首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1370篇
  免费   53篇
  国内免费   2篇
电工技术   10篇
化学工业   282篇
金属工艺   59篇
机械仪表   38篇
建筑科学   118篇
矿业工程   2篇
能源动力   65篇
轻工业   200篇
水利工程   4篇
石油天然气   4篇
无线电   62篇
一般工业技术   286篇
冶金工业   64篇
原子能技术   20篇
自动化技术   211篇
  2023年   5篇
  2022年   17篇
  2021年   26篇
  2020年   14篇
  2019年   17篇
  2018年   18篇
  2017年   32篇
  2016年   28篇
  2015年   29篇
  2014年   41篇
  2013年   84篇
  2012年   61篇
  2011年   106篇
  2010年   65篇
  2009年   80篇
  2008年   91篇
  2007年   88篇
  2006年   55篇
  2005年   55篇
  2004年   52篇
  2003年   43篇
  2002年   46篇
  2001年   27篇
  2000年   20篇
  1999年   14篇
  1998年   30篇
  1997年   26篇
  1996年   19篇
  1995年   16篇
  1994年   12篇
  1993年   14篇
  1992年   9篇
  1991年   11篇
  1990年   13篇
  1989年   12篇
  1988年   16篇
  1987年   13篇
  1986年   13篇
  1985年   12篇
  1984年   12篇
  1983年   13篇
  1982年   8篇
  1981年   8篇
  1980年   8篇
  1979年   8篇
  1978年   7篇
  1976年   7篇
  1974年   7篇
  1973年   3篇
  1972年   4篇
排序方式: 共有1425条查询结果,搜索用时 31 毫秒
991.
A three factorial experimental design involving electrical stimulation (ES/NES), wrapping (wrapped/unwrapped) and pre rigor temperature (15 °C or 35 °C) was applied to 70 beef M. longissimus lumborum muscles to obtain a wide variation in shear force and drip loss. The shear force of all treatment groups decreased during ageing. As anticipated, wrapping and electrical stimulation had positive effects on shear force. However, high pre rigor temperature (35 °C) did not result in higher shear force values if the muscles were electrically stimulated, wrapped or both. The results suggested that electrical stimulation protects against the negative effects of high pre rigor temperatures. The drip loss of all treatment groups increased during ageing in a manner that was unrelated to treatment but was correlated to tenderness (r2 = 0.70; p < 0.0001). It was concluded that the application of electrical stimulation, whatever the pre rigor temperature, protects beef from toughening through the prevention of rigor shortening and the avoidance of inhibition of ageing enzymes.  相似文献   
992.
A flexible high-resolution sensor capable of measuring the distribution of pressure beneath the foot via a microfabricated optical waveguide system is presented. The uniqueness of the system is in its batch fabrication process, which involves a microfabrication molding technique with polydimethylsiloxane (PDMS) as the optical medium. The sensor manufacturing technique is described in detail, the optical performance of the waveguides is quantified and the effect of using a matching fluid to improve fiber-coupling efficiency is demonstrated. Mechanical loading tests were performed on a 4 x 4 array with a 2-mm spacing between sensing elements. Loading displacement curves were obtained using a 0 to 0.4 mm triangle loading profile. A force of 0.28 N applied to one of the sensing elements produced a displacement of a 0.325 mm and 39% change in the output light intensity. Multiple loadings were conducted to demonstrate the repeatability of the sensor. A force image algorithm with a two-layer neural network system was used to identify four load magnitudes and four different shaped applicators. All four shapes were successfully identified with the neural network.  相似文献   
993.
Suspension plasma spraying (SPS) has been shown as a promising process to produce porous columnar strain tolerant coatings for thermal barrier coatings (TBCs) in gas turbine engines. However, the highly porous structure is vulnerable to crack propagation, especially near the topcoat-bondcoat interface where high stresses are generated due to thermal cycling. A topcoat layer with high toughness near the topcoat-bondcoat interface could be beneficial to enhance thermal cyclic lifetime of SPS TBCs. In this work, a bilayer coating system consisting of first a dense layer near the topcoat-bondcoat interface followed by a porous columnar layer was fabricated by SPS using Yttria-stabilised zirconia suspension. The objective of this work was to investigate if the bilayer topcoat architecture could enhance the thermal cyclic lifetime of SPS TBCs through experiments and to understand the effect of the column gaps/vertical cracks and the dense layer on the generated stresses in the TBC during thermal cyclic loading through finite element modeling. The experimental results show that the bilayer TBC had significantly higher lifetime than the single-layer TBC. The modeling results show that the dense layer and vertical cracks are beneficial as they reduce the thermally induced stresses which thus increase the lifetime.  相似文献   
994.
Colliander  Cristian  Ahlgren  Per 《Scientometrics》2012,90(2):675-685
The measurement of similarity between objects plays a role in several scientific areas. In this article, we deal with document–document similarity in a scientometric context. We compare experimentally, using a large dataset, first-order with second-order similarities with respect to the overall quality of partitions of the dataset, where the partitions are obtained on the basis of optimizing weighted modularity. The quality of a partition is defined in terms of textual coherence. The results show that the second-order approach consistently outperforms the first-order approach. Each difference between the two approaches in overall partition quality values is significant at the 0.01 level.  相似文献   
995.
