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911.
Reactivity of Tris(dialkylthiophosphinyl)phosphines – Crystal Structure of [Ag{O[P(S)Me2]2}2][AsF6] In contrast to tris(dialkylphosphoryl)phosphines the reaction of tris(dimethylthiophosphinyl)phosphine with transition metal hexafluoroarsenates of the type [M(SO2)m [AsF6]n (M = Ag, m = 0, n = 1; M = Fe, Cd, m = n = 2) forms no molecular 2 : 1-complexes but polymeric products. The silver polymer is transformed into [Ag{O[P(S)Me2]2}2][AsF6], which is also formed by the reaction of Ag[AsF6] with O[P(S)Me2]2. It crystallizes in the space group P1 with a = 862.5(2), b = 1 241.4(2), c = 1 254.0(3)pm, α = 80.34(1), β = 101.99(6), γ= 73.75(1)° (at 20°C) and Z = 2. The central silver atom is surrounded by four sulphur atoms in a slighly distorted tetrahedron. The average (Ag? S) and (P? S) bond lengthes are 259.4(2) pm and 194.9(2)pm, respectively. 相似文献
912.
Mao Jiang-Gao 《结构化学》1994,(5)
Preparation and Crystal Structures of LaCl_3(12-crown-4)(MeOH)and[LaCl_3(phen)_2(H_2O)]·MeOHMaoJiang-Gao(FujianInstituteofResea... 相似文献
913.
利用核磁共振方法研究了取代吡唑对炔基Fischer卡宾化合物的Michael加成的动力学行为,该反应为典型的二级反应。当吡唑的3,5-位由较大基团取代时,反应速率常数变小,而活化焓和活化熵明显增大。利用密度泛函理论研究了炔基钨卡宾为底物的Michael加成反应机理,发现吡唑上取代基团的增大可以导致第三步反应的活化能大于第一步,从而使反应的决速步骤由原来的第一步转变为第三步。 相似文献
914.
José Neri G.?Paniz érico Marlon de M.?Flores Ayrton F.?MartinsEmail author 《Mikrochimica acta》2005,152(1-2):89-92
With the aim of avoiding cumbersome sample treatment, we present a device for the introduction of solid soil samples into
AAS-flames for gold determination, as well as the proposition of earth from anthills as a gold occurrence indicator. A previous
ground sample of anthill earth (0.50 mg) was weighed directly into a small recipient of polyethylene which was then connected
to a sampling boronsilicate glass chamber. The sample was carried by an airflow (5 L min−1) to a quartz cell positioned between the burner top and the optical beam. The generated atomic vapor produced a transient
signal which was totally integrated in three seconds. The performance was compared with conventional flame atomic absorption
spectrometry after proper sample digestion. No significant differences were observed between both procedures (mean deviation
±1.90%), and a LOQ of 0.03 μg Au was achieved using the proposed method. The anthill earth was found to be very suitable for
indication of gold occurrence in soils and related materials. 相似文献
915.
Wagner J. Barreto Henrique de Santana Flaveli A. S. Almeida Dilson N. Ishikawa Yoshio Kawano 《Journal of Analytical and Applied Pyrolysis》2003,70(2):719-210
The synthesis, characterization, and thermal decomposition of the [Ni(SCN)2(H+SCN)2(4-mepy)2] compound with an octahedral structure in polymeric chain were reported, in which SCN groups form bridges among Ni(II) ions. The compound decomposes in water resulting in a pH<4 solution. The FT-IR spectrum presented doublet bands at 2117; 2128 cm−1, 788; 773 cm−1 assigned to ν(C---N) and ν(C---S) stretching modes, respectively, and δ(SCN) deformation modes at 468; 476 cm−1. The Raman spectrum of the compound presented the ν(C---N) stretching as a strong doublet at 2122; 2128 cm−1, ν(C---S) at 783; 770 cm−1, and δ(SCN) at 468; 477 cm−1. No significant changes were observed in the 4-mepy ligand bands compared with the vibrational frequencies of the pure compound or the compound in aqueous solution 0.2 mol l−1. The crystal UV–vis reflectance spectrum presented two bands centered in 626 and 424 nm tentatively assigned to the d→d type transitions, 3A2g→3T1g and 3A2g→3T1g, for a symmetry close to Oh. The TG curve showed a mass loss between 120 and 200 °C assigned to the loss of the two 4-mepy molecules; from 200 to 265 °C, the loss of the two H+SCN groups; and from 265 to 450 °C, the loss of the two SCN groups that formed the bridges among the nickel atoms. Based on these mass loss data, a mechanism of thermal decomposition for the compound was proposed. 相似文献
916.
