全文获取类型
收费全文 | 30052篇 |
免费 | 3645篇 |
国内免费 | 1950篇 |
专业分类
电工技术 | 3472篇 |
技术理论 | 5篇 |
综合类 | 3278篇 |
化学工业 | 3722篇 |
金属工艺 | 955篇 |
机械仪表 | 1419篇 |
建筑科学 | 3710篇 |
矿业工程 | 1245篇 |
能源动力 | 1163篇 |
轻工业 | 2286篇 |
水利工程 | 1240篇 |
石油天然气 | 2723篇 |
武器工业 | 242篇 |
无线电 | 2331篇 |
一般工业技术 | 3158篇 |
冶金工业 | 1395篇 |
原子能技术 | 684篇 |
自动化技术 | 2619篇 |
出版年
2024年 | 437篇 |
2023年 | 498篇 |
2022年 | 1093篇 |
2021年 | 1274篇 |
2020年 | 1093篇 |
2019年 | 826篇 |
2018年 | 827篇 |
2017年 | 944篇 |
2016年 | 1135篇 |
2015年 | 1201篇 |
2014年 | 1849篇 |
2013年 | 1990篇 |
2012年 | 2177篇 |
2011年 | 2393篇 |
2010年 | 1799篇 |
2009年 | 1858篇 |
2008年 | 1693篇 |
2007年 | 1982篇 |
2006年 | 1742篇 |
2005年 | 1497篇 |
2004年 | 1204篇 |
2003年 | 1025篇 |
2002年 | 911篇 |
2001年 | 746篇 |
2000年 | 602篇 |
1999年 | 520篇 |
1998年 | 409篇 |
1997年 | 333篇 |
1996年 | 304篇 |
1995年 | 251篇 |
1994年 | 202篇 |
1993年 | 131篇 |
1992年 | 110篇 |
1991年 | 87篇 |
1990年 | 92篇 |
1989年 | 79篇 |
1988年 | 84篇 |
1987年 | 38篇 |
1986年 | 23篇 |
1985年 | 20篇 |
1984年 | 28篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1964年 | 10篇 |
1962年 | 7篇 |
1961年 | 8篇 |
1960年 | 9篇 |
1959年 | 8篇 |
1955年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
介绍了阳泉市煤矿采空区对公路建设所造成的危害,对其上覆岩层变形破坏的地质因素及其破坏机理作了分析,指出应该采取各种措施减少对公路的破坏。 相似文献
2.
氯蜡-70是—应用广泛、性能优良的精细化工产品,其色泽是—重要的技术指标,直接影响着产品的质量和应用。本文考察了合成反应过程导致生色的因素,指出原料中含有的少量环烷烃、芳烃、杂环有机物及少量无机杂质能影响产品的色泽,实验表明温度过高,光源波长选择不当也是致色的重要原因。研究了致色的过程,提出其生色历程是按照β-消除反应机理进行的,并做了具体描述。 相似文献
3.
Kenji Imura 《Color research and application》2007,32(3):195-200
In this article, a new method for measuring a total spectral radiance factor of a FWA‐treated sample illuminated by a specific standard illuminant is introduced. The method replaces an unstable real fluorescent standard by a bi‐spectral luminescent radiance factor data, which works as a virtual fluorescent standard (VFS) by knowing spectral intensity distributions of illuminations applied to the sample. The method utilizes two illuminations I1 and I2 whose relative spectral intensity distributions are different from each other and synthesizes a virtual illumination presenting the identical fluorescent spectral radiance factor to that presented by the standard illuminant with the VFS of the specific bi‐spectral luminescent radiance factor by linearly combining I1 and I2 with the suitable weighting factors. The applicability of the method is examined in principle by comparing ISO brightness and CIE whiteness index of fluorescent standard paper as a test sample obtained by this new method to the assigned values. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 195–200, 2007 相似文献
4.
5.
A statistical study of the particle shape and size of pure V2O5 and TiO2, and samples of coprecipitated V2O5---TiO2 catalysts with different V/Ti ratios, has been performed. They were also characterized by XRD, EDAX, SEM and XPS. The results showed that pure vanadium pentoxide is compose by large square or needle-shaped particles, while pure titanium dioxide has small and rounded ones. VTiO samples presented an area and shape, depending on the V/Ti ratio.
These results and the spectroscopical characterization conducted to a particle model of the catalysts. Those VOTi samples with high V/Ti ratio would have large V2O5 crystals acting as support of a V/TiO2 solid solution. In contrast, those samples with a low V/Ti ratio, would have the solid solution supporting vanadium pentoxide crystals. 相似文献
6.
B. E. Rytsar 《Cybernetics and Systems Analysis》2007,43(2):192-207
The paper considers the set-theoretical approach to the joint decomposition of systems of Boolean functions of variables specified
in different representation forms. The approach is based on the method of q-partitions of conjuncterms and concept of decomposition
clones. Theorems on joint decomposition of a system of full and partial functions are formulated. The approach is illustrated
by examples.
Parts I and II of this article are published in No. 5 (2001) and No. 1 (2002).
__________
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 39–58, March–April 2007. 相似文献
7.
8.
探讨了该厂化肥生产中碳铵发青的原因,通过硫化氢含量的测定,分析了系统内外影响因素,提出了解决措施,达到了不停车稳定产品质量的目的。 相似文献
9.
Transport phenomena studies on single phase “model” fluids are of limited value in biochemical engineering if they cannot be translated to the heterogeneous systems encountered in real fermentation processes. In this paper we discuss the utility of polymer solutions as models of filamentous fermentation broths for evaluation of: pipeline friction factors and impeller power numbers (turbine and helical ribbon). To a first approximation, polymer solutions can serve as suitable models for the prediction of laminar flow pressure drop in pipelines and turbulent power consumption in stirred tanks. However, results obtained on polymer solutions do not directly apply to filamentous fermentation broths for predictions of laminar flow impeller power consumption and the transition point for turbulent flow in stirred tanks. These discrepancies are believed to result from the existence of a time dependent yield stress in filamentous fermentation broths. 相似文献
10.
Daizo Kunii 《Chemical engineering science》1980,35(9):1887-1911
A general procedure is proposed for innovative research and development of gas-solid reactor systems, with a brief explanation of the significance of each step in the procedureBased upon the contacting mode between gas and solid phases, as well as the ways of supplying thermal energy to the reacting regions, various types of gas-solid reactor systems are classified by using tables of so called “matrix” form, for thermal cracking and gasification of heavy oils, gasification of coal, gasification of solid waste, calcination of limestone, clinkering of cement and reduction of iron ore.The importance of fundamental concepts is emphasized for successful research and development by presenting several examples; namely, calcination of limestone, thermal cracking of heavy oils and gasification of solid waste materials.In connection with the direction in which fundamental research should be oriented, four primary ways of thinking are proposed, which can be applied to obtain innovative ideas for further research and development in this field.One example of the author's practical experience was selected to show the role of the fundamental research in the course of large scale development. Finally the author outlines the role of chemical reaction engineering to innovate the novel gas-solid reactor systems which may be inevitable for simultaneous solution of the three big E's; namely, Energy, Environment and Economy. 相似文献