全文获取类型
收费全文 | 1728篇 |
免费 | 207篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 19篇 |
化学工业 | 502篇 |
金属工艺 | 45篇 |
机械仪表 | 63篇 |
建筑科学 | 63篇 |
矿业工程 | 2篇 |
能源动力 | 54篇 |
轻工业 | 376篇 |
水利工程 | 20篇 |
石油天然气 | 12篇 |
无线电 | 150篇 |
一般工业技术 | 268篇 |
冶金工业 | 147篇 |
原子能技术 | 13篇 |
自动化技术 | 203篇 |
出版年
2024年 | 8篇 |
2023年 | 22篇 |
2022年 | 41篇 |
2021年 | 106篇 |
2020年 | 81篇 |
2019年 | 74篇 |
2018年 | 96篇 |
2017年 | 101篇 |
2016年 | 98篇 |
2015年 | 92篇 |
2014年 | 90篇 |
2013年 | 144篇 |
2012年 | 129篇 |
2011年 | 120篇 |
2010年 | 97篇 |
2009年 | 83篇 |
2008年 | 72篇 |
2007年 | 50篇 |
2006年 | 43篇 |
2005年 | 44篇 |
2004年 | 32篇 |
2003年 | 23篇 |
2002年 | 17篇 |
2001年 | 20篇 |
2000年 | 17篇 |
1999年 | 19篇 |
1998年 | 49篇 |
1997年 | 37篇 |
1996年 | 28篇 |
1995年 | 21篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 3篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1974年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有1937条查询结果,搜索用时 296 毫秒
91.
Cavity walls are often proposed in the building envelope design as a solution for improving the thermal comfort of the occupants and reducing the adverse condensation effects on the building fabric. Although the behaviour of a non‐ventilated cavity wall is well‐known, more studies are required when cavity ventilation is allowed. In order to consistently predict the thermal behaviour of a naturally ventilated cavity wall, a convective model based on the integral equations of motion and enthalpy was developed and applied in the present study. The model is presented as a combination of two limiting cases of a steady laminar flow into the channel gap: fully developed flow and boundary layer flow. Conduction effects across the system are also included through a proper limiting case and then combined with the convective model. In addition a numerical CFD model was developed that provides solution for free convective flow configurations between two parallel conducting vertical walls. For comparison purposes, some test cases were simulated with the two models and a general good agreement was found between results. Finally, the integral model was applied to assess the thermal performance of a ventilated cavity wall for winter and summer conditions. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
92.
A localized Delaunay triangulation owns the following interesting properties for sensor and wireless ad hoc networks: it can
be built with localized information, the communication cost imposed by control information is limited, and it supports geographical
routing algorithms that offer guaranteed convergence. This paper presents two localized algorithms, fast localized Delaunay
triangulation 1 (FLDT1) and fast localized Delaunay triangulation 2 (FLDT2), that build a graph called planar localized Delaunay
triangulation, PLDel, known to be a good spanner of the Unit Disk Graph, UDG. Our algorithms improve previous algorithms with similar theoretical bounds in the following aspects: unlike previous work,
FLDT1 and FLDT2 build PLDel in a single communication step, maintaining a communication cost of O(n log n), which is within a constant of the optimal. Additionally, we show that FLDT1 is more robust than previous triangulation
algorithms, because it does not require the strict UDG connectivity model to work. The small signaling cost of our algorithms allows us to improve routing performance, by efficiently
using the PLDel graph instead of sparser graphs, like the Gabriel or the Relative Neighborhood graphs. 相似文献
93.
In this paper a realistic directional channel model that is an extension of the COST 273 channel model is presented. The model
uses a cluster of scatterers and visibility region generation based strategy with increased realism, due to the introduction
of terrain and clutter information. New approaches for path-loss prediction and line of sight modeling are considered, affecting
the cluster path gain model implementation. The new model was implemented using terrain, clutter, street and user mobility
information for the city of Lisbon, Portugal. Some of the model’s outputs are presented, mainly path loss and small/large-scale
fading statistics. 相似文献
94.
