全文获取类型
收费全文 | 23127篇 |
免费 | 2383篇 |
国内免费 | 1265篇 |
专业分类
电工技术 | 451篇 |
技术理论 | 1篇 |
综合类 | 316篇 |
化学工业 | 5513篇 |
金属工艺 | 1487篇 |
机械仪表 | 1653篇 |
建筑科学 | 700篇 |
矿业工程 | 157篇 |
能源动力 | 2524篇 |
轻工业 | 1259篇 |
水利工程 | 197篇 |
石油天然气 | 200篇 |
武器工业 | 7篇 |
无线电 | 2658篇 |
一般工业技术 | 4999篇 |
冶金工业 | 575篇 |
原子能技术 | 196篇 |
自动化技术 | 3882篇 |
出版年
2024年 | 165篇 |
2023年 | 1360篇 |
2022年 | 1171篇 |
2021年 | 1294篇 |
2020年 | 1623篇 |
2019年 | 1373篇 |
2018年 | 881篇 |
2017年 | 1464篇 |
2016年 | 1572篇 |
2015年 | 1651篇 |
2014年 | 1700篇 |
2013年 | 1549篇 |
2012年 | 1573篇 |
2011年 | 1309篇 |
2010年 | 1009篇 |
2009年 | 1173篇 |
2008年 | 538篇 |
2007年 | 839篇 |
2006年 | 912篇 |
2005年 | 462篇 |
2004年 | 226篇 |
2003年 | 282篇 |
2002年 | 294篇 |
2001年 | 310篇 |
2000年 | 197篇 |
1999年 | 237篇 |
1998年 | 106篇 |
1997年 | 54篇 |
1996年 | 85篇 |
1995年 | 77篇 |
1994年 | 61篇 |
1993年 | 60篇 |
1992年 | 64篇 |
1991年 | 55篇 |
1990年 | 76篇 |
1989年 | 70篇 |
1988年 | 119篇 |
1987年 | 264篇 |
1986年 | 223篇 |
1985年 | 57篇 |
1984年 | 41篇 |
1983年 | 31篇 |
1982年 | 22篇 |
1981年 | 40篇 |
1980年 | 25篇 |
1979年 | 34篇 |
1978年 | 16篇 |
1977年 | 9篇 |
1976年 | 14篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
为了提高建筑类高校学生的实际工作能力,提出情景模拟的实践教学方法,并以建筑环境与能源应用工程专业为例,制订了三条执行路线。采用情景模拟教学法指导本科生进行毕业设计,可以使毕业设计组内学生相互配合,培养工作能力和沟通能力,并使学生了解行业信息。 相似文献
992.
通过测试装置测定出测试孔输入功率、环路平均温度,采用线热源模型对现场测试数据进行推导分析,计算出测试孔岩土导热系数,该数值对在当地以及周边地区进行土壤源热泵系统设计具有重要的参考价值。 相似文献
993.
A ternary nanocomposite consisting of poly(L-lactic acid) (PLLA), poly(D-lactic acid) (PDLA), and epoxy cyclohexyl polyhedral oligomeric silsesquioxane (e-POSS) was prepared by reactive blending method. Scanning electron microscopy revealed that the feeding of three compositions in batches, i.e., PDLA incorporation at different times, was more beneficial for the even dispersion of POSS in matrix. POSS introduction improved the homocrystallinity and stereocomplex of the blends. Rheological properties and heat resistance were enhanced, which indicated potential extensive application of PLLA-based materials. The optimization of degradation stability in saline buffer was attributed to the various hydrophobic properties of blends caused by POSS structure. 相似文献
994.
《Ceramics International》2016,42(15):17137-17147
The properties of ceramic matrix composites strongly depend upon their complex internal structures. To better understand and improve the properties of the silicon carbide fiber-reinforced silicon carbide matrix composites (SiCf/SiC), we explored the microstructural properties of composites reinforced with either two-dimensional (2D) woven or three-dimensional (3D) braided preforms using synchrotron X-ray computed microtomography. Transects and volumetric images of the composites were reconstructed from objection images and the microstructures were investigated in three spatial directions. The network of void space in a composites was visualized in 3D and quantitative analysis of the porosity was performed to characterize the fiber-tissue structures. 2D-woven SiCf/SiC composite exhibited important fluctuations of porosity in different directions and the stacking of plies had a significant effect on the porosity distribution. In contrast, 3D-braided SiCf/SiC composites showed much less variation of porosity. We found the degree of densification of the composite also influenced the porosity distribution. 相似文献
995.
Huihui Zhang Rong Wang Gesheng Yang Yuanyuan Xu Huili Shao 《Polymer Engineering and Science》2016,56(4):373-379
The UV‐excitable fluorescent poly(lactic acid) (PLA) fibers were spun by the traditional melt spinning process, and the effects of the fluorescent powder content (w(FP)) and draw ratio (DR) on the structure and properties of the fluorescent PLA fibers were investigated, respectively. The results showed that the emission spectra of fluorescent PLA fibers were peaked at 530 nm after UV excitation, indicating the PLA fibers would emit green light under UV light. With the increasing of w(FP), the relative fluorescence intensity of PLA fibers increased gradually, whereas more and larger protrusions were formed on the fiber surface due to the agglomeration of fluorescent powder, both the crystallinity and mechanical properties of fluorescent PLA fiber showed the decreasing trend with the increase of w(FP). With the increase of DR, the tensile strength of fluorescent PLA fibers increased gradually, whereas the relative fluorescence intensity of PLA fibers increased firstly and then decreased, and the highest fluorescence intensity was obtained when the DR was 3.6. In addition, the confocal laser scanning microscope can be used well to simulate the 3D distribution of fluorescent powder among the PLA fibers. POLYM. ENG. SCI., 56:373–379, 2016. © 2016 Society of Plastics Engineers 相似文献
996.
