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   85723篇
  免费   13658篇
  国内免费   8907篇
电工技术   6696篇
技术理论   1篇
综合类   10518篇
化学工业   3723篇
金属工艺   3112篇
机械仪表   10319篇
建筑科学   5178篇
矿业工程   2755篇
能源动力   2047篇
轻工业   2336篇
水利工程   1890篇
石油天然气   3032篇
武器工业   1411篇
无线电   13508篇
一般工业技术   11876篇
冶金工业   1754篇
原子能技术   615篇
自动化技术   27517篇
  2024年   590篇
  2023年   1440篇
  2022年   2754篇
  2021年   3028篇
  2020年   3208篇
  2019年   2513篇
  2018年   2380篇
  2017年   3181篇
  2016年   3471篇
  2015年   3890篇
  2014年   5461篇
  2013年   5157篇
  2012年   6836篇
  2011年   6985篇
  2010年   5708篇
  2009年   5776篇
  2008年   5664篇
  2007年   6669篇
  2006年   5702篇
  2005年   4860篇
  2004年   3944篇
  2003年   3366篇
  2002年   2638篇
  2001年   2269篇
  2000年   1922篇
  1999年   1538篇
  1998年   1216篇
  1997年   1133篇
  1996年   900篇
  1995年   775篇
  1994年   683篇
  1993年   468篇
  1992年   435篇
  1991年   356篇
  1990年   301篇
  1989年   252篇
  1988年   191篇
  1987年   109篇
  1986年   87篇
  1985年   64篇
  1984年   77篇
  1983年   61篇
  1982年   48篇
  1981年   46篇
  1980年   27篇
  1979年   26篇
  1978年   17篇
  1977年   13篇
  1965年   6篇
  1959年   14篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
A small handful of recent studies have addressed a phenomenon known as “phantom vibration syndrome”. This refers to when phone users perceive their device to vibrate, indicating that a call or text is incoming, when in fact the phone did not vibrate at all. Though these studies show that most users do not find phantom vibration hallucinations to be very bothersome, they also find that a large majority of users experience this phenomenon. This paper explores what the striking prevalence of phantom vibration syndrome means for our contemporary relationships with technology. I begin with a review of the theories purporting to explain these data, which largely rely on particular understandings of the brain. Next I develop an alternative theory of phantom vibration syndrome based on insights from the philosophical tradition of phenomenology. This account considers the ways users develop bodily and perceptual habits regarding how the phone is understood and used. By critically contrasting these different theories, we can refine our questions about what the high prevalence of phantom vibration syndrome implies about our contemporary technological situation.  相似文献   
2.
The ensemble learning paradigm has proved to be relevant to solving most challenging industrial problems. Despite its successful application especially in the Bioinformatics, the petroleum industry has not benefited enough from the promises of this machine learning technology. The petroleum industry, with its persistent quest for high-performance predictive models, is in great need of this new learning methodology. A marginal improvement in the prediction indices of petroleum reservoir properties could have huge positive impact on the success of exploration, drilling and the overall reservoir management portfolio. Support vector machines (SVM) is one of the promising machine learning tools that have performed excellently well in most prediction problems. However, its performance is a function of the prudent choice of its tuning parameters most especially the regularization parameter, C. Reports have shown that this parameter has significant impact on the performance of SVM. Understandably, no specific value has been recommended for it. This paper proposes a stacked generalization ensemble model of SVM that incorporates different expert opinions on the optimal values of this parameter in the prediction of porosity and permeability of petroleum reservoirs using datasets from diverse geological formations. The performance of the proposed SVM ensemble was compared to that of conventional SVM technique, another SVM implemented with the bagging method, and Random Forest technique. The results showed that the proposed ensemble model, in most cases, outperformed the others with the highest correlation coefficient, and the lowest mean and absolute errors. The study indicated that there is a great potential for ensemble learning in petroleum reservoir characterization to improve the accuracy of reservoir properties predictions for more successful explorations and increased production of petroleum resources. The results also confirmed that ensemble models perform better than the conventional SVM implementation.  相似文献   
3.
