全文获取类型
收费全文 | 2978篇 |
免费 | 258篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 54篇 |
综合类 | 11篇 |
化学工业 | 871篇 |
金属工艺 | 132篇 |
机械仪表 | 104篇 |
建筑科学 | 77篇 |
矿业工程 | 4篇 |
能源动力 | 121篇 |
轻工业 | 264篇 |
水利工程 | 14篇 |
石油天然气 | 9篇 |
无线电 | 456篇 |
一般工业技术 | 527篇 |
冶金工业 | 157篇 |
原子能技术 | 31篇 |
自动化技术 | 416篇 |
出版年
2024年 | 6篇 |
2023年 | 53篇 |
2022年 | 55篇 |
2021年 | 139篇 |
2020年 | 104篇 |
2019年 | 120篇 |
2018年 | 128篇 |
2017年 | 143篇 |
2016年 | 171篇 |
2015年 | 94篇 |
2014年 | 145篇 |
2013年 | 217篇 |
2012年 | 213篇 |
2011年 | 244篇 |
2010年 | 171篇 |
2009年 | 146篇 |
2008年 | 139篇 |
2007年 | 110篇 |
2006年 | 95篇 |
2005年 | 69篇 |
2004年 | 59篇 |
2003年 | 70篇 |
2002年 | 69篇 |
2001年 | 44篇 |
2000年 | 47篇 |
1999年 | 29篇 |
1998年 | 64篇 |
1997年 | 40篇 |
1996年 | 46篇 |
1995年 | 32篇 |
1994年 | 13篇 |
1993年 | 12篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 9篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1972年 | 3篇 |
1971年 | 3篇 |
排序方式: 共有3248条查询结果,搜索用时 15 毫秒
11.
12.
Effect of Supports and Promoters on the Performance of Ni-Based Catalysts in Ethanol Steam Reforming
Thanh Khoa Phung Thong Le Minh Pham Anh-Nga T. Nguyen Khanh B. Vu Ha Ngoc Giang Tuan-Anh Nguyen Thanh Cong Huynh Hong Duc Pham 《化学工程与技术》2020,43(4):672-688
Ethanol steam reforming (ESR) is one of the potential processes to convert ethanol into valuable products. Hydrogen produced from ESR is considered as green energy for the future and can be an excellent alternative to fossil fuels with the aim of mitigating the greenhouse gas effect. The ESR process has been well studied, using transition metals as catalysts coupled with both acidic and basic oxides as supports. Among various reported transition metals, Ni is an inexpensive material with activity comparable to that of noble metals, showing promising ethanol conversion and hydrogen yields. Additionally, different promoters and supports were utilized to enhance the hydrogen yield and the catalyst stability. This review summarizes and discusses the influences of the supports and promoters of Ni-based catalysts on the ESR process. 相似文献
13.
14.
15.
We generalize the Negation-as-Failure procedure for disjunctive logic programming. Then we compare our method with related methods in the literature. We also propose a new completion theory for disjunctive logic programs which allows some program clauses to have inclusive meaning and the others exclusive meaning. 相似文献
16.
Choong Do Lee 《Metals and Materials International》2002,8(3):283-288
In the present study, the effect of microporosity on the tensile properties of as-cast AZ91D magnesium alloy was investigated through experimental observation and numerical prediction. The test specimens were fabricated by die-casting and gravity-casting. For gravity-casting, the inoculation and use of various metallic moulds were applied to obtain a wide range of microporosity. The deficiency of the interdendritic feeding of the liquid phase acted as a dominant mechanism on the formation of the micropores in the Mg?Al-alloys, rather than the evolution of hydrogen gas. Although tensile strength and elongation has a nonlinear and very intensive dependence upon microporosity, the yield strength appeared to have a linear relationship with microporosity. However, it was possible to quantitatively estimate the linear contribution of microporosity on the individual tensile property for a range of microporosity, which was below about 1%. The numerical prediction suggests that the effect of microporosity on fractured strength and elongation decreased as the strain hardening exponent increased. Furthermore, the shape and distribution of micropores may play a more dominant role than local plastic deformation on the tensile behavior of AZ91D alloy. 相似文献
17.
Xiaomeng Shi Jian-Guo Ma Kiat Seng Yeo Manh Anh Do Erping Li 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2005,13(9):1060-1071
This paper investigates the properties of the on-wafer interconnects built in a 0.18-/spl mu/m CMOS technology for RF applications. A scalable equivalent circuit model is developed. The model parameters are extracted directly from the on-wafer measurements and formulated into empirical expressions. The expressions are in functions of the length and the width of the interconnects. The proposed model can be easily implemented into commercial RF circuit simulators. It provides a novel solution to include the frequency-variant characteristics into a circuit simulation. The silicon-verified accuracy is proved to be up to 25 GHz with an average error less than 2%. Additionally, equivalent circuit model for longer wires can be obtained by cascading smaller subsections together. The scalability of the propose model is demonstrated. 相似文献
18.
K.D. Do Author Vitae Z.P. Jiang Author Vitae Author Vitae H. Nijmeijer Author Vitae 《Automatica》2004,40(1):117-124
This paper presents a method to design an output-feedback controller that simultaneously solves global asymptotic stabilization and tracking of an underactuated omni-directional intelligent navigator—a spherical underwater vehicle moving in a horizontal plane (i.e. at a constant depth). The vehicle does not have a sway actuator and has only position and orientation measurements available. The control development is based on Lyapunov's direct method, backstepping technique and use of interconnected structure of the vehicle dynamics. Numerical simulations demonstrate the results. 相似文献
19.
Sverak J.G. Wang W. Gervais Y. Do X.-D. Mukhedkar D. 《Power Delivery, IEEE Transactions on》1992,7(3):1196-1206
An improved multivariable, probabilistic method for the safety analysis of power grounding systems is presented. The application of this method is demonstrated in four examples. The first three examples illustrate the practical evaluation of one new and two existing substation grounding grids when the substation is connected to an overhead distribution system. The fourth example ascertains the relative impact of a difference between the S curve of IEC Publication 479 and Dalziel's equation for the allowable body current used in ANSI/IEEE Std 80-1986 on the validity of an exposure model based on the requirements of Std 80. In this example, the statistical data on ground faults have been taken from actual system records. Further possible refinements of the exposure model are discussed 相似文献
20.
Minh Lequan Rose Marie Lequan Kathleen Chane-ching Anne-claude Callier Marguerite Barzoukas Alain Fort 《Advanced functional materials》1992,1(5):243-247
Samples of {4-(dimethylamino) stilben Z & E 4'-yl} dimesityl borane (BNS) were synthesised and investigated for their non-linear optical properties. The results show that the quadratic hyperpolarisability of the Z-isomer is smaller than that of the E-isomer, the beta value found for the latter being as high as 60 × 10?30 esu. 相似文献