全文获取类型
收费全文 | 50391篇 |
免费 | 1644篇 |
国内免费 | 33篇 |
专业分类
化学 | 30851篇 |
晶体学 | 254篇 |
力学 | 893篇 |
综合类 | 1篇 |
数学 | 9381篇 |
物理学 | 10688篇 |
出版年
2023年 | 357篇 |
2022年 | 371篇 |
2021年 | 567篇 |
2020年 | 719篇 |
2019年 | 685篇 |
2018年 | 999篇 |
2017年 | 925篇 |
2016年 | 1843篇 |
2015年 | 1480篇 |
2014年 | 1480篇 |
2013年 | 3269篇 |
2012年 | 3120篇 |
2011年 | 2969篇 |
2010年 | 1972篇 |
2009年 | 1676篇 |
2008年 | 2618篇 |
2007年 | 2415篇 |
2006年 | 2137篇 |
2005年 | 2200篇 |
2004年 | 1902篇 |
2003年 | 1592篇 |
2002年 | 1376篇 |
2001年 | 1007篇 |
2000年 | 1007篇 |
1999年 | 707篇 |
1998年 | 551篇 |
1997年 | 475篇 |
1996年 | 637篇 |
1995年 | 459篇 |
1994年 | 536篇 |
1993年 | 470篇 |
1992年 | 489篇 |
1991年 | 423篇 |
1990年 | 472篇 |
1989年 | 392篇 |
1988年 | 390篇 |
1987年 | 351篇 |
1986年 | 336篇 |
1985年 | 471篇 |
1984年 | 448篇 |
1983年 | 343篇 |
1982年 | 349篇 |
1981年 | 371篇 |
1980年 | 300篇 |
1979年 | 290篇 |
1978年 | 289篇 |
1977年 | 272篇 |
1976年 | 282篇 |
1974年 | 257篇 |
1973年 | 268篇 |
排序方式: 共有10000条查询结果,搜索用时 290 毫秒
81.
P. Kolář 《Czechoslovak Journal of Physics》1989,39(11):1317-1320
Conclusions The sets (3) and (4) of condensates have been compared using the QCD sum rules (2) with indefinite weight functions. A bad matching between both sets of condensates and experimental data has been obtained. The standard values (3) appear to be closer to data but some increase ofQ is necessary to improve the agreement. Only higher values ofm
0
2
could change the results of this analysis. It is interesting that negative values ofm
0
2
considerably improve the agreement with data; note that this quantity cannot be determined with a sufficient accuracy. We conclude that the QCD sum rules (2) cannot definitely determine a privileged set of condensates.Dedicated to Academician Václav Votruba on the occasion of his eightieth birthday. 相似文献
82.
Time structure of iodine laser pulse in the free running mode of operation was studied using the power amplifier of laser system PERUN as the laser oscillator. Two characteristic shapes of laser pulse correspond to different regimes of laser operation, the existence of which is ascribed to the critical concentration of I2 molecules. Simultaneously an additional chemical pumping was proved at least in the initial phase of photodissociation and in a late-time lasing after the end of flashlamps pumping light. 相似文献
83.
Flávio A. Pavan Yoshitaka Gushikem Celso C. Moro Tania M. Costa Edilson V. Benvenutti 《Colloid and polymer science》2003,281(2):173-177
Anilinepropylsilica xerogel was obtained by using an appropriate organosilane and tetraethyl orthosilicate as precursor reagents. The gelation was carried out using HF and NaF as catalysts. The presence of Na+ (when NaF was used) resulted in a decrease in the final organic content of the materials. This effect was interpreted as an inhibition of the organosilane polycondensation possibly due to the Na+ interaction with the SiO- groups of the hydrolyzed organosilane. The presence of Na+ also results in morphological changes in the xerogels. 相似文献
84.
Thermodynamic fluctuations in systems that are in nonequilibrium steady states are always spatially long ranged, in contrast to fluctuations in thermodynamic equilibrium. In the present paper we consider a fluid subjected to a stationary temperature gradient. Two different physical mechanisms have been identified by which the temperature gradient causes long-ranged fluctuations. One cause is the presence of couplings between fluctuating fields. Secondly, spatial variation of the strength of random forces, resulting from the local version of the fluctuation-dissipation theorem, has also been shown to generate long-ranged fluctuations. We evaluate the contributions to the long-ranged temperature fluctuations due to both mechanisms. While the inhomogeneously correlated Langevin noise does lead to long-ranged fluctuations, in practice, they turn out to be negligible as compared to nonequilibrium temperature fluctuations resulting from the coupling between temperature and velocity fluctuations. 相似文献
85.
J.-F. Pascual-Sánchez A. San Miguel F. Vicente 《General Relativity and Gravitation》2004,36(9):2075-2083
We analyze the geometry of a rotating disk with a tangential acceleration in the framework of the theory of Special Relativity, using the kinematic linear differential system that verifies the relative position vector of time-like curves in a Fermi reference. A numerical integration of these equations for a generic initial value problem is made up and the results are compared with those obtained in other works. 相似文献
86.
87.
88.
89.
90.
One of the most ignored, but urgent and vital challenges confronting society today is the vulnerability of urban areas to extreme events. Current organization of response systems, predominantly based on a command and control model, limits their effectiveness and efficiency. Particularly, in decision‐making processes where a large number of actors may be involved. In this article, a new distributed collaborative decision‐making model is proposed to overcome command and control limitations encountered in stressful, hostile, chaotic, and large‐scale settings. This model was derived by borrowing concepts from the collective decision making of honeybees foraging, a successful process in solving complex tasks within complex settings. The model introduced in this article was evaluated through differential equations, i.e., continuous analysis, and difference equations, i.e., discrete analysis. The most important result found is that the best available option in any large‐scale decision‐making problem can be configured as an attractor, in a distributed and timely manner. We suggest that the proposed model has the potential to facilitate decision‐making processes in large‐scale settings. © 2005 Wiley Periodicals, Inc. Complexity 11:28–38, 2005 相似文献