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211.
Murine splenic B lymphocytes are induced to proliferate and undergo polyclonal activation in the presence of Fc fragments, AHGG, antigen-antibody complexes, and CH3 fragments derived from plasmin digestion of human Ig. The unifying feature of the polyclonal antibody response induced by these agents is that in all cases a portion of the constant region of the Ig molecule (ie, Fc region) is present. Fragments of Ig lacking the Fc piece, such as Fab and F(ab)2 were found not to be stimulatory. In addition, a model is proposed to account for the regulatory effects of antigen-antibody complexes on an ongoing humoral immune response. 相似文献
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Relatively large amounts of alkylated derivatives of the polynuclear aromatic hydrocarbons are present in some urban atmospheres. These compounds are believed to be derived from industrial sources. Because alkylation of the tetracyclic aromatic hydrocarbons can confer carcinogenic activity on the derivatives, the presence of substantial amounts of these alkylated compounds in the air needs thorough study. The R(F) value and the retention time, by themselves, are inadequate for characterisation of the polynuclear compounds. Gasliquid chromatography followed by fluorometric examination of the eluent bands, and mixed-adsorbent two-dimensional thin-layer chromatography followed by direct fluorometric examination are very useful in characterising all types of organic compound in the organic fractions of airborne particulates and effluents from air pollution sources. 相似文献
215.
Several improvements are made to available computer programs for calculating formation constants from pH data. The most important features are wide portability of program among computers, ability to optimize any parameter in the model equations and to fix any parameters (including stepwise formation constants) to a constant, and options to allow for variations in thermodynamic activity of ions and to fit pH after fitting the volume of added reagent. The latter feature was used with synthetic data to explore the effects of random errors in either reagent volume or pH or both. Whereas fits to reagent volume will usually be more accurate for systems with pKa values near 7, this is not the case for systems with pKa values which differ by > 2.0 from 7. 相似文献
216.
Steven H. Selman James A. Hampton Alan R. Morgan Rick W. Keck AdamD. Balkany Dimitris Skalkos 《Photochemistry and photobiology》1993,57(4):681-685
Abstract— An iminum salt of octaethylbenzochlorin with copper in the aromatic ring, CDSI, was tested for its tumoricidal effects on theA–27 N-[4-(5-notro-2-furyl)-2-thiazoly] formamide tumor line. CDSI was found to be an effective photosensitiz4r in vivo when used in combination with either a xenon arc lamp or a pulsed alexandrite laser. Hemodynamically, CDSI and light caused a rapid decrease in tumor blood flow. skin photosensitization was found to be minimal when drug-injected mice werwe illuminated in a solar simulator. 相似文献
217.
David L. Morgan Jr. 《Hyperfine Interactions》1993,76(1):347-352
In the scattering of negative particles other than the electron by atoms at lab-frame energies around 10 eV, an elastic process
termed “brickwall scattering” might lead to a high probability for scattering angles around 180°. For an antiproton slowing
in hydrogen, this backward scattering would result in the loss of nearly all of its energy in a single collision, since it
and a hydrogen atom have nearly the same mass. Such energy loss would have a significant effect on the energy distribution
of antiprotons at energies where capture by the protons of hydrogen is possible and might, thereby, affect the capture rate
and the distribution of capture states. In the semiclassical treatment of the problem with an adiabatic potential energy,
brickwall scattering is indeed present, and with a substantial cross section. However, this model appears to underestimate
inelastic processes. Based on calculations for negative muons on hydrogen atoms, these processes appear to occur for about
the same impact parameters as brickwall scattering and thus substantially reduce its effect. 相似文献
218.
Asymptotic expansions have long found utility in quantum field theoretical studies of statistical mechanics. In this context a generalized Laplace formula is discussed and the technique is illustrated by applying it to a simple quantum Hamiltonian spin system. 相似文献
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Aubert B Barate R Bona M Boutigny D Couderc F Karyotakis Y Lees JP Poireau V Tisserand V Zghiche A Grauges E Palano A Chen JC Qi ND Rong G Wang P Zhu YS Eigen G Ofte I Stugu B Abrams GS Battaglia M Brown DN Button-Shafer J Cahn RN Charles E Gill MS Groysman Y Jacobsen RG Kadyk JA Kerth LT Kolomensky YG Kukartsev G Lynch G Mir LM Orimoto TJ Pripstein M Roe NA Ronan MT Wenzel WA del Amo Sanchez P Barrett M Ford KE Harrison TJ Hart AJ Hawkes CM Morgan SE Watson AT Held T Koch H Lewandowski B 《Physical review letters》2006,97(21):211801
We report a measurement of the B-->pi l nu branching fraction based on 211 fb(-1) of data collected with the BABAR detector. We use samples of B0 and B+ mesons tagged by a second B meson reconstructed in a semileptonic or hadronic decay and combine the results assuming isospin symmetry to obtain B(B(0)-->pi- l+ nu) = (1.33+/-0.17stat+/-0.11syst) x 10(-4). We determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element absolute value V(ub) by combining the partial branching fractions measured in ranges of the momentum transfer squared and theoretical calculations of the form factor. Using a recent lattice QCD calculation, we find absolute value V(ub) = (4.5+/-0.5stat+/-0.3syst(+0.7) -0.5FF x 10(-3), where the last error is due to the normalization of the form factor. 相似文献