全文获取类型
收费全文 | 14990篇 |
免费 | 3116篇 |
国内免费 | 2290篇 |
专业分类
化学 | 7727篇 |
晶体学 | 176篇 |
力学 | 1636篇 |
综合类 | 157篇 |
数学 | 1132篇 |
物理学 | 9568篇 |
出版年
2024年 | 17篇 |
2023年 | 146篇 |
2022年 | 414篇 |
2021年 | 514篇 |
2020年 | 578篇 |
2019年 | 486篇 |
2018年 | 480篇 |
2017年 | 627篇 |
2016年 | 714篇 |
2015年 | 567篇 |
2014年 | 858篇 |
2013年 | 1312篇 |
2012年 | 986篇 |
2011年 | 1059篇 |
2010年 | 907篇 |
2009年 | 1011篇 |
2008年 | 1050篇 |
2007年 | 942篇 |
2006年 | 987篇 |
2005年 | 783篇 |
2004年 | 768篇 |
2003年 | 666篇 |
2002年 | 567篇 |
2001年 | 543篇 |
2000年 | 449篇 |
1999年 | 319篇 |
1998年 | 379篇 |
1997年 | 297篇 |
1996年 | 281篇 |
1995年 | 252篇 |
1994年 | 233篇 |
1993年 | 199篇 |
1992年 | 181篇 |
1991年 | 134篇 |
1990年 | 114篇 |
1989年 | 95篇 |
1988年 | 109篇 |
1987年 | 72篇 |
1986年 | 54篇 |
1985年 | 40篇 |
1984年 | 46篇 |
1983年 | 17篇 |
1982年 | 34篇 |
1981年 | 20篇 |
1980年 | 13篇 |
1979年 | 11篇 |
1978年 | 18篇 |
1977年 | 9篇 |
1976年 | 6篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Cover Picture: Water Repellency in Hydrophobic Nanocapsules—Molecular View on Dewetting (Chem. Eur. J. 22/2014) 下载免费PDF全文
92.
Synthesis of conjugated polymers possessing diketopyrrolopyrrole units bearing phenyl,pyridyl, and thiazolyl groups by direct arylation polycondensation: Effects of aromatic groups in DPP on physical properties 下载免费PDF全文
Junpei Kuwabara Naoto Takase Takeshi Yasuda Takaki Kanbara 《Journal of polymer science. Part A, Polymer chemistry》2016,54(15):2337-2345
Conjugated polymers containing phenyl‐, pyridyl‐, and thiazolyl‐flanked diketopyrrolopyrrole (DPP) were synthesized by direct arylation polycondensation of 3,4‐ethylenedioxythiophene derivatives and dibrominated DPP‐based monomers, in order to probe the effects of the aromatic groups in the DPP units on the absorption property, energy level, and crystallinity. A polymer possessing thiazolyl‐flanked DPP units was found to display long‐wavelength absorption properties and higher crystallinity than the polymers bearing phenyl‐ and pyridyl‐flanked DPP units. These features of the thiazolyl‐based polymer were afforded by its coplanar structure of the main chain. The synthesized polymers showed semiconducting properties in organic field effect transistors and organic photovoltaics. Direct arylation polycondensation is an efficient synthetic method that affords a series of DPP‐based polymers in a simple fashion and, thus, helping in a comprehensive understanding on the relationship between the aromatic groups in DPP units and their physical properties. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2337–2345 相似文献
93.
Magnus Pfaffenbach Dipl.‐Wirtschaftsing. Alexander Roller Prof. Dr. Tanja Gaich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8444-8447
Herein, we report the synthetically practical, short, and general access to novel indolophane architectures by means of a photochemical C?H activation process—the Witkop cyclization. These highly strained scaffolds were obtained by photoinduced ring closure and feature atropisomerism as well as aromatic ring current effects, which both have been investigated. The prevailing regioselectivity of theWitkop cyclization reaction was completely reversed by the presence of a quaternary carbon center, exerting a strong Thorpe–Ingold effect on the system for which experimental‐evidence is provided. 相似文献
94.
95.
