全文获取类型
收费全文 | 106642篇 |
免费 | 9698篇 |
国内免费 | 5658篇 |
专业分类
电工技术 | 6825篇 |
技术理论 | 5篇 |
综合类 | 8197篇 |
化学工业 | 17393篇 |
金属工艺 | 6112篇 |
机械仪表 | 6628篇 |
建筑科学 | 8876篇 |
矿业工程 | 3228篇 |
能源动力 | 3215篇 |
轻工业 | 7569篇 |
水利工程 | 2051篇 |
石油天然气 | 6337篇 |
武器工业 | 880篇 |
无线电 | 12010篇 |
一般工业技术 | 12274篇 |
冶金工业 | 4581篇 |
原子能技术 | 1266篇 |
自动化技术 | 14551篇 |
出版年
2024年 | 407篇 |
2023年 | 1848篇 |
2022年 | 3090篇 |
2021年 | 4493篇 |
2020年 | 3515篇 |
2019年 | 3089篇 |
2018年 | 3265篇 |
2017年 | 3577篇 |
2016年 | 3066篇 |
2015年 | 4289篇 |
2014年 | 5390篇 |
2013年 | 6139篇 |
2012年 | 6572篇 |
2011年 | 7185篇 |
2010年 | 6452篇 |
2009年 | 6001篇 |
2008年 | 5910篇 |
2007年 | 5489篇 |
2006年 | 5510篇 |
2005年 | 4569篇 |
2004年 | 3632篇 |
2003年 | 3933篇 |
2002年 | 4788篇 |
2001年 | 4036篇 |
2000年 | 2710篇 |
1999年 | 2628篇 |
1998年 | 1929篇 |
1997年 | 1678篇 |
1996年 | 1553篇 |
1995年 | 1266篇 |
1994年 | 1021篇 |
1993年 | 723篇 |
1992年 | 625篇 |
1991年 | 381篇 |
1990年 | 320篇 |
1989年 | 244篇 |
1988年 | 185篇 |
1987年 | 108篇 |
1986年 | 96篇 |
1985年 | 68篇 |
1984年 | 52篇 |
1983年 | 38篇 |
1982年 | 39篇 |
1981年 | 25篇 |
1980年 | 28篇 |
1979年 | 12篇 |
1965年 | 2篇 |
1959年 | 6篇 |
1951年 | 4篇 |
1940年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Tian Xie Haixia Zhao Zunhang Lv Guangwen Xie Yan He 《International Journal of Hydrogen Energy》2021,46(1):581-588
This work demonstrates a facile Nb2O5-decorated electrocatalyst to prepare cost-effective Ni–Fe–P–Nb2O5/NF and compared HER & OER performance in alkaline media. The prepared electrocatalyst presented an outstanding electrocatalytic performance towards hydrogen evolution reaction, which required a quite low overpotential of 39.05 mV at the current density of ?10 mA cm?2 in 1 M KOH electrolyte. Moreover, the Ni–Fe–P–Nb2O5/NF catalyst also has excellent oxygen evolution efficiency, which needs only 322 mV to reach the current density of 50 mA cm?2. Furthermore, its electrocatalytic performance towards overall water splitting worked as both cathode and anode achieved a quite low potential of 1.56 V (10 mA cm?2). 相似文献
53.
Guangbo Zeng Dongqing Zhang Liuming Yan Baohua Yue Ting Pan Yidong Hu Shufa He Hongbin Zhao Jiujun Zhang 《International Journal of Hydrogen Energy》2021,46(39):20664-20677
Side-chain optimized poly (2,6-dimethyl-1,4-phenylene oxide)-g-poly (styrene sulfonic acid) (PPO-g-PSSA) is designed with balanced water-resistance and sulfonation degree. The PPO-g-PSSA is synthesized by controlled atom-transfer radical polymerization (ATRP) from brominated poly (2,6-dimethyl-1,4-phenylene oxide) (PPO-xBr) and ethyl styrene-4-sulfonate and followed by hydrolysis. A series of PPO-g-PSSA are prepared possessing different bromination degree (x) of PPO-xBr and polymerization degree (m) of the side-chains and the water-resistances of the fabricated membranes are investigated. The results show that a PPO-g-PSSA at relatively low x (x < 0.2) and high m (m > 4) exhibits good balance between the water-resistance and the sulfonation degree. Namely, it displays suitable proton conductivity with compromised water-resistance. Moreover, a maximum ion exchange capacity (IEC) of 3.24 mmol g?1 is reached without the sacrifice of water-resistance. In addition, PPO-g-0.08PSSA-13 and PPO-g-0.14PSSA-4 are chosen characterized by thermogravimetric analysis, proton conductivities and mechanical properties. At 90% RH, the optimized PPO-g-0.08PPSA-13 possesses a proton conductivity of 37.9 mS cm?1 at 40 °C and 45.5 mS cm?1 at 95 °C, respectively. 相似文献
54.
