全文获取类型
收费全文 | 19576篇 |
免费 | 1580篇 |
国内免费 | 757篇 |
专业分类
电工技术 | 556篇 |
综合类 | 1420篇 |
化学工业 | 4131篇 |
金属工艺 | 1042篇 |
机械仪表 | 357篇 |
建筑科学 | 1671篇 |
矿业工程 | 945篇 |
能源动力 | 478篇 |
轻工业 | 3874篇 |
水利工程 | 539篇 |
石油天然气 | 1288篇 |
武器工业 | 45篇 |
无线电 | 743篇 |
一般工业技术 | 1203篇 |
冶金工业 | 1558篇 |
原子能技术 | 111篇 |
自动化技术 | 1952篇 |
出版年
2024年 | 96篇 |
2023年 | 246篇 |
2022年 | 536篇 |
2021年 | 599篇 |
2020年 | 651篇 |
2019年 | 605篇 |
2018年 | 581篇 |
2017年 | 691篇 |
2016年 | 727篇 |
2015年 | 745篇 |
2014年 | 1249篇 |
2013年 | 1324篇 |
2012年 | 1483篇 |
2011年 | 1512篇 |
2010年 | 1099篇 |
2009年 | 1024篇 |
2008年 | 895篇 |
2007年 | 1136篇 |
2006年 | 1014篇 |
2005年 | 876篇 |
2004年 | 847篇 |
2003年 | 707篇 |
2002年 | 554篇 |
2001年 | 443篇 |
2000年 | 402篇 |
1999年 | 317篇 |
1998年 | 255篇 |
1997年 | 203篇 |
1996年 | 185篇 |
1995年 | 177篇 |
1994年 | 142篇 |
1993年 | 108篇 |
1992年 | 91篇 |
1991年 | 75篇 |
1990年 | 52篇 |
1989年 | 45篇 |
1988年 | 39篇 |
1987年 | 26篇 |
1986年 | 24篇 |
1985年 | 24篇 |
1984年 | 16篇 |
1983年 | 7篇 |
1982年 | 16篇 |
1981年 | 13篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1964年 | 4篇 |
1960年 | 3篇 |
1959年 | 3篇 |
1958年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 43 毫秒
41.
刘国华 《湖南工业大学学报》2004,18(4)
邓小平的稳定思想是邓小平理论的重要组成部分,是邓小平在不断总结革命与建设实践经验,继承和发展毛泽东稳定思想的基础上形成的正确思想.从理论渊源、历史沿革、基本内容和主要特征几个方面论述了邓小平的稳定思想. 相似文献
42.
Sensitivity of spectral reflectance to variation in live fuel moisture content at leaf and canopy level 总被引:1,自引:0,他引:1
Wildland fires burn large areas of the earth's land surface annually, causing significant environmental damage and danger to human health. In order to mitigate the effects, and to better manage the incidence of such fires, fire behaviour models are used to predict, among other things, the likelihood of ignition, the rate of spread, and the intensity and duration of burning. A key input parameter to these models is the amount of water in the vegetation, described as the fuel moisture content (FMC). A number of studies have shown that vegetation indices (VI) calculated from red and NIR reflectances may be used to map spatial and temporal variation in FMC in a range of fire-prone environments, with varying degrees of success. Strong empirical relationships may be established between VI and FMC over grasslands, yet over shrublands and forests, the relationships are weaker. If FMC is to be estimated with greater accuracy and consistency than is currently achieved, it is necessary to fully understand the relative contribution that spatial and temporal variation in the various biophysical and geometrical variables make to reflectance variability at the leaf and canopy level.This paper uses a modelling approach to investigate the sensitivity of reflectance data at leaf and canopy level to variation in the biophysical variables that are used to compute FMC. At the leaf level, the results show that the sensitivity of reflectance to variation in leaf water and dry matter content, used to compute FMC, is greatest in the SWIR and NIR, respectively. Variation in FMC has no effect in the visible wavelengths. At the canopy level, the results show that the sensitivity of reflectance to variation in leaf water and dry matter content is heavily dependent upon the type of model used and the range of variation over which the variables are tested. In the longer wavelengths of the SWIR, the competing influence of variable leaf area index, fractional vegetation cover, and solar zenith angle is shown to be greater than that at the shorter wavelengths of the SWIR and NIR. Empirical relationships between the normalised difference water index (NDWI) and FMC are shown to be weaker than that with canopy water content. However, when the range of the variables under study is more limited, useful empirical relationships between FMC and remotely sensed VI may be established. 相似文献
43.
