全文获取类型
收费全文 | 26658篇 |
免费 | 2844篇 |
国内免费 | 1308篇 |
专业分类
电工技术 | 9067篇 |
综合类 | 2379篇 |
化学工业 | 1193篇 |
金属工艺 | 1162篇 |
机械仪表 | 1846篇 |
建筑科学 | 2791篇 |
矿业工程 | 742篇 |
能源动力 | 645篇 |
轻工业 | 678篇 |
水利工程 | 647篇 |
石油天然气 | 618篇 |
武器工业 | 159篇 |
无线电 | 2957篇 |
一般工业技术 | 1546篇 |
冶金工业 | 950篇 |
原子能技术 | 227篇 |
自动化技术 | 3203篇 |
出版年
2024年 | 53篇 |
2023年 | 231篇 |
2022年 | 464篇 |
2021年 | 615篇 |
2020年 | 745篇 |
2019年 | 504篇 |
2018年 | 510篇 |
2017年 | 670篇 |
2016年 | 729篇 |
2015年 | 967篇 |
2014年 | 1953篇 |
2013年 | 1591篇 |
2012年 | 2217篇 |
2011年 | 2282篇 |
2010年 | 1843篇 |
2009年 | 1802篇 |
2008年 | 1711篇 |
2007年 | 1913篇 |
2006年 | 1633篇 |
2005年 | 1387篇 |
2004年 | 1133篇 |
2003年 | 1046篇 |
2002年 | 877篇 |
2001年 | 816篇 |
2000年 | 609篇 |
1999年 | 578篇 |
1998年 | 391篇 |
1997年 | 321篇 |
1996年 | 281篇 |
1995年 | 215篇 |
1994年 | 153篇 |
1993年 | 122篇 |
1992年 | 104篇 |
1991年 | 77篇 |
1990年 | 56篇 |
1989年 | 58篇 |
1988年 | 50篇 |
1987年 | 18篇 |
1986年 | 21篇 |
1985年 | 19篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1975年 | 2篇 |
1963年 | 2篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
101.
介绍了集随动系统在线监测与故障诊断于一体的智能系统。利用基于知识的诊断推理技术与神经网络技术相结合的方法构建了随动系统在线故障诊断专家系统,使得神经网络推理与基于符号的知识诊断控制、解释有机地结合起来,取长补短,大大提高了系统的工作效率和诊断可靠性。 相似文献
102.
对传统双曲线极尖的四极透镜进行了磁性能分析。在此基础上,提出了极尖断面为折线的四极透镜结构。磁场的数值分析以及测量结果表明:该结构产生的场梯度均匀,且具有磁场集中、磁场梯度高、便于加工和安装的对称性控制等优点。该结构的四极透镜已用于CYCIAE-30回旋加速器和HI-13串列加速器束流输运线之中 相似文献
103.
Stephen Dain 《Color research and application》2007,32(6):428-432
There are anecdotal reports of color vision deficient medical practitioners (particularly deuteranopes) having difficulty in recognizing cyanosis. An understanding of the color changes in oxygenated blood has led to a better understanding of the lighting needs for hospitals. Using the same database, this article investigates the propensity for color vision deficient observers to make mistakes with cyanotic patients. The possibilities for helping the observer with appropriate color of lighting are considered. The spectral reflectances of blood at varying oxygenation levels previously reported were used 7 ; 8 to calculate chromaticity and lightness. The direction of the chromaticity change was compared with the protanopic and deuteranopic confusion lines. An attempt was made to identify sources that enhanced color changes for the color deficient. The color change of blood oxygenation is closely aligned with the confusion lines of congenital dichromats (particularly protanopia) showing the potential for difficulty in making this decision. No source could be demonstrated to solve the problem or even reduce it significantly. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 428–432, 2007 相似文献
104.
提出了一种利用零序与正负序之和的相对相位关系选相新原理。该原理通过零序与正负序之和的相对相位关系,并结合零序与负序相对相位关系进行接地故障相别的判断。该选相元件从原理上克服了以往序分量选相方法受过渡电阻影响较大的缺点,原理简单,理论分析和大量的现场数据验证表明能有效可靠地选出故障相别,是高压线路保护实现单相重合闸较为理想的选相元件。 相似文献
105.
On‐Line Detection Of State‐Of‐Charge In Lead Acid Battery Using Radial Basis Function Neural Network
To realize a stable supply of electric power in an automobile, an accurate and reliable detection method of SOC (state‐of‐charge) in a lead acid battery is required. However the dynamics of the battery is very complicated. The characteristics of the battery greatly change due to its degradation. Moreover a automobile has many driving patterns, which are unknown beforehand. Thus it is not easy to detect the SOC analytically. In this paper, to overcome this problem, a new on‐line SOC detection method with a radial basis function neural network is proposed. In order to increase the detection accuracy of degraded batteries, physical values related to the degradation degree are used as input signal in the neural network. The detection accuracies for different sized batteries and various degradation states are investigated. 相似文献
106.
某跨线桥施工支架方案设计 总被引:1,自引:0,他引:1
结合某大桥的概况,根据梁体施工工艺要求、现场实地勘察情况确定跨线施工方案,支架采用布架灵活、搭拆方便、承载力大的WDJ碗扣式多功能钢支架,部分预应力现浇连续箱梁采用支墩加纵梁预留门洞的支架现浇,取得良好效果。 相似文献
107.
108.
109.
110.
Calcining of the mixture of BaCO3 and TiO2 with a ratio 1:4 at different temperatures was carried out to synthesize BaTi4O9 powders. Phase evolution of the samples was studied using the differential thermal analysis (DTA) and X-ray diffractometry
(XRD). Both techniques confirmed that the formation of BaTi4O9 started around 1000 °C. The XRD peaks showed that BaTi4O9 was most pronounced at 1250 °C. X-ray line broadening methods were employed to study the variation of particle size and microstrain
of the BaTi4O9 powders. The Voigt function in a single line and the pseudo-Voigt function in the variance methods were used in our case.
We found that both functions resulted in the same trends, i.e., the particle size increased with the temperature with the
biggest size of 180 and 160 nm, whilst the microstrain yielded the opposite trend with the lowest values of 6.2 × 10–3 and 1.1 × 10–3. The scanning electron microscopy (SEM) study revealed the size of the large particles formed, due to agglomeration, to be
about 0.5–1.9 μm. Furthermore, it was shown that irregular shapes of BaTi4O9 powders necked to each other appeared at 1000 °C and grew into ellipse and rod shapes at 1250 °C.
Electronic Publication 相似文献