全文获取类型
收费全文 | 14920篇 |
免费 | 1945篇 |
国内免费 | 502篇 |
专业分类
电工技术 | 1105篇 |
技术理论 | 1篇 |
综合类 | 1153篇 |
化学工业 | 3011篇 |
金属工艺 | 779篇 |
机械仪表 | 923篇 |
建筑科学 | 1371篇 |
矿业工程 | 757篇 |
能源动力 | 669篇 |
轻工业 | 1060篇 |
水利工程 | 411篇 |
石油天然气 | 523篇 |
武器工业 | 60篇 |
无线电 | 1427篇 |
一般工业技术 | 1434篇 |
冶金工业 | 586篇 |
原子能技术 | 192篇 |
自动化技术 | 1905篇 |
出版年
2024年 | 58篇 |
2023年 | 416篇 |
2022年 | 543篇 |
2021年 | 782篇 |
2020年 | 670篇 |
2019年 | 509篇 |
2018年 | 452篇 |
2017年 | 448篇 |
2016年 | 511篇 |
2015年 | 868篇 |
2014年 | 1632篇 |
2013年 | 1506篇 |
2012年 | 2174篇 |
2011年 | 1976篇 |
2010年 | 1158篇 |
2009年 | 1096篇 |
2008年 | 490篇 |
2007年 | 635篇 |
2006年 | 559篇 |
2005年 | 190篇 |
2004年 | 108篇 |
2003年 | 82篇 |
2002年 | 79篇 |
2001年 | 64篇 |
2000年 | 88篇 |
1999年 | 95篇 |
1998年 | 54篇 |
1997年 | 36篇 |
1996年 | 20篇 |
1995年 | 15篇 |
1994年 | 14篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《Ceramics International》2022,48(3):3720-3728
In this paper, a stable lithium niobate (LN) sol was prepared using niobium pentachloride, niobium ethoxide, lithium acetate, anhydrous ethanol, and benzoylacetone (BzAcH) as a chemical modifier. The effects of different starting materials and organic solvents on the obtained gel film quality of the sols were studied and the optimization mechanism of BzAcH on the film quality was analyzed in detail. The effects of heat treatment temperature on the structure and performance of the LN thin films were also studied. X-ray diffraction (XRD) spectra showed that LN was more highly crystalline in the heat treatment temperature range of 600–800 °C. The refractive index of the LN thin films first increased and then decreased with increasing heat treatment temperature, and the LN thin film prepared at 700 °C had the largest refractive index. Light transmittance tests showed that as the heat treatment temperature increased, light transmittance decreased. Finally, it was determined that LN gel films modified with BzAcH were more highly sensitive to UV light and that after UV irradiation, it was difficult to dissolve LN gel films in organic solvent. The UV-sensitive property was utilized to realize microstructure processing of the LN thin films. The results indicated that a high-quality, non-destructive, and photoresist-free micro-fabrication method was realized. This method was used to fabricate microscale LN fine patterns with smooth sidewalls while avoiding lateral corrosion. These results are of great significance for LN thin film applications and the development of LN-based optoelectronic devices prepared by chemical methods. 相似文献
2.
《International Journal of Hydrogen Energy》2022,47(80):34244-34256
A conducting and anticorrosive coating is crucial for the application of metal bipolar plates (BP) in proton exchange membrane fuel cell (PEMFC). In this work, a Ti3C2Tx (T)-carbon black (C)-acrylic epoxy (AE) coating is prepared on 304 stainless steel (SS) with enhanced corrosion resistance and conductivity. The corrosion resistance of the T-C-AE coating is investigated in a 0.5 M H2SO4 solution as compared to the AE, T, and T-AE coatings. The T-C-AE coated 304SS exhibits the strongest corrosion resistance with the most positive corrosion potential and the lowest corrosion current density of 0.00673 μA cm?2 in all the samples, while retaining intact and compact surface morphology with the lowest metal ion dissolution even after immersed for 720 h. The addition of Ti3C2Tx and carbon black into the AE matrix greatly decreases interfacial contact resistance (ICR), and the T-C-AE coating achieves a low ICR of 15.5 mΩ cm?2 under 140 N cm?2 compaction force. The excellent anticorrosion performance is mainly attributed to the physical barrier and the cathodic protection provided by the stacked Ti3C2Tx (MXene) nanosheets in the T-C-AE coating. This eco-friendly, conducting, and anticorrosive T-C-AE coating has a good application prospect on SS BP of PEMFC. 相似文献
3.
《Geotextiles and Geomembranes》2022,50(4):794-806
A study on the liquefaction resistance of calcareous sands reinforced with polypropylene fibers was reported. Stress-controlled cyclic simple shear tests were conducted on specimens prepared at a relative density of 50%, with and without fiber reinforcements. The liquefaction behavior was investigated by considering the effects of fiber contents ranging from 0% to 1%, fiber lengths varying from 3 mm to 12 mm and loading patterns. The results indicated that increasing fiber content and fiber length resulted in a decrease in the deformation, a reduction in pore pressure accumulation rate, and improved the liquefaction resistance of calcareous sands. Additionally, the risk of soil liquefaction could be significantly reduced when the fiber content was greater than 0.8%. The multidirectional loading had a considerable effect in reducing the liquefaction resistance compared to unidirectional loading. Further, the stiffness degradation of calcareous sands decreased with increasing fiber content and fiber length. The pore pressure generated in the cyclic tests was analyzed and was found to be affected by fiber content. A pore pressure prediction model was proposed to obtain the pore pressure characteristics of fiber-reinforced calcareous sands under various fiber content conditions. 相似文献
4.
