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101.
Eduardo Sommella Giacomo Pepe Francesco Pagano Gian Carlo Tenore Paola Dugo Michele Manfra Pietro Campiglia 《Journal of separation science》2013,36(20):3351-3355
We have developed a fast ultra HPLC with ion‐trap TOF‐MS method for the analysis of flavonoids in Citrus bergamia juice. With respect to the typical methods for the analysis of these matrices based on conventional HPLC techniques, a tenfold faster separation was attained. The use of a core–shell particle column ensured high resolution within the fast analysis time of only 5 min. Unambiguous determination of flavonoid identity was obtained by the employment of a hybrid ion‐trap TOF mass spectrometer with high mass accuracy (average error 1.69 ppm). The system showed good retention time and peak area repeatability, with maximum RSD% values of 0.36 and 3.86, respectively, as well as good linearity (R2 ≥ 0.99). Our results show that ultra HPLC can be a useful tool for ultra fast qualitative/quantitative analysis of flavonoid compounds in citrus fruit juices. 相似文献
102.
Two strategies have been explored for the synthesis of steroidal 20,16-γ-carbolactones from the corresponding 17-ketoandrostane. A highly efficient, stereospecific protocol has been developed for the β-oriented cis-γ-lactone, based on a Michael addition of cyanide to a conjugated ketone. A different approach, involving prior attachment of a 3-carbon side chain on C-17 of a 17-oxo-16β-acetoxy-androstane led to the epimeric, α-oriented lactone. 相似文献
103.
An integrated gas chromatographic system has been successfully developed and implemented for the measurement of oxygen, nitrogen, carbon monoxide, carbon dioxide and light hydrocarbons in one single analysis. These analytes are frequently encountered in critical industrial petrochemical and chemical processes like catalytic cracking of naphtha or diesel fuel to lighter components used in gasoline. The system employs a practical, effective configuration consisting of two three-port planar microfluidic devices in series with each other, having built-in fluidic gates, and a mid-point pressure source. The use of planar microfluidic devices offers intangible advantages like in-oven switching with no mechanical moving parts, an inert sample flow path, and a leak-free operation even with multiple thermal cycles. In this way, necessary features such as selectivity enhancement, column isolation, column back-flushing, and improved system cleanliness were realized. Porous layer open tubular capillary columns were employed for the separation of hydrocarbons followed by flame ionization detection. After separation has occurred, carbon monoxide and carbon dioxide were converted to methane with the use of a nickel-based methanizer for detection with flame ionization. Flow modulated thermal conductivity detection was employed to measure oxygen and nitrogen. Separation of all the target analytes was achieved in one single analysis of less than 12 min. Reproducibility of retention times for all compounds were found to be less than 0.1% (n = 20). Reproducibility of area counts at two levels, namely 100 ppmv and 1000 ppmv over a period of two days were found to be less than 5.5% (n = 20). Oxygen and nitrogen were found to be linear over a range from 20 ppmv to 10,000 ppmv with correlation coefficients of at least 0.998 and detection limits of less than 10 ppmv. Hydrocarbons of interest were found to be linear over a range from 200 ppbv to 1000 ppmv with correlation coefficients of greater than 0.999 and detection limits of less than 100 ppbv. 相似文献
104.
Phosphorylation of phenols with diethyl cyanophosphonate in methylene chloride solution at 0°C is an easy, rapid and good yielding reaction. 相似文献
105.
Paula Gomes Maria João Araújo Eduardo F. Marques Soraia Falcão Rodrigo O. Brito 《合成通讯》2013,43(12):2025-2036
Double-chained surfactants with potential biocompatibility have been prepared in high yields by lysine acylation with four natural saturated fatty acids (C6 to C12) and with cis-undec-5-enoic acid. The surfactants were found to assemble into nanotubules in aqueous medium and, when mixed with a commercial cationic surfactant, to spontaneously form liposomes. 相似文献
106.
