首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   465047篇
  免费   3824篇
  国内免费   1310篇
化学   206157篇
晶体学   6873篇
力学   26315篇
综合类   7篇
数学   85683篇
物理学   145146篇
  2021年   3146篇
  2020年   3361篇
  2019年   3807篇
  2018年   19792篇
  2017年   20208篇
  2016年   15097篇
  2015年   5507篇
  2014年   7412篇
  2013年   16282篇
  2012年   18401篇
  2011年   32127篇
  2010年   20882篇
  2009年   21219篇
  2008年   26455篇
  2007年   30675篇
  2006年   12554篇
  2005年   16876篇
  2004年   13693篇
  2003年   13005篇
  2002年   10682篇
  2001年   10747篇
  2000年   8198篇
  1999年   6150篇
  1998年   5192篇
  1997年   4967篇
  1996年   4804篇
  1995年   4071篇
  1994年   3988篇
  1993年   3874篇
  1992年   4236篇
  1991年   4453篇
  1990年   4222篇
  1989年   4136篇
  1988年   3919篇
  1987年   4040篇
  1986年   3804篇
  1985年   4756篇
  1984年   4813篇
  1983年   4022篇
  1982年   4096篇
  1981年   3812篇
  1980年   3771篇
  1979年   4050篇
  1978年   4044篇
  1977年   3949篇
  1976年   3955篇
  1975年   3734篇
  1974年   3674篇
  1973年   3742篇
  1972年   2653篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
81.
82.
83.
Russian Journal of General Chemistry - 8-Phenyltetrazolo[5,1-b][1,3,4]thiadiazepine was obtained as a result of intermolecular cyclization of 1-amino-1H-tetrazole-5-thiol and 3-phenyl-2-propynal....  相似文献   
84.
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   
85.
86.
87.
88.
Russian Chemical Bulletin - Quantum chemical calculations and a comparative analysis of Raman spectra of 3,4,5-triphenyl-1-propyl-1,2-diphosphole (1),...  相似文献   
89.
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   
90.
The microscopic Polymer Reference Interaction Site Model theory is employed to study, for the first time, the effective interactions, spatial organization, and miscibility of dilute spherical nanoparticles in non‐microphase separating, chemically heterogeneous, compositionally symmetric AB multiblock copolymer melts of varying monomer sequence or architecture. The dependence of nanoparticle wettability on copolymer sequence and chemistry results in interparticle potentials‐of‐mean force that are qualitatively different from homopolymers. An important prediction is the ability to improve nanoparticle dispersion via judicious choice of block length and monomer adsorption‐strengths which control both local surface segregation and chain connectivity induced packing constraints and frustration. The degree of dispersion also depends strongly on nanoparticle diameter relative to the block contour length. Small particles in copolymers with longer block lengths experience a more homopolymer‐like environment which renders them relatively insensitive to copolymer chemical heterogeneity and hinders dispersion. Larger particles (sufficiently larger than the monomer diameter) in copolymers of relatively short block lengths provide better dispersion than either a homopolymer or random copolymer. The theory also predicts a novel widening of the miscibility window for large particles upon increasing the overall molecular weight of copolymers composed of relatively long blocks. The influence of a positive chi‐parameter in the pure copolymer melt is briefly studied. Quantitative application to fullerenes in specific copolymers of experimental interest is performed, and miscibility predictions are made. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1098–1111  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号