全文获取类型
收费全文 | 85723篇 |
免费 | 13658篇 |
国内免费 | 8907篇 |
专业分类
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 |
出版年
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.
Haibo Zhang Guohua Geng Kang Li Cheng Liu Yuqing Hou 《Journal of Modern Optics》2018,65(20):2278-2289
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?1) regularization was utilized for the efficient reconstruction for early detection of small tumour in CB-XLCT imaging. Specifically, we transformed the non-convex optimization problem into an iteratively reweighted scheme based on the 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?1) model. We studied eight different non-convex 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?1/2) methods give the best performance. 相似文献
5.
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.
7.
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