High flux nanofibrous composite microfiltration membrane prepared by melt blending extrusion: Application in liquid filtration
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)
High flux PP/EVOH nanofibrous composite microfiltration membrane (P/E‐NCMM) based on polypropylene (PP) (575 nm) and polyethylene‐co‐polyvinyl alcohol (EVOH) nanofibers (248 nm) with low operation pressure for liquid filtration was fabricated by melt blending extrusion. PP nanofibers as the scaffold played a supporting role, and EVOH nanofibers filled in the PP nanofibers network structure narrowed the pore size and improved the wettability. Taking advantages of PP and EVOH nanofibers, the nanofibrous composite membrane created fascinating features for liquid filtration. The experimental results showed that the P/E‐NCMM had high average pure water flux at low operating pressure. The P/E‐NCMM with 30 wt % PP nanofibers showed high water flux [450.9 L/(m2 h)] even at very low feeding pressure (0.05 MPa) with above 95% retention for TiO2 suspension. The results indicated that the P/E‐NCMM prepared by this method had great potential for the application in liquid filtration. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43585. 相似文献
997.
Polyether‐based main‐chain‐type polytriazole elastomer with benzoxazine via a 1,3‐dipolar cycloaddition reaction
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)
A novel functional polyether‐based elastomer with a benzoxazine structure in its main chain was successfully synthesized via a 1,3‐dipolar cycloaddition reaction. Benefitting from a facile one‐pot synthesis strategy, the elastomer was prepared at low temperature (80°C) and was characterized clearly afterward. The azide‐terminated polyether and acetylene‐terminated benzoxazine were used as the soft and hard segments, respectively, in the polymer chain. Because the triazole rings served as stable linkage between the soft and hard segments, the elastomer possessed good thermal stability (the 5% weight loss temperature could exceed 350°C) compared to traditional elastomers, such as polyurethane. The rigid benzoxazine rings provided the product with good mechanical properties (the tensile strength of the elastomer could exceed 30 MPa). Furthermore, the ring‐opening polymerization of oxazine rings in the structure gifted the elastomer with possibility of thermally induced structural transformation. The thermally induced structural transformation could conveniently realize the conversion of the elastomer to a thermosetting resin. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42820. 相似文献
998.
Ag/g-C3N4 photocatalysts were synthesized by a rapid microwave-assisted polyol process. The characterization results showed monodisperse Ag nanoparticles with diameters of a few nanometers closely attached to the edges of g-C3N4. The presence of Ag nanoparticles in Ag/g-C3N4 photocatalysts enhanced the visible-light absorption and suppressed the recombination of photogenerated electron/hole pairs. The Ag/g-C3N4 photocatalysts exhibited the superior visible-light responsive photocatalytic activity for rhodamine B degradation. The mechanism of visible-light induced photocatalysis over Ag/g-C3N4 photocatalysts was also discussed. 相似文献
999.
Molybdenum doped graphitic carbon nitride (g-C3N4) catalysts were prepared by a simple pyrolysis method using melamine and ammonium molybdate as precursors. The characterization results indicated that the obtained Mo-doped g-C3N4 catalysts had worm-like mesostructures with higher surface area. Introduction of Mo species can effectively extend the spectral response property and reduce the recombination rate of photogenerated electrons and holes. CO2 photocatalytic reduction tests showed that the Mo-doped g-C3N4 catalysts exhibited considerably higher activity (the highest CO and CH4 yields of 887 and 123 μmol g− 1-cat., respectively, after 8 h of UV irradiation.) compared with pure g-C3N4 from melamine. 相似文献
1000.
《Ceramics International》2016,42(6):6664-6672
Undoped and Zn-doped CuCrO2 nanoparticles were synthesized by sol–gel method as promising wide band gap p-type semiconductor materials for solid-state dye-sensitized solar cells (DSSCs). We studied the influence of Zn dopant concentration on structural, electrical and optical properties of CuCrO2 nanoparticles. The X-ray diffraction data indicated that the delafossite-to-spinel ferrite phase transition occurs by increasing the amount of Zn doping. The average nanoparticle size was determined about 40 nm. A minimum value of electrical resistivity of 5.7 Ω cm was obtained for doping concentration of 5%. Having optimized the Zn-doped CuCrO2 nanoparticles, solid-state DSSCs were fabricated using undoped and Zn-doped CuCrO2 (5%) as solid electrolytes. As the photoanode layer, the vertically aligned TiO2 nanorod arrays were grown on FTO glass using a hydrothermal method. Compared with undoped CuCrO2, the Zn-doped nanoparticles exhibited an improvement in photovoltaic properties. The overall efficiency enhancement of 39% was obtained for the dopant concentration of 5%. The improved power conversion efficiency is attributed to the lowered electrical resistivity and enlarged work function of Zn-doped CuCrO2 nanoparticles. 相似文献