A new matching cost computation method based on nonsubsampled contourlet transform (NSCT) for stereo image matching is proposed in this paper. Firstly, stereo image is decomposed into high frequency sub-band images at different scales and along different directions by NSCT. Secondly, by utilizing coefficients in high frequency domain and grayscales in RGB color space, the computation model of weighted matching cost between two pixels is designed based on the gestalt laws. Lastly, two types of experiments are carried out with standard stereopairs in the Middlebury benchmark. One of the experiments is to confirm optimum values of NSCT scale and direction parameters, and the other is to compare proposed matching cost with nine known matching costs. Experimental results show that the optimum values of scale and direction parameters are respectively 2 and 3, and the matching accuracy of the proposed matching cost is twice higher than that of traditional NCC cost.  相似文献   
4.
Cone-beam X-ray luminescence computed tomography (CB-XLCT) is an attractive hybrid imaging modality, and it has the potential of monitoring the metabolic processes of nanophosphors-based drugs in vivo. However, the XLCT imaging suffers from a severe ill-posed problem. In this work, a sparse nonconvex Lp (0?p?L1 regularization. Further, an iteratively reweighted split augmented lagrangian shrinkage algorithm (IRW_SALSA-Lp) was proposed to efficiently solve the non-convex Lp (0?p?p-values (1/16, 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 7/8) in both 3D digital mouse experiments and in vivo experiments. The results demonstrate that the proposed non-convex methods outperform L2 and L1 regularization in accurately recovering sparse targets in CB-XLCT. And among all the non-convex p-values, our Lp(1/4?p?相似文献   
5.
光荣 《西北水电》2006,(4):80-81
宁东供水工程供水水泵共有卧式和立式离心泵2种方案可供选择,也是工程论证时争论的焦点,经综合比较及主机设备的国际招标,最终确定了奥地利安德里兹公司的卧式双吸中开式离心泵为宁东供水工程的供水水泵。  相似文献   
6.
压裂是低孔、低渗油层改造的主要增产措施。根据常规测井资料、岩石物理实验分析数据及试油成果。研究储层四性关系,确定区块的低孔、低渗储层评价标准。进一步对油层进行分类,有针对性地为油层压裂提供施工层位和准确的储层参数。通过商543区块实例,阐述了选择压裂层位的方法。  相似文献   
7.
与常规的小型测试压裂不同,流体注入诊断测试(DFIT)是通过关井阶段出现的拟线性流或拟径向流阶段求取储层压力,采用改进的梅耶霍夫方法(M-method)解释储层渗透率。以长庆榆林气田一口开发井为例,依据DFIT的技术原理和测试步骤,对该井测试压降数据进行解释分析,结果可信度较高,证明了该项工艺在长庆低压低渗油气田的可行性。  相似文献   
8.
在取得土料场土料物理力学性质参数的情况下,遵循碾压试验基本原理、方法及参数组合,进行了现场碾压试验,通过试验成果的分析,得出了大坝碾压试验结论,为大坝土方填筑提供了技术依据。  相似文献   
9.
大位移井钻柱振动规律研究与应用   总被引:5,自引:0,他引:5  
在大位移井钻井工程中钻柱受着各种振动,当各种振动共振时,钻柱承受着非常大的动载,很容易受损,同时,钻柱的振动影响着井壁的稳定,严重威胁着井下的作业安全。以大位移井近井底的钻柱为研究对象,分析了钻柱振动行为所遵循的规律。采用线性分析法,获得了大位移井钻柱横向振动和扭转振动的频谱方程。同时获得了钻柱各种共振频率的分布。经分析表明:大位移井钻柱的横向振动和扭转振动的共振频率与实际钻井转速非常接近,应合理选择转速以减小钻柱共振的发生。文章的分析研究为大位移井钻柱动态行为的研究提供了理论依据。  相似文献   
10.
表面贴装工艺流程的关键工序之一就是焊膏印刷,其工艺控制的好坏直接影响着装配的线路板的质量。通过对印刷工艺参数的分析,利用试验设计的方法来找出关键工艺参数,并加以优化设定,从而为控制工序参数奠定基础。  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