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101.
Chellappan Shobana Basuvannan Rangasamy Subramani Surendran Ramakrishnan Kalai Selvan Mathan Ramesh 《Journal of Cluster Science》2018,29(2):267-279
Biosynthesis of silver nanoparticles has received considerable attention due to their cost-effective, eco-friendly and medicinal values. In this study, silver nanoparticles (Ag NPs) were synthesised using the aqueous leaf extracts of Piper nigrum. TEM images revealed that the particle is spherical with 20–50 nm in size. Furthermore, to evaluate the toxicity of synthesized Ag NPs, fish Labeo rohita were exposed to two different concentrations (2.5 µg/L as the treatment I and 5 µg/L as treatment II) for 35 days, and antioxidant parameters and histology of gill, liver and kidney were examined. A biphasic response in the activity of glutathione S-transferases (GST) was observed in gill and liver of fish. GST activity in the kidney of fish was significantly increased when compared to control group. Glutathione reductase (GR) activity in organs/tissue of fish were found to be increased while peroxidase (POD) activity was significantly decreased. Histopathological changes such as hyperplasia, proliferation of epithelial cells and fusion of lamellae were observed in both the concentrations. In liver, necrosis, nuclear degeneration and dilation of sinusoids were observed. Subsequently, the representative effects of POD activity were assessed based on the Box–Behnken Equation, 3-D contour plot and ANOVA analysis through response surface methodology analysis. 相似文献
102.
T V Ramakrishnan 《Pramana》1976,7(2):63-94
The possible instabilities of a 1-dimensional itinerant electron gas are discussed, assuming electron-electron interaction to play the dominant role. As is well known, in the RPA, a 1-dimensional metal is prone to spin density wave (SDW), charge density wave (CDW) and Cooper pair (CP) instabilities. The spin channel decomposition of the irreducible scattering amplitude I is made and the spin channel projections are evaluated in terms of the matrix elements of bare electron-electron interactionV(x) for momenta of interest. It is found that if the bare electron interactionV(x) is repulsive and decreases monotonically with separation, only the SDW instability will occur. If the small separation (x?(2k F )?1) part of the interaction is greatly reduced or is made attractive,V(x) is non-monotonic,V q (q?2k F ) is negative, and a CDW instability is preferred. A CP instability is possible if the electron interaction is attractive,i.e., if [V q (0<q<k F )+V q (q?2k F )]<0. The above RPA results serve only as rough indicators, since in general there are important two-electron configurations with two-electron momentum close to zero and with electron hole momentum close to 2k F , an example being the near Fermi energy configurationk 1?k F ,k 2??k F ,k 3??k F k 4?k F . Therefore as pointed out first by Bychkov, Gorkov and Dzhyaloshinskii (BGD), cross channel coupling is especially significant. It is shown that the cross channel coupling is constructive is some cases,eg., exchange of CD fluctuations leads to an effective electron-electron spin singlet attraction and vice-versa. A formalism for studying such effects is set up, and the particular example mentioned above is discussed. An RPA-like approximation is made for the form of the reducible singlet electron hole scattering amplitudeγ s d and the resulting induced Cooper pair attraction is calculated to be $$\begin{gathered} [I_s ^e ]_{ind.} \rho _{{}^\varepsilon F} = [ln(\lambda \beta \omega _c )]^{ - 1} ln\{ [1 + 2\pi ^{ - 1} ln(\lambda \beta \omega _c )^2 ]/ \hfill \\ 1 + [8\pi ^{ - 1} \gamma _s ^d (q = 2k_F )^{ - 1} )^2 ]\} \hfill \\ \end{gathered} $$ where λ=1.14,β=(k B T)?1 andω 0 is an electronic energy cut-off ~ε F . The induced electron hole attraction due to the exchange of virtual Cooper pairs has a similar expression, but with a factor of (1/4) and withγ s e (q=0) replacingγ s d (q=2k F ). The induced Cooper pair attraction is seen to be quite large over a broad range of temperatures close to but aboveT CDW [i.e., aboveT such thatγ s d (q=2k F )?1=0]. There is no requirement thatγ s d (q=2k F ) andγ s e (q=0) become singular at the same temperature, as found by BGD. The BGD prediction is seen to arise from the neglect of real particle hole and particle-particle excitations while calculatingγ s d andγ s e . The effect of impurities, of electron-phonon coupling, of interchain coupling and of interaction between thermal order parameter fluctuations is discussed. The results are then applied to a discussion of the properties of TTF-TCNQ, where it is suggested that a CDW instability occurs becauseV q (q=2k F )<0,i.e., because the small separation electron repulsion is strongly reduced by the highly polarizable TTF. Because of substantial interchain coupling, the bulk CDW instability occurs close to the RPA instability temperature. The giant conductivity observed by Colemanet al is attributed to superconductive fluctuations in a 1-dimensional system with large mean field superconductive transition temperatureT CP MF of order 300°K. Such a largeT CP MF is shown to result from the induced Cooper pair attraction due to CD fluctuation exchange. 相似文献
103.
