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21.
Induction of Chromosome Aberrations and Delayed Genomic Instability by Photochemical Processes 总被引:1,自引:0,他引:1
Charles L. Limoli Joseph P. Day John F. Ward William F. Morgan 《Photochemistry and photobiology》1998,67(2):233-238
Exponentially growing cells cultured in medium containing bromodeoxyuridine, then exposed to UVA light in the presence of the dye Hoechst 33258, show significant levels of DNA strand breaks and base damage. This dye–bromodeoxyuridine–UVA photolysis treatment is markedly cytotoxic. We now demonstrate that exposure of cells to the agents used in photolysis leads directly to the formation of chromosome aberrations. Furthermore, we demonstrate that this photochemical treatment induces delayed chromosomal instability in clonal populations derived from single progenitor cells surviving photolysis. These results suggest that photolysis-induced DNA damage leads to chromosome rearrangements that could account for the observed cytotoxicity. Furthermore, in those cells surviving photolysis, the delayed effects of this treatment can be observed several generations after exposure and are manifested as compromised genomic integrity. 相似文献
22.
DTA curves were run for the ethylenebisdithiocarbamate fungicides maneb, mancozeb and zineb in a nitrogen atmosphere. Zineb produces a curve quite different from the others, with weak endothermic peaks at 166°C, 252°C and 293°C. Maneb and mancozeb have a relatively strong endothermic peak at 185–190°C corresponding to carbon disulphide evolution and a weaker endothemic peak at 290°C corresponding to hydrogen sulphide evolution. Maneb samples and some mancozeb samples also had a minor endothermic peak at 235°C, but this peak was lost after solvent extraction, which proved that it was due to an impurity or impurities. Elemental sulphur was found in the extract and on mixing sulphur with mancozeb, the peak at 235°C made its appearance. There is no distinguishing feature between the DTA curves for maneb and mancozeb. The shapes of the curves are, within experimental limits, indistinguishable, which means that the temperatures and energies of decomposition are the same. The chemist is left with the question whether differences in structure between maneb and mancozeb should lead to different DTA curves. 相似文献
23.
T. P. Fischer S. Shuttleworth P. A. O’Day 《Analytical and bioanalytical chemistry》1998,362(5):457-464
The accurate measurement of ultra-trace concentrations of rare metals and platinum group elements in volcanic fluids is complicated by interferences, complex matrices, and preferential element partitioning. We analyzed condensed, high-temperature magmatic fluids collected from Kudryavy volcano (Kurile Islands, Russia) for Be, B, Rb, Sr, Mo, Ru, Rh, Pd, Cd, W, Re, Pt, Pb, Bi, and U using ICP-MS. The samples had three different matrices: 5 mol L–1 sodium hydroxide (NaOH, pH = 11), gas condensates of sulfuric acid (H2SO4, pH = 0), and solid elemental sulfur. Interferences and suppression/enhancement effects were investigated using standards in concentrated NaOH and H2SO4 solutions to determine adequate dilution for sample analyses, which then required very low levels of element detection (< 1 μg L–1 for most elements). Depending on the field sampling technique of volcanic gas vents, our results show significant differences in concentrations of some trace elements due to the precipitation of solid sulfur during gas condensation and variations in element volatility as a function of temperature. 相似文献
24.
Joseph A. Rard Kirk J. Staggs S. Dan Day Susan A. Carroll 《Journal of solution chemistry》2006,35(8):1187-1215
Boiling temperature measurements have been made at ambient pressure for saturated ternary solutions of NaCl + KNO3 + H2O, NaNO3 + KNO3 + H2O, and NaCl + Ca(NO3)2 + H2O over the full composition range, along with those of the single salt systems. Boiling temperatures were also measured for the four component NaCl + NaNO3 + KNO3 + H2O and five component NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O mixtures, where the solute mole fraction of Ca(NO3)2, x{Ca(NO3)2}, was varied between 0 and 0.25. The maximum boiling temperature found for the NaCl + KNO3 + H2O system is ≈134.9 ∘C; for the NaNO3 + KNO3 + H2O system is ≈165.1 ∘C at x(NaNO3) ≈ 0.46 and x(KNO3) ≈ 0.54; and for the NaCl + Ca(NO3)2 + H2O system is 164.7 ± 0.6 ∘C at x{NaCl} ≈ 0.25 and x{Ca(NO3)2} ≈ 0.75. The NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O system forms molten salts below their maximum boiling temperatures and the temperatures corresponding to the cessation of boiling (dry-out temperatures) of these liquid mixtures were determined. These dry-out temperatures range from ≈300 ∘C when x{Ca(NO3)2} = 0 to ≥ 400 ∘C when x{Ca(NO3)2} = 0.20 and 0.25. Mutual deliquescence/efflorescence relative humidity (MDRH/MERH) measurements were also made for the NaNO3 + KNO3 and NaCl + NaNO3 + KNO3 salt mixture from 120 to 180 ∘C at ambient pressure. The NaNO3 + KNO3 salt mixture has a MDRH of 26.4% at 120 ∘C and 20.0% at 150 ∘C. This salt mixture also absorbs water at 180 ∘C, which is higher than expected from the boiling temperature experiments. The NaCl + NaNO3 + KNO3 salt mixture was found to have a MDRH of 25.9% at 120 ∘C and 10.5% at 180 ∘C. The investigated mixture compositions correspond to some of the major mineral assemblages that are predicted to control brine composition due to the deliquescence of salts formed in dust deposited on waste canisters in the proposed nuclear repository at Yucca Mountain, Nevada. 相似文献
25.
