全文获取类型
收费全文 | 101859篇 |
免费 | 28368篇 |
国内免费 | 27074篇 |
专业分类
化学 | 65741篇 |
晶体学 | 2237篇 |
力学 | 7018篇 |
综合类 | 1540篇 |
数学 | 14248篇 |
物理学 | 66517篇 |
出版年
2024年 | 503篇 |
2023年 | 926篇 |
2022年 | 1644篇 |
2021年 | 1579篇 |
2020年 | 1759篇 |
2019年 | 2180篇 |
2018年 | 2139篇 |
2017年 | 3222篇 |
2016年 | 2896篇 |
2015年 | 3551篇 |
2014年 | 3694篇 |
2013年 | 5736篇 |
2012年 | 6168篇 |
2011年 | 8111篇 |
2010年 | 11551篇 |
2009年 | 12115篇 |
2008年 | 6106篇 |
2007年 | 5373篇 |
2006年 | 5110篇 |
2005年 | 5151篇 |
2004年 | 5482篇 |
2003年 | 4228篇 |
2002年 | 4069篇 |
2001年 | 4488篇 |
2000年 | 3890篇 |
1999年 | 3369篇 |
1998年 | 2537篇 |
1997年 | 2260篇 |
1996年 | 2522篇 |
1995年 | 2962篇 |
1994年 | 3021篇 |
1993年 | 3099篇 |
1992年 | 2635篇 |
1991年 | 2265篇 |
1990年 | 1910篇 |
1989年 | 2040篇 |
1988年 | 1995篇 |
1987年 | 1256篇 |
1986年 | 1305篇 |
1985年 | 910篇 |
1984年 | 1052篇 |
1983年 | 443篇 |
1982年 | 947篇 |
1981年 | 792篇 |
1980年 | 817篇 |
1979年 | 568篇 |
1978年 | 552篇 |
1977年 | 642篇 |
1976年 | 1048篇 |
1972年 | 534篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
V. T. Plaksiy O. N. Suchoruchko B. P. Yefimov A. P. Kasyanenko 《International Journal of Infrared and Millimeter Waves》2002,23(4):645-650
Bismuth, antimony and its alloys are the typical representatives of a class of semimetals, which electric conductance is lower in 102-103 times, than of usual well conducting an electrical current metals. The alloys bismuth with antimony have semi-conductor properties in wide area of compositions at temperatures below 77 °K. The semimetals are rather perspective materials from the point of view of their probable application in various devices [1,2,3].In present time the semimetal alloys BiSb have wide application in thermoelectric generators and refrigerators. In work [3] the opportunity of use of semimetals BiSb with percentage content of Bi and Sb from 8 % up to 25 % was shown as high-sensitivity and of small inertion indicators of the mm range radiation where thermoelectric effect is used. The principle of action of such indicators is based on occurrence of temperature gradient in a semimetal crystal BiSb that has two contacts of the various area with flowing electrical current. Basic element of such device is the dot contact metal - semimetal. One of the main characteristics is volt-watt sensitivity of metal-semimetal BiSb contact which calculating is shown in present work. 相似文献
992.
993.
由Q-Nd:YAG脉冲激光(波长1.06μm,脉宽10 ns)烧蚀Al靶产生等离子体.观测了在低气压和直流电场条件下的Al等离子体发射光谱.研究了激光功率密度和直流电场对各谱线强度的影响,分析了谱线半高全宽与外加电压,等离子体电子温度与激光能量的变化规律.结果表明,直流电场对铝原子谱线强度有显著的增强,铝原子谱线的半高全宽与直流电场的外加电压基本上呈线性关系. 相似文献
994.
995.
利用溶胶凝胶法在SiO2Si衬底上沉积高取向的V2O5薄膜,在压强低于2Pa,温度高于400℃的条件下,对V2O5薄膜进行真空烘烤,获得了电阻率变化3个数量级以上、弛豫宽度为62℃的VO2多晶薄膜.以X射线衍射(XRD)、扫描电子显微镜(SEM)图和电阻率转换特性等实验结果为依据,详细分析了溶胶凝胶薄膜在真空烘烤时从V2O5向VO2的转化,它经历了从VnO2n+1(n=2,3,4,6)到VO2的过程.实验证明,根据选择合适的成膜热处理条件和真空烘烤条件是实现溶胶凝胶V2O5结构向VO2结构成功转换的关键
关键词:
溶胶-凝胶法 氧化钒薄膜 VO2膜转换特性 相似文献
996.
The paper presents an analytical study of blood flow through a stenosed artery using a suitable mathematical model. The artery is modelled as an anisotropic viscoelastic cylindrical tube containing a non-Newtonian viscous incompressible fluid representing blood. The blood flow is assumed to be characterized by the Herschel–Bulkley model. The effect of the surrounding connective tissues on the motion of the arterial wall has been incorporated. Initially, the relevant solutions of the boundary value problem are obtained in the Laplace transform space, through the use of a suitable finite difference technique. Laplace inversion is carried out by employing suitable numerical techniques. Finally, the variations of the vascular wall displacements, the velocity distribution of the blood flow, the flux, the resistance to flow and the wall shear stress in the stenotic region are quantified through numerical computations and presented graphically. 相似文献
997.
XU Yichao CHEN Minru & MA Songya Academy of Mathematics Systems Science Chinese Academy of Sciences Beijing China College of Mathematics Information Sciences Henan University Kaifeng China 《中国科学A辑(英文版)》2006,49(10):1392-1404
We known that the maximal connected holomorphic automorphism group Aut (D)(0) is a semi-direct product of the triangle group T(D) and the maximal connected isotropic subgroup Iso(D)(0) of a fixed point in the complex homogeneous bounded domain D and any complex homogeneous bounded domain is holomorphic isomorphic to a normal Siegel domain D(VN,F). In this paper, we give the explicit formula of any holomorphic automorphism in T(D(VN, F)) and Iso(D(VN,F))(0), where G(0) is the unit connected component of the Lie group G. 相似文献
998.
Summary Cold neutrons at the external neutron guide laboratory (ELLA) of the KFA Jülich are used to demonstrate their profitable application
for multielement characterization of biological materials. The set-up and experimental conditions of the Prompt Gamma Cold
Neutron Activation Analysis (PGCNAA) device is described in detail. Results for C, H, N, S, K, B, and Cd using synthetic standards
and the “ratio” technique for calculation are reported for several reference materials and prove the method to be reliable
and complementary with respect to the elements being determined by INAA.
IAEA fellow at the KFA from 6. 3. 91 to 2. 9. 91 on contract No. VIE/9016R. 相似文献
999.
1000.
A detailed study of the oxidation of plasma deposited amorphous silicon (a-Si : H) using infrared phase modulated ellipsometry (IRPME) is presented. a-Si : H is found to be resistant against air oxidation confirming previous measurements. A 5–6 Å thick oxide layer at the surface of a-Si : H is observed after a few months of exposure to air. The extreme sensitivity of IRPME is emphasized. In particular Si-O-Si and (On)Si-H stretching vibrations are identified at the film surface at the submonolayer level. The oxidation mechanisms are discussed. The weak reactivity of a-Si : H with atmosphere is correlated with the presence of a hydrogen rich thin layer at the top surface. 相似文献