全文获取类型
收费全文 | 15828篇 |
免费 | 241篇 |
国内免费 | 67篇 |
专业分类
化学 | 5787篇 |
晶体学 | 358篇 |
力学 | 984篇 |
综合类 | 3篇 |
数学 | 1440篇 |
物理学 | 7564篇 |
出版年
2023年 | 61篇 |
2022年 | 178篇 |
2021年 | 149篇 |
2020年 | 86篇 |
2019年 | 102篇 |
2018年 | 198篇 |
2017年 | 169篇 |
2016年 | 282篇 |
2015年 | 199篇 |
2014年 | 339篇 |
2013年 | 693篇 |
2012年 | 871篇 |
2011年 | 1138篇 |
2010年 | 821篇 |
2009年 | 807篇 |
2008年 | 916篇 |
2007年 | 918篇 |
2006年 | 936篇 |
2005年 | 747篇 |
2004年 | 660篇 |
2003年 | 510篇 |
2002年 | 487篇 |
2001年 | 910篇 |
2000年 | 609篇 |
1999年 | 502篇 |
1998年 | 330篇 |
1997年 | 343篇 |
1996年 | 263篇 |
1995年 | 216篇 |
1994年 | 210篇 |
1993年 | 162篇 |
1992年 | 180篇 |
1991年 | 156篇 |
1990年 | 145篇 |
1989年 | 122篇 |
1988年 | 97篇 |
1987年 | 88篇 |
1986年 | 71篇 |
1985年 | 77篇 |
1984年 | 57篇 |
1983年 | 37篇 |
1982年 | 28篇 |
1981年 | 28篇 |
1980年 | 17篇 |
1978年 | 17篇 |
1977年 | 18篇 |
1976年 | 27篇 |
1975年 | 27篇 |
1974年 | 21篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Y.?Ni H.?Liu F.?Wang G.?Yin J.?Hong X.?Ma Z.?XuEmail author 《Applied Physics A: Materials Science & Processing》2004,79(8):2007-2011
We report fabrication of CuS particles with solid, hollow, spherical and tubular structures in a simple aqueous system under microwave irradiation, employing CuSO4 and Na2S2O3 as the starting materials without assistance of any surfactant or template. Energy-dispersive X-ray analysis and an X-ray powder diffraction pattern proved that the product is hexagonal CuS phase. The morphologies of the product were observed by scanning electron microscopy and transmission electron microscopy. Some factors affecting the morphologies of the product are discussed. PACS 81.05.Hd; 81.07.Bc; 81.16.Be; 81.16.Dn; 81.20.Ka 相似文献
992.
X.H.?LiuEmail author M.H.?Hong W.D.?Song G.X.?Chen J.F.?Chong J.P.?Wang Y.H.?Wu T.C.?Chong 《Applied Physics A: Materials Science & Processing》2004,78(3):423-425
Barium ferrite (BaFe12O19) thin films have been deposited by pulsed laser deposition at 900 °C in 250 mTorr oxygen on Si substrates with Pt(111) underlayers. The barium ferrite films contained platelet grains and a small amount of acicular grains, with sizes of 300 nm and 80×300 nm, respectively, and had a surface roughness of 11 nm. Vibrating-sample magnetometer measurements indicated that the BaFe12O19 films have some perpendicular orientation, with a perpendicular squareness of 0.64 and an in-plane squareness of 0.28. The saturation magnetization is about 190 emu/cc. The perpendicular and in-plane coercivities are 2.1 kOe and 1.6 kOe, respectively. PACS 75.50.Ss; 75.60.Ej; 75.70.Ak; 68.55.Ik 相似文献
993.
Vibrated sessile drops: Transition between pinned and mobile contact line oscillations 总被引:1,自引:0,他引:1
Noblin X Buguin A Brochard-Wyart F 《The European physical journal. E, Soft matter》2004,14(4):395-404
We study the effects of vertical vibrations on non-wetting large water sessile drops flattened by gravity. The solid substrate is characterized by a finite contact angle hysteresis (10-15 degrees). By varying the frequency and the amplitude of the vertical displacement, we observe two types of oscillations. At low amplitude, the contact line remains pinned and the drop presents eigen modes at different resonance frequencies. At higher amplitude, the contact line moves: it remains circular but its radius oscillates at the excitation frequency. The transition between these two regimes arises when the variations of contact angle exceed the contact angle hysteresis. We interpret different features of these oscillations, such as the decrease of the resonance frequencies at larger vibration amplitudes. The hysteresis acts as solid friction on the contour oscillations, and gives rise to a stick-slip regime at intermediate amplitude.Received: 4 April 2004, Published online: 10 August 2004PACS:
47.55.Dz Drops and bubbles - 68.08.Bc Wetting - 47.35. + i Hydrodynamic waves 相似文献
994.
