全文获取类型
收费全文 | 26969篇 |
免费 | 4143篇 |
国内免费 | 3219篇 |
专业分类
化学 | 17999篇 |
晶体学 | 250篇 |
力学 | 1155篇 |
综合类 | 397篇 |
数学 | 5818篇 |
物理学 | 8712篇 |
出版年
2024年 | 53篇 |
2023年 | 258篇 |
2022年 | 1197篇 |
2021年 | 1092篇 |
2020年 | 1100篇 |
2019年 | 852篇 |
2018年 | 754篇 |
2017年 | 876篇 |
2016年 | 1144篇 |
2015年 | 988篇 |
2014年 | 1377篇 |
2013年 | 2202篇 |
2012年 | 1552篇 |
2011年 | 1532篇 |
2010年 | 1338篇 |
2009年 | 1549篇 |
2008年 | 1734篇 |
2007年 | 1689篇 |
2006年 | 1519篇 |
2005年 | 1429篇 |
2004年 | 1285篇 |
2003年 | 1214篇 |
2002年 | 980篇 |
2001年 | 805篇 |
2000年 | 801篇 |
1999年 | 729篇 |
1998年 | 689篇 |
1997年 | 525篇 |
1996年 | 448篇 |
1995年 | 407篇 |
1994年 | 384篇 |
1993年 | 241篇 |
1992年 | 246篇 |
1991年 | 161篇 |
1990年 | 135篇 |
1989年 | 148篇 |
1988年 | 121篇 |
1987年 | 101篇 |
1986年 | 83篇 |
1985年 | 116篇 |
1984年 | 74篇 |
1983年 | 42篇 |
1982年 | 60篇 |
1981年 | 45篇 |
1980年 | 44篇 |
1979年 | 42篇 |
1978年 | 43篇 |
1977年 | 26篇 |
1976年 | 25篇 |
1973年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Ralf Jäger Anatolij I. Saprykin J. Sabine Becker Hans -Joachim Dietze José A. C. Broekaert 《Mikrochimica acta》1997,125(1-4):41-44
The analytical capabilities of a high-resolution mass spectrometer in combination with a 13.56 MHz glow discharge ion source for the analysis of semiconducting materials (silicon carbide and gallium arsenide) were studied. It was shown that single positively charged ions of sample material have about 10 eV higher average energy than the ions of the discharge and residual gas. Therefore effective energy separation of the ions of analyte from the ions of the discharge and residual gas was achieved by adjusting the ion transfer optics (breadth and position of energy slit), which improves the analytical capabilities of the developed method.Some analytical applications are presented to illustrate the performance of r.f. GDMS for the bulk analysis of semiconducting materials. The results of the trace element analysis of gallium arsenide and silicon carbide samples are compared with data of independent methods (LIMS, ICP-AES, SIMS).Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthdayOn leave from the Institute of Inorganic Chemistry, 630090 Novosibirsk, Russia 相似文献
102.
103.
In this paper, a construction of optimal constant composition codes is developed, and used to derive some series of new optimal
constant composition codes meeting the upper bound given by [13]. 相似文献
104.
105.
引入了随机环境中双移民生灭过程的概念,定义了过程的模态指示函数,在此基础上研究了其转移矩阵的平稳分布,给出了平稳分布众数的位置与模态指示函数之间的关系.研究了平稳分布的众数与边界关系. 相似文献
106.
当s∈ R,0,〈q, p〈∈∞,0,〈β≤∞且 max{-n/q,-nδ2/qδ1}〈a时,定义了加权Herz—type Triebel-Lizorkin空间kq^q,pF^s β(R^n,ω1,ω2)和Kq^a,pF^sβ(R^n,ω1,ω2),并给出这些空间的一些特征及在这些空间上的Hard—Littlewood极大算子不等式. 相似文献
107.
Longlan Cui Hong Xu Ping He Keiko Sumitomo Yoshinori Yamaguchi Hongchen Gu 《Journal of polymer science. Part A, Polymer chemistry》2007,45(22):5285-5295
A hybrid emulsion polymerization was formulated for synthesizing Fe3O4/polystyrene composite latex. This system, containing binary droplets that are magnetic (Mag)‐droplets with a diameter of 100–200 nm and styrene (St)‐droplets with a diameter of 3–4 μm, was obtained by mixing Mag‐miniemulsion and St‐macroemulsion. With extremely low surfactants concentration (?critical micelle concentration, CMC), the nucleated loci are selectively controlled in the Mag‐droplets, as the result of smaller droplet size and larger surface ratio. Both water‐soluble potassium persulfate (KPS) and oil‐soluble 2,2′‐azobis(2‐isobutyronitrile) was adopted to initiate the polymerization. In the presence of KPS, magnetic polystyrene latices with particles size of 60–200 nm, narrow size distribution, and high magnetite content (86 wt % measured by TGA) were attained successfully. The synthesized magnetic Fe3O4/polystyrene latices assembled into well‐ordered hexagonal structure in the surface of a carbon supported copper grid. The influence of various parameters on various aspects of the as‐synthesized Fe3O4/polystyrene was investigated in detail: type of initiator on composite morphology, feed ratio of Mag‐miniemulsion and St‐macroemulsion on magnetite content, and hydrophobic agent or amount of surfactant on size and size distribution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5285–5295, 2007 相似文献
108.
一个改进的Hardy-Hilbert不等式 总被引:1,自引:1,他引:0
通过建立权系数的不等式,得到一个改进的Hardy-Hilbert不等式. 相似文献
109.
一个推广的Hardy-Hilbert型不等式及其逆式 总被引:1,自引:0,他引:1
本文引入单参数λ及应用Beta函数,给一个Hardy-Hilbert型不等式以具有最佳常数因子的推广,作为应用,给出了它的逆向形式. 相似文献
110.
Tensile impact experiments of EC8.0−24×7 glass fiber bundles at different low temperaturesT(14°C, −40°C and −10°C) and strain rates ɛ were carried out, and complete stress-strain curves were obtained. Within the range
of the experiment temperatures and strain rates, it is found that the initial modulusE, the ultimate strength σmax and the unstable strain ɛ
b
of the glass fiber bundles all increase with ɛ at an identicalT. At an identical ɛ, with the decrease ofT, E and σmax increase; but ɛ
b
increases when 10°C>T>−40°C and decreases when −40°C>T>−100°C. The strain-rate- and temperature-dependent bimodal Weibull statistical constitutive theory was adopted for the statistical
analysis of the experimental results, and the Weibull parameters of single fiber were obtained. The results show that the
bimodal Weibull distribution function is suitable to represent the strength distribution of the glass fiber at low temperature
and different strain rates. The differences in the mechanical properties between EC8.0−24×7 and EC5.5−12 ×14 glass fiber bundles
were also discussed.
Project supported by the National Natural Science Foundation of China (No. 19772058). 相似文献