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991.
Sbai K. Abouimrane A. El Kababi K. Vilminot S. 《Journal of Thermal Analysis and Calorimetry》2002,68(1):109-122
We have studied the thermal behaviour under atmospheric pressure of isotypic tetrahydrate cyclotriphosphates MII(NH4)4(P3O9)2x4H2O (M
II=Cu, Ni and Co), between 25 and 1400°C, by X-ray diffraction, thermal analyses (TG and DTA) and infrared spectrometry. This
study shows that the series of the compounds MII(NH4)4(P3O9)2x4H2O (M
II=Cu, Ni and Co) after elimination of water, in two different stages, and ammonia leads, at 400°C to cyclotetraphosphate M2
IIP4O12 crystallized and to a thermal residue with a formula H4P4O12 which undergoes under a thermal degradation by evolving water and pentoxide phosphorus. The kinetic characteristics of the
dehydration and elimination of ammonia have been determinated. The vibrational spectra of Cu(NH4)4(P3O9)2x4H2O were examined and interpreted, in the domain of the valency frequencies, on the basis of the crystalline structure of its
isotypic compound Co(NH4)4(P3O9)2x4H2O whose cycle has the site symmetry C1, of our results of the calculation of the IR frequencies and the successive isotopic substitutions of the equivalent atoms
(3P, 3Oi and 6Oe belonging to the P3Oi3Oe6 ring) of the P3O9
3− cycle with high symmetry D3h.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
992.
Fa-Kun Zheng A-Qing Wu Yan Li Guo-Cong Guo Ming-Sheng Wang Qiang Li Jin-Shun Huang 《Journal of Molecular Structure》2005,740(1-3):147-151
Three new metal complexes, Cu(4-Hcba)2(4-cba)2(Py)2 (4-Hcba=4-cyanobenzoic acid) 1 and M[H(4-cba)2]2(Py)2 (M=Ni 2, Co 3), have been prepared by the treatment of 4-Hcba with the respective metal nitrate M(NO3)2 (M=Cu, Ni, Co) in the presence of pyridine (Py). Single-crystal X-ray diffraction analyses (3 is isostructural to 2) show that the obtained complexes are of isolated mononuclear and the metal atoms have distorted octahedral coordination environment. Two different types of intramolecular hydrogen bonds exist: asymmetrical O–HO for 1 and symmetrical OHO for 2 and 3. The crystal packing between the molecular complexes is controlled mainly by T-shaped C–Hπ interactions between pyridine and phenyl rings. Preliminary discussions on IR, UV–VIS and fluorescent spectra have also been carried out. 相似文献
993.
The new compound CuSb2O3Br crystallize in the monoclinic space group Cc. The unit cell parameters are , , , β=90°, Z=16. The crystal structure is solved from single crystal data, R=0.0490. The compound show a layered structure with slabs from cubic Sb2O3 interspersed in between puckered layers of CuBr. The Sb(III) atoms have tetrahedral [SbO3E] coordination where E is the 5s2 lone pair, these units build up Sb4O4E6 cages. The CuBr layers resemble those in hexagonal CuBr but the Cu(I) ions have actually tetrahedral [CuBr3O] coordination. The Cu-O bonds link the Sb4O6 cages with the CuBr layers. 相似文献
994.
Agnieszka Bajorek Marcin Ciepluch Jerzy Pczkowski 《Journal of polymer science. Part A, Polymer chemistry》2002,40(20):3481-3488
The series of 9‐acridyl derivatives of aromatic amines have been investigated as fluorescent probes for monitoring the progress of free‐radical polymerization. This study on the changes in the fluorescence intensity and spectroscopic shift of specific compounds was carried out during thermally initiated polymerization of methyl methacrylate and photoinitiated polymerization of 2‐ethyl‐2‐(hydroxymethyl)‐1,3‐propanediol triacrylate‐1‐methyl‐2‐pyrrolidonone mixture. The purpose of this investigation was to find a relationship between the changes in the shape and intensity of fluorescent probes and the degree of monomer conversion into a polymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3481–3488, 2002 相似文献
995.
Krayushkin M. M. Ivanov S. N. Martynkin A. Yu. Lichitsky B. V. Dudinov A. A. Uzhinov B. M. 《Russian Chemical Bulletin》2001,50(12):2424-2427
Procedures were developed for the synthesis of substituted bis(2,5-dimethyl-3-thienyl)furans based on 1,2-bis(2,5-dimethyl-3-thienyl)-2-hydroxyethanone. Dithienylethene structures in which the ethene fragment is involved in the furan or furopyrimidine system possess photochromic properties and their open forms exhibit fluorescence. 相似文献
996.
Mohamed M. El-Kerdawy Ali A. El-Emam Hussein I. El-Subbagh Elie Abushanab 《Monatshefte für Chemie / Chemical Monthly》1990,121(1):45-50
Summary A new series of thiophenic isosters of thioxanthones, namely: 2-substituted-4H-thieno[2,3-b][1]benzothiopyran-4-ones and 5-substituted-2-nitro-8-methyl-4H-thieno[2,3-b][1]benzothiopyran-4-ones were synthesized as potential schistosomicidal agents. The synthesized compounds were characterized by their1H-NMR data.