104.
Abstract— Analysis of the distribution of pyrimidine-rich tracts (up to decanucleotides) in ascites tumor DNA revealed that these tracts occur predominantly in repetitive sequence of DNA. UV irradiation of ascites DNA resulted in preferential formation of thymine dimers in the pyrimidine-rich tracts as compared to other regions of DNA. 相似文献
105.
Natalija van Well Sitaram Ramakrishnan Ketty Beauvois Navid Qureshi Eric Ressouche Markos Skoulatos Robert Georgii Oksana Zaharko Sander van Smaalen 《Annalen der Physik》2020,532(7):2000147
The triangular antiferromagnetic Cs2CuCl4-xBrx mixed system is studied by neutron single-crystal diffraction in magnetic field. It shows a rich magnetic phase diagram consisting of four regimes depending on the Br concentration and is characterized by different exchange coupling mechanisms. For the investigated compositions from regime I (0 < x ≤ 1.5), a critical magnetic field Bc is found for a Br concentration x = 0.8 at Bc = 8.10(1) T and for x = 1.1 at Bc = 7.73(1) T and from regime IV (3.2 < x < 4) for x = 3.3 at Bc = 0.99(3) T. For magnetic fields larger than the respective Bc, magnetic superlattice reflections of these compounds are not found. The incommensurate magnetic wave vector q = (0, 0.470, 0) appears below the ordering temperature TN = 0.51(1) K for Cs2CuCl3.2Br0.8, and q = (0, 0.418, 0) below TN = 1.00(6) K for Cs2CuCl0.3Br3.7. Neutron diffraction experiments at around 60 mK for x = 3.7 in a magnetic field show the critical magnetic field at Bc = 7.94(16) T and the formation of the second magnetic phase at around 8.5 T depending on the temperature. Inelastic neutron scattering experiments for the compound from regime III (2 < x ≤ 3.2) with x = 2.2 show dynamical correlations at a temperature around 50 mK giving evidence for a spin liquid phase. 相似文献
106.
The molecular recognition properties of p-tert-butyl-calix(8)arene with 1,5 -diamino anthraquinone (1,5 DAAQ) were studied by using UV–Visible and Fluorescence spectroscopic
techniques. The binding constant was determined by using the Benesi-Hilde brand expression. It was found that the host–guest
complex was formed between 1,5 DAAQ and p-tert-butyl- calix(8)arene in the 1:2 Stoichiometry ratio. 相似文献
107.
108.
Irradiation of triazole thiones in thin‐film reactor furnished the corresponding desulfurized triazoles in good yield. The required triazole thiones were synthesized from the respective acid hydrazide and isothiocyanate. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:269–272, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10140 相似文献
109.
The solvatochromic behavior of the 1,4-bis(((2-methylthio) phenylimino)methyl) benzene [BMTPMB] in single solvents and binary
mixtures were investigated. Fluorescence spectra show the dual emission due to twisted intramolecular charge transfer (TICT)
state. The preferential solvation parameters: local mole fraction, X2L, solvation index δs2, exchange constant K12 were calculated for the binary mixtures, ACN+MEOH, DMSO+CCl4 and CCl4+1,2 DCE. The dipole moment ratios between ground and excited states were deduced using the solvatochromic shifts of absorption
and fluorescence spectra as a function of dielectric constant (ε), refractive index (n) and it was found to be 1.25. 相似文献
110.