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   41345篇
  免费   2377篇
  国内免费   36篇
电工技术   279篇
综合类   29篇
化学工业   7469篇
金属工艺   739篇
机械仪表   777篇
建筑科学   1287篇
矿业工程   74篇
能源动力   825篇
轻工业   5371篇
水利工程   375篇
石油天然气   170篇
武器工业   4篇
无线电   2343篇
一般工业技术   7535篇
冶金工业   10608篇
原子能技术   204篇
自动化技术   5669篇
  2023年   354篇
  2022年   325篇
  2021年   879篇
  2020年   745篇
  2019年   694篇
  2018年   1523篇
  2017年   1528篇
  2016年   1580篇
  2015年   1133篇
  2014年   1448篇
  2013年   2786篇
  2012年   2427篇
  2011年   2290篇
  2010年   1798篇
  2009年   1594篇
  2008年   1876篇
  2007年   1646篇
  2006年   1229篇
  2005年   1041篇
  2004年   955篇
  2003年   845篇
  2002年   749篇
  2001年   484篇
  2000年   471篇
  1999年   624篇
  1998年   3357篇
  1997年   2012篇
  1996年   1304篇
  1995年   764篇
  1994年   654篇
  1993年   642篇
  1992年   214篇
  1991年   225篇
  1990年   232篇
  1989年   222篇
  1988年   198篇
  1987年   173篇
  1986年   181篇
  1985年   211篇
  1984年   185篇
  1983年   135篇
  1982年   165篇
  1981年   173篇
  1980年   154篇
  1979年   128篇
  1978年   120篇
  1977年   201篇
  1976年   416篇
  1975年   90篇
  1973年   82篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
1.
Brito  Claúdia  Esteves  Marisa  Peixoto  Hugo  Abelha  António  Machado  José 《Wireless Networks》2022,28(3):1269-1277
Wireless Networks - Continuous ambulatory peritoneal dialysis (CAPD) is a treatment used by patients in the end-stage of chronic kidney diseases. Those patients need to be monitored using blood...  相似文献   
2.
3.

Particles generated by wood machining have a proven impact on the health of users and woodworkers. The aim of this study was to quantify and describe wood particles in solid and gas phases to reliably and reproducibly characterise these emissions. First, we developed an experimental device that produced particles from solid wood and wood-based panels using portable machine tools. The objective was to study the particles emitted by wood machining while avoiding ambient pollution. Based on own technical specifications, the experimental system was defined and composed of various elements that integrated treatment of inlet air through wood machining to the analysis section that allows solid and gas phases. The first experiments were carried out in sanding and sawing modes on materials used in construction, including solid wood (spruce) and composite panels (particle board (PB), oriented strand board (OSB), and medium density fibreboard (MDF)). Wood-based panels showed more emissive behaviour than solid wood, both for the solid phase and the gas phase. These tests validate the feasibility of generating and measuring particles and emissions of volatile organic compounds (VOCs). Further modifications to the experimental device would enable us to integrate additional devices, such as toxicological ones, to better understand the impact of these wood particles on the health of woodworkers.

