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961.
Paul Seiler 《Helvetica chimica acta》1990,73(6):1574-1585
The molecular structure of [1.1.1]propellane has been determined from single-crystal X-ray diffraction measurements at 138 K. The crystals of this reactive compound were grown from the melt at ca. 263 K. The space group is C2, and the asymmetric unit contains four molecules. All have large thermal motion and two show orientational disorder as well. Because of these problems, the atomic positions cannot be determined with high accuracy. Within the experimental limits, the two ordered molecules have D3h symmetry, with corrected lengths of central and side bonds of ca. 1.60 Å and 1.53 Å, respectively. At lower temperature, the crystals undergo a phase transition. The transition temperature, in the range of 100 to 132 K, varied from one crystal sample to another. All crystals obtained of the low-temperature phase were twinned, and its space group could not be established. 相似文献
962.
Bernhard Neumüller My-Linh Ha-Eierdanz Ulrich Müller Sylvia Magull Gertrud Kruter Kurt Dehnicke 《无机化学与普通化学杂志》1992,609(3):12-18
Syntheses and Crystal Structures of the Polyselenido Complexes (PPh4)6[M(Se4)2]2[WSe4] · DMF with M = Zinc and Mercury The title compounds have been prepared by the reactions of the acetates of zinc and mercury, respectively, with excess (PPh4)2 WSe4 in boiling dimethylformamide, forming black-red single crystals. According to the X-ray structure determinations both compounds crystallize isotypically in the space group 12/a with four formula units per unit cell. (PPh4)6[Zn(Se4)2]2[WSe4] · DMF: a = 2888.1(6), b = 1740.3(2), c = 2893.9(4) pm, β = 90.47(1)°. 3230 observed unique reflections, R = 0.009. (PPh4)6[Hg(Se4)2]2[WSe4] · DMF: a = 2891.8(5), b = 1738.0(4), c = 2920.1(5) pm, β = 90.29(2)°. 2978 observed unique reflections, R = 0.115%. The compounds consist of PPh4+ ions, spirocyclic octaseleno metallates [M(Se4)2]2?, tetrahedral WSe42-ions, and disordered DMF Molecules. 相似文献
963.
Kurt Rossmanith 《Monatshefte für Chemie / Chemical Monthly》1983,114(4):407-409
The effective distribution coefficients of the cerium earth nitrates were determined with input of 100 g oxide, while those of the yttrium earths were estimated from former work. The values rise to a maximum at Dy, then decrease from Ho to Yb. The separation of cerium earths from each other was distinctly better with 11M HNO3 than with 4M HNO3. 相似文献
964.
Reiner Figge Ute Patt-Siebel Elke Conradi Ulrich Müller Kurt Dehnicke 《无机化学与普通化学杂志》1988,558(1):107-113
Synthesis, I.R. Spectrum, and Crystal Structure of PPh4[OsCl4(NO)(NSCl)] Molten trithiazyl chloride reacts with OsCl3(NO) to yield a product mixture consisting mainly of S4N3[OsCl4(NO)(NSCl)] and S4N3Cl. Extraction of this mixture with a solution of tetraphenylphosphonium chloride in dichloromethane affords green (PPh4)2[OsCl5(NO)] · 2 CH2Cl2 and the red title compound. PPh4[OsCl4(NO)(NSCl)] was characterized by its IR spectrum and an X-ray crystal structure analysis (3001 independent observed reflexions, R = 0.048). Crystal data: monoclinic, space group P21/c, Z = 4, a = 1716, b = 1054, c = 1588 pm, β = 96.25°. The compound consists of PPh4⊕ cations and [OsCl4(NO)(NSCl)]? anions in which the nitrosyl and the chlorothionitrene ligands have a cis arrangement. Due to positional disorder the NO and NSCl groups are superimposed statistically in the structure model. 相似文献
965.
