全文获取类型
收费全文 | 6686篇 |
免费 | 204篇 |
国内免费 | 122篇 |
专业分类
电工技术 | 170篇 |
技术理论 | 1篇 |
综合类 | 317篇 |
化学工业 | 310篇 |
金属工艺 | 195篇 |
机械仪表 | 385篇 |
建筑科学 | 1024篇 |
矿业工程 | 151篇 |
能源动力 | 89篇 |
轻工业 | 302篇 |
水利工程 | 66篇 |
石油天然气 | 176篇 |
武器工业 | 22篇 |
无线电 | 342篇 |
一般工业技术 | 258篇 |
冶金工业 | 2228篇 |
原子能技术 | 38篇 |
自动化技术 | 938篇 |
出版年
2023年 | 25篇 |
2022年 | 44篇 |
2021年 | 81篇 |
2020年 | 115篇 |
2019年 | 113篇 |
2018年 | 59篇 |
2017年 | 59篇 |
2016年 | 109篇 |
2015年 | 140篇 |
2014年 | 212篇 |
2013年 | 229篇 |
2012年 | 473篇 |
2011年 | 609篇 |
2010年 | 499篇 |
2009年 | 599篇 |
2008年 | 437篇 |
2007年 | 258篇 |
2006年 | 285篇 |
2005年 | 289篇 |
2004年 | 177篇 |
2003年 | 319篇 |
2002年 | 410篇 |
2001年 | 200篇 |
2000年 | 94篇 |
1999年 | 106篇 |
1998年 | 60篇 |
1997年 | 36篇 |
1996年 | 47篇 |
1995年 | 35篇 |
1994年 | 43篇 |
1993年 | 32篇 |
1992年 | 36篇 |
1990年 | 40篇 |
1989年 | 42篇 |
1988年 | 36篇 |
1987年 | 37篇 |
1986年 | 51篇 |
1985年 | 43篇 |
1984年 | 31篇 |
1983年 | 30篇 |
1982年 | 19篇 |
1981年 | 34篇 |
1980年 | 21篇 |
1979年 | 25篇 |
1976年 | 17篇 |
1975年 | 20篇 |
1966年 | 26篇 |
1965年 | 25篇 |
1964年 | 17篇 |
1962年 | 59篇 |
排序方式: 共有7012条查询结果,搜索用时 15 毫秒
1.
Marion Börnhorst Jens Friedland Bjarne Kreitz Emanuele Moioli Gregor Wehinger 《化学,工程师,技术》2021,93(8):1210-1213
In this article, the results of the NaWuReT (Early Career Reaction Engineers) workshop on the topic “Are we doing relevant science?” are presented. The topics “(In)surmountable hurdles for Citizen Scientists in reaction engineering?” and “Circular Economy in reaction engineering with/for society?” were discussed. Therefrom, a variety of ideas and suggestions were extracted. 相似文献
2.
大气温室气体柱浓度地基遥感观测是碳监测卫星验证和校正的有效手段,目前主要依赖于昂贵且移动困难的高分辨率傅里叶变换红外光谱仪(120/125 HR)。采用便携式较低光谱分辨率(0.5cm-1)傅里叶变换红外光谱仪(EM27/SUN)进行温室气体柱浓度的监测提供了一种新型的便捷手段。EM27/SUN通过自带的太阳跟踪器记录太阳直射辐射光谱,根据温室气体在短波红外波段存在明显吸收线的原理,利用非线性最小二乘算法PROFFIT和GGG反演柱气体平均干空气摩尔分数Xgas。通过高精度反演算法反演后得到的数据具有较高精度和高稳定度,具备进行科学应用的条件。EM27/SUN在国际上的科学应用主要总结为3类:烟羽成分浓度测量、卫星验证以及城市尺度源汇估算。重点讨论了EM27/SUN相比于其他观测手段的优势及带来的创新性结果。展望了未来EM27/SUN可以用于国内外各种特殊点的气体羽流分析、卫星数据验证和城市源汇分析工作,还可以用于不同TCCON站点的传递定标。 相似文献
3.
