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   2662篇
  免费   232篇
  国内免费   74篇
化学   1986篇
晶体学   18篇
力学   69篇
综合类   3篇
数学   176篇
物理学   716篇
  2023年   33篇
  2022年   18篇
  2021年   66篇
  2020年   77篇
  2019年   88篇
  2018年   57篇
  2017年   68篇
  2016年   111篇
  2015年   98篇
  2014年   136篇
  2013年   178篇
  2012年   228篇
  2011年   277篇
  2010年   164篇
  2009年   139篇
  2008年   201篇
  2007年   151篇
  2006年   194篇
  2005年   152篇
  2004年   125篇
  2003年   75篇
  2002年   67篇
  2001年   44篇
  2000年   23篇
  1999年   18篇
  1998年   22篇
  1997年   22篇
  1996年   14篇
  1995年   17篇
  1994年   11篇
  1993年   13篇
  1992年   4篇
  1991年   7篇
  1990年   5篇
  1989年   4篇
  1988年   7篇
  1987年   8篇
  1986年   3篇
  1985年   5篇
  1984年   6篇
  1983年   8篇
  1982年   3篇
  1981年   2篇
  1980年   6篇
  1979年   5篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1969年   2篇
  1967年   1篇
排序方式: 共有2968条查询结果,搜索用时 15 毫秒
1.
Journal of Optimization Theory and Applications - We consider the conic linear program given by a closed convex cone in an Euclidean space and a matrix, where vector on the right-hand side of the...  相似文献   
2.
Chen  Yujie  Sang  Weixuan  Chen  Rong  Liu  Xue  Li  Xiaoyan  Guan  Fenfen  Li  Xun  Xiao  Hui 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(1):367-373
Journal of Radioanalytical and Nuclear Chemistry - The nanoscale zero-valent nickel (nano-Ni0) was prepared by liquid-phase reduction method and characterized by BET, XPS, FT-IR and XRD and be used...  相似文献   
3.
The mono- and di-chloroform solvates of [Au2(μ-1,2-bis(diphenylarsino)ethane)2](AsF6)2 undergo single-crystal-to-single-crystal transformations that result in gain (over 12 hours) or slow loss (over five years) of only one chloroform molecule. The change in solvation results in changes in the structure and luminescence of the digold cation. The cation consists of a pair of slightly bent As-Au-As units that are connected through the two bridging dpae ligands and by aurophilic interactions with Au⋅⋅⋅Au contacts of 3.05152(15) Å in the disolvate or 2.9570(5) Å in the monosolvate.  相似文献   
4.
Li  Tun  Liu  Yanbing  Wu  Xinhong  Xiao  Yunpeng  Sang  Chunyan 《Nonlinear dynamics》2020,101(4):2671-2686
Nonlinear Dynamics - The large-scale use of the Internet brings the problem of the rapid spread of computer malware over the network. Aiming at the relationship between malware, propagation paths...  相似文献   
5.
6.
Circular polarized luminescence (CPL)-active materials attract great attentions owing to their widely applications in 3D optical displays and encrypted transmission. Inspired by the strategies adopted in perovskite based CPL materials, herein, CPL-active hybrids (D)- and (L)-(tert-butyl prolinate)MnCl3 were successfully prepared by assembling chiral D/L tert-butyl prolinate with manganese (II) chloride. Single crystal structures show the as-formed hybrids possess one-dimensional (1D) structure containing linear chains of face-sharing MnCl6 octahedral surrounded by prolinate cations. The 1D Mn(II) hybrids display strong red emission peaked at 646 nm with PLQY of 67.1 % and 57.2 % for d -type and l -type, respectively, representing the highest PLQY for 1D MnII hybrids. Interestingly, the 1D Mn(II) hybrids exhibit prominent circular dichroism (CD) signals and remarkable CPL activity with the dissymmetry factor g of 6.1*10−3 and −6.3*10−3 from 550 to 800 nm for (D)- and (L)-(tert-butyl prolinate)MnCl3, respectively, owing to the existence of chiral cations. It is worthy noted the obtained g represents the highest value for non-lead organic–inorganic hybrids.  相似文献   
7.
