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   3909篇
  免费   58篇
  国内免费   75篇
电工技术   21篇
综合类   102篇
化学工业   1651篇
金属工艺   239篇
机械仪表   179篇
建筑科学   197篇
矿业工程   19篇
能源动力   112篇
轻工业   310篇
水利工程   6篇
石油天然气   19篇
武器工业   3篇
无线电   102篇
一般工业技术   890篇
冶金工业   84篇
原子能技术   36篇
自动化技术   72篇
  2023年   46篇
  2022年   77篇
  2021年   78篇
  2020年   76篇
  2019年   75篇
  2018年   88篇
  2017年   102篇
  2016年   112篇
  2015年   150篇
  2014年   170篇
  2013年   343篇
  2012年   186篇
  2011年   279篇
  2010年   197篇
  2009年   206篇
  2008年   185篇
  2007年   177篇
  2006年   156篇
  2005年   144篇
  2004年   134篇
  2003年   136篇
  2002年   121篇
  2001年   93篇
  2000年   74篇
  1999年   90篇
  1998年   93篇
  1997年   77篇
  1996年   68篇
  1995年   60篇
  1994年   49篇
  1993年   48篇
  1992年   35篇
  1991年   21篇
  1990年   21篇
  1989年   16篇
  1988年   12篇
  1987年   6篇
  1986年   6篇
  1985年   11篇
  1984年   8篇
  1983年   6篇
  1982年   4篇
  1981年   2篇
  1980年   2篇
  1977年   1篇
  1976年   1篇
排序方式: 共有4042条查询结果,搜索用时 15 毫秒
41.
我国在商、周之交,就开始了早期的中西交流,而张骞西行后又开辟了新的中外来往的交通路线。我国的玻璃业尽管没能发展为重要的手工业门类,但它始终在持续而缓慢的发展,更重要的是,正是由于玻璃业的非主流,在发展过程中凸显了外部因素的重要性。丝绸之路在中国古代玻璃艺术的发展过程中起到了重要作用。  相似文献   
42.
A hybrid model incorporating wavelet and radial basis function neural network is presented which is used to detect, identify and characterize the acoustic signals due to surface discharge activity and hence differentiate abnormal operating conditions from the normal ones. The tests were carried out on cleaned and polluted high voltage glass insulators by using surface tracking and erosion test procedure of international electrotechnical commission 60587. A laboratory experiment was conducted by preparing the prototypes of the discharges. This study suggests a feature extraction and classification algorithm for surface discharge classification, which when combined together reduced the dimensionality of the feature space to a manageable dimension, by “marrying” the wavelet to radial basis function neural network very high levels of classification are achieved. Wavelet signal treatment toolbox is used to recover the surface discharge acoustic signals by eliminating the noisy portion and to reduce the dimension of the feature input vector. A radial basis function neural network classifier was used to classify the surface discharge and assess the suitability of this feature vector in classification. This learning method is proved to be effective by applying the wavelet radial basis function neural network in the classification of surface discharge fault data set. The test results show that the proposed approach is efficient and reliable.  相似文献   
43.
微合金化蠕墨铸铁玻璃模具材质的研究   总被引:3,自引:0,他引:3  
介绍了微合金化蠕墨铸铁玻璃模具材质的组织、力学性能及热物性,探讨了影响其性能的诸多因素。结果表明:这种材质具有较高的综合性能指标,具有良好的使用性能和显著的经济价值和社会效益。不仅适于与玻璃模具,还可广泛地应用于冶金、塑料和橡胶行业。  相似文献   
44.
The effects of suspended fibre on macroscale and microscale mixing in a small stirred tank reactor were studied under batch conditions using the competitive, consecutive azo coupling between 1-naphthol and diazotized sulfanilic acid. The mixing quality was determined from the distribution between the mono and bis substituted reaction products. Nylon (2 and 3 millimeters in length) and fully bleached softwood kraft pulp (FBK) fibre suspensions were examined at volumetric concentrations up to the limit that complete suspension motion could be maintained in the vessel at impellet rotational speeds of 7 and 10s-1. The adsorption of the product dyes on the fibre was found to be proportional or very nearly proportional to their concentrations in the aqueous phase and did not interfere with the assessment of mixing in the suspension.

