全文获取类型
收费全文 | 1194篇 |
免费 | 124篇 |
国内免费 | 99篇 |
专业分类
化学 | 788篇 |
晶体学 | 23篇 |
力学 | 57篇 |
综合类 | 4篇 |
数学 | 173篇 |
物理学 | 372篇 |
出版年
2023年 | 17篇 |
2022年 | 30篇 |
2021年 | 34篇 |
2020年 | 28篇 |
2019年 | 34篇 |
2018年 | 36篇 |
2017年 | 30篇 |
2016年 | 39篇 |
2015年 | 48篇 |
2014年 | 70篇 |
2013年 | 94篇 |
2012年 | 92篇 |
2011年 | 100篇 |
2010年 | 65篇 |
2009年 | 44篇 |
2008年 | 57篇 |
2007年 | 61篇 |
2006年 | 63篇 |
2005年 | 45篇 |
2004年 | 51篇 |
2003年 | 29篇 |
2002年 | 26篇 |
2001年 | 25篇 |
2000年 | 25篇 |
1999年 | 19篇 |
1998年 | 11篇 |
1997年 | 18篇 |
1996年 | 15篇 |
1995年 | 17篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 21篇 |
1979年 | 6篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1969年 | 4篇 |
排序方式: 共有1417条查询结果,搜索用时 937 毫秒
81.
Haitao Han Liang Kan Ping Li Guoshuai Zhang Kaiyue Li Wuping Liao Yunling Liu Wei Chen Chunhua T.Hu 《中国科学:化学(英文版)》2021,(3):426-431
Three 4.8 nm isostructural{M72}(M=CoⅡ for CIAC-128,NiⅡ for CIAC-129,FeⅡ for CIAC-130) metal-organic polyhedra(MOPs) are constructed by eighteen M4-p-tert-butylthiacalix[4]arene (M4-TC4A) units bridged via sixteen four-connected 5,5′-(1H-1,2,4-triazole-3,5-diyl) diisophthalic acid (H4TADIPA) linkers.These MOPs are featured with a rarely reported concave coordination cage,which can be simplified as a squeezed double-decker hexagonal prism pressed from the top and bottom hexagonal faces.Furthermore,CIAC-128,CIAC-129 and CIAC-130 are the highest nuclearity discrete clusters of Co,Ni and Fe reported so far.CIAC-128 has higher separation selectivity of C3H8 than CH4 under ambient conditions,and also exhibits separation selectivity for C2H6/CH4,C2H2/CH4,and C2H4/CH4.In addition,CIAC-128 can provide the cavity for the confined synthesis of noble metal nanoclusters such as Pd nanoclusters and the resulting Pd@CIAC-128 hybrids show higher electrocatalytic activity than commercial Pt/C towards hydrogen evolution reaction (HER). 相似文献
82.
铈掺杂对超细LaMnO_(3+λ)催化性能的影响 总被引:1,自引:0,他引:1
以Ce2(CO3)3,La2O3和Mn(NO3)2为原料,用"溶胶-凝胶"法结合"超临界干燥"技术,将铈掺入超细LaMnO3+λ气凝胶中。用TG-DTA,XRD,TEM,FT-IR等手段对样品进行表征;并用"2CO+2NO=2CO2+N2"反应测试铈掺杂对超细LaMnO3+λ催化活性的影响。结果显示:260℃时,镧铈锰气凝胶为疏松、絮状且具有较好分散性的棕色粉末,由大量直径小于10 nm的球形颗粒组成;850℃热处理后,镧铈锰气凝胶为粒径小于20 nm的类球形颗粒,晶相成分为LaMnO3+λ,La2O3和CeO2;铈掺杂增加LaMnO3+λ晶格的氧空缺数量,改善氧化还原催化的气氛条件,提高超细LaMnO3+λ的催化活性。 相似文献
83.
