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991.
Douglas S. Werner Hanqing Dong Mridula Kadalbajoo Radoslaw S. Laufer Paula A. Tavares-Greco Brian R. Volk Mark J. Mulvihill Andrew P. Crew 《Tetrahedron letters》2010,51(30):3899-515
The preparation of 5,7-disubstituted imidazo[5,1-f][1,2,4]triazin-4-amines, exemplified by 5-[3-(benzyloxy)phenyl]-7-cyclobutylimidazo[5,1-f][1,2,4]triazin-4-amine, was developed through a linear and three convergent synthetic strategies, with the latter providing the greatest flexibility for diversification at the 5-position at the last step of the synthesis. 相似文献
992.
We present an adaptable method to compute the solubility limit of solids by molecular simulation, which avoids the difficulty of reference state calculations. In this way, the method is highly adaptable to molecules of complex topology. Results are shown for solubility calculations of sodium chloride in water and light alcohols at atmospheric conditions. The pseudosupercritical path integration method is used to calculate the free energy of the solid and gives results that are in good agreement with previous studies that reference the Einstein crystal. For the solution phase calculations, the self-adaptive Wang-Landau transition-matrix Monte Carlo method is used within the context of an expanded isothermal-isobaric ensemble. The method shows rapid convergence properties and the uncertainty in the calculated chemical potential was 1% or less for all cases. The present study underpredicts the solubility limit of sodium chloride in water, suggesting a shortcoming of the molecular models. Importantly, the proper trend for the chemical potential in various solvents was captured, suggesting that relative solubilities can be computed by the method. 相似文献
993.
Clemens JB Chagarov EA Holland M Droopad R Shen J Kummel AC 《The Journal of chemical physics》2010,133(15):154704
The reaction of trimethyl aluminum on the group III rich reconstructions of InAs(0 0 1) and In(0.53)Ga(0.47)As(0?0?1) is observed with scanning tunneling microscopy/spectroscopy. At high coverage, a self-terminated ordered overlayer is observed that provides the monolayer nucleation density required for subnanometer thick transistor gate oxide scaling and removes the surface Fermi level pinning that is present on the clean InGaAs surface. Density functional theory simulations confirm that an adsorbate-induced reconstruction is the basis of the monolayer nucleation density and passivation. 相似文献
994.
Griffin JM Yates JR Berry AJ Wimperis S Ashbrook SE 《Journal of the American Chemical Society》2010,132(44):15651-15660
High-resolution (19)F magic angle spinning (MAS) NMR spectroscopy is used to study disorder and bonding in a crystalline solid. (19)F MAS NMR reveals four distinct F sites in a 50% fluorine-substituted deuterated hydrous magnesium silicate (clinohumite, 4Mg(2)SiO(4)·Mg(OD(1-x)F(x))(2) with x = 0.5), indicating extensive structural disorder. The four (19)F peaks can be assigned using density functional theory (DFT) calculations of NMR parameters for a number of structural models with a range of possible local F environments generated by F(-)/OH(-) substitution. These assignments are supported by two-dimensional (19)F double-quantum MAS NMR experiments that correlate F sites based on either spatial proximity (via dipolar couplings) or through-bond connectivity (via scalar, or J, couplings). The observation of (19)F-(19)F J couplings is unexpected as the fluorines coordinate Mg atoms and the Mg-F interaction is normally considered to be ionic in character (i.e., there is no formal F-Mg-F covalent bonding arrangement). However, DFT calculations predict significant (19)F-(19)F J couplings, and these are in good agreement with the splittings observed in a (19)F J-resolved MAS NMR experiment. The existence of these J couplings is discussed in relation to both the nature of bonding in the solid state and the occurrence of so-called "through-space" (19)F-(19)F J couplings in solution. Finally, we note that we have found similar structural disorder and spin-spin interactions in both synthetic and naturally occurring clinohumite samples. 相似文献
995.
Kamphuis MM Johnston AP Such GK Dam HH Evans RA Scott AM Nice EC Heath JK Caruso F 《Journal of the American Chemical Society》2010,132(45):15881-15883
Targeted delivery of drugs to specific cells allows a high therapeutic dose to be delivered to the target site with minimal harmful side effects. Combining targeting molecules with nanoengineered drug carriers, such as polymer capsules, micelles and polymersomes, has significant potential to improve the therapeutic delivery and index of a range of drugs. We present a general approach for functionalization of low-fouling, nanoengineered polymer capsules with antibodies using click chemistry. We demonstrate that antibody (Ab)-functionalized capsules specifically bind to colorectal cancer cells even when the target cells constitute less than 0.1% of the total cell population. This precise targeting offers promise for drug delivery applications. 相似文献
996.
Maher TR Spaeth AD Neal BM Berrie CL Thompson WH Day VW Barybin MV 《Journal of the American Chemical Society》2010,132(45):15924-15926
The key step in accessing the title species (5), the first nonbenzenoid diisocyanobiaryl, involved an unexpected homocoupling of a 6-bromoazulene derivative. The reversible 2e(-) reduction of 5 was addressed electrochemically and computationally. The shifts in energies of the S(0)→S(1) and S(0)→S(2) transitions for a series of related 6,6'-biazulenyl derivatives correlate with the e(-)-donating/-withdrawing strength of their 2,2'-substituents but follow opposite trends. Species 5 adsorbs end-on (η(1)) to the Au(111) surface via one of its -NC groups to form a 2-nm-thick film. In addition, bimetallic coordination of 5's -NC termini can be readily achieved. 相似文献
997.
