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   32780篇
  免费   3161篇
  国内免费   1551篇
电工技术   2369篇
技术理论   1篇
综合类   2039篇
化学工业   5570篇
金属工艺   1841篇
机械仪表   2050篇
建筑科学   2570篇
矿业工程   1011篇
能源动力   884篇
轻工业   2459篇
水利工程   603篇
石油天然气   1760篇
武器工业   280篇
无线电   4037篇
一般工业技术   4161篇
冶金工业   1377篇
原子能技术   417篇
自动化技术   4063篇
  2024年   184篇
  2023年   662篇
  2022年   1301篇
  2021年   1570篇
  2020年   1216篇
  2019年   992篇
  2018年   1107篇
  2017年   1237篇
  2016年   1016篇
  2015年   1411篇
  2014年   1763篇
  2013年   1946篇
  2012年   2113篇
  2011年   2175篇
  2010年   1846篇
  2009年   1873篇
  2008年   1807篇
  2007年   1604篇
  2006年   1675篇
  2005年   1365篇
  2004年   891篇
  2003年   899篇
  2002年   841篇
  2001年   742篇
  2000年   761篇
  1999年   808篇
  1998年   647篇
  1997年   561篇
  1996年   489篇
  1995年   444篇
  1994年   329篇
  1993年   258篇
  1992年   232篇
  1991年   150篇
  1990年   134篇
  1989年   121篇
  1988年   84篇
  1987年   52篇
  1986年   31篇
  1985年   35篇
  1984年   18篇
  1983年   21篇
  1982年   23篇
  1981年   7篇
  1980年   12篇
  1979年   6篇
  1978年   6篇
  1977年   7篇
  1975年   3篇
  1951年   6篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Metallurgical and Materials Transactions A - A hot-rolled Ti–6Al–4V sheet was annealed at 960 °C (sub β-transus temperature) and then subjected to different coolings [in water...  相似文献   
102.
Metallurgical and Materials Transactions A - A cold-rolled low Al-added medium Mn steel was employed to investigate the low-temperature superplastic deformation at a relatively high initial strain...  相似文献   
103.
LD7铝合金时效工艺的研究   总被引:5,自引:3,他引:5  
通过试验系统地研究了LD7铝合金的单级和两级时效工艺。结果表明,与传统的单级时效相比,两级时效在不降低室温强度,硬度的前提下,可显著提高合金的电导率及高温性能。  相似文献   
104.
A second generation proton beam writing (PBW) system has been built at the Centre for Ion Beam Applications at the National University of Singapore for fabrication of high aspect ratio 3D nano lithographic structures. System improvements and a few lithographic structures obtained with this facility are presented in this paper. Through accurate alignment of the magnetic quadrupole lenses and the electrostatic scanning system, orthogonal beam scanning has been achieved. The earlier constrain of limited beam scan area has been overcome by adopting a combination of beam and stage scanning as well as stitching. With these improvements smallest ever Ni structure of 65 nm in width has been fabricated using nickel electroplating on a proton beam written PMMA sample in the second generation PBW facility. Using this improved PBW facility, we have also demonstrated the fabrication of fine lithographic patterns with 19 nm line width and 60 nm spacing in 100 nm thick negative high resolution hydrogen silsesquioxane resist. Future possible system improvements leading to finer resolution will be discussed briefly.  相似文献   
105.
One of the fundamental tasks of targeted marketing is to elicit associations between customers and products. Based on the results from information retrieval and utility theory, this article proposes a unified framework of targeted marketing. The customer judgments of products are formally described by preference relations and the connections of customers and products are quantitatively measured by market value functions. Two marketing strategies, known as the customer‐oriented and product‐oriented marketing strategies, are investigated. Four marketing models are introduced and examined. They represent, respectively, the relationships between a group of customers and a group of products, between a group of customers and a single product, between a single customer and a group of products, and between a single customer and a single product. Linear and bilinear market value functions are suggested and studied. The required parameters of a market value function can be estimated by exploring three types of information, namely, customer profiles, product profiles, and transaction data. Experiments on a real‐world data set are performed to demonstrate the effectiveness of the proposed framework.  相似文献   
106.

Background

Preoperatively acquired diffusion tensor image (DTI) and blood oxygen level dependent (BOLD) have been proved to be effective in providing more anatomical and functional information; however, the brain deformation induced by brain shift and tumor resection severely impairs the correspondence between the image space and the patient space in image-guided neurosurgery.

Method

To address the brain deformation, we developed a hybrid non-rigid registration method to register high-field preoperative MRI with low-field intra-operative MRI in order to recover the deformation induced by brain shift and tumor resection. The registered DTI and BOLD are fused with low-field intra-operative MRI for image-guided neurosurgery.

Results

The proposed hybrid registration method was evaluated by comparing the landmarks predicted by the hybrid registration method with the landmarks identified in the low-field intra-operative MRI for 10 patients. The prediction error of the hybrid method is 1.92 ± 0.54 mm, and the compensation accuracy is 74.3 ± 5.0%. Compared to the landmarks far from the resection region, those near the resection region demonstrated a higher compensation accuracy (P-value = .003) although these landmarks had larger initial displacements.

Conclusions

The proposed hybrid registration method is able to bring preoperatively acquired BOLD and DTI into the operating room and compensate for the deformation to augment low-field intra-operative MRI with rich anatomical and functional information.  相似文献   
107.
喷动床反应模型的研究进展   总被引:1,自引:0,他引:1  
喷动床是一种可实现热量重复循环的高效反应器 .介绍了目前喷动床研究中出现的各种反应模型 ,从等温和非等温两个方面讨论了一维轴向、流管、半分割和流动反应耦合等各类模型的基本思想和理论及各自的特点 ,并提出了进一步发展的方向 .  相似文献   
108.
石灰石在煤气化过程中的催化和固硫作用   总被引:1,自引:1,他引:1  
冯杰  同小妹 《煤炭转化》1993,16(2):31-38
基于CaO在煤气化中的催化和固硫作用,以及石灰石加热分解的性质,石灰石有可能作为煤气化过程中的催化剂和固硫剂。本文根据国内外对石灰石在煤燃烧和煤气化中作用的研究,从石灰石结构、Ca/C,Ca/S,可能的反应机理等几个方面进行了介绍和分析,并指出需进一步研究的内容。  相似文献   
109.
Sparse localized decomposition is a useful technique to extract meaningful deformation components out of a training set of mesh data. However, existing methods cannot capture large rotational motion in the given mesh dataset. In this paper we present a new decomposition technique based on deformation gradients. Given a mesh dataset, the deformation gradient field is extracted, and decomposed into two groups: rotation field and stretching field, through polar decomposition. These two groups of deformation information are further processed through the sparse localized decomposition into the desired components. These sparse localized components can be linearly combined to form a meaningful deformation gradient field, and can be used to reconstruct the mesh through a least squares optimization step. Our experiments show that the proposed method addresses the rotation problem associated with traditional deformation decomposition techniques, making it suitable to handle not only stretched deformations, but also articulated motions that involve large rotations.  相似文献   
110.
透明香皂的研制   总被引:2,自引:1,他引:2  
介绍了生产透明香皂的新配方和新工艺 ,提出了透明香皂的企业标准。新工艺用丙二醇取代传统工艺所用的乙醇做溶剂 ,生产周期大为缩短。采用速冻隧道设备 ,可方便地实现不同品种的切换 ,操作方便 ,设备投资少 ,产品综合成本低 ,具有较大的工业应用价值  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