全文获取类型
收费全文 | 8029篇 |
免费 | 641篇 |
国内免费 | 443篇 |
专业分类
电工技术 | 163篇 |
综合类 | 436篇 |
化学工业 | 3210篇 |
金属工艺 | 797篇 |
机械仪表 | 269篇 |
建筑科学 | 198篇 |
矿业工程 | 113篇 |
能源动力 | 233篇 |
轻工业 | 447篇 |
水利工程 | 66篇 |
石油天然气 | 434篇 |
武器工业 | 43篇 |
无线电 | 520篇 |
一般工业技术 | 1016篇 |
冶金工业 | 434篇 |
原子能技术 | 255篇 |
自动化技术 | 479篇 |
出版年
2024年 | 20篇 |
2023年 | 133篇 |
2022年 | 197篇 |
2021年 | 212篇 |
2020年 | 245篇 |
2019年 | 252篇 |
2018年 | 187篇 |
2017年 | 247篇 |
2016年 | 306篇 |
2015年 | 281篇 |
2014年 | 349篇 |
2013年 | 430篇 |
2012年 | 447篇 |
2011年 | 503篇 |
2010年 | 470篇 |
2009年 | 435篇 |
2008年 | 397篇 |
2007年 | 507篇 |
2006年 | 471篇 |
2005年 | 376篇 |
2004年 | 327篇 |
2003年 | 334篇 |
2002年 | 344篇 |
2001年 | 319篇 |
2000年 | 274篇 |
1999年 | 228篇 |
1998年 | 153篇 |
1997年 | 128篇 |
1996年 | 102篇 |
1995年 | 97篇 |
1994年 | 52篇 |
1993年 | 43篇 |
1992年 | 37篇 |
1991年 | 37篇 |
1990年 | 28篇 |
1989年 | 15篇 |
1988年 | 27篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 3篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1972年 | 2篇 |
1951年 | 6篇 |
排序方式: 共有9113条查询结果,搜索用时 0 毫秒
931.
932.
Peapod‐like Li3VO4/N‐Doped Carbon Nanowires with Pseudocapacitive Properties as Advanced Materials for High‐Energy Lithium‐Ion Capacitors 下载免费PDF全文
Laifa Shen Haifeng Lv Shuangqiang Chen Peter Kopold Peter A. van Aken Xiaojun Wu Joachim Maier Yan Yu 《Advanced materials (Deerfield Beach, Fla.)》2017,29(27)
Lithium ion capacitors are new energy storage devices combining the complementary features of both electric double‐layer capacitors and lithium ion batteries. A key limitation to this technology is the kinetic imbalance between the Faradaic insertion electrode and capacitive electrode. Here, we demonstrate that the Li3VO4 with low Li‐ion insertion voltage and fast kinetics can be favorably used for lithium ion capacitors. N‐doped carbon‐encapsulated Li3VO4 nanowires are synthesized through a morphology‐inheritance route, displaying a low insertion voltage between 0.2 and 1.0 V, a high reversible capacity of ≈400 mAh g?1 at 0.1 A g?1, excellent rate capability, and long‐term cycling stability. Benefiting from the small nanoparticles, low energy diffusion barrier and highly localized charge‐transfer, the Li3VO4/N‐doped carbon nanowires exhibit a high‐rate pseudocapacitive behavior. A lithium ion capacitor device based on these Li3VO4/N‐doped carbon nanowires delivers a high energy density of 136.4 Wh kg?1 at a power density of 532 W kg?1, revealing the potential for application in high‐performance and long life energy storage devices. 相似文献
933.
Photocatalysts: Layered‐Double‐Hydroxide Nanosheets as Efficient Visible‐Light‐Driven Photocatalysts for Dinitrogen Fixation (Adv. Mater. 42/2017) 下载免费PDF全文
934.
935.
Low‐Temperature Carbide‐Mediated Growth of Bicontinuous Nitrogen‐Doped Mesoporous Graphene as an Efficient Oxygen Reduction Electrocatalyst 下载免费PDF全文
Jiuhui Han Gang Huang Zhili Wang Zhen Lu Jing Du Hamzeh Kashani Mingwei Chen 《Advanced materials (Deerfield Beach, Fla.)》2018,30(38)
Nitrogen‐doped graphene exhibits high electrocatalytic activity toward the oxygen reduction reaction (ORR), which is essential for many renewable energy technologies. To maximize the catalytic efficiency, it is desirable to have both a high concentration of robust nitrogen dopants and a large accessible surface of the graphene electrodes for rapid access of oxygen to the active sites. Here, 3D bicontinuous nitrogen‐doped mesoporous graphene synthesized by a low‐temperature carbide‐mediated graphene‐growth method is reported. The mesoporous graphene has a mesoscale pore size of ≈25 nm and large specific surface area of 1015 m2 g?1, which can effectively host and stabilize a high concentration of nitrogen dopants. Accordingly, it shows an excellent electrocatalytic activity toward the ORR with an efficient four‐electron‐dominated pathway and high durability in alkaline media. The synthesis route developed herein provides a new economic approach to synthesize bicontinuous porous graphene materials with tunable characteristic length, porosity, and chemical doping as high efficiency electrocatalysts for a wide range of electrochemical reactions. 相似文献
936.
