首页 | 官方网站   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   48481篇
  免费   4352篇
  国内免费   1965篇
工业技术   54798篇
  2024年   101篇
  2023年   856篇
  2022年   1199篇
  2021年   1897篇
  2020年   1523篇
  2019年   1285篇
  2018年   1449篇
  2017年   1610篇
  2016年   1432篇
  2015年   1999篇
  2014年   2370篇
  2013年   2889篇
  2012年   2932篇
  2011年   3306篇
  2010年   2964篇
  2009年   2822篇
  2008年   3020篇
  2007年   2519篇
  2006年   2599篇
  2005年   2286篇
  2004年   1436篇
  2003年   1349篇
  2002年   1213篇
  2001年   1081篇
  2000年   1185篇
  1999年   1410篇
  1998年   1099篇
  1997年   925篇
  1996年   828篇
  1995年   758篇
  1994年   624篇
  1993年   465篇
  1992年   352篇
  1991年   256篇
  1990年   213篇
  1989年   147篇
  1988年   131篇
  1987年   81篇
  1986年   56篇
  1985年   29篇
  1984年   25篇
  1983年   25篇
  1982年   22篇
  1981年   14篇
  1980年   11篇
  1979年   4篇
  1978年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
At present, the development and implementation of digital transformation are the keys to promoting high-quality industry development. The new digital fabrication method of robotic 3D printing is a research area being studied by many to tackle the issue of the declining productivity of traditional construction methods. Although many studies have been done, most of the current 3D printing projects are facing limitations in terms of scale. In order to bridge the gap, this article proposed a mass customization 3D printing framework system for large-scale projects. This article discusses how mass customization is made possible through the joint operation of the FUROBOT software and 3D printing hardware. By taking the east gate of Nanjing Happy Valley Plaza as a case study, the article demonstrates and studies the feasibility of the large-scale mass customization 3D printing framework system.  相似文献   
22.
Gao  Yufu  Wu  Shaohua  Li  Chuncheng  Xiao  Yaonan  Liu  Jiajian  Zhang  Bo 《Journal of Materials Science》2022,57(19):8701-8713
Journal of Materials Science - Poly(p-phenylene benzobisoxazole) (PBO) fibre-based specialty paper has become a promising candidate for high-performance insulating materials due to the remarkable...  相似文献   
23.

The effect of Co, Pd and Pt ultrathin films on the kinetics of the formation of Ni-silicide by reactive diffusion is investigated. 50 nm Ni/1 nm X/ 50 nm Ni (X?=?Co, Pd, Pt) deposited on Si(100) substrates are studied using in-situ and ex-situ measurements by X-ray diffraction (XRD). The presence of Co, Pd or Pt thin films in between the Ni layers delays the formation of the metal rich phase compared to the pure Ni/Si system and thus these films act as diffusion barriers. A simultaneous silicide formation (δ-Ni2Si and NiSi phases) different from the classic sequential formation is found during the consumption of the top Ni layer for which Ni has to diffuse through the barrier. A model for the simultaneous growth in the presence of a barrier is developed, and simulation of the kinetics measured by XRD is used to determine the permeability of the different barriers. Atom probe tomography (APT) of the Ni/Pd/Ni system shows that the Pd layer is located between the Ni top layer and δ-Ni2Si during the silicide growth, in accordance with a silicide formation controlled by Ni diffusion through the Pd layer. The effect of the barrier on the silicide formation and properties is discussed.

