全文获取类型
收费全文 | 35985篇 |
免费 | 6512篇 |
国内免费 | 5401篇 |
专业分类
化学 | 27462篇 |
晶体学 | 586篇 |
力学 | 1899篇 |
综合类 | 413篇 |
数学 | 3965篇 |
物理学 | 13573篇 |
出版年
2024年 | 138篇 |
2023年 | 769篇 |
2022年 | 1388篇 |
2021年 | 1543篇 |
2020年 | 1608篇 |
2019年 | 1651篇 |
2018年 | 1373篇 |
2017年 | 1379篇 |
2016年 | 1789篇 |
2015年 | 1952篇 |
2014年 | 2360篇 |
2013年 | 2862篇 |
2012年 | 3430篇 |
2011年 | 3435篇 |
2010年 | 2562篇 |
2009年 | 2479篇 |
2008年 | 2635篇 |
2007年 | 2348篇 |
2006年 | 2186篇 |
2005年 | 1734篇 |
2004年 | 1277篇 |
2003年 | 987篇 |
2002年 | 951篇 |
2001年 | 802篇 |
2000年 | 712篇 |
1999年 | 592篇 |
1998年 | 448篇 |
1997年 | 381篇 |
1996年 | 329篇 |
1995年 | 300篇 |
1994年 | 272篇 |
1993年 | 210篇 |
1992年 | 179篇 |
1991年 | 153篇 |
1990年 | 139篇 |
1989年 | 108篇 |
1988年 | 87篇 |
1987年 | 69篇 |
1986年 | 79篇 |
1985年 | 64篇 |
1984年 | 29篇 |
1983年 | 21篇 |
1982年 | 21篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 4篇 |
1971年 | 6篇 |
1957年 | 6篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Ding-kang WANG~ Yan ZHANG Key Laboratory of Mathematics Mechanization Academy of Mathematics Systems Science Chinese Academy of Sciences Beijing China 《中国科学A辑(英文版)》2007,50(10):1441-1450
We present an algorithm to decompose a polynomial system into a finite set of normal ascending sets such that the set of the zeros of the polynomial system is the union of the sets of the regular zeros of the normal ascending sets.If the polynomial system is zero dimensional,the set of the zeros of the polynomials is the union of the sets of the zeros of the normal ascending sets. 相似文献
72.
The dendrite growth process of transparent NaBi(WO4)2 with small prandtl and high melting point was studied by using the in-situ observation system. According to the dynamic images and detailed information, there are two kinds of restriction effect on
the dendrite growth, the competition between arms and branches and the convection in the melt. The dendrite growth rate was
time dependent, and the rate of arm growth reached the maximum 5.8 mm/s in the diffusive-advective region and rapidly decreased
in the diffusive-convective region. The growth rate of branch had the same change trends as the arm’s. Based on the EPMA-EDS
data of solidification structure of quenched NaBi(WO4)2 melt, it was found that there were component differences from stoichiometric concentration in the melt near the interface
during the growth process.
Supported by the National Natural Science Foundation of China (Grant No. 50331040) and the Innovation Funds from Shanghai
Institute of Ceramics, Chinese Academy of Sciences (Grant No. SCX0623) 相似文献
73.
通过两个积分 (一个是不定积分 ,一个是定积分 )及一个极限 ,说明如何灵活使用积分法解决积分问题 ,方法灵活、巧妙 ,适用范围广 . 相似文献
74.
该项目研究内容以压力管道安全保障为中心,在管道危险源辨识与安全状况等级评价、无损检测和结构完整性评估技术三个方面取得了突破性进展。突破了安全状况等级定量评价、薄壁和大曲率管道焊缝缺陷检测、复杂管系统结构完整性评估等技术难题,首次提出在用压力管道安全保障五大环节的全过程技术方法,系统建立了压力管道安全检测与评价方法体系,在压力管道事故预防技术领域实现了跨跃式发展。 相似文献
75.
76.
Yan Guo 《纯数学与应用数学通讯》2007,60(2):291-293
The original article to which this erratum refers was published in Communications on Pure and Applied Mathematics Comm Pure Appl Math(2006)59(5) 626 . 相似文献
77.
Thin films of oxide materials are playing a growing role as critical elements in optoelectronic devices and nanoscale devices. In this work, thin films of some typical oxides such as WO3, Ga2O3 and SrTiO3 were investigated. We present measurements of those films, using various optical techniques like photoconductivity transients over a wide time range and photo-Hall measurements. Analysis of the photo-Hall and photoconductivity data permits the determination of the contribution to the photoconductivity made by the carrier mobility and concentration. A model for dispersive carrier transport was proposed to explain the relaxation of the photoconductivity in oxide thin films. In addition, photoluminescence characterization was used to study microstructures and energy band in oxide thin films. The broad emission from oxide host, consisting of several band peaks, was likely due to a recombination process with several possible paths. The dependence of the luminescent intensity on the annealing atmosphere was associated with the presence of oxygen vacancies. It is suggested that our optical analysis efforts have improved the understanding of oxide thin films, and this should lead to the necessary advancements in a variety of devices. 相似文献
78.
基于完全信息博弈理论,阐述了寡头垄断市场的排污收费古诺模型.建立了具有政府宏观调控机制的博弈模型,并对调控效果进行了分析. 相似文献
79.
在研究排队网络的文献中,G-网络(即推广的排队网络)最近受到了国际学者广泛的关注,它的研究在一定程度上丰富了排队网络的内容.正因为有很多学者投入到此项研究中,新的结果是层出不穷的.本文简短地介绍G-网络近年来的发展. 相似文献
80.
X.P. Hu X. Wang Z. Yan H.X. Li J.L. He S.N. Zhu 《Applied physics. B, Lasers and optics》2007,86(2):265-268
High power red light was generated from a periodically-poled stoichiometric LiTaO3 (PPSLT) by single-pass frequency doubling of a diode-side-pumped, Q-switched Nd:YAG laser at 1319 nm. An average power of
2.4 W of the 660 nm red light was obtained at the fundamental power of ∼5.4 W with the conversion efficiency up to 44.4% and
with low fluctuation down to 2%. The high efficiency and stability at the red output indicate that it is a practical method
to construct a reliable compact red laser.
PACS 42.70.Mp; 42.79.Nv; 42.55.Xi 相似文献