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   306451篇
  免费   6031篇
  国内免费   956篇
电工技术   5779篇
综合类   393篇
化学工业   47471篇
金属工艺   12192篇
机械仪表   11617篇
建筑科学   7149篇
矿业工程   1098篇
能源动力   8406篇
轻工业   26558篇
水利工程   2789篇
石油天然气   3980篇
武器工业   70篇
无线电   41995篇
一般工业技术   59929篇
冶金工业   50145篇
原子能技术   6024篇
自动化技术   27843篇
  2022年   2094篇
  2021年   3496篇
  2020年   2577篇
  2019年   3185篇
  2018年   4862篇
  2017年   4914篇
  2016年   5422篇
  2015年   3583篇
  2014年   6082篇
  2013年   14183篇
  2012年   9688篇
  2011年   12626篇
  2010年   9673篇
  2009年   10624篇
  2008年   11294篇
  2007年   10614篇
  2006年   9671篇
  2005年   8707篇
  2004年   8321篇
  2003年   8123篇
  2002年   7606篇
  2001年   7493篇
  2000年   7071篇
  1999年   7103篇
  1998年   15683篇
  1997年   11195篇
  1996年   8853篇
  1995年   6910篇
  1994年   6130篇
  1993年   5937篇
  1992年   4804篇
  1991年   4445篇
  1990年   4276篇
  1989年   3999篇
  1988年   3802篇
  1987年   3324篇
  1986年   3177篇
  1985年   3713篇
  1984年   3460篇
  1983年   3087篇
  1982年   2880篇
  1981年   2986篇
  1980年   2786篇
  1979年   2675篇
  1978年   2528篇
  1977年   2975篇
  1976年   3608篇
  1975年   2329篇
  1974年   2327篇
  1973年   2334篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
Mobile Networks and Applications - Public cloud system offers Infrastructure-as-a-Service (IaaS) to deliver the computational resources on demand. Resource requirements of a cloud environment are...  相似文献   
34.
Russian Microelectronics - The recently developed nanomaterials and their production technologies as intellectual property objects (IPOs) are considered. The role of the informational-analytical...  相似文献   
35.
Strength of Materials - Creep constitutive equations have been derived for the materials that exhibit the properties of orthotropy (transversal isotropy) and transient creep under cyclic loading. A...  相似文献   
36.
High Temperature - Experimental findings suggest that a strongly ionized, arc He plasma of atmospheric pressure does not exist in the state of the local thermodynamic equilibrium (LTE) expected for...  相似文献   
37.
38.
A technology for slag formation in the ladle–furnace unit is considered; the slag is based on the CaO–SiO2–MgO–Al2O3–B2O3 system. This technology permits both microalloying of the steel with boron (reduced from the oxide phase) and desulfurization of the steel. The resulting boron content in the steel is 0.001–0.008%; the sulfur content in low-alloy steel and pipe steel is low (0.004–0.010%); and the consumption of manganese ferroalloys is reduced to 0.5 kg/t for 08кп steel and 1.4 kg/t for 09Г2C steel. In addition, the proposed technology increases the strength of the rolled steel, without loss in its plasticity; and reduces the environmental impact thanks to the replacement of fluorspar by colemanite.  相似文献   
39.
Hypoxia formation and breakdown were tracked during 2015 in Muskegon Lake estuary at multiple locations, and five years (2011–2015) of time-series buoy observatory data were evaluated for the effect of episodic wind-events on lake mixing. Bi-weekly water temperature and dissolved oxygen (DO) profiles at four locations revealed that hypoxia occurred at all sites and persisted for 2–3 months during summer 2015. On one date in late-summer, up to 24% of the lake’s volume was estimated to be mildly hypoxic (DO < 4 mg L?1) as defined by lake sturgeon requirements. Patterns of wind speed and water column stability in late spring indicated that high winds and low stability delayed the onset of hypoxia while in late summer low winds and high stability delayed degradation of hypoxia. Wind speeds appear to play a great role in the interannual variability of stratification and subsequent hypoxia. Water temperature and DO profiles taken before and after one mid-summer mixing event (wind speed >7.7 m s?1 for 10 h), indicated that while the wind was unable to completely mix the entire water column, it deepened the epilimnion by ~1.5 m and sheared a thin layer from the upper hypolimnion. By entraining internally loaded nutrients, such episodic wind-events may initiate and sustain algal blooms in nutrient limited surface waters. Quantifying the variable role of wind and mixing events will be key to integrating limnological processes into climate models of the future.  相似文献   
40.
This work presents simulation of microstructure evolution in the nugget zone (NZ) of a AZ31-Mg-alloy friction stir weld. The process parameters (tool geometrical characteristics, rotational speed, travel speed, applied load) have been correlated with the resulting microstructural features in the NZ of the weld (grain size and population) with the aid of the MICRESS software, which provides the ability to simulate both nucleation and grain growth during dynamic recrystallization phenomena evolving in the NZ during the weld thermal cycle. The input parameters of the developed model include the tool geometry, the welding conditions as well as the recrystallization energy, the grain boundary mobility and specific material properties. NZ microstructure obtained by simulation shows good agreement with experimental measurements for both grain population and size.  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