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91.
Jianying Li Shengtao Li Fuyi Liu M. A. Alim G. Chen 《Journal of Materials Science: Materials in Electronics》2003,14(8):483-486
The role of oxygen in the heat-treatment process of SrTiO3 varistor ceramics has been investigated in this paper. The varistor voltage of SrTiO3 ceramics has been found to be independent of the sample thickness and it increases with the heat-treatment temperature. It has been further revealed that the dielectric property is mainly governed by a highly resistive surface layer. The XPS results of Mn 2p and O 1s suggest that the surface layer is formed by oxygen diffusion and surface chemisorption at grain boundaries during the heat treatment in air. The chemisorption of oxygen in grain boundaries, which leads to the highly resistive surface layer, is the origin of the varistor property of SrTiO3 ceramics. 相似文献
92.
生态的思想结合现实的设计往往需要各方面的努力。美国南方松木构系统作为材料供应在物质循环和能量消耗方面,为设计师特别是景观设计师提供了良好的生态环保途径。南方松不仅有着较完备的加工和配备系统及等级评定和检测体系,而且在设计实践方面范围宽广,运用极其灵活,在国内外都留下了诸多佳例。 相似文献
93.
94.
为提高喷水推进器进水流道的流动性能,在给定进水流道出口直径D、流道高度H和流道总长度L等条件下,针对目标变量流道效率η、出口速度加权平均角θ和出口速度不均匀系数ξ,基于响应面方法对倾斜角α和过渡段半径RT进行优化设计。采用中心复合设计法和拉丁超立方法生成35组样本点,建立目标变量随设计变量变化的响应面模型,进行局部敏感性和全局敏感性分析,发现倾斜角α对不同目标变量的影响程度均高于过渡段半径RT. 采用多目标遗传算法对η、θ和ξ进行优化分析,得到满足条件的Pareto解。研究结果表明:优化之后,η从91.2%提高至94.1%,θ从82.5°提高至87.1°,ξ从0.152降低至0.068. 相似文献
95.
96.
Algae are one of the most important disinfection by-product (DBP) precursors in aquatic environments. The contents of DBP precursors in algae are influenced by not only environmental factors but also some xenobiotics. Trihalomethane formation potential (THMFP) in both the separate and interactive pollution of Microcystis aeruginosa and Nitrobenzene (NB) was investigated in batch experiment to discover the effects of xenobiotics on the yield of DBP precursors in the algal solution. The results show that in the separate NB solution, NB did not react with Cl2 to form trihalomethane (THM), whereas in the algae solution, THMFP had a significant positive linear correlation with M. aeruginosa density in both solution and extracellular organic matter (EOM). The correlation coefficients were 0.9845 (p = 3.567 × 10−4) and 0.9854 (p = 1.406 × 10−4), respectively. According to regression results, about 77.9% of the total THMFP came from the algal cells, while the rest came from EOM. When the interactive pollution of M. aeruginosa and NB occurred, the growth of algae was inhibited by NB. The density of M. aeruginosa in a high concentration NB solution (280 μg/L) was only 71.1% of that in the solution without NB after 5 days of incubation. However, THMFP in the mixture (algae and NB) and the EOM did not change significantly, and the productivity of THMFP by the algae (THMFP/108cells) increased with the increase in NB concentration. There was a significant linear correlation between THMFP/108cell and NB concentration (r = 0.9117, p < 0.01), which shows the contribution of the algae to THM formation was enhanced by NB. This result might be caused by the increased protein productivity and the biodegradation of NB by M. aeruginosa. 相似文献
97.
The bio-reaction of nitrobenzene (NB) with Microcystis aeruginosa was investigated at different initial algal densities and NB concentrations by performing static experiments. The results showed that the elimination of NB was enhanced by the bio-reaction, and the reaction rate varied as a function of the reaction time. Moreover, the reaction rate was significantly affected by the algal density and NB concentration. A kinetic analysis showed that the elimination of NB in a solution without algae appeared to be pseudo-first-order with respect to the NB concentration, whereas a first-order model was too oversimplified to describe the elimination of NB in a solution with algae. Assuming that different algal cells have the same effect on the bio-reaction under the same conditions, the bio-reaction can be described as dCNB = −k0CAmANBndt (where k0 is the reaction rate constant, CA is the algae density and CNB is the concentration of NB). When the growth of algae was not considered, the value of k0, m and n were 8.170 × 10−4, 0.5887 and 1.692, respectively. Alternatively, when algae were in the exponential growth phase, the value of k0, m and n were 1.6871 × 10−5, 0.7248 and 2.5407, respectively, according to a nonlinear fitting analysis. The kinetic model was also used to elucidate the effect of nutritional limitation on the bio-reaction. 相似文献
98.
对鄂尔多斯盆地中生界三叠系延长组成藏组合进行了系统的划分。在划分过程中,主要根据成藏组合的定义,并充分考虑目的层的:①烃源岩分布和砂体分布;②构造、古构造分布、主要断裂分布及油气运移疏导系统空间分布;③所在成藏组合主要烃源岩分布;④所在成藏组合盖层分布,特别是区域性盖层分布。另外,还考虑目前认识的构造圈闭及可能的其他圈闭分布情况,并分析含油气系统的保存情况。盆地中生界延长组划分为6个成藏组合:长10-长7下部成藏组合、长7-长5中部成藏组合、长7-长4+5中部成藏组合、长4+5-长3上部成藏组合、长4+5-长2上部成藏组合和长4-长1上部成藏组合。通过对各组合的生、储、盖层分析,认为中生界成藏组合主要分布在伊-陕斜坡西北部、东南部、西南部和天环坳陷南部。 相似文献
99.
100.
通过迦尔瓦尼置换反应在不同的Ag+溶液中制备出了铜基银枝晶,采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和电化学工作站分别对样品的结构、微观形貌以及电化学性能进行了表征。结果表明,随着溶液中Ag+浓度和反应时间的增加,银的形貌从团簇状向树枝状转变,氧还原电催化性能也增强;在相同浓度Ag+溶液中,SO42-比NO3-更能促进枝晶的生长,但当阴离子是NO3-时比阴离子是SO42-时所制备的银枝晶的氧还原电催化性能更好;在10 mmol/L AgNO3溶液中,反应时间为1800 s时制备的银枝晶电极使H2O2的还原峰电流最大,在0.1 mol/L Na2SO4+5mmol/L H2O2溶液中,恒电位为-0.32 V时,其稳态电流密度可达2.83 mA/cm2。初步提出了银枝晶的生长机制和H2O2的氧还原催化机制。 相似文献