Yuta Nohara Junpei Kuwabara Takeshi Yasuda Liyuan Han Takaki Kanbara 《Journal of polymer science. Part A, Polymer chemistry》2014,52(10):1401-1407
A naphthalenediimide (NDI)‐based conjugated polymer was synthesized by a two‐step direct C‐H arylation sequence. In the first step, two ethylenedioxythiophene units were coupled to NDI by direct arylation. In the second step, the direct arylation polycondensation of the monomer, formed in the first step, with 2,7‐dibromo‐9,9‐dioctylfluorene afforded the corresponding NDI‐based conjugated polymer ( PEDOTNDIF ) with molecular weight of 21,500 in 91% yield. The optical and electrochemical properties of the polymer were evaluated. The polymer showed ambipolar behavior in organic field‐effect transistors (OFETs). The electron mobility of PEDOTNDIF was estimated to be 2.3 × 10?6 cm2 V?1 s?1 using an OFET device with source‐drain (S‐D) Au electrodes. A modified OFET device with S‐D MgAg electrodes increased the electron mobility for PEDOTNDIF to 1.0 × 10?5 cm2 V?1 s?1 due to the more suitable work function of these electrodes, which reduced the injection barrier to the semiconducting polymer. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1401–1407 相似文献
96.
CUI Yuan-min FENG Jie-qing 《高校应用数学学报(英文版)》2014,(4):455-467
We implemented accurate FFD in terms of triangular Bezier surfaces as matrix multiplications in CUDA and rendered them via OpenGL. Experimental results show that the proposed algorithm is more efficient than the previous GPU acceleration algorithm and tessel- lation shader algorithms. 相似文献
97.
Thomas Özgün Dr. Klaus Bergander Dr. Lei Liu Dr. Constantin G. Daniliuc Prof. Dr. Stefan Grimme Dr. Gerald Kehr Prof. Dr. Gerhard Erker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):11958-11961
The energy profile of a frustrated Lewis pair (FLP) dihydrogen splitting system was determined by a combined experimental kinetic and DFT study. A trimethylene‐bridged phosphane–borane FLP was converted into its endothermic H2‐cleavage product by sequential H+/H? addition. The system could be handled at low temperature, and the kinetics of the H2 elimination were determined to give a rate constant of kHH,exp(299 K)=(2.87±0.1)×10?4 s?1 in solution. The primary kinetic isotope effects were determined; for example, (kHH/kDD)exp=3.19. The system was accurately analyzed by DFT calculations. 相似文献
98.
Inside Cover: Lipid Nanotube Tailored Fabrication of Uniquely Shaped Polydopamine Nanofibers as Photothermal Converters (Chem. Eur. J. 13/2016) 下载免费PDF全文
99.
Green Approach to the Fabrication of Superhydrophobic Mesh Surface for Oil/Water Separation 下载免费PDF全文
We report a simple and environment friendly method to fabricate superhydrophobic metallic mesh surfaces for oil/water separation. The obtained mesh surface exhibits superhydrophobicity and superoleophilicity after it was dried in an oven at 200 °C for 10 min. A rough silver layer is formed on the mesh surface after immersion, and the spontaneous adsorption of airborne carbon contaminants on the silver surface lower the surface free energy of the mesh. No low‐surface‐energy reagents and/or volatile organic solvents are used. In addition, we demonstrate that by using the mesh box, oils can be separated and collected from the surface of water repeatedly, and that high separation efficiencies of larger than 92 % are retained for various oils. Moreover, the superhydrophobic mesh also possesses excellent corrosion resistance and thermal stability. Hence, these superhydrophobic meshes might be good candidates for the practical separation of oil from the surface of water. 相似文献
100.
Multicomponent Molecular Orbital–Climbing Image–Nudged Elastic Band Method to Analyze Chemical Reactions Including Nuclear Quantum Effect 下载免费PDF全文
To analyze the H/D isotope effects on hydrogen transfer reactions in XHCHCHCHY?XCHCHCHYH (X, Y=O, NH, or CH2) including the nuclear quantum effect of proton and deuteron, we propose a multicomponent molecular orbital‐climbing image‐nudged elastic band (MC_MO–CI–NEB) method. We obtain not only transition state structures but also minimum‐energy paths (MEPs) on the MC_MO effective potential energy surface by using MC_MO–CI–NEB method. We find that nuclear quantum effect affects not only stationary‐point geometries but also MEPs and electronic structures in the reactions. We clearly demonstrate the importance of including nuclear quantum effects for H/D isotope effect on rate constants (kH/kD). 相似文献