全文获取类型
收费全文 | 47276篇 |
免费 | 9881篇 |
国内免费 | 17839篇 |
专业分类
化学 | 33874篇 |
晶体学 | 2275篇 |
力学 | 3902篇 |
综合类 | 2024篇 |
数学 | 7858篇 |
物理学 | 25063篇 |
出版年
2024年 | 132篇 |
2023年 | 490篇 |
2022年 | 1827篇 |
2021年 | 1750篇 |
2020年 | 1663篇 |
2019年 | 1617篇 |
2018年 | 1498篇 |
2017年 | 2387篇 |
2016年 | 1594篇 |
2015年 | 2476篇 |
2014年 | 2993篇 |
2013年 | 3977篇 |
2012年 | 3830篇 |
2011年 | 4046篇 |
2010年 | 4255篇 |
2009年 | 4405篇 |
2008年 | 5012篇 |
2007年 | 4383篇 |
2006年 | 4354篇 |
2005年 | 3814篇 |
2004年 | 2896篇 |
2003年 | 2083篇 |
2002年 | 2062篇 |
2001年 | 2124篇 |
2000年 | 2216篇 |
1999年 | 1253篇 |
1998年 | 663篇 |
1997年 | 529篇 |
1996年 | 487篇 |
1995年 | 433篇 |
1994年 | 513篇 |
1993年 | 476篇 |
1992年 | 405篇 |
1991年 | 284篇 |
1990年 | 283篇 |
1989年 | 318篇 |
1988年 | 257篇 |
1987年 | 206篇 |
1986年 | 159篇 |
1985年 | 124篇 |
1984年 | 120篇 |
1983年 | 134篇 |
1982年 | 113篇 |
1981年 | 97篇 |
1980年 | 70篇 |
1979年 | 63篇 |
1978年 | 24篇 |
1977年 | 16篇 |
1971年 | 16篇 |
1959年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
132.
133.
Banach空间二阶非线性脉冲微分-积分方程的极值解 总被引:1,自引:0,他引:1
通过建立一个新的比较定理研究了B anach空间二阶非线性混合型脉冲微分-积分方程初值问题的极值解,所得结果推广和改进了现有文献的主要结果. 相似文献
134.
135.
Effects of Processing Parameters on Microstructure and Properties of Nanoscale ZrC/ZrB2 Multilayered Coatings 下载免费PDF全文
ZrC/ZrB2 multilayered coatings with bilayer periods of 3.5-40nm are synthesized by rf magnetron sputtering. Analyses of x-ray diffraction, scanning electron microscopy and nanoindentation indicate that multilayered coatings possess much higher hardness and greater fracture resistance than monolithic ZrC and ZrB2 coatings. A maximum hardness (41.TCPa) and a critical fracture load (73.7mN) are observed in the multilayer with A = 32 nm deposited at the substrate bias -40 V. Higher residual stress built in the ZrC layer can be released by periodic insertion of ZrB2 into the ZrC layer. A clear multilayered structure with mixed ZrB2(001), ZrB2 (002) and ZrC (111) orientations should be responsible for the enhanced mechanical properties. 相似文献
136.
137.
An economical magnetocardiogram (MCG) system is built in our laboratory. It mainly consists of a MCG data acquisition stage equipped with two high-To superconducting quantum interference device (SQUID) magnetometers, a data processing stage with digital filtering and a one-layer μ-metal magnetically shielded room in conjunction with a high-Tc SQUID based active compensation. Experimental results show that a noise level of pico-tesla in MCG profiles, which is necessary for clinical applications, may be achieved with the system. Moreover, stable and convenient operations of the system are demonstrated with simulating MCG measurements. 相似文献
138.
Electroluminescence of a Multi-Layered Organic Light-Emitting Diode Utilizing Trans-4-[p-[N-methyl-N-(hydroxymethyl)amino]styryl]-N-Methylphridinium Tetraphenylborate as the Active Layer 下载免费PDF全文
Employing an organic dye salt of trans-4-[p-[N-methyl-N-(hydroxymethyl)amino]styryl]-N-methylphridinium tetra\-phenylborate (ASPT) as the active layer, 8-hydrocyquinoline aluminium (Alq3) as the electron transporting layer and N,N’-diphenyl-N,N’-bis(3-methylphenyl)-[1,1’-biphenyl]-4,4’-diamine (TPD) as the hole transporting layer, respectively, we fabricate a multi-layered organic light-emitting diode and observe the colour tunable electroluminescence (EL). The dependence of the EL spectra on the applied voltage is investigated in detail, and the recombination mechanism is discussed by considering the variation of the hole-electron recombination region. 相似文献
139.
Double-Humped Transverse Density Profile in Two-Dimensional Chute Flow with Rough Sidewalls 下载免费PDF全文
We study a two-dimensional granular rapid flow with rough sidewalls stuck with the same size discs by molecular dynamics simulation. A transient state of the double-humped density profile in the flowing process has been found, which appears and moves as travelling wave and is the same as the phenomena in the recent experiments [Acta Phys. Sin. 53 (2004) 3389 (in Chinese)]. Our simulation shows that the rough sidewalls play an important role in the converting momentum of boundary discs from the vertical direction to the horizontal one through particle collisions to form this profile and the good elasticity of discs ensures this effect. The appearance of the double-humped profile may be a precursor, which determines if the whole flow will be far repulsed from the boundary and become dilute eventually. 相似文献
140.
高抗冲聚丙烯序列结构的综合表征 总被引:3,自引:0,他引:3
用高分辨^13C NMR、FTIR等手段获得了高抗冲聚丙烯的组成和序列分布等链结构方面的信息。用DSC、WAXD等方法研究了它们的结晶行为、熔融转变及晶体结构,多种方法相结合有效地表征了高抗冲聚丙烯的序列结构。 相似文献