全文获取类型
收费全文 | 100342篇 |
免费 | 13283篇 |
国内免费 | 8750篇 |
专业分类
电工技术 | 15001篇 |
技术理论 | 10篇 |
综合类 | 10806篇 |
化学工业 | 6953篇 |
金属工艺 | 2029篇 |
机械仪表 | 5557篇 |
建筑科学 | 5904篇 |
矿业工程 | 2963篇 |
能源动力 | 2665篇 |
轻工业 | 2214篇 |
水利工程 | 3009篇 |
石油天然气 | 5602篇 |
武器工业 | 1250篇 |
无线电 | 12610篇 |
一般工业技术 | 6426篇 |
冶金工业 | 2732篇 |
原子能技术 | 1622篇 |
自动化技术 | 35022篇 |
出版年
2024年 | 480篇 |
2023年 | 1425篇 |
2022年 | 2955篇 |
2021年 | 3642篇 |
2020年 | 3891篇 |
2019年 | 3177篇 |
2018年 | 2931篇 |
2017年 | 3618篇 |
2016年 | 3903篇 |
2015年 | 4355篇 |
2014年 | 6715篇 |
2013年 | 6563篇 |
2012年 | 7391篇 |
2011年 | 7876篇 |
2010年 | 5913篇 |
2009年 | 6058篇 |
2008年 | 6384篇 |
2007年 | 7228篇 |
2006年 | 6323篇 |
2005年 | 5456篇 |
2004年 | 4767篇 |
2003年 | 4056篇 |
2002年 | 3202篇 |
2001年 | 2503篇 |
2000年 | 2143篇 |
1999年 | 1678篇 |
1998年 | 1332篇 |
1997年 | 1081篇 |
1996年 | 907篇 |
1995年 | 814篇 |
1994年 | 728篇 |
1993年 | 509篇 |
1992年 | 381篇 |
1991年 | 360篇 |
1990年 | 285篇 |
1989年 | 239篇 |
1988年 | 183篇 |
1987年 | 138篇 |
1986年 | 109篇 |
1985年 | 132篇 |
1984年 | 90篇 |
1983年 | 93篇 |
1982年 | 88篇 |
1981年 | 44篇 |
1980年 | 33篇 |
1979年 | 40篇 |
1978年 | 14篇 |
1977年 | 25篇 |
1976年 | 17篇 |
1959年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
黄浦江为感潮河流,低潮位重现期的确定对黄浦江航道的设计具有重要意义。为了准确估计黄浦江低潮位的重现期,以黄浦江下游吴淞口站年最低潮位序列为例,在对样本进行三性审查的基础上,分别采用传统的数理统计方法和时变矩方法进行水文频率分析。结果表明:吴淞口站年最低潮位序列在1996年发生了变异;还现修正后的序列服从位置参数线性时变的GEV模型,低潮位存在缓慢的上升趋势;一致性条件下百年一遇低潮位约为0.261 m,在非一致性条件下其重现期增大为150 a。非一致性条件下的重现期增大说明黄浦江现有的航道设计标准偏安全,航道通航保证率提高。 相似文献
52.
带有传感器的可穿戴式医疗设备不断生成大量数据,由于数据的复杂性,难以通过处理和分析大数据来找到有价值的决策信息。为了解决这个问题,提出了一种新的物联网体系结构,用于存储和处理医疗应用的可扩展传感器数据(大数据)。所提出的架构主要由两个子架构组成:Meta Fog重定向(MF-R)架构和AWS密钥管理机制。MF-R架构使用Apache Pig和Apache HBase等大数据技术来收集和存储不同传感器设备生成的传感器数据,并利用卡尔曼滤波消除噪声。AWS密钥管理机制使用密钥管理方案,目的是保护云中的数据,防止未经授权的访问。当数据存储在云中时,所提出的系统能够使用随机梯度下降算法和逻辑回归来开发心脏病的预测模型。仿真实验表明,和其他几种算法相比,提出的算法具有更小的误差,且在吞吐量、准确度等方面具有一定的优越性。 相似文献
53.