Sabine Schlecht Naim Faza Werner Massa Frank Weller Kurt Dehnicke 《无机化学与普通化学杂志》1997,623(11):1739-1743
Synthesis and Crystal Structures of the Silylated λ5-Phosphazenes R? C(CH2PPh2NSiMe3)3 with R = H and CH3 The title compounds are obtained by Staudinger reaction from the corresponding tripodal phosphanes R? C(CH2PPh2)3 and trimethylsilylazide. Both complexes are characterized by their IR and NMR spectra and by crystal structure analyses. H? C(CH2PPh2NSiMe3)3 ( 1 ): Space group P21/c, Z = 4, structure determination with 7833 independent reflections, R = 0.055. Lattice dimensions at ?50°C: a = 1399.5, b = 2311.4, c = 1678.9 pm, β = 112.92°. CH3? C(CH2PPh2NSiMe3)3 ( 2 ): Space group P1 , Z = 2, structure determination with 9251 independent reflections, R = 0.057. Lattice dimensions at ?50°C: a = 1276.5, b = 1386.9, c = 1790.2 pm; α = 85.55°, β = 69.39°, γ = 62.99°. 1 and 2 form monomeric molecules which are distinguished by their conformation. 相似文献
966.
Werner M. Dÿck Kurt Dehnicke Gisela Beyendorff-Gulba Joachim Strhle 《无机化学与普通化学杂志》1981,482(11):113-120
Azido Complexes of Zirconium: ZrCl3N3, [ZrCl4N3]22?, [ZrCl4(N3)2]2?; Crystal Structure of (PPh4)2 [ZrCl4N3]2 Highly explosive ZrCl3N3 is formed by the reaction of ZrCl4 with iodine azide in dichloromethane suspension. According to the i.r. spectra, the compound is polymeric by azide and chlorine bridges. Zirconium tetrachloride reacts with one and two moles of tetraphenylphosphonium azide respectively, forming the thermally and mechanically stable complexes (PPh4)2[ZrCl4N3]2 and (PPh4)2[ZrCl4(N3)2]. The crystal structure of (PPh4)2[ZrCl4N3]2 was determined by X-ray methods (1942 reflexions, R = 6.5%). The complex crystallizes in the monoclinic space group P21/n with two formula units per unit cell. The structure consists of tetraphenylphosphonium cations and dimeric anions [ZrCl4N3]22?, in which the Zr atoms are linked by the α-N atoms of the azide groups, forming a centrosymmetric Zr2N2 ring with symmetry D2h. According to the i.r. spectra, the azide groups in the complex (PPh4)2[ZrCl4(N3)2] are covalently bonded at the Zr atom in trans positions. 相似文献
967.
Bela P. Ruzsicska Silvia E. Braslavsky Kurt Schaffner 《Photochemistry and photobiology》1985,41(6):681-688
A comparative study of the decay kinetics of photogenerated transients from small (60 kDalton) and native (124 kDalton) oat phytochrome in the red-absorbing form (Pr) in phosphate buffer containing 5 mM ethylenediamine tetraacetic acid, pH 7.8, (PB) and in PB containing 20% ethylene glycol, has been carried out in the temperature range 275–298 K. The analysis confirmed that at least two primary photoproducts, intermediates Ii700s and Ii7oo are formed from Pr. The kinetic parameters, as observed in PB at 695 nm and 275 K, are similar for the I700 intermediates of both small and native phytochrome. Namely, the lifetimes are about 21 μs (component percentages 38%) for the I Ii700s and about 200 μ.s (62%) for the Ii700S- Arrhenius preexponential factors (A) of about 1016 and 1015 s-1and activation energies of about 61 and 56 kJ/mol were measured for the absorbance decays of the I700S of small and native phytochrome, respectively. The kinetic data favour parallel paths for the formation of the Ii700s from Pr, and the activation parameters indicate that the primary photoreactions of the transformation from Pr to the far-red-absorbing form are restricted to the chromophore within the protein. Moreover, the relatively modest temperature dependence of the lifetimes of the Ii700S from small and native Pr supports the working hypothesis that the ground state reactions to the Iibl, intermediates–although somewhat influenced by the polypeptide fragment that is removed upon degradation of native to small Pr–are localized to the chromophore, as is most probably the case also for the primary photoreactions. The effect of the addition of 20% ethylene glycol on the pre-exponential factors of the time-dependent decay functions is discussed in similar terms of the early stages of the phototransformation. 相似文献
968.
