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   40072篇
  免费   3934篇
  国内免费   1927篇
电工技术   2489篇
技术理论   3篇
综合类   2703篇
化学工业   6582篇
金属工艺   2223篇
机械仪表   2472篇
建筑科学   2981篇
矿业工程   1132篇
能源动力   1124篇
轻工业   2646篇
水利工程   772篇
石油天然气   2491篇
武器工业   388篇
无线电   4895篇
一般工业技术   4729篇
冶金工业   1754篇
原子能技术   429篇
自动化技术   6120篇
  2024年   199篇
  2023年   800篇
  2022年   1441篇
  2021年   2069篇
  2020年   1510篇
  2019年   1141篇
  2018年   1344篇
  2017年   1397篇
  2016年   1172篇
  2015年   1671篇
  2014年   2155篇
  2013年   2437篇
  2012年   2752篇
  2011年   2967篇
  2010年   2630篇
  2009年   2204篇
  2008年   2335篇
  2007年   2103篇
  2006年   2024篇
  2005年   1762篇
  2004年   1144篇
  2003年   973篇
  2002年   930篇
  2001年   820篇
  2000年   817篇
  1999年   991篇
  1998年   761篇
  1997年   605篇
  1996年   567篇
  1995年   471篇
  1994年   393篇
  1993年   265篇
  1992年   242篇
  1991年   173篇
  1990年   128篇
  1989年   100篇
  1988年   88篇
  1987年   53篇
  1986年   47篇
  1985年   36篇
  1984年   29篇
  1983年   28篇
  1982年   23篇
  1981年   21篇
  1980年   22篇
  1979年   12篇
  1978年   12篇
  1977年   11篇
  1976年   8篇
  1973年   12篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
21.
Based on the potential therapeutic value in targeting mitochondria and the fluorophore tracing ability, a fluorescent mitochondria-targeted organic arsenical PDT-PAO-F16 was fabricated, which not only visualized the cellular distribution, but also exerted anti-cancer activity in vitro and in vivo via targeting pyruvate dehydrogenase complex (PDHC) and respiratory chain complexes in mitochondria. In details, PDT-PAO-F16 mainly accumulated into mitochondria within hours and suppressed the activity of PDHC resulting in the inhibition of ATP synthesis and thermogenesis disorder. Moreover, the suppression of respiratory chain complex I and IV accelerated the mitochondrial dysfunction leading to caspase family-dependent apoptosis. In vivo, the acute promyelocytic leukemia was greatly alleviated in the PDT-PAO-F16 treated group in APL mice model. Our results demonstrated the organic arsenical precursor with fluorescence imaging and target-anticancer efficacy is a promising anticancer drug.  相似文献   
22.
Initialization speed is one of the most important factors in network real time kinematic (NRTK) performance. Owing to the low correlation among the error s  相似文献   
23.
24.
Hexagonal barium ferries is a promising and efficient microwave (MW) absorbing material, but the low dielectric loss and poor conductivity have limited their extensive applications. In this work, a simple tactic of coating conductive polymer PANI on hexaferrite BaCo2Fe16O27 is presented, wherein the dielectric properties are customized, and more significantly, the electromagnetic loss is greatly enhanced. As displayed from structural characterizations, PANI were coated equably on the surface of hexaferrite grains by an in-situ polymerization process. The outcomes exhibit the as-prepared PANI@hexaferrite composite has remarkable electromagnetic wave absorption capacity. When the thickness is 6.0 mm, the minimal RL of ?40.4 dB was achieved at 2.9 GHz. The effective absorption bandwidth (RL < ?20 dB) of 0.65 GHz, 0.53 GHz, 0.65 GHz, 0.52 GHz, 0.46 GHz and 0.39 GHz was achieved separately when the thickness ranges from 4 to 9 mm. The highly efficient MW absorbing performance of PANI@hexaferrite composite were the consequence of multiple loss mechanisms and perfect impedance matching. It is demonstrated that the PANI@hexaferrite composite with excellent MW absorption performance is expected to be potential MW absorbers for extensive applications.  相似文献   
25.
For rechargeable wireless sensor networks, limited energy storage capacity, dynamic energy supply, low and dynamic duty cycles cause that it is unpractical to maintain a fixed routing path for packets delivery permanently from a source to destination in a distributed scenario. Therefore, before data delivery, a sensor has to update its waking schedule continuously and share them to its neighbors, which lead to high energy expenditure for reestablishing path links frequently and low efficiency of energy utilization for collecting packets. In this work, we propose the maximum data generation rate routing protocol based on data flow controlling technology. For a sensor, it does not share its waking schedule to its neighbors and cache any waking schedules of other sensors. Hence, the energy consumption for time synchronization, location information and waking schedule shared will be reduced significantly. The saving energy can be used for improving data collection rate. Simulation shows our scheme is efficient to improve packets generation rate in rechargeable wireless sensor networks.  相似文献   
26.
Chemistry and Technology of Fuels and Oils - Application of water flooding technologies in the oilfield causes intensive heterogeneity of the oil reservoir and improper circulation of the injected...  相似文献   
27.
以转基因水稻中最常用的CaMV35S启动子、NOS终止子、Cry1Ab/Ac基因、HPT基因及SPS水稻内标基因为研究对象,利用5 种不同的荧光信号(FAM、HEX、Taxas Red、Cy5、Cy5.5)进行多重实时聚合酶链式反应(real-time polymerase chain reaction,real-time PCR)检测方法的研究。通过引物组合筛选、反应体系优化、特异性测试、灵敏度测试、适用性测试等一系列实验,建立了5 重real-time PCR方法,灵敏度可达0.032%。此方法具有灵敏度高、结果准确、通量大等优点,可实现水稻中转基因成分的快速、高效检测。  相似文献   
28.
29.
The appearance of colossal permittivity materials broadened the choice of materials for energy-storage applications. In this work, colossal permittivity in ceramics of TiO2 co-doped with niobium and europium ions ((Eu0.5Nb0.5)xTi1-xO2 ceramics) was reported. A large permittivity (εr ~ 2.01?×?105) and a low dielectric loss (tanδ ~ 0.095) were observed for (Eu0.5Nb0.5)xTi1-xO2 (x?=?1%) ceramics at 1?kHz. Moreover, two significant relaxations were observed in the temperature dependence of dielectric properties for (Eu, Nb) co-doped TiO2 ceramics, which originated from defect dipoles and electron hopping, respectively. The low dielectric loss and high relative permittivity were ascribed to the electron-pinned defect-dipoles and electrons hopping. The (Eu0.5Nb0.5)xTi1-xO2 ceramic with great colossal permittivity is one of the most promising candidates for high-energy density storage applications.  相似文献   
30.
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