全文获取类型
收费全文 | 25067篇 |
免费 | 1941篇 |
国内免费 | 1433篇 |
专业分类
电工技术 | 409篇 |
技术理论 | 1篇 |
综合类 | 1030篇 |
化学工业 | 8066篇 |
金属工艺 | 6907篇 |
机械仪表 | 1180篇 |
建筑科学 | 1066篇 |
矿业工程 | 291篇 |
能源动力 | 542篇 |
轻工业 | 1549篇 |
水利工程 | 63篇 |
石油天然气 | 559篇 |
武器工业 | 207篇 |
无线电 | 864篇 |
一般工业技术 | 4395篇 |
冶金工业 | 1090篇 |
原子能技术 | 119篇 |
自动化技术 | 103篇 |
出版年
2024年 | 165篇 |
2023年 | 527篇 |
2022年 | 741篇 |
2021年 | 895篇 |
2020年 | 846篇 |
2019年 | 766篇 |
2018年 | 808篇 |
2017年 | 967篇 |
2016年 | 830篇 |
2015年 | 900篇 |
2014年 | 1269篇 |
2013年 | 1353篇 |
2012年 | 1610篇 |
2011年 | 1863篇 |
2010年 | 1490篇 |
2009年 | 1461篇 |
2008年 | 1221篇 |
2007年 | 1522篇 |
2006年 | 1544篇 |
2005年 | 1289篇 |
2004年 | 1133篇 |
2003年 | 930篇 |
2002年 | 815篇 |
2001年 | 654篇 |
2000年 | 593篇 |
1999年 | 434篇 |
1998年 | 377篇 |
1997年 | 296篇 |
1996年 | 265篇 |
1995年 | 213篇 |
1994年 | 165篇 |
1993年 | 144篇 |
1992年 | 127篇 |
1991年 | 63篇 |
1990年 | 50篇 |
1989年 | 50篇 |
1988年 | 19篇 |
1987年 | 5篇 |
1986年 | 15篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1976年 | 1篇 |
1959年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
182.
本文采用溶胶-凝胶法以组成为3Al2O32SiO2的混合溶胶分别于常压和压力条件下,对SiC微细粉进行包覆处理,该涂覆层在低于1000℃下经1h热处理可结晶成莫来石层,研究了涂覆溶胶浓度、涂覆压力对涂层厚度、结晶化温度等的影响,涂覆后的SiC微粉在中高温的表面抗氧化性明显提高 相似文献
183.
炼厂外排污水回用于循环冷却水腐蚀影响因素初探 总被引:3,自引:0,他引:3
从单因素、多因素和复杂水系考察了炼厂外排污水回用于循环冷却水腐蚀的影响因素,结果表明,碳钢腐蚀的主要影响因素取决于离子特性、氧化膜的形成和溶解氧的扩散等综合协同作用,其中以离子特性的,影响为最大(如:Cl^-、Ca^2 、CO3^2-的腐蚀性较强)。碳钢腐蚀反应又可由以上三种主要影响因素分为三个反应控制区,而当电导率在0.1-2.0mS/cm范围时,其水质属于腐蚀危险高发区。从而也进一步说明水质的低电导率处理,其防腐效果并不理想,相反在高电导率情况下却表现出相对较好的低腐蚀性能。 相似文献
184.
This study determines the influences of siloxane flow agents’ migration on the outermost surface composition of clearcoats, before and after ethanol cleaning. This evaluation is undertaken to improve adhesion of pressure-sensitive adhesives (PSAs) on automotive paint systems. Most of the siloxane flow agents segregate from the bulk to the clearcoat outermost surface during curing. These additives can cover until 50% of the surface area but X-ray photoelectron spectroscopy (XPS) and time of flight-secondary ion mass spectrometry (ToF-SIMS) analyses indicate that they can be removed by ethanol cleaning. Composition of the cleaned clearcoats surfaces are similar as the composition of clearcoat formulated without siloxane additives: the polyester-(melamine)-polyurethane network is more detected than before cleaning. However, outermost surface analyses show that several aging weeks increase the siloxane additives segregation. This post-cleaning migration modifies the clearcoat surface composition and cancels the chemical modifications due to the ethanol cleaning. XPS analyses show that silicon concentrations after cleaning and aging are inversely proportional to the initial silicon concentrations measured after curing. It highlights that aging has to be controlled to improve adhesion of PSAs on clearcoats. A second ethanol cleaning on aged clearcoats is not effective to remove these new siloxane additives. Their formulation should be different from the flow agents and it could modify their solubility in ethanol. This result could also indicate that these new siloxane additives are not located on the last molecular layer of surface and they would not be soluble in ethanol. 相似文献
185.