Jin Luo Kangjun Wang Xing Hua Wang Wang Jun Li Shiming Zhang Shengli Chen 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(11)
Nitrogen (N)‐doped carbons are potential nonprecious metal catalysts to replace Pt for the oxygen reduction reaction (ORR). Pyridinic‐N‐C is believed to be the most active N group for catalyzing ORR. In this work, using zinc phthalocyanine as a precursor effectively overcomes the serious loss of pyridinic‐N, which is commonly regarded as the biggest obstacle to catalytic performance enhancement upon adopting a second pyrolysis process, for the preparation of a 3D porous N‐doped carbon framework (NDCF). The results show only ≈14% loss in pyridinic‐N proportion in the Zn‐containing sample during the second pyrolysis process. In comparison, a loss of ≈72% pyridinic‐N occurs for the non‐Zn counterpart. The high pyridinic‐N proportion, the porous carbon framework produced upon NaCl removal, and the increased mesoporous defects in the second pyrolysis process make the as‐prepared catalyst an excellent electrocatalyst for ORR, exhibiting a half‐wave potential (E1/2 = 0.88 V) up to 33 mV superior to state‐of‐the‐art Pt/C and high four‐electron selectivity (n > 3.83) in alkaline solution, which is among the best ORR activities reported for N‐doped carbon catalysts. Furthermore, only ≈18 mV degradation in E1/2 occurs after an 8000 cycles' accelerating stability test, manifesting the outstanding stability of the as‐prepared catalyst. 相似文献
937.
Jiangyue Chen Chuang Fan Xianyu Hu Chao Wang Zihan Huang Gengtao Fu Jong‐Min Lee Yawen Tang 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(28)
Tailoring composition and morphology of electrocatalysts is of great importance in improving their catalytic performance. Herein, a salt‐templated strategy is proposed to construct novel multicomponent Co/CoxMy (M = P, N) hybrids with outstanding electrocatalytic performance for the oxygen evolution reaction (OER). The obtained Co/CoxMy hybrids present porous sheet‐like architecture consisting of many hierarchical secondary building‐units. The synthetic strategy depends on a facile and effective dissolution–recrystallization–pyrolysis process under NH3 atmosphere of the precursors, which does not involve any surfactant or long‐time hydrothermal pretreatment. That is different from the conventional methods for the synthesis of hierarchical nitrides/phosphides. Benefitting from unique composition/structure‐dependent merits, the Co/CoxMy hybrids as a typical Mott–Schottky electrocatalyst exhibit good OER performance in an alkaline medium compared with their counterparts, as evidenced by a low overpotential of 334 mV at 10 mA cm?2 and a small Tafel slope of 79.2 mV dec?1, as well as superior long‐term stability. More importantly, the Co/CoxMy+Pt/C achieves higher voltaic efficiency and several times longer cycle life than conventional RuO2+Pt/C catalysts in rechargeable Zn–air batteries. It is envisioned that the present work can provide a new avenue for the development of Mott–Schottky electrocatalysts for sustainable energy storage. 相似文献
938.
Wenjuan Yang Ningjing Luo Cheng Zheng Shuping Huang Mingdeng Wei 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(51)
In the present work, a hierarchical composite of rose‐like VS2@S/N‐doped carbon (VS2@SNC) with expanded (001) planes is successfully fabricated through a facile synthetic route. Notably, the d‐spacing of (001) planes is expanded to 0.92 nm, which is proved to dramatically reduce the energy barrier for Li+ diffusion in the composite of VS2@SNC by density functional theory calculation. On the other hand, the S/N‐doped carbon in the composite greatly promotes the electrical conductivity and enhances the structural stability. In addition, the hierarchical structure of VS2@SNC facilitates rapid electrolyte diffusion and increases the contact area between the electrode and electrolyte simultaneously. Benefiting from the merits mentioned above, the VS2@SNC electrode exhibits excellent electrochemical properties, such as a large reversible capacity of 971.6 mA h g?1 at 0.2 A g?1, an extremely high rate capability of 772.1 mA h g?1 at 10 A g?1, and a remarkable cycling stability up to 600 cycles at 8 A g?1 with a capacity of 684.5 mA h g?1, making it a promising candidate as an anode material for lithium‐ion batteries. 相似文献
939.
针对陶瓷涡轮的发展,设计了一套制备陶瓷涡轮毛坯的模具。利用CAD采用双回转成形法设计涡轮模具的模块,并对模块的强度进行了分析。根据十个模块构成的模具型腔的结构和受力状态,建立了合适的力学模型,对模具型腔的侧壁厚度进行了强度校核。利用Solidworks对设计好的模具零件图进行了装配。最后。用设计好的模具在热等静压下烧结制备Si3N4陶瓷涡轮,验证了设计的模具制备陶瓷涡轮的可行性。 相似文献
940.
直流电子负载系统采用凌阳公司SPCE061A单片机为控制核心,由信号处理模块、A/D转换模块、D/A转换模块、液晶显示模块、矩阵键盘等模块组成.它能够实现恒流、恒压、恒阻和恒功率四种工作模式.其中恒压与恒流模式为基本的工作模式,而恒阻和恒功率模式是在恒流模式的基础上实现的.本系统的主要特点就是采用LM358双运算放大器和MTY25 N60E大功率场效应管构成负载的信号处理模块,这样的信号处理模块设计能够更容易获得稳定且精确的负载信号.由于SPC E061A单片机内部集成了A/D和D/A,大大简化了电路,提高了系统的可靠性. 相似文献