Sterically bulky monodentate and bidentate phosphines have been widely used as ligands for metal complexation and catalyst formation. Bulky tridentate phosphine ligands are however much rarer and have not been widely investigated even though they may be considered attractive ligands for coordination chemistry studies and catalysis. Here we report the synthesis of two new N-centred tripodal phosphine ligands bearing bulky cyclohexyl and tert-butyl groups. The coordination chemistry of the cyclohexyl triphosphine ligand N(CH2PCy2)3 (4) was investigated and found to react with Mo and W hexacarbonyls preferentially forming bidentate metal tetracarbonyl complexes [Mo(CO)4{N(CH2PCy2)3-κ2P}] (6) and [W(CO)4{N(CH2PCy2)3-κ2P}] (7) over the expected facial capping tridentate complexes. The steric bulk of the cyclohexyl groups on the phosphorus atoms is sufficient to prevent the third arm of the ligand from coordinating and adopting the required geometry for facial coordination. This ‘steric control’ at the metal centre results in the third arm remaining freely available for further metal coordination. The coordination chemistry of this free phosphine arm on complexes 6 and 7 was investigated further and used to prepare a series of gold, platinum and silver multimetallic complexes. The X-ray crystal structures of the resulting mixed bi and trimetallic complexes [W(CO)4{N(CH2PCy2)3-κ2P}AuCl] (8), [[Mo(CO)4{N(CH2PCy2)3-κ2P}]2(μ-PtCl2)] (9) and [[W(CO)4{N(CH2PCy2)3-κ2P}]2(μ-Ag)]ClO4 (11) are reported. 相似文献
998.
The photodynamic action of a novel photoactive polymer comprising covalently bound anthraquinone (AQ) moieties was evaluated after developing a methodology to reliably immobilize viable micro-organisms onto polymer film surfaces. The survival of Escherichia coli, Bacillus cereus (vegetative cells and spores), Fusarium oxysporum and Saccharomyces cerevisiae microbes inoculated on the surface of inert polymeric substrates was assessed to determine the effect of inoculum composition, drying rate and exposure to ultraviolet (UV-A) radiation. Their survival was highly dependent on microbial genus, with E. coli consistently displaying markedly shorter survival times than the other microbes, and B. cereus spores being the most resistant. Inoculation of the microbes onto the surface of the photoactive polymer films, followed by exposure to UV-A radiation, dramatically accelerated the inactivation of all microbial types studied compared with their survival on the surface of inert polymer substrates. Simultaneous exposure to both oxygen and UV-A radiation is required to affect cell survival, which is consistent with this effect most likely originating from the photoinduced production of singlet oxygen by the photoactive polymer. These results provide further compelling evidence that singlet oxygen produced exogenously by this photoactive polymeric substrate can successfully inactivate a broad spectrum of microbes on the substrate’s surface. 相似文献
999.
Reaction of 2,3-diaminopyridine with one equivalent of a functionalised vicinal diketone, in ethanol, yields a series of ligands based upon the pyrido[2,3-b]pyrazine core. The ligands were characterised by 1H, 13C–{1H} NMR, MS and UV–Vis spectroscopy. Reaction of the ligands with one equivalent of {ReBr(CO)5} gave a series of Re-Ln complexes based upon the general formula fac-{ReBr(CO)3(L)} (where L = pyrido[2,3-b]pyrazine-derived ligands, L1–L6). Solution IR studies confirmed the retention of the facially capped, tri-carbonyl coordination geometry at rhenium, and 1H NMR studies confirmed coordination of the ligand to Re(I). EI HR MS data were obtained for each complex confirming the proposed formulation and stoichiometry. Single crystal X-ray structures were obtained for three of the complexes (Re-L1, Re-L2, Re-L6), with each demonstrating that the ligands coordinate to Re(I) in a bidentate manner, via a four-membered chelate ring, which was unsymmetrical in the former two cases. The electronic absorption spectra of the complexes showed absorption into the visible region ca. 375–500 nm, (the complexes are orange-red in appearance). Following irradiation at 350–450 nm, the complexes display a solid-state broad emission peaking between 600–700 nm. The complexes were not sufficiently luminescent in solution to allow further investigation into the origin of this emission band, although with reference to related 1,8-naphthyridine complexes of Re(I) it is likely to incorporate significant 3MLCT character. 相似文献
1000.
Andrew D. Burnett Dr. John Kendrick Dr. John E. Cunningham Dr. Michael D. Hargreaves Dr. Tasmin Munshi Dr. Howell G. M. Edwards Prof. Edmund H. Linfield Prof. A. Giles Davies Prof. 《Chemphyschem》2010,11(2):368-378
The terahertz frequency spectrum of pentaerythritol tetranitrate (PETN) is calculated using Discover 1 with the COMPASS 2 force field, CASTEP[3] and PWscf. 4 The calculations are compared to each other and to terahertz spectra (0.3–3 THz) of crystalline PETN recorded at 4 K. A number of analysis methods are used to characterise the calculated normal modes. 相似文献