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181.
Nikolaos S Papageorgiou 《Journal of multivariate analysis》1985,17(2):207-227
This second part of the work on Banach space valued multifunctions begins with a detailed study of set valued martingales, which have their values in a Banach space. Several new convergence theorems are established for different modes of convergence. The profile of a multifunction in connection with set valued martingales is also studied. The notion of weak convergence of multifunctions is introduced and used to obtain additional convergence theorems for set valued martingales. In the last two sections of the paper set valued measures dealt with and an integral with respect to a set valued measure is introduced. 相似文献
182.
Tsitsas Nikolaos L.; Athanasiadis Christodoulos 《The Quarterly Journal of Mechanics and Applied Mathematics》2006,59(1):55-74
A spherical electromagnetic wave is scattered by a layered sphere.The exact expressions of the scattered and interior fields areobtained by solving the corresponding boundary-value problem,by means of a combination of Sommerfeld's and T-matrix methods.A recursive algorithm with respect to the number of layers isextracted for the computation of the fields in every layer.The far-field pattern and the scattering cross-sections aredetermined in terms of the physical and geometrical characteristicsof the scatterer. As the point-source tends to infinity, theknown results for plane wave incidence are recovered. Numericalresults are presented for several cases and various parametersof the layered spherical scatterer. 相似文献
183.
Atrane-analogous Compounds. III. Atrane-analogous Compounds of the Type Me2DCH2CH2OSi(Me)(OCH2 CH2)2 D′Me (I) and Type Me2DCH2CH2OSi(Me) OCH2CH22D″Me2 (II) (Me?CH3; D, D′, D″?N, P, As) Atrane analogous compounds I and II (Abb. 1) have been prepared by condensation reactions of trifunctional silanes RSiX3 (X?Cl, OEt, NMe2) with N-methyldiethanolamine, ß-chloroethanol, ß-dimethylaminoethanol, and ß-dimethylarsanoethanol according to eqn. (1) to (3) and reaction schemes of Figs. 2 and 3, respectively. For compounds of type I weak N→Si adduct bonding is indicated for the MeN-donor of the eight-membered ring by significant shifts of the MeNCH2 and OCH2 proton n.m.r. signals. For compounds of type II there is no n.m.r. evidence for D→Si interactions. In spite of equal Lewis acidity of the Si atoms differences in adduct formation are observed for cage, ring, and acyclic podand systems, which can be explained mainly by entropy effects connected to the formation of five-membered rings. 相似文献
184.
Kristi S. Anseth Christopher N. Bowman Nikolaos A. Peppas 《Journal of polymer science. Part A, Polymer chemistry》1994,32(1):139-147
Multifunctional monomers (trimethylol propane trimethacrylate, trimethylol propane triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol monohydroxy pentaacrylate) were photopolymerized with 2,2-dimethoxy-2-phenylacetophenone as the photoinitiator to produce highly crosslinked networks. The volume shrinkage behavior and the reaction kinetics were studied under various reaction conditions. The volume shrinkage and maximum functional group conversion were dependent on the number of functional groups, type of functional group, and the curing conditions. The maximum functional group conversion was also dependent on the reaction temperature. All the polymerized systems exhibited a strong coupling between the volume relaxation and the reaction kinetics. The kinetic constants were also determined as a function of conversion, and the termination mechanism was found to be reaction diffusion dominated even at low conversions. The importance of these results on the prediction of the reaction behavior for multifunctional monomers producing highly crosslinked polymers is discussed. © 1994 John Wiley & Sons, Inc. 相似文献
185.
The ring-substituted bis(cyclopentadienyl)silanesMe
2Si(C5H5) (MeC5H4) (1a) andMe
2Si(MeC5H4)2 (2a) could be prepared by the reactions ofMe
2SiCl2 with C5H5Na andMeC5H4Na or only withMeC5H4Na, respectively. Metallation of1 a or2 a withn-BuLi and following reaction with TiCl4 led to the first ringsubstituted [1]titanocenophanes,Me
2Si(C5H4) (MeC5H3)TiCl2 (1 b) orMe
2Si(MeC5H3)2 TiCl2 (2 b), respectively. On reaction with NaI,1 b yieldedMe
2Si(C5H4) (MeC5H3)TiI2 (1 c). Structural assignments of the compounds could be made on the basis of their1H NMR spectra. 相似文献
186.
