全文获取类型
收费全文 | 9351篇 |
免费 | 1741篇 |
国内免费 | 946篇 |
专业分类
电工技术 | 1218篇 |
技术理论 | 2篇 |
综合类 | 1026篇 |
化学工业 | 170篇 |
金属工艺 | 134篇 |
机械仪表 | 916篇 |
建筑科学 | 481篇 |
矿业工程 | 484篇 |
能源动力 | 122篇 |
轻工业 | 82篇 |
水利工程 | 566篇 |
石油天然气 | 216篇 |
武器工业 | 73篇 |
无线电 | 2011篇 |
一般工业技术 | 362篇 |
冶金工业 | 161篇 |
原子能技术 | 76篇 |
自动化技术 | 3938篇 |
出版年
2025年 | 1篇 |
2024年 | 175篇 |
2023年 | 191篇 |
2022年 | 294篇 |
2021年 | 359篇 |
2020年 | 345篇 |
2019年 | 267篇 |
2018年 | 250篇 |
2017年 | 342篇 |
2016年 | 351篇 |
2015年 | 460篇 |
2014年 | 727篇 |
2013年 | 703篇 |
2012年 | 906篇 |
2011年 | 889篇 |
2010年 | 658篇 |
2009年 | 589篇 |
2008年 | 640篇 |
2007年 | 707篇 |
2006年 | 663篇 |
2005年 | 562篇 |
2004年 | 462篇 |
2003年 | 397篇 |
2002年 | 262篇 |
2001年 | 199篇 |
2000年 | 165篇 |
1999年 | 101篇 |
1998年 | 86篇 |
1997年 | 61篇 |
1996年 | 49篇 |
1995年 | 34篇 |
1994年 | 26篇 |
1993年 | 19篇 |
1992年 | 23篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 1篇 |
1986年 | 18篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 2篇 |
1964年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
本文介绍了一种先进的楼宇自控系统,它不仅监控了大量的楼宇机电设备,还可以与第三方控制系统进行接口。更为可贵的是,本系统可以通过电话进行远程控制。 相似文献
943.
944.
945.
在现代企业中实现远程监测与控制的Web化 总被引:16,自引:2,他引:16
文章在介绍ISAPI和SOCKET编程的基础上,详细介绍了如何基于INTERNET技术,在现代企业中实现远程监测与控制的WEB化。 相似文献
946.
Comparison of land surface emissivity and radiometric temperature derived from MODIS and ASTER sensors 总被引:1,自引:0,他引:1
Frédéric Jacob Franc?ois Petitcolin Éric Vermote Kenta Ogawa 《Remote sensing of environment》2004,90(2):137-152
This study compared surface emissivity and radiometric temperature retrievals derived from data collected with the MODerate resolution Imaging Spectroradiometer (MODIS) and Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER) sensors, onboard the NASA's Earth Observation System (EOS)-TERRA satellite. Two study sites were selected: a semi-arid area located in northern Chihuahuan desert, USA, and a Savannah landscape located in central Africa. Atmospheric corrections were performed using the MODTRAN 4 atmospheric radiative transfer code along with atmospheric profiles generated by the National Center for Environmental Predictions (NCEP). Atmospheric radiative properties were derived from MODTRAN 4 calculations according to the sensor swaths, which yielded different strategies from one sensor to the other. The MODIS estimates were then computed using a designed Temperature-Independent Spectral Indices of Emissivity (TISIE) method. The ASTER estimates were derived using the Temperature Emissivity Separation (TES) algorithm. The MODIS and ASTER radiometric temperature retrievals were in good agreement when the atmospheric corrections were similar, with differences lower than 0.9 K. The emissivity estimates were compared for MODIS/ASTER matching bands at 8.5 and 11 μm. It was shown that the retrievals agreed well, with RMSD ranging from 0.005 to 0.015, and biases ranging from −0.01 to 0.005. At 8.5 μm, the ranges of emissivities from both sensors were very similar. At 11 μm, however, the ranges of MODIS values were broader than those of the ASTER estimates. The larger MODIS values were ascribed to the gray body problem of the TES algorithm, whereas the lower MODIS values were not consistent with field references. Finally, we assessed the combined effects of spatial variability and sensor resolution. It was shown that for the study areas we considered, these effects were not critical. 相似文献
947.
