全文获取类型
收费全文 | 15242篇 |
免费 | 1258篇 |
国内免费 | 645篇 |
专业分类
电工技术 | 845篇 |
技术理论 | 2篇 |
综合类 | 843篇 |
化学工业 | 2682篇 |
金属工艺 | 927篇 |
机械仪表 | 963篇 |
建筑科学 | 1128篇 |
矿业工程 | 516篇 |
能源动力 | 434篇 |
轻工业 | 932篇 |
水利工程 | 237篇 |
石油天然气 | 1190篇 |
武器工业 | 102篇 |
无线电 | 1674篇 |
一般工业技术 | 1892篇 |
冶金工业 | 836篇 |
原子能技术 | 147篇 |
自动化技术 | 1795篇 |
出版年
2024年 | 80篇 |
2023年 | 308篇 |
2022年 | 489篇 |
2021年 | 665篇 |
2020年 | 532篇 |
2019年 | 460篇 |
2018年 | 522篇 |
2017年 | 518篇 |
2016年 | 444篇 |
2015年 | 605篇 |
2014年 | 779篇 |
2013年 | 833篇 |
2012年 | 934篇 |
2011年 | 994篇 |
2010年 | 875篇 |
2009年 | 858篇 |
2008年 | 872篇 |
2007年 | 750篇 |
2006年 | 786篇 |
2005年 | 645篇 |
2004年 | 525篇 |
2003年 | 440篇 |
2002年 | 426篇 |
2001年 | 360篇 |
2000年 | 339篇 |
1999年 | 398篇 |
1998年 | 293篇 |
1997年 | 278篇 |
1996年 | 240篇 |
1995年 | 212篇 |
1994年 | 171篇 |
1993年 | 120篇 |
1992年 | 103篇 |
1991年 | 65篇 |
1990年 | 62篇 |
1989年 | 45篇 |
1988年 | 28篇 |
1987年 | 25篇 |
1986年 | 15篇 |
1985年 | 12篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
研究了羟基磷灰石(HA)和中性玻璃(G)的混合涂料在TC4多孔钛基体上的界面复合强度。探讨了中性玻璃含量、基体表面状态以及烧结工艺对这种涂层复合种植体的复合强度的影响。指出:复合的实质是中性玻璃与基体的润湿结合,最合适的玻璃含量为50 wt%,提高复合强度的关键,在于基体表面的TiN蒸镀处理,当TiN厚度为2~3 μm时,复合强度可达7.2 MPa。最佳烧结工艺为:900~950℃/30 min。 相似文献
84.
85.
Dawei Song Yanjie Shi Peng Zhang Qiang Huang Udo Kruschwitz Yuexian Hou Bo Wang 《Computational Intelligence》2015,31(4):699-720
Query language modeling based on relevance feedback has been widely applied to improve the effectiveness of information retrieval. However, intra‐query term dependencies (i.e., the dependencies between different query terms and term combinations) have not yet been sufficiently addressed in the existing approaches. This article aims to investigate this issue within a comprehensive framework, namely the Aspect Query Language Model (AM). We propose to extend the AM with a hidden Markov model (HMM) structure to incorporate the intra‐query term dependencies and learn the structure of a novel aspect HMM (AHMM) for query language modeling. In the proposed AHMM, the combinations of query terms are viewed as latent variables representing query aspects. They further form an ergodic HMM, where the dependencies between latent variables (nodes) are modeled as the transitional probabilities. The segmented chunks from the feedback documents are considered as observables of the HMM. Then the AHMM structure is optimized by the HMM, which can estimate the prior of the latent variables and the probability distribution of the observed chunks. Our extensive experiments on three large‐scale text retrieval conference (TREC) collections have shown that our method not only significantly outperforms a number of strong baselines in terms of both effectiveness and robustness but also achieves better results than the AM and another state‐of‐the‐art approach, namely the latent concept expansion model. © 2014 Wiley Periodicals, Inc. 相似文献
86.
为提高基于EOG的眼动信号分类算法精度,改进基于EOG的人—机交互系统性能,提出了一种基于曲线拟合(curve fitting)与支持向量机(SVM)的眼动信号分类算法(CF-SVM),并设计了新的实验范式,增加了“扫视保持”环节.该算法采用曲线拟合方法进行特征提取,在此基础上,使用SVM分类器对眼动信号进行分类.实验室环境下,对9名眼部活动正常的受试者进行了眼动数据采集与识别,CF-SVM算法的平均分类准确率达到98.3%,与其他几种眼动识别方法相比较,其平均正确率分别提升了9.4%、5.9%、1.0%.实验结果表明,CF-SVM算法在眼动信号识别中表现了良好的性能,具有高的分类精度和鲁棒性. 相似文献
87.
88.
Cheng Zhang Chunping Hou Xiaoyan Wang Zhiyuan Wang 《Multimedia Tools and Applications》2016,75(12):6945-6962
In this paper, based on the proposed basic implementation of circular projection, a multi-camera setup which can be used for panoramic stereo imaging is presented. Firstly, we get multiple stereo pairs instantly by fixing multiple cameras on the proposed setup, which is an approximate implementation of circular projection. We then prove that the influence on the resultant stereo pairs generated by this approximate setup is slight based on similar triangles and structural similarity (SSIM). With these stereo pairs, the automatic panoramic image stitching algorithm is applied to generate panoramas for both eyes. In addition, with reasonable distance between cameras and the scene, physical dimensions of this setup are given. Finally, experimental results demonstrate that our scheme can be used to generate cylindrical stereo panoramic image with proper scene depth, which can provide viewers with distinguishing stereoscopic experience. The device can be installed on the mobile equipment and captures panoramic stereo image in a moment without stopping. In the future, the proposed setup can be used in the field of network navigation, video monitor and virtual reality. 相似文献
89.
In this paper, a nonlinear entanglement witness criterion based on continuous-variable local orthogonal observables for bipartite states is established, which is strictly stronger than the the linear entanglement witnesses criterion introduced by Zhang et al. (Phys. Rev. Lett. 111:190501, 2013). This criterion is particularly applied to two-mode Gaussian states yielding a criterion in terms of the covariance matrix. Comparison with CCNR criterion is discussed. 相似文献
90.
Wenchao?Xu Zining?Hou Zhenhua?Liu Zhigang?WuEmail author 《Microfluidics and nanofluidics》2016,20(9):128
We developed a new approach for particle separation by introducing viscosity difference of the sheath flows to form an asymmetric focusing of sample particle flow. This approach relies on the high-velocity gradient in the asymmetric focusing of the particle flow to generate a lift force, which plays a dominated role in the particle separation. The larger particles migrate away from the original streamline to the side of the higher relative velocity, while the smaller particles remain close to the streamline. Under high-viscosity (glycerol–water solution) and low-viscosity (PBS) sheath flows, a significant large stroke separation between the smaller (1.0 μm) and larger (9.9 μm) particles was achieved in a sample microfluidic device. We demonstrate that the flow rate and the viscosity difference of the sheath flows have an impact on the interval distance of the particle separation that affects the collected purity and on the focusing distribution of the smaller particles that affects the collected concentration. The interval distance of 293 μm (relative to the channel width: 0.281) and the focusing distribution of 112 μm (relative to the channel width: 0.107) were obtained in the 1042-μm-width separation area of the device. This separation method proposed in our work can potentially be applied to biological and medical applications due to the wide interval distance and the narrow focusing distribution of the particle separation, by easy manufacturing in a simple device. 相似文献