全文获取类型
收费全文 | 42176篇 |
免费 | 4510篇 |
国内免费 | 3918篇 |
专业分类
化学 | 21067篇 |
晶体学 | 363篇 |
力学 | 1431篇 |
综合类 | 235篇 |
数学 | 3544篇 |
物理学 | 9345篇 |
综合类 | 14619篇 |
出版年
2024年 | 133篇 |
2023年 | 567篇 |
2022年 | 999篇 |
2021年 | 1106篇 |
2020年 | 1093篇 |
2019年 | 1050篇 |
2018年 | 938篇 |
2017年 | 947篇 |
2016年 | 1344篇 |
2015年 | 1488篇 |
2014年 | 1907篇 |
2013年 | 2494篇 |
2012年 | 2895篇 |
2011年 | 3190篇 |
2010年 | 2412篇 |
2009年 | 2431篇 |
2008年 | 2659篇 |
2007年 | 2550篇 |
2006年 | 2229篇 |
2005年 | 1963篇 |
2004年 | 1557篇 |
2003年 | 1250篇 |
2002年 | 1315篇 |
2001年 | 1140篇 |
2000年 | 967篇 |
1999年 | 1076篇 |
1998年 | 966篇 |
1997年 | 921篇 |
1996年 | 912篇 |
1995年 | 840篇 |
1994年 | 759篇 |
1993年 | 660篇 |
1992年 | 596篇 |
1991年 | 547篇 |
1990年 | 479篇 |
1989年 | 408篇 |
1988年 | 365篇 |
1987年 | 269篇 |
1986年 | 213篇 |
1985年 | 199篇 |
1984年 | 111篇 |
1983年 | 76篇 |
1982年 | 77篇 |
1981年 | 56篇 |
1980年 | 52篇 |
1979年 | 59篇 |
1978年 | 42篇 |
1976年 | 38篇 |
1974年 | 41篇 |
1973年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
国内外交通安全管理之比较 总被引:1,自引:0,他引:1
文章通过对欧美、日本等发达国家在道路交通安全宣传教育、事故紧急救援、管理人员严格公正执法、事故损害赔偿归责等方面和我国的交通安全管理情况进行比较分析,试提出我国目前在这些方面存在的问题以及应对措施。 相似文献
22.
设函数f(w)为凸区域D内的单叶解析函数,对于2≤n≤8和所有w∈D,本文得到估计式|f(n)(w)/f'(w)|的精确上界.这个结果推广了一些已知的结论. 相似文献
23.
24.
The structural evolution in amorphous silicon and germanium thin films has been investigated by high-resolution transmission electron microscopy (HRTEM) in conjunction with autocorrelation function (ACF) analysis. The results established that the structure of as-deposited semiconductor films is of a high density of nanocrystallites embedded in the amorphous matrix. In addition, from ACF analysis, the structure of a-Ge is more ordered than that of a-Si. The density of embedded nanocrystallites in amorphous films was found to diminish with annealing temperature first, then to increase. The conclusions also corroborate well with the results of diminished medium-range order in annealed amorphous films determined previously by a variable coherence microscopy method. 相似文献
25.
26.
利用DA算法实现大规模FIR滤波器 总被引:3,自引:0,他引:3
分布式算法是一种广泛地应用在可编程逻辑序列(FPCA)和ASIC设计中计算乘积和的算法。DA算法的处理速度仅与输入的位宽有关,对于大规模乘积和的运算,其计算速度有着明显的优势。当输入位宽过大时,可以将DA算法改进成并串结构以获得更快的处理速度。该文对在FPCA中利用DA算法实现大规模FIR滤波器,提出了具体的实现方案。 相似文献
27.
28.
Resistivity-temperature characteristics of sol gel YBa2Cu3Oy samples synthesized in flowing oxygen atmosphere
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The relationship of resistivity versus synthesizing temperature of sol gel YBa_2Cu_3O_y samples was studied when prepared under flowing oxygen conditions. A set of high-temperature ρ-T curves was obtained for the whole process. After the sample finished the test measuring, its resistivity was ρ_{300}=9.83×10^{-3 }Ω·cm at room temperature. The ρ-T curve also showed that the orthorhombic-tetragonal phase transformation of sol-gel YBa_2Cu_3O_y sample occurred at 581℃ for the sample in the rising temperature process, but at 613℃ in the cooling process, lower than that of the samples made by using the conventional powder metallurgy methods. 相似文献
29.
Random copolymers of poly{(methacrylamide)-co-(vinyl trimethoxysilane)} and poly{(methacrylic acid)-co-(vinyl trimethoxysilane)} were synthesized via a free radical polymerization reaction. Acid catalyzed sol-gel process of tetraethylorthosilicate (TEOS) with aforementioned polymers in the presence of methyl xanthine class of alkaloid like caffeine resulted in the formation of highly transparent monoliths. Solvent extraction of the template leaves behind the recognition sites intact with high selectivity towards the print molecule. The ionic and non-specific adsorptions, which are considered to be the main disadvantages of the molecularly imprinted polymers (MIP), are prevented to a considerable extent by the end capping of surface silanol groups. The template binding efficiencies of MIP were determined by HPLC analysis. 相似文献
30.
The concept and application of phase-space reconstructions are reviewed. Fractional derivatives are then proposed for the purpose of reconstructing dynamics from a single observed time history. A procedure is presented in which the fractional derivatives of time series data are obtained in the frequency domain. The method is applied to the Lorenz system. The ability of the method to unfold the data is assessed by the method of global false nearest neighbors. The reconstructed data is used to compute recurrences and correlation dimensions. The reconstruction is compared to the commonly used method of delays in order to assess the choice of reconstruction parameters, and also the quality of results. 相似文献