Barbara Szczepaniak Kurt C. Frisch Piotr Penczek Jerzy Mejsner Irena Leszczyska Ewa Rudnik 《Journal of polymer science. Part A, Polymer chemistry》1993,31(13):3223-3230
Previous studies on liquid crystalline polyurethanes prepared from 4,4′-bis(2-hydroxyethoxy)biphenyl (BHBP) and 2,4-tolylene diisocyanate (TDI) were continued. In this article, a series of polyurethanes, which differ in the flexible spacer length and BHBP content is described. Poly(oxytetramethylene)diols of different molecular weights (PTMO, M n = 250, 650, 1000, 2000) were used as flexible spacers. The polyurethanes were investigated by DSC, polarizing microscopy, x-ray diffractometry, and IR spectroscopy. The molecular weight distribution was determined by GPC. The morphology of the polyurethanes was investigated by the SALS method. Partial replacement of BHBP by 25–75 mol % PTMO and the flexible spacer length influence the liquid crystalline properties, the phase transition temperatures, and the range of mesophase occurrence. © 1993 John Wiley & Sons, Inc. 相似文献
969.
Kurt L. Komarek Peter Matyas Johann Mikler 《Monatshefte für Chemie / Chemical Monthly》1975,106(1):73-84
The enthalpies of formation of solid Co?Te alloys were determined at room temperature with an isoperibol solution calorimeter of the submarine type. Co?Te alloys and mechanical mixtures of the pure components were dissolved in separate experiments in a saturated hydrochloric acid (8.000n)—bromine mixture and the enthalpies of formation obtained by difference. For the NiAs-type β-phase ΔH f o(NTe)=(4.079–15.017N Te) kcal·g-atom?1 and for the marcasitetype γ-phase ΔH f o(N Te)=(3.787–14.400N Te) kcal·g-atom?1. Combining these results with data from the literature integral thermodynamic properties of solid Co—Te alloys were calculated at room temperature and at 600°C. 相似文献
970.
Turkusic E Kalcher J Kahrovic E Beyene NW Moderegger H Sofic E Begic S Kalcher K 《Talanta》2005,65(2):559-564
A screen-printed amperometric biosensor based on carbon ink double bulk-modified with MnO2 as a mediator and glucose oxidase as a biocomponent was investigated for its ability to serve as a detector for bonded glucose in different compounds, such as cellobiose, saccharose, (-)-4-nitrophenyl-β-d-glucopyranoside, as well as in beer samples by flow-injection analysis (FIA). The biosensor could be operated under physiological conditions (0.1 M phosphate buffer, pH 7.5) and exhibited good reproducibility and stability. Bonded glucose was released with glucosidase in solution, and the free glucose was detected with the modified screen-printed electrode (SPE). The release of glucose by the aid of glucosidase from cellobiose, saccharose and (-)-4-nitrophenyl-β-d-glucopyranoside in solution showed that stoichiometric quantities of free glucose could be monitored in all three cases.The linear range of the amperometric response of the biosensor in the FIA-mode flow rate 0.2 mL min−1, injection volume 0.25 mL, operation potential 0.48 V versus Ag/AgCl) extends from 11 to 13,900 μmol L−1 glucose in free form. The limit of detection (3σ) is 1 μmol L−1 glucose. A concentration of 100 μmol L−1 yields a relative standard deviation of approximately 7% with five injections. These values correspond to the same concentrations of bonded glucose supposed that it is liberated quantitatively (incubation for 2 h with glucosidase).Bonded glucose could be determined in beer samples using the same assay. The results corresponded very well with the reference procedure. 相似文献