Baofu Qiu Xiaoming Duan Zhuo Zhang Delong Cai Ning Liao Peigang He Dechang Jia Yu Zhou 《Ceramics International》2021,47(1):73-79
The effects of La2O3–Al2O3–SiO2 addition on the thermal conductivity, coefficient of thermal expansion (CTE), Young's modulus and cyclic thermal shock resistance of hot-pressed h-BN composite ceramics were investigated. The samples were heated to 1000 °C and then quenched to room temperature with 1–50 cycles, and the residual flexural strength was used to evaluate cyclic thermal shock resistance. h-BN composite ceramics containing 10 vol% La2O3–Al2O3 and 20 vol% SiO2 addition exhibited the highest flexural strength, thermal conductivity and relatively low CTE, which were beneficial to the excellent thermal shock resistance. In addition, the viscous amorphous phase of ternary La2O3–Al2O3–SiO2 system could accommodate and relax thermal stress contributing to the high thermal shock resistance. Therefore, the residual flexural strength still maintained the value of 234.3 MPa (86.9% of initial strength) after 50 cycles of thermal shock. 相似文献
55.
Wang Zhicheng Xu Kangwei Ruan Shangshang He Chenliang Zhang Lidong Liu Fuyi 《Catalysis Letters》2022,152(9):2695-2704
Catalysis Letters - A series of mesoporous cobalt–manganese catalysts were successfully synthesized by sol–gel method as efficient catalysts for the propane oxidation. A significant... 相似文献
56.
针对平面并联机构无奇异位置工作空间求解困难、过程繁琐、计算量大等问题,提出了基于CAD求解平面并联机构工作空间的三维螺旋扫描方法。将[n]自由度平面并联机构分解成[n]条支链进行独立分析,得到每条支链下末端执行器的可达区域,再将所有支链可达区域取交集即为平面并联机构工作空间。应用SolidWorks软件建立平面并联机构模型,进行几何特征处理,通过自动求解器求解,将求解过程图形化,快速得到同轴布局5R机构和平面3-RPR并联机构的无奇异位置工作空间。通过同轴布局5R机构的运动学实验,验证了该求解方法的可行性。 相似文献
57.
58.
In this paper, we first re-examine the previous protocol of controlled quantum secure direct communication of Zhang et al.’s scheme, which was found insecure under two kinds of attacks, fake entangled particles attack and disentanglement attack. Then, by changing the party of the preparation of cluster states and using unitary operations, we present an improved protocol which can avoid these two kinds of attacks. Moreover, the protocol is proposed using the three-qubit partially entangled set of states. It is more efficient by only using three particles rather than four or even more to transmit one bit secret information. Given our using state is much easier to prepare for multiqubit states and our protocol needs less measurement resource, it makes this protocol more convenient from an applied point of view. 相似文献
59.
Basins with various mineral resources coexisting and enriching often occupy an important strategic position. The exploration of various mineral resources is repetitive at present due to unshared data and imperfect management mechanism. This situation greatly increases the cost of energy exploitation in the country. Traditional data-sharing mode has several disadvantages, such as high cost, difficulty in confirming the right of data, and lack of incentive mechanism, which make achieving real data sharing difficult. In this paper, we propose a data-sharing mechanism based on blockchain and provide implementation suggestions and technical key points. Compared with traditional data-sharing methods, the proposed data-sharing mechanism can realize data sharing, ensure data quality, and protect intellectual property. Moreover, key points in the construction are stated in the case study section to verify the feasibility of the data-sharing system based on blockchain proposed in this paper. 相似文献
60.