现阶段变压器油纸绝缘等效弛豫机构参数辨识多采用拓扑支路数任意假定、粒子群等智能算法对 N组非线性方程组寻优迭代计算。其计算往往具有收敛性差、结果不唯一等问题,且难以从介质响应函数特性分析真实的油纸绝缘弛豫过程,影响后续弛豫参数对老化评估的准确性。基于此,提出一种应用数学解析法的变压器油纸绝缘弛豫机构参数辨识新方法。首先,从介质响应函数特性出发,深入挖掘弛豫项数信息,辨识油纸绝缘等效弛豫机构的拓扑结构;其次,公式推演得到参数辨识的数学计算公式,避免了智能算法对非线性方程组的寻优误差与不唯一性;最后,通过实例验证该方法的有效性与可行性,提出的数学解析法可为变压器油纸绝缘介质内部弛豫响应特性提供可靠的数学分析模型。 相似文献
44.
在教学实践的基础上,结合工程实践,介绍了定性结构力学的内容体系,包括概念设计、计算模型的建立和简化、估算判断和计算结果的定性分析.并通过工程案例说明定性结构力学的重要意义. 相似文献
45.
严亚菊 《湖南工业职业技术学院学报》2012,(4):127-129
改革后的日语能力测试中,听力部分占总分的比例也由原来的25%提高到30%,而且还增加了最低标准,由此可见,日语听力教学的重要性。文章提出了高职院校日语听力教学过程中产生的问题,并结合实际,创新教学内容,开展互动型教学,重视学生不良情绪的疏导,帮助学生提高日语听力水平,提高教学效果。 相似文献
46.
47.
48.
根据冶金熔体的共存理论,计算了CaO-MgO-MnO-FeO-SiO2-Al2O3六元渣系各组元的作用浓度。结合生产实际数据,建立了LF精炼过程中炉渣成分和钢水[Ca]之间氧化还原反应的数学模型,计算了炉渣成分对钢水[Ca]含量的影响。结果表明,LF精炼过程中钢水[Ca]含量受[Si]-(FeO)联合控制,渣中SiO2、FeO质量分数每增加1%,[Ca]质量分数分别降低1.63×10-6和1.55×10-6。为了将[Ca]质量分数控制在10×10-6以下,当FeO质量分数为3%左右时,碱度B应不高于0.9。 相似文献
49.
50.
Paul G. Skokowski 《Minds and Machines》1994,4(3):333-344
I examine whether it is possible for content relevant to a computer's behavior to be carried without an explicit internal representation. I consider three approaches. First, an example of a chess playing computer carrying emergent content is offered from Dennett. Next I examine Cummins response to this example. Cummins says Dennett's computer executes a rule which is inexplicitly represented. Cummins describes a process wherein a computer interprets explicit rules in its program, implements them to form a chess-playing device, then this device executes the rules in a way that exhibits them inexplicitly. Though this approach is intriguing, I argue that the chess-playing device cannot exist as imagined. The processes of interpretation and implementation produce explicit representations of the content claimed to be inexplicit. Finally, the Chinese Room argument is examined and shown not to save the notion of inexplicit information. This means the strategy of attributing inexplicit content to a computer which is executing a rule, fails.I wish to thank Fred Dretske, JOhn Perry, and an anonymous reviewer for helpful comments and suggestions. Earlier versions of this paper were read at the American Philosophical Association Pacific Division Meeting in San Francisco in March, 1993, and at the 7th International Conference on Computing and Philosophy in Orlando in August, 1992. 相似文献