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   10971篇
  免费   2813篇
  国内免费   252篇
电工技术   97篇
综合类   884篇
化学工业   1257篇
金属工艺   653篇
机械仪表   171篇
建筑科学   1491篇
矿业工程   2216篇
能源动力   84篇
轻工业   362篇
水利工程   103篇
石油天然气   359篇
武器工业   10篇
无线电   438篇
一般工业技术   1118篇
冶金工业   4551篇
原子能技术   150篇
自动化技术   92篇
  2024年   55篇
  2023年   182篇
  2022年   325篇
  2021年   418篇
  2020年   551篇
  2019年   389篇
  2018年   441篇
  2017年   496篇
  2016年   610篇
  2015年   513篇
  2014年   718篇
  2013年   780篇
  2012年   780篇
  2011年   811篇
  2010年   607篇
  2009年   614篇
  2008年   463篇
  2007年   583篇
  2006年   476篇
  2005年   459篇
  2004年   368篇
  2003年   381篇
  2002年   330篇
  2001年   340篇
  2000年   312篇
  1999年   327篇
  1998年   272篇
  1997年   218篇
  1996年   183篇
  1995年   193篇
  1994年   190篇
  1993年   119篇
  1992年   117篇
  1991年   113篇
  1990年   93篇
  1989年   100篇
  1988年   47篇
  1987年   26篇
  1986年   14篇
  1985年   6篇
  1984年   6篇
  1983年   1篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1979年   2篇
  1978年   1篇
  1974年   1篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.
简述了黑龙江省东部中生代含煤建造类型及各自特征,并指出了今后找煤的方向。  相似文献   
992.
通过单因素试验,得到3种配方快速镍刷镀液电压与沉积速度、电极相对速度与沉积速度关系的回归方程和回归曲线,揭示了其中的规律,对机械零件的刷镀修复具有实践意义。  相似文献   
993.
994.
995.
Tool steel consumption reduction feasibility is considered in tool making by the creation of two-layered materials, obtained by deposit welding, which allow for reliability, durability and considerable increase in the high-loaded components and machinery.  相似文献   
996.
通过试验分析,得出了温度、pH、浓度与化学镍、化学金析出速率的关系,为精确控制化学镍、化学金的镀层厚度、降低化金成本提供了依据。  相似文献   
997.
In mineral exploration, the apparent resistivity and apparent frequency (or apparent polarizability) parameters of induced polarization method are commonly utilized to describe the induced polarization anomaly. When the target geology structure is significantly complicated, these parameters would fail to reflect the nature of the anomaly source, and wrong conclusions may be obtained. A wavelet approach and a metal factor method were used to comprehensively interpret the induced polarization anomaly of complex geologic bodies in the Adi Bladia mine. Db5 wavelet basis was used to conduct two-scale decomposition and reconstruction, which effectively suppress the noise interference of greenschist facies regional metamorphism and magma intrusion, making energy concentrated and boundary problem unobservable. On the basis of that, the ore-induced anomaly was effectively extracted by the metal factor method.  相似文献   
998.
Criteria or transition indicators to guide the complex decision problem of open pit to underground (OP-UG) transition are currently not well defined and documented as most mines rely on context-dependent experiences of their respective project feasibility teams. This problem is further compounded by the fact that transition indicators such as net present value (NPV), stripping ratio and commodity price are dynamic over time. Therefore, traditional deterministic approaches to solving the OP-UG transition problem cannot fully address the practicalities that mining companies face due to the variability of the transition indicators. This paper therefore reviews the OP-UG transition decision problem from a stochastic perspective. Transition indicators identified from an extensive literature review were used to benchmark four case study mines against one which had recently made the OP-UG transition, subsequently leading to the development of a generic OP-UG transition model for gold mines. The model indicates that depending on the type of deposit, gold mines can prepare to transition when the gold price to cost per ounce ratio is just greater than 2.0; grade is between 4 and 9?g/t, stripping ratio is between 3 and 15?m3/t and NPV is positive for the underground mining option.  相似文献   
999.
Fungal pretreatment of sulfides in refractory gold ores   总被引:1,自引:0,他引:1  
This study assessed the capability of the fungus, Phanerochaete chrysosporium, to decompose pyrite, arsenopyrite and a sulfide-containing flotation concentrate in an effort to develop a microbial process for pretreating refractory gold ores. The extent of biotransformation was monitored by analyzing for iron, sulfur and arsenic in incubation solutions, and for sulfide sulfur in the residual solids. The results were then expressed as percentages of the initial weights. For arsenopyrite, 1.5 wt.%, 7.2 wt.% and 10.3 wt.% of iron, arsenic and sulfur respectively were present as soluble constituents in the incubation solution within 21 days of fungal treatment, whereas for pyrite, there was 1.2 wt.% iron and 6.0 wt.% sulfur. For the same processing period in the case of the flotation concentrate, 1.8 wt.%, 6.1 wt.% and 10.7 wt.% respectively of iron, arsenic and sulfur remained in solution. Overall, the decomposition of sulfide sulfur in the samples was 15 wt.%, 35 wt.% and 57 wt.% respectively for pyrite, arsenopyrite and the flotation concentrate. Changes in sulfide sulfur concentration and the formation of oxide phases during fungal treatment were confirmed using Raman spectroscopy and X-ray diffraction analysis. These results suggest that P. chrysosporium is a potential microorganism for oxidative decomposition of metal sulfides associated with refractory gold ores.  相似文献   
1000.
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