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   2287篇
  免费   86篇
  国内免费   74篇
电工技术   5篇
综合类   99篇
化学工业   207篇
金属工艺   278篇
机械仪表   66篇
建筑科学   185篇
矿业工程   40篇
能源动力   37篇
轻工业   746篇
水利工程   53篇
石油天然气   170篇
武器工业   4篇
无线电   22篇
一般工业技术   154篇
冶金工业   331篇
原子能技术   14篇
自动化技术   36篇
  2024年   9篇
  2023年   37篇
  2022年   72篇
  2021年   81篇
  2020年   98篇
  2019年   66篇
  2018年   63篇
  2017年   48篇
  2016年   54篇
  2015年   50篇
  2014年   101篇
  2013年   107篇
  2012年   160篇
  2011年   152篇
  2010年   125篇
  2009年   138篇
  2008年   86篇
  2007年   118篇
  2006年   125篇
  2005年   112篇
  2004年   118篇
  2003年   113篇
  2002年   67篇
  2001年   49篇
  2000年   44篇
  1999年   43篇
  1998年   37篇
  1997年   41篇
  1996年   28篇
  1995年   23篇
  1994年   20篇
  1993年   7篇
  1992年   8篇
  1991年   8篇
  1990年   10篇
  1989年   7篇
  1988年   4篇
  1987年   4篇
  1986年   2篇
  1985年   4篇
  1984年   1篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1979年   2篇
  1976年   1篇
排序方式: 共有2447条查询结果,搜索用时 15 毫秒
1.
At present, the proportion of tight oil in non-renewable hydrogen energy is increasing. According to an initial exploration and attemptable practice on the exploration of tight oil, it is found that the cost can be controlled effectively and positive effects are achieved. But this technique cannot make sure the proppants filled uniformly in the long fracture. Several researches on the proppants migration experiment devices and factors influencing on proppant setting are reviewed and a new set of experimental device to simulate the laws of proppants setting in long fracture is developed. This device can simulate the main factors influencing proppants setting performance. It analyzes several factors such as wall filtration, construction displacement, sand concentration, proppant size and density, viscosity of fracturing fluid is used to rank the influencing degree of every factor. Considering the effects of mutual interference between proppants, width of fracture, rough fracture surface and fracture surface filtration during the proppants setting progress, the mathematical model of proppant setting is modified by adding sand concentration correction factor, wall effect correction factor and filtration correction factor. The experimental data verify the accuracy of the settlement model is established using the data getting from experiment.  相似文献   
2.
3.
《Ceramics International》2020,46(7):9256-9262
Foam ceramics with high strength were successfully fabricated by using sand shale and steel slag as the major materials and SiC as foam agent. The influence of raw materials ratio and heat treatment temperatures on crystalline phases, porosity, mechanical properties and pore structures was investigated via XRF, XRD, SEM, DTA-TG, Micro-CT. The results indicate that the raw materials composed of 94 wt% sand shale and 6 wt% steel slag enable the fabrication of foam ceramics possessing strength of 29.98 MPa, bulk density of 0.821 g/cm3, total porosity of 67.22%, closed porosity of 55.27% and thermal conductivity of 0.08 W/(m·K). Micro-CT result shows that the pores with an average size of 267.05 μm are isolated. Pore wall thickness conforms to normal distribution, and it ranges from 18 to 42 μm. The superior property makes it promising high-strength and lightweight material in application fields, including thermal insulation materials and lightweight building materials.  相似文献   
4.
Anaerobic batch biodegradation of spent brewery grains (SBG) was investigated in the presence of co-substrates and a monoazo dye (Acid Orange 7 – AO7) under mesophilic and thermophilic regimes. The highest values for the yield coefficient of biogas (STP) on substrate (Ybs) were obtained under mesophilic conditions (0.381–0.516 Lbiogas/g CODremoved and 0.147 to 0.475 Lbiogas/g CODremoved for mesophilic and thermophilic regimes, respectively). A stimulation of the degradation of SBG associated with microbial growth was observed in the presence of co-substrates (glucose and acetate). Supplemented co-substrates also lowered the residual COD leading to an increase in the COD removal efficiency, particularly under thermophilic regime (from 41% to 70%). Although biogas yield (Ybs) indicates a decrease in the presence of the dye, suggesting that it has inhibitory effects, the overall COD removal was not significantly altered. An increase of colour removal was observed when the temperature of the operation was increased (87 ± 2% and 93 ± 1% for mesophilic and thermophilic reactors, respectively), which could be explained by both faster adsorption and biotic reductive cleavage of azo dye bond mechanisms. These results indicate that raw SBG is more prone to biodegradation under an anaerobic mesophilic regime; hence its bio-energetic valorisation is possible.  相似文献   
5.
