全文获取类型
收费全文 | 35236篇 |
免费 | 3830篇 |
国内免费 | 2126篇 |
专业分类
电工技术 | 2526篇 |
技术理论 | 2篇 |
综合类 | 3024篇 |
化学工业 | 5449篇 |
金属工艺 | 1763篇 |
机械仪表 | 1915篇 |
建筑科学 | 2944篇 |
矿业工程 | 1039篇 |
能源动力 | 952篇 |
轻工业 | 3640篇 |
水利工程 | 811篇 |
石油天然气 | 1671篇 |
武器工业 | 334篇 |
无线电 | 4067篇 |
一般工业技术 | 4005篇 |
冶金工业 | 1693篇 |
原子能技术 | 356篇 |
自动化技术 | 5001篇 |
出版年
2024年 | 291篇 |
2023年 | 934篇 |
2022年 | 1636篇 |
2021年 | 2141篇 |
2020年 | 1483篇 |
2019年 | 1206篇 |
2018年 | 1320篇 |
2017年 | 1448篇 |
2016年 | 1212篇 |
2015年 | 1597篇 |
2014年 | 2023篇 |
2013年 | 2318篇 |
2012年 | 2410篇 |
2011年 | 2463篇 |
2010年 | 2041篇 |
2009年 | 1972篇 |
2008年 | 1940篇 |
2007年 | 1830篇 |
2006年 | 1726篇 |
2005年 | 1404篇 |
2004年 | 1043篇 |
2003年 | 1005篇 |
2002年 | 1035篇 |
2001年 | 959篇 |
2000年 | 675篇 |
1999年 | 612篇 |
1998年 | 558篇 |
1997年 | 409篇 |
1996年 | 316篇 |
1995年 | 250篇 |
1994年 | 222篇 |
1993年 | 146篇 |
1992年 | 106篇 |
1991年 | 86篇 |
1990年 | 63篇 |
1989年 | 57篇 |
1988年 | 45篇 |
1987年 | 30篇 |
1986年 | 32篇 |
1985年 | 16篇 |
1984年 | 9篇 |
1983年 | 18篇 |
1982年 | 18篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1979年 | 11篇 |
1977年 | 10篇 |
1976年 | 14篇 |
1975年 | 5篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
The public information signs ( The term public information signs will be abbreviated to public signs in the following text.)in the urban areas not only offer convenience for people to move around, but also reflect the level of development and progress of those areas. It is essential to the creative development and uplifting of the New Costal Area (thereafter, NCA) to have a good understanding of its present situation with regard to its public signs, to discuss the related issues in the development, to work out a system that is up to international standard and develop its own standards in the course of implementing the national strategies on standardizing public signs. 相似文献
83.
The Humanitarian Engineering initiative, sponsored by the William and Flora Hewlett Foundation, at the Colorado School of Mines, is creating a program that will support engineering students in understanding their responsibility for solving community development problems that exist throughout the world. As part of this effort, data has been collected on faculty and student attitudes using the ‘Community Service Attitudes Scale,” developed and validated by Shiarella, McCarthy, and Tucker. During the fall 2004, 78 students and 34 faculty members responded to this instrument. Statistically significant differences were found between the attitudes of students and faculty, males and females, and among different age groupings with respect to service activities. A general finding was that faculty displayed better attitudes toward community service than the students. 相似文献
84.
85.
水平管路清管过程流动参数变化规律模拟研究 总被引:4,自引:0,他引:4
混输管路清管技术的研究对混输管道的运行管理具有非常重要的意义。在分析清管器清管物理模型的基础上 ,建立清管器的特征参数计算模型、动态数学模型和数值计算方法 ,并进行数值模拟 ,计算出测压点压力随时间变化的数据 ,并把它们与试验数据进行比较 ,得到清管过程中压力的变化规律。通过数学模拟 ,可以计算清管过程中管道的压力分布状况 ,利用压力分布状况就可跟踪清管球在管道内的运行情况 相似文献
86.
87.
氧化物共还原制取W-Cu和Mo-Cu复合材料的研究 总被引:3,自引:0,他引:3
近些年来,国内外研究了一些制备高分散度W/Cu和Mo/Cu复合粉末的方法,高分散度的粉末具有高的烧结致密度,用氧化物共还原粉末可在较低温度下进行烧结得到接近和达到100%的理论密度。这样的复合材料有细而均匀的组织和较好的性能。本文报道近来的研究状况,并就共还原法所用的前驱体原料种类、工艺条件、粉末特性和复合材料的性能进行评述。 相似文献
88.
P. R. Cetlin S. Yue J. J. Jonas T. M. Maccagno 《Metallurgical and Materials Transactions A》1993,24(7):1543-1553
Most laboratory simulations of hot rolling involve a scaling down of the strain rate from the much higher industrial levels.
This leads to slower softening between each rolling pass, for which corrections must be made. In the present work, torsion
testing simulations of “warm” rod rolling were conducted on a Ti-Nb interstitial-free (IF) steel at 840 °C and 770 °C(i.e., in the ferrite range). For this purpose, “strain rate corrected” interpass times were used, in addition to the more familiar
corrections for the stress. The results are compared with those obtained from simulations using uncorrected industrial interpass
times. At 840 °C, simulations using corrected interpass times led to high levels of softening between the stages of rolling,
thus triggering the reinitiation of cycles of dynamic recrystallization. The initially high stress level at the start of these
cycles was responsible for the large differences in the pass-to-pass mean flow stress behavior, compared with that observed
when using uncorrected industrial interpass times, or continuous deformations. The differences were much less pronounced at
770 °C, where the rate of softening is much slower than at 840 °C. Predictions for softening based on the Avrami equation
underestimated the softening observed using the continuous and uncorrected industrial interpass time schedules and overestimated
it for the corrected ones. The former is due to the occurrence of recovery, which is not addressed by the Avrami relation,
while the latter is due to the precipitation that takes place during the corrected (longer) interpass times. It was also found
that simulations using continuous deformations are applicable only if the interpass softening that would be expected using
the corrected interpass times does not exceed about 20 pct. 相似文献
89.
从分析修磨过程运动学和单个磨粒切削入手,建立了磨削深度与磨削过程诸参数(如工艺、材料性能、砂轮性能等)的关系表达式,从而建立起金属切除率与各单项参数的定量关系,为改善或提高修磨效率和修磨过程控制提供了有意义的根据。理论分析与实验结果吻合良好。 相似文献
90.