Marcus Heinze Sandra Starke Marcel Händler Hartmut Komber Marco Drache Norbert Moszner Brigitte Voit Doris Pospiech 《应用聚合物科学杂志》2019,136(48):48256
We demonstrate in this study that the combination of modern inline monitoring methods [here: inline nuclear magnetic resonance (NMR)] with simulations gains more exact and profound kinetic results than previously used methods like linearization without that combination. The 1H-NMR spectroscopic data (more than 100 data points) are used to construct the copolymerization diagram. The reactivity ratios are obtained applying the van Herks nonlinear least square method. The examination of the radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) with (2-{[2-(ethoxycarbonyl)prop-2-en-1-yl]oxy}ethyl) phosphonic acid (ECPPA) as important adhesive monomer used in dentistry yields reactivity ratios of rHEMA = 1.83; rECPPA = 0.42. The copolymerization diagram reflects nonideal, non-azeotropic copolymerization. The sequence distribution of the obtained by Monte Carlo simulation indicates the generation of statistical copolymers. As an important finding, it is demonstrated that the repeating units responsible for etching and adhesion are arranged over the whole polymer chain, which is necessary to achieve proper functionality. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48256. 相似文献
54.
An engineered variant of the yeast Pichia pastoris was used to produce the potential malaria vaccine D1M1. This paper describes the implementation of an expanded bed adsorption chromatography step into a sequential cultivation process of the yeast in order to link protein expression, cell release, and product capture of the secreted protein in a fully automated plant. The process is operated with a semi-continuous strategy for an integrated production. Process improvements have been achieved using design of experiments. Resulting purities of product achieved up to 87% with recoveries of 51% in a single downstream operation. Furthermore, a multivariate analysis of historical batch data was used to develop a golden batch model for process monitoring. 相似文献
55.
56.
Eight datasets of 1-h black carbon (BC) concentrations measured in Warsaw agglomeration (Poland), at urban background and sub-urban sites, and in Racibórz, a small town in Upper Silesia district (regional background site) were analyzed to evaluate BC levels, daily profiles and statistical distributions of concentrations in Central-Eastern European region. The observed mean levels ranged from 1483 ng m−3 in suburban site during summer to 3358 ng m−3 in regional background site in winter. Observed diurnal patterns were bimodal in the locations dominated by traffic emissions, but unimodal, with elevated evening peak in individually heated residential area. Three theoretical frequency distributions were applied to fit analyzed datasets separately. The lognormal distribution was the most appropriate to represent the middle-range values, while the high concentrations were satisfactorily predicted by the type I two-parameter exponential distribution which was used to estimate the return periods of extreme concentrations for winter months. 相似文献
57.
58.
随着大数据和云计算的技术的深入应用,人工智能时代的机器学习和深度学习更需要日益增长的数据,因此数据安全与隐私保护变得更加迫切。本文介绍人工智能的定义以及特征,探究数据安全和隐私保护现状,分析数据安全和隐私保护面临的诸多问题,并提出在人工智能时代对数据安全和隐私保护的措施。 相似文献
59.
从硬件和软件两个角度出发,介绍基于DSP的多元数据同步采集与存储系统的组成、工作模式以及功能的测试。系统主要由上位机和数字采集与存储单元组成,其中数字采集与存储单元的硬件部分包括电源模块,值班电路模块,数据采集模块,数据存储模块,时钟同步模块。系统采用DSP作为中央处理芯片,利用经过同步后的秒脉冲作为触发信号,实现同步数据采集。以CF卡作为存储介质,实现数据自容式存储。软件部分实现自检、同步、数据采集存储功能。经过测试,系统工作稳定,功能正常,同步精度在100ns以内。 相似文献
60.
《矿业科学技术学报(英文版)》2020,30(6):747-757
Digitalisation in mining refers to the use of computerised or digital devices or systems and digitised data that are to reduce costs, improve business productivity, and transform mining practices. However, it remains increasingly difficult for mining companies to decide which digital technologies are most relevant to their needs and individual mines. This paper provides an overview of digital technologies currently relevant to mining companies as presented and discussed by mining journals, the media and insight reports of leading consultancy agencies. Relevant technologies were systematically identified using text-mining techniques, and network analyses established the relations between significant technologies. Results demonstrated that currently 107 different digital technologies are pursued in the mining sector. Also, an analysis of the actual implementation of digital technologies in 158 active surface and underground mines reveals a limited uptake of digital technologies in general and that the uptake increases with the run-of-mine production. Large-scale mining operations appear to select and apply digital technologies suitable to their needs, whereas operations with lower production rates do not implement the currently available digital technologies to the same extent. These minor producers may require other digital transformation solutions tailored to their capabilities and needs and applicable to their scale of operations. 相似文献