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31.
Yu-Ping Zhang Kwang-Pill Lee Hyun-Joo Noh Ali Md Showkat Seong-Ho Choi 《Microchemical Journal》2004,78(2):99-106
An appropriate optimization strategy should be used to find a desired resolution or selectivity with a minimum number of experiments in a limited time, which could assure the baseline separation of all target compounds. It was usually realized by means of a specialized computer program. In this paper, mapping optimization method and overlapping resolution mapping were compared for the optimization of a reversed-phase high-performance liquid chromatography (HPLC) isocratic separation of neutral compounds. The calculated resolutions and separation time of 7 to 10 experiments are fitted by different equations, which were used to build a contour plot with a minimum effective resolution and maximum retention time as a function of a mobile phase composition. The balance between resolution and analysis time could be easily realized by the overlapping of the final overlapping resolution mapping and analysis time mapping. The validity of the two methods was confirmed by some typical experiments. The models are simple, visual, and common without theoretical arithmetic. 相似文献
32.
Akhtaruzzaman M Kamata N Nishida J Ando S Tada H Tomura M Yamashita Y 《Chemical communications (Cambridge, England)》2005,(25):3183-3185
Dithiazolylbenzothiadiazoles easily obtained have high electron affinity and the FET device of a trifluoromethylphenyl derivative exhibited a good n-type performance with high electron mobility. 相似文献
33.
R. Sanduja G. E. Martin A. J. Weinheimer M. Alam M. B. Hossain Dick van der Helm 《Journal of heterocyclic chemistry》1984,21(3):845-848
The marine coelenterate Echinopora lamellosa (class Anthozoa, family Scleractinidae) was found to contain a number of unprecedented secondary metabolites which were isolated and identified as smilagenin (I), neodunol methyl ether (II), glycyrrhetic acid (III), 3β-acetoxyglycyrrhetic acid (IV), and 3β-acetoxy-11-deoxoglycyrrhetic acid (V). The structure of neodunol methyl ether was confirmed and its absolute configuration determined by the x-ray diffraction method. 相似文献
34.
An efficient route to various sugar lactones has been developed. Key to the overall transformation is the sequential osmium-catalyzed dihydroxylation of 2,4-dienoates. The simplest (one-step/racemic) example of this reaction occurs when the dihydroxylation is performed with aqueous NMO in MeOH. When the first dihydroxylation is performed using the AD-mix procedure, an enantioselective variant results. When a matched AD-mix procedure is used for the second dihydroxylation, an exceedingly diastereo- and enantioselective synthesis of galacto-1,4-lactone results. [Reaction: see text] 相似文献
35.
Xanthine Sensors Based on Anodic and Cathodic Detection of Enzymatically Generated Hydrogen Peroxide
A xanthine biosensor was fabricated by the covalent immobilization of xanthine oxidase (XO) onto a functionalized conducting polymer (Poly‐5, 2′: 5′, 2″‐terthiophine‐3‐carboxylic acid), poly‐TTCA through the formation of amide bond between carboxylic acid groups of poly‐TTCA and amine groups of enzyme. The immobilization of XO onto the conducting polymer (XO/poly‐TTCA) was characterized using cyclic voltammetry, quartz crystal microbalance (QCM), and X‐ray photoelectron spectroscopy (XPS) techniques. The direct electron transfer of the immobilized XO at poly‐TTCA was found to be quasireversible and the electron transfer rate constant was determined to be 0.73 s?1. The biosensor efficiently detected xanthine through oxidation at +0.35 V and reduction at ?0.25 V (versus Ag/AgCl) of enzymatically generated hydrogen peroxide. Various experimental parameters, such as pH, temperature, and applied potential were optimized. The linear dynamic ranges of anodic and cathodic detections of xanthine were between 5.0×10?6?1.0×10?4 M and 5.0×10?7 to 1.0×10?4 M, respectively. The detection limits were determined to be of 1.0×10?6 M and 9.0×10?8 M with anodic and cathodic processes, respectively. The applicability of the biosensor was tested by detecting xanthine in blood serum and urine real samples. 相似文献
36.
Shariff?E.?KabirEmail author M.?Arzu?Miah M.?Abdur?Rahim Sonia?Sultana G.?M.?Golzar?Hossain Ebbe?Nordlander Edward?Rosenberg 《Journal of Cluster Science》2005,16(1):93-110
Treatment of Ru3(CO)12 with dpphSe2 (dpph = 1,6-bis(diphenylphosphino)hexane) in refluxing toluene in the presence of Me3NO afforded two new compounds, Ru3(CO)7(-CO)(3-Se)(-dpph) (1) and Ru3(CO)7(3-Se)2(-dpph) (2). A similar reaction of Ru3(CO)12 with dpppeSe2 (dpppe = 1,5-bis(diphenylphosphino)pentane) gave exclusively Ru3(CO)7(3-Se)2(-dpppe) (3). Treatment of Ru3(CO)12 with dpphS2 and dpppeS2 at 110°C in the presence of Me3NO afforded Ru3(CO)7(3-S)2(-dpph) (4) and Ru3(CO)7(3-S)2(-dpppe) (5), respectively. Reactions of Fe3(CO)12 with dpphSe2 and dpppeSe2, under identical conditions, afforded Fe3(CO)7(3-Se)2(-dpph) (6) and Fe3(CO)7(3-Se)2(-dpppe) (7), respectively. Compounds 1–7 were characterized spectroscopically and the molecular structures of compounds 1–4 were determined by single crystal X-ray crystallography. The core of 1 contains an equilateral triangle of ruthenium atoms with one capping selenium, one bridging dpph, one doubly bridging carbonyl and seven terminal carbonyl ligands. Complexes 2–4 have a square-pyramidal structure with two metal and two chalcogenide atoms alternating in the basal plane and the third metal atom at the apex of the pyramid, and belong to the family of well-known nido clusters with seven skeletal electron pairs. 相似文献
37.