《Contact lens & anterior eye》2022,45(4):101484
PurposeTo investigate the repeatability and reproducibility of choroidal thickness measurements using Lenstar images in young myopic children before and after one-month orthokeratology (ortho-k) treatment.MethodOcular biometry of 39 subjects were performed using the Lenstar 900. The first five measurements with maximum differences of 0.02 mm in axial length in the right eyes were saved and used for measurement of choroidal thickness. Subfoveal choroidal thickness were manually measured by identifying the signals from the retinal pigmented epithelium layer and chorioscleral interface. Repeatability was determined by comparing measurements of the same images made by the same observer on two separate occasions (four weeks apart), while reproducibility was calculated by comparing measurements of the same images made by two independent observers. Data was analysed using intra-class correlation coefficients (ICC) and non-parametric Bland and Altman plots.ResultsThe choroidal peaks could not be identified in all five measurements in all subjects. On average, only 71% subjects had at least four definable images. Compared with the use of fewer than four images, reliability using an average of four definable images improved statistically, but remained clinically unacceptable (>10 µm), although pre- and post-ortho-k ICC values were good to excellent for repeatability (0.867 and 0.975, respectively) and excellent and good for reproducibility (0.959 and 0.868, respectively). Non-parametric pre- and post-ortho-k limits of agreement (2.5% and 97.5% percentiles) obtained were ?45.8 to 79.3 µm and ?30.3 to 9.5 µm, respectively for repeatability, and ?29.0 to 33.5 µm and ?21.8 to 70.0 µm, respectively for reproducibility.ConclusionChoroidal thickness measurements using the Lenstar did not show good reliability, despite the high ICC values, non-parametric Bland and Altman plots demonstrated a wide variability of measurement errors. Any changes in subfoveal choroidal thickness, measured by Lenstar, of <80 µm may not represent real changes. 相似文献
4.
5.
R-test测量仪是用于五轴数控机床转动轴结构误差测量的专用设备,其通过测量球相对测量坐标系的位置变化进行误差辨识。在测量坐标系中,测量球球心坐标计算的准确性和稳定性是保证测量精度的重要前提。为进行测量球球心坐标的精确计算,构建了非接触式R-test测量仪的结构模型并建立了球心坐标计算方程组。以球心坐标计算方程组为基础,简化得到用于球心坐标求解的非线性方程组并构建其目标函数,然后采用差分进化算法提高球心坐标求解的精度。最后,在GF Mikron UCP800五轴机床上进行对比实验,将测量球球心坐标的计算结果与机床实际坐标进行对比,验证所提出球心坐标计算方法的精度和可靠性。 相似文献
6.
刘畅智 《安徽冶金科技职业学院学报》2021,31(1):106-108
科技在不断发展,时代在不断进步,新时代高校基层组织所面临的挑战也在不断的改变。为了在新时代背景下更好的应对这些变化,为了让广大青年学生可以健康成长,建立和谐校园,要对新时代的各类挑战加以研究。作为基层团组织工作参与者,要加强工作引领,在与时俱进的同时加强各方面的渠道宣传。要对新时代高校基层组织团组织工作进行研究,发现问题、分析问题并解决问题。 相似文献
7.
In this work, the effects of support surface pore structures(including surface pore size, surface pore density and surface porosity) on the performance of thin film composite(TFC) gas separation membrane over a wide pressure range(from 0.3 to 2.0 MPa) were studied. To fulfill it, the polysulfone(PSf) supports with different surface pore structures were prepared. Two kinds of wide-accepted polymeric membrane materials, i.e., polyvinylamine(PVAm) and Pebax 1657 copolymer, were used as skin layer materials. We pointed out for the first time that the support surface average pore size and pore density could affect the chain mobility of polymer of skin layer at the support surface pore entrance, then, can affect the TFC membrane performance. Besides, we also discussed the effects of support on the TFC membrane performance when the feed pressure changes for the first time. This work can provide guidance for choosing a suitable support for TFC gas separation membrane. 相似文献
8.
In recent years, metabolic engineering has made great progress in both academic research and industrial applications. However, we have not found any articles that specifically analyze the current state of metabolic engineering in China in comparison with other countries. Here, we review the current development and future trends of global metabolic engineering, conduct an in-depth benchmarking analysis of the development situation of China’s metabolic engineering, and identify current problems as well as future trends. We searched publications in the Scopus database from 2015 to September 2020 in the field of metabolic engineering, and analyzed the output in general, including publication trends, research distribution, popular journals, hot topics and vital institutions, but also analyzed the share of citations, field-weighted citation impact, and production in collaboration with strategic countries in science and technology. This study aims to serve as a reference for later studies, offering a comprehensive view of China’s contribution to metabolic engineering, and as a tool for the elaboration of national public policy in science and technology. 相似文献
9.
10.
大数据背景下,财务共享技术成为各行各业财务管理发展的新方向,为了验证财务共享技术应用于医院财务管理的优势,此次研究将设计出一种财务共享服务中心,并利用该共享服务中心优化医院财务管理流程,比较优化前后的财务管理各方面的差异。研究结果表明,基于财务共享模式的医院财务管理中,会计成本、报销成本、工资成本、资金预算成本依次降低55%、40%、35%、35%;客户满意度提升幅度为25%,后台运营成本降低了54%;会计核算效率和会计信息的信息准确度提高,漏报率与误报率降低。说明医院可通过财务共享模式的应用,提高医院财务管理效率,降低投入成本。希望本次研究的结果能为医院财务管理的发展提供参考。 相似文献