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121.
122.
针对一类含有不确定参数的网络控制系统(NCS),研究网络中存在时延与丢包情况下的鲁棒?∞控制问题.构造一个新的Lyapunov-Krasovskii泛函,并基于改进的Wirtinger不等式推导出闭环NCS渐近稳定且满足?∞性能的充分条件,该条件能得到比已有文献保守性更小的结果.给出线性锥补算法以实现次优鲁棒?∞控制器增益的求解.最后通过多个数值实例验证了所提出方法的有效性. 相似文献
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124.
离子水是一种新型的保健饮用水.本文主要对饮用水、离子水的功能和作用进行了概述,阐述了离子水对人类生活和健康的影响,且指出了离子水具有良好的发展、开发和推广的前景. 相似文献
125.
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
126.
A great number of complex electronic devices are now part of our everyday lives. While many of us learn to handle these products by trial and error; others, especially older users with little experience in using electronic devices, need support. In order to allow the user maximum flexibility in terms of learning time and location, a training programme is presented which is implemented as part of the software embedded in the product itself. Particular focus is placed on the effect of adaptive training on learning. In this study, the training versions differed in their ability to adjust their complexity to the user's experience (adaptive user interface complexity) and their capability to support the learner by prompting them during the learning process (adaptive training advice). The results show that the adjustment of complexity had a positive effect on users’ experience: elderly users who trained with an adaptive interface were more successful in learning to use a mobile phone. Adaptive training advice, however, was found to have no significant effects on learners’ success and reduced their self-efficacy. This work offers guidelines on how to design integrated training applications for electronic devices that successfully help elderly users with little prior experience. 相似文献
127.
Poly(epichlorohydrin-g-styrene) copolymers, P(ECH-g-S)s, have been prepared in solution by two different methods of coupling polyepichlorohydrin, PECH, with polystyrene, PS, containing a functional end group. In the first method, polystyryl carboxylic acid, PSCOOH, prepared from living polystyrene, was converted to the corresponding potassium salt which was coupled with PECH in dimethyl formamide solution usually at 60°C. In the second method, polystyryl potassium, PS?K+, in tetrahydrofuran solution was end-capped with propylene sulphide to form PSCH2CH(CH3)S?K+ which was coupled directly with PECH in tetrahydrofuran at 40°C. Grafting by the first reaction was relatively slow but occurred without significant adverse side reactions. The grafting by the second reaction was relatively fast, but side reactions occurred resulting in a cleavage of the graft copolymer. The graft copolymers were purified by fractional precipitation and extraction procedures and were characterized by infra-red and ultra-violet spectroscopy, microanalysis, gel permeation chromatography, differential scanning calorimetry, solution viscometry, dynamic mechanical testing, and electron microscopy. Solution properties of the graft copolymers in benzene-carbon tetrachloride and toluene-cyclohexane mixtures were studied. There was evidence of micelle formation in dilute solutions of the mixed solvents and microphase separation of components in the solid state. Nucleophilic substitution of chlorine atoms in PECH by phenyl acetate (C6H5 CH2COO-) and thiophenoxide (C6H5S-) groups was performed. 相似文献
128.
129.
纤维素科学与技术研究进展 总被引:3,自引:0,他引:3
梁锋 《纤维素科学与技术》1993,1(3):1-14
本文综述纤维素科学与技术的研究进展。阐述了纤维素结构、纤维素的合成、纤维素液晶、功能纤维素、纤维素溶剂、纤维素裂解和纤维素的废物利用等的最新动态。 相似文献
130.
Changho Jung Hideyuki Tsuboi Michihisa Koyama Momoji Kubo Ewa Broclawik Akira Miyamoto 《Catalysis Today》2006,111(3-4):322-327
CO adsorption over Pd4 and Pt4 cluster supported by c-ZrO2(1 1 1) and CeO2(1 1 1) catalyst systems was investigated using periodic density functional method in order to clarify the support effect on CO activation. We found that the support increases the CO activation for bridge and three-fold sites but decreases for the atop site. Moreover, it was found that the support changes the site preference for the CO adsorption. Bridge site on both the Pt4/c-ZrO2 and Pt4/CeO2 show larger CO adsorption energies than those on the other sites while the atop site is energetically preferable on isolated Pt4 cluster. c-ZrO2 supported Pd shows the largest CO activation with large charge transfer from the catalyst to the CO molecule. This reveals that ZrO2 supported Pd can be a good catalyst for CO activation because of its higher probability to the three-fold site CO adsorption. We also found that positively charged M4 clusters on the support keep their strong electron-donating properties and have enough charge density to contribute to the activation of an adsorbed CO molecule by a charge transfer. 相似文献