Suspended fibres were found to slightly increase the 'critical feed time' of the diazotized sulfanilic acid, corresponding to an increase in the macromixing or bulk blend lime of the vessel. Continued increase in the fibre concentration led to the formation of a well mixed cavern centered on the impeller and the creation of stagnant regions adjacent to the vessel walls. The departure from the Newtonian fibre-free case is due to changes in the flow through and distribution of the energy dissipative regions in the vessel. The most effective location for chemical addition to ensure good microscale mixing remains in the impeller vicinity.  相似文献   
45.
我厂总结加料实际运行情况,分析加料口对配合料熔化作业的影响,在仍采用一台(嘴宽为800mm)毯式推料加料机情况下,对24m~2的马蹄焰熔炉加料口结构进行了改进,取得了较好的效果。  相似文献   
46.
空心玻璃微珠复合聚氨酯泡沫的模塑成型收缩率   总被引:1,自引:1,他引:1  
研究了用空心玻璃微珠复合聚氨酯泡沫塑料制成厚度不同、形状不同、结构不同的制品时模型成型的收缩率,以及在模塑成型过程中,熟化温度、熟化时间和熟化后在模具内保持的时间对模塑成型收缩率的影响。结果表明,制品模塑成型收缩率随着厚度的增加而增大;加入金属嵌件后可较大程度地限制制品收缩;当熟化温度高于100℃时,随着熟化温度的升高,制品收缩率增大。  相似文献   
47.
玻璃器皿压机夹模机构的分析与研究   总被引:1,自引:0,他引:1  
曾孝宇  李茂延  傅旻 《玻璃与搪瓷》2002,30(5):35-37,25
对夹模机构的两种结构型式-杠杆式夹模机构和连杆式夹模机构的结构、工作原理及受力情况进行了分析和研究.  相似文献   
48.
熔制玻璃用坩埚抗热震性的改进   总被引:1,自引:0,他引:1  
王志发 《耐火材料》2002,36(3):163-164
在粘土 -蜡石质玻璃用坩埚的配方基础上 ,研究了蜡石的粒径和加入量的变化对试样抗热震性的影响。结果发现 :减小蜡石的粒径与加入量均可提高试样的抗热震性 ,但减小蜡石粒径对提高试样的抗热震性更有效 ;在配料中引入少量的蓝晶石细粉 ,可明显提高试样的抗热震性。  相似文献   
49.
The electrochemical insertion of sodium ions into different types of hard carbons was achieved in electrolytes composed of ethylene carbonate as the solvent and NaClO4 as the salt. For all the materials studied the sodium uptake increases when the carbon highest heat treatment temperature (HTT) decreases. PAN-based carbon fibres appear to be suitable structures to allow significant sodium insertion. Thus, T650 ex-PAN fibres lead to a reversible capacity close to 209 mAh g−1. In that case, sodium insertion occurs in two main ways: one is the adsorption on the single graphene layers and the other is the concomitant insertion into the porosity that occurs below 0.1 V versus Na+/Na. This second mechanism, which is indicated by a low-voltage plateau on the electrochemical curves, allows significant insertion. The compared electrochemical study of two saccharose-coke samples corresponding to different regions of Dahn's classification underlines the importance of the carbon precursor and of the manufacture process. The reversible capacity is equal to 184 mAh g−1 for the sample heat treated at 800 °C which presents a high hydrogen content whereas it is close to 145 mAh g−1 for the one characterized by a HTT of about 1500 °C and a low hydrogen content. The best electrochemical performances are obtained for pyrolyzed cellulose carbons. Indeed, the reversible capacity is about 279 mAh g−1. Outgassing these carbons at 950 °C results in such a decrease of the reversible capacity down to 145 mAh g−1. That can be related either to the thermal elimination of heteroelements or to modifications of the pore size distribution. Consequently, the most suitable hard carbon material for anodic applications in rechargeable sodium-ion batteries should both present a high residual hydrogen content and a significant microporosity.  相似文献   
50.
对水平钢化炉内传动辊的温度场进行了数值模拟。在研究玻璃加热过程时,传动辊释放出的辐射热是个非常重要的因素,其大小与传动辊的温度有关,影响着钢化玻璃的质量。传动辊温度随加热时间而改变,在计算玻璃板温度时,必须与传动辊的温度场耦合求解。  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