A crisis of a stochastic web 总被引:1,自引:0,他引:1
Y.-M.?Jiang Y.-Q.?Lu X.-G.?Chao D.-R.?HeEmail author 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2004,29(2):285-292
In a kicked rotor subjected to a piecewise-continuous force field, it is observed that a stochastic web and the chaotic diffusion on it suddenly change to transients when an adjustable parameter drives the dissipation. This phenomenon appears to be a new crisis type, which occurs in systems where conservative dynamics may be converted to a dissipative one with a contraction rate showing linear time dependence. It is analytically and numerically shown that, in the crisis, the lifetime dependence obeys universal scaling law suggested by Grebogy, Ott, and Yorke [Phys. Rev. Lett. 57, 1284 (1986)], and the scaling exponent takes a special value, 1, due to the dissipation characteristics. Additionally presented is another power law that describes, from another viewpoint, the transition of a conservative stochastic web (which is a fat fractal) to a non-attracting thin fractal (the strange repeller).Received: 13 December 2003, Published online: 9 March 2004PACS:
05.45.Ac Low-dimensional chaos 相似文献
995.
996.
Nonlinear optical responses due to exciton-phonon interactions in strongly coupled exciton-phonon systems 总被引:2,自引:0,他引:2
K.-D.?ZhuEmail author X.-Z.?Yuan J.-J.?Dong W.-S.?Li 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2004,30(1):117-121
The excitonic nonlinear optical responses due to exciton-phonon interactions in strongly coupled exciton-phonon systems are investigated theoretically. It is shown that the influence of exciton-phonon interactions on the nonlinear optical absorptions and Kerr nonlinear coefficients is significant as the signal field frequency detuning from the exciton frequency approaches to the optical phonon frequency. How to manipulate the nonlinear optical responses by using the control fields is also presented.Received: 16 March 2004, Published online: 4 May 2004PACS:
42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption - 42.50.Hz Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift - 42.25.Bs Wave propagation, transmission and absorption - 72.80.Le Polymers; organic compounds (including organic semiconductors) 相似文献
997.
Lee HJ Jin ZX Aleshin AN Lee JY Goh MJ Akagi K Kim YS Kim DW Park YW 《Journal of the American Chemical Society》2004,126(51):16722-16723
To study the transport properties of individual helical polyacetylene (PA) fibers, we developed a method to extract a single fiber from tightly entangled ropes of helical PA bulk film. After a few minutes of sonication of a piece of helical PA bulk film in an organic solution containing surfactant, a droplet of solution is deposited on the pre-pattened electrode under argon atmosphere. AFM images show that extracted helical PA fibers are typically 10 mum in length and 100-200 nm in diameter. We found that the helicity of bulk materials is conserved. We present the temperature dependencies of current-voltage characteristics of individual helical PA fibers doped with iodine. 相似文献
998.
N. X. Tan 《Journal of Optimization Theory and Applications》2004,123(3):619-638
Quasivariational inclusion problems are formulated and sufficient conditions on the existence of solutions are shown. As special cases, we obtain several results on the existence of solutions of general vector ideal, proper, Pareto, weak quasioptimization problems, quasivariational inequalities, and vector quasiequilibrium problems. Further, we prove theorems on the existence for solutions of systems of these inclusions. As a corollary, we obtain an ideal minimax theorem concerning vector functions. 相似文献
999.
Alnaser AS Tong XM Osipov T Voss S Maharjan CM Ranitovic P Ulrich B Shan B Chang Z Lin CD Cocke CL 《Physical review letters》2004,93(18):183202
We have measured coincident ion pairs produced in the Coulomb explosion of H2 by 8-30 fs laser pulses at different laser intensities. We show how the Coulomb explosion of H2 can be experimentally controlled by tuning the appropriate pulse duration and laser intensity. For laser pulses less than 15 fs, we found that the rescattering-induced Coulomb explosion is dominated by first-return recollisions, while for longer pulses and at the proper laser intensity, the third return can be made to be the major one. Additionally, by choosing suitable pulse duration and laser intensity, we show H2 Coulomb explosion proceeding through three distinct processes that are simultaneously observable, each exhibiting different characteristics and revealing distinctive time information about the H2 evolution in the laser pulse. 相似文献
1000.
Alexopoulos T Arenton M Barbosa RF Barker AR Bellantoni L Bellavance A Blucher E Bock GJ Cheu E Childress S Coleman R Corcoran MD Cox B Erwin AR Ford R Glazov A Golossanov A Graham J Hamm J Hanagaki K Hsiung YB Huang H Jejer V Jensen DA Kessler R Kobrak HG Kotera K LaDue J Ledovskoy A McBride PL Monnier E Nelson KS Nguyen H Niclasen R Prasad V Qi XR Ramberg EJ Ray RE Ronquest M Santos E Shanahan P Shields J Slater W Smith D Solomey N Swallow EC Toale PA Tschirhart R Wah YW Wang J White HB 《Physical review letters》2004,93(18):181802
We present a determination of the Cabibbo-Kobayashi-Maskawa parameter |V(us)| based on new measurements of the six largest K(L) branching fractions and semileptonic form factors by the KTeV (E832) experiment at Fermilab. We find |V(us)|=0.2252+/-0.0008(KTeV)+/-0.0021(ext), where the errors are from KTeV measurements and from external sources. We also use the measured branching fractions to determine the CP violation parameter |eta(+-)|=(2.228+/-0.005(KTeV)+/-0.009(ext))x10(-3). 相似文献