Ana A. Rodrigues Nilza A. Batista Vanessa P. Bavaresco Vitor Baranauskas Helder J. Ceragioli Alfredo C. Peterlevitz Arnaldo R. Santos William D. Belangero 《Carbon》2012,50(2):450-459
Polyvinyl alcohol (PVAl) hydrogel, alone and reinforced with two types of carbon nanoparticles, was studied in cultured cells to assess its potential use in treating osteochondral defects. The carbon nanoparticles were produced by hot-filament chemical vapour deposition. The carbon material was characterised with a Renishaw Invia Raman microscope system and the morphological particles were characterised with field emission scanning electron microscopy and high-resolution transmission electron microscopy. Cytotoxicity was evaluated by measuring the Vero fibroblast-type cells’ metabolic activity and studying their morphology. The osteogenic differentiation of mesenchymal stem cells obtained from rat bone marrow was evaluated by alkaline phosphatase (ALP) and alizarin red S (ARS) staining. Cell viability and morphology were assessed with thiazolyl blue tetrazolium bromide and scanning electron microscopy, respectively. The materials did not interfere with the viability, metabolic activity, morphology and spreading of either of the cell types analysed. Nodules of mineralised organic matrix were identified with ARS and ALP, confirming osteogenic differentiation. These results indicated higher concentration of ALP and mineralised matrix for PVAl with carbon nanoparticles. The results of this study indicate the potential use of carbon nanoparticles with PVAl hydrogels as orthopaedic biomaterials to treat osteochondral defects, but further in vivo investigations are still necessary. 相似文献
95.
Dr. Peter I. Dosa Dr. Tim Ward Dr. Rui E. Castro Prof. Dr. Cecília M. P. Rodrigues Prof. Dr. Clifford J. Steer 《ChemMedChem》2013,8(6):1002-1011
Ursodeoxycholic acid (UDCA) is a bile acid with demonstrated anti‐apoptotic activity in both in vitro and in vivo models. However, its utility is hampered by limited aqueous solubility. As such, water‐soluble prodrugs of UDCA could have an advantage over the parent bile acid in indications where intravenous administration might be preferable, such as decreasing damage from stroke or acute kidney injury. Five phosphate prodrugs were synthesized, including one incorporating a novel phosphoryloxymethyl carboxylate (POMC) moiety. These prodrugs were highly water‐soluble, but showed significant differences in chemical stability, with oxymethylphosphate prodrugs being the most unstable. In a series of NMR experiments, the POMC prodrug was bioactivated to UDCA by alkaline phosphatase (AP) faster than a prodrug containing a phosphate directly attached to the alcohol at the 3‐position of UDCA. Both of these prodrugs showed significant anti‐apoptotic activity in a series of in vitro assays, although the POMC prodrug required the addition of AP for activity, while the other compound was active without exogenous AP. 相似文献
96.
I. Galvão R.M. Leal D.M. Rodrigues A. Loureiro 《Journal of Materials Processing Technology》2013,213(2):129-135
The aim of this work is to study the influence of the shoulder geometry on friction stir welding of 1 mm-thick copper-DHP plates. The welds were produced using three different shoulder geometries, flat, conical and scrolled, and varying the rotation and traverse speeds of the tool. The flat shoulder tool proved to be inadequate for performing welds, because many defects were produced for all welding conditions. In turn, the scrolled shoulder tool is more effective than the conical one in the production of defect free welds. However, both geometries required a minimum rotational speed to avoid internal defects. For the same welding parameters, greater grain refinement, higher hardness and improved strength are also achieved in the nugget of the welds, using the scrolled tool. 相似文献
97.
S. Guriyanova B. Semin T. S. Rodrigues H.-J. Butt E. Bonaccurso 《Microfluidics and nanofluidics》2010,8(5):653-663
We measured the hydrodynamic drainage force of an aqueous, Newtonian liquid squeezed between two hydrophobic or two hydrophilic
surfaces by means of the colloidal probe technique. We controlled the wettability, the roughness, the topology, and also the
approaching velocity of the surfaces. We found that asperities on the surfaces caused an artificial decrease of the measured
drainage force that must be considered by the interpretation of the force curves. Even considering the effect of asperities,
our experimental results could be interpreted only with the aid of a partial slip model. Or else, interpreted assuming that
the viscosity close to the surfaces is different from bulk. On patterned hydrophilic surfaces, we demonstrated that the drainage
force depends not only on the overall surface roughness or micro structuring but also on the specific length scale of the
surface nanostructures. 相似文献
98.
