全文获取类型
收费全文 | 12373篇 |
免费 | 2170篇 |
国内免费 | 2676篇 |
专业分类
化学 | 9449篇 |
晶体学 | 231篇 |
力学 | 692篇 |
综合类 | 379篇 |
数学 | 1624篇 |
物理学 | 4844篇 |
出版年
2024年 | 18篇 |
2023年 | 114篇 |
2022年 | 278篇 |
2021年 | 319篇 |
2020年 | 349篇 |
2019年 | 436篇 |
2018年 | 335篇 |
2017年 | 380篇 |
2016年 | 514篇 |
2015年 | 568篇 |
2014年 | 692篇 |
2013年 | 950篇 |
2012年 | 1023篇 |
2011年 | 1125篇 |
2010年 | 1007篇 |
2009年 | 993篇 |
2008年 | 1106篇 |
2007年 | 1042篇 |
2006年 | 963篇 |
2005年 | 816篇 |
2004年 | 701篇 |
2003年 | 607篇 |
2002年 | 580篇 |
2001年 | 485篇 |
2000年 | 388篇 |
1999年 | 276篇 |
1998年 | 192篇 |
1997年 | 138篇 |
1996年 | 135篇 |
1995年 | 103篇 |
1994年 | 96篇 |
1993年 | 81篇 |
1992年 | 70篇 |
1991年 | 61篇 |
1990年 | 51篇 |
1989年 | 35篇 |
1988年 | 35篇 |
1987年 | 36篇 |
1986年 | 28篇 |
1985年 | 22篇 |
1984年 | 12篇 |
1983年 | 18篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1973年 | 3篇 |
1970年 | 3篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
将Abe引入的q q-1对称变形熵应用于玻色子的正则系综,根据最大熵原理和Lagrange乘子法,导出了系统的密度算子,进而在微变形的条件下求出了粒子数算符的期望值及其在高温、低温下的近似值。 相似文献
42.
X. S. Wu Xuehai Wu Yunping Li Zhangde Lu Liangen Gong Ping Zhou Qing Zhang 《Fiber and Integrated Optics》1993,12(1):97-103
Miniature, etching ridge InGaAsP/InP Phase Modulator with highly efficient phase shifting efficiency of 60°/V.mm and 43°/V.mm for TE and TM modes, respectively, and 3 dB bandwidth of 650 MHz at 1.52 μm are reported. It is well suited for integrated opto-electronics. Some functions depending on bandwidth of the devices are discussed. 相似文献
43.
一个包含Smarandache函数的方程 总被引:2,自引:0,他引:2
对于任意正整数n,我们用S(n)表示Smarandache函数,即S(n)=min{m:n|m!}.本文的主要目的是运用初等方法研究方程∑_(d|n)S(d)=n的可解性,并给出它的所有正整数解. 相似文献
44.
高密度氩气的原子间相互作用与状态方程 总被引:5,自引:4,他引:1
本文从高密度气体的原子间相互作用出发进行思考,在修改范德瓦耳方程的基础上,提出了一种新的适用于高密度气体的状态方程,并用以对氩气临界区的等温压缩线进行计算,结果与实验值很符合. 相似文献
45.
46.
47.
Zhishen Mo Lixiao Wang Hongfang Zhang Ping Han Baotong Huang 《Journal of Polymer Science.Polymer Physics》1987,25(9):1829-1837
Wide-angle X-ray scattering from presumed block copolymers of polypropylene (PP) and ethylene-propylene copolymer (EPR), i.e., PP-EPR and PP-EPR-PP, synthesized by sequential polymerization with δ-TiCl3? Et2AlCl, was examined and compared with WAXS of mechanical blends and chain-transfer mixtures of PP and EPR with comparable compositions. The peak at 2θ = 20° for both the copolymers and the mixtures was attributed to the γ modification of PP in EPR. A strong variation in the ratio of diffraction intensities I040/I110 of PP in block copolymers and mixtures was explained in terms of crystallite growth in different directions. Analysis of the patterns and calculation of crystallinity, crystallite size, and lattice parameters led to the conclusion that block structure existed in the prepared copolymers. 相似文献
48.
�� Ƽ������ͨ�������������� 《核聚变与等离子体物理》2006,39(3):265-269
By using Fluent software with the Eulerian multiphase model and Non-equilibrium boiling model, the subcooled flow boiling heat transfers was numerically simulated in the plain upward vertical tubes under the condition of one-side heating. The influences of the different mass flux, inlet temperatures and heat flux on the heat transfer coefficient, the void fraction and heat transfer deterioration were investigated. 相似文献
49.
Design and Fabrication of 1.06 μm Resonant-Cavity Enhanced Reflective Modulator with GaInAs/GaAs Quantum Wells 下载免费PDF全文
A resonant-cavity enhanced reflective optical modulator is designed and fabricated, with three groups of three highly strained InGaAs/GaAs quantum wells in the cavity, for low voltage and high contrast ratio operation. The quantum wells are positioned in antinodes of the optical standing wave. The modulator is grown in a single growth step in an molecular beam epitaxy system, using GaAs/AlAs distributed Bragg reflectors as both the top and bottom mirrors. Results show that the reflection device has a modulation extinction of 3 dB at -4.5 V bias. 相似文献
50.
Li‐Ming Tang Yan‐Guo Li Wei‐Ping Ye Yue‐Sheng Li 《Journal of polymer science. Part A, Polymer chemistry》2006,44(20):5846-5854
Ethylene–propylene copolymerization, using [(Ph)NC(R2)CHC(R1)O]2TiCl2 (R1 = CF3, Ph, or t‐Bu; R2 = CH3 or CF3) titanium complexes activated with modified methylaluminoxane as a cocatalyst, was investigated. High‐molecular‐weight ethylene–propylene copolymers with relatively narrow molecular weight distributions and a broad range of chemical compositions were obtained. Substituents R1 and R2 influenced the copolymerization behavior, including the copolymerization activity, methylene sequence distribution, molecular weight, and polydispersity. With small steric hindrance at R1 and R2, one complex (R1 = CF3; R2 = CH3) displayed high catalytic activity and produced copolymers with high propylene incorporation but low molecular weight. The microstructures of the copolymers were analyzed with 13C NMR to determine the methylene sequence distribution and number‐average sequence lengths of uninterrupted methylene carbons. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5846–5854, 2006 相似文献