Satellite radar remote sensing of seasonal growing seasons for boreal and subalpine evergreen forests 总被引:2,自引:0,他引:2
John S. Kimball Kyle C. McDonald Steve E. Frolking 《Remote sensing of environment》2004,90(2):243-258
We evaluated whether satellite radar remote sensing of landscape seasonal freeze-thaw cycles provides an effective measure of active growing season timing and duration for boreal and subalpine evergreen forests. Landscape daily radar backscatter measurements from the SeaWinds scatterometer on-board the QuikSCAT satellite were evaluated across a regional network of North American coniferous forest sites for 2000 and 2001. Radar remote sensing measurements of the initiation and length of the growing season corresponded closely with both site measurements and ecosystem process model (BIOME-BGC) simulations of these parameters because of the sensitivity of the Ku-band scatterometer to snow cover freeze-thaw dynamics and associated linkages between growing season initiation and the timing of seasonal snowmelt. In contrast, remote sensing estimates of the timing of growing season termination were either weakly or not significantly associated with site measurements and model simulation results, due to the relative importance of light availability and other environmental controls on stand phenology in the fall. Regional patterns of estimated annual net primary production (NPP) and component photosynthetic and autotrophic respiration rates for the evergreen forest sites also corresponded favorably with remote sensing estimates of the seasonal timing of spring thaw and associated growing season length, indicating the importance of these parameters in determining spatial and temporal patterns of NPP and the potential utility of satellite radar remote sensing for regional monitoring of the terrestrial biosphere. 相似文献
948.
随着高铁运营速度的不断提高,对高速列车进行长期的实时监测,有利于保障列车的行车安全.在明确监测需求的基础上,开发出基于LabVIEW的高速列车车下设备舱远程监测系统.系统以LabVIEW软件为编程平台,以NI CompactRIO硬件结构体系为载体,选择可重复配置的FPGA数据采集模块进行数据采集,数据传输采用DMA FIFO方法,实现了车下设备舱关键受力部位吊架和支座数据的高速采集、实时显示、远程传输等功能.通过远程监测系统对采集的数据进行实时查看,可以实时掌握列车的运行状态,对维护列车运行的安全性和稳定性具有重要意义. 相似文献
949.
高光谱图像监督分类中,为了避免休斯效应需要大量的训练样本,但在实际应用中对样本进行标注成本非常高,因此,得到高质量的训练样本显得十分重要。提出一种基于主动学习的高光谱图像分类方法,通过对区域关注度的统计,有效地结合图像光谱和空间特性,基于主动学习方法获取信息量较大的训练样本,从而较大幅度提高了分类的精确度。实验结果表明,所提算法比传统的随机取样监督分类法和主动学习方法在分类精确度上有较大的优势。 相似文献
950.
土壤水分是监测作物旱情的基本因子,以欧空局1978~2014年微波遥感土壤水分产品、中国经济与社会发展统计数据库以及气象数据为基础,结合土壤水分亏缺指数(Soil Water Deficit Index, SWDI)分析东北地区的干旱程度与玉米亩产的关系。结果表明:①东北三省干旱程度空间上呈现自东北向西南逐渐加重的空间分布模式;②基于CCI (Climate Change Initiative)土壤水分产品计算的SWDI干旱指数与降雨量和气温有良好的相关关系,可用于评估干旱发生的严重程度;③玉米生长季关键需水期——7月的SWDI与玉米产量的相关性最好,二者在黑龙江、吉林和辽宁省的R2分别为0.43、0.78和0.38,非常适合用于评估干旱对玉米单产的影响。该结论对于研究大范围土壤水分含量对农作物产量的影响以及相关农业决策具有重要指导意义。 相似文献