Brewer's grains are the most important by-product of the brewery industry and it is mostly used as a protein and energy source in animal nutrition. Listeria monocytogenes is a food-borne pathogen can cause invasive diseases such as meningoencephalitis, sepsis, abortion, and gastroenteritis in humans and several animal species. The aim of this work was to study the antilisterial activity of lactic acid bacteria (LAB) isolated from brewer's grains. The incidence of Listeria spp. in brewer's grains was 3.12%. Twenty-one LAB inhibited the growth of the eight strains of L. monocytogenes. The mean inhibition halo of cell free supernatants of LAB ranged between 11.5 and 24.5 mm. The isolation of lactic acid bacteria with antilisterial activity from brewer's grains is promising based on their capacity to produce antimicrobial compounds. The production of antimicrobial metabolites by LAB in the substrate would generate an unfavorable environment for the growth of the pathogenic bacterium under study.  相似文献   
6.
Traditional kefir grains were collected from distinct parts of Turkey, and their microbial profile was determined. A wide bacterial biota was observed formed by distinct lactic acid bacteria (LAB) in which Lactococcus lactis strains appeared to be dominant. Yeast species were also identified in kefir grains. Significant levels of antifungal and antibacterial activities were monitored in kefir isolates. All tested LAB produced an exopolysaccharide (EPS) containing glucose and galactose, and some strains formed a fructan‐type EPS. Importantly, low levels of antibiotic resistance were observed among the kefir isolates.  相似文献   
7.
8.
The environmental crisis has created a demand for practices that build awareness about the interconnections of diverse forms of life, allowing humans to understand complex earthly relationships and reconnect with the land they inhabit. This paper contributes to this debate by investigating bird watching activities and their relevance for architects and landscape architects. Drawing upon multispecies studies and the notion of landscape thinking, it examines the potential of birding as a caring landscaping practice. It analyzes the relationship between birders and sand martins in two case studies and probes how birders develop attentiveness for the birds and their shared environment. The investigation suggests that birding fosters care beyond the observed species. It can trigger a landscaping practice comparable to landscape thinking that helps humans reconnect with the land, fostering response-able spatial design practices.  相似文献   
9.
For one week from August 17 to 23, 2016, three consecutive typhoons made landfall in Hokkaido for the first time on record. These typhoons and the front they stimulated brought record-breaking torrential rain over the eastern part of Hokkaido. To investigate the damage to grounds and rivers resulting from this rainfall, the Japan Society of Civil Engineers (JSCE) and the Japanese Geotechnical Society (JGS) formed a disaster research group to conduct an investigation. This report provides the results of the investigation into damage to the grounds of areas along the Tokoro River of the Okhotsk region, Hokkaido, that suffered from this tremendous and diverse disaster. Specifically, the report describes the situation of the levees which were broken and eroded by the overflowing water, the shape of the levee bodies, the levee body soil properties examined by observation of the sections, as well as the occurrence of sand boiling and air blows. The washout of road embankments as well as damage to road bridge mounting fills and abutment backfills were also investigated. The investigation has demonstrated the need to clarify the resistance of the abutment backfills and levee bodies to flowing water as well as the geotechnical predominant factors in order to clarify the mechanisms behind erosion and washout, the need to review new measures that allow for the scale of sand boiling and resultant changes in levee body stability, and the fact that the existing embankments were able to temporarily suppress the flooding water which had spilled over from the river. Furthermore, although it has been identified that the findings of a study on an embankment washout associated with a tsunami can be applied to measures taken against the overflowing water, it has also been found necessary to clarify the predominant geotechnical factors using model tests and to use a more sophisticated analytical approach to establish a geotechnical stability review as soon as possible in order to prevent the levees and embankments from being eroded and washed out due to overflowing water.  相似文献   
10.
《Soils and Foundations》2019,59(4):982-1000
This paper presents results of a series of cyclic laboratory test performed on dense to very dense silica sand. Triaxial and direct simple shear tests were performed on reconstituted sand. The test program aimed to determine the cyclic shear strength and soil deformation properties for foundation design of offshore wind turbine structures on the Dogger Bank site, offshore United Kingdom, but is also applicable for foundation design of other offshore structures and other locations. Two sand batches were used, one with clean silica sand and one with 20% silt content. Normally consolidated specimens from both batches were reconstituted to a target relative density approximately equal to 100% and 80%. On the clean sand with a target relative density of 80%, tests were also performed on specimens with an overconsolidation ratio of OCR = 4. Various contour diagrams, presenting cyclic shear strength and average and cyclic shear strains for different number of cycles, are presented. These diagrams can be used in the front-end engineering design (FEED) stage of commercial design projects on similar soil conditions, to define soil behavior when limited cyclic data is available, or in the planning stage of a cyclic laboratory test program. Effects of precycling and fines content on the cyclic behavior of triaxial and DSS specimens are discussed.  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