全文获取类型
收费全文 | 12007篇 |
免费 | 259篇 |
国内免费 | 26篇 |
专业分类
化学 | 7044篇 |
晶体学 | 72篇 |
力学 | 286篇 |
综合类 | 1篇 |
数学 | 1517篇 |
物理学 | 3372篇 |
出版年
2021年 | 92篇 |
2020年 | 127篇 |
2019年 | 110篇 |
2018年 | 94篇 |
2016年 | 188篇 |
2015年 | 191篇 |
2014年 | 193篇 |
2013年 | 364篇 |
2012年 | 420篇 |
2011年 | 521篇 |
2010年 | 327篇 |
2009年 | 261篇 |
2008年 | 469篇 |
2007年 | 471篇 |
2006年 | 492篇 |
2005年 | 446篇 |
2004年 | 412篇 |
2003年 | 353篇 |
2002年 | 329篇 |
2001年 | 282篇 |
2000年 | 233篇 |
1999年 | 181篇 |
1998年 | 170篇 |
1997年 | 154篇 |
1996年 | 190篇 |
1995年 | 205篇 |
1994年 | 209篇 |
1993年 | 211篇 |
1992年 | 233篇 |
1991年 | 183篇 |
1990年 | 161篇 |
1989年 | 125篇 |
1988年 | 154篇 |
1987年 | 141篇 |
1986年 | 139篇 |
1985年 | 152篇 |
1984年 | 149篇 |
1983年 | 133篇 |
1982年 | 147篇 |
1981年 | 130篇 |
1980年 | 122篇 |
1979年 | 124篇 |
1978年 | 123篇 |
1977年 | 127篇 |
1976年 | 125篇 |
1975年 | 103篇 |
1974年 | 109篇 |
1973年 | 123篇 |
1972年 | 70篇 |
1971年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Rüdiger Schultz Leen Stougie Maarten H. van der Vlerk 《Mathematical Programming》1998,83(1-3):229-252
In this paper we present a framework for solving stochastic programs with complete integer recourse and discretely distributed right-hand side vector, using Gröbner basis methods from computational algebra to solve the numerous second-stage integer programs. Using structural properties of the expected integer recourse function, we prove that under mild conditions an optimal solution is contained in a finite set. Furthermore, we present a basic scheme to enumerate this set and suggest improvements to reduce the number of function evaluations needed. 相似文献
73.
R. Klein R. Grieser L. Hoog G. Huber I. Klaft P. Merz T. Kühl S. Schröder M. Grieser D. Habs W. Petrich D. Schwalm 《Zeitschrift für Physik A Hadrons and Nuclei》1992,342(4):455-461
We have performed for the first time precision spectroscopy on a coasting fast7Li+ ion beam in a storage ring. The ion beam moving with 6.4% speed of light was first electron cooled and then merged with two counterpropagating laser beams acting on two different hyperfine transitions sharing a common upper level (λ-system). One laser was frequency locked to thea 3 127J2 hfs frequency component established as a secondary frequency standard at 514 nm. The second laser was tuned over theλ-resonance, which was recorded relative to127J2 hfs components. This experiment is sensitive to the time dilation in fast moving frames and will lead to new limits for the verification of special relatively. The present status of the experiment and perspectives in accuracy are discussed. 相似文献
74.
A. Roberts M. L. von Bibra H-P. Gemünd E. Kreysa 《International Journal of Infrared and Millimeter Waves》1994,15(3):505-517
In this paper a comparison between a rigorous electromagnetic model for transmission through a hexagonal array of circular waveguides in a series of thick, metallic screens and experimental measurements in the far infrared is made. It is found that there is excellent agreement between theory and experiment when the frequency is below that where any diffracted orders propagate. The agreement is still very good above this frequency. Below a frequency approximately equal to the cut-off frequency of the circular waveguides little power is transmitted. As the thickness of the screen is increased, this decrease in transmission becomes more abrupt. Also, for thick screens, resonances appear in the transmission spectrum which are analogous to those which appear in the spectra of two grids separated by a distance comparable to the wavelength of the radiation being used. 相似文献
75.
76.
We investigated the photoluminescence (PL) properties of carbon nitride films (CNx) deposited by rf magnetron sputtering and compared them to their microstructure depending on the target self-bias. While many of the data are compatible with ‘a-C:H like’ PL properties the observed variation of the PL efficiency η with respect to the target bias cannot be easily explained by the standard models. It is suggested that the observed variation of η is rather dominated by a change in microstructure which depends on the bombardment intensity during growth than by the concentration of non-radiative centres. 相似文献
77.
Y. Akiyama P. von Brentano A. Gelberg 《Zeitschrift für Physik A Hadrons and Nuclei》1987,326(4):517-521
Energies of collective levels in178Hf and234U are compared with predictions of theSU (3) limit of thesdg Interacting Boson Model. All known positive parity states of178Hf below 1.8 MeV (with the exception of a 0+ band) have been satisfactorily reproduced. Most of the bands in234U are also described by the model. However, a few predicted states have no experimental counterpart. The introduction of theg-bosons strongly reduces the previously observed discrepancies between experimentalB(E2)'s in238U and thesd-IBM calculation. 相似文献
78.
H. Günther M. Foerste M. Kunze G. zu Putlitz U. von Stein 《Zeitschrift für Physik B Condensed Matter》1996,100(4):613-617
We review the previous conclusion [J.Y. Ryu, Y.C. Chung and S.D. Choi, Phys. Rev. B 32, 7769 (1984)] that the trace property Tr(ABC) = Tr(CAB) leads to two different cyclotron transition absorption formulae in the electron-phonon systems in the lowest order approximation. The pictorial expression and the calculated linewidths in Ge and Si show that the socalled EWC scheme is more seeming than the socalled MWC scheme. The difference is expected to disappear if we take into account all the higher order perturbation terms or start with the many body formalism in the complete scheme. 相似文献
79.
Hans Peters Hans van der Stel Ton Storcken 《Mathematical Methods of Operations Research》1993,38(2):213-229
A voting scheme assigns to each profile of alternatives reported byn individuals a compromise alternative. A voting scheme is strategy-proof if no individual is better off by lying, i.e., not reporting a best alternative. In this paper the main results concern the case where the set of alternatives is the Euclidean plane and the preferences are Euclidean. It is shown that for strategy-proof voting schemes continuity is equivalent to convexity of the range of the voting scheme. Using a result by Kim and Roush (1984), this leads to characterizations of surjective or unanimous, anonymous, strategy-proof voting schemes.Furthermore, the paper contains an extensive discussion of related results in the area. 相似文献
80.