全文获取类型
收费全文 | 65538篇 |
免费 | 4902篇 |
国内免费 | 3288篇 |
专业分类
电工技术 | 3085篇 |
综合类 | 4176篇 |
化学工业 | 9251篇 |
金属工艺 | 4413篇 |
机械仪表 | 5542篇 |
建筑科学 | 6387篇 |
矿业工程 | 5375篇 |
能源动力 | 3749篇 |
轻工业 | 4023篇 |
水利工程 | 2104篇 |
石油天然气 | 7825篇 |
武器工业 | 659篇 |
无线电 | 3278篇 |
一般工业技术 | 6218篇 |
冶金工业 | 2868篇 |
原子能技术 | 1324篇 |
自动化技术 | 3451篇 |
出版年
2024年 | 201篇 |
2023年 | 745篇 |
2022年 | 1503篇 |
2021年 | 1972篇 |
2020年 | 2037篇 |
2019年 | 1648篇 |
2018年 | 1611篇 |
2017年 | 1973篇 |
2016年 | 2149篇 |
2015年 | 2205篇 |
2014年 | 3947篇 |
2013年 | 4036篇 |
2012年 | 4614篇 |
2011年 | 5290篇 |
2010年 | 3635篇 |
2009年 | 3564篇 |
2008年 | 3161篇 |
2007年 | 3905篇 |
2006年 | 3884篇 |
2005年 | 3255篇 |
2004年 | 2923篇 |
2003年 | 2407篇 |
2002年 | 2116篇 |
2001年 | 1853篇 |
2000年 | 1608篇 |
1999年 | 1420篇 |
1998年 | 1159篇 |
1997年 | 1021篇 |
1996年 | 805篇 |
1995年 | 728篇 |
1994年 | 590篇 |
1993年 | 326篇 |
1992年 | 297篇 |
1991年 | 245篇 |
1990年 | 183篇 |
1989年 | 177篇 |
1988年 | 118篇 |
1987年 | 83篇 |
1986年 | 72篇 |
1985年 | 59篇 |
1984年 | 29篇 |
1983年 | 21篇 |
1982年 | 22篇 |
1981年 | 22篇 |
1980年 | 22篇 |
1979年 | 21篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1964年 | 6篇 |
1959年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
随着设备高速化的日益发展,传统的螺杆设计方法及相应的供送特性评价体系已显落后。参照蜗型凸轮动力学性能的评价方法,建立了高速供送螺杆的动态性能评价体系,为高速化供送螺杆的设计提供了性能参照指标。 相似文献
42.
43.
正压冲固基础海洋平台冰激振动动力响应 总被引:1,自引:0,他引:1
正压冲固基础海洋平台是一种新型平台桩基结构形式。采用三维有限元的数值分析方法,建立了正压冲固平台的三维有限元模型。基于冰激强迫振动理论提出动冰载荷的计算方法,根据海冰破碎长度和冰速确定冰载周期,冰强度限制的水平冰力作为冰力峰值,得到的动冰载荷用于正压冲固平台的动力响应分析,并依照规范计算了6倍桩径处刚性固定时的动力响应。三维有限元方法计算得到的动力响应大于6倍桩径刚性固定时的计算结果,结构安全性评估偏于安全。 相似文献
44.
A semi-empirical mathematical model for the acid-oxygen pressure leaching of Ni–Cu matte is presented, based on data from batch leaching experiments. The primary controlling factor in the leaching process is found to be galvanic inhibition of the more highly oxidized copper and nickel sulfide species by less oxidized species, particularly Ni alloy and Ni3S2. The leaching rate of many species is greatly reduced by the presence of one or both of these phases, and others will not commence leaching until neither is present. The mathematical model is based on first-order chemical reaction controlled rate expressions, as the reactions occurring are electrochemical in nature. Mass transfer effects are included only empirically. Some possibly diffusion-related phenomena are noted, although the model is not extended to incorporate these effects on a fundamental level. The model is verified and extended by the inclusion of several different factors that were tested experimentally. The effects of variations in O2 flow rate and partial pressure, initial particle size, reaction pulp density and initial acid concentration were all studied, and included in the model. Variations in O2 flow rate and partial pressure are found to affect the reaction rates via the dissolved oxygen concentration in the solution phase. 相似文献
45.
LED生产过程中的质量控制 总被引:2,自引:0,他引:2
对LED封装过程可能出现的问题逐一指出,并提出解决的办法,着重介绍封装位置对LED发光亮度的影响。以期引起LED封装管理人员及工作人员的注意。 相似文献
46.
47.
建(构)筑物机械拆除方法综述 总被引:1,自引:0,他引:1
介绍了几种常用的建(构)筑物机械拆除方法,对其工作原理、特点、应用条件及局限性加以分析和说明。 相似文献
48.
49.
In accord with the increasing concern about the global environmental issues, the absorption refrigeration heat-pump systems are currently being considered very promising and attractive. For the purpose of supporting the advanced R&D technology in this area, we have developed a novel correlation to represent the bubble-point pressures of LiBr H2O solutions. The developed correlation covers the most extensive range of validity ever proposed: 273–483 K for temperatures, 0.05 kPa to 1.0 MPa for pressures. and 29 76 wt% LiBr for concentrations.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994. Boulder, Colorado, U.S.A. 相似文献
50.
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