全文获取类型
收费全文 | 62340篇 |
免费 | 8051篇 |
国内免费 | 4340篇 |
专业分类
电工技术 | 11044篇 |
技术理论 | 1篇 |
综合类 | 6093篇 |
化学工业 | 8747篇 |
金属工艺 | 3023篇 |
机械仪表 | 3068篇 |
建筑科学 | 4642篇 |
矿业工程 | 2350篇 |
能源动力 | 2381篇 |
轻工业 | 3001篇 |
水利工程 | 2027篇 |
石油天然气 | 3285篇 |
武器工业 | 659篇 |
无线电 | 5863篇 |
一般工业技术 | 6278篇 |
冶金工业 | 3172篇 |
原子能技术 | 1086篇 |
自动化技术 | 8011篇 |
出版年
2024年 | 323篇 |
2023年 | 977篇 |
2022年 | 1830篇 |
2021年 | 2202篇 |
2020年 | 2467篇 |
2019年 | 2141篇 |
2018年 | 1999篇 |
2017年 | 2555篇 |
2016年 | 2555篇 |
2015年 | 2672篇 |
2014年 | 3915篇 |
2013年 | 4377篇 |
2012年 | 4495篇 |
2011年 | 4753篇 |
2010年 | 3455篇 |
2009年 | 3667篇 |
2008年 | 3479篇 |
2007年 | 3952篇 |
2006年 | 3658篇 |
2005年 | 3067篇 |
2004年 | 2631篇 |
2003年 | 2279篇 |
2002年 | 1943篇 |
2001年 | 1574篇 |
2000年 | 1314篇 |
1999年 | 1166篇 |
1998年 | 906篇 |
1997年 | 748篇 |
1996年 | 597篇 |
1995年 | 539篇 |
1994年 | 530篇 |
1993年 | 354篇 |
1992年 | 286篇 |
1991年 | 250篇 |
1990年 | 221篇 |
1989年 | 188篇 |
1988年 | 137篇 |
1987年 | 101篇 |
1986年 | 75篇 |
1985年 | 68篇 |
1984年 | 50篇 |
1983年 | 37篇 |
1982年 | 37篇 |
1981年 | 18篇 |
1980年 | 21篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1964年 | 8篇 |
1959年 | 16篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
磷酸酯淀粉在纯棉细特高密织物浆纱中的应用 总被引:2,自引:0,他引:2
就磷酸酯淀粉在纯棉细号高密织物中的上浆情况进行了试验,提出了具体浆纱工艺和减少织造断头率,提高织物效率及布面质量对策,实验表明,磷酸酯淀粉完全适应于纯绵细特高密织物的上浆要求。 相似文献
72.
对照IS0 9001质量管理体系标推的要求,结合石化销售企业质量管理工作中存在的主要问题,提出质量管理工作创新的建议。 相似文献
73.
Uniformity of bulk density distribution during the die filling process is required to minimize quality problems, such as distortion and cracking, for powder compacts. Understanding the die filling process is necessary in ensuring a uniform powder deposition. The second-generation pressure deposition tester (PDT-II) was used to investigate the deposition process and final pressure distribution of powder filling in toroidal, cylindrical, and E-shaped dies. All tests were conducted using a spray-dried free-flowing granular powder. The results indicated that for toroidal dies: (1) the area around 0° orientation (the leeward end) had the highest pressure values (1186.7 to 2498.0 Pa), with the average pressure values of the remaining area 353.7-648.0 Pa; (2) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; (3) the highest feed shoe speed (500 mm/s) led to the most nonuniform pressure distribution among the three speeds; (4) higher feed shoe speed did not always result in higher final pressure values; and (5) the right die tended to have higher final pressure values (215.0 to 2498.0 Pa) than the center die (95.4 to 2052.5 Pa). For E-shaped dies: (1) the final pressure values of the middle leg (308.9 to 760.7 Pa) were higher than those of the left and the right legs (148.9 to 530.3 Pa); (2) the area along the backside had the highest final pressure value (1054.6 to 1303.8 Pa); (3) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; and (4) neither the center die nor the right die always had higher pressure values than the other one at all locations. Comparison between cylindrical and toroidal dies indicated that: (1) neither of the two die shapes (cylinder and toroid) led to consistently higher or lower final pressure values at all locations and (2) for all three feed shoe speeds, the toroidal die had higher average final pressure values in the 0° orientation. 相似文献
74.
模拟计算表明:采用活性趋于表层的分布,可以较明显地提高国产中温变换催化剂的内表面利用率,有效地节省催化剂用量,而对“热点”温度没有多大影响。 相似文献
75.
This paper deals with the non-steady-state kinetics of direct thermal initiated polymerization. The initiation is assumed to be a bimolecular reaction of the monomer. The relationship between the radical concentration and the monomer conversion is rigorously derived. In further treatment a few very close approximations are introduced based on the fact that the number of monomer molecules reacting in the initiation step is much less than that consumed in the propagation step for a process producing high polymer, and the value of the rate constant for propagation or chain transfer is much lower than that for chain termination. Expressions for various molecular parameters, such as molecular weight distribution, number-average and weight-average degrees of polymerization, and dispersity, are given. Several numerical examples are provided. 相似文献
76.
对掺氟化镨玻璃光纤放大器的小信号增益,用广义的高斯近似公式可获得精确的分析表达。文中研究了限制光纤芯层中央部分的镨掺杂对光纤放大器特性的影响,结果发现限制镨掺杂分布能改进光纤放大器的工作效率,且截止波长比芯层全部均匀掺镨的光纤更长。 相似文献
77.
A finite element formulation and the solution of a set of nonlinear coupled heat and mass transfer equations for a two-phase system with a moving evaporation interface is presented. The interface condition takes into account the moisture transfer balance at the moving boundary. The finite element results were compared with existing results for a single phase system for model validation. In the two-phase system, the movement of evaporation front has an appreciable effect on the temperature and moisture distribution inside the porous medium during drying. The effect of the nondimensional heat of vapourization parameter γ on the evaporation front, temperature and moisture distribution in porous medium was studied. The higher the value of γ, the slower is the movement of the evaporation front. The temperature decreased and the moisture content increased as the nondimensional vapourization parameter γ increased. This model has potential applications in studying the heat and mass transfer characteristics in food and biomaterials. 相似文献
78.
锻热淬火工艺对工具钢碳化物粒度的影响 总被引:6,自引:1,他引:5
研究了锻热淬火工艺对T10钢和GCr15钢碳化物技度的影响。结果表明,碳化物粒度随变形量的增大而细化;终锻温度在高于碳化物析出的温度范围内变化,其碳化物粒度都同样细小;终锻温度不宜过低,否则将使碳化物变粗。 相似文献
79.
斯新中 《石油化工设备技术》1996,17(4):1-3
根据十万立方米浮顶油罐罐壁板应力测试的实测结果,运用应力分析程序,对罐壁板应力分布情况进行了分析和比较,通过调整罐壁板的厚度,使新设计储罐的罐壁板应力分布更加均匀、合理。 相似文献
80.
StudyonFactorsAffectingtheStructureofHighSpeedSteelIngotProducedbyESRLiZhengbang;CheXiangqianAbstract:Theinfluenceofthemetalp... 相似文献