全文获取类型
收费全文 | 1172篇 |
免费 | 29篇 |
国内免费 | 139篇 |
专业分类
化学 | 589篇 |
晶体学 | 13篇 |
力学 | 57篇 |
综合类 | 5篇 |
数学 | 473篇 |
物理学 | 203篇 |
出版年
2025年 | 2篇 |
2024年 | 3篇 |
2023年 | 21篇 |
2022年 | 17篇 |
2021年 | 13篇 |
2020年 | 25篇 |
2019年 | 15篇 |
2018年 | 24篇 |
2017年 | 22篇 |
2016年 | 26篇 |
2015年 | 16篇 |
2014年 | 39篇 |
2013年 | 86篇 |
2012年 | 72篇 |
2011年 | 63篇 |
2010年 | 56篇 |
2009年 | 58篇 |
2008年 | 68篇 |
2007年 | 59篇 |
2006年 | 62篇 |
2005年 | 53篇 |
2004年 | 51篇 |
2003年 | 35篇 |
2002年 | 34篇 |
2001年 | 43篇 |
2000年 | 39篇 |
1999年 | 43篇 |
1998年 | 25篇 |
1997年 | 28篇 |
1996年 | 35篇 |
1995年 | 38篇 |
1994年 | 27篇 |
1993年 | 27篇 |
1992年 | 20篇 |
1991年 | 12篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 2篇 |
排序方式: 共有1340条查询结果,搜索用时 0 毫秒
111.
利用Ket-Bra纠缠态方法,求解了原子与热库相互作用系统中的密度矩阵主方程,得到了密度矩阵的演化表达式.考虑三个二能级原子独立与热库相互作用的情况,利用负本征值度量三体纠缠,研究了系统中原子间的三体纠缠特性.采用数值计算方法,讨论了热库平均光子数和原子自发辐射率对原子间三体纠缠特性的影响.研究结果表明:随原子自发辐射率和热库平均光子数的增大,原子间的三体纠缠衰减加快. 相似文献
112.
微色谱柱分离—FAAS法测定镀铬液中铁、铜、锌 总被引:5,自引:0,他引:5
本文研究了减压条件下微孔色谱柱分离富集镀铬液中杂质无素铁、铜、锌的柱性能,确定了最佳富集条件,在近中性介质中,以H^ 型732强酸性阳离子交换树脂于φ3×70mm微孔色谱柱中富集镀铬液中铁、铜、锌,与铬(Ⅵ)分离,以蒸馏水为淋洗液,被吸附的离子用4.5mol/L硝酸洗脱后用火焰原子吸收光谱法测定,方法简便、快速,灵敏度高,标准加入回收率在98%-104%之间,用于镀铬液中铁、铜、锌的测定,结果令人满意。 相似文献
113.
应用不对称2DNOESHY实验方法研究了顺铂配合物Cis-Pt (NH3)2(Guo)2Cl2的水溶液中的构象,表明鸟苷同铂配合后其糖环构象发生明显的变化。 相似文献
114.
Jacob Palme 《BIT Numerical Mathematics》1972,12(4):534-542
Many programming languages include the ability to divide large programs into smaller segments, which are compiled separately. When a small modification is made to a large program, then the affected segment only has to be re-compiled.This paper discusses how high-level languages like Algol 68, Algol W or Simula 67 can incorporate part-compilation in a usable, secure and efficient way. 相似文献
115.
Kai Xu Zhenchang Tang Yan Zhang Wanshu Li Haiou Li Lihui Wang Liming Liu Honghang Wang Feng Chi Xiaowen Zhang 《Current Applied Physics》2019,19(10):1076-1081
Germanium dioxide (GeO2) aqueous solutions are facilely prepared and the corresponding anode buffer layers (ABLs) with solution process are demonstrated. Atomic force microscopy, X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy measurements show that solution-processed GeO2 behaves superior film morphology and enhanced work function. Using GeO2 as ABL of organic light-emitting diodes (OLEDs), the visible device with tris(8-hydroxy-quinolinato)aluminium as emitter gives maximum luminous efficiency of 6.5 cd/A and power efficiency of 3.5 lm/W, the ultraviolet device with 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole as emitter exhibits short-wavelength emission with peak of 376 nm, full-width at half-maximum of 42 nm, maximum radiance of 3.36 mW/cm2 and external quantum efficiency of 1.5%. The performances are almost comparable to the counterparts with poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) as ABL. The current, impedance, phase and capacitance as a function of voltage characteristics elucidate that the GeO2 ABL formed from appropriate concentration of GeO2 aqueous solution favors hole injection enhancement and accordingly promoting device performance. 相似文献
116.
Visible and NIR luminescence of nanocrystalline β-Ga2O3:Er prepared by solution combustion synthesis
In this paper we report on facile solution combustion synthesis of erbium doped β-Ga2O3 with urea as fuel. The product was characterized using powder X-ray diffraction and transmission electron microscopy (TEM). X-ray diffraction and TEM showed that the material is nanostructured. Luminescence properties of β-Ga2O3:Er are studied with excitation in near infrared (Nd:YAG laser at 1064 nm) and visible (argon laser at 514.5 nm). A strong NIR emission of Er3+ in the window of minimal optical loss in silica based optical fibers, due to the 4I13/2→4I15/2 transition at 1.55 μm has been observed. Codoping with Yb3+ significantly increases the intensity of that important emission. 相似文献
117.
《Optimization》2012,61(4):293-316
The paper develops sufficient conditions for controllability and necessary conditions in different forms of the maximum principle for extremal solutions of discrete inclusions. The objective function is assumed to be locally lipschitzian only 相似文献
118.
119.
The plane problem of an elliptically reinforced circular hole in an anisotropic plate or laminate 总被引:11,自引:0,他引:11
Summary Within the scope of linear elasticity, the in-plane problem of an anisotropic plate or laminate with a circular hole and
an elliptical hole reinforcement is considered. Arbitrary anisotropic elastic stiffnesses are allowed for the base plate and
the reinforcement material, and for the reinforcement there is no restriction for its elliptical shape and size. The analysis
of the problem is performed by the complex potential method with appropriately chosen series representations inside and outside
the reinforcement region. The derived closed-form solution provides all resultant in-plane stresses and deformations within
and around the hole reinforcement with little computational effort and at high accuracy. The determined solution allows a
proper and effective assessment of hole reinforcements for many technical applications.
Received 26 June 2000; accepted for publication 26 September 2000 相似文献
120.
Vagn Askegaard 《Experimental Mechanics》1995,35(4):315-321
A normal stress cell and a shear stress cell have been designed and tested under very varied conditions including permanent
strain. Results pooled from nine different tests with the cells embedded in cohesionless materials (sand and wheat) showed
that the coefficient of variation of the normal stress-cell sensitivity was 0.04, while it was 0.10 for the shear cell. The
agreement between predicted and measured sensitivity was considered to be good for the normal stress cell and reasonably good
for the shear stress cell.
The shear cell showed a systematic dependence, within acceptable limits, of the total stress state in the surrounding material.
A qualitative explanation of this phenomenon is given.
Paper was presented at the SEM VI International Congress on Experimental Mechanics held in Portland, OR in June 6–10, 1988. 相似文献