全文获取类型
收费全文 | 37170篇 |
免费 | 6616篇 |
国内免费 | 4307篇 |
专业分类
化学 | 25448篇 |
晶体学 | 518篇 |
力学 | 2469篇 |
综合类 | 327篇 |
数学 | 4485篇 |
物理学 | 14846篇 |
出版年
2024年 | 35篇 |
2023年 | 758篇 |
2022年 | 821篇 |
2021年 | 1111篇 |
2020年 | 1475篇 |
2019年 | 1391篇 |
2018年 | 1242篇 |
2017年 | 1157篇 |
2016年 | 1738篇 |
2015年 | 1710篇 |
2014年 | 2091篇 |
2013年 | 2647篇 |
2012年 | 3240篇 |
2011年 | 3436篇 |
2010年 | 2366篇 |
2009年 | 2329篇 |
2008年 | 2541篇 |
2007年 | 2291篇 |
2006年 | 2176篇 |
2005年 | 1700篇 |
2004年 | 1363篇 |
2003年 | 1101篇 |
2002年 | 994篇 |
2001年 | 827篇 |
2000年 | 842篇 |
1999年 | 797篇 |
1998年 | 706篇 |
1997年 | 663篇 |
1996年 | 674篇 |
1995年 | 615篇 |
1994年 | 535篇 |
1993年 | 432篇 |
1992年 | 428篇 |
1991年 | 334篇 |
1990年 | 302篇 |
1989年 | 238篇 |
1988年 | 205篇 |
1987年 | 174篇 |
1986年 | 154篇 |
1985年 | 152篇 |
1984年 | 103篇 |
1983年 | 70篇 |
1982年 | 60篇 |
1981年 | 36篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1977年 | 2篇 |
1971年 | 1篇 |
1959年 | 1篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Guanlin Li Ling Zhao Yicong Luo Youbin Peng Kai Xu Dr. Xiaohong Huo Prof. Dr. Wanbin Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(24):e202200273
Asymmetric desymmetrization has been demonstrated to be a powerful strategy for building stereocenters in asymmetric synthesis. Herein, a Pd/Cu catalyzed asymmetric desymmetrization reaction with a simple geminal dicarboxylate is reported. A wide scope of imino esters bearing an aryl or heteroaromatic group were compatible with this bimetallic catalytic system. The reactions proceeded smoothly, giving the desired products in good yields with high to excellent regio-, diastereo-, and enantioselectivity (up to 20 : 1 branched:linear, >20 : 1 dr, >99 % ee). Notably, the reaction favored branched selectivity, which is unusual for the Pd-catalyzed allylic alkylation reaction. In addition, the standard product could be easily transformed to other valuable molecules such as chiral allylic alcohols, carbamates, and organic boron compounds. Furthermore, DFT calculations were conducted to explain the origin of the branched selectivity. 相似文献
52.
Hanghang Zhou Dr. Ying Luo Dr. Jun Xu Dr. Lidan Deng Prof. Dr. Zheng Wang Prof. Dr. Hong He 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(68):e202202044
Cubic-like CaTaO2N photocatalysts with high crystallinity and uniform particle size were successfully prepared by the flux-assisted nitridation method. The growth of CaTaO2N single crystals under different synthesis conditions was systematically investigated to understand the effects of the crystallinity and optical property on photocatalytic performance of CO2 reduction. Moreover, the modification of CaTaO2N single crystals with core-shell Ni−Ag bicomponent cocatalyst by two-step decoration process gave a 2.4 times higher amount of CO evolution than the deposition of sole Ag cocatalyst, because of the synergistic effects of bicomponent cocatalyst on the interfacial electron transfer and surface catalytic process. This study provides a valuable way to construct high-crystalline photocatalysts with effective bicomponent cocatalyst for visible-light-driven CO2 reduction with H2O. 相似文献
53.
Tianyu Shan Liang Gao Xiaoqian Tong Qinqing Du Zhihang An Huiwen He Prof. Jiaping Lin Prof. Si Chen Prof. Xu Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(52):12098-12104
An amazing phenomenon of the relative magnitude of modulus of two liquid-crystal (LC) gels is found inverted under/above their phase transition temperature TLC-iso, which is further proved to be caused by their diverse morphology flexibility. By testing the polarity of two LCs, gelator POSS-G1-Boc (POSS=polyhedral oligomeric silsesquioxane) was discovered to self-assemble into more flexible structures in a relatively low polar LC, whereas more rigid ones are formed in higher polar LC. Hence, a fitting function to connect morphology flexibility with solvent polarity was established, which can even be generalized to a number of common solvents. Experimental observations and coarse-grained molecular dynamics simulations revealed that solvent polarity mirrors a “Morse code”, with each “code” corresponding to a specific morphology flexibility. 相似文献
54.
Lianghao Song Tiantian Xu Daowei Gao Prof. Xun Hu Prof. Cuncheng Li Prof. Shun Li Prof. Guozhu Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(26):6621-6627
CeO2-based catalysts are widely studied in catalysis fields. Developing one novel synthetic approach to increase the intimate contact between CeO2 and secondary species is of particular importance for enhancing catalytic activities. Herein, an interfacial reaction between metal–organic framework (MOF)-derived carbon and KMnO4 to synthesize CeO2−MnO2, in which carbon is derived from the pyrolysis of Ce-MOFs under an inert atmosphere, is described. The MOF-derived carbon is found to restrain the growth of CeO2 crystallites under a high calcination temperature and, more importantly, intimate contact within CeO2/C is conveyed to CeO2/MnO2 after the interfacial reaction; this is responsible for the high catalytic activity of CeO2−MnO2 towards CO oxidation. 相似文献
55.
