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951.
During the determination of zinc in a polluted stream by atomic-absorption with electrothermal atomization, chloride was found to exercise a large negative interference (40%) when a carbon-filament atomizer was used, but not when a graphite-furnace atomizer was used. The effect on the filament method was confirmed and shown to be due to the formation of zinc chloride, and further complicated by interaction of this with iron. This interference could be overcome by the use of aqueous ammonia solution or silver nitrate added as matrix modifier. The absence of interference in the graphite-furnace method is attributed to the liberation of hydrogen and removal of chloride as hydrogen chloride. It is further suggested that these observations offer a basis for the exploration of apparently contradictory reports in the literature. 相似文献
952.
Allen JM Brennessel WW Buss CE Ellis JE Minyaev ME Pink M Warnock GF Winzenburg ML Young VG 《Inorganic chemistry》2001,40(20):5279-5284
Reduction of Na[Ir(CO)4] by sodium metal in (Me2N)3PO, followed by treatment with liquid ammonia, provided high yields (ca. 90%) of unsolvated Na3[Ir(CO)3], a thermally stable, pyrophoric orange solid. This substance contains iridium in its lowest known formal oxidation state of -3 and has been characterized by IR spectroscopy, elemental analyses, and derivative chemistry, i.e., by its conversion to the triphenylgermyl and triphenylstannyl complexes, trans-[Ir(CO)3(EPh3)2](-), E = Ge, Sn. Single-crystal X-ray structures of the tetraethylammonium salts of these species, as well as [Co(CO)3(SnPh3)2](-), confirm the trigonal bipyramidal nature of the anions, originally predicted on the basis of their IR spectra in the carbonyl stretching frequency region. These structural characterizations provide important additional evidence for the presence of metal tricarbonyl units in Na3[M(CO)3], M = Co, Ir. 相似文献
953.
RbVSe2 has been synthesized at 773 K through the reaction of V and Se with a Rb2Se3 reactive flux. The compound crystallizes in the orthorhombic space group D2h24-Fddd with 16 formula units in a cell of dimensions , , and at . The structure possesses infinite one-dimensional chains of edge-sharing VSe4 tetrahedra separated from the Rb+ ions. These chains distort slightly to chains. The V-V distance within these chains is 2.8362(4) Å. First-principles total energy calculations indicate that a non-magnetic configuration for the V3+ cations is the most stable. 相似文献
954.
Lipton AS Bergquist C Parkin G Ellis PD 《Journal of the American Chemical Society》2003,125(13):3768-3772
The tris(pyrazolyl)hydroborato zinc complexes [Tp(But,Me)]ZnX (where X = Br, Cl, and OH) have been examined by low-temperature solid-state (67)Zn NMR spectroscopy. The value of the quadrupole coupling constant, Cq, for the zinc increased monotonically with the electronegativity of the bound substituent X, e.g., Br < Cl < OH. Calculations on the methylimidazole complex [(MeImH)(3)Zn(OH)](+) as a model for the active site of carbonic anhydrase indicate that the computed electric field gradient tensor is in good agreement with the experimental and calculated values for [Tp(But,Me)]ZnOH. 相似文献
955.
A. C. Ribes S. Damaskinos A. E. Dixon K. A. Ellis S. P. Duttaguptat P. M. Fauchet 《Progress in Surface Science》1995,50(1-4):295-304
High resolution, large area photoluminescence mapping with scanning stage microscopes has proven to be a useful, but slow, quality control technique for compound semiconductor wafers. This paper describes a confocal scanning beam MACROscope-Microscope which can image specimens up to 7.5×7.5 cm in size, in less than 10s, using reflected light, photoluminescence, and optical beam induced current. MACROscope mode provides 5 μm lateral resolution and 300 μm axial resolution. Microscope mode provides 0.25 μm lateral and 0.5 μm axial resolution, with a minimum field of view of 25×25 μm. This instrument can be used to evaluate preparation parameters involved in the manufacture of porous silicon as well as to provide quality control at a macroscopic and microscopic level for the fabrication of porous silicon specimens, wafers, detectors, and similar devices. A brief introduction to confocal microscopy and porous silicon is given. Several confocal and non-confocal photoluminescence and reflected-light images of a porous silicon wafer are shown at macroscopic and microscopic levels. A 3D profile of porous silicon structures reconstructed from confocal slices is also shown. 相似文献
956.
Laser-induced excitation and dispersed fluorescence spectra (originating from the 00, 21 and 31 vibrational levels of the
electronic state) of jet-cooled CdCH3 are presented and assigned. The observation of emission from these levels is a result having important implications for the dynamics of photodissociation of Cd(CH3)2. Fluorescence lifetimes for emission from the 00, 21 and 31 vibrational levels are also presented. 相似文献
957.
