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991.
Gehrhus B Hitchcock PB Pongtavornpinyo R Zhang L 《Dalton transactions (Cambridge, England : 2003)》2006,(15):1847-1857
Reduction of Cl2Si[(NR)2C6H4-1,2] (R = CH2Bu(t)) with potassium is known to lead to the stable silylene Si[(NR)2C6H4-1,2] (1). However, silylene is now shown to react further with an alkali metal (Na or K) to yield the (1)(2)2-, c-(1)(3)-*, c-(1)(3)2- or c-(1)(4)2- derivatives. Reduction of Cl2Si[(NR)2C6H4-1,2] (R = CH2CH3 or CH2CHMe2) with potassium does not lead to an isolable silylene, but such a silylene is proposed to be an intermediate and, as for 1, reacts further to afford the potassium salts of c-[Si{(NR)2C6H4-1,2}]4-* and c-[Si{(NR)2C6H4-1,2}](4)2-. The pathways leading to the anionic cyclotri- and cyclotetrasilanes are discussed and supported experimentally; including by X-ray structures of relevant intermediates. 相似文献
992.
Rodríguez LM Gayone JE Sanchez EA Grizzi O Blum B Salvarezza RC 《The journal of physical chemistry. B》2006,110(14):7095-7097
We have used time-of-flight (TOF) direct recoiling spectroscopy (DRS) to follow propanethiol adsorption at 300 K from the vapor phase on an Ag(111) surface, for exposures ranging from 10(-1) to 10(5) L. Results show that the adsorption proceeds with changes in the sticking coefficient, consistent with at least three phases. At low exposures, the alkanethiol molecules adsorb with high probability at defect sites, followed by a slower growth mode that essentially covers the whole surface. A third change in the sticking coefficient is associated with the final saturation stage, corresponding to a thicker layer related to molecules in a more upright orientation. The adsorption kinetics for hexanethiol is similar to that of propanethiol but taking place at higher rates, stressing the importance of the hydrocarbon chain length in the growth process. ISS-TOF measurements during thermal desorption show that most of the C, H, and S go away together, suggesting that the molecules adsorb and desorb from flat regions without S-C bond cleavage. Fitting the desorption maximum at 450 K with a first-order desorption curve gives a desorption energy of 1.43 eV. A small final S content that is correlated with the initial Ag(111) surface roughness is observed after desorption. 相似文献
993.
Efficient quenching of photoluminescence from functionalized single-walled carbon nanotubes by nitroaromatic molecules 总被引:2,自引:0,他引:2
Kose ME Harruff BA Lin Y Veca LM Lu F Sun YP 《The journal of physical chemistry. B》2006,110(29):14032-14034
The photoluminescence from functionalized single-walled carbon nanotubes was found to be highly sensitive to the presence of nitroaromatic compounds such as nitrobenzene, 4-nitrotoluene, and 2,4-dinitrotoluene. The strong luminescence quenching in solution was at the upper limit of diffusion-control and also showed significant static quenching contributions. Mechanistic implication of the results and potential applications are discussed. 相似文献
994.
Fred Espen Benth Barbara Rüdiger Andre Süss 《Stochastic Processes and their Applications》2018,128(2):461-486
We propose a non-Gaussian operator-valued extension of the Barndorff-Nielsen and Shephard stochastic volatility dynamics, defined as the square-root of an operator-valued Ornstein–Uhlenbeck process with Lévy noise and bounded drift. We derive conditions for the positive definiteness of the Ornstein–Uhlenbeck process, where in particular we must restrict to operator-valued Lévy processes with “non-decreasing paths”. It turns out that the volatility model allows for an explicit calculation of its characteristic function, showing an affine structure. We introduce another Hilbert space-valued Ornstein–Uhlenbeck process with Wiener noise perturbed by this class of stochastic volatility dynamics. Under a strong commutativity condition between the covariance operator of the Wiener process and the stochastic volatility, we can derive an analytical expression for the characteristic functional of the Ornstein–Uhlenbeck process perturbed by stochastic volatility if the noises are independent. The case of operator-valued compound Poisson processes as driving noise in the volatility is discussed as a particular example of interest. We apply our results to futures prices in commodity markets, where we discuss our proposed stochastic volatility model in light of ambit fields. 相似文献
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Laura J. Waters Barbara Kasprzyk-Hordern 《Journal of Thermal Analysis and Calorimetry》2010,102(1):343-347
Micelle/water partition coefficients were obtained for procaine hydrochloride using micellar liquid chromatography (MLC) to
illustrate the potential application of this technique to compounds of pharmaceutical interest. Experiments were conducted
over a temperature range which led to calculation of a Gibbs free energy, enthalpy and entropy of transfer for procaine hydrochloride.
Successful application of this technique was confirmed using a second compound over a range of temperatures, namely caffeine.
Overall, this work confirms that MLC can be used to determine precise and accurate partition coefficients that possibly more
closely mimic biological membranes than traditional in vitro systems, namely octanol/water. 相似文献
1000.
A short synthesis for the alkaloid (+)-pilocarpine has been developed. Key step of this synthesis is a chemoenzymatic resolution utilizing the lipase AP. 相似文献