全文获取类型
收费全文 | 24552篇 |
免费 | 2069篇 |
国内免费 | 903篇 |
专业分类
电工技术 | 1198篇 |
技术理论 | 5篇 |
综合类 | 1363篇 |
化学工业 | 4375篇 |
金属工艺 | 1642篇 |
机械仪表 | 1494篇 |
建筑科学 | 1837篇 |
矿业工程 | 710篇 |
能源动力 | 797篇 |
轻工业 | 1615篇 |
水利工程 | 395篇 |
石油天然气 | 1721篇 |
武器工业 | 167篇 |
无线电 | 2537篇 |
一般工业技术 | 3060篇 |
冶金工业 | 1398篇 |
原子能技术 | 255篇 |
自动化技术 | 2955篇 |
出版年
2024年 | 123篇 |
2023年 | 484篇 |
2022年 | 746篇 |
2021年 | 1050篇 |
2020年 | 853篇 |
2019年 | 705篇 |
2018年 | 820篇 |
2017年 | 848篇 |
2016年 | 722篇 |
2015年 | 983篇 |
2014年 | 1173篇 |
2013年 | 1587篇 |
2012年 | 1543篇 |
2011年 | 1603篇 |
2010年 | 1410篇 |
2009年 | 1338篇 |
2008年 | 1280篇 |
2007年 | 1243篇 |
2006年 | 1319篇 |
2005年 | 1140篇 |
2004年 | 704篇 |
2003年 | 657篇 |
2002年 | 603篇 |
2001年 | 480篇 |
2000年 | 557篇 |
1999年 | 659篇 |
1998年 | 561篇 |
1997年 | 415篇 |
1996年 | 409篇 |
1995年 | 339篇 |
1994年 | 276篇 |
1993年 | 192篇 |
1992年 | 156篇 |
1991年 | 111篇 |
1990年 | 91篇 |
1989年 | 51篇 |
1988年 | 67篇 |
1987年 | 41篇 |
1986年 | 29篇 |
1985年 | 32篇 |
1984年 | 28篇 |
1983年 | 16篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 14篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1974年 | 3篇 |
1959年 | 2篇 |
1958年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Chuantao Gu Zhengkun Du Wenfei Shen Xichang Bao Shuguang Wen Dangqiang Zhu Ting Wang Ning Wang Renqiang Yang 《应用聚合物科学杂志》2015,132(8)
Three conjugated polymers, P1–P3, with dithiafulvalene (DTF) as side chains have been synthesized. All polymers have good thermal stabilities. The DTF unit could be oxidized to DTF?+ which was observed from cyclic voltammetry and ultraviolet–visible (UV–vis) spectra, and the oxidation process was independent of the conjugated backbone of the polymer. The strong π–π* transition absorbing band of the three polymers decreases gradually as increasing oxidation, and the resulting DTF?+ species give rise to an additional band at 750–1100 nm, which can be assigned to a distinguishing feature of the cation radical species. Photovoltaic device based on the blend of P2 and [6,6]‐phenyl‐C61‐butyric acid methyl ester (PC61BM) showed the power conversion efficiency of 1.05% with a fill factor of 42.8%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41508. 相似文献
992.
Discharged Energy Properties of SrO–PbO–Na2O–Nb2O5–SiO2 Glass‐Ceramics with Different Crystallization Time
下载免费PDF全文
![点击此处可从《Journal of the American Ceramic Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Qingmeng Zhang Chang Li Hongwei Liu Qun Tang Jinfeng Liu Hongtao Li Meng Wang Weiping Xie Jun Du 《Journal of the American Ceramic Society》2015,98(2):366-369
Discharged energy properties of PbO–SrO–Na2O–Nb2O5–SiO2 glass‐ceramics with crystallization time from 1 to 1000 min were investigated by measuring their hysteresis loops (described as quasi‐static measuring method) and pulse‐discharge current‐time curves (described as dynamic measuring method). The results show the same trend for both measuring methods: With the increment of crystallization time, the discharged energy density increases gradually, while the energy efficiency decreases. The highest energy efficiencies were obtained in the sample with crystallization time of 1 min, which are 96.3% and 82.4%, corresponding quasi‐static and dynamic measurement, respectively. The reduction of energy efficiency with crystallization time is attributed to combined effect of ferroelectric polarization and interfacial polarization, and part of the corresponding energy could not release in the pulse‐discharge process. 相似文献
993.
