全文获取类型
收费全文 | 238735篇 |
免费 | 2733篇 |
国内免费 | 830篇 |
专业分类
化学 | 121475篇 |
晶体学 | 4023篇 |
力学 | 10910篇 |
综合类 | 2篇 |
数学 | 26512篇 |
物理学 | 79376篇 |
出版年
2020年 | 1849篇 |
2019年 | 2148篇 |
2018年 | 2782篇 |
2017年 | 2713篇 |
2016年 | 4110篇 |
2015年 | 2616篇 |
2014年 | 4193篇 |
2013年 | 10444篇 |
2012年 | 7808篇 |
2011年 | 9694篇 |
2010年 | 6958篇 |
2009年 | 6903篇 |
2008年 | 9013篇 |
2007年 | 8995篇 |
2006年 | 8519篇 |
2005年 | 7719篇 |
2004年 | 7170篇 |
2003年 | 6314篇 |
2002年 | 6332篇 |
2001年 | 7231篇 |
2000年 | 5507篇 |
1999年 | 4305篇 |
1998年 | 3626篇 |
1997年 | 3548篇 |
1996年 | 3376篇 |
1995年 | 3069篇 |
1994年 | 3023篇 |
1993年 | 3112篇 |
1992年 | 3217篇 |
1991年 | 3373篇 |
1990年 | 3128篇 |
1989年 | 3069篇 |
1988年 | 3106篇 |
1987年 | 2996篇 |
1986年 | 2837篇 |
1985年 | 3855篇 |
1984年 | 4070篇 |
1983年 | 3254篇 |
1982年 | 3480篇 |
1981年 | 3406篇 |
1980年 | 3302篇 |
1979年 | 3412篇 |
1978年 | 3496篇 |
1977年 | 3427篇 |
1976年 | 3520篇 |
1975年 | 3215篇 |
1974年 | 3225篇 |
1973年 | 3246篇 |
1972年 | 2252篇 |
1971年 | 1863篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Photoisomerisation in Aminoazobenzene‐Substituted Ruthenium(II) Tris(bipyridine) Complexes: Influence of the Conjugation Pathway 下载免费PDF全文
Dr. Anissa Amar Dr. Paul Savel Dr. Huriye Akdas‐Kilig Dr. Claudine Katan Prof. Hacène Meghezzi Prof. Abdou Boucekkine Dr. Jean‐Pierre Malval Dr. Jean‐Luc Fillaut 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8262-8270
Transition‐metal complexes containing stimuli‐responsive systems are attractive for applications in optical devices, photonic memory, photosensing, as well as luminescence imaging. Amongst them, photochromic metal complexes offer the possibility of combining the specific properties of the metal centre and the optical response of the photochromic group. The synthesis, the electrochemical properties and the photophysical characterisation of a series of donor–acceptor azobenzene derivatives that possess bipyridine groups connected to a 4‐dialkylaminoazobenzene moiety through various linkers are presented. DFT and TD‐DFT calculations were performed to complement the experimental findings and contribute to their interpretation. The position and nature of the linker (ethynyl, triazolyl, none) were engineered and shown to induce different electronic coupling between donor and acceptor in ligands and complexes. This in turn led to strong modulations in terms of photoisomerisation of the ligands and complexes. 相似文献
63.
Crosslinked poly(ethylene oxide) containing siloxanes fabricated through thiol‐ene photochemistry 下载免费PDF全文
Victor A. Kusuma Elliot A. Roth William P. Clafshenkel Steven S. Klara Xu Zhou Surendar R. Venna Erik Albenze David R. Luebke Meagan S. Mauter Richard R. Koepsel Alan J. Russell David Hopkinson Hunaid B. Nulwala 《Journal of polymer science. Part A, Polymer chemistry》2015,53(13):1548-1557
Homogenous amphiphilic crosslinked polymer films comprising of poly(ethylene oxide) and polysiloxane were synthesized utilizing thiol‐ene “ click ” photochemistry. A systematic variation in polymer composition was Carried out to obtain high quality films with varied amount of siloxane and poly(ethylene oxide). These films showed improved gas separation performance with high gas permeabilities with good CO2/N2 selectivity. Furthermore, the resulting films were also tested for its biocompatibility, as a carrier media which allow human adult mesenchymal stem cells to retain their capacity for osteoblastic differentiation after transplantation. The obtained crosslinked films were characterized using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, FTIR, Raman‐IR , and small angle X‐ray scattering. The synthesis ease and commercial availability of the starting materials suggests that these new crosslinked polymer networks could find applications in wide range of applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1548–1557 相似文献
64.
Experimental Mechanics - Insufficient data are available to fully understand the effects of metal additive manufacturing (AM) defects for widespread adoption of the emerging technology.... 相似文献
65.
66.
67.
Naphthalimide‐phthalimide derivative based photoinitiating systems for polymerization reactions under blue lights 下载免费PDF全文
Pu Xiao Frédéric Dumur Jing Zhang Bernadette Graff Didier Gigmes Jean Pierre Fouassier Jacques Lalevée 《Journal of polymer science. Part A, Polymer chemistry》2015,53(5):665-674
Naphthalimide‐phthalimide derivatives (NDPDs) have been synthesized and combined with an iodonium salt, N‐vinylcarbazole, amine or 2,4,6‐tris(trichloromethyl)‐1,3,5‐triazine to produce reactive species (i.e., radicals and cations). These generated reactive species are capable of initiating the cationic polymerization of epoxides and/or the radical polymerization of acrylates upon exposure to very soft polychromatic visible lights or blue lights. Compared with the well‐known camphorquinone based systems used as references, the novel NDPD based combinations employed here demonstrate clearly higher efficiencies for the cationic polymerization of epoxides under air as well as the radical polymerization of acrylates. Remarkably, one of the NDPDs (i.e., NDPD2) based systems is characterized by an outstanding reactivity. The structure/reactivity/efficiency relationships of the investigated NDPDs were studied by fluorescence, cyclic voltammetry, laser flash photolysis, electron spin resonance spin trapping, and steady state photolysis techniques. The key parameters for their reactivity are provided. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 665–674 相似文献
68.
Gelikonov G. V. Ksenofontov S. Yu. Shilyagin P. A. Gelikonov V. M. 《Radiophysics and Quantum Electronics》2019,62(3):228-236
Radiophysics and Quantum Electronics - We propose and experimentally test a numerical method for correction of the influence of fluctuations in the distance to objects during noncontact probing in... 相似文献
69.
A.G. Rousskikh A.V. Fedyunin A.P. Artyomov A.S. Zhigalin V.I. Oreshkin 《Current Applied Physics》2019,19(6):704-708
The aim of the study presented in this paper was to characterize quantitatively the erosion of aluminum cathodes in high-current vacuum arcs. The experimental setup comprised two current generators. The first one, capable of generating a current of amplitude up to 350 kA, was used to produce a plasma jet, that is, the object to be investigated. The second generator was used to produce a source of probe radiation for imaging the object under investigation in soft x rays of energy ?ν ≈ 0.5–3 keV. The findings of the study are based on experimental data obtained by electrophysical and radiographic methods. It has been shown that the cathode erosion rate in a high-current vacuum arc is a function of the charge passed through the cathode. 相似文献