Katsuhiko Ono Kyohei Yoshikawa Hiroyuki Yamaguchi Masaaki Tomura Katsuhiro Saito 《Tetrahedron》2007,63(38):9354-9358
BF2 complexes with 1,3-diketone ligands were synthesized, and their optical and electrochemical properties were studied. The colors of the complexes varied depending on the structures of the 1,3-diketone ligands. The absorption and emission maxima of the complexes with 1,3-diaryl-1,3-diketone ligands were considerably red shifted as compared to those of the complexes with 1-aryl-3-trifluoromethyl-1,3-diketone ligands, suggesting an extended π-conjugation of the 1,3-diaryl-1,3-diketone moieties. The molar absorption coefficients and quantum yields of the complexes with 1,3-diaryl-1,3-diketone ligands were larger than those of the complexes with 1-aryl-3-trifluoromethyl-1,3-diketone ligands. Cyclic voltammetry measurements revealed that the reduction potentials of the BF2 complexes were higher than those of the free ligands. These complexes exhibited various emission colors in the solid states due to the intermolecular interactions. 相似文献
917.
Two novel supramolecular complexes [Cu(bpapa)(dhbd)]·CHaOH (1) and [Cu(bpapa)(ma)]·ma (2) (bpapa= bis[6-(2-pyridylamino)pyrid-2-yl]amine, dhbd=2,3-dihydroxybutanedioate dianion, ma=a-methacrylate) were rationally designed, synthesized and characterized by single crystal X-ray diffraction, IR, electronic spectroscopy and thermogravimetric analyses. Complex 1 was the first oligo-a-pyfidylamino complex based on hydroxypolycarboxylate and self-assembled into a 3D honeycomb configuration network with open channels and tubes containing 1D ladder-shaped double chains formed by hydrogen bonds and aromatic π-π stacking interactions. Complex 2 constructed a 2D supramolecular network extended by 1D chains from dimeric supramolecular synthon through noncovalent supramolecular interactions. In the two complexes, the chelating monohelical ligand adopted all-anti configuration. Density functional theory calculations were applied to 1 and 2. 相似文献
918.
IntroductionAmperometricbiosensorofhydrogenperoxideisofpracticalimportancebecauseofitswideapplicationsinchemical,biological,clinical,environmentalandmanyotherfields.Forimprovementofsensor抯quality,vari-ouskindsofchemicalmodificationmethodshavebeendevelopedforreducingredoxoverpotentialsofH2O2atelectrodesurfaces,increasingthedetectionsensitivity,linearrange,stabilityandlivetime.Ithasbeenshownthattheuseofsub-micrometersizedmetalparticlessuchasPt-blackcansignificantlyimprovethequalityofthebiosens… 相似文献
919.
A series of [tetra-α-(2,2,4-tirmethyl-3-pentoxy) phthalocyaninato] metal complexes(M=Co, Ni, Cu, Zn)were prepared by cyclotetramerization of 3-(2,2,4-tirmethyl-3-pentoxy)phthalonitrile with corresponding anhydrous metal salts, using 1.8-diazabicyclo[5.4.0] undec-7-ene (DBU) as the catalyst. HPLC analysis shows that one isomer predominates in the product of nickel complex, while at least two main constitutional isomers exist in the product of other metal complexes. The complexes (in the form of mixture of constitutional isomers) were characterized by elemental analyses, MS, IR and UV-Vis spectroscopy. 相似文献
920.
A series of titanium complexes [(Ar)NC(CF3)CHC(R)O]2TiCl2 (4b: Ar = -C6H4OMe(p), R = Ph; 4c: Ar = -C6H4Me(p), R = Ph; 4d: Ar = -C6H4Me(o), R = Ph; 4e: Ar = α-Naphthyl, R = Ph; 4f: Ar = -C6H5, R = t-Bu; 4g: Ar = -C6H4OMe(p); R = t-Bu; 4h: Ar = -C6H4Me(p); R = t-Bu; 4i: Ar = -C6H4Me(o); R = t-Bu) has been synthesized and characterized. X-ray crystal structures reveal that complexes 4b, 4c and 4h adopt distorted octahedral geometry around the titanium center. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 4b-c and 4f-i are active catalysts for ethylene polymerization and ethylene/norbornene copolymerization, and produce high molecular weight polyethylenes and ethylene/norbornene alternating copolymers. In addition, the complex 4c/MMAO catalyst system exhibits the characteristics of a quasi-living copolymerization of ethylene and norbornene with narrow molecular weight distribution. 相似文献