全文获取类型
收费全文 | 1558篇 |
免费 | 74篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 22篇 |
综合类 | 5篇 |
化学工业 | 301篇 |
金属工艺 | 54篇 |
机械仪表 | 33篇 |
建筑科学 | 116篇 |
能源动力 | 35篇 |
轻工业 | 88篇 |
水利工程 | 16篇 |
石油天然气 | 5篇 |
无线电 | 181篇 |
一般工业技术 | 294篇 |
冶金工业 | 199篇 |
原子能技术 | 14篇 |
自动化技术 | 274篇 |
出版年
2023年 | 10篇 |
2022年 | 12篇 |
2021年 | 24篇 |
2020年 | 23篇 |
2019年 | 29篇 |
2018年 | 43篇 |
2017年 | 26篇 |
2016年 | 37篇 |
2015年 | 30篇 |
2014年 | 66篇 |
2013年 | 100篇 |
2012年 | 76篇 |
2011年 | 88篇 |
2010年 | 61篇 |
2009年 | 61篇 |
2008年 | 78篇 |
2007年 | 87篇 |
2006年 | 86篇 |
2005年 | 64篇 |
2004年 | 65篇 |
2003年 | 35篇 |
2002年 | 41篇 |
2001年 | 39篇 |
2000年 | 34篇 |
1999年 | 25篇 |
1998年 | 44篇 |
1997年 | 32篇 |
1996年 | 27篇 |
1995年 | 24篇 |
1994年 | 23篇 |
1993年 | 14篇 |
1992年 | 16篇 |
1991年 | 5篇 |
1990年 | 21篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 14篇 |
1984年 | 20篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 18篇 |
1980年 | 23篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 7篇 |
1973年 | 4篇 |
排序方式: 共有1637条查询结果,搜索用时 15 毫秒
1.
John D. Rodney S. Deepapriya M. Cyril Robinson C. Justin Raj Suresh Perumal Byung Chul Kim S. Krishnan S. Jerome Das 《International Journal of Hydrogen Energy》2021,46(54):27585-27596
The production of hydrogen, a favourable alternative to an unsustainable fossil fuel remains as a significant hurdle with the pertaining challenge in the design of proficient, highly productive and sustainable electrocatalyst for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, the dysprosium (Dy) doped copper oxide (Cu1-xDyxO) nanoparticles were synthesized via solution combustion technique and utilized as a non-noble metal based bi-functional electrocatalyst for overall water splitting. Due to the improved surface to volume ratio and conductivity, the optimized Cu1-xDyxO (x = 0.01, 0.02) electrocatalysts exhibited impressive HER and OER performance respectively in 1 M KOH delivering a current density of 10 mAcm?2 at a potential of ?0.18 V vs RHE for HER and 1.53 V vs RHE for OER. Moreover, the Dy doped CuO electrocatalyst used as a bi-functional catalyst for overall water splitting achieved a potential of 1.56 V at a current density 10 mAcm?2 and relatively high current density of 66 mAcm?2 at a peak potential of 2 V. A long term stability of 24 h was achieved for a cell voltage of 2.2 V at a constant current density of 30 mAcm?2 with only 10% of the initial current loss. This showcases the accumulative opportunity of dysprosium as a dopant in CuO nanoparticles for fabricating a highly effective and low-cost bi-functional electrocatalyst for overall water splitting. 相似文献
2.
A historical review of licensing among industrial/organizational (I/O) psychologists demonstrates that the American Psychological Association (APA) policy on such licensing is inconsistent. Arguments for and against licensure for this group are presented. Job analysis and APA data are drawn upon to show that few I/O activities may pose the personal risk that would seem to require the protection of a license. Alternatives are discussed for changes in present APA policy and state licensing requirements. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
在目前的系列文章中,我正在阐述项目管理的八个学派。前两期我讨论了(硬)系统学派和合同学派(治理学派的一部分)。从历史沿革来看下一个出现的学派是成功和失败学派,不过去年我已经以此为主题撰写过一系列文章,因此这里就不再赘述。本期我将转而讨论过程学派,如图1所示,过程学派坐落在迄今为止讨论过的其他三个学派之间。 相似文献
4.
