全文获取类型
收费全文 | 525169篇 |
免费 | 11804篇 |
国内免费 | 5732篇 |
专业分类
化学 | 274223篇 |
晶体学 | 6603篇 |
力学 | 24967篇 |
综合类 | 297篇 |
数学 | 73065篇 |
物理学 | 163550篇 |
出版年
2021年 | 3177篇 |
2020年 | 3887篇 |
2019年 | 3749篇 |
2018年 | 12425篇 |
2017年 | 13162篇 |
2016年 | 10364篇 |
2015年 | 6507篇 |
2014年 | 7516篇 |
2013年 | 19917篇 |
2012年 | 20124篇 |
2011年 | 31273篇 |
2010年 | 19335篇 |
2009年 | 19085篇 |
2008年 | 27318篇 |
2007年 | 30538篇 |
2006年 | 16972篇 |
2005年 | 22263篇 |
2004年 | 16991篇 |
2003年 | 15154篇 |
2002年 | 12925篇 |
2001年 | 13014篇 |
2000年 | 10394篇 |
1999年 | 8283篇 |
1998年 | 6866篇 |
1997年 | 6628篇 |
1996年 | 6766篇 |
1995年 | 6228篇 |
1994年 | 5754篇 |
1993年 | 5457篇 |
1992年 | 6046篇 |
1991年 | 5628篇 |
1990年 | 5250篇 |
1989年 | 5055篇 |
1988年 | 5310篇 |
1987年 | 4993篇 |
1986年 | 4785篇 |
1985年 | 6907篇 |
1984年 | 7002篇 |
1983年 | 5690篇 |
1982年 | 6303篇 |
1981年 | 6196篇 |
1980年 | 5936篇 |
1979年 | 6066篇 |
1978年 | 6203篇 |
1977年 | 6047篇 |
1976年 | 6061篇 |
1975年 | 5875篇 |
1974年 | 5616篇 |
1973年 | 5938篇 |
1972年 | 3468篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
61.
62.
V. A. Bespalov V. M. Glazov E. A. Il’ichev Yu. A. Klimov S. V. Kuklev A. E. Kuleshov R. M. Nabiev G. N. Petrukhin B. G. Potapov G. S. Rychkov D. S. Sokolov V. V. Fandeev E. A. Fetisov S. S. Yakushov 《Technical Physics》2015,60(4):553-560
The results of investigation of optical image detectors designed for the largest problem, near-VUV, range of the spectrum are presented. The possibility of using a dual-stage image detection system to appreciably lower the sensitivity threshold and make computer data processing feasible is considered. The integration of a UV module into a wideband image detector is studied. 相似文献
63.
64.
65.
66.
A (di)graph is supereulerian if it contains a spanning eulerian sub(di)graph. This property is a relaxation of hamiltonicity. Inspired by this analogy with hamiltonian cycles and by similar results in supereulerian graph theory, we analyze a number of sufficient Ore type conditions for a digraph to be supereulerian. Furthermore, we study the following conjecture due to Thomassé and the first author: if the arc‐connectivity of a digraph is not smaller than its independence number, then the digraph is supereulerian. As a support for this conjecture we prove it for digraphs that are semicomplete multipartite or quasitransitive and verify the analogous statement for undirected graphs. 相似文献
67.
68.
A. Lashgari S. Ghammamy R. Ramirez-Tagle G. Salgado-Moran 《Journal of Structural Chemistry》2015,56(8):1505-1513
Two new compounds of fluorine: (C2H5)4N[I2F] and (C2H5)4N[Br2F], have been easily synthesized in a nearly quantitative by a direct reaction of (C2H5)4NF, I2 and Br2. The products were isolated and characterized by elemental analysis and spectroscopic methods such as: Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis). These compounds have been studied computationally with the Scalar ZORA relativistic level of theory using the ADF program package. The molecular parameters, and vibrational spectra were calculated. The excitation energies were found by timedependent perturbation density functional theory (TD-DFT). Molecule optimization, frequencies and excitation energies were calculated with standard Slatertype-orbital (STO) basis sets with triple-zeta quality double plus polarization functions (TZ2P) for all atoms. The FTIR, UV-Vis spectra and assignment of principal transitions and total density of state (TDOS) were extracted using the GaussSum 2.2 program. The comparison between experimental and calculated values showes that the experimental results correlate well with the predicted data. 相似文献
69.
Xiaoxia Yang Hongyan Xie Zhiguang Xu Jiabing Feng Qiwei Fu Haidong Li Yongtang Jia 《Journal of polymer science. Part A, Polymer chemistry》2021,59(9):813-823
An efficient, atom-economic, oxygen-tolerant, and water-tolerant strategy has been established to synthesize cyano-rich polyesters. Four kinds of organic bases, 1,1,3,3-tetramethylguanidine (TMG), 4-dimethylaminopyridine, triethylamine, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) were explored for accelerating Michael addition polymerization of malononitrile and 1,4-butandiol diacrylate. TMG can promote the polymerization efficiently under mild conditions to quantitatively afford polyester with high-molecular weight and moderate polydispersity. The comparison of the kinetic studies of TMG and TBD reveals that TMG shows better catalytic performance, while the catalysis of TBD brings about oligomers in spite of the higher efficiency at early age of the polymerization. Moreover, other diacrylate compounds could also be quantitatively polymerized to afford polyesters with high molecular weight. When dimethacrylate is chose as the monomer, the polymerization becomes sluggish. All the afforded polyesters display programmable thermal and mechanical properties that are closely related to their chemical structures. 相似文献
70.
We present the fabrication of core-shell-satellite Au@SiO2-Pt nanostructures and demonstrate that LSPR excitation of the core Au nanoparticle can induce plasmon coupling effect to initiate photocatalytic hydrogen generation from decomposition of formic acid. Further studies suggest that the plasmon coupling effect induces a strong local electric field between the Au core and Pt nanoparticles on the SiO2 shell, which enables creation of hot electrons on the non-plasmonic-active Pt nanoparticles to participate hydrogen evolution reaction on the Pt surface. In addition, small SiO2 shell thickness is required in order to obtain a strong plamon coupling effect and achieve efficient photocatalytic activities for hydrogen generation. 相似文献