referees for many useful suggestions. 相似文献
976.
Optical solitary waves that propagate in a Kerr medium exhibiting a power-law nonlocal response are studied analytically. The first-principles stability analysis based on quantum field theory shows that within the whole range of the exponent (the fractal dimension) the solitary wave can be stabilized. 相似文献
977.
CONVERGENCEANDSTABILITYOFSOLUTIONSOFCERTAININFINITEDELAYDIFFERENTIALEQUATIONSChenWuhua(GuangXiNationalInstitute,Abstract:ByCo... 相似文献
978.
A. V. Dem'yanov I. V. Kochetov A. P. Napartovich S. Longo M. Capitei 《Plasma Chemistry and Plasma Processing》1996,16(1):121-140
The satbilit r of the pumping discharge for XeCI (Ne/Xe/HCI) lasers is investigated by using different one-dimensional models, considering both bulk discharge instabilities and filamentary ones. It is found that the bulk stability in a XeCl laser discharge can he improved, under certain conditions, due to the vihrational excitation of HCl molecules: this effect is studied by using different models for the HCl vihrational kinetics. It is established that the very short instability time found in experiments cannot he explained as a result of hulk instability of the discharge. On the other hand, a satisfactory comparison with experiments can he obtained by adding to the model a simplified microinstability which develops in the discharge. 相似文献
979.
980.