  相似文献   
4.
5.
This work deals with the additive manufacturing and characterization of hydroxyapatite scaffolds mimicking the trabecular architecture of cancellous bone. A novel approach was proposed relying on stereolithographic technology, which builds foam-like ceramic scaffolds by using three-dimensional (3D) micro-tomographic reconstructions of polymeric sponges as virtual templates for the manufacturing process. The layer-by-layer fabrication process involves the selective polymerization of a photocurable resin in which hydroxyapatite particles are homogeneously dispersed. Irradiation is performed by a dynamic mask that projects blue light onto the slurry. After sintering, highly-porous hydroxyapatite scaffolds (total porosity ~0.80, pore size 100-800 µm) replicating the 3D open-cell architecture of the polymeric template as well as spongy bone were obtained. Intrinsic permeability of scaffolds was determined by measuring laminar airflow alternating pressure wave drops and was found to be within 0.75-1.74 × 10−9 m2, which is comparable to the range of human cancellous bone. Compressive tests were also carried out in order to determine the strength (~1.60 MPa), elastic modulus (~513 MPa) and Weibull modulus (m = 2.2) of the scaffolds. Overall, the fabrication strategy used to print hydroxyapatite scaffolds (tomographic imaging combined with digital mirror device [DMD]-based stereolithography) shows great promise for the development of porous bioceramics with bone-like architecture and mass transport properties.  相似文献   
6.
Journal of Applied Electrochemistry - The present work reports the development of screen-printed electrode (SPE) using flexible polyester sheets modified with nanodiamond (ND), Au nanoparticles...  相似文献   
7.
Mixing by gas injection is an operation used in industrial processes such as wastewater treatment, metallurgy, or methanization in which pressurized gas is injected into a fluid in order to reduce concentrations and temperatures gradients. This study demonstrates how the CFD toolbox OpenFOAM can be used to simulate such flows. Experimental measurements and observations have been performed on a pilot-scale reactor where pressurized air is injected in a yield stress fluid. The volume of fluid method and an adaptive mesh with refinement at the interface have been used to track the gas inclusions. The numerical model accuracy has been assessed by comparing experimental and numerical results related to the bubble's frequency, dimensions, and rising velocities as well as the fluid recirculation, yielded, and unyielded regions in the tank. The influence of injection parameters such as the injection flow rate and the fluid rheological parameters has been quantified.  相似文献   
8.

In this article, we want to bolster a critical discussion of how the “home” is used in research on residential care, and additionally make sense of young and old residents’ feelings of resistance, through the lens of a critical geography of home. We illustrate how the home ideal might be provocative and frustrating for the residents, although previous studies point out that the ideal is used by staff and in policy to reassure residents of a sense of belonging and mastery. Examples from interviews with young unaccompanied boys as well as older residents living in residential care have been used and the analysis resulted in two themes: “Residents’ conflicting experiences of space” (shared space, restricted space and regulated space, and “Residents’ feelings of homelessness” (transitional space and encroached space). How the residents themselves understand the space that is called their home and why their home can stir ambivalent or negative feelings of isolation, exclusion, and homelessness, is relevant in order to avoid romanticizing home. Residents’ understanding of home can be different from the staff, a reminder that home is a much more complex notion than the rosy ideal.

  相似文献   
9.
The structural role of V in 28Li2O–72SiO2 (in mol%) lithium silicate glass doped with 0.5 mol% V2O5 was assessed using 29Si and 51V Nuclear Magnetic Resonance (NMR), Fourier-transform infrared (FTIR), and X-ray photoelectron (XPS) spectroscopy techniques. Despite the low amount of V2O5 used, the structural information obtained or deduced from the statistical analysis of the NMR data could explain the evolution of glass properties after V2O5 addition. The XPS results indicated that all vanadium exists in 5+ oxidation state. Both the 29Si NMR and FTIR data point toward an increase in the polymerization of the silicate network, caused by the V2O5 acting as network former, capable to form various tetrahedral units (for n = 0, 1, and 2) in the glasses. These units, which are similar to phosphate units, scavenge the Li+ ions and cause the silicate network to polymerize. However, in an overall balance, the entire glass network is depolymerized due to the additional nonbridging oxygens contributed by the vanadium polyhedra. The addition of vanadium causes the network to expand and increases the ionic conductivity.  相似文献   
10.
This study investigates the behavior of fruit and vegetable samples during drying. The experimental data are fitted to several different thin-layer drying models. Regression analysis is used to determine model parameters, while statistical indicators serve to evaluate the goodness of fit. The power function model gives the best fit for all examined samples. Based on this model, different drying and heat storage technologies can be combined to ensure that the required residual moisture content of an agricultural product is reached. It is demonstrated on the case of a specific Togolese processing plant that under favorable conditions, fossil fuel consumption can be decreased by 33 %.  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