全文获取类型
收费全文 | 14991篇 |
免费 | 695篇 |
国内免费 | 232篇 |
专业分类
化学 | 9454篇 |
晶体学 | 126篇 |
力学 | 544篇 |
综合类 | 25篇 |
数学 | 2486篇 |
物理学 | 3283篇 |
出版年
2023年 | 114篇 |
2022年 | 279篇 |
2021年 | 309篇 |
2020年 | 326篇 |
2019年 | 336篇 |
2018年 | 324篇 |
2017年 | 294篇 |
2016年 | 462篇 |
2015年 | 463篇 |
2014年 | 491篇 |
2013年 | 972篇 |
2012年 | 998篇 |
2011年 | 1081篇 |
2010年 | 667篇 |
2009年 | 588篇 |
2008年 | 808篇 |
2007年 | 739篇 |
2006年 | 713篇 |
2005年 | 644篇 |
2004年 | 528篇 |
2003年 | 498篇 |
2002年 | 410篇 |
2001年 | 291篇 |
2000年 | 250篇 |
1999年 | 199篇 |
1998年 | 139篇 |
1997年 | 124篇 |
1996年 | 139篇 |
1995年 | 105篇 |
1994年 | 149篇 |
1993年 | 112篇 |
1992年 | 123篇 |
1991年 | 127篇 |
1990年 | 119篇 |
1989年 | 98篇 |
1988年 | 92篇 |
1987年 | 80篇 |
1986年 | 71篇 |
1985年 | 115篇 |
1984年 | 134篇 |
1983年 | 75篇 |
1982年 | 115篇 |
1981年 | 94篇 |
1980年 | 103篇 |
1979年 | 88篇 |
1978年 | 94篇 |
1977年 | 103篇 |
1976年 | 82篇 |
1975年 | 74篇 |
1973年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Mejía Hugo Fernando Giraldo Jiménez-Piqué Emilio Valdés Matías Procaccini Raúl Pellice Sergio 《Journal of Solid State Electrochemistry》2020,24(10):2451-2460
Journal of Solid State Electrochemistry - A novel material was developed using sol-gel chemistry and an environmental-friendly grafting process of clay nanoparticles. In a previous work of our... 相似文献
12.
13.
Jiatian Chen Le Yang Ying Li Qinghua Hou Lanlan Li Peng Jin 《International journal of quantum chemistry》2019,119(16):e25961
Inorganic planar ring-shape molecules with 4n + 2 π electrons are always the focus of experimental synthesis and theoretical research due to their potential aromaticity and stability. In this work, the whole series of five-membered heterocycle monoanions X nY5-n− (X, Y = group 15 elements; n = 1-4) were thoroughly investigated by means of density functional theory calculations. They all have large formation energies and HOMO-LUMO gap energies, suggesting the potential thermodynamic and kinetic stability. Their aromaticities are comparable to that of typical aromatic hydrocarbons. Their thermal stabilities were firmly established by the ab initio molecular dynamics simulations. As most of them are predicted for the first time, their various spectra were simulated for experimental characterization. Furthermore, we demonstrate that these five-membered cyclic anions can be employed as η5-ligand to construct novel all-inorganic metallocenes, which may serve as the building blocks of low-dimensional nanomaterials. 相似文献
14.
An N. Le Ruiqi Liang Prof. Dr. Mingjiang Zhong 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(35):8177-8189
Mixed-graft block copolymers (mGBCPs) consist of two or more types of polymeric side chains grafted on a linear backbone in a random, alternating, or pseudo-alternating sequence. They can phase-separate with the backbone serving as the interface of the blocks, and the side chains dominate their self-assembly behavior. mGBCPs are an accessible polymer architecture for exploring the idea of encoding polymer properties through the macromolecular architecture, as there are two distinct structural components that can be tuned: the backbone and the side chains. In this Concept article, the current literature on the synthesis of mGBCPs is reviewed, and the advantages and disadvantages of each synthetic method are noted. The self-assembly of mGBCPs is also discussed where possible. Finally, directions for future research on mGBCP synthesis and self-assembly are suggested. 相似文献
15.
16.
17.
In this study, stoichiometric protonation constants of L-tyrosine, L-cysteine, L-tryptophane, L-lysine, and L-histidine, and
their methyl and ethyl esters in water and ethanol–water mixtures of 30, 50, and 70% ethanol (v/v), were determined potentiometrically
using a combined pH electrode system calibrated as the concentration of hydrogen ion. Titrations were performed at 25∘C and the ionic strength of the medium was maintained at 0.10 mol⋅L−1 using sodium chloride. Protonation constants were calculated by using the BEST computer program. The effect of solvent composition
on the protonation constants is discussed. The log10 K2 values of esters generally decreased with increasing ethanol content. However, the log10 K1 values of the esters of L-tyrosine, L-cysteine, and L-tryptophane were found to increase with increasing ethanol content
in contrast those of L-lysine and L-histidine esters. 相似文献
18.
19.
20.
P Vincent A BrioudeC Journet S RabasteS.T Purcell J Le BrusqJ.C Plenet 《Journal of Non》2002,311(2):130-137
We report here the successful inclusion of carbon nanotubes (CNs) into a TiO2 matrix prepared by a sol-gel method. The presence of CNs in the sol-gel matrix and the structure of the film were analyzed principally by transmission electron microscopy. Complementary information about the behavior of embedded carbon nanotubes versus heat treatment and ion irradiation were obtained by X-ray photoelectron spectroscopy. The elaboration of an inorganic matrix containing embedded carbon nanotubes leads to a new nanocomposite. The possible applications of this nanocomposite are discussed. 相似文献