全文获取类型
收费全文 | 110654篇 |
免费 | 6066篇 |
国内免费 | 5102篇 |
专业分类
化学 | 47805篇 |
晶体学 | 1267篇 |
力学 | 8966篇 |
综合类 | 412篇 |
数学 | 35564篇 |
物理学 | 27808篇 |
出版年
2024年 | 95篇 |
2023年 | 575篇 |
2022年 | 1094篇 |
2021年 | 1170篇 |
2020年 | 1256篇 |
2019年 | 1288篇 |
2018年 | 11327篇 |
2017年 | 11077篇 |
2016年 | 7513篇 |
2015年 | 2498篇 |
2014年 | 2228篇 |
2013年 | 2844篇 |
2012年 | 6677篇 |
2011年 | 13442篇 |
2010年 | 7656篇 |
2009年 | 8070篇 |
2008年 | 8769篇 |
2007年 | 10705篇 |
2006年 | 2249篇 |
2005年 | 2930篇 |
2004年 | 3005篇 |
2003年 | 3112篇 |
2002年 | 2234篇 |
2001年 | 1337篇 |
2000年 | 1132篇 |
1999年 | 896篇 |
1998年 | 774篇 |
1997年 | 598篇 |
1996年 | 654篇 |
1995年 | 538篇 |
1994年 | 457篇 |
1993年 | 412篇 |
1992年 | 347篇 |
1991年 | 312篇 |
1990年 | 268篇 |
1989年 | 247篇 |
1988年 | 172篇 |
1987年 | 167篇 |
1986年 | 151篇 |
1985年 | 139篇 |
1984年 | 90篇 |
1983年 | 84篇 |
1982年 | 80篇 |
1981年 | 64篇 |
1980年 | 64篇 |
1979年 | 55篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
Gang Wang Xiulin Zhu Zhenping Cheng Jian Zhu 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):2912-2921
A series of (di)picolinic acids and their derivates are investigated as novel complexing tridentate or bidentate ligands in the iron‐mediated reverse atom transfer radical polymerization of methyl methacrylate in N,N‐dimethylformamide at 100 °C with 2,2′‐azobisisobutyrontrile as an initiator. The polymerization rates and polydispersity indices (1.32–1.8) of the resulting polymers are dependent on the structures of the ligands employed. Different iron complexes may be involved in iron‐mediated reverse atom transfer radical polymerization, depending on the type of acid used. 1H NMR spectroscopy has been used to study the structure of the resulting polymers. Chain‐extension reactions have been performed to further confirm the living nature of this catalytic system. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2912–2921, 2006 相似文献
65.
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
66.
67.
Graham Smith 《The Journal of the Operational Research Society》1989,40(9):761-770
Courses which teach discrete-event simulation are based on many different simulation languages. The requirements for a language to support teaching simulation are discussed. In particular, it is recommended that such languages separate into distinct modules those aspects of simulation which are taught as separate topics. Implementation of the separation is discussed. The SEESIM language, developed as a teaching aid, is described, and examples of its use are given. Straightforward use of SEESIM can be learned quickly, yet the language provides facilities for a staged introduction to advanced concepts of simulation. 相似文献
68.
J Ashenfelter 《Pramana》2002,59(5):713-717
The ESTU began operation in 1988 and achieved the design voltage of 20 MV in 1990. Since that time, improvements to the gas
handling system, negative ion injector, accelerator terminal and control system have greatly increased its capability and
reliability. Today, the ESTU can efficiently produce an extensive assortment of stable ions at wide-ranging energies in support
of low-energy nuclear physics. 相似文献
69.
溴酸钾-亚甲蓝催化光度法测定硝酸盐和亚硝酸盐 总被引:16,自引:1,他引:15
用镉柱将NO-3 还原为NO-2 ,利用在磷酸介质中NO-2 对溴酸钾氧化亚甲蓝这一褪色反应具有强烈的催化作用而建立了同时测定痕量硝酸盐和亚硝酸盐的新方法。本方法简便、快速、灵敏 ,对亚硝酸盐和硝酸盐测定的线性范围分别为 0~ 2 0 0 μg·L-1和 0 0 0 3~ 310 μg·L-1,用于测定各种水样中痕量NO-2 和NO-3 的含量均获得满意结果 相似文献
70.
A pressure sensitive paint (PSP) measurement has been known as a pressure field measurement technique based on the oxygen quenching phenomenon of luminescence of specific luminophores. A PSP measurement was applied for pressure field measurement in a low-solidity circular cascade diffuser of a single-stage transonic centrifugal compressor with 5 in pressure ratio for HFC134a gas. The oxygen concentration was about 500 ppm. Ru (bath-phen) was adsorbed on a silica-gel thinlayer chromatography sheet, and the sheet was pasted onto the side-wall between the cascade vanes. A drastic change in luminescent intensity was recognized during a surge condition. Also the pressure variations based on luminescent intensity agreed well with the pressure fluctuations measured using a semiconductor pressure sensor with high-frequency-response. It was shown that a PSP measurement worked well to investigate the unsteady pressure fields in a circular cascade diffuser of a transonic centrifugal compressor. Moreover, the time response of PSP becomes clear as a problem to be overcome for the present. 相似文献