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81.
直接凝固注模成型Si_3N_4及SiC陶瓷──基本原理及工艺过程 总被引:10,自引:3,他引:10
直接凝固注模成型(directcoagulationcasting,DCC)是一种崭新的(准)净尺寸陶瓷成型方法。本文报道了采用此法成型Si_3N_4及SiC陶瓷的基本原理和工艺过程。DCC成型工艺过程为把高固相含量低粘度的陶瓷浆料浇注到无孔模具中,事先加入到浆料中的生物酶及化学物质通过改变浆料的pH或电解质浓度来改变浆料的胶体化学行为,从而使浆料原位凝固,得到有足够脱模强度的陶瓷坯体。DCC成型的特点为坯体密度高(理论密度的55%~70%),坯体均匀,不用或只需少量的有机添加剂(少于1%),可成型大尺寸、复杂形状、高可靠性的陶瓷部件。 相似文献
82.
Shampa Kandoi Jeff Greeley Marco A. Sanchez-Castillo Steven T. Evans Amit A. Gokhale James A. Dumesic Manos Mavrikakis 《Topics in Catalysis》2006,37(1):17-28
A microkinetic model for methanol decomposition on platinum is presented. The model incorporates competitive decomposition
pathways, beginning with both O–H and C–H bond scission in methanol, and uses results from density functional theory (DFT)
calculations [Greeley and Mavrikakis, J. Am. Chem. Soc. 124 (2002) 7193, Greeley and Mavrikakis, J. Am. Chem. Soc. 126 (2004)
3910]. Results from reaction kinetics experiments show that the rate of H2 production increases with increasing temperature and methanol concentration in the feed and is only nominally affected by
the presence of CO or H2 with methanol. The model, based on the values of binding energies, pre-exponential factors and activation energy barriers
derived from first principles calculations, accurately predicts experimental reaction rates and orders. The model also gives
insight into the most favorable reaction pathway, the rate-limiting step, the apparent activation energy, coverages, and the
effects of pressure. It is found that the pathway beginning with the C–H bond scission (CH3OH→H2COH→HCOH→CO) is dominant compared with the path beginning with O–H bond scission. The cleavage of the first C–H bond in methanol
is the rate-controlling step. The surface is highly poisoned by CO, whereas COH appears to be a spectator species. 相似文献
83.
概述了研究定向结晶过程传递问题的分形方法,并对各类数学模型进行了分析,探讨了进一步研究的方向和途径。 相似文献
84.
85.
86.
J. Linares-Pérez R. Caballero-Águila I. García-Garrido 《International journal of systems science》2014,45(7):1548-1562
This paper addresses the optimal least-squares linear estimation problem for a class of discrete-time stochastic systems with random parameter matrices and correlated additive noises. The system presents the following main features: (1) one-step correlated and cross-correlated random parameter matrices in the observation equation are assumed; (2) the process and measurement noises are one-step autocorrelated and two-step cross-correlated. Using an innovation approach and these correlation assumptions, a recursive algorithm with a simple computational procedure is derived for the optimal linear filter. As a significant application of the proposed results, the optimal recursive filtering problem in multi-sensor systems with missing measurements and random delays can be addressed. Numerical simulation examples are used to demonstrate the feasibility of the proposed filtering algorithm, which is also compared with other filters that have been proposed. 相似文献
87.
Yuzhu Guo L.Z. Guo Daniel Coca Z.Q. Lang 《International journal of systems science》2014,45(10):2133-2144
A new parametric frequency response algorithm is introduced to investigate linear and non-linear dynamic systems with time-varying parameters. In the new algorithm the time-varying parameters are regarded as additional inputs of the systems and the non-linear generalised frequency response functions for multi-input-single-output systems are then employed to obtain Zadeh's system functions from a differential equation representation. The parametric frequency response method reveals how the time-varying parameters affect the behaviour of the systems through a time-varying term. The new method can be applied to both linear and non-linear time-varying systems. 相似文献
88.
Analysis of the polyethylene glycol glucosides and FA esters thereof by atmospheric-pressure ionization MS 总被引:1,自引:0,他引:1
Xin?Jin Jinzong?YangEmail author Bingtao?Tang Minggui?Zhu Ning?Yu Yi?Liu 《Journal of the American Oil Chemists' Society》2003,80(6):519-524
Polyethylene glycol (PEG) glucosides (PEGG) and the PEGG esters of lauric acid were analyzed by atmospheric-pressure ionization
MS (API-MS) with electrospray ionization. Straightforward mass characterization of the complex mixtures could be achieved
without prior chromatographic separation. The constituents were identified on the basis of quasi-molecular ions. Individual
components could be observed as protonated molecular ions [M+H]+ and/or as their NH4
+, Na+, or K+ adducts in positive ion mode. The mass spectrometric investigation showed that mixtures of PEGG consisted of monoglucoside,
diglucoside, polyglucoside, and free PEG. The esterification product is a mixture of two types of nonionic surfactants: PEG-laurates
and PEGG-laurates. The reasons for distortion of the quasi-molecular ion intensities and the stabilization of adduct ions
were discussed. The rapid and highly sensitive API-MS analysis technique proposed here is well suited for direct characterization
of complex mixtures and suitable for development as a routine analytical method. 相似文献
89.
90.
In the electrochemical system with liquid-liquid interface, intense local convections by the resonance with potential pulses take place. Therefore, with laser beam scattering, temporal movement of the water-mercury interface was observed. As a result, the scattering efficiency showed non-linear oscillation.
Such non-linear response could be controlled by potential pulse height. As the potential height was increased, new scattering peaks in the oscillation emerged, which was expected of a kind of bifurcation phenomenon. From these results, phase portrait, Poincarè section, correlation dimension of the strange attractor and the largest Lyapunov exponent of the trajectories were obtained. Consequently, it was concluded that all the parameters indicate chaotic behavior of the resonance flow. 相似文献