全文获取类型
收费全文 | 2646篇 |
免费 | 327篇 |
国内免费 | 33篇 |
专业分类
化学 | 188篇 |
晶体学 | 1篇 |
力学 | 149篇 |
综合类 | 32篇 |
数学 | 156篇 |
物理学 | 239篇 |
无线电 | 2241篇 |
出版年
2024年 | 13篇 |
2023年 | 35篇 |
2022年 | 90篇 |
2021年 | 126篇 |
2020年 | 159篇 |
2019年 | 64篇 |
2018年 | 78篇 |
2017年 | 103篇 |
2016年 | 146篇 |
2015年 | 156篇 |
2014年 | 273篇 |
2013年 | 206篇 |
2012年 | 251篇 |
2011年 | 233篇 |
2010年 | 128篇 |
2009年 | 127篇 |
2008年 | 133篇 |
2007年 | 120篇 |
2006年 | 105篇 |
2005年 | 112篇 |
2004年 | 76篇 |
2003年 | 71篇 |
2002年 | 31篇 |
2001年 | 23篇 |
2000年 | 28篇 |
1999年 | 18篇 |
1998年 | 14篇 |
1997年 | 13篇 |
1996年 | 9篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有3006条查询结果,搜索用时 31 毫秒
31.
Eun Jeong ChoFrank V Bright 《Analytica chimica acta》2002,470(1):101-110
We report a new, solid-state, integrated optical array sensor platform. By using pin printing technology in concert with sol-gel-processing methods, we form discrete xerogel-based microsensor elements that are on the order of 100 μm in diameter and 1 μm thick directly on the face of a light emitting diode (LED). The LED serves as the light source to excite chemically responsive luminophores sequestered within the doped xerogel microsensors and the analyte-dependent emission from within the doped xerogel is detected with a charge coupled device (CCD). We overcome the problem of background illumination from the LED reaching the CCD and the associated biasing that results by coating the LED first with a thin layer of blue paint. The thin paint layer serves as an optical filter, knocking out the LEDs red-edge spectral tail. The problem of the spatially-dependent fluence across the LED face is solved entirely by performing ratiometric measurements. We illustrate the performance of the new sensor scheme by forming an array of 100 discrete O2-responsive sensing elements on the face of a single LED. The combination of pin printing with an integrated sensor and light source platform results in a rapid method of forming (∼1 s per sensor element) reusable sensor arrays. The entire sensor array can be calibrated using just one sensor element. Array-to-array reproducibly is <8%. Arrays can be formed using single or multiple pins with indistinguishable analytical performance. 相似文献
32.
为了解决电子商务平台发展应用与分销商之间的利益问题,采用TRIZ理论的理想解分析方法以及商业冲突矩阵,对此进行了分析阐述。最终给出可行的发明原理及原理所对应的解决方案。进一步验证了TRIZ理论在商业管理中应用的可行性。 相似文献
33.
文中首先阐述和分析了交互式设计的含义及重要性,然后介绍了在互联网上实现交互式业务的具体开发流程,以及如何从目标用户的需求和期望出发,结合人类本身的心理特征和行为特点,用最简单的方法创建易用、有效而且让用户愉悦的设计。 相似文献
34.
35.
Ray Nichol Jim Robinson 《International Journal of Mathematical Education in Science & Technology》2013,44(4):495-504
After the invasion and occupation of their land by Europeans, Indigenous Australians were expected to benefit from a Western education system based on that of the dominant Europeans. Gradually educators realized that Aboriginal children learn differently and that Indigenous culture and pedagogy has validity and strength. Of course, educators also need to be acutely aware of the diversity of Indigenous cultures in Australia and that there is not a monolithic sense of Aboriginal identity or Aboriginal pedagogy. Dispossession and alienation, poor health and few employment opportunities must also affect educational interest, attendance, application and performance. In this paper the characteristics of Indigenous learners are examined and pedagogical strategies to assist in both students' learning and teachers' delivery are explored. The message conveyed in this paper has particular relevance for teaching mathematics to Aboriginal learners. It is also of considerable value in teaching mathematics to nonAboriginal students, in Australia and elsewhere. 相似文献
36.
林建宗 《数学的实践与认识》2016,(19):62-73
在线声誉机制是网购平台重要的信号机制,是平台可持续成长的基础.从理论基础、研究假设、数据来源、变量选择、模型应用等方面,全面梳理了在线声誉机制作用的实证研究方法,包括Hedonic回归、Logit、Probit、Poisson、Tobit、截取正态回归、样本选择回归、固定效应、广义最小二乘法等模型的应用.最后展望未来相关研究及方法,并构建在线声誉机制作用的实证研究综合框架. 相似文献
37.
The hydrothermal treatment of sugars features a promising technology for the production of fine and platform chemicals from renewable resources. In this work the hydrothermal decomposition of fructose was studied in a buffered medium at a pH range between 2.2 and 8.0. It is demonstrated that at lower pH values mainly 5-hydroxymethylfurfural (HMF), levulinic acid and humin are generated, while lactic acid and acetic acid are produced at higher pH values. The work shows that the use of moderate acidic conditions may have advantages for the hydrothermal HMF production over the use of strongly acidic conditions, as especially the degradation into levulinic acid is suppressed. Besides, this study deals with a rather complex reaction network, hence limitations and need for adaption of the kinetic model are discussed. 相似文献
38.
39.
为满足信息化处理需求的增长,提出MPI在云计算领域的应用研究。文章在介绍了云计算的优势、MPI概念的基础上,将MPI并行程序与并行机群系统及云计算平台整合在一起,借助Hadoop框架,充分利用MapReduce模式来实现并行化云计算对应的MPI算法。研究结果分析表明,该算法是可行的,可有效提高MPI并行处理的性能。 相似文献
40.
在特定的边界下美军“强盗”电子情报系统具备强大的单站定位能力。通过分析“强盗”系统,提出了一种独特的定位技术。有别于传统定位技术,该技术利用雷达杂波信号实现对辐射源的定位,理论分析和仿真结果证明了其可行性。 相似文献