大型风力发电机偏航系统控制策略研究现状及展望 总被引:2,自引:0,他引:2
偏航系统控制策略直接决定着风力发电系统的经济效益。本文在介绍偏航系统工作原理的基础上,把风力发电机偏航系统控制策略分为重启对风策略和执行对风策略,并分别评述了研究现状。分析结果表明当前业界的研究热点主要集中于偏航系统执行对风策略方面,偏航系统重启对风策略新的研究开展较少。文中在量化分析偏航系统实际运行数据、风电场风速风向实测数据及风电机组功率曲线的基础上,指出传统的偏航系统重启对风策略存在过多将偏航系统寿命消耗在低风速区的不足,影响了偏航系统寿命周期综合经济效益;偏航系统重启对风策略制定需综合考虑风电场实际风能特征、风电机组发电功率特征等因素,研究能实现偏航系统动作寿命的高效利用的新型重启对风策略具有重要的价值,值得关注。 相似文献
994.
荧光免疫层析定量检测技术是一种正在兴起的即时检验技术。在前期荧光免疫层析定量检测仪的研究基础上,采用小波算法对A/D采样后的荧光信号进行去噪处理,选用中值滤波剔除基线漂移,最后比较了采用测试线峰值和面积作为特征量的定量检测效果。数据显示,去噪后信噪比提高10 d B,相对均方差减小30.4%;采用峰值和面积值作为定量特征量的测量CV值分别为5.1%和0.4%,测量误差分别为9.1%和0.9%。结果表明采用积分面积作为特征量对荧光信号进行定量检测具有更好的准确度和重复性。 相似文献
995.
Preparation of dual‐layer acetylated methyl cellulose hollow fiber membranes via co‐extrusion using thermally induced phase separation and non‐solvent induced phase separation methods
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hanna Jang Du‐Hyun Song Hye‐Jin Lee Seong‐Han Lim In‐Chul Kim Young‐Nam Kwon 《应用聚合物科学杂志》2015,132(43)
Dual‐layer acetylated methyl cellulose (AMC) hollow fiber membranes were prepared by coupling the thermally induced phase separation (TIPS) and non‐solvent induced phase separation (NIPS) methods through a co‐extrusion process. The TIPS layer was optimized by investigating the effects of coagulant composition on morphology and tensile strength. The solvent in the aqueous coagulation bath caused both delayed liquid–liquid demixing and decreased polymer concentration at the membrane surface, leading to porous structure. The addition of an additive (triethylene glycol, (TEG)) to the NIPS solution resolved the adhesion instability problem of the TIPS and NIPS layers, which occurred due to the different phase separation rates. The dual‐layer AMC membrane showed good mechanical strength and performance. Comparison of the fouling resistance of the AMC membranes with dual‐layer polyvinylidene fluoride (PVDF) hollow fiber membranes fabricated with the same method revealed less fouling of the AMC than the PVDF hollow fiber membrane. This study demonstrated that a dual‐layer AMC membrane with good mechanical strength, performance, and fouling resistance can be successfully fabricated by a one‐step process of TIPS and NIPS. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42715. 相似文献
996.
997.
A Self‐Charging Power Unit by Integration of a Textile Triboelectric Nanogenerator and a Flexible Lithium‐Ion Battery for Wearable Electronics
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
998.
999.
Gene Delivery: Large‐Pore Ultrasmall Mesoporous Organosilica Nanoparticles: Micelle/Precursor Co‐templating Assembly and Nuclear‐Targeted Gene Delivery (Adv. Mater. 2/2015)
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
1000.
TiO2/WO3 composite nanotubes were synthesized in an anodic aluminum oxide (AAO) template by a sol–gel method. The prepared nanotubes were characterized by transmission electron microscopy, scanning electron microscopy, powder X-ray diffraction, and Brunauer–Emmett–Teller surface area. Using the nanotubes embedded in the AAO templates as catalysts, photocatalytic degradation of methyl orange aqueous solution was carried out under UV light irradiation. The results showed that the TiO2/WO3 composite nanotubes with the thickness about 50 nm could be successfully synthesized by this method. TiO2 showed anatase phase and WO3 displayed monoclinic phase. The composite nanotubes (TiO2/WO3) exhibited higher photocatalytic activity than the pure nanotubes (WO3 or TiO2). The possible reason for improving the photocatalytic activity was also discussed. 相似文献