全文获取类型
收费全文 | 10853篇 |
免费 | 2411篇 |
国内免费 | 634篇 |
专业分类
化学 | 1538篇 |
晶体学 | 60篇 |
力学 | 2959篇 |
综合类 | 140篇 |
数学 | 2395篇 |
物理学 | 6806篇 |
出版年
2024年 | 18篇 |
2023年 | 106篇 |
2022年 | 159篇 |
2021年 | 224篇 |
2020年 | 315篇 |
2019年 | 250篇 |
2018年 | 292篇 |
2017年 | 333篇 |
2016年 | 365篇 |
2015年 | 299篇 |
2014年 | 580篇 |
2013年 | 730篇 |
2012年 | 650篇 |
2011年 | 809篇 |
2010年 | 647篇 |
2009年 | 662篇 |
2008年 | 734篇 |
2007年 | 734篇 |
2006年 | 689篇 |
2005年 | 675篇 |
2004年 | 615篇 |
2003年 | 588篇 |
2002年 | 468篇 |
2001年 | 433篇 |
2000年 | 352篇 |
1999年 | 290篇 |
1998年 | 276篇 |
1997年 | 227篇 |
1996年 | 177篇 |
1995年 | 184篇 |
1994年 | 138篇 |
1993年 | 148篇 |
1992年 | 118篇 |
1991年 | 119篇 |
1990年 | 81篇 |
1989年 | 79篇 |
1988年 | 67篇 |
1987年 | 55篇 |
1986年 | 34篇 |
1985年 | 33篇 |
1984年 | 30篇 |
1983年 | 15篇 |
1982年 | 27篇 |
1981年 | 19篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1973年 | 7篇 |
1971年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
51.
An infinite row of periodically spaced, identical rigid circularcylinders is excited by an acoustic line source which is parallelto the generators of the cylinders. A method for calculatingthe scattered field accurately and efficiently is presented.When the cylinders are sufficiently close together, Rayleigh–Blochsurface waves that propagate energy to infinity along the arrayare excited. An expression is derived which enables the amplitudesof these surface waves to be computed without requiring thesolution to the full scattering problem. 相似文献
52.
The spontaneous drift of the spiral wave in a finite domain in the complex Ginzburg-Landau equation is investigated numerically. By using the interactions between the spiral wave and its images, we propose a phenomenological theory to explain the observations. 相似文献
53.
T. Kasahara H.S. Park D. Shindo H. Yoshikawa T. Sato K. Kondo 《Journal of magnetism and magnetic materials》2006
Domain wall motion in Mn–Zn and Ni–Zn ferrites with applied magnetic fields is investigated by in situ observations with Lorentz microscopy and electron holography. It is found that both Mn–Zn and Ni–Zn ferrites have a mean grain size of approximately 10 μm and several pores with sizes ranging from 0.2 to 1.1 μm. In situ observations by Lorentz microscopy with an applied magnetic field reveals that in Mn–Zn ferrite, the domain walls move easily across the grain boundary, while in Ni–Zn ferrite, the domain walls move along the grain boundary but are pinned at the grain boundary and pores. From in situ observations of Ni–Zn ferrite by electron holography, it is clarified that domain wall pinning at the grain boundary retards a sensitive increase in magnetic flux parallel to the applied field direction, which is considered to result in high hysteresis loss. 相似文献
54.
用微分脉冲溶出伏安法研究了镍(11)与酸性铬兰K(ACBK)所生成的络合物在悬汞电极上的电化学特性及电化学反应机理,发现电极反应为镍与酸性铬兰K所生成的络合物吸附在电极表面后发生的不可逆还原。在HCl-硼砂介质中(pH8.67),络合物在-316mV处有一吸附还原峰,其峰电流与镍浓度在0.001~0.010μ/mL范围内呈现良好的线性关系,其最低检出浓度为0.0005μg/mL。 相似文献
55.
A method is developed for a stress analysis in an infinite elastic body containing two neighboring periodically cophasaly curved fibers located along two parallel lines. The stress distribution is studied when the body is loaded at infinity by uniformly distributed normal forces in the fiber direction. The investigation is carried out within the framework of a piecewise homogeneous body model with the use of exact three-dimensional equations of elasticity theory. Numerical results related to the stress distribution considered and the influence of interaction between the fibers on this distribution are given. 相似文献
56.
57.
We consider some types of packet discretization for continuous spectra in quantum scattering problems. As we previously showed, this discretization leads to a convenient finite-dimensional (i.e., matrix) approximation for integral operators in the scattering theory and allows reducing the solution of singular integral equations connected with the scattering theory to some suitable purely algebraic equations on an analytic basis. All singularities are explicitly singled out. Our primary emphasis is on realizing the method practically. 相似文献
58.
S. Schrader A. Penzkofer W. Holzer R. Velagapudi B. Grimm 《Journal of luminescence》2004,110(4):303-308
Optical, structural and morphological properties of thin films of polyparaphenylenevinylene (PPV) formed by an alkyl sulfinyl precursor route have been studied. Thin films were fabricated on an optical glass and on quartz glass either by spin-coating of the precursor solution or by layer-by-layer deposition using Langmuir–Blodgett technique. PPV precursor films were also spin-coated on gold-coated glass in order to study thin-film optical parameters by surface plasmon spectroscopy. We have been successful in forming about 40 precursor mono layers on quartz glass by Langmuir–Blodgett technique using optimized surface pressure and dipping conditions. After thermal conversion of the precursor layers good quality fluorescent PPV films of yellow colour have been obtained. Optical characterization of the films was carried out by linear absorption and emission spectroscopy, ellipsometry, and surface plasmon spectroscopy. Structural and morphological studies on the thin films were carried out by using X-ray scattering and atomic force microscopy. Wave-guided travelling-wave laser action has been achieved in a PPV film on quartz glass. The sample was transversally pumped with picosecond laser pulses (wavelength 347.15 nm, duration 35 ps). Laser emission occurred at 550 nm for pump pulse energy densities above . 相似文献
59.
Othman Belhadj Miled David Grosso Jacques Livage 《Journal of Physics and Chemistry of Solids》2004,65(10):1751-1755
This paper describes the synthesis and optical pH sensing properties of a pH indicator dye activated mesostructured silica coated optical fibre. The pH-sensitive dye bromothymol blue was incorporated into the mesostructure sol precursor and thin films/coatings were used for pH-sensing applications without prior removal of the surfactant. The pH sensitivity range and operating wavelength were analysed by absorption measurements on layer dip-coated on glass slides. The pH sensing properties of coated optical fibre were tested by evanescent wave method. Experiments were carried out by using a series of solutions of known pH. No leaching was observed (except at very high pH) and an excellent reversibility was obtained between pH=2 and 5. 相似文献
60.
A. López-Ortega 《General Relativity and Gravitation》2004,36(6):1299-1319
We show that the Dirac equation is separable in the circularly symmetric metric in three dimensions and when the background spacetime is de Sitter we find exact solutions to the radial equations. Using these results we show that the de Sitter horizon has a cross section equal to zero for the massless Dirac field, as in the case of the scalar field. Also, using the improved brick wall model we calculate the fermionic entropy associated with the de Sitter horizon and we compare it with some results previously published. 相似文献