Xuan Zhang Xianhe Fang Miao Xu Yibo Lei Zibo Wu Xiangdong Hu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(23):7927-7931
Enantioselective total syntheses of pseudopteroxazole ( 1 ) and ileabethoxazole ( 2 ) are presented. The two original stereocenters were constructed in excellent enantioselectivity and good diastereoselectivity through Carreira's asymmetric dual catalytic allylation, which shows potential for accessing diastereoisomers at C2 and C3 of 1 and 2 . Cationic cyclizations of 13 and 24 demonstrated an effective pathway for the construction of the opposite configurations at C1 in 1 and 2 . Additionally, an approach for the introduction of methyl at C4 is a feasible solution for structural modifications at C4 in 1 and 2 . 相似文献
56.
Ke Xu Evan T. Vickers Longshi Rao Dr. Sarah A. Lindley A'Lester C. Allen Prof. Binbin Luo Prof. Xueming Li Prof. Jin Zhong Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(19):5014-5021
CH3NH3PbBr3 perovskite quantum dots (PQDs) are synthesized by using four different linear alkyl phosphonic acids (PAs) in conjunction with (3-aminopropyl)triethoxysilane (APTES) as capping ligands. The resultant PQDs are characterized by means of XRD, TEM, Raman spectroscopy, FTIR spectroscopy, UV/Vis, photoluminescence (PL), time-resolved PL, and X-ray photoelectron spectroscopy (XPS). PA chain length is shown to control the PQD size (ca. 2.9–4.2 nm) and excitonic absorption band positions (λ=488–525 nm), with shorter chain lengths corresponding to smaller sizes and bluer absorptions. All samples show a high PL quantum yield (ca. 46–83 %) and high PL stability; this is indicative of a low density of band gap trap states and effective surface passivation. Stability is higher for smaller PQDs; this is attributed to better passivation due to better solubility and less steric hindrance of the shorter PA ligands. Based on the FTIR, Raman, and XPS results, it is proposed that Pb2+ and CH3NH3+ surface defects are passivated by R−PO32− or R−PO2(OH)−, whereas Br− surface defects are passivated by R−NH3+ moieties. This study establishes the combination of PA and APTES ligands as a highly effective dual passivation system for the synergistic passivation of multiple surface defects of PQDs through primarily ionic bonding. 相似文献
57.
Wenjing Li Mingchun Lu Eva Zurek Xuedi Xu Lulu Chen Miao Zhang Lili Gao Xin Zhong Jia Li Xiaoming Zhou Wenyan Liu 《Physics letters. A》2019,383(10):1047-1051
Silicon (Si) is one of the most essential elements, as it is indispensable for modern electronic technology. The standard Si structure at ambient conditions is the cubic diamond structure, and it has an indirect band gap, which prevents it from being considered as a next-generation platform for semiconductor technologies. Therefore, the search for new allotropes of silicon has attracted great attention. Herein, first principles swarm-intelligence structure searches coupled with density-functional theory were performed to explore the stable high-pressure phases of silicon-rich lithium containing compounds, LiSix (). The LiSi4 stoichiometry was predicted to be stable, and it was found to assume one of the following space groups, P4/mnc, Cmmm, and C2/m within the pressure range of 0 to 50 GPa. By removing the Li atoms from these compounds, three silicon allotropes were obtained that were metastable at ambient pressures. Our work illustrates how novel silicon allotropes can be predicted using the CALYPSO method. 相似文献
58.
59.
An electromechanical integrated electrostatic harmonic actuator is promising for the miniaturization of electromechanical devices. As the dimensions of the actuator decrease, the effects of the van der Waals force become obvious. In this study, by considering the nonlinearity of electrostatic and van der Waals forces, nonlinear vibration equations of the flexible ring of an electrostatic harmonic actuator are deduced. Using these equations, the nonlinear free vibration and nonlinear forced response of the actuator are investigated. The effects of the van der Waals force on the nonlinear vibration of the flexible ring are analyzed. Results show that these effects of the van der Waals force are relatively obvious under some conditions and should be considered. 相似文献
60.
Xiaoyu Ding Dr. Zhenghui Pan Na Liu Linge Li Xianshu Wang Guoguang Xu Jie Yang Jin Yang Nengsheng Yu Meinan Liu Prof. Wanfei Li Prof. Yuegang Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(15):3775-3780
Flexible lithium/sulfur (Li/S) batteries are promising to meet the emerging power demand for flexible electronic devices. The key challenge for a flexible Li/S battery is to design a cathode with excellent electrochemical performance and mechanical flexibility. In this work, a flexible strap-like Li/S battery based on a S@carbon nanotube/Pt@carbon nanotube hybrid film cathode was designed. It delivers a specific capacity of 1145 mAh g−1 at the first cycle and retains a specific capacity of 822 mAh g−1 after 100 cycles. Moreover, the flexible Li/S battery retains stabile specific capacity and Coulombic efficiency even under severe bending conditions. As a demonstration of practical applications, an LED array is shown stably powered by the flexible Li/S battery under flattened and bent states. We also use the strap-like flexible Li/S battery as a real strap for a watch, which at the same time provides a reliable power supply to the watch. 相似文献