Chen JP Meziani ZE Beck D Boyd G Chinitz LM Day DB Dennis LC Dodge G Filippone BW Giovanetti KL Jourdan J Kemper KW Koh T Lorenzon W McCarthy JS McKeown RD Milner RG Minehart RC Morgenstern J Mougey J Potterveld DH Rondon-Aramayo OA Sealock RM Smith LC Thornton ST Walker RC Woodward C 《Physical review letters》1991,66(10):1283-1286
26.
Three novel coordination polymers built of octahedral niobium cyanochloride clusters [Nb6Cl12(CN)6] and alkaline earth metal complexes have been prepared by reaction of aqueous solutions of (Me4N)4Nb6Cl18 and KCN with solutions of alkaline earth metal salts and 1,10-phenanthroline (phen) (1:2 molar ratio) in H2O/EtOH. The structures of [Ca(phen)2(H2O)3]2[Nb6Cl12(CN)6] x (phen)(EtOH)1.6 (1), [Ca(phen)2(H2O)2]2[Nb6Cl12(CN)6] x (phen)2 x 4H2O (2), and [Ba(phen)2(H2O)]2[Nb6Cl12(CN)6] (3) were determined by single-crystal X-ray diffraction. The three compounds were found to crystallize in the monoclinic system (space group Pn) with a = 11.5499(6) A, b = 17.5305(8) A, c = 21.784(1) A, beta = 100.877(1) degrees for 1; triclinic system (P1) with a = 12.609(4) A, b = 13.262(4) A, c = 16.645(5) A, alpha = 69.933(6) degrees, beta = 68.607(6) degrees, gamma = 63.522(5) degrees for 2; and a = 16.057(1) A, b = 16.063(1) A, c = 16.061(1) A, alpha = 86.830(1) degrees, beta = 64.380(1) degrees, gamma = 67.803(1) degrees for 3. Compounds 1 and 2 are built of cluster anions [Nb6Cl12(CN)6]4- trans-coordinated by two Ca2+ complexes via CN ligands to form neutral macromolecular units [Ca(phen)2(H2O)3]2[Nb6Cl12(CN)6] in 1 and [Ca(phen)2(H2O)2]2[Nb6Cl12(CN)6] in 2. Water of coordination and cyanide ligands form hydrogen bonded 3D and 2D frameworks for 1 and 2, respectively. The structure of 3 consists of [Nb6Cl12(CN)6]4- cluster anions and [Ba(phen)2(H2O)]2+ complexes linked through bridging cyanide ligands to form a neutral three-dimensional framework in which each barium complex is bound to three neighboring Nb6 clusters and each Nb6 cluster is linked to six Ba complexes. 相似文献
27.
In this study, sugarcane bagasse was pretreated with ammonium hydroxide, and the effectiveness of the pretreatment on enzyme hydrolysis and ethanol production was examined. Bagasse was soaked in ammonium hydroxide and water at a ratio of 1:0.5:8 for 0–4 days at 70 °C. Approximately, 14–45 % lignin, 2–6 % cellulose, and 13–22 % hemicellulose were removed during a 0.5- to 4-day ammonia soaking period. The highest glucan conversion of sugarcane bagasse soaked in dilute ammonia at moderate temperature by cellulase was accomplished at 78 % with 75 % of the theoretical ethanol yield. Under the same conditions, untreated bagasse resulted in a cellulose digestibility of 29 and 27 % of the theoretical ethanol yield. The increased enzymatic digestibility and ethanol yields after dilute ammonia pretreatment was related to a combined effect of the removal of lignin and increase in the surface area of fibers. 相似文献
28.
Orville W. Day 《International journal of quantum chemistry》1996,57(3):391-399
The wave function of a system may be expanded in terms of eigenfunctions of the N −1 electron Hamiltonian times one-particle functions known as generalized overlap amplitudes (GOAS). The one-electron operator whose eigenfunctions are the GOAS is presented, without using an energy-dependent term as in the one-particle Green function or propagator approach. It is shown that this operator and the extended Koopmans' theorem (EKT) one-electron operator are of similar form, but perform complementary roles. The GOA operator begins with one-electron densities and total energies of N −1 electron states to generate the two-matrix and total energy of an N-electron state. The EKT operator begins with the two-matrix of an N-electron state to generate one-electron densities and ionization potentials (or approximations thereto) for N −1 electron states. However, whereas the EKT orbitals must be linearly independent, no such restriction applies to the GOAS. © 1996 John Wiley & Sons, Inc. 相似文献
29.
Robert C. Morrison Jerry R. Mizell Orville W. Day 《International journal of quantum chemistry》1996,57(3):355-360
Generalized overlap amplitudes (GOAS) are calculated between the lithium atom and several states of Li+. An examination of the long-range behavior of the GOAS indicates that they are coupled, appearing to have the same exponential decay at large r. At intermediate distances from the nucleus, the GOAS decay with their unique exponential rate and the decay rates only merge at large r. Although many of the GOAS appear to be similar, their distinctness indicates that they may, in fact, be linearly independent. © 1996 John Wiley & Sons, Inc. 相似文献
30.
Wei Tong Robert C. Morrison Orville W. Day 《International journal of quantum chemistry》1996,60(7):1623-1631
Multireference configuration interaction wave functions with single and double excitations were calculated for the 1Σ+g ground state of the C2 molecule and the excited states of C+2 with symmetries 2Σ+g, 2Σ-u, 2Πu, and 2Πg. The corresponding σg, σu, πu, and πg valence Dyson orbitals were calculated. Most of the density due to the valence electrons is accounted for by three σg, one σu, and one degenerate pair of πu Dyson orbitals. Electron correlation plays an important role in the bond strength of C2 by increasing the occupation of the σg valence orbitals and decreasing the occupation of the σu and πu valence orbitals. © 1996 John Wiley & Sons, Inc. 相似文献