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81.
Amlan J. Kalita Namrata Gohain Abhik Bordoloi Dr. Kusum K. Bania Dr. Ankur K. Guha 《Chemphyschem》2023,24(9):e202200873
Number of bonds formed by sharing an electron pair between two atoms is not restricted to one, it can go beyond four and six is the maximum. While homopolar sextuple bond in Mo2 and W2 has been reported, such a high bond order in heteropolar diatomics has remained elusive. In the pursuit of the sextuple bond in polar diatomics, the present study depicts the existence of such multiple bonds in Rhodium-Scandium hetero-diatom based on relativistic quantum chemical calculations. The bonding comprises of three normal electron sharing covalent bonds and three dative covalent bonds. 相似文献
82.
83.
Lei Zhu Christopher J. Brassard Xiaoguang Zhang Pampa M. Guha Ronald J. Clark 《Chemical record (New York, N.Y.)》2016,16(3):1501-1517
The copper(I)‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction regiospecifically produces 1,4‐disubstituted‐1,2,3‐triazole molecules. This heterocycle formation chemistry has high tolerance to reaction conditions and substrate structures. Therefore, it has been practiced not only within, but also far beyond the area of heterocyclic chemistry. Herein, the mechanistic understanding of CuAAC is summarized, with a particular emphasis on the significance of copper/azide interactions. Our analysis concludes that the formation of the azide/copper(I) acetylide complex in the early stage of the reaction dictates the reaction rate. The subsequent triazole ring‐formation step is fast and consequently possibly kinetically invisible. Therefore, structures of substrates and copper catalysts, as well as other reaction variables that are conducive to the formation of the copper/alkyne/azide ternary complex predisposed for cycloaddition would result in highly efficient CuAAC reactions. Specifically, terminal alkynes with relatively low pKa values and an inclination to engage in π‐backbonding with copper(I), azides with ancillary copper‐binding ligands (aka chelating azides), and copper catalysts that resist aggregation, balance redox activity with Lewis acidity, and allow for dinuclear cooperative catalysis are favored in CuAAC reactions. Brief discussions on the mechanistic aspects of internal alkyne‐involved CuAAC reactions are also included, based on the relatively limited data that are available at this point. 相似文献
84.
Wang H Klinginsmith J Dong X Lee AC Guha R Wu Y Crippen GM Wild DJ 《Journal of chemical information and modeling》2007,47(6):2063-2076
The NCI Developmental Therapeutics Program Human Tumor cell line data set is a publicly available database that contains cellular assay screening data for over 40 000 compounds tested in 60 human tumor cell lines. The database also contains microarray assay gene expression data for the cell lines, and so it provides an excellent information resource particularly for testing data mining methods that bridge chemical, biological, and genomic information. In this paper we describe a formal knowledge discovery approach to characterizing and data mining this set and report the results of some of our initial experiments in mining the set from a chemoinformatics perspective. 相似文献
85.
Dong X Gilbert KE Guha R Heiland R Kim J Pierce ME Fox GC Wild DJ 《Journal of chemical information and modeling》2007,47(4):1303-1307
The vast increase of pertinent information available to drug discovery scientists means that there is a strong demand for tools and techniques for organizing and intelligently mining this information for manageable human consumption. At Indiana University, we have developed an infrastructure of chemoinformatics Web services that simplifies the access to this information and the computational techniques that can be applied to it. In this paper, we describe this infrastructure, give some examples of its use, and then discuss our plans to use it as a platform for chemoinformatics application development in the future. 相似文献
86.
Partha Guha 《Acta Appl Math》2007,95(1):1-30
We consider the action of vector field Vect(S
1) on the space of an sl
n
- opers on S
1, i.e., a space of nth order differential operator . This action takes the sections of Ω
–(n–1)/2 to those of Ω
(n+1)/2, where Ω is the cotangent bundle on S
1. In this paper we study Euler–Poincaré (EP) flows on the space of sl
n
opers, in particular, we demonstrate explicitly EP flows on the space of third and fourth order differential operators (or
sl
3 and sl
4 opers) and its relation to Drienfeld–Sokolov, Hirota–Satsuma and other coupled KdV type systems. We also discuss the Boussinesq
equation associated with the third order operator. The solutions of the sl
n
oper defines an immersion in homogeneous coordinates. We derive the Schwarzian KdV equation as an evolution of the solution curve associated to Δ
(n), we study the factorization of higher order operators and its compatibility with the action of Vect(S
1). We obtain the generalized Miura transformation and its connection to the modified Boussinesq equation for sl
3 oper. We also study the eigenvalue problem associated to sl
4 oper. We discuss flows on the special higher order differential operators for all u
i
= f(u,u
x
,u
xx
⋯) and its connection to KdV equation. Finally we explore a relation between projective vector field equation and generalized
Riccati equations.
相似文献
87.
88.
89.
Sankar J Rath H Prabhuraja V Gokulnath S Chandrashekar TK Purohit CS Verma S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(1):105-114
The synthesis and characterization of the first examples of core-modified corrole dimers linked through the meso positions are described. The dimers are obtained by a simple Ag(I)- or Fe(III)-catalyzed coupling reaction in near-quantitative yields. The corroles obtained are metalated with metal ions, such as Cu(II) and Ni(II). The electronic-absorption spectral studies reveal weak electronic interaction between the two subunits and the exciton coupling observed for the free-base corrole dimer (1717 cm(-1)) is lower than that for the corresponding protonated derivative (4081 cm(-1)). The solution-state structure derived from (1)H and two-dimensional NMR spectral studies reveals a noncoplanar arrangement of two corrole units. Geometry optimization at the B3LYP-631G level also confirms the noncoplanar arrangement of corroles with a dihedral angle of 64.8 degrees between two corrole planes. The electron paramagnetic resonance (EPR) and magnetic characterization studies on the paramagnetic copper-metalated dimer indicate that both copper ions behave as independent spins without any noticeable interaction. Results of fluorescence studies reveal a bathochromic shift of about 60 nm upon dimerization. The first hyperpolarizability (beta) measured by using the hyper Rayleigh scattering (HRS) method reveals doubling of the beta values on progressing from monomer to dimer, attributed to enhanced pi conjugation. The use of copper dimers in the photocleavage of DNA is also explored. It is shown that the bimetallic copper dimer selectively cleaves the nucleic acids without affecting the proteins, suggesting a possible application of the copper complex in the removal of nucleic acid contaminants from protein extracts through a simple photolytic pathway. 相似文献
90.
A density functional theory based on Wertheim's first order perturbation theory is developed for inhomogeneous complex fluids. The theory is derived along similar lines as interfacial statistical associating fluid theory [S. Tripathi and W. G. Chapman, J. Chem. Phys. 122, 094506 (2005)]. However, the derivation is more general and applies broadly to a range of systems, retaining the simplicity of a segment density based theory. Furthermore, the theory gives the exact density profile for ideal chains in an external field. The general avail of the theory has been demonstrated by applying the theory to lipids near surfaces, lipid bilayers, and copolymer thin films. The theoretical results show excellent agreement with the results from molecular simulations. 相似文献