在基于项目的组织中实现创新 在本节我们将探讨如何在项目环境中进行创新.首先我们来了解一下人们进行改变,进而实现创新的规律;然后我们介绍两种截然不同的管理创新的方法,即常用的线性推理方法和有机推进法;最后,我们对它们的优缺点做一个比较,看看它们各自适用于什么情况. 相似文献
5.
6.
Off-Site Exposure to Respirable Aerosols Produced during the Disk-Incorporation of Class B Biosolids
Swee Yang Low Tania Paez-Rubio Carolina Baertsch Matthew Kucharski Jordan Peccia 《Canadian Metallurgical Quarterly》2007,133(10):987-994
Field experiments were conducted at a Class B biosolids land application site in central Arizona to measure, model, and source-track the off-site transport of aerosols emitted when biosolids were disk-incorporated into soils. Real-time PM10 monitoring provided time-resolved aerosol information sufficient for verifying both off-site concentration and off-site exposure time model results. Under the conditions considered and at a distance of 165?m from the aerosol source, biosolids disk-incorporation resulted in an intermittent exposure to biosolids-derived aerosol concentration between 15 and 40?μg/m3 and an inhalable biosolids dose between 2 and 8?μg. Transport modeling predicted that these doses will decrease with increasing wind speed. In addition, three DNA sequence-based biosolids source tracking methods were applied to aerosol samples and confirmed the presence of biosolids in aerosols at 5, 65, and 165?m from the aerosol source. Field measurements and modeling indicate that the nature of biosolids-derived aerosol exposure is a series of intermittent high concentration puffs, rather than a continuous low concentration. 相似文献
7.
Transformations for nonideal uniform circular arrays operating in correlated signal environments 总被引:2,自引:0,他引:2
Buon Kiong Lau Yee Hong Leung Yanqun Liu Kok Lay Teo 《Signal Processing, IEEE Transactions on》2006,54(1):34-48
The Davies transformation is a method to transform the steering vector of a uniform circular array (UCA) to one with Vandermonde form. As such, it allows techniques such as spatial smoothing for direction-of-arrival (DOA) estimation in a correlated signal environment, developed originally for uniform linear arrays, to be applied to UCAs. However, the Davies transformation can be highly sensitive to perturbations of the underlying array model. This paper presents a method for deriving a more robust transformation using optimization techniques. The effectiveness of the method is illustrated through a number of DOA estimation examples. 相似文献
8.
The authors present a method for solving a class of optimization problems with nonsmooth constraints. In particular, they apply the method to the design of narrowband minimum-power antenna array processors which are robust in the presence of errors such as array element placement, look direction misalignment, and frequency offset. They first show that the constrained minimum power problem has a unique global minimum provided that the constraint set is nonempty. Then it is shown how the design problem derived directly from considerations of the sensitivity of the antenna array processor to errors can be transformed into a quadratic programming problem with linear inequality constraints which can be solved efficiently by the standard active set strategy. They also present numerical results for two types of nonsmooth constraints developed to provided robustness. These results confirm the effectiveness of the method 相似文献
9.
Taijiro Nonaka Rodney J. Clifton Taichiro Okazaki 《International Journal of Impact Engineering》1996,18(7-8):889-898
An analysis is presented of longitudinal waves in a thin elastic column. Velocity is specified at one end, and the boundary condition at the other end is expressed in terms of a range of effective impedances of an attached structure. Propagation, reflection and interference of the waves are followed by the method of characteristics. Integration of differential equations along characteristics yields the wave-induced stress, which is then applied to problems of earthquake excitation. Numerical examples are given for recorded updown ground motion of the Kobe Earthquake. 相似文献
10.
When rolled out for its first customer in 1995, the 777 will be the first new Boeing commercial airplane in more than ten years. Since the introduction of the last two Boeing planes, the 767 and 757, the science and technology of titanium alloys has come a long way. Some of the advances have led to new applications of titanium\3-with its accompanying performance benefits\3-on the 777. 相似文献