全文获取类型
收费全文 | 90792篇 |
免费 | 16984篇 |
国内免费 | 9166篇 |
专业分类
化学 | 77769篇 |
晶体学 | 1214篇 |
力学 | 4107篇 |
综合类 | 601篇 |
数学 | 8789篇 |
物理学 | 24462篇 |
出版年
2024年 | 175篇 |
2023年 | 1002篇 |
2022年 | 1871篇 |
2021年 | 2091篇 |
2020年 | 3131篇 |
2019年 | 4372篇 |
2018年 | 2775篇 |
2017年 | 2480篇 |
2016年 | 5684篇 |
2015年 | 5958篇 |
2014年 | 6441篇 |
2013年 | 7850篇 |
2012年 | 7726篇 |
2011年 | 7111篇 |
2010年 | 6272篇 |
2009年 | 6277篇 |
2008年 | 6100篇 |
2007年 | 5162篇 |
2006年 | 4746篇 |
2005年 | 4201篇 |
2004年 | 3622篇 |
2003年 | 3111篇 |
2002年 | 3853篇 |
2001年 | 2925篇 |
2000年 | 2640篇 |
1999年 | 1607篇 |
1998年 | 1081篇 |
1997年 | 924篇 |
1996年 | 899篇 |
1995年 | 781篇 |
1994年 | 696篇 |
1993年 | 564篇 |
1992年 | 523篇 |
1991年 | 414篇 |
1990年 | 387篇 |
1989年 | 302篇 |
1988年 | 252篇 |
1987年 | 206篇 |
1986年 | 184篇 |
1985年 | 180篇 |
1984年 | 115篇 |
1983年 | 80篇 |
1982年 | 65篇 |
1981年 | 43篇 |
1980年 | 21篇 |
1979年 | 13篇 |
1977年 | 5篇 |
1959年 | 2篇 |
1957年 | 3篇 |
1936年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
用相位调制方法测量光盘盘基应力双折射的精度分析 总被引:4,自引:2,他引:2
偏振相位调制方法是测量微小双折射的一种高精度检测方法。本文系统全面地分析了以PMCSA结构形式测量光盘盘基应力双折射的相位调制方法中,由各种误差源造成的对测试结果的影响。 相似文献
93.
94.
95.
96.
97.
Przemyslaw Bogacki Stanley Weinstein Yuesheng Xu 《Advances in Computational Mathematics》1997,7(4):593-621
We consider the choice of a functional to measure the distance between two parametric curves. We identify properties of such
a distance functional that are important for geometric design. Several popular definitions of distance are examined, and new
functionals are presented which satisfy the desired properties.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
98.
一类非线性单调型方程的区域分裂法 总被引:1,自引:0,他引:1
本文考虑了一类非线性单调问题的加性Schwgrz交替法和异步平行算法,并得到了在能量模意义下的收敛性结果,最后还讨论了格式的有限元离散。 相似文献
99.
To incorporate an acceptor type polythiophene segment onto a supramolecular block copolymer for potential light harvesting applications, effective synthetic routes for the end‐functionalized and acceptor‐substituted polythiophenes are critical. The Ullmann coupling reaction can be utilized to obtain electron‐deficient polythiophenes and to attach terminal thiophene units that carry functional groups. In this article, the reactions involving a 2,5‐dibromothiophene monomer containing an electron‐withdrawing fluorinated ester and 5‐bromo‐2‐thiophenecarboxaldehyde (the end‐capper) were studied in detail. It was found that the Ullmann coupling reaction of the dibromide is very fast (completed in a few minutes) and the terminal bromine group does not survive long under the reaction condition. These findings lead to the development of an effective procedure for aldehyde end‐capping of electron‐deficient polythiophenes. Polymers with molecular weights around 4000 Da are routinely obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 41–47, 2007 相似文献
100.
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