全文获取类型
收费全文 | 140230篇 |
免费 | 11453篇 |
国内免费 | 6176篇 |
学科分类
工业技术 | 157859篇 |
出版年
2024年 | 277篇 |
2023年 | 2079篇 |
2022年 | 3071篇 |
2021年 | 4989篇 |
2020年 | 3943篇 |
2019年 | 3313篇 |
2018年 | 3787篇 |
2017年 | 4276篇 |
2016年 | 3727篇 |
2015年 | 5127篇 |
2014年 | 6543篇 |
2013年 | 8101篇 |
2012年 | 8673篇 |
2011年 | 9433篇 |
2010年 | 8361篇 |
2009年 | 8151篇 |
2008年 | 8321篇 |
2007年 | 7761篇 |
2006年 | 7917篇 |
2005年 | 6810篇 |
2004年 | 4909篇 |
2003年 | 4348篇 |
2002年 | 4302篇 |
2001年 | 4018篇 |
2000年 | 3666篇 |
1999年 | 3894篇 |
1998年 | 3185篇 |
1997年 | 2786篇 |
1996年 | 2460篇 |
1995年 | 2086篇 |
1994年 | 1652篇 |
1993年 | 1278篇 |
1992年 | 1027篇 |
1991年 | 775篇 |
1990年 | 617篇 |
1989年 | 518篇 |
1988年 | 406篇 |
1987年 | 298篇 |
1986年 | 205篇 |
1985年 | 166篇 |
1984年 | 95篇 |
1983年 | 77篇 |
1982年 | 90篇 |
1981年 | 64篇 |
1980年 | 68篇 |
1979年 | 36篇 |
1978年 | 24篇 |
1977年 | 25篇 |
1976年 | 40篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 781 毫秒
51.
Lü Qing Xu Bin Yu Yang Zhan Wei Zhao Yu Zheng Jun Ji Jian 《Bulletin of Engineering Geology and the Environment》2021,80(8):6513-6525
Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability... 相似文献
52.
53.
54.
在45钢表面电刷镀得到三价铬镀层,镀液组成和工艺条件为:Cr2(SO4)36H2O 0.4 mol/L,甲酸铵0.5 mol/L,氨基乙酸0.5 mol/L,H3BO30.6 mol/L,NaH2PO2 H2O 0.3 mol/L,pH=1.5,温度50°C,镀笔移动速率15 cm/s。研究了电压对镀铬层显微结构、表面粗糙度、厚度、显微硬度和耐磨性的影响。随电压增大,镀层厚度增大,显微硬度和耐磨性均先提高后降低。电压为14 V时,镀层的表面平整,粗糙度为2.387μm,显微硬度为602 HV,耐磨性最好。 相似文献
55.
57.
58.
不同折流板结构螺旋折流板换热器传热性能的比较(英文) 总被引:1,自引:0,他引:1
Numerical simulations were performed on flow and heat transfer performances of heat exchangers having six helical baffles of different baffle shapes and assembly configurations, i.e., two trisection baffle schemes, two quadrant baffle schemes, and two continuous helical baffle schemes. The temperature contour or the pressure contour and velocity contour plots with superimposed velocity vectors on meridian, transverse and unfolded concentric hexagonal slices are presented to obtain a full angular view. For the six helix baffled heat exchangers, the different patterns of the single vortex secondary flow and the shortcut leakage flow were depicted as wel as the heat transfer properties were compared. The results show that the optimum scheme among the six configurations is a circumferential overlap trisection helix baffled heat exchanger with a baffle incline angle of 20° (20°TCO) scheme with an anti-shortcut baffle structure, which exhibits the second highest pressure dropΔpo, the highest overal heat transfer coefficient K, shel-side heat transfer coefficient ho and shel-side average comprehensive index ho/Δpo. 相似文献
59.
Thermally conductive polymers offer new possibilities for the heat dissipation in electric and electronic components, for example, by a three‐dimensional shaping of the heat sinks. To face safety regulations, improved fire performance of those components is required. In contrast to unfilled polymers, those materials exhibit an entirely different thermal behavior. To investigate the flammability, a phosphorus flame retardant was incorporated into thermally conductive composites of polyamide 6 and hexagonal boron nitride. The flame retardant decreased the thermal conductivity only slightly. However, the burning behavior changed significantly, due to a different heat propagation, which was investigated using a thermographic camera. An optimum content of hexagonal boron nitride for a sufficient thermal conductivity and fire performance was found between 20 and 30 vol%. The improvement of the fire performance was due to a faster heat release out of the pyrolysis zone and an earlier decomposition of the flame retardant. For higher contents of hexagonal boron nitride, the heat was spread faster within the part, promoting an earlier ignition and increasing the decomposition rate of the flame retardant. 相似文献