全文获取类型
收费全文 | 294030篇 |
免费 | 3333篇 |
国内免费 | 425篇 |
专业分类
化学 | 143097篇 |
晶体学 | 3657篇 |
力学 | 14876篇 |
综合类 | 7篇 |
数学 | 46479篇 |
物理学 | 89672篇 |
出版年
2021年 | 1443篇 |
2020年 | 1722篇 |
2019年 | 1759篇 |
2018年 | 11181篇 |
2017年 | 11902篇 |
2016年 | 7875篇 |
2015年 | 3697篇 |
2014年 | 3804篇 |
2013年 | 9077篇 |
2012年 | 12313篇 |
2011年 | 21700篇 |
2010年 | 13252篇 |
2009年 | 13011篇 |
2008年 | 18926篇 |
2007年 | 22507篇 |
2006年 | 7949篇 |
2005年 | 14202篇 |
2004年 | 9832篇 |
2003年 | 8835篇 |
2002年 | 6668篇 |
2001年 | 5208篇 |
2000年 | 4240篇 |
1999年 | 3049篇 |
1998年 | 2623篇 |
1997年 | 2517篇 |
1996年 | 2564篇 |
1995年 | 2244篇 |
1994年 | 2279篇 |
1993年 | 2119篇 |
1992年 | 2401篇 |
1991年 | 2473篇 |
1990年 | 2265篇 |
1989年 | 2270篇 |
1988年 | 2170篇 |
1987年 | 2062篇 |
1986年 | 1956篇 |
1985年 | 2618篇 |
1984年 | 2737篇 |
1983年 | 2205篇 |
1982年 | 2457篇 |
1981年 | 2326篇 |
1980年 | 2222篇 |
1979年 | 2381篇 |
1978年 | 2538篇 |
1977年 | 2286篇 |
1976年 | 2420篇 |
1975年 | 2282篇 |
1974年 | 2341篇 |
1973年 | 2366篇 |
1972年 | 1485篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Pd0‐Catalyzed Intramolecular α‐Arylation of Sulfones: Domino Reactions in the Synthesis of Functionalized Tetrahydroisoquinolines 下载免费PDF全文
Prof.Dr. Daniel Solé Ferran Pérez‐Janer Dr. Raffaella Mancuso 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4580-4584
A new strategy for the synthesis of tetrahydroisoquinolines based on the Pd0‐catalyzed intramolecular α‐arylation of sulfones is reported. The combination of this Pd‐catalyzed reaction with intermolecular Michael and aza‐Michael reactions allows the development of two‐ and three‐step domino processes to synthesize diversely functionalized scaffolds from readily available starting materials. 相似文献
12.
13.
14.
15.
16.
Su X. F. Zhang Y. L. Maximov A. L. Zhang K. Xin Q. Feng C. Q. Bai X. F. Wu W. 《Russian Journal of Applied Chemistry》2020,93(1):127-136
Russian Journal of Applied Chemistry - Nanoscale ZSM-5 (AlZ5-D) and Ga-substituted ZSM-5 zeolites ((Al,Ga)Z5-D and GaZ5-D) were synthesized by a green dry-gel conversion strategy. For comparison,... 相似文献
17.
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
18.
19.
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