全文获取类型
收费全文 | 103328篇 |
免费 | 10097篇 |
国内免费 | 5563篇 |
学科分类
工业技术 | 118988篇 |
出版年
2024年 | 230篇 |
2023年 | 1663篇 |
2022年 | 3104篇 |
2021年 | 4379篇 |
2020年 | 3360篇 |
2019年 | 2660篇 |
2018年 | 2883篇 |
2017年 | 3343篇 |
2016年 | 2911篇 |
2015年 | 4359篇 |
2014年 | 5630篇 |
2013年 | 6479篇 |
2012年 | 7669篇 |
2011年 | 8389篇 |
2010年 | 7531篇 |
2009年 | 7109篇 |
2008年 | 7091篇 |
2007年 | 6614篇 |
2006年 | 6310篇 |
2005年 | 5015篇 |
2004年 | 3568篇 |
2003年 | 3015篇 |
2002年 | 3045篇 |
2001年 | 2560篇 |
2000年 | 2126篇 |
1999年 | 1829篇 |
1998年 | 1318篇 |
1997年 | 1016篇 |
1996年 | 900篇 |
1995年 | 682篇 |
1994年 | 553篇 |
1993年 | 386篇 |
1992年 | 326篇 |
1991年 | 243篇 |
1990年 | 164篇 |
1989年 | 144篇 |
1988年 | 88篇 |
1987年 | 70篇 |
1986年 | 54篇 |
1985年 | 25篇 |
1984年 | 15篇 |
1983年 | 21篇 |
1982年 | 22篇 |
1981年 | 24篇 |
1980年 | 32篇 |
1979年 | 9篇 |
1965年 | 2篇 |
1960年 | 2篇 |
1959年 | 8篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
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
82.
针对低速大转矩切向结构永磁同步电机中磁钢尺寸对性能的影响进行研究.提出一种"工"字形排布的磁钢径向并联组合优化方案.在保证电机磁钢轴向长度和体积不变前提下,分析磁钢磁化方向长度变化对电机性能的影响.分析表明:磁钢的磁化方向长度在一定范围内增加可降低磁钢漏磁、增大反电动势和降低转矩波动;但磁钢的磁化方向长度过度增加会大大降低电机磁通面积,使得电机反电动势不增反降.在此基础上,提出一种降低磁钢漏磁、增大反电动势和降低转矩波动的三块磁钢径向并联组合的"工"字形排布方案:近气隙侧和近隔磁槽侧磁钢槽内分别插入磁化方向长度短、径向宽度窄的磁钢以降低近气隙侧和近隔磁套侧磁钢漏磁;近气隙侧磁钢和近隔磁槽侧磁钢之间采用磁化方向长度较短的磁钢以保证磁钢磁通面积降低得不多.通过仿真实验验证所提方案的可行性. 相似文献
83.
Zhezhe Yu Chunyan Qiao Xueru Zhang Lin Yan Linqiang Li Yongfeng Liu 《Journal of dairy science》2021,104(4):4108-4118
Frozen milk can help producers overcome the seasonality of goat milk production, low goat production and short lactation periods, and avoid discarding milk during some special periods. We investigated effects of combination between freezing (cryogenic refrigerator of ?16 to ?20°C or ultra-cryogenic refrigerator of ?76 to ?80°C) and thawing (homeothermy of 20 to 25°C or refrigeration of 2 to 4°C) on nutritive compositions and physicochemical characteristics of raw goat milk during storage period (80 d). Compared with fresh goat milk, the frozen-thawed milk decreased contents of fat, protein, and lactose, as well as surface tension and stability coefficient, whereas increased effective diameter and polydispersity index. The average values of color values (L*, a*, and b*) in 4 group samples changed from 83.01 to 82.25, ?1.40 to ?1.54, 3.51 to 3.81, respectively, and the ΔE of most samples did not exceed 2. In contrast to the other 3 frozen-thawed treatments, goat milk treated with ultra-cryogenic freezing-homeothermic thawing (UFHT) possessed higher fat (5.20 g/100 g), smaller effective particle diameter (0.32 µm), and the lowest polydispersity index value (0.26). The color and confocal laser scanning microscopy images of UFHT were similar to those of fresh goat milk, illustrating UFHT was the optimal approach to maintain the natural quality of goat milk. Our finding provides a theoretical basis for producers to freeze surplus milk. 相似文献
84.
85.
Zifei Yan Yubin Wang Chencan Du Jian Deng Guangsheng Luo 《American Institute of Chemical Engineers》2022,68(11):e17791
Ring-opening of epoxides with carboxylic acids has been widely used to prepare many high value intermediates in the polymer and pharmaceutical industries. Most of conventional processes proceeded in batch stirred reactors. As such they always suffer from low productivity and selectivity. Here we developed an advanced technology to perform the ring-opening reaction of epichlorohydrin with neodecanoic acid (NDA) for continuous production of 3-chloro-2-hydroxypropyl neodecanoate in a more efficient and safer way. A microreaction system where a microreactor connected to a stirred reactor was established. When the conversion of NDA rapidly reaching around 90% in a microreactor at 110°C, the reaction solution was transferred to a stirred reactor at 90°C. This two-stage operating mode can reduce the reaction time and improve the selectivity through free switching of temperature in the consecutive two reactors, thus substantially reducing the consumption of energy and materials. 相似文献
88.
89.
采用氢火焰气相色谱法(GC-FID)对凝胶洗手液中乙醇含量的测试,验证凝胶洗手液中乙醇含量检测方法的适用性,采用直接法进样,色谱柱为HP-INNOWAX毛细管色谱柱(30 m×0.25 mm,0.25μm),载气为氮气,氢火焰离子化检测器,进样口温度为230℃;检测器温度为250℃;起始温度60℃保持5 min,以40℃/min升温至230℃保持8 min.乙醇含量线性范围在5~20 mg/mL,相关系数r=0.99994,加标回收率在99.6%~101.9%之间. 相似文献
90.
Raul D. Rodriguez Sergey Shchadenko Gennadiy Murastov Anna Lipovka Maxim Fatkullin Ilia Petrov Tuan-Hoang Tran Alimzhan Khalelov Muhammad Saqib Nelson E. Villa Vladimir Bogoslovskiy Yan Wang Chang-Gang Hu Alexey Zinovyev Wenbo Sheng Jin-Ju Chen Ihsan Amin Evgeniya Sheremet 《Advanced functional materials》2021,31(17):2008818
Polyethylene terephthalate (PET) is the most widely used polymer in the world. For the first time, the laser-driven integration of aluminum nanoparticles (Al NPs) into PET to realize a laser-induced graphene/Al NPs/polymer composite, which demonstrates excellent toughness and high electrical conductivity with the formation of aluminum carbide into the polymer is shown. The conductive structures show an impressive mechanical resistance against >10000 bending cycles, projectile impact, hammering, abrasion, and structural and chemical stability when in contact with different solvents (ethanol, water, and aqueous electrolytes). Devices including thermal heaters, carbon electrodes for energy storage, electrochemical and bending sensors show this technology's practical application for ultra-robust polymer electronics. This laser-based technology can be extended to integrating other nanomaterials and create hybrid graphene-based structures with excellent properties in a wide range of flexible electronics’ applications. 相似文献