Brennessel WW Ellis JE Pomije MK Sussman VJ Urnezius E Young VG 《Journal of the American Chemical Society》2002,124(35):10258-10259
Reduction of tantalum pentachloride by 6 equiv of sodium naphthalene in 1,2-dimethoxyethane provided, after recrystallization from tetrahydrofuran, 50-55% yields of yellow, pyrophoric [Na(THF)][Ta(C10H8)3]. The product was shown by 1H and 13C NMR spectra and an X-ray study (on the corresponding [Na(crypt 2.2.2)]salt) to be tris(eta4-naphthalene)tantalate(1-), 1, the first homoleptic naphthalene complex of a third row (5d) transition metal. Salts of 1 react under mild conditions with excess CO (1 atm pressure, -60 degrees to +20 degrees C) and 3 equiv of anthracene, C14H10 (20 degrees C), to give 99 and 52% yields of yellow [Ta(CO)6]- and orange [Ta(C14H10)3]-, (2), respectively. The latter is the first homoleptic anthracene complex of a group 5 element and only the third one known, the others being Cr(eta6-C14H10)2 and [Co(eta4-C14H10)2]-. NMR spectra and X-ray structural characterization, as the [Na(crypt 2.2.2)] salt, established 2 to be [Ta(1-4-eta4-C14H10)3]- and is very similar to 1 in solution and in the solid state. Salts of 2 also undergo facile ligand substitution reactions. For example, it reacts with 1,3,5,7-cyclooctatetraene, COT, at 20 degrees in THF to give high yields of the previously known [Ta(COT)3]-, which was structurally characterized as the Na(crypt 2.2.2)salt. One particularly important feature concerning 1 and 2 is that they are the first available synthons for "naked" atomic Ta- and promise to be useful reagents for the general exploration of low-valent tantalum chemistry. Also, 1 and 2 represent the first homoleptic arene tantalum complexes to have been prepared by conventional syntheses. The only previously known substance of this class is the neutral bis(benzene)tantalum(0), which was accessed by the co-condensation of atomic tantalum and benzene vapor in a sophisticated (electron-gun furnace equipped) metal atom reactor. 相似文献
958.
A simple procedure for the determination of selenium and tellurium in electrolytic copper is described. These two elements are first separated from copper by passing an ammoniacal solution of the sample through Chelex-100 resin. Voltammetric interferences from nitrite liberated during the dissolution of the metal sample in nitric acid and from arsenic and antimony present in the metal are eliminated by addition of hydrogen peroxide. Excess of peroxide is quickly decomposed by the copper(II) ions present. As little as 0.01 μg Se g-1 and 0.02 μg Te g-1 can be determined; relative standard deviations (n = 5) are in the ranges 1.4–3.7% for selenium concentrations of 7.3–0.6 ppm in copper and 1.6—3.1% for tellurium concentrations of 4.6—0.5 ppm. 相似文献
959.
The complexes Pt(nb)3-n(P-iPr3)n (n=1, 2, nb=bicyclo[2.2.1]hept-2-ene), prepared in situ from Pt(nb)3, are useful reagents for addition of Pt(P-iPr3)n fragments to saturated triruthenium clusters. The complexes Ru3Pt(CO)11(P-iPr3)2 (1), Ru3Pt(-H)(3-3-MeCCHCMe)(CO)9(P-iPr3) (2), Ru3Pt(3-2-PhCCPh)(CO)10(P-iPr3) (3), Ru3Pt(-H)(4-N)(CO)10(P-iPr3) (4) and Ru3Pt(-H)(4-2-NO)(CO)10(P-iPr3) (5) have been prepared in this fashion. All complexes have been characterized spectroscopically and by single crystal X-ray determinations. Clusters 1–3 all have 60 cluster valence electrons (CVE) but exhibit differing metal skeletal geometries. Cluster 1 exhibits a planar-rhomboidal metal skeleton with 5 metal–metal bonds and with minor disorder in the metal atoms. Cluster 2 has a distorted tetrahedral metal arrangement, while cluster 3 has a butterfly framework (butterfly angle=118.93(2)°). Clusters 4 and 5 posseses 62 CVE and spiked triangular metal frameworks. Cluster 4 contains a 4-nitrido ligand, while cluster 5 has a highly unusual 4-2-nitrosyl ligand with a very long nitrosyl N–O distance of 1.366(5) Å. 相似文献
960.