G. Zhang W.-Y. Li M. Cherigui C. Zhang H. Liao J.-M. Bordes C. Coddet 《Progress in Organic Coatings》2007
Driven by economical and ecological reasons, thermoplastic-based coatings become a potential solution for anti-wear purpose. Two coating design concepts, flame spraying and printing PEEK (poly-ether-ether-ketone)-based coatings on Al substrate, were introduced in this paper. An amorphous PEEK coating was obtained by these two techniques. After being annealed, the coating presents a semi-crystalline structure. The friction and wear behaviors of PEEK-based coatings were investigated by means of ball-on-disc tests. The results show that PEEK coatings exhibit an excellent tribological performance with a relatively low coefficient of friction and wear rate. The semi-crystalline PEEK coating exhibits a lower friction coefficient and wear rate than the amorphous one. The additions of micron-sized particles such as SiC and graphite in PEEK coating can improve significantly the coating wear resistance. 相似文献
186.
The chemical composition and quantitative molar ratios among all components of biodegradable polyphosphoester copolymers of DL ‐lactide and ethylphosphate were determined by a comprehensive set of NMR spectroscopic methods. The polyphosphoester copolymers studied were synthesized using condensation polymerization of oligomeric DL ‐lactide prepolymers and ethyl dichlorophosphate. Conclusive identification of the chemical shift patterns of all functional groups in the copolymers required additional NMR methods such as 31P‐NMR and two‐dimensional 1H–1H COSY NMR, in addition to the synthesis and comparative NMR analysis of model compounds possessing identical phosphoester linkages in the polyphosphoester copolymers. For the polymers synthesized using the bulk polycondensation process, 1H–1H COSY NMR analysis revealed the presence of a small amount of side products that were undetected by 1H‐NMR alone. These side reactions most likely occurred between the pendant ethoxy group of the phosphoesters and the hydrogen chloride gas generated in the bulk polycondensation process. 31P‐NMR spectra of the copolymers revealed a consistent triple‐peak pattern characteristic of phosphoesters linked to a racemic mixture of D,L ‐lactides. These results offered new insight into the side reactions occurring in bulk polymerization of polyphosphoesters and provided a powerful tool of characterizing complex biodegradable polymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4021–4031, 2003 相似文献
187.
188.
新型碳纤维复合芯导线具有良好的力学性能和电气特性,与等径钢芯铝绞线相比,其主要有芯线强度高、导电率高、载流量大、质量轻、耐腐蚀、弧垂小等优点;与普通碳纤维导线相比,新型碳纤维复合芯导线采用铝包覆技术,在配套金具、导线压接和施工工艺等方面都有较大改进。以110~500 kV新建线路为例,对185~800 mm~2截面的新型碳纤维复合芯导线进行了全面的经济性比较。研究结果得到:对于500 kV新建双回线路,推荐采用JLRX1/F2A-710/50、JLRX1/F2A-800/50导线;对于220 kV新建双回线路,推荐采用JLRX1/F2A-400/50、JLRX1/F2A-450/50导线;对于110 kV新建双回线路,推荐采用JLRX1/F2A-300/40、JLRX1/F2A-360/40导线。 相似文献
189.
The kinetics of polymerization of ?‐caprolactone (CL) in bulk was studied by irradiating with microwave of 350 W and frequency of 2.45 GHz with different cycle‐heating periods (30–50 s). The molecular weight distributions were determined as a function of reaction time by gel permeation chromatography. Because the temperature of the system continuously varied with reaction time, a model based on continuous distribution kinetics with time/temperature‐dependent rate coefficients was proposed. To quantify the effect of microwave on polymerization, experiments were conducted under thermal heating. The polymerization was also investigated with thermal and microwave heating in the presence of zinc catalyst. The activation energies determined from temperature‐dependent rate coefficients for pure thermal heating, thermally aided catalytic polymerization, and microwave‐aided catalytic polymerization were 24.3, 13.4, and 5.7 kcal/mol, respectively. This indicates that microwaves increase the polymerization rate by lowering the activation energy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1450–1456, 2004 相似文献
190.