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   142篇
  免费   4篇
  国内免费   7篇
化学   76篇
晶体学   2篇
力学   6篇
数学   58篇
物理学   11篇
  2023年   4篇
  2022年   1篇
  2021年   7篇
  2020年   5篇
  2019年   9篇
  2018年   5篇
  2017年   2篇
  2016年   8篇
  2015年   8篇
  2014年   9篇
  2013年   13篇
  2012年   8篇
  2011年   11篇
  2010年   3篇
  2009年   5篇
  2008年   4篇
  2007年   3篇
  2006年   6篇
  2005年   6篇
  2004年   2篇
  2003年   2篇
  2002年   3篇
  2001年   2篇
  2000年   3篇
  1998年   2篇
  1997年   1篇
  1996年   3篇
  1995年   2篇
  1994年   2篇
  1992年   1篇
  1991年   1篇
  1989年   1篇
  1988年   1篇
  1984年   1篇
  1983年   2篇
  1982年   1篇
  1981年   2篇
  1979年   1篇
  1977年   3篇
排序方式: 共有153条查询结果,搜索用时 46 毫秒
1.
乌兰哈斯 《数学杂志》1994,14(2):227-232
本文研究了混合范数空间H(p,q,a)中解析函数f的Taylor系数,对0<p≤2,0<q<∞,a>0和2≤p<∞,0<q<∞,a>0两种情形,分别给出了f属于H(p,q,a)的必要条件和充分条件。用上述结果我们还得到了几个关于混合范数空间的乘子定理,这些结果也推广了Hardy和Littlewood关于H^p空间的相应结论。  相似文献   
2.
The new mixed-valence mixed-metal complex Cu(py)6Cu2Ag2(CN)6 (py = pyridine) possesses a three dimensional polymeric crystal structure. The Cu(I) atom is tetrahedrally coordinated by two nitrogen atoms of pyridine molecules, by one nitrogen atom of the dicyanoargentate anion and by one carbon atom of the cyano group. Both the dicyanoargentate anion and the cyano group bridge the Cu(I) atom with neighboring Cu(II) atoms. These are hexacoordinated in the form of an elongated tetragonal bipyramid. The equatorial plane is formed by two nitrogen atoms from two pyridine molecules and two nitrogen atoms from bridging cyano groups. Axial positions are occupied by nitrogen atoms of the bridging [Ag(CN2] anions. Correlation between structures of the title compound and seven other dicyanoargentates with their i.r. spectra has been studied. The coordination mode of [Ag(CN2] anions in compounds Cu8-xAgx(tn)3(CN)10 x = 0.25, Cu(3-Mepy)2Ag2(CN)4, Cu(py)2Ag2(CN)4 and Cu(py)4Ag2(CN)4 (tn is 1,3-diaminopropane, 3-Mepy is 3-methylpyridine) is predicted based on this correlation.  相似文献   
3.
LetK be an algebraically closed field withp:=char (K)>0 andX a bielliptic curve over Spec(K) with genus≥6 and such that the canonical model ofX is ordinary. In this paper we determine all the possible gap sequences of Weierstrass points on such curves.  相似文献   
4.

Films of titanate nanosheets (approx. 1.8-nm layer thickness and 200-nm size) having a lamellar structure can form electrolyte-filled semi-permeable channels containing tetrabutylammonium cations. By evaporation of a colloidal solution, persistent deposits are readily formed with approx. 10-μm thickness on a 6-μm-thick poly(ethylene-terephthalate) (PET) substrate with a 20-μm diameter microhole. When immersed in aqueous solution, the titanate nanosheets exhibit a p.z.c. of − 37 mV, consistent with the formation of a cation conducting (semi-permeable) deposit. With a sufficiently low ionic strength in the aqueous electrolyte, ionic current rectification is observed (cationic diode behaviour). Currents can be dissected into (i) electrolyte cation transport, (ii) electrolyte anion transport and (iii) water heterolysis causing additional proton transport. For all types of electrolyte cations, a water heterolysis mechanism is observed. For Ca2+ and Mg2+ions, water heterolysis causes ion current blocking, presumably due to localised hydroxide-induced precipitation processes. Aqueous NBu4+ is shown to ‘invert’ the diode effect (from cationic to anionic diode). Potential for applications in desalination and/or ion sensing are discussed.

  相似文献   
5.
In this work,the entropy functions of ideal quantum gases in a three-dimensional harmonic trap are analytically calculated using temperature as an explicit variable.Afterward,the applicability of the analytical formulas is validated by comparison with the numerical calculation.The results illustrate that the obtained functions could be applied for the whole temperature regime with a maximum relative deviation of less than 7.5%in the vicinity of the critical temperature Tcin the case of Bose gases.Meanwhile,for Fermi gases,although the analytical formula fits well at very low-and high-temperature regimes,it cannot be applied at temperature in the range[0.3-0.5]T_F,where T_F is the Fermi temperature.In addition,the consistency between our formulas and classical ones at significantly high temperatures is also discussed.  相似文献   
6.
