全文获取类型
收费全文 | 6238篇 |
免费 | 676篇 |
国内免费 | 770篇 |
专业分类
化学 | 4129篇 |
晶体学 | 26篇 |
力学 | 348篇 |
综合类 | 66篇 |
数学 | 1689篇 |
物理学 | 1426篇 |
出版年
2024年 | 22篇 |
2023年 | 89篇 |
2022年 | 152篇 |
2021年 | 255篇 |
2020年 | 437篇 |
2019年 | 255篇 |
2018年 | 191篇 |
2017年 | 206篇 |
2016年 | 278篇 |
2015年 | 213篇 |
2014年 | 281篇 |
2013年 | 371篇 |
2012年 | 275篇 |
2011年 | 265篇 |
2010年 | 189篇 |
2009年 | 305篇 |
2008年 | 349篇 |
2007年 | 311篇 |
2006年 | 349篇 |
2005年 | 249篇 |
2004年 | 195篇 |
2003年 | 208篇 |
2002年 | 307篇 |
2001年 | 172篇 |
2000年 | 145篇 |
1999年 | 129篇 |
1998年 | 122篇 |
1997年 | 117篇 |
1996年 | 84篇 |
1995年 | 61篇 |
1994年 | 70篇 |
1993年 | 74篇 |
1992年 | 73篇 |
1991年 | 47篇 |
1990年 | 39篇 |
1989年 | 29篇 |
1988年 | 40篇 |
1987年 | 35篇 |
1985年 | 77篇 |
1984年 | 100篇 |
1983年 | 47篇 |
1982年 | 89篇 |
1981年 | 93篇 |
1980年 | 57篇 |
1979年 | 54篇 |
1978年 | 50篇 |
1977年 | 34篇 |
1976年 | 24篇 |
1974年 | 17篇 |
1973年 | 20篇 |
排序方式: 共有7684条查询结果,搜索用时 343 毫秒
101.
The action of lithium butyl acetylenide in THF causes 4,4-diethyl-1,2-dithiolane to undergo ring-opening to form 2,2-diethyl-4-thia-5-decyne-1-thiol,
which cyclizes to give 2-butyl-6,6-diethyl-5,6-dihydro-1,4-dithiepin by either a homolytic or a nucleophilic mechanism.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 204–206, January, 1997. 相似文献
102.
ZHUANG QuanChao XU JinMei FAN XiaoYong WEI GuoZhen DONG QuanFeng JIANG YanXia HUANG Ling SUN Shigang 《中国科学B辑(英文版)》2007,50(6)
The storage behavior and the first delithiation of LiCoO2 electrode in 1 mol/L LiPF6-EC:DMC:DEC elec- trolyte were investigated by electrochemical impedance spectroscopy (EIS). It has found that, along with the increase of storage time, the thickness of SEI film increases, and some organic carbonate lithium compounds are formed due to spontaneous reactions occurring between the LiCoO2 electrode and the electrolyte. When electrode potential is changed from 3.8 to 3.95 V, the reversible breakdown of the resistive SEI film occurs, which is attributed to the reversible dissolution of the SEI film component. With the increase of electrode potential, the thickness of SEI film increases rapidly above 4.2 V, due to overcharge reactions. The inductive loop observed in impedance spectra of the LiCoO2 electrode in Li/LiCoO2 cells is attributed to the formation of a Li1-xCoO2/LiCoO2 concentration cell. Moreover, it has been demonstrated that the lithium-ion insertion-deinsertion in LiCoO2 hosts can be well described by both Langmuir and Frumkin insertion isotherms, and the symmetry factor of charge transfer has been evaluated at 0.5. 相似文献
103.
Jean-Yves Sanchez Fannie Alloin Cristina Iojoiu 《Journal of fluorine chemistry》2006,127(11):1471-1478
This contribution has been partly adapted from a special lecture intended to commemorate the Nobel prize, awarded one century ago, to Henri Moissan. It, is focused on fluorinated and perfluorinated molecules and macromolecules used in electrochemical energy sources, i.e. storage and conversion of energy. The latter, which figure indisputably among New Energy Technologies, include lithium batteries and fuel cells based on polymeric membranes both of which have tremendous development potential in terms of performances, safety and cost reductions. The advantages inherent in fluorine, in particular its electron-withdrawing effect and the oxidation stability that it provides to the carbon-fluorine bond, make it an asset in the search for new organic molecular and macromolecular anions with extensive delocalization of the negative charge, usable both in lithium batteries and fuel cells. As for fluorinated and perfluorinated macromolecule backbones, they are currently the reference material in fuel cell ionomeric membranes but some of them are also good candidates for use in lithium-ion batteries. This paper, far from being exhaustive, also emphasizes the economic aspects that influence material selection and also govern the future of basic research. 相似文献
104.
It is proven that the canonical Gibbs measure associated with a gas of vortices of intensity ± converges, in the limitN, 0,Nconst, to a Gaussian measure, which is invariant for the two-dimensional Euler equation.On leave from Dipartimento di Matematica Università di Roma Tor Vergata Roma, Italy.On leave from Dipartimento di Matematica Università di Roma La Sapienza, Roma, Italy. 相似文献
105.
106.
The spherical-model limitn of then-vector model in a random field, with either a statistically independent distribution or with long-range correlated random fields, is studied to demonstrate the correctness of the replica method in which then and replica limits limits are interchanged, provided the replica and thermodynamic limits are taken in the right order, in the case of long-range correlated random fields. A scaling form for the two-point correlation function relevant to the first-order phase transition below the lower critical dimensionality of the random system is also obtained. 相似文献
107.
液晶电视由于其优异的显示性能将会越来越受到青睐。本文简要综述了近年来电视用液晶材料的研究进展,归纳总结了这些液晶材料的合成方法及其热性能、介电各向异性、双折射率、粘度等特性。 相似文献
108.
本标准物质系合金钢。主要成份有碳、硅、锰、磷、硫、铬、镍、钼、钒,同时还含有锡、铅、砷、锑、铋等微量元素,每种元素成份都具有良好的线性关系。它可作为量值传递和仲裁分析的依据,同时也可用于校验分析仪器与分析方法的正确性和可靠性。 相似文献
109.
荧光钙探针试剂及其在生物分析中的应用 总被引:2,自引:0,他引:2
本文评论了荧光钙探针试剂合成、性质、结构和生物分析应用方面的进展。各种典型的荧光钙探针试剂均已分别加以讨论。 相似文献
110.
Li_3PO_4包覆LiMn_2O_4正极材料的结构表征和电化学性能 总被引:1,自引:0,他引:1
采用共沉淀法在尖晶石LiMn2O4颗粒表面包覆Li3PO4.XRD、SEM研究结果表明,包覆后的材料仍为尖晶石结构,粒径均匀.电化学性能测试表明,Li3PO4包覆层的存在,减少了正极材料与电解液的直接接触,抑制了高温下电解液对LiMn2O4材料的侵蚀,从而有效改善了高温下材料的循环性能.在40℃时,包覆样品的比容量衰减率都低于未包覆样品,其中包覆1%Li3PO4的样品的初始比容量为110.4mAh/g,50次循环后比容量为84.1mAh/g. 相似文献