Two-dimensional capillary electrophoresis was used for the separation of proteins and biogenic amines from the mouse AtT-20 cell line. The first-dimension capillary contained a TRIS–CHES–SDS–dextran buffer to perform capillary sieving electrophoresis, which is based on molecular weight of proteins. The second-dimension capillary contained a TRIS–CHES–SDS buffer for micellar electrokinetic capillary chromatography. After a 61-s preliminary separation, fractions from the first-dimension capillary were successively transferred to the second-dimension capillary, where they further separated by MECC. The two-dimensional separation required 60 min. 相似文献
38.
Noorjahan Begum Amarash C. Ghosh Shariff E. Kabir Md. Arzu Miah G.M. Golzar Hossain 《Polyhedron》2005,24(18):3074-3081
Four triosmium carbonyl clusters bearing terminal pyrazines, bridging hydroxy and methoxycarbonyl ligands of general formula [Os3(CO)9(μ-OH)(μ-OMeCO)L] (1, L = pyrazine; 2, L = 2-methylpyrazine; 3, L = 2,3-dimethylpyrazine; 4, L = 2,3,5-trimethylpyrazine) were synthesized by the reactions of [Os3(CO)12] with the corresponding pyrazine derivatives and water in the presence of a methanolic solution of Me3NO in moderate yields. Compounds [Os3(CO)9(μ-OH)(μ-OMeCO)L] react with a series of two electron donor ligands, L′ at ambient temperature to give [Os3(CO)9(μ-OH)(μ-OMeCO)L′] (5, L′ = PPh3; 6, L′ = P(OMe)3; 7, L′ = tBuNC; 8, L′ = C5H5N) in good yields by the displacement of the pyrazine ligands. This implies that the pyrazine ligands in 1–4 are relatively labile. Compounds 2, 3, 4, and 8 were characterized by single crystal X-ray diffraction analyses. All the four compounds possess two metal–metal bonds and a non-bonded separation of two osmium atoms defined by Os(1)Os(3), which are simultaneously bridged by OH and MeOCO ligands and a heterocyclic ligand is terminally coordinated to one of the two non-bonded osmium atoms. 相似文献
39.
Ali Mohammad Akbar Edwards Alice A. Tuah Jauyah Hossain Mir Ezharul Nazimuddin Mohamed 《Transition Metal Chemistry》1997,23(1):41-44
A new, potentially polydentate sulfur–nitrogen chelating agent, 2,6–bis(N-methyl-S-methyldithiocarbazato)pyridine (L) has
been synthesized and characterized. With nickel(II) salts, the ligand yields complexes of empirical formula NiLX2·nH2O (X=Cl−,
NCS− or NO3−; n=0 or 1) in which it behaves as a quadridentate NSSN chelating agent, coordinating to the nickel(II) ion via
the two amino nitrogen atoms and the two sulfur atoms. Magnetic and spectral evidence support a distorted octahedral structure
for these complexes. The ligand reacts with copper(II), platinum(II) and palladium(II) salts to yield homo-binuclear complexes
of general formula [M2LX4]·nSol (M=CuII, PtII or PdII; X=Cl− or Br−; n=0.5, 1 or 2; Sol=H2O, MeOH or MeCOMe), in which each
of the metal ions is in a square-planar environment. These complexes have been characterized by a variety of physicochemical
techniques.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
40.
Matin MR Katsumoto Y Matsuura H Ohno K 《The journal of physical chemistry. B》2005,109(42):19704-19710
Hydration of short-chain poly(oxyethylene)s, CH(3)(OCH(2)CH(2))(m)OCH(3) (abbreviated as C(1)E(m)()C(1)) (m = 1-3), in carbon tetrachloride has been studied by infrared spectroscopy. The O-H stretching vibrations of water in ternary solutions with H(2)O:C(1)E(m)C(1):CCl(4) mole ratios of 0.000418:0.005:0.995 to 0.000403:0.04:0.96 were analyzed. Two types of hydrogen bonds are formed in the interaction between water and C(1)E(m)C(1) in carbon tetrachloride; one is a monodentate hydrogen bond, in which only one of the O-H bonds of a water molecule participates in hydrogen bonding, and the other is a bidentate hydrogen bond, in which both of the O-H bonds of a water molecule participate in hydrogen bonding by bridging oxygen atoms separated by two or more monomer units on the polymer chain. An important finding is that the bidentate hydrogen-bond bridge is not formed between the nearest-neighbor oxygen atoms. This experimental observation supports the results of previous molecular dynamics simulations. The shortest oligomer of poly(oxyethylene), i.e., CH(3)OCH(2)CH(2)OCH(3) (1,2-dimethoxyethane) with a single monomer unit, is suggested not to be an adequate model for this polymer with respect to hydrogen bonding to water. The hydrogen bonding in a 1:1 C(1)E(m)C(1)-water adduct in carbon tetrachloride represents primitive incipient hydration of poly(oxyethylene). The present results indicate that both monodentate and bidentate hydrogen bonds are important and the latter is destabilized more rapidly than the former with increasing temperature. This dehydration process can be a potential mechanism of the poly(oxyethylene)-water phase separation. 相似文献