We consider a generating function of the domino tilings of an Aztec rectangle with several unit squares removed from the boundary. Our generating function involves two statistics: the rank of the tiling and half number of vertical dominoes as in the Aztec diamond theorem by Elkies, Kuperberg, Larsen and Propp. In addition, our work deduces a combinatorial explanation for an interesting connection between the number of lozenge tilings of a semihexagon and the number of domino tilings of an Aztec rectangle.  相似文献   
7.
Ultraviolet (UV) irradiation is a serious problem for skin health thus the interest in the research to develop sunscreen agent has been increasing. Chalcone is a promising compound to be developed as its chromophore absorbs in the UV region. Therefore, in the present work, we synthesized eight chalcone derivatives through Claisen–Schmidt condensation at room temperature. The evaluation of the optical properties of each chalcone derivatives in the UV region was conducted through spectroscopic and computational studies. The synthesized chalcones were obtained in good yields and they were active in the UV region. The results revealed that more methoxy substituents to chalcone leads toward red shift. All chalcone derivatives have high molar absorptivity value (21,000–56,000) demonstrating that they have the potential to be used as the sunscreen agent. The cytotoxicity assay showed that chalcone derivatives were demonstrating low toxicity toward normal human fibroblast cell, which is remarkable. Therefore, we concluded that the synthesized chalcones in this work were potential to be developed as novel sunscreen agents in real application.  相似文献   
8.
Density functional theory and multiconfigurational CASPT2 and density matrix renormalization group DMRG-CASPT2 have been employed to study the low-lying states of NbGen−/0/+ (n = 1–3) clusters. With the DMRG-CASPT2 method, the active spaces are extended to a size of 20 orbitals. For most of the states, the CASPT2 relative energies are comparable with the DMRG-CASPT2 results. The leading configuration, bond distances, vibrational frequencies, and relative energies of the low-lying states of these clusters were calculated. The ground states of these clusters were computed to be 3Δ, 4Φ, and 5Φ of NbGe−/0/+; 3A2, 4B1, and 3B1 of cyclic-NbGe2−/0/+; and 1A′, 12A″ and 12A′′ (2E), and 3A″ of tetrahedral-NbGe3−/0/+ isomers. For NbGe cluster, our calculations proposed that the 6∑ is almost degenerate with the 4Φ with the CASPT2 and DMRG-CASPT2 relative energies of 0.05 and 0.06 eV. The adiabatic detachment energies of NbGen (n = 1–3) clusters were estimated to be 1.46, 1.55, and 2.18 eV by the CASPT2 method. The relevant detachment energies of the anionic ground state and the ionization energies of the neutral ground states are evaluated at the CASPT2 level.  相似文献   
9.
This paper is a continuation of our earlier note [V. T. T. Hien and N. M. Tri, “Analyticity of Solutions of Semililnear Equations with Double Characteristics,” J. Math. Anal. Appl. 337, 1249–1260 (2008)]. Here we prove the analyticity of solutions of a class of semilinear elliptic degenerate equations with double characteristics by using the Fourier transform.  相似文献   
10.
Metallabisphosphonates as Chelating Ligands. II. Synthesis and Reactivity of Mono- and Binuclear Palladiumbisphosphonate Complexes Containing OHO and OBF2O Bridges The complexes C5H5Pd[{P(OR)2O}2H] ( 1 : R = Me; 2 : R = Et) are formed either by reaction of C5H5Pd(2-MeC3H4) with dimethyl- and diethylphosphite or by reaction of [ClPd{P(OR)2O}2H]2 ( 3 : R = Me; 4 : R = Et) with TlC5H5. With excess HP(O)(OMe)2, the π-allyl complex (2-MeC3H4)Pd[{P(OMe)2O}2H] ( 5 ) is also formed (besides 1 ) from C5H5Pd(2-MeC3H4). The 1H and 31P n.m.r. spectra indicate that in 1 – 5 the PdP2O2H chelate ring presumably contains a symmetrical OHO-hydrogen bond. The reaction of 3 with BF3 etherate leads to the binuclear complex [ClPd{P(OMe)2O}2BF2]2 ( 6 ) which reacts with TlC5H5 to yield C5H5Pd[{P(OMe)2O}2BF2] ( 7 ). From C5H5Pd[{P(OR)2O}2H] ( 1 , 2 ) and NH3 the bisamminepalladium bisphosphonates(NH3)2Pd[P(OR)2O]2 ( 8 , 9 ) are formed which probably possess a trans-configuration. The reaction of 8 , 9 with CF3COOH does not lead to a corresponding Pd[{P(OR)2O}2H] chelate complex but instead gives by elimination of NH3 polymeric palladium bisphosphonates [Pd{P(OR)2O}2]n ( 10 , 11 ). 1 reacts with thallium acetylacetonate to give C5H5Pd[P(OMe)2O]2Tl ( 12 ).  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