  相似文献   
24.
Gao  Zehai  Liu  Yang  Li  Nan  Ma  Kangjie 《Water Resources Management》2022,36(8):2685-2702
Water Resources Management - Urban river not only has the important function in urban hydrological environment, but also is an area for entertainment. Water quality assessment is the core technique...  相似文献   
25.
26.
LiCuNb3O9 has been reported newly a colossal permittivity (CP) perovskite, in which the B-site NbO6 octahedra play a bridging role in the polaron hopping. However, how the A-site modification affects the origin of the polarons and further the CP behaviours remains unexplored. To this end, A-site Ca2+ was incorporated to form Li1-xCaxCuNb3O9, and the local states, dielectric relaxations and conduction behaviours were comprehensively studied. The substitution induces the polyvalent Cu cations, i.e. Cu+/Cu2+/Cu3+. Bond valence sum calculations imply that Cu2+ and Cu3+ are underbonded, and Cu+ is overbonded, while B-site Nb5+ shows slightly different with theoretical pentavalence. All the compositions exhibit a similarly room-temperature CP response, but present two dielectric relaxations, i.e. TR1:170–300 K and TR2:260–400 K. Comprehensive investigations on universal dielectric response and bulk dc conductivity indicate that the TR1 follows the variable-range-hopping where the electron hopping between the mixed Cu+/Cu2+, while TR2 contributes from the Cu3+ nearest neighbor hopping.  相似文献   
27.
Deep-red light emitting phosphors are widely used in LEDs for indoor plant growth because of the critical role played by red light in plant growth. The luminescence properties of deep-red phosphors are still not well understood at present. An energy transfer strategy is a common and effective method to improve luminescence properties. In principle, the energy transfer process may occur when the sensitizer's emission spectra overlap with the activator's excitation spectra. In this work, Bi3+ and Mn4+ were incorporated into the matrix of Gd2MgTiO6 as sensitisers and activators, respectively. Mn4+ ions tend to occupy the [TiO6] octahedral site and the Bi3+ ions are expected to substituted in the site of Gd3+. The energy transfer process from Bi3+ to Mn4+ was realised and the photoluminescence (PL) intensity of Mn4+ increased with the doping content of Bi3+. Upon excitation at 375 nm, the PL intensity of Mn4+ increased to 116.4% when the doping concentration of Bi3+ reached 0.3%. Finally, the pc-LED devices were prepared by a Gd2MgTiO6:Bi3+, Mn4+ phosphor. The high red luminescence indicated that this phosphor has potential applications in indoor LED lighting.  相似文献   
28.
Multimedia Tools and Applications - In geometry-based point cloud compression, the geometry information is typically compressed using octree coding. In octree coding, the size of the blocks in the...  相似文献   
29.
Li  Qian  Chen  Yan  Sun  Shikun  Zhu  Muyuan  Xue  Jing  Gao  Zihan  Zhao  Jinfeng  Tang  Yihe 《Water Resources Management》2022,36(12):4799-4817
Water Resources Management - Increasing water consumption in agriculture due to global climate change has posed considerable challenges to food security, thus improving the efficiency of water...  相似文献   
30.
The over-exploitation of finite fossil resources and/or the increased environmental and sustainable awareness inspire scientists and technologists to search for inexpensive alternatives from renewable chemicals. Phenol formaldehyde (PF) resins, the oldest type of synthetic polymers with good mechanical properties and heat resistance, are widely used in the production of coatings, laminates, molding compositions, and glues. Here, biobased urushiol-derived PF resins were synthesized from the alkali-catalyzed reaction between urushiol and formaldehyde. The chemical compositions and molecular structures of resole resins were characterized by carbon-13 nuclear magnetic resonance and Fourier transform infrared spectroscopy, and their curing behaviors were studied by differential scanning calorimetry. The as-prepared urushiol-derived resole resins had methylol (Ph−CH2OH), ortho- and para-hemiformal groups (Ph−CH2OCH2OH), and the para−para/ortho−para/ortho−ortho links of methylene groups (Ph−CH2−Ph), whereas the resole resins had low curing temperatures at about 100–113°C. Additionally, given the long side alkyl group moiety on the aromatic rings of urushiol, the films of cured urushiol-derived resole resins had low glass transition temperatures of 132 ± 2°C. Furthermore, the as-prepared urushiol-derived coatings exhibited excellent physical and mechanical properties.  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-23

京公网安备 11010802026262号