In this study arsenic compounds were determined in mussels (Mytulis galloprovincialis), anchovies (Engraulis encrasicholus), sea-breams (Sparus aurata), sea bass (Dicentrarchus labrax) and sardines (Sardina pilchardus) collected from Aegean Sea using liquid chromatography-photo-oxidation-hydride generation-atomic fluorescence spectrometry [LC-(PO)-HG-AFS] system. Twelve arsenicals were separated and determined on the basis of their difference in two properties: (i) the pKa values and (ii) hydride generation capacity. The separation was carried out both with an anion- and a cation-exchange column, with and without photo-oxidation. In all the samples arsenobetaine, AB was detected as the major compound (concentrations ranging between 2.7 and 23.1 μg g−1 dry weight), with trace amounts of arsenite, As(III), dimethylarsinic acid, DMA and arsenocholine, AC, also present. Arsenosugars were detected only in the mussel samples (in concentrations of 0.9-3.6 μg g−1 dry weight), along with the presence of an unknown compound, which, based on its retention time on the anion-exchange column Hamilton PRP-X100 and a recent communication [E. Schmeisser, R. Raml, K.A. Francesconi, D. Kuehnelt, A. Lindberg, Cs. Soeroes, W. Goessler, Chem. Commun. 16 (2004) 1824], is supposed to be a thio-arsenic analogue. 相似文献
187.
The ability of vesicle-coated silica to aid the extraction of organic compounds from water prior to liquid chromatographic analysis is presented for the first time. The method is based on the formation of silica supported cationic multi-lamellar vesicles of gemini surfactants inherently ensuring the presence of hydrophilic and hydrophobic sites for the partitioning of analytes bearing different properties. Method development is illustrated by studying the adsolubilization of UV absorbing chemicals from swimming pool water. Due to the requirement for external energy input (intense shearing) a method based on solid-phase dispersion (SPD) was applied producing better results than off-line solid-phase extraction (SPE). Meticulous investigation of the experimental parameters was conducted in order to elucidate the mechanisms behind the proposed extraction pattern. Analyte recoveries were quantitative under the optimum experimental conditions offering recoveries higher than 96% with RSD values below 5%. 相似文献
188.
Research activity in the Balkan and East Mediterranean countries was evaluated on the basis of publications appearing in Analytical Abstracts (AA) during the cumulative 8-year period of 1994-2001. This was accomplished by assessing the scientific publication productivity in analytical chemistry as the number of publications from each country and the number of publications per population unit. To assess the impact in the scientific community, the mean impact factor for each country was calculated. The publication productivity trend was recorded for the 7-year period 1994-2000. Moreover, the preference to publish in specific journals per country was appraised. According to the total number of publications, Egypt (765 publications) and Greece (717 publications) are the most productive countries, while Slovenia shows the highest number of publications per million of population (140). Scientists from Israel published their work in the highest impact analytical journals with a mean impact factor of 2.02, followed by Slovenia (mean impact factor of 1.67) and Greece (mean impact factor of 1.53). Studies of scientists from different countries do not show any obvious preference to a single specific journal. It is interesting to note that preference for journals reveals the research interests of scientists from each country for sub-fields of analytical chemistry. 相似文献
189.
The sensitivity of the photosynthetic apparatus to ultraviolet-B (UV-B) irradiation was studied in cultures of unicellular green alga Scenedesmus obliquus incubated in low light (low photosynthetically active radiation intensity [LL]) and high light (high photosynthetically active radiation intensity [HL]) conditions, treated or not with exogenous polyamines. Biochemical and physicochemical measurements showed that UV-B radiation induces a decrease in the thylakoid-associated putrescine (Put) and an increase in spermine (Spm), so that the reduction of Put/Spm ratio leads to the increase of light-harvesting complex II (LHCII) size per active reaction center and, consequently, the amplification of UV-B effects on the photosynthetic apparatus. The separation of oligomeric and monomeric forms of LHCII from isolated thylakoids showed that UV-B induces an increase in the oligomeric forms of LHCII, which was more intense in LL than in HL. By manipulating the LHCII size with exogenous polyamines, the sensitivity degree of the photosynthetic apparatus to UV-B changed significantly. Specifically, the addition of Put decreased highly the sensitivity of LL culture to UV-B because of the inhibitory effect of Put on the LHCII size increasing, whereas the addition of Spm enhanced the UV-B injury induced in HL culture because of the increasing of LHCII size. The ability of the photosynthetic apparatus to recover the UV-B induced changes was also investigated. 相似文献
190.
In this paper we report a method for the determination of 4-aminophenol (4-AP) in solution using a quartz crystal microbalance (QCM) sensor. 4-AP reacts with (para-unsubstituted) phenols to form hydrophobic indophenol dye species that precipitate out and adsorb to the surface of the crystal to produce a shift in the crystal resonant frequency. This frequency change, due to in-situ indophenol mass adsorption, can be related to the initial 4-AP concentration. A range of phenols (namely o-cresol, 1-naphthol, resorcinol, catechol and 8-hydroxyquinoline) and their reaction with 4-AP were tested. Ammonium persulfate (APS) and potassium periodate were used as initiators to improve the speed of the reaction and the rate of formation of the precipitate. APS elicited improved signal in terms of response times and frequency shifts compared with KIO4. Of the phenols studied, resorcinol gave the best response time of 6 min for 4-AP determination. The reaction of resorcinol with 4-AP gave extended response times and signal size with decreasing concentration of 4-AP (in the range 2-5 mM). 相似文献