全文获取类型
收费全文 | 31689篇 |
免费 | 2493篇 |
国内免费 | 1230篇 |
专业分类
电工技术 | 1674篇 |
技术理论 | 1篇 |
综合类 | 1935篇 |
化学工业 | 5366篇 |
金属工艺 | 1579篇 |
机械仪表 | 2110篇 |
建筑科学 | 2535篇 |
矿业工程 | 995篇 |
能源动力 | 833篇 |
轻工业 | 2003篇 |
水利工程 | 543篇 |
石油天然气 | 2040篇 |
武器工业 | 212篇 |
无线电 | 3727篇 |
一般工业技术 | 3871篇 |
冶金工业 | 1546篇 |
原子能技术 | 378篇 |
自动化技术 | 4064篇 |
出版年
2024年 | 60篇 |
2023年 | 565篇 |
2022年 | 700篇 |
2021年 | 1191篇 |
2020年 | 910篇 |
2019年 | 825篇 |
2018年 | 911篇 |
2017年 | 972篇 |
2016年 | 857篇 |
2015年 | 1150篇 |
2014年 | 1530篇 |
2013年 | 1808篇 |
2012年 | 1950篇 |
2011年 | 2041篇 |
2010年 | 1792篇 |
2009年 | 1760篇 |
2008年 | 1615篇 |
2007年 | 1636篇 |
2006年 | 1778篇 |
2005年 | 1595篇 |
2004年 | 1021篇 |
2003年 | 930篇 |
2002年 | 891篇 |
2001年 | 774篇 |
2000年 | 870篇 |
1999年 | 929篇 |
1998年 | 770篇 |
1997年 | 670篇 |
1996年 | 659篇 |
1995年 | 524篇 |
1994年 | 431篇 |
1993年 | 318篇 |
1992年 | 249篇 |
1991年 | 198篇 |
1990年 | 149篇 |
1989年 | 115篇 |
1988年 | 91篇 |
1987年 | 47篇 |
1986年 | 35篇 |
1985年 | 24篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 22篇 |
1981年 | 13篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
In Situ Electrochemical Synthesis and Deposition of Discotic Hexa‐peri‐hexabenzocoronene Molecules on Electrodes: Self‐Assembled Structure,Redox Properties,and Application for Supercapacitor 下载免费PDF全文
Leiqiang Qin Yunan Zhang Xiaoyan Wu Li Nian Zengqi Xie Linlin Liu Yuguang Ma 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(25):3028-3034
Discotic hexa‐peri‐hexabenzocoronene (HBC) molecules are synthesized by electrochemical cyclodehydrogenation reaction and in situ self‐assembled to π‐electronic, discrete nanofibular objects with an average diameter about 70 nm, which are deposited directly onto the electrode. The nanofibers consist of columnar arrays of the π‐stacked HBC molecules and the intercolumnar distance is determined to be 1.19 nm by X‐ray diffraction, which corresponds well to the distance of 1.1 nm observed by high‐resolution transmitting electron microscopy. The diameter of the molecular columns matches the size of the discotic HBC molecule indicating face‐to‐face π‐stacking of HBC units in the column. The HBC nanofibers on electrode are redox active, and the nanosized columnar structures provide a huge surface area, which is a great benefit for the charging/discharging process, delivering excellent capacitance of 155 F g?1. The described electrochemical deposition method shows great advantage for self‐assembling the family of insoluble and structurally designable graphene‐like nano materials, which constitutes an important step toward molecular electronics. 相似文献
992.
993.
红外焦平面阵列(IRFPA)的盲元既包括因材料与制造工艺的缺陷而导致的固定盲元,也包括因环境温度的漂移而出现的随机盲元.基于场景的盲元检测与补偿算法是去除这两种盲元,提高IRFPA 成像质量的有效手段.针对目前滤波类场景检测算法无法有效区分弱小点目标和随机盲元的缺陷,重点研究了随机盲元的响应特性和噪声特性,并提出了一种基于模糊中值与时域累积的盲元自适应检测与补偿算法.首先利用模糊中值滤波器从场景中提取出潜在的盲元,并通过多帧累积确定固定盲元和随机盲元的正确分布,最后对盲元进行实时补偿.实验结果证明:该算法可以有效地实现对盲元的校正,同时避免对弱小点目标的误判别. 相似文献
994.
载波相位平滑伪距的主要目的是通过高精度的载波相位测量值作为辅助量,使伪距测量值中、大随机误差得以消减。针对GPS 伪距测量中未知时变的噪声,提出基于极大后验时变噪声统计估计器的自适应衰减因子Kalman 滤波算法(AFKF),采用衰减的加权因子,使估计器逐渐忘记陈旧数据的作用,同时增加新数据的比重,避免滤波过程的发散。结合载波相位平滑伪距原理,利用AFKF 算法对全球导航卫星系统(GNSS)的国际GNSS 服务组织(IGS)的跟踪站实测数据进行仿真分析,并提出利用伪距双差值及伪距三差值来直观体现不同算法的效果比较,结果表明:与标准Kalman 滤波相比,AFKF 算法在伪距平滑应用中取得很好的效果。 相似文献
995.
