全文获取类型
收费全文 | 60854篇 |
免费 | 921篇 |
国内免费 | 304篇 |
专业分类
化学 | 28946篇 |
晶体学 | 1055篇 |
力学 | 3222篇 |
综合类 | 8篇 |
数学 | 4790篇 |
物理学 | 24058篇 |
出版年
2022年 | 550篇 |
2021年 | 491篇 |
2020年 | 469篇 |
2019年 | 476篇 |
2018年 | 589篇 |
2017年 | 517篇 |
2016年 | 930篇 |
2015年 | 660篇 |
2014年 | 1018篇 |
2013年 | 2598篇 |
2012年 | 2451篇 |
2011年 | 3132篇 |
2010年 | 2183篇 |
2009年 | 2241篇 |
2008年 | 2866篇 |
2007年 | 2700篇 |
2006年 | 2576篇 |
2005年 | 2273篇 |
2004年 | 2050篇 |
2003年 | 1827篇 |
2002年 | 1732篇 |
2001年 | 3039篇 |
2000年 | 2176篇 |
1999年 | 1576篇 |
1998年 | 1104篇 |
1997年 | 1077篇 |
1996年 | 902篇 |
1995年 | 790篇 |
1994年 | 717篇 |
1993年 | 645篇 |
1992年 | 971篇 |
1991年 | 964篇 |
1990年 | 871篇 |
1989年 | 765篇 |
1988年 | 750篇 |
1987年 | 809篇 |
1986年 | 671篇 |
1985年 | 905篇 |
1984年 | 860篇 |
1983年 | 589篇 |
1982年 | 594篇 |
1981年 | 561篇 |
1980年 | 525篇 |
1979年 | 646篇 |
1978年 | 682篇 |
1977年 | 686篇 |
1976年 | 593篇 |
1975年 | 497篇 |
1974年 | 537篇 |
1973年 | 469篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
1.
2.
Kinetics and Catalysis - The catalytic properties of a nickel phosphide catalyst supported on silica gel in the reductive amination of carbonyl compounds were studied in a flow reactor using... 相似文献
3.
Yang T. L. Kao C. L. Kuo C. E. Yeh H. C. Li W. J. Li H. T. Chen C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the... 相似文献
4.
Saqib Kamal Arif I. Inamdar Kuan-Ru Chiou Batjargal Sainbileg Muhammad Usman Jenq-Wei Chen Tzuoo-Tsair Luo Michitoshi Hayashi Chen-Hsiung Hung Wen-Feng Liaw Kuang-Lieh Lu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202103905
The dielectric properties of coordination polymers has been a topic of recent interest, but the role of different functional groups on the dielectric properties of these polymers has not yet been fully addressed. Herein, the effects of electron-donating (R=NH2) and electron-withdrawing (R=NO2) groups on the dielectric behavior of such materials were investigated for two thermally stable and guest-free Zn-based coordination polymers, [Zn(L1)(L2)]n ( 1 ) and [Zn(L1)(L3)]n ( 2 ) [L1=2-(2-pyridyl) benzimidazole (Pbim), L2=5-aminoisophthalate (Aip), and L3=5-nitroisophthalate (Nip)]. The results of dielectric studies of 1 revealed that it possesses a high dielectric constant (κ=65.5 at 1 kHz), while compound 2 displayed an even higher dielectric constant (κ=110.3 at 1 kHz). The electron donating and withdrawing effects of the NH2 and NO2 substituents induce changes in the polarity of the polymers, which is due to the inductive effect from the aryl ring for both NO2 and NH2. Theoretical results from density functional theory (DFT) calculations, which also support the experimental findings, show that both compounds have a distinct electronic behavior with diverse wide bandgaps. The significance of the current work is to provide information about the structure-dielectric property relationships. So, this study promises to pave the way for further research on the effects of different functional groups on coordination polymers on their dielectric properties. 相似文献
5.
Kobayashi M. Zhang Y. Ishikawa H. Sun J. Oddershede J. Juul Jensen D. Miura H. 《Experimental Mechanics》2021,61(5):817-828
Experimental Mechanics - The internal strain distribution developing during plastic deformation is important for understanding the mechanical properties of polycrystalline materials. Such... 相似文献
6.
7.
Li Y. Shi W. H. Dong L. M. Xu S. X. Huang H. J. Yin J. R. 《Journal of Applied Spectroscopy》2022,89(3):534-541
Journal of Applied Spectroscopy - Sr3B2O6:Dy3+, Eu3+ single-matrix white-light-emitting materials are prepared using the high-temperature solid-state method. The microstructure, emission spectrum,... 相似文献
8.
Dr. Yulia Y. Enakieva Dr. Anna A. Sinelshchikova Prof. Mikhail S. Grigoriev Prof. Vladimir V. Chernyshev Dr. Konstantin A. Kovalenko Prof. Irina A. Stenina Prof. Andrey B. Yaroslavtsev Prof. Yulia G. Gorbunova Prof. Aslan Y. Tsivadze 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(45):10552-10556
The design of new solid-state proton-conducting materials is a great challenge for chemistry and materials science. Herein, a new anionic porphyrinylphosphonate-based MOF ( IPCE-1Ni ), which involves dimethylammonium (DMA) cations for charge compensation, is reported. As a result of its unique structure, IPCE-1Ni exhibits one of the highest value of the proton conductivity among reported proton-conducting MOF materials based on porphyrins (1.55×10−3 S cm−1 at 75 °C and 80 % relative humidity). 相似文献
9.
10.
Su X. F. Zhang Y. L. Maximov A. L. Zhang K. Xin Q. Feng C. Q. Bai X. F. Wu W. 《Russian Journal of Applied Chemistry》2020,93(1):127-136
Russian Journal of Applied Chemistry - Nanoscale ZSM-5 (AlZ5-D) and Ga-substituted ZSM-5 zeolites ((Al,Ga)Z5-D and GaZ5-D) were synthesized by a green dry-gel conversion strategy. For comparison,... 相似文献