Polyaniline (PANI) was doped with different lithium salts such as LiPF6 and LiClO4 and evaluated as cathode-active material for application in room-temperature lithium batteries. The doped PANI was characterized by FTIR and XPS measurements. In the FTIR spectra, the characteristic peaks of PANI are shifted to lower bands as a consequence of doping, and it is more shifted in the case of PANI doped with LiPF6. The cathodes prepared using PANI doped with LiPF6 and LiClO4 delivered initial discharge capacities of 125 mAh g?1 and 112 mAh g?1 and stable reversible capacities of 114 mAh g?1 and 81 mAh g?1, respectively, after 10 charge–discharge cycles. The cells were also tested using polymer electrolyte, which delivered highest discharge capacities of 142.6 mAh g?1 and 140 mAh g?1 and stable reversible capacities of 117 mAh g?1 and 122 mAh g?1 for PANI-LiPF6 and PANI-LiClO4, respectively, after 10 cycles. The cathode prepared with LiPF6 doped PANI shows better cycling performance and stability as compared to the cathode prepared with LiClO4 doped PANI using both liquid and polymer electrolytes.  相似文献   
996.
This paper examines the effectiveness of a range of aluminum induced textured (AIT) glass topographies at enhancing light absorption in silicon thin film diode structures deposited on the textured glass side, operating in the superstrate configuration. The aluminum layer used to produce the AIT can be deposited either by thermal evaporation or magnetron sputtering. Varying AIT process parameters produces a wide range of feature roughness and uniformity, providing scope to optimize texture effectiveness and process repeatability. We report strong correlation between the degree of absorption enhancement from these textures and both dark field microscope images of the AIT glass and reduction of the interference envelope in spectral reflectance of the deposited silicon films. Our findings corroborate earlier modeling work based on ray tracing, which predicted that the best enhancement occurs when the feature size is close to the film thickness. In this paper we investigate AIT samples in the 1 – 3 µm film thickness range, some of which trap light in silicon as strongly as at the Lambertian limit. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
997.
We introduce FlexCore, the first exemplar of an architecture based on the FlexSoC framework. Comprising the same datapath units found in a conventional five-stage pipeline, the FlexCore has an exposed datapath control and a flexible interconnect to allow the datapath to be dynamically reconfigured as a consequence of code generation. Additionally, the FlexCore allows specialized datapath units to be inserted and utilized within the same architecture and compilation framework. This study shows that, in comparison to a conventional five-stage general-purpose processor, the FlexCore is up to 40% more efficient in terms of cycle count on a set of benchmarks from the embedded application domain. We show that both the fine-grained control and the flexible interconnect contribute to the speedup. Furthermore, according to our VLSI implementation study, the FlexCore architecture offers both time and energy savings. The exposed FlexCore datapath requires a wide control word. The conducted evaluation confirms that this increases the instruction bandwidth and memory footprint. This calls for efficient instruction decoding as proposed in the FlexSoC framework.  相似文献   
998.
The adhesion strength of high-velocity oxyfuel thermally sprayed coatings is of prime importance when thick coatings are to be sprayed in repair applications. In this study, relationships between process parameters, particle in-flight characteristics, residual stresses, and adhesion strength were explored. The most important process parameters that influence HVOF sprayed IN718 coating adhesion strength on IN718 substrate material were identified. Residual stress distributions were determined using the modified layer removal method, and adhesion strength was measured using an in-house-developed tensile test. Relationships between process parameters, particle in-flight characteristics, coating microstructure, and adhesion strength were established. Particle temperature, particle velocity, substrate preparation, and deposition temperature were identified as critical parameters to attain high adhesion strength. Controlling these parameters can significantly improve the adhesion strength, thus enabling thick coatings to be sprayed for repair applications.  相似文献   
999.
The aim of this study is to relate the influence of ground water to the properties of bentonite gels. It has been proposed that compacted bentonite could be used as a buffer substance around canisters containing nuclear waste deposited about 500 m down in the bedrock. The bentonite shield is thought to provide a zone of low permeability which on contact with ground water will swell into cracks formed in the rock.Visual inspection and measurements of the amount of particles released from a bentonite gel by light-scattering showed that while particles are released in distilled water, they are coagulated when in contact with ground water with composition varying within reasonable limits, with the result that the release of particles is negligibly small.Studies of sedimentation volumes after ultracentrifugation also clearly indicated that the bentonite in contact with ground water in the repository forms a completely coagulated gel.It was shown that calcium ions diffuse rapidly into the gel that is in contact with ground water. This implies that bentonite gel which is initially partially in its sodium form will be completely exchanged to its calcium form when brought into contact with ground water. This ensures that it remains coagulated and does not release any particles.  相似文献   
1000.
This paper describes the implementation of the Solo operating system written in Concurrent Pascal.* It explains the overall structure and details of the system in which concurrent processes communicate by means of a hierarchy of monitors and classes. The concurrent program is a sequence of nearly independent components of less than one page of text each. The system has been operating since May 1975.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号