全文获取类型
收费全文 | 111175篇 |
免费 | 12391篇 |
国内免费 | 6798篇 |
专业分类
电工技术 | 8491篇 |
技术理论 | 8篇 |
综合类 | 8486篇 |
化学工业 | 16450篇 |
金属工艺 | 6404篇 |
机械仪表 | 7402篇 |
建筑科学 | 9057篇 |
矿业工程 | 3673篇 |
能源动力 | 3261篇 |
轻工业 | 7914篇 |
水利工程 | 2565篇 |
石油天然气 | 5891篇 |
武器工业 | 1287篇 |
无线电 | 14106篇 |
一般工业技术 | 11862篇 |
冶金工业 | 4462篇 |
原子能技术 | 1415篇 |
自动化技术 | 17630篇 |
出版年
2024年 | 689篇 |
2023年 | 2185篇 |
2022年 | 4359篇 |
2021年 | 6047篇 |
2020年 | 4497篇 |
2019年 | 3361篇 |
2018年 | 3832篇 |
2017年 | 4196篇 |
2016年 | 3584篇 |
2015年 | 5390篇 |
2014年 | 6786篇 |
2013年 | 7717篇 |
2012年 | 9042篇 |
2011年 | 9442篇 |
2010年 | 8415篇 |
2009年 | 7536篇 |
2008年 | 7358篇 |
2007年 | 6560篇 |
2006年 | 5815篇 |
2005年 | 4793篇 |
2004年 | 3126篇 |
2003年 | 2266篇 |
2002年 | 2100篇 |
2001年 | 1697篇 |
2000年 | 1556篇 |
1999年 | 1643篇 |
1998年 | 1174篇 |
1997年 | 962篇 |
1996年 | 886篇 |
1995年 | 741篇 |
1994年 | 604篇 |
1993年 | 406篇 |
1992年 | 339篇 |
1991年 | 271篇 |
1990年 | 191篇 |
1989年 | 148篇 |
1988年 | 134篇 |
1987年 | 78篇 |
1986年 | 69篇 |
1985年 | 46篇 |
1984年 | 42篇 |
1983年 | 31篇 |
1982年 | 34篇 |
1981年 | 33篇 |
1980年 | 44篇 |
1979年 | 28篇 |
1978年 | 14篇 |
1973年 | 12篇 |
1959年 | 17篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
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
52.
53.
Tong Le Fan Ronggui Yang Shuangchun Zhang Qiushi Pan Yi 《Chemistry and Technology of Fuels and Oils》2022,57(6):991-999
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
54.
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
55.
56.
针对领域自适应问题中源域和目标域的联合分布差异最小化问题,提出两阶段领域自适应学习方法.在第一阶段考虑样本标签和数据结构的判别信息,通过学习一个共享投影变换,使投影后的共享空间中边缘分布的差异最小.第二阶段利用源域标记数据和目标域非标记数据学习一个带结构风险的自适应分类器,不仅能最小化源域和目标域条件分布差异,还能进一步保持源域和目标域边缘分布的流形一致性.在3个基准数据集上的实验表明,文中方法在平均分类准确率和Kappa系数两项评价指标上均表现较优. 相似文献
57.
58.
Huimin Zhao Wensi Wang Yunmei Du Yu Yang Minghui Wang Shaoxiang Li Ruixin Chen Yanru Liu Lei Wang 《International Journal of Hydrogen Energy》2021,46(18):10763-10772
In this work, we synthesized Se doped MoS2@Ni3S2 with nanosheets coated nanorods structure supported on Ni foam (MoNiSeS). Firstly, MoS2@Ni3S2 (MoNiS) nanorods was synthesized by hydrothermal method. After selenization treatment, MoSe2 successfully formed on the edge of MoS2 nanosheets and particle Ni3S2 transformed into NiSe, in which MoSe2 and NiSe acted as new phase in MoNiSeS. The obtained MoNiSeS only needs a low overpotential of 68 mV to reach the current density of 10 mA cm?2, and has a low Tafel plots of 72.77 mV dec?1 and good electrochemical durability, whose electrochemical activity is much better than that of MoNiS and NiSeS, implying the introduction of Mo and Se is beneficial to improve the electrocatalytic performance of NiS for HER. In addition, the proper amount of Mo source, which has an effect on the morphology of product, has also been investigated. For MoNiSeS, the typical nanosheets coated nanarods expose more active sites and the synergic effects is good to the improvement of the catalytic activity. Meanwhile, WNiSeS has also been prepared using the same method and the corresponding results show that the electrochemical activity of WNiSeS is much better than that of NiSeS, proving the universality of this strategy. 相似文献
59.
60.
Zhuo Wang Haonan Chen Tian Wang Yujia Xiao Wenwen Nian Jiahao Fan 《Journal of the European Ceramic Society》2018,38(11):3847-3852
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