In this paper,we consider a possible modification of the de Sitter and anti-de Sitter space for the extended uncertainty principle.For the modified anti-de Sitter model we discuss the representation and wave functions of the momentum operator for a one-dimensional box problem.Also,we consider modified Snyder and anti-Snyder models for the generalized uncertainty principle.Then,we assume the Hamiltonian with different potential and solve the Heisenberg algebra for the modified(anti)-de Sitter and(anti)-Snyder models in both position and in the momentum space.  相似文献   
8.
A novel plasmonic polarization filter based on the diamond-shape photonic crystal fiber(PCF) is proposed. The resonant coupling characteristics of the PCF polarization filter are investigated by the full-vector finite-element method. By optimizing the geometric parameters of the PCF, when the fiber length is 5 mm, the polarization filter has a bandwidth of 990 nm and an extinction ratio(ER) of lower than -20 dB. Moreover, a single wavelength polarization filter can also be achieved, along with an ER of -279.78 dB at wavelength 1.55 μm. It is believed that the proposed PCF polarization filter will be very useful in laser and optical communication systems.  相似文献   
9.
The wheel-like tungstophosphate ([P8W48O184]40−, abbreviated as P8W48) reacted with estertin trichloride (Cl3SnRCH3, R = CH2CH2COO) in aqueous solution, resulting in a new wheel-like polyoxometalate (POM) containing six SnR fragments, formulated as K6Na24[{(SnR(H2O))2(μ-OH)(μ-SnR(H2O))}2(P8W48O184)]·59H2O (abbreviated as Sn 6 - P 8 W 48 ). Based on this, the transition metal (TM) was further introduced into the Sn 6 - P 8 W 48 system, self-assembling three other wheel-like POMs with the general formula KxNayH26 − x − y[{TM(H2O)3(SnR(H2O))2(μ-OH)(μ-SnR(H2O))}2(P8W48O184)]·nH2O (abbreviated as TM 2 - Sn 6 - P 8 W 48 , TM = Mn, Co, Ni; x = 0, 1, 2; y = 19, 22, 15; n = 72, 85, 75, respectively). The structures of these new organometal and TM co-modified compounds were characterized using infrared, UV–Vis. spectroscopy, 119Sn NMR, and powder- and single-crystal X-ray diffraction analysis. The estertin precursor hydrolyzed into carboxyethyltin (SnR) fragment in these crystalline POM materials, which can improve their adhesion to titanium dioxide (TiO2). The photocatalytic performance of Sn 6 - P 8 W 48 , TM 2 - Sn 6 - P 8 W 48 , and their TiO2 composites was examined by studying the degradation of a model dye pollutant Rhodamine B (RhB) under visible-light irradiation without adding hydrogen peroxide (H2O2), and the photocatalytic mechanism was also discussed. The experimental results show that the title compounds exhibit a quicker and better photocatalytic degradation effect on RhB compared with their parent compound, indicating that the introduced organotin groups play a significant role. Moreover, it was found that H2O2 was produced after illumination pretreatment for POM solution, promoting the photocatalytic reaction.  相似文献   
10.
This review is mainly focused on the optoelectronic properties of diamond-based one-dimensional-metal-oxide heterojunction. First, we briefly introduce the research progress on one-dimensional (1D)-metal-oxide heterojunctions and the features of the p-type boron-doped diamond (BDD) film; then, we discuss the use of three oxide types (ZnO, TiO2 and WO3) in diamond-based-1D-metal-oxide heterojunctions, including fabrication, epitaxial growth, photocatalytic properties, electrical transport behavior and negative differential resistance behavior, especially at higher temperatures. Finally, we discuss the challenges and future trends in this research area. The discussed results of about 10 years’ research on high-performance diamond-based heterojunctions will contribute to the further development of photoelectric nano-devices for high-temperature and high-power applications.  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