《Geotextiles and Geomembranes》2022,50(5):1020-1035
This paper presents a numerical study on the load-bearing performance of reinforced slopes under footing load using a finite element limit analysis (FELA) method where a non-associated flow rule is assumed in the analysis. The method was validated against results from full-scale model tests and a limit equilibrium (LE) analytical method. A series of parametric analyses was subsequently carried out to examine the influences that the soil dilation angle, footing location, and reinforcement design (i.e. length, tensile strength, and vertical spacing) could have on the load-bearing performance of reinforced slopes. Results indicate that dilation angle has a significant influence on the predicted magnitudes of bearing capacity, slope deformation, and mobilized reinforcement load. The predicted values of bearing capacity using the FELA are smaller than those from the Meyerhof's analytical method for unreinforced semi-infinite foundation, especially for larger friction angle values. Additionally, the ultimate bearing capacity of the slope and its corresponding horizontal deformation increase with the reinforcement tensile strength. Finally, the slip planes under the applied footing load are found to be y-shaped and primarily occur in the upper half of the slope. 相似文献
5.
6.
本文提出一种基于实时几何测距的船桥主动防撞方法。该方法对船的改动量甚微,仅需维持多项距离矩阵,通过告警逻辑矩阵进行展示与告警,能起到很好的船桥防撞提示效果。 相似文献
7.
This work investigated incorporation of Nannochloropsis salina into renneted dairy gels and curd. Whole and ruptured microalgal cells did not impair κ-casein macropeptide cleavage by the rennet enzyme. However, insoluble components of ruptured cells impeded gelation, presumably by hindering interactions between renneted casein micelles. Confocal imaging showed that whole cells were retained and homogenously distributed within the protein network of the gels and cooked curd, whereas ruptured algae formed large aggregates that altered the protein matrix. Eicosapentaenoic acid (EPA) in the whole microalgal cells was incorporated within the curds, with considerably less EPA retained for ruptured cells. Soluble algal debris did not impair gelation, however EPA wasn't retained in the curd. The study demonstrates that nutrient enrichment of renneted dairy products is possible by incorporating whole microalgal cells to displace milk fat with protein and the beneficial long-chain omega-3 fatty acid EPA. Future research into the optimisation of product organoleptic properties is required. 相似文献
8.
《Ceramics International》2022,48(13):18151-18156
The electrical properties and domain reversal in BiFeO3 ferroelectric films were studied using sandwiched heterostructures and piezoresponse force microscopy. A robust polarization state was observed, combined with a switchable domain pattern and a remanent polarization of approximately 100 μC cm?2. In addition, domain reversal was explored using scanning probe microscopy. The results show that dipoles could be reversed along the direction of the electric field under a negative tip bias, leading to carrier gathering near the domain walls. The enhanced conductivity near the domain walls was owing to the discontinuous polarization boundary conditions. In addition, typical diode-like current transport properties are sensitive to various temperature conditions, which is attributed to the Schottky barriers at the contact interface. These findings extend the current understanding of domain texture reversal in ferroelectric films and shed light on their potential applications for future ferroelectric random-access memory operations over a wide temperature range. 相似文献
9.
空孔在岩石巷道直眼掏槽爆破中具有重要作用,为研究空孔及其缺陷在爆炸荷载作用下的扩展行为和作用机理,以PMMA代替岩石材料,利用预制裂纹代替空孔缺陷,借助动态焦散线系统和理论分析为手段,研究不同间距下空孔、空孔处预制裂纹、爆生裂纹动态扩展规律及机理,分析不同"径距比"与掏槽效果的关系。研究结果表明:在装药量一定的情况下,随着炮孔与空孔距离的变化,爆生裂纹扩展距离呈现递增而预制裂纹扩展距离呈现递减的趋势,但都存在极值;当炮孔与空孔距离较小时,爆生裂纹和预制裂纹扩展及相互作用最复杂,爆生裂纹扩展经历由压缩应力波为主,表现为直线的前期扩展;由空孔处发射应力波和压缩应力波共同作用下,爆生裂纹偏离炮孔与空孔连心线的中期扩展,以及由空孔应力集中区作用使爆生裂纹向空孔方向偏移的后期阶段;预制裂纹扩展经历由空孔处应力集中作用下,表现为直线的前期扩展,以及由爆生裂纹处反射拉伸波作用使其向爆生裂纹发展的后期阶段;当炮孔与空孔距离较大时,反射应力波及应力集中效应对爆生裂纹和预制裂纹扩展在减弱,爆生裂纹与预制裂纹扩展行为仅有前期直线扩展阶段。"径距比"的大小对爆破效果影响较大,直眼掏槽爆破应以最优"径距比"作为掏槽爆破参数设计的依据。 相似文献
10.