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991.
Aleem Gangjee Anil Vasudevant Roy L. Kisliuk 《Journal of heterocyclic chemistry》1997,34(6):1669-1676
Classical inhibitors of thymidylate synthase such as Nl0-propargyl-5,8-dideazafolic acid (1), N-(5-[N-(3,4-dihydro-2-methyl-4-oxoquinazolin-6-ylmethyl)-N-methylamino]-2-thenoyl)-L-glutamic acid (ZD1694, 2) and N-[2-amino-4-oxo-3,4-dihydro(pyrrolo[2,3-d]pyrintidin-5-yl)ethylbenzoyl]-L-glutamic acid (LY231514, 3) while potent, suffer from a number of potential disadvantages, such as impaired uptake due to an alteration of the active transport system required for their cellular uptake, as well as formation of long acting, non-effluxing polyglutamates via the action of folylpolyglutamate synthetase, which are responsible for toxicity. To overcome some of the disadvantages of classical inhibitors, there has been considerable interest in the synthesis and evaluation of nonclassical thymidylate synthase inhibitors, which could enter cells via passive diffusion. In an attempt to elucidate the role of saturation of the B-ring of non-classical, quinazoline antifolate inhibitors of thymidylate synthase, analogues 7-17 were designed. Analogues 13-17 which contain a methyl group at the 7-position, were synthesized in an attempt to align the methyl group in an orientation which allows interaction with tryptophan-80 in the active site of thymidylate synthase. The synthesis of these analogues was achieved via the reaction of guanidine with the appropriately substituted cyclohexanone-ketoester. These ketoesters were in turn synthesized via a Michael addition of the appropriate thiophenol with 2-carbethoxycyclohexen-1-one or 5-methyl-2-carbethoxycyclo-hexen-1-one to afford a mixture of diastereomers. The most inhibitory compound was the 3,4-dichloro, 7-methyl derivative 17 which inhibited the Escherichia coli and Pneumocystis carinii thymidylate syntheses 50% at 5 × 105 M. Our results confirm the importance of the 7-CH3 group and electron withdrawing groups on the aromatic side chain for thymidylate synthase inhibition. 相似文献
992.
The compound di-2-thienyl ketone p-nitrophenylhydrazone (DSKNPH) melting point 168-170 °C was isolated in good yield from the reaction between di-2-thienyl ketone (DSK) and p-nitrophenylhydrazine in refluxing ethanol containing a few drop of concentrated HCl. Nuclear magnetic resonance studies on DSKNPH in non-aqueous solvents revealed strong solvent and temperature dependence due to solvent-solute interactions. Optical measurements on DSKNPH in DMSO in the presence and absence of KPF6 gave extinction coefficients of 83,300±2000 and 25,600±2000 M−1 cm−1 at 612 and 427 nm at 295 K. In CH2Cl2, extinction coefficient of 34,000±2000 M−1 cm−1 was calculated at 422 nm. When DMSO solutions of DSKNPH were allowed to interact with DMSO solutions of NaBH4 the low energy electronic state becomes favorable and when DMSO solutions of DSPKNPH where allowed to interact with DMSO solutions of KPF6 or NaBF4, the high energy electronic state becomes favorable. The reversible BH4−/BF4− interconversion points to physical interactions between these species and DSKNPH and hints to the possible use of DSKNPH as a spectrophotometric sensor for a variety of physical and chemical stimuli. Thermo-optical measurements on DSKNPH in DMSO confirmed the reversible interconversion between the high and low energy electronic states of DSKNPH and allowed for the calculations of the thermodynamic activation parameters of DSKNPH. Changes in enthalpy (ΔH∅) of +57.67±4.20; 27.15±0.90 kJ mol−1, entropy (ΔS∅) of +160±12.88; 83±2.91 J mol−1 and free energy (ΔG∅) of −8.52±0.40; 2.66±0.25 kJ mol−1 were calculated at 295 K in the absence and presence of NaBH4, respectively. Manipulation of the equilibrium distribution of the high and low energy electronic states of DSKNPH allowed for the use of these systems (DSKNPH and surrounding solvent molecules) as molecular sensors for group I and II metal ions. Group I and II metal ions in concentrations as low as 1.00×10−5 M can be detected and determined using DSKNPH in DMSO. 相似文献
993.
Debapriya De Amit Das Brojendranath Dey Bidhan Chandra Roy 《European Polymer Journal》2006,42(4):917-927
The present paper describes the mechanical reclaiming of ground rubber tire (GRT) by tetra methyl thiuram disulfide (TMTD), a multi-functional reclaiming agent. The versatility of the proposed agent is that it acts as a reclaiming agent during reclaiming and as a curing agent during revulcanization of the reclaimed sample. Reclaiming of GRT was carried out on an open two roll mixing mill at various time intervals and different concentrations of the reclaiming agent (TMTD). The degree of reclaiming was evaluated by measurement of the gel content, inherent viscosity of sol rubber, Mooney viscosity of the reclaimed rubber, crosslink density, swelling ratio and molecular weight between two crosslink bonds as a function of milling time. Also, the influence of the gel content on crosslink density at various time intervals on the open two roll mixing mill was determined. A unique correlation between gel fraction and crosslink density obtained at various time intervals and concentrations of reclaiming agent indicated that an optimization of the concentration of TMTD and milling time has a positive influence on improving the efficiency of reclaiming. The reclaiming conditions have been optimized in view of the mechanical properties of the revulcanized GRT and the aging resistance properties of the revulcanized reclaim. The influence of the concentration of sulfur on the mechanical properties in the revulcanized reclaim was also studied. Scanning electron microscopy (SEM) studies further indicate the coherency and homogeneity in the revulcanized reclaim rubber when reclamation is carried out by optimum concentration of TMTD after maximum time of reclaiming. 相似文献
994.