Kai Kang Cheng-you Kan Yi Du De-shan Liu 《高分子科学》2005,(5):479-485
Soap-free poly(methyl methacrylate-ethyl acrylate-methacrylic acid) latex particles with narrow size distribution were synthesized by seeded emulsion polymerization, and the porous particles were created by a stepwise alkali/acid treatment method. Effects of acid treatment conditions on the particle morphology were investigated. Results show that one to three pores were formed inside most of particles after post-treatment. At pH 7.0, when the treatment temperature was lower than 70℃, the size of particles and the volume of pores remained almost unchanged, and these two values increased significantly when the temperature was higher than 70℃. Both the particle size and the pore volume decreased with the increase of initial pH value and treatment time in the acid treatment. As the pH was below 4.0 and the treatment time was longer than 180 min, the particles shrunk in size. 相似文献
84.
85.
86.
J. Kawanaka Y. Takeuchi A. Yoshida S. J. Pearce R. Yasuhara T. Kawashima H. Kan 《Laser Physics》2010,20(5):1079-1084
A MOPA laser system for high pulse energy and high average power has been developed by using a cryogenic Yb:YAG. In the regenerative
amplifier with our original TRAM architecture, the high pulse energies of 6.5 and 1.5 mJ were obtained at the repetition rate
of 200 Hz and 1 kHz, respectively. An optical efficiency was as high as ηo-o = 9.3% with an excellent beam quality of M
2 < 1.1, which ensured that a cryogenic Yb:YAG TRAM had a high thermal strength. The following four pass power amplifier with
a cryogenic Yb:YAG rod showed 140 mJ at 100 Hz. Both a high optical efficiency of ηo-o = 30% and a high slope efficiency of ηs = 44% showed that an efficient laser operation could be realized for a power amplification with both a high pulse energy
and a high average power by using a cryogenic Yb:YAG. 相似文献
87.
Intrinsic self‐initiating thermal ring‐opening polymerization of 1,3‐benzoxazines without the influence of impurities using very high purity crystals
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Lu Han María Laura Salum Kan Zhang Pablo Froimowicz Hatsuo Ishida 《Journal of polymer science. Part A, Polymer chemistry》2017,55(20):3434-3445
A phenol/aniline type monofunctional benzoxazine monomer, PH‐a , is synthesized and highly purified to study the intrinsic thermal ring‐opening polymerization of benzoxazines without the influence of any impurity. The successful synthesis of the monomer and its corresponding chemical structure are confirmed by Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (1H NMR) spectroscopy. Purity of the compound is evaluated through differential scanning calorimetry (DSC) as well as elemental analysis (EA). Moreover, the thermal behavior of benzoxazine monomer toward polymerization is also studied by DSC, indicating that the highly purified benzoxazine monomer actually polymerize upon heating. The results present evidence of an intrinsic tendency for 1,3‐benzoxazines to undergo thermally induced ring‐opening polymerization upon heating only without any impurity participating during the reaction. This reveals that polybenzoxazines can be obtained by both the traditional thermally accelerated (or activated) polymerization, where impurities or purposefully added initiators are involved in the reaction; or, by the classic thermal polymerization, where only heat is enough to initiate the reaction. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3434–3445 相似文献
88.
89.
Shutao Wang Kan Liu Jian Liu Zeta T.‐F. Yu Xiaowen Xu Libo Zhao Tom Lee Eun Kyung Lee Jean Reiss Yi‐Kuen Lee Leland W. K. Chung Jiaoti Huang Matthew Rettig David Seligson Kumaran N. Duraiswamy Clifton K.‐F. Shen Hsian‐Rong Tseng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2011,123(13):2909-2909
90.
Total synthesis of ecteinascidin 743 总被引:1,自引:0,他引:1
Endo A Yanagisawa A Abe M Tohma S Kan T Fukuyama T 《Journal of the American Chemical Society》2002,124(23):6552-6554
The total synthesis of ecteinascidin 743 (1), an extremely potent antitumor agent, has been accomplished. The synthesis features Ugi's 4CC reaction, intramolecular Heck reaction, phenol-aldehyde cyclization, and acid-induced intramolecular sulfide formation. 相似文献