全文获取类型
收费全文 | 19008篇 |
免费 | 3583篇 |
国内免费 | 2675篇 |
专业分类
化学 | 12360篇 |
晶体学 | 284篇 |
力学 | 2334篇 |
综合类 | 201篇 |
数学 | 2491篇 |
物理学 | 7596篇 |
出版年
2024年 | 17篇 |
2023年 | 217篇 |
2022年 | 395篇 |
2021年 | 570篇 |
2020年 | 769篇 |
2019年 | 657篇 |
2018年 | 677篇 |
2017年 | 789篇 |
2016年 | 939篇 |
2015年 | 836篇 |
2014年 | 1161篇 |
2013年 | 2042篇 |
2012年 | 1294篇 |
2011年 | 1280篇 |
2010年 | 1059篇 |
2009年 | 1138篇 |
2008年 | 1173篇 |
2007年 | 1231篇 |
2006年 | 1118篇 |
2005年 | 991篇 |
2004年 | 891篇 |
2003年 | 866篇 |
2002年 | 655篇 |
2001年 | 617篇 |
2000年 | 608篇 |
1999年 | 468篇 |
1998年 | 410篇 |
1997年 | 308篇 |
1996年 | 301篇 |
1995年 | 286篇 |
1994年 | 273篇 |
1993年 | 214篇 |
1992年 | 185篇 |
1991年 | 139篇 |
1990年 | 118篇 |
1989年 | 89篇 |
1988年 | 79篇 |
1987年 | 65篇 |
1986年 | 61篇 |
1985年 | 53篇 |
1984年 | 41篇 |
1983年 | 15篇 |
1982年 | 42篇 |
1981年 | 19篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1972年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
A mathematical model of laser beam treatment of double layer alloys (Ni/Fe, Al/Fe and Cr/Fe systems) describing the effect of laser beam on different physical and geometrical parameters of coated layer system has been adapted. The numerical solutions of the non-homogeneous heat-transport differential equation could estimate the temperature of the treated region.The suggested model allows investigation of the temperature distribution as a function of treated surface and laser parameters. The physical parameters of the treated materials were taken as functions of temperature due to the change in the temperature of the treated double layer materials. 相似文献
102.
An m‐covering of a graph G is a spanning subgraph of G with maximum degree at most m. In this paper, we shall show that every 3‐connected graph on a surface with Euler genus k ≥ 2 with sufficiently large representativity has a 2‐connected 7‐covering with at most 6k ? 12 vertices of degree 7. We also construct, for every surface F2 with Euler genus k ≥ 2, a 3‐connected graph G on F2 with arbitrarily large representativity each of whose 2‐connected 7‐coverings contains at least 6k ? 12 vertices of degree 7. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 26–36, 2003 相似文献
103.
Andrzej Dabrowski Erich Robens Peter Klobes Klaus Meyer Przemyslaw Podkocielny 《Particle & Particle Systems Characterization》2003,20(5):311-322
Since a comprehensive survey published in 1999 [1] much work was done in standardizing measuring methods to characterize the surface geometry of dispersed and/or porous solids and to certify reference materials. The present paper is an extension of a short communication [2]. It gives a survey on existing standards and reports on new drafts and proposals. 相似文献
104.
Surface free energy of a solid surface gives a direct measure of intermolecular interactions at interfaces and has a strong influence on adsorption and adhesion behaviour. However few data are available for the surface free energies of electroless Ni–P based composition coatings. In this paper, the electroless Ni–P, Ni–P-surfactant, Ni–Cu–P, Ni–P–PTFE and Ni–Cu–P–PTFE composite coatings were prepared under various coating conditions. The chemical compositions, surface morphology and thickness of the coatings were measured using an energy dispersive X-ray microanalysis (EDX), a scanning electron microscope (SEM) and a digital micrometer respectively. The contact angles of water, diiodomethane and ethylene glycol on the coatings were measured automatically using dataphysics OCA-20 contact angle analyser. The surface free energy of the coatings and their components (e.g. dispersion, polar or acid/base portions) were calculated using various methods. The experimental results showed that the incorporation of surfactant or PTFE particles into Ni–P matrixes has a significant influence on the surface free energy of the coatings, while the incorporation of copper into Ni–P matrixes has no significant influence on the surface free energy of the coatings. 相似文献
105.
106.
Akhlesh Lakhtakia 《Optik》2004,115(4):151-158
107.
利用相干渡越辐射(CTR)测量短和超短电子束团长度是国际上束测领域新发展的频域测量技术.文中理论分析和数值计算了北京自由电子激光装置的皮秒级的射频电子束团序列产生的CTR,当辐射波长在长于束长(4ps)时,渡越辐射发生相干增强效应;与非相干渡越辐射相比,当λ≥2πσz时,增强的倍数约等于束团中粒子的数目(108);CTR从亚毫米波到毫米波段呈宽带连续谱特性;渡越辐射能量主要集中在轴线附近,宏脉冲辐射能量高达几毫焦.设计采用偏振型束团长度测量系统,利用CTR自相关技术,实验测量该束团序列的纵向长度,并藉助傅里叶变换光谱法,推求束团电子分布. 相似文献
108.
109.
TiC reinforced composite coating on γ-TiAl alloy was successfully fabricated by laser surface alloying with carbon. The fine TiC reinforcing phase had a gradient distribution in the coating, and its growth morphology of TiC in laser surface alloyed coating was in unique faceted platelet-like. The composite coating exhibited high hardness and excellent high-temperature sliding wear resistance. 相似文献
110.
§ 1 IntroductionInthispaperwediscusstheglobalclassicalsolutionofamultidimensionalquasistationaryproblem .Theproblemcomesfromthediscussionofagrowthmodelofselfmaintainingprotocell(see [1— 3])inmultidimensionalcase .Theprotocellcanbevisualizedashavingaporousst… 相似文献