全文获取类型
收费全文 | 787篇 |
免费 | 86篇 |
国内免费 | 68篇 |
专业分类
化学 | 557篇 |
晶体学 | 15篇 |
力学 | 40篇 |
综合类 | 6篇 |
数学 | 128篇 |
物理学 | 195篇 |
出版年
2024年 | 1篇 |
2023年 | 13篇 |
2022年 | 14篇 |
2021年 | 24篇 |
2020年 | 28篇 |
2019年 | 20篇 |
2018年 | 10篇 |
2017年 | 15篇 |
2016年 | 22篇 |
2015年 | 47篇 |
2014年 | 39篇 |
2013年 | 44篇 |
2012年 | 55篇 |
2011年 | 71篇 |
2010年 | 47篇 |
2009年 | 41篇 |
2008年 | 44篇 |
2007年 | 38篇 |
2006年 | 31篇 |
2005年 | 47篇 |
2004年 | 32篇 |
2003年 | 34篇 |
2002年 | 22篇 |
2001年 | 22篇 |
2000年 | 19篇 |
1999年 | 15篇 |
1998年 | 15篇 |
1997年 | 15篇 |
1996年 | 15篇 |
1995年 | 20篇 |
1994年 | 13篇 |
1993年 | 9篇 |
1992年 | 14篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1976年 | 2篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1957年 | 2篇 |
1945年 | 1篇 |
排序方式: 共有941条查询结果,搜索用时 31 毫秒
71.
Wen-Hua Zhang Xiu-Bao Wei Ping-Ning Jin Jun-Feng Kou Guang Yang 《Transition Metal Chemistry》2011,36(5):459-463
Reactions of 3(5)-methyl-5(3)-phenyl-1H-1,2,4-triazole (3-Me-5-Ph-tzH) with AgNO3 in the absence/presence of NH3 yield a mononuclear [Ag(3-Me-5-Ph-tzH)2]NO3·3H2O (1) and a polymeric [Ag(3-Me-5-Ph-tz)]n (2), respectively. Two structurally different infinite chains, however, with the same formula of AgC9H8N3—one is double-decked and the other single zigzag—coexist in 1:1 ratio in the crystal of 2. As far as we know, 2 is the first binary silver(I) complex based on an asymmetric triazole and represents a rare case of two supramolecular isomers
coexisting in the same crystal. 相似文献
72.
从理想混合物的定义出发,用数学推导的方法建立了它的微观模型。推导得到的两个推论可作为进一步改进非电解质溶液理论的出发点。 相似文献
73.
74.
Cao‐Yuan Niu Xian‐Fu Zheng Ling‐Ling Bai Xiao‐Ling Wu Chun‐Hong Kou 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(9):m305-m307
This study presents new coordinating modes of a Schiff base with three coordinating groups and an interesting two‐dimensional framework based on two types of constructing units. In the title compound, {[Ag(C14H10N4O)]ClO4}n, the AgI ion is coordinated by three N atoms and one O atom from three different N′‐(4‐cyanobenzylidene)isonicotinohydrazide (L) ligands, forming a primary distorted square‐planar coordination geometry. Two ligands each bridge two metal centres through one carbonitrile N atom in a monodentate mode and the hydrazide N and O atoms in a bidentate mode to form a small centrosymmetric (2+2)‐Ag2L2 ring as a principal constructing unit. The pyridyl N atoms from four ligands in four of these small rings coordinate to Ag atoms in adjacent rings to form a large hexanuclear silver grid. A two‐dimensional framework of rectangular grids is constructed from these small rings and large grids. Two perchlorate anions are located in each large grid and are bound to the grid by N—H...O hydrogen bonding. Crosslinking between the layers is achieved through long Ag...O interactions between the perchlorate anions and Ag atoms in adjacent layers. 相似文献
75.
Ai-Li Cui Guo-Xing Feng Ya-Fan Zhao Hui-Zhong Kou Hong Li Guang-Hua Zhu Ho-Soon Hwang Hee-Chang Oh Young-Jin Kwon Doo-Chul Lee 《Electrochemistry communications》2009,11(2):409-412
Electrochemical oxidation of graphite anode in deionized water at galvanostatic mode is investigated. It is found that mellitic acid and graphite oxide colloid (>20 nm) are coexisted as main products, as identified by XRD and TEM, FTIR and XPS. They can be separated successfully through several procedures. A few amounts of graphene and graphene rolls are also appeared as co-products. 相似文献
76.
对ISO/IEC17025-1999和ISO/IEC指南25-1990进行了比较,分析了ISO/IEC17025-1999的显著变化,提出了由ISO/IEC指南25-1990质量体系向ISO/IEC17025-1999质量体系过渡的措施。 相似文献
77.
In this paper, we present some variants of Cauchy's method for solving non-linear equations. Analysis of convergence shows that the methods have fourth-order convergence. Per iteration the new methods cost almost the same as Cauchy's method. Numerical results show that the methods can compete with Cauchy's method. 相似文献
78.
This paper introduces a novel niching scheme called the q-nearest neighbors replacement (q-NNR) method in the framework of the steady-state GAs (SSGAs) for solving binary multimodal optimization problems. A detailed
comparison of the main niching approaches are presented first. The niching paradigm and difference of the selection-recombination
genetic algorithms (GAs) and the recombination-replacement SSGAs are discussed. Then the q-NNR is developed by adopting special replacement policies based on the SSGAs; a Boltzmann scheme for dynamically sizing the
nearest neighbors set is designed to achieve a speed-up and control the proportion of individuals adapted to different niches.
Finally, experiments are carried out on a set of test functions characterized by deception, epistasis, symmetry and multimodality.
The results are satisfactory and illustrate the effectivity and efficiency of the proposed niching method. 相似文献
79.
80.
Conventional inorganic semiconductors are best known for their superior physical properties and chemical robustness, and their widespread use in optoelectronic devices. However, implementation of these materials in many other applications has been hindered by their poor solubility and/or solution-processability, a longstanding drawback that is largely responsible for issues such as high cost. While recent progress on hybrid perovskites, an important class of inorganic–organic hybrid materials, has shed light on the development of high-performance solution processable semiconductors, they rely heavily on toxic metals and generally suffer from framework instability. To address these issues, a new group of hybrid semiconductors based on anionic copper(i) halide and cationic organic ligands has been developed. These compounds are noted as All-In-One (AIO) structures as they consist of covalently bonded anionic CuX inorganic modules that form both coordinate and ionic bonds with cationic organic ligands. Studies demonstrate that framework stability and solution processibility of these materials are greatly enhanced as a result of such bonds. In the perspective, we highlight the development of this newly emerged type of materials including their crystal structures, chemical and physical properties and possible applications. The untapped potential that the AIO approach can offer for other hybrid families is also discussed.This Perspective features the newly emerged AIO-type Cu(i)X-based hybrid semiconductors and showcases their structural diversity, solution-processability, framework stability, important photophysical properties and related potential applications. 相似文献