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971.
We describe a novel microscopy technique for quantitative phase-contrast imaging of a transparent specimen. The technique is based on depth-resolved phase information provided by common path spectral-domain optical coherence tomography and can measure minute phase variations caused by changes in refractive index and thickness inside the specimen. We demonstrate subnanometer level path-length sensitivity and present images obtained on reflection from a known phase object and human epithelial cheek cells. 相似文献
972.
We present a novel approach to generating radially and azimuthally polarized vector beams that utilize an interferometer constructed from two identical diffractive optical elements. The measured polarization properties of four vector beam states and their phase relationships are in good agreement with theoretical expectations. This interferometer is passively phase stable and robust, making it suitable for linear and nonlinear optical (superresolution) microscopy. 相似文献
973.
Based on first-principles calculations, a model for large-size-mismatched group-V dopants in ZnO is proposed. The dopants do not occupy the O sites as is widely perceived, but rather the Zn sites: each forms a complex with two spontaneously induced Zn vacancies in a process that involves fivefold As coordination. Moreover, an As(Zn)-2V(Zn) complex may have lower formation energy than any of the parent defects. Our model agrees with the recent observations that both As and Sb have low acceptor-ionization energies and that to obtain p-type ZnO requires O-rich growth or annealing conditions. 相似文献
974.
Asner DM Dytman SA Mehrabyan S Mueller JA Nam S Savinov V Huang GS Miller DH Pavlunin V Sanghi B Shibata EI Shipsey IP Adams GS Chasse M Cummings JP Danko I Napolitano J Cronin-Hennessy D Park CS Park W Thayer JB Thorndike EH Coan TE Gao YS Liu F Stroynowski R Artuso M Boulahouache C Blusk S Butt J Dambasuren E Dorjkhaidav O Haynes J Menaa N Mountain R Muramatsu H Nandakumar R Redjimi R Sia R Skwarnicki T Stone S Wang JC Zhang K Mahmood AH Csorna SE Bonvicini G Cinabro D Dubrovin M Bornheim A 《Physical review letters》2004,92(14):142001
We report on the observation of the eta(')(c)(2(1)S0), the radial excitation of the eta(c)(1(1)S0) ground state of charmonium, in the two-photon fusion reaction gammagamma-->eta(')(c)-->K(0)(S)K+/-pi(-/+) in 13.6 fb(-1) of CLEO II/II.V data and 13.1 fb(-1) of CLEO III data. We obtain M(eta(')(c))=3642.9+/-3.1(stat)+/-1.5(syst) MeV and M(eta(c))=2981.8+/-1.3(stat)+/-1.5(syst) MeV. The corresponding values of hyperfine splittings between 1S0 and 3S1 states are DeltaM(hf)(1S)=115.1+/-2.0 MeV and DeltaM(hf)(2S)=43.1+/-3.4 MeV. Assuming that the eta(c) and eta(')(c) have equal branching fractions to K(S)Kpi, we obtain Gamma(gammagamma)(eta(')(c))=1.3+/-0.6 keV. 相似文献
975.
A one-dimensional system of Si(111)-(5 x 2)-Au is explored using scanning tunneling microscopy and spectroscopy. The chain of Si adatoms called bright protrusions (BP's) is found to be semiconducting with an evanescent state in the gap, which originates from adjoining metallic BP-free segments. A quantitative analysis shows that the evanescent state decays in inverse-Gaussian form, leading to an appearance of a parabolic BP chain, and scales to its chain length. Spatial decay of the state suggests a quadratic band bending and the existence of a Schottky-like potential barrier at the interface driven by charge transfer. 相似文献
976.
977.
978.
Monolayers of cubic zeolite microcrystals (1.7 x 1.7 x 1.7 and 0.3 x 0.3 x 0.3 mum3) were assembled on glass plates through imine- or urethane-linkages between the zeolite-tethered 3-aminopropyl (AP) groups and the glass-bound benzaldehyde or isocyanate groups, which were prepared by treating AP-tethering glass plates with a large excess of terephthaldicarboxaldehyde (TPDA) or 1,4-diisocyanatobutane (DICB), respectively, in toluene. The additional treatment of the monolayers of zeolite microcrystals with TPDA or DICB led to lateral molecular cross-linking between the neighboring, closely packed zeolite microcrystals in the monolayers through AP-TPDA-AP imine or AP-DICB-AP urethane linkages between the zeolite-tethered AP groups and the newly introduced TPDA or DICB, respectively. The comparison of the binding strengths between the glass substrates and the monolayers revealed that the molecular cross-linking leads to as much as 7- and 38-fold (by average) increase in the binding strength in the cases of 1.7 x 1.7 x 1.7 and 0.3 x 0.3 x 0.3 mum3 crystals, respectively. We predict that the effect of lateral cross-linking on the binding strength will further increase with further decreasing the size of the building blocks to nanoparticles and to molecules. 相似文献
979.
J.S.?Bae Y.H.?Kim J.K.?Jang K.S.?Shim J.K.?Lee J.H.?JeongEmail author S.S.?Yi H.L.?Park 《Applied Physics A: Materials Science & Processing》2004,78(7):1073-1077
Mn-doped ZnGa2O4-xSx thin-film phosphors have been grown using a pulsed laser deposition technique at varying growth conditions. Structural characterization was carried out on a series of ZnGa2O4-xSx:Mn2+ films grown on MgO(100) substrates using Zn-rich ceramic targets. Oxygen pressure was fixed at 100 mTorr and substrate temperatures were varied from 500 to 700 °C. The results of X-ray-diffraction patterns showed that the lattice constants of the ZnGa2O3.95S0.05:Mn2+ thin films decrease with the substitution of sulfur for the oxygen in ZnGa2O4. Measurements of photoluminescence (PL) properties of ZnGa2O4-xSx:Mn2+ thin films have indicated that MgO(100) is one of the most promising substrates for the growth of high-quality ZnGa2O4-xSx:Mn2+ thin films. In particular, the incorporation of sulfur into the ZnGa2O4 lattice could induce a remarkable increase of PL. The highest green-emission intensity was observed with ZnGa2O3.95S0.05:Mn2+ films, whose brightness was increased by a factor of 3.5 in comparison with that of ZnGa2O4:Mn2+ films. This phosphor may be promising for application to flat-panel displays. PACS 78.20.-e; 78.55.-m; 78.66.-w 相似文献
980.
The design of synthetic agents to disrupt protein-protein interactions has received relatively little attention in recent years. In this review we describe strategies for targeting different types of protein surfaces using mimetics of protein secondary or tertiary structure. In this way strong and selective binding to a protein surface has be achieved and disruption of clinically important protein-protein interactions has been demonstrated in models of human disease. 相似文献