全文获取类型
收费全文 | 12166篇 |
免费 | 1717篇 |
国内免费 | 1439篇 |
专业分类
化学 | 8325篇 |
晶体学 | 156篇 |
力学 | 875篇 |
综合类 | 105篇 |
数学 | 1447篇 |
物理学 | 4414篇 |
出版年
2024年 | 22篇 |
2023年 | 171篇 |
2022年 | 248篇 |
2021年 | 307篇 |
2020年 | 397篇 |
2019年 | 352篇 |
2018年 | 313篇 |
2017年 | 300篇 |
2016年 | 462篇 |
2015年 | 440篇 |
2014年 | 570篇 |
2013年 | 817篇 |
2012年 | 899篇 |
2011年 | 983篇 |
2010年 | 658篇 |
2009年 | 728篇 |
2008年 | 765篇 |
2007年 | 730篇 |
2006年 | 688篇 |
2005年 | 634篇 |
2004年 | 500篇 |
2003年 | 398篇 |
2002年 | 352篇 |
2001年 | 333篇 |
2000年 | 290篇 |
1999年 | 327篇 |
1998年 | 337篇 |
1997年 | 274篇 |
1996年 | 273篇 |
1995年 | 235篇 |
1994年 | 249篇 |
1993年 | 173篇 |
1992年 | 154篇 |
1991年 | 140篇 |
1990年 | 141篇 |
1989年 | 86篇 |
1988年 | 81篇 |
1987年 | 87篇 |
1986年 | 82篇 |
1985年 | 71篇 |
1984年 | 48篇 |
1983年 | 35篇 |
1982年 | 35篇 |
1981年 | 27篇 |
1980年 | 20篇 |
1979年 | 15篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
981.
982.
D.H. Shen A. Berlinger E. Nold W. Lai G.M. Luo 《Applied Physics A: Materials Science & Processing》1999,68(4):425-428
Received: 13 August 1998 / Published online: 10 February 1999 相似文献
983.
984.
J. H. Rohling J. Shen C. Wang J. Zhou C. E. Gu 《The European physical journal. Special topics》2008,153(1):111-113
In this work, an effective gas diffusion coefficient of a
porous medium was measured using photothermal deflection (PD) technique. An
in-house made Loschmidt diffusion cell with a photothermal-deflection probe
were employed to measure the effective gas diffusion coefficient of a gas
diffusion layer (GDL) with a porosity ε ≈ 0.7. The concentration
evolutions of CO2 in O2 with and without the GDL were measured,
respectively, using a transverse normal PD technique. The concentration
variations were used to deduce the gas diffusion coefficients in the
presence and absence of the GDL by solving mass diffusion equations. The
effective gas diffusion coefficient of the GDL was calculated from the
diffusion coefficients using a model of an equivalent resistance to
diffusion and found to be 4.39 × 10-6 m2s-1,
demonstrating that PD technique can be employed to determine the effective
gas diffusion coefficient of a porous medium. 相似文献
985.
Thermal-annealing has been widely used in modulating the oxygen content of manganites. In this work, we have studied the effect of annealing on the transport properties and magnetoresistance of junctions composed of a La0.9Ca0.1MnO3+6 film and a Nb-doped SrTiO3 substrate. We have demonstrated that the magnetoresistance of junctions is strongly dependent on the annealing conditions: Prom the junction annealed-in-air to the junction annealedin-vacuum, the magnetoresistance near 0-V bias can vary from ~-60% to N~0. A possible mechanism accounting for this phenomenon is discussed. 相似文献
986.
Superconducting La1.937Sr0.063CuO4 crystals grown by the travelling-solvent floating-zone technique were thermally treated under various temperatures and oxygen pressures for moderately adjusting the oxygen content. The response of intrinsic electronic property of the crystals to the change of hole density in La2-xSrxCuO4 in the vicinity of the magic doping of x= 1/16 (= 0.0625) is studied in detail by magnetic measurements under various fields up to 1 T. It is found that when the superconducting critical temperature (Tc) increases with the oxygen content, there appears also a new subtle electronic state that can be detected from the differential curves of diamagnetic susceptibility dx/dT of the crystal sample. In contrast with the intrinsic state, the new subtle electronic state is very fragile under the magnetic fields. Our results indicate that a moderate change in oxygen doping does not significantly modify the intrinsic electronic state originally existing at the magic doping level. 相似文献
987.
The effects of interstitial oxygen on superconducting electronic phases in strontium and oxygen co-doped La1.937Sr0.063CuO4+δ 下载免费PDF全文
Strontium and oxygen co-doped La1.937Sr0.063CuO4+δ superconductor with Tc≈ 40K, which is obtained by oxidizing strontium-doped starting ceramic sample La1.937Sr0.063CuO4 in NaC10 solution, is annealed under different conditions to allow interstitial oxygen to redistribute. The evolution of the intrinsic superconducting property with the oxygen redistribution is studied in detail by magnetic measurements in various fields. It is found that there occurs the electronic phase separation from the single superconducting phase with Tc ≈ 40 K into two coexisting superconducting states with values of Tc: 15 and 40K or of 15 and 35 K in this system, depending on annealing condition. Our results indicate that the 15, 35 and 40 K superconducting phases associated with the excess oxygen redistribution are all thermodynamically meta-stable intrinsic states in this Sr/O co-doped cuprate. 相似文献
988.
Study on the optical limiting properties of the mixed liquid of carbon black suspensions and
green tea solution by multi-pulse laser 下载免费PDF全文
The optical limiting properties of the mixed liquid of carbon black
suspensions (CBS) and green tea solution were studied by using an 8
ns laser pulse at 532\,nm. The optical limiting effects of the CBS
and mixed liquid have been compared between 5 and 10\,Hz repetition
frequencies with nanosecond laser pulse. The experimental results
indicate that the optical limiting threshold of the sample with the
incidence laser at 10\,Hz repetition frequency is lower than at
5\,Hz repetition frequency. The possible reasons for the influence
of the repetition frequency on the samples are discussed. And by
observing the optical radiant distributions when the laser pulse
passing through different samples, a possible mechanism for the
observed effects is suggested. At the same time, the result shows
that the optical limiting of CBS is the dominant factor to optical
limiting of the mixed liquid. 相似文献
989.
990.
Shen Ting-gen Zhou Yue-qun Ge Jun Yu Feng-chao Ji Pei-lai Wang Gang 《Journal of Russian Laser Research》2008,29(3):255-261
The method of finite-difference-time domain (FDTD) was used to study the characteristics of the patch antenna based on drilling
air holes in the PBG substrate. The results obtained show that the waves propagating along the substrate surface can be suppressed
by the drilled photonic crystal band gap (PBG) structure due to the influence of its forbidden band. The energy of the electromagnetic
waves is concentrated mainly in the substrate. As a result, patch antennas based on drilling air holes in the PBG substrate
have lower return losses (S11) in comparison with the conventional patch antennas; thus, a high gain is reached and the performance
is improved. Due to such the advantages, the use of patch antennas can be extended to such fields as mobile communication,
satellite communication, aviation, etc. 相似文献