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271.
The binary encounter approximation has been used to investigate the effect of charge state of the target atom (ion) on the
electron impact excitation autoionization cross-sections. Roothan-Hartree-Fock (RHF) velocity distribution for the bound electrons
has been used through-out the calculations. The present results give a good account of the experimental observations. 相似文献
272.
Indira H. Shrivastava Shridhar R. Gadre 《International journal of quantum chemistry》1994,49(4):397-407
Electrostatic charge models for molecules have been developed by employing the critical topographical features of the molecular electrostatic potential (MESP ) as the “fitting” criterion. These models include one or more spherical Gaussians for incorporating the continuous electron-charge distribution in addition to the positive valued point charges representing the nuclei. The model parameters (point charges, the orbital exponents, and Gaussian centers) are optimized so as to mimic the extremal characteristics of the corresponding quantum chemical MESP . The test cases reported here include methane, ethylene, and methanol molecules. The charge models developed using the present method are seen to satisfactorily reproduce the ab initio MESP and its extremal features. © 1994 John Wiley & Sons, Inc. 相似文献
273.
Suryanarayan MV Shrivastava RK Pandey D Vaidyanathaswamy R Mahajan S Bhoumik D 《Journal of chromatography. A》2001,907(1-2):229-234
A simple air-monitoring method was developed and validated for vesicant sulfur mustard (HD) in the work place at time weighted average levels. XAD-2 adsorbent was used for the collection of HD vapours for 8 h followed by liquid desorption with carbon tetrachloride. The trace level analysis was carried out by gas chromatography-photoionization detection and was confirmed by gas chromatography-mass spectrometric detection in the selected ion mode. 相似文献
274.
I. P. Saraswat S. K. Shrivastava A. K. Sharma 《Journal of Radioanalytical and Nuclear Chemistry》1981,67(2):453-458
Distribution coefficients of a number of uni-, di-, tri- and quadrivalent metal ions have been determined on chromium ferrocyanide
gel loaded with [Co(NH3)6]3+ and [Co(en)3]3+ ions at 25 °C, and the observed Kd values are compared with those obtained on the unloaded exchanger in H-form. The gel is found to develop ion-sieve properties
after being loaded with the complex cations. The variation in Kd values with the pH of Rb+, Cs+, Ti+ and Ag+ solutions has also been studied to understand the mechanism of their uptake. 相似文献
275.
Kamlakar Avasthi Sangeeta Aswal Rishi Kumar Umesh Yadav Diwan S. Rawat Prakas R. Maulik 《Journal of Molecular Structure》2005,750(1-3):179-185
Proton NMR and X-ray crystallographic analysis of two newly synthesized ‘trimethylene linker,’ (Leonard linker) compounds 1,3-bis(4-ethoxy-6-methylsulfanyl-lH-pyrazolo[3,4-d]pyrimidin-1-yl)propane (4c) and 1,3-bis(4-isopropoxy-6-methylsulfanyl-1H-pyrazolo[3,4-d]pyrimidin-1-yl)propane (4d) show intramolecularly stacked conformations both in solution and solid state. Robustness of the unusual U-motif formed due to intramolecular stacking in earlier related compounds (1, n=3 and 3, n=3) is not only confirmed but additional fine tuning is also achieved in new compounds (4) formed by replacement of remote 4-alkylsulfanyl group in 1a by 4-alkoxy substituents. 相似文献
276.
Ahluwalia Vinod K. Singh Daljeet Singh Rishi P. 《Monatshefte für Chemie / Chemical Monthly》1985,116(6-7):869-872
Reaction of 2-hydroxybenzophenones (1,3,7,8) with ethoxycarbonyl-methylenetriphenylphosphorane affords 4-aryl-2H-1-benzopyran-2-ones (2,4–6) in excellent yields.
Eine einfache Synthese für 4-Aryl-2H-1-benzopyran-2-one
Zusammenfassung Die Reaktion der 2-Hydroxybenzophenone1,3,7 und8 mit Ethoxycarbonyl-methylentriphenylphosphoran ergab die 4-Aryl-2H-1-benzopyran-2-one2 und4–6 in ausgezeichneten Ausbeuten.相似文献
277.
Singh N Shukla KK Patel RN Chauhan UK Shrivastava R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(13):3111-3122
X-band e.s.r. and optical absorption spectra of the imidazolate bridged heterobimetallic complexes [(tren)Cu-E-Im-Zn-(tren)](ClO(4))(3) and [(tren)Cu-E-Im-Ni-(tren)](ClO(4))(3), where trentris(2-aminoethyl)amine, E-Im=2-ethylimidazolate ion and the related mononuclear complexes [Cu(tren)](ClO(4))(2) and [(tren)Cu-E-ImH)](ClO(4))(2) have been described. Biological activities (superoxide dismutase and antimicrobial) have also been measured and compared with reported complexes. 相似文献
278.
Singh Nand K. Singh Aparna Sodhi Ajit Shrivastava Anju 《Transition Metal Chemistry》1997,22(6):570-574
New complexes [M(dtf)2] (M=MnII or CuII), Cr(dtf)3 and V(dtf)4 (dtf=dithiofuroate) and heterobimetallic complexes M[Cd(dtf)4]
(M=VO2+, MnII, FeII, CoII, NiII or ZnII) have been prepared in H2O−EtOH and characterized by elemental analyses, magnetic
susceptibility measurements and spectroscopic studies. The known complexes Fe(dtf)3, Co(dtf)3, Ni(dtf)2, and Zn(dtf)2 have
been screened towards the bacteria Pseudomonas spergillus and Bacillus spergillus. In vitro results of the binary complexes
on P-815 (murine mastocytoma) indicate that these complexes show significant inhibition of [3H]thymidine and [3H]uridine incorporation
in DNA and RNA in the tumour cells.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
279.
280.
Soil-venting or vacuum extraction is an effective tool for remediation of soils contaminated with volatile compounds. Brusseau’s
[Water Resour. Res. 27(12), 3189–3199, 1991] model of fate and transport of volatile compounds in the gaseous phase of dual-porosity soils with
rate-limited sorption is adopted in this study. Using temporal moment analysis, expressions for effective velocity and dispersion
are derived. The values of effective transport properties are presented for a set of volatile compounds for two typical soils.
Sensitivity of these effective parameters to Peclet and Damkohler numbers is discussed. 相似文献