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   23079篇
  免费   1945篇
  国内免费   1151篇
电工技术   1379篇
综合类   1868篇
化学工业   2452篇
金属工艺   2955篇
机械仪表   3709篇
建筑科学   1788篇
矿业工程   3048篇
能源动力   632篇
轻工业   1079篇
水利工程   2717篇
石油天然气   1378篇
武器工业   198篇
无线电   145篇
一般工业技术   1148篇
冶金工业   1027篇
原子能技术   133篇
自动化技术   519篇
  2024年   81篇
  2023年   232篇
  2022年   461篇
  2021年   670篇
  2020年   670篇
  2019年   439篇
  2018年   503篇
  2017年   600篇
  2016年   740篇
  2015年   850篇
  2014年   1372篇
  2013年   1314篇
  2012年   2085篇
  2011年   1954篇
  2010年   1393篇
  2009年   1331篇
  2008年   1109篇
  2007年   1524篇
  2006年   1472篇
  2005年   1213篇
  2004年   1028篇
  2003年   960篇
  2002年   881篇
  2001年   721篇
  2000年   602篇
  1999年   426篇
  1998年   326篇
  1997年   270篇
  1996年   235篇
  1995年   193篇
  1994年   145篇
  1993年   83篇
  1992年   90篇
  1991年   52篇
  1990年   39篇
  1989年   39篇
  1988年   23篇
  1987年   22篇
  1986年   10篇
  1985年   4篇
  1984年   2篇
  1983年   1篇
  1982年   2篇
  1980年   1篇
  1979年   3篇
  1959年   2篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
In this work, corn extruded snack products were enriched with rice bran (RB) at 10% and 15%. A co-rotating twin-screw extruder was used with a feed moisture content of 16 g 100 g−1, a screw speed of 240 r.p.m. and four heating sections of the barrel (100, 140, 150 and 150 °C). The impact of RB inclusion on nutritional profile, starch digestion, physicochemical and textural properties of snack products was evaluated. RB-enriched extrudates showed a lower specific volume and hardness and higher crispness than control. RB at 15% gave a water-holding capacity lower than control. Rheology of extrudate dispersions indicated an increase in elastic interactions and solid-like behaviour with RB supplementation. Differences in rheological properties resulted in attenuation of predictive glycaemic response for RB-enriched snacks.  相似文献   
2.
In this study, the hydraulic reactivity and cement formation of baghdadite (Ca3ZrSi2O9) was investigated. The material was synthesized by sintering a mixture of CaCO3, SiO2, and ZrO2 and then mechanically activated using a planetary mill. This leads to a decrease in particle and crystallite size and a partial amorphization of baghdadite as shown by X-ray powder diffraction (XRD) and laser diffraction measurements. Baghdadite cements were formed by the addition of water at a powder to liquid ratio of 2.0 g/ml. Maximum compressive strengths were found to be ~2 MPa after 3-day setting for a 24-h ground material. Inductively coupled plasma mass spectrometry (ICP-MS) measurements showed an incongruent dissolution profile of set cements with a preferred dissolution of calcium and only marginal release of zirconium ions. Cement formation occurs under alkaline conditions, whereas the unground raw powder leads to a pH of 11.9 during setting, while prolonged grinding increased pH values to approximately 12.3.  相似文献   
3.
Traditional West African pearl millet couscous products are popular; however, their preparation is laborious, time-consuming and energy-demanding, involving agglomeration, steaming, drying and sieving steps. In this study, a process was developed to produce millet couscous using a high pressure, high temperature and low-cost single-screw extruder. The innovation was to directly process the cooked low-moisture extrudate to a couscous product by drying and milling to the appropriate particle size (ranging between 1 and 2 mm). Throughput for the traditional process as prepared for commercial sale is 50 kg per day, but with the same amount of labour, the extrusion process yields ~350 kg per day. A consumer sensory study held in Niamey (Niger) showed that the extruded millet couscous was comparable to traditional couscous, though this was dependent on selection of the proper millet variety. This novel extrusion process could stimulate small- to medium-scale manufacturing of couscous and couscous-type products in West Africa.  相似文献   
4.
构皮滩水电站为满足2008年12月工程提前发电的需要,结合现有泄洪洞地质情况和施工情况对泄洪洞布置进行了专题研究,结果表明利用降低进口高程为550 m的泄洪洞和坝身放空底孔联合参与后期导流,可缓解2007年导流隧洞下闸封堵后大坝在2008年汛期施工的压力,为大坝施工增加了2个月左右的工期。  相似文献   
5.
水力射孔对套管强度的影响研究   总被引:4,自引:2,他引:2  
水力射孔技术是一种新型的完井方式,深穿透水力射孔技术辅助定向水力压裂可以实现油气层改造和油气井增产。但是,水力射孔套管会在孔眼处造成应力集中,使得局部应力过大而削弱了套管和水泥环的强度,可能会影响套管的使用寿命。因此,文章利用有限元软件建立了射孔套管的三维有限元模型,分析了水力射孔后套管管体的应力分布,重点研究了水力射孔参数-孔密、孔径、孔深、射孔方位角等对套管强度的影响规律。分析结果表明,沿着最大水平地应力方向深穿透水力射孔,选择合适的孔密、孔径可将射孔对套管的损害降至最小。研究结果为提高水力射孔完井设计水平提供了一定的参数依据。  相似文献   
6.
为了提高非稳定渗流计算的计算精度 ,通过数学分析得到了水位传导系数随时间变化时 ,一类非稳定渗流井流模型的半解析解 ,并进行了计算比较  相似文献   
7.
以矿用液力联轴器为研究对象 ,阐明其喷油着火的机理 ,分析其喷油着火的原因并作出事故树分析 ,针对现场使用的情况 ,提出预防措施及发展趋势 ,对矿井安全生产具有指导性作用。  相似文献   
8.
In this paper, the load-carrying capacity, power losses and stiffness of disk-type hydrostatic thrust bearings including the case of eccentric loading are discussed theoretically. The numerical analysis method is established based on a two-dimensional elastohydrostatic problem with an elastic deformation model, which is extended to adapt it for a non-axisymmetric load acting on the thrust bearing. The bearing is made of a combination of stainless steel/stainless steel and stainless steel/plastics. For the elastic materials, the maximum stiffness derived from, i.e., minimum film thickness is, larger than that of the rigid material in the range of a large ratio of pocket pressure and a hydrostatic balance ratio of over unity, which is defined as the ratio of the load to the maximum hydrostatic load-carrying capacity. The maximum load-carrying capacity and minimum power loss can exist in the domain of the hydrostatic balance ratio over unity for the case of the bearing consisting of elastic/rigid materials, in comparison with that composed of the same rigid materials. For the case of water, the power loss due to leakage flow is slightly larger but that due to frictional torque is much smaller than that in the case of hydraulic oil. Then, the total power loss is much smaller than that of hydraulic oil.  相似文献   
9.
液压伺服马达拖动和液压伺服加载 ,目前列为液压技术研究的前缘学科。本文专门从液压伺服马达进行探讨。  相似文献   
10.
飞机液压系统污染及控制   总被引:2,自引:2,他引:0  
本文全面分析了收音机液压系统污染的危害和主要原因,并在此基础上有针对性地提出了预防措施。  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