全文获取类型
收费全文 | 11039篇 |
免费 | 2539篇 |
国内免费 | 1829篇 |
专业分类
化学 | 6319篇 |
晶体学 | 681篇 |
力学 | 1090篇 |
综合类 | 96篇 |
数学 | 279篇 |
物理学 | 6942篇 |
出版年
2024年 | 12篇 |
2023年 | 57篇 |
2022年 | 253篇 |
2021年 | 241篇 |
2020年 | 278篇 |
2019年 | 243篇 |
2018年 | 261篇 |
2017年 | 392篇 |
2016年 | 501篇 |
2015年 | 465篇 |
2014年 | 537篇 |
2013年 | 959篇 |
2012年 | 800篇 |
2011年 | 904篇 |
2010年 | 770篇 |
2009年 | 873篇 |
2008年 | 793篇 |
2007年 | 890篇 |
2006年 | 892篇 |
2005年 | 717篇 |
2004年 | 667篇 |
2003年 | 543篇 |
2002年 | 479篇 |
2001年 | 385篇 |
2000年 | 391篇 |
1999年 | 320篇 |
1998年 | 285篇 |
1997年 | 286篇 |
1996年 | 218篇 |
1995年 | 200篇 |
1994年 | 170篇 |
1993年 | 113篇 |
1992年 | 136篇 |
1991年 | 92篇 |
1990年 | 79篇 |
1989年 | 43篇 |
1988年 | 43篇 |
1987年 | 35篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1975年 | 2篇 |
1970年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Polydiphenylsilylenemethylene (PDPhSM) thin films, which are difficult to fabricate by conventional methods because of their insolubility and high melting point, have been synthesized by using laser-ablated metal nanoparticles for the thermal ring-opening polymerization of 1,1,3,3-tetraphenyl-1,3-disilacyclobutane (TPDC) in this paper. TPDC was first evaporated on silicon substrates and then exposed to metal (Pt, Cu and Ag) nanoparticles deposition by laser ablation prior to heat treatment. The catalytic activity of Pt, Cu and Ag nanoparticles has been studied. The results showed that the mean diameter of Pt nanoparticles was the smallest, Cu nanoparticles the moderate and Ag nanoparticles the biggest, while the polymerization efficiency for Pt nanoparticles was the highest, Cu nanoparticles the moderate and Ag nanoparticles the lowest. In addition, the penetration behaviours of Pt, Cu and Ag nanoparticles into the TPDC monomer films during laser ablation were different due to the particle size or the chemical interaction between metal nanoparticles and TPDC molecules. 相似文献
992.
This paper reports the formation and properties of nano-composite pyroelectric thin films. They consist of pyroelectric triglycine sulfate (TGS) single-crystal nano-rods grown inside a highly dense array of alumina pores (about 65 nm diameter and density of 1011 cm−2). The nucleation and growth of the TGS single crystals are obtained by precipitation from a supersaturated aqueous solution. Nucleation is preferred only at the bottom of the pores due to a tight control of temperature, composition and pore diameter. Growth of single crystals with preferred crystallographic orientation is obtained with the aid of an applied electric field. Various crystallographic orientations (1 0 0) (−1 1 0) (−1 2 0) are obtained separately as a single preferred orientation by changing the amplitude of the electric field during crystal growth. The films exhibit ferroelectric behavior. 相似文献
993.
通过实验测量和理论分析, 从载流子动力学角度研究了用于脉冲辐射探测的CVD金刚石薄膜探测器的适用结构、电荷收集效率和时间响应性能. 结果表明, CVD金刚石薄膜可以制成均匀型结构的探测器; 薄膜中的缺陷会降低探测器的电荷收集效率, 探测器的电荷收集效率随场强增大而增大直至饱和. 已研制的CVD金刚石探测器电荷收集时间可达719ps, 在2.5V/μm场强下达到饱和, 电荷收集效率
达60.5%; 晶格散射是影响探测器时间响应的主要因素, 选用大晶粒甚至单晶金刚石薄膜可以提高探测器时间响应. 相似文献
994.
V.A. Kheraj C.J. Panchal P.K. Patel B.M. Arora T.K. Sharma 《Optics & Laser Technology》2007,39(7):1395-1399
The optical output power of a laser diode can be enhanced by anti-reflection (AR) and high-reflection (HR) facet coatings, respectively, at the front and back facet. AR and HR coatings also serve the purpose of protection and passivation of laser diode facets. In this work, we have designed and optimized a single layer λ/4 thick Al2O3 film for the AR coating and a stack of λ/4 thick Al2O3/λ/4 thick Si bi-layers for the HR coating for highly strained InGaAs quantum-well edge emitting broad area (BA) laser diodes. Effect of the front and back facet reflectivities on output power of the laser diodes has been studied. The light output versus injected current (L–I characteristics) measurements were carried out on selected devices before and after the facet coatings. We have also carried out the numerical simulation and analysis of L–I characteristics for this particular diode structure. The experimental results have been compared and verified with the numerical simulation. 相似文献
995.
在ns激光辐照光学薄膜温度分布的基础上,利用最大剪应力理论建立了光学薄膜发生迎光剥落的理论模型,得到了发生损伤相应的应力分布和膜层剥落半径与入射激光能量关系.通过数值分析,验证了理论模型与实验结果基本保持一致,膜层临界损伤阈值与实验结论在数量级上保持一致;剥落半径与入射能量关系曲线与实验结果基本吻合.指出薄膜的损伤形态与其附着力强度有着密切关系,只有当附着力强度小于某一定值(~9.4×10^4N/cm^2)时,才会发生剥落. 相似文献
996.
Yu. Zorenko V. Gorbenko T. Zorenko O. Sidletskiy A. Fedorov P. Bilski A. Twardak 《固体物理学:研究快报》2015,9(8):489-493
We report for the first time the optimized content and excellent scintillation properties of single crystalline film (SCF) scintillators of multicomponent Gd3–xLux Al5–yGay O12:Ce garnet compounds grown by liquid phase epitaxy (LPE) method. The Gd1.5Lu1.5Al2.75Ga2.25O12:Ce and Gd3Al2.75–2Ga2.25–3O12:Ce SCF show the light yield (LY) comparable with that of high‐quality bulk crystal analogues of these garnets but faster scintillation decay and very low thermoluminescence in the above room temperature range. To our knowledge, these SCF possess the highest LY values ever obtained in LPE grown garnet SCF scintillators exceeding by at least 1.5–1.6 times the values previously reported for SCF scintillators.
997.
998.
999.
采用同时具有三角函数良好逼近特性和小波多分辨率与局部特性的Hermite插值型三角小波,基于二维张量积三角小波,推导了求解各种不同边界条件下的矩形弹性薄板的弯曲、振动和屈曲问题的统一列式,同时给出了两种提高计算精度的方法一升阶法和多分辨率法。数值算例表明,三角小波法求解弹性薄板的弯曲、振动和屈曲问题时,能方便地处理各类边界条件,计算效果良好;自振特性分析更具优势,升阶法和多分辨率法能有效地提高分析精度。 相似文献
1000.
E. F. Skelton A. W. Webb S. B. Qadri E. R. Carpenter Jr. M. Z. Harford P. Lubitz 《高压研究》2013,33(1-6):914-916
Abstract The objectives of this work are two fold: (1) to study the effect of using oxygen-acetylene flame grown synthetic diamond as seed crystals for the high pressure-high temperature conversion of graphite into diamond and (2) to demonstrate the ability to produce small crystallites of diamond by a simple, electron beam evaporation technique. In each case, the production of diamond from graphite was confirmed. 相似文献