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   194928篇
  免费   27646篇
  国内免费   7505篇
电工技术   11268篇
技术理论   14篇
综合类   11099篇
化学工业   40334篇
金属工艺   9372篇
机械仪表   11220篇
建筑科学   15308篇
矿业工程   4252篇
能源动力   5445篇
轻工业   16868篇
水利工程   3510篇
石油天然气   8420篇
武器工业   1289篇
无线电   25675篇
一般工业技术   29319篇
冶金工业   8080篇
原子能技术   1837篇
自动化技术   26769篇
  2024年   324篇
  2023年   2530篇
  2022年   4060篇
  2021年   6552篇
  2020年   6254篇
  2019年   6884篇
  2018年   7157篇
  2017年   8106篇
  2016年   8167篇
  2015年   9796篇
  2014年   11658篇
  2013年   14384篇
  2012年   13528篇
  2011年   13685篇
  2010年   12774篇
  2009年   12270篇
  2008年   11667篇
  2007年   11026篇
  2006年   10846篇
  2005年   9330篇
  2004年   6630篇
  2003年   5937篇
  2002年   5509篇
  2001年   4806篇
  2000年   4228篇
  1999年   4053篇
  1998年   3385篇
  1997年   2734篇
  1996年   2454篇
  1995年   2070篇
  1994年   1692篇
  1993年   1193篇
  1992年   944篇
  1991年   774篇
  1990年   573篇
  1989年   510篇
  1988年   416篇
  1987年   241篇
  1986年   209篇
  1985年   136篇
  1984年   116篇
  1983年   73篇
  1982年   82篇
  1981年   65篇
  1980年   54篇
  1979年   41篇
  1978年   15篇
  1977年   34篇
  1976年   17篇
  1975年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Zhang  Junbao  Huang  Haojun  Yang  Changlin  Liu  Jizhao  Fan  Yinting  Yang  Guan 《Wireless Networks》2022,28(3):1301-1312
Wireless Networks - Although centrality is widely used to differentiate the importance of nodes for social-aware routing in mobile opportunistic networks (MONs), it is destination-agnostic since...  相似文献   
2.

This paper deals with a class of fast diffusion p-Laplace equation with logarithmic non-linearity in a bounded smooth domain with homogeneous Dirichlet boundary condition. By using energy estimates and some ordinary differential inequalities, we study the conditions on extinction and non-extinction of global solutions. The results of this paper extend and complete the previous studies on this equation.

  相似文献   
3.
4.
A double pyrovanadate CaMgV2O7 sample was synthesized via a facile solid-state route under an air atmosphere. The nonequilibrium formation pathways of the CaMgV2O7 were investigated via powder X-ray diffraction. A multistep reactions path (metavanadates–pyrovanadates–double pyrovanadate CaMgV2O7) was proposed to describe the formation of the CaMgV2O7 considering the thermodynamic and kinetic factors. The cell unit parameters of the CaMgV2O7 sample indicated the crystallization according to a monoclinic system with space group P12/c1(14), and the lattice parameters of a = 6.756 Å, b = 14.495 Å, c = 11.253 Å, β = 99.12, and V = 108.806 Å3. X-ray photoelectron spectroscopy also confirmed the +5 oxidation state vanadium in CaMgV2O7. The endothermic effects at 1033 and 1143 K were related to the incongruent melting and liquidus temperatures of CaMgV2O7, respectively. The comprehensive thermodynamic properties of CaMgV2O7 were established in both low- and high-temperature regions, utilizing a physical property measurement system and multi-high-temperature calorimetry (96 lines). The heat capacity (200 J mol K−1) and entropy (198 J mol K−1) at 298.15 K were computed based on the low-temperature heat capacity values, and the enthalpy of formation at 298.15 K was also estimated. The fitted high-temperature capacity can be used to obtain the changes in the enthalpy, entropy, and Gibbs free energy. This study is part of building a reliable thermodynamic database of the CaO–MgO–V2O5 system.  相似文献   
5.
陈尊凤  肖雄  黄伟健  吴超  王洳锦 《广东化工》2022,49(1):121-122,143
以消费者、行业专家、各品牌商以及全球各个美妆相关行业对纯净美妆的认识为依据,从配方设计、关键的原料筛选、生产过程、包材选择以及测试评估等方面,对如何实现纯净美妆产品进行了较为详细的阐述,无疑为纯净美妆的标准建立和定义提供很好的参考.  相似文献   
6.
7.
使用结构为42°Y-X LiTaO3(600 nm)/SiO2(500 nm)/Si的SOI衬底,通过抑制横向模式等优化设计,研制了单端谐振器和声表面波滤波器。经测试,谐振器的谐振频率为1.5 GHz,品质因数(Q)值高达4 000;滤波器的中心频率为1 370 MHz,插入损耗为-1.2 dB,1 dB带宽为74 MHz,相对带宽达到5.4%,阻带抑制大于40 dB,且温度系数在-55~+85 ℃时优于-9×10-6/℃。该产品具有高频、宽带、低损耗、低温漂、高阻带抑制的特点,其性能指标优异,具有很好的实用性。  相似文献   
8.
Multimedia Tools and Applications - We focus on the one-example person re-identification (Re-ID) task, where each identity has only one labeled example along with many unlabeled examples. Since...  相似文献   
9.
Novel inks were formulated by dissolving polycaprolactone (PCL), a hydrophobic polymer, in organic solvent systems; polyethylene oxide (PEO) was incorporated to extend the range of hydrophilicity of the system. Hydroxyapatite (HAp) with a weight ratio of 55–85% was added to the polymer-based solution to mimic the material composition of natural bone tissue. The direct ink writing (DIW) technique was applied to extrude the formulated inks to fabricate the predesigned tissue scaffold structures; the influence of HAp concentration was investigated. The results indicate that in comparison to other inks containing HAp (55%, 75%, and 85%w/w), the ink containing 65% w/w HAp had faster ink recovery behavior; the fabricated scaffold had a rougher surface as well as better mechanical properties and wettability. It is noted that the 65% w/w HAp concentration is similar to the inorganic composition of natural bone tissue. The elastic modulus values of PCL/PEO/HAp scaffolds were in the range of 4–12 MPa; the values were dependent on the HAp concentration. Furthermore, vancomycin as a model drug was successfully encapsulated in the PCL/PEO/HAp composite scaffold for drug release applications. This paper presents novel drug-loaded PCL/PEO/HAp inks for 3D scaffold fabrication using the DIW printing technique for potential bone scaffold applications.  相似文献   
10.
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