Dr. Martha V. Escárcega‐Bobadilla Dr. Marta Martínez Belmonte Eddy Martin Eduardo C. Escudero‐Adán Prof. Dr. Arjan W. Kleij 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(8):2641-2648
A tetraoxo bis‐Zn(salphen) supramolecular host can bind various divalent metal salts, thereby providing access to trinuclear bifunctional systems that incorporate both Lewis acid sites and dynamically bound nucleophilic anions. The formation of these trinuclear species was investigated and their stability features were also determined. The application of these trinuclear complexes as bifunctional catalysts was evaluated in the formation of cyclic organic carbonates from epoxides and CO2. The catalytic data, in combination with control experiments, clearly demonstrate that these trinuclear compounds show much higher recycling potential compared to various control compounds and they can be used in up to five cycles without an observable loss in activity. Furthermore, this new recyclable catalytic system does not require any additives and can be applied under solvent‐free conditions. 相似文献
107.
Dr. Gregorio Guisado‐Barrios Joanna Hiller Prof. Eduardo Peris 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(31):10405-10411
Two new palladium complexes with a pyracene‐linked bis‐imidazolylidene (pyrabim) group have been obtained and fully characterized. The related monometallic analogues were obtained from the coordination of an acetanaphthene‐supported N‐heterocyclic carbene (NHC). The catalytic properties of all complexes were studied in the acylation of aryl halides with hydrocinnamaldehyde, and in the Suzuki–Miyaura coupling of aryl halides and aryl boronic acids. The results show that the presence of a second metal in the dimetallic complexes induces some benefits in the catalytic behavior of the complexes. This effect is more pronounced in the Suzuki–Miyaura coupling, for which the dimetallic complexes exhibit significantly higher activity than their monometallic counterparts. 相似文献
108.
Eduardo González‐Olivares Lina M. Gallego‐Berrío Betsabé González‐Yañez Alejandro Rojas‐Palma 《Mathematical Methods in the Applied Sciences》2015,38(18):5183-5196
In this work, a modified Holling–Tanner predator–prey model is analyzed, considering important aspects describing the interaction such as the predator growth function is of a logistic type; a weak Allee effect acting in the prey growth function, and the functional response is of hyperbolic type. Making a change of variables and time rescaling, we obtain a polynomial differential equations system topologically equivalent to the original one in which the non‐hyperbolic equilibrium point (0,0) is an attractor for all parameter values. An important consequence of this property is the existence of a separatrix curve dividing the behavior of trajectories in the phase plane, and the system exhibits the bistability phenomenon, because the trajectories can have different ω ? limit sets; as example, the origin (0,0) or a stable limit cycle surrounding an unstable positive equilibrium point. We show that, under certain parameter conditions, a positive equilibrium may undergo saddle‐node, Hopf, and Bogdanov–Takens bifurcations; the existence of a homoclinic curve on the phase plane is also proved, which breaks in an unstable limit cycle. Some simulations to reinforce our results are also shown. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
109.
Machado Poliana A. L. Cavalcanti Marcello H. S. Silva Fábio A. B. de Almeida Eduardo T. Cardoso Marcus V. C. Mesquita Anderson F. Lemes Nelson H. T. Virtuoso Luciano S. 《Journal of solution chemistry》2022,51(3):320-344
Journal of Solution Chemistry - Liquid–liquid equilibrium (LLE) data and phase diagrams for new aqueous two-phase systems (ATPSs) containing 1-butyl-3-methylimidazolium chloride... 相似文献
110.
César Ruiz-Zambrana Rajeev K. Dubey Macarena Poyatos Prof. Aurelio Mateo-Alonso Prof. Eduardo Peris 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(44):e202201384
A series of rhodium and iridium complexes with a N-heterocyclic carbene (NHC) ligand decorated with a perylene-diimide-pyrene moiety are described. Electrochemical studies reveal that the complexes can undergo two successive one-electron reduction events, associated to the reduction of the PDI moiety attached to the NHC ligand. The reduction of the ligand produces a significant increase on its electron-donating character, as observed from the infrared spectroelectrochemical studies. The rhodium complex was tested in the [3+2] cycloaddition of diphenylcyclopropenone and methylphenylacetylene, where it displayed a redox-switchable behavior. The neutral complex showed moderate activity, which was suppressed when the catalyst was reduced. 相似文献