Ana Paula Rodrigues Brasil Sebastio Tavares de Rezende Maria do Carmo Gouveia Pelúzio Valria Monteze Guimares 《Food chemistry》2010,118(2):251-255
The objectives of this work were to establish a safe and economically viable process for the removal of raffinose oligosaccharides (RO) from soy flour and compare the effects of RO elimination from diets with regard to nutritional parameters by testing in Wistar rats. Debaryomyces hansenii UFV-1 was cultivated in suspension of defatted soy flour (1:10 w/v). An increase in α-galactosidase activity was observed in the medium, with a consequent decrease in the RO concentration. A total reduction of RO was achieved at 36 h of incubation. The diet containing soy flour free of RO presented higher digestibility, 91.28%, in relation to the diet containing soy flour with RO, 87.14%. However, the removal of the oligosaccharides from the diet did not promote a significant improvement in the values of weight gain, and other nutritional parameters tested on rats, during the experimental period of 14 days. 相似文献
99.
Davis Castro dos Santos Matthew Ayorinde Adebayo Simone de Fátima Pinheiro Pereira Lizie Daniela Tentler Prola Renato Cataluña Eder Cláudio Lima Caroline Saucier Caline Rodrigues Gally Fernando Machado Machado 《Korean Journal of Chemical Engineering》2014,31(8):1470-1479
New carbon composite materials were prepared by pyrolysis of mixture of coffee wastes and red mud at 700 °C with the inorganic: organic ratios of 1.9 (CC-1.9) and 2.2 (CC-2.2). These adsorbents were used to remove reactive orange 16 (RO-16) and reactive red 120 (RR-120) textile dyes from aqueous solution. The CC-1.9 and CC-2.2 materials were characterized using Fourier transform infrared spectroscopy, Nitrogen adsorption/desorption curves, scanning electron Microscopy and X-ray diffraction. The kinetic of adsorption data was fitted by general order kinetic model. A three-parameter isotherm model, Liu isotherm model, gave the best fit of the equilibrium data (298 to 323 K). The maximum amounts of dyes removed at 323 K were 144.8 (CC-1.9) and 139.5 mg g?1 (CC-2.2) for RO-16 dye and 95.76 (CC-1.9) and 93.80 mg g?1 (CC-2.2) for RR-120 dye. Two simulated dyehouse effluents were used to investigate the application of the adsorbents for effluent treatment. 相似文献
100.
Estimation of Small Reservoir Storage Capacities with Remote Sensing in the Brazilian Savannah Region 总被引:2,自引:0,他引:2
Lineu N. Rodrigues Edson E. Sano Tammo S. Steenhuis Denílson P. Passo 《Water Resources Management》2012,26(4):873-882
Small reservoirs play an important role in supporting the local economy in the savannah areas of Brazil and are primarily
used for the provision of water for irrigation and watering livestock. Hundreds of small reservoirs have been built in the
last few decades in the Preto River Basin, but efficient water management and sound planning are hindered by inadequate knowledge
of the number, storage capacity and spatial distribution of reservoirs in the basin. The main reason for the lack of this
information is that current methodologies for quantifying the physical parameters of reservoirs are laborious, time consuming
and costly. To address this lack of data, a simple method to estimate reservoir storage volumes based on remotely sensed reservoir
surface area measured with LANDSAT was developed. The method was validated with a subset of reservoirs in the Preto River
Basin for which surface areas, shapes and depths were determined with ground-based survey measurements. The agreement between
measured and the remotely sensed reservoir volumes was satisfactory, indicating that remotely-sensed images can be used for
improved management of water in the Brazilian Savannah region. With the newly developed methods we found that the Preto River
Basin’s 147 small reservoirs can store 19 × 106 m3 of water at full capacity. 相似文献