全文获取类型
收费全文 | 30449篇 |
免费 | 1745篇 |
国内免费 | 1175篇 |
专业分类
电工技术 | 1182篇 |
综合类 | 2562篇 |
化学工业 | 4203篇 |
金属工艺 | 2105篇 |
机械仪表 | 3071篇 |
建筑科学 | 2524篇 |
矿业工程 | 959篇 |
能源动力 | 1439篇 |
轻工业 | 1037篇 |
水利工程 | 885篇 |
石油天然气 | 1580篇 |
武器工业 | 526篇 |
无线电 | 1758篇 |
一般工业技术 | 2242篇 |
冶金工业 | 1272篇 |
原子能技术 | 542篇 |
自动化技术 | 5482篇 |
出版年
2024年 | 59篇 |
2023年 | 231篇 |
2022年 | 452篇 |
2021年 | 621篇 |
2020年 | 646篇 |
2019年 | 522篇 |
2018年 | 528篇 |
2017年 | 742篇 |
2016年 | 834篇 |
2015年 | 1140篇 |
2014年 | 1724篇 |
2013年 | 1653篇 |
2012年 | 2030篇 |
2011年 | 2563篇 |
2010年 | 1778篇 |
2009年 | 1896篇 |
2008年 | 1784篇 |
2007年 | 2337篇 |
2006年 | 2147篇 |
2005年 | 1872篇 |
2004年 | 1525篇 |
2003年 | 1381篇 |
2002年 | 987篇 |
2001年 | 765篇 |
2000年 | 620篇 |
1999年 | 469篇 |
1998年 | 399篇 |
1997年 | 289篇 |
1996年 | 265篇 |
1995年 | 203篇 |
1994年 | 180篇 |
1993年 | 127篇 |
1992年 | 105篇 |
1991年 | 104篇 |
1990年 | 64篇 |
1989年 | 66篇 |
1988年 | 45篇 |
1987年 | 23篇 |
1986年 | 21篇 |
1985年 | 26篇 |
1984年 | 21篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1976年 | 13篇 |
1975年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
采用二次回归正交设计进行烧结试验,获得了七个目标的数学模型,并验证了其可靠性,用多目标计算机选优法对四烧车间的工艺参数进行了选优。 相似文献
83.
分析和总结了飞机各种机动动作的内在因素,提出了目标机动规范模型,研究了模型的数学描述方式、控制参量的相互约束关系及其组织形式,并通过模拟导弹对目标的攻击过程对模型进行了验证。 相似文献
84.
对WQ-10型煤气平焰烧嘴进行半工业性试验,得到了该烧嘴较长时间运行下的一些性能。结果表明,该烧嘴平火焰稳定,炉顶温度分布均匀,燃烧烟气中CO、NO含量达到了YB/T062-94标准的要求。 相似文献
85.
We have studied the CO2/CH4 mixed gas permeation through hollow fiber membranes in a permeator. An approach to characterize the true separation performance of hollow fiber membranes for binary gas mixtures was provided based on experiments and simulations. Experiments were carried out to measure the retentate and permeate flow rates and compositions at each outlet. The influences of pressure drop within the hollow fibers, non-ideal gas behavior in the mixture and concentration polarization were taken into consideration in the mathematics model. The calculation results indicate that the net influence of the non-ideal gas behavior, competitive sorption and plasticization yields the calculated CO2 permeance in a mixed gas permeator close to that obtained in pure gas tests. Whereas the CH4 permeance is higher in the mixed gas tests than that in the pure gas tests, as the plasticization caused by CO2 dominates the permeation process. As a result, the CO2/CH4 mixed gas selectivity is smaller than those obtained in pure gas tests at equivalent pressures.The calculated membrane performance shows little changes with stage cut if the effect of concentration polarization is accounted for in the calculation. The integration method developed in this study could provide more accurate characterizations of mixed gas permeance of hollow membranes than other estimation methods, as our model considers the roles of non-ideal gas behavior and concentration polarization properly. 相似文献
86.
Richard D. Dick William L. Fourney Deborah J. Goodings Chaun‐Ping Lin Leonhard E. Bernold 《Canadian Metallurgical Quarterly》1992,5(1):59-69
The utilization of explosives for excavation on the lunar surface is under serious consideration as a part of the design for construction of temporary and permanent bases. An excavation research program has shown that small‐scale explosives blasting in a lunar‐soil simulant will greatly reduce the digging forces required for scoop and dragline excavators. Some crater‐blasting parameters were determined for the lunar soil simulant at one Earth gravity and at 10 Earth gravities using a centrifuge. The size of the craters produced at 10 Earth gs matched those formed at one earth g by scaling according to the weight of the explosive. These data can be applied to explosive‐excavation problems such as habitat construction, burial of nuclear power sources, and the rapid construction of shelters remote from the main base to shield against solar‐flare activity. 相似文献
87.
换热网络的数值模拟在换热网络的定量分析中起着重要作用。但在模拟计算中,有时表现出数值稳定性差。提高数值稳定性的方法,目前多通过改善算法来实现。本文通过对换热网络数值模拟的误差分析,提出了误差放大因子的概念,并依此选择迭代变量。通过对迭代变量的选择,达到提高换热网络数值模拟稳定性的目的。 相似文献
88.
89.
This study examines the comfort criteria of ASHRAE Standard 55-2004 for their applicability in hospital environments. Through an extensive field survey conducted in a university hospital in Taiwan, 927 sets of data have been collected. Above half of the measured samples failed to meet the specifications of Standard 55 comfort zone due to improper humidity control. Acceptability votes by patients exceeded the Standard's 80% criterion, regardless of whether the physical conditions were in or out of the comfort zone. Thermal neutrality, preference and comfort range are compared with other studies conducted in office environments and Standard 55 criteria. Results of chi-square tests revealed that patients’ physical strength significantly effected their thermal requirements. The net effect of health yields a marked difference in thermal neutrality and preference, and also in the comfortable temperature range. 相似文献
90.
Gamma distributions are some of the most popular models for hydrological processes. In this paper, a very flexible family which contains the gamma distribution as a particular case is introduced. Evidence of flexibility is shown by examining the shape of its probability density function (pdf). A treatment of the mathematical properties is provided by deriving expressions for the n th moment. Estimation and simulation issues are also considered. Finally, a detailed application to drought data from the State of Nebraska is illustrated. 相似文献