996.
997.
998.
In Situ Preparation of Sandwich MoO3/C Hybrid Nanostructures for High‐Rate and Ultralong‐Life Supercapacitors 下载免费PDF全文
Hongmei Ji Xiaolin Liu Zhijuan Liu Bo Yan Lin Chen Yafeng Xie Chao Liu Wenhua Hou Gang Yang 《Advanced functional materials》2015,25(12):1886-1894
This work presents a design of sandwich MoO3/C hybrid nanostructure via calcination of the dodecylamine‐intercalated layered α‐MoO3, leading to the in situ production of the interlayered graphene layer. The sample with a high degree of graphitization of graphene layer and more interlayered void region exhibits the most outstanding energy storage performance. The obtained material is capable of delivering a high specific capacitance of 331 F g?1 at a current density of 1 A g?1 and retained 71% capacitance at 10 A g?1. In addition, nearly no discharge capacity decay between 1000 and 10 000 continuous charge–discharge cycles is observed at a high current density of 10 A g?1, indicating an excellent specific capacitance retention ability. The exceptional rate capability endows the electrode with a high energy density of 41.2 W h kg?1 and a high power density of 12.0 kW kg?1 simultaneously. The excellent performance is attributed to the sandwich hybrid nanostructure of MoO3/C with broad ion diffusion pathway, low charge‐transfer resistance, and robust structure at high current density for long‐time cycling. The present work provides an insight into the fabrication of novel electrode materials with both enhanced rate capability and cyclability for potential use in supercapacitor and other energy storage devices. 相似文献
999.
Self‐Assembling Prodrugs by Precise Programming of Molecular Structures that Contribute Distinct Stability,Pharmacokinetics, and Antitumor Efficacy 下载免费PDF全文
Hangxiang Wang Haiyang Xie Jianguo Wang Jiaping Wu Xueji Ma Lingling Li Xuyong Wei Qi Ling Penghong Song Lin Zhou Xiao Xu Shusen Zheng 《Advanced functional materials》2015,25(31):4956-4965
The availability of precisely modulated chemical modifications dramatically affects the physicochemical properties of pristine drugs and should facilitate the amphiphilic self‐assembly of prodrugs into supramolecular nanoprodrugs (SNPs). However, rationally designing such prodrugs to achieve favorable clinical outcomes still remains a challenge. Here, a library of prodrugs through site‐specific attachment of a variety of lipophilic moieties to the antitumor agent SN‐38 (7‐ethyl‐10‐hydroxycamptothecin) is constructed. Taking advantage of the role of hydroxyl groups as solvophilic moieties, these prodrugs exhibit self‐assembly in aqueous environments, allowing for the identification of five prodrugs capable of self‐assembling into SNPs at high drug concentrations. Importantly, in vivo studies demonstrate that the antitumor activity of the SNPs correlates well with their stability and long‐term circulation. In addition, the modular feature of this SNP design strategy offers the opportunity to readily incorporate additional valuable functionalities (e.g., tumor‐specific targeting ligands) to the particle surface, which is further exploited to improve antitumor efficacy in mouse xenograft models. Thus, this structure‐based reconstruction of SN‐38 molecules significantly improves the potency of SNPs for clinical use. These results also provide novel mechanistic insights into the rational design of prodrugs. 相似文献
1000.
Wei Hu Zhi Ren Junpeng Li Erin Askounis Zhixin Xie Qibing Pei 《Advanced functional materials》2015,25(30):4827-4836
Dielectric elastomers have been widely investigated for muscle‐like soft actuators and capacitive sensors. Mechanical properties play a central role in the performances of the active material. Most elastomers have specific moduli pre‐determined by the polymers' molecular structures, which are not suitable for applications in changing working conditions as natural muscles are capable of. Here new dielectric elastomers are described exhibiting variable moduli controlled via thermal treatment. The elastomers contain furan‐maleimide Diels–Alder adduct moieties to administer the crosslinking densities of the elastomeric networks via reversible Diels–Alder/retro‐Diels–Alder cycloaddition reaction, resulting in changes in the elastomers' moduli. One of the synthesized elastomers has moduli that can be controlled between 0.17 and 0.52 MPa incrementally and reversibly. Capacitive strain sensors based on this elastomer can be operated in both rigid and soft modes to achieve variable sensing response up to 30% linear strain. Actuators were fabricated and operated in both high strain mode (35% actuation area strain at 65 MV m?1) and high force output mode (0.55 MPa at 104 MV m?1). The elastomers can exhibit a range of stress–strain outputs in similar fashion as muscle. 相似文献