Synthese von substituierten 4H-Thieno[2,3-b][1]benzothiopyran-4-onen als mögliche schistosomicide Wirkstoffe
Zusammenfassung Es wurde eine neue Serie von thiophenischen Isosteren des Thioxanthons, nämlich 2-substituierte 4H-Thieno[2,3-b][1]benzothiopyran-4-one und 5-substituierte 2-Nitro-8-methyl-4H-thieno[2,3-b][1]benzothiopyran-4-one als potentielle schistosomicide Wirkstoffe synthetisiert. Die synthetisierten Verbindungen wurden mittels ihrer1H-NMR Daten charakterisiert.相似文献
997.
The three-dimensional structure of human cytochrome P450 3A4 was modeled based on crystallographic coordinates of four bacterial P450s: P450 BM-3, P450cam, P450terp, and P450eryF. The P450 3A4 sequence was aligned to those of the known proteins using a structure-based alignment of P450 BM-3, P450cam, P450terp, and P450eryF. The coordinates of the model were then calculated using a consensus strategy, and the final structure was optimized in the presence of water. The P450 3A4 model resembles P450 BM-3 the most, but the B helix is similar to that of P450eryF, which leads to an enlarged active site when compared with P450 BM-3, P450cam, and P450terp. The 3A4 residues equivalent to known substrate contact residues of the bacterial proteins and key residues of rat P450 2B1 are located in the active site or the substrate access channel. Docking of progesterone into the P450 3A4 model demonstrated that the substrate bound in a 6-orientation can interact with a number of active site residues, such as 114, 119, 301, 304, 305, 309, 370, 373, and 479, through hydrophobic interactions. The active site of the enzyme can also accommodate erythromycin, which, in addition to the residues listed for progesterone, also contacts residues 101, 104, 105, 214, 215, 217, 218, 374, and 478. The majority of 3A4 residues which interact with progesterone and/or erythromycin possess their equivalents in key residues of P450 2B enzymes, except for residues 297, 480 and 482, which do not contact either substrate in P450 3A4. The results from docking of progesterone and erythromycin into the enzyme model make it possible to pinpoint residues which may be important for 3A4 function and to target them for site-directed mutagenesis. 相似文献
998.
R. Kernke P. Hug A. Reller H. R. Oswald 《Journal of Thermal Analysis and Calorimetry》1992,38(4):611-618
The thermochemical reactivity of the spinel-type quaternary metal oxide Cu1–xZnxAl2O4 has been investigated for different Cu:Zn ratios. In oxygen or inert gas atmospheres no considerable reduction is observed. In molecular hydrogen metal selective reduction of the Cu is found at relatively high temperature. The solid reduction product is made up of sintered, poorly dispersed metallic copper on a Zn-Al-O metal oxide support, a potential catalyst for the methanol synthesis. Owing to the measured high reduction temperature leading to the mentioned sintering of the metallic copper, the activity of this system cannot be high.Financial support by the Swiss National Science Foundation under project Nr. 2027933.89 is gratefully acknowledged. 相似文献
999.
E.B. Lobkovskii G.L. Soloveichik A.I. Sisov B.M. Bulychev A.I. Gusev N.I. Kirillova 《Journal of organometallic chemistry》1984,265(2):167-173
The structure of a titanium aluminium hydride complex of composition [(C5H5)2TiAlH4]2(CH3)2NC2H4N(CH3)2C6H6 has been determined by X-ray diffraction. The complex forms triclinic crystals with unit cell dimensions a = 8.406(2), b = 10.117(2), c = 11.269(3) Å; α = 112.01(2)°, β = 109.25(2)°, γ = 87.04(2)°, space group P, Z = 2 and density d = 1.21 g/cm3. The structure was refined to give a discrepancy index R = 0.056. The crystals are composed of centrosymmetric molecules of (Cp2TiAlH4)2TMEDA (Cp = η5-cyclopentadienyl) and molecules of crystal benzene. Two moieties of Cp2TiH2AlH2 are linked by a tetramethylethylenediamine molecule (rAlN 2.11 Å). The aluminium atom is bonded to a titanium atom by a double hydride bridge (rAlH b = 1.8, 1.6 Å, rTiH b = 1.6 Å), and has trigonal bipyramidal stereochemistry, [H4N] (rAlH t = 1.6 Å). 相似文献
1000.
The mercury perrhenates with the empirical formulas HgReO4 and Hg2ReO5 were prepared by annealing powdered mixtures of mercury(II)oxide and mercury(II)metaperrhenate Hg(ReO4)2 in sealed silica tubes. Their crystal structures were determined from single-crystal X-ray data. HgReO4 crystallizes dimeric with nearly linear O3Re? O? Hg? Hg? O? ReO3 molecular units and Hg2ReO5 has a solid state structure, where Hg(I) and Hg(II) together with oxygen atoms form 14-membered rings, which are condensed to two-dimensionally infinite polycationic nets of composition (Hg22+ · 2 HgO)n. These nets are separated from each other by tetrahedral ReO4? anions. 相似文献