A soft nanochannel involves a soft interface that contains a polyelectrolyte layer (PEL) sandwiched between a rigid surface and a bulk electrolyte solution. Mass transfer of a neutral solute in a combined electroosmotic and pressure driven flow through a polyelectrolyte grafted charged nanochannel with porous wall is presented in this work. Assuming the PEL as fixed charged layer and PEL-electrolyte interface as a semi-penetrable membrane, analytical solutions were obtained for potential distributions (for small wall potential). Velocity profiles were also derived in the same domains, for both inside and outside the PEL. Convective-diffusive species balance equation was semi-analytically solved inside the PEL. Expression of length averaged Sherwood number was also obtained and effects of different parameters, namely, drag parameter (α), Debye parameter , and PEL thickness were studied in detail. The variation of permeate concentration and permeation flux across the porous wall was obtained. 相似文献
995.
We derive and compare with experimental data the bound , where α is the fine-structure constant, mp the proton mass, ν0 the photo-pion production threshold, σtot and are the unpolarized total hadronic photo-absorption cross section on protons and the unpolarized forward differential cross section for proton Compton scattering at photon-lab energy ν′, and λ and ν1 are any real numbers. We derive similar bounds on proton and neutron magnetic moments. 相似文献
996.
Atiya MS Chiang IH Frank JS Haggerty JS Ito MM Kycia TF Li KK Littenberg LS Stevens A Strand RC Louis WC Akerib DS Hildreth M Marlow DR Meyers PD Selen MA Shoemaker FC Smith AJ Azuelos G Blackmore EW Bryman DA Felawka L Kitching P Kuno Y Macdonald JA Numao T Padley P Poutissou JM Poutissou R Roy J 《Physical review letters》1989,63(20):2177-2180
997.
Berger C Fröhlich M Mönch H Nisius R Raupach F Schleper P Benadjal Y Blum D Bourdarios C Dudelzak B Eschstruth P Jullian S Lalanne D Laplanche F Longuemare C Paulot C Perdereau O Roy P Szklarz G Behr L Degrange B Minet Y Nguyen-Khac U Serri P Tisserant S Tripp RD Arpesella C Bareyre P Barloutaud R Borg A Chardin G Ernwein J Glicenstein JF Mosca L Moscoso L Becker J Becker KH Daum HJ Demski S Jacobi B Kuznik B Mayer R Meyer H Möller R Schubnell M Seyffert B Wei Y Wintgen P 《Physical review D: Particles and fields》1989,40(7):2163-2171
998.
Event rates and distributions for high mass gluinos and squarks are computed at Tevatron collider energies, imposing experimentally realisticP T cuts. Gluino and squark masses can be probed up to 200 GeV at \(\sqrt s = 2 TeV\) , and up to about 150 GeV at \(\sqrt s = 1.6 TeV\) with the supersymmetric signal being much more enhanced relative to the standard model background than at CERN \(\bar p\) energies. If the CERN UA1 missing-p T events are indeed indicative for the existence of gluinos and/or squarks with masses of about 50–70 GeV, then the Fermilab collider experiments should easily confirm the expected huge supersymmetric signals. 相似文献
999.
In this paper we present a comparative study of inelastic interactions of C12-Em and p-Em at 4·5 GeV/c per nucleon. The multiplicity distributions and their correlations have been studied. The results show a strong correlation of n
s onn
h in the case of C12-Em but not in the case of p-Em. It is also shown that the n
s increases with the increase of the projectile mass. The angular distribution of the target fragments in C12-Em shows a massive forward collimation. Comparison is also made in the pseudorapidity distribution of both C12-Em and p-Em, the result shows many interesting features. 相似文献
1000.
Somnath Roy Tarak Nath Mandal Anil Kumar Barik Sachindranath Pal Samik Gupta Arijit Hazra Ray J. Butcher Allen D. Hunter Matthias Zeller Susanta Kumar Kar 《Polyhedron》2007
Two new pyrimidine based NNS tridentate Schiff base ligands S-methyl-3-((2-S-methyl-6-methyl-4-pyrimidyl)methyl)dithiocarbazate [HL1] and S-benzyl-3-((2-S-methyl-6-methyl-4-pyrimidyl)methyl)dithiocarbazate [HL2] have been synthesised by the 1:1 condensation of 2-S-methylmercapto-6-methylpyrimidine-4-carbaldehyde and S-methyl/S-benzyl dithiocarbazate. A Ni(II) complex of HL1 and Co(III) and Fe(III) complexes of HL2 have been prepared and characterized by elemental analyses, molar conductivities, magnetic susceptibilities and spectroscopic studies. All the bis-chelate complexes have a distorted octahedral arrangement with an N4S2 chromophore around the central metal ion. Each ligand molecule binds the metal ion using the pyrimidyl and azomethine nitrogen and thiolato sulfur atoms (except in the nickel complex, one ligand molecule uses the thione sulfur in lieu of thiolato sulfur atom). In the Ni(II) complex, one of the ligand molecules behaves as a neutral tridentate and the other molecule functions as a uninegative tridentate, whereas in the Co(III) and Fe(III) complexes, the ligand molecules behave as monoanionic tridentate. All the complexes were analyzed by single crystal X-ray diffraction and significant differences concerning the distortion from an octahedral geometry of the coordination environment were observed. 相似文献