全文获取类型
收费全文 | 5580篇 |
免费 | 1009篇 |
国内免费 | 556篇 |
专业分类
化学 | 3631篇 |
晶体学 | 53篇 |
力学 | 245篇 |
综合类 | 30篇 |
数学 | 735篇 |
物理学 | 2451篇 |
出版年
2024年 | 11篇 |
2023年 | 126篇 |
2022年 | 158篇 |
2021年 | 194篇 |
2020年 | 223篇 |
2019年 | 189篇 |
2018年 | 178篇 |
2017年 | 170篇 |
2016年 | 282篇 |
2015年 | 236篇 |
2014年 | 303篇 |
2013年 | 371篇 |
2012年 | 472篇 |
2011年 | 546篇 |
2010年 | 331篇 |
2009年 | 328篇 |
2008年 | 355篇 |
2007年 | 327篇 |
2006年 | 313篇 |
2005年 | 260篇 |
2004年 | 193篇 |
2003年 | 168篇 |
2002年 | 193篇 |
2001年 | 150篇 |
2000年 | 124篇 |
1999年 | 155篇 |
1998年 | 127篇 |
1997年 | 108篇 |
1996年 | 105篇 |
1995年 | 71篇 |
1994年 | 53篇 |
1993年 | 52篇 |
1992年 | 47篇 |
1991年 | 59篇 |
1990年 | 31篇 |
1989年 | 27篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1986年 | 22篇 |
1985年 | 17篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有7145条查询结果,搜索用时 343 毫秒
201.
Copper Causes Regiospecific Formation of C4F8‐Containing Six‐Membered Rings and their Defluorination/Aromatization to C4F4‐Containing Rings in Triphenylene/1,4‐C4F8I2 Reactions
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kerry C. Rippy Dr. Eric V. Bukovsky Dr. Tyler T. Clikeman Dr. Yu‐Sheng Chen Dr. Gao‐Lei Hou Dr. Xue‐Bin Wang Dr. Alexey A. Popov Dr. Olga V. Boltalina Prof. Steven H. Strauss 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(3):874-877
The presence of Cu in reactions of triphenylene (TRPH) and 1,4‐C4F8I2 at 360 °C led to regiospecific substitution of TRPH ortho C(β) atoms to form C4F8‐containing rings, completely suppressing substitution on C(α) atoms. In addition, Cu caused selective reductive‐defluorination/aromatization (RD/A) to form C4F4‐containing aromatic rings. Without Cu, the reactions of TRPH and 1,4‐C4F8I2 were not regiospecific and no RD/A was observed. These results, supported by DFT calculations, are the first examples of Cu‐promoted 1) regiospecific perfluoroannulation, 2) preparative C?F activation, and 3) RD/A. HPLC‐purified products were characterized by X‐ray diffraction, low‐temperature PES, and 1H/19F NMR. 相似文献
202.
A novel flavone, penimethavone A (1), possessing a rare unique methyl group at ring-B, was isolated from the fungus Penicillium chrysogenum cultured from a gorgonian Carijoa sp. collected from the South China Sea. The structure was elucidated by extensive spectroscopic analysis and by comparison with related known compound. Compound 1 showed selective and moderate cytotoxicity against cervical cancer (HeLa) and rhabdomyosarcoma cell lines with IC50 values of 8.41 and 8.18 μM, respectively. 相似文献
203.
204.
205.
Back Cover: Improved Electrochromic Performance of Poly(3,4‐ethylenedioxythiophene) by Incorporating a Three‐Dimensionally Ordered Macroporous Structure (Chem. Asian J. 20/2016)
下载免费PDF全文
![点击此处可从《化学:亚洲杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
206.
207.
In this paper, we construct a second order algorithm based on the spectral deferred correction method for the time-dependent magnetohydrodynamics flows at a low magnetic Reynolds number. We present a complete theoretical analysis to prove that this algorithm is unconditionally stable, consistent and second order accuracy. Finally, two numerical examples are given to illustrate the convergence and effectiveness of our algorithm. 相似文献
208.
209.
Colloidal gold nanoparticles were prepared through in situ reduction in the presence of water-soluble star homopolymer with β-cyclodextrin core and poly[2-(dimethylamino) ethyl methacrylate] arms (star PDMAEMA-β-CD) at ambient temperature. In this process, star PDMAEMA-β-CD acted as both reducing agent and stabilizing agent for gold nanoparticles. More importantly, the optical properties and the morphology of star-PDMAEMA-β-CD-stabilized colloidal gold nanoparticles were sensitive to the solution pH due to structural changes of the polymer. Different assemblies can be formed by tuning the pH of the medium. Fourier transform infrared (FT-IR), UV-Vis absorption spectroscopy, transmission electron microscopy (TEM), dynamic laser light scattering (DLS) and X-ray diffraction (XRD) were used to characterize the synthetic gold nanoparticles and the pH-controlled assembly of gold nanoparticles. 相似文献
210.