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排序方式: 共有3825条查询结果,搜索用时 15 毫秒
1.
《中国稀土学报(英文版)》2022,40(8):1199-1210
A series of Sm–Mn mixed oxide catalysts were prepared via precipitation using various precipitants, namely Na2CO3 (NH4)2CO3, and NH3·H2O, and evaluated for the selective catalytic reduction (SCR) of NOx with NH3 at low temperatures. Various characterisation techniques were used to determine the physicochemical properties of the catalysts, and it is found that their catalytic performance is greatly influenced by the nature of the precipitation agent used. It is found that Sm0.1Mn–Na2CO3 and Sm0.1Mn-(NH4)2CO3 exhibit superior catalytic performance in the SCR reaction to that of Sm0.1Mn–NH3·H2O due to an abundance of surface acid sites, high surface concentration of Mn4+, and high NO oxidation capacity. From in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) analysis, we conclude that the Sm–Mn catalysts follow both Eley-Rideal and Langmuir–Hinshelwood mechanisms, and that the Eley-Rideal mechanism is dominant at elevated temperatures. 相似文献
2.
Alvin W. Nienow 《化学,工程师,技术》2021,93(1-2):17-30
From the start of industrial biotechnology, there has been a perception that biological entities are damaged by stirring, so-called ‘shear damage'. Often, it was the soft option to explain a loss of performance when it was due to other factors, such as bubble ingestion with proteins or on scale-up, where tip speed increased when it was due to decreased homogeneity, especially in pH. For many years, poor control and the range of analytical tools available made a more in-depth explanation difficult; and the concepts of ‘high' and ‘low shear' impellers, now largely disproven, increased it. Here, the size of the biological entity is compared to the Kolmogorov microscale of turbulence leading to a reasonably clear picture emerging. The article starts with the author's introduction to the issue approximately 42 year ago with enzymes, conveniently also the smallest entity; and finishes with the largest, filamentous fungi. 相似文献
3.
A Coating that Combines Lotus‐Effect and Contact‐Active Antimicrobial Properties on Silicone 下载免费PDF全文
Nicolas Rauner Christoph Mueller Sabine Ring Sara Boehle Arne Strassburg Carmen Schoeneweiss Marvin Wasner Joerg C. Tiller 《Advanced functional materials》2018,28(29)
The antimicrobial equipment of materials is of great importance in medicine but also in daily life. A challenge is the antimicrobial modification of hydrophobic surfaces without increasing their low surface energy. This is particularly important for silicone‐based materials. Because most antimicrobial surface modifications render the materials more hydrophilic, methods are needed to achieve antimicrobial activity without changing the high water‐contact‐angle. This is achieved in the present work, where SiO2 nanoparticles are prepared and functionalized with 3‐(trimethoxysilyl)‐propyldimethyloctadecyl ammonium chloride (QAS) in a one‐pot synthesis. The modified nanoparticles are applied onto a silicone surface from suspension with no need of elaborate pretreatment. The resulting surface exhibits a Lotus‐Effect combined with contact‐active antimicrobial properties. The particle surfaces show self‐organizing micro‐ and nanostructures that afford a water‐contact angle of 144° and a hysteresis below 10°. The particles are self‐adhering on the silicone after solvent evaporation and resistant against immersion into and washing with water for at least 5 d. Thereby, the adhesion of the bacterial strain Staphylococcus aureus to these surfaces is reduced and the remaining bacterial cells are killed within 16 h. This is the first example of a Lotus‐Effect surface with intrinsic contact‐active antimicrobial properties. 相似文献
4.
尺度问题作为对地观测的主要挑战和遥感科学的核心问题,一直以来备受关注.国内外学者对这一问题进行了大量的基础理论研究和科学验证工作,探讨和解决了许多与遥感尺度相关的核心问题.当然,在遥感探测内容中,发射率和温度遥感中也存在明显的尺度问题.以往混合像元发射率尺度问题的研究往往集中于地球表面,幸运的是,月球为我们研究这一问题提供了绝佳的对象.同时,伴随着Diviner热辐射探测器月表测量数据的不断更新,混合像元中发射率尺度问题的具体研究及其定量描述逐渐变为可能.本文以月表Diviner热红外测量数据为基础,在充分研究和分析Diviner数据特征和发射率计算方法的前提下,以不同尺度下的Apollo 15登月区或者登月点热红外发射率为研究对象,依据混合像元发射率定义,分析和研究了混合像元中发射率的尺度转换和尺度效应两个问题,从发射率数值角度出发讨论和验证了尺度变换和尺度效应的一般规律,并给出定量描述,希望能够为尺度变换和尺度效应等问题的研究提供理论支持和实验依据. 相似文献
5.
在全钢载重子午线轮胎胎面胶中加入不同用量炭黑N234,并将白炭黑与炭黑并用,考察炭黑用量和添加白炭黑对胶料性能的影响。结果表明:随着炭黑N234用量增大,不添加白炭黑的胶料Fmax和门尼粘度增大,门尼焦烧时间呈缩短趋势;密度、硬度和定伸应力提高,拉伸强度和回弹值降低,撕裂强度先提高后降低,耐磨性能提高,生热增大,炭黑用量不宜过大;在填料用量相当的条件下,添加白炭黑的胶料门尼粘度较小,门尼焦烧时间较短,撕裂强度和耐磨性能显著提高,生热明显降低;随着炭黑用量增大,不添加白炭黑的胶料弹性模量和损耗因子总体提高;总体来看,添加45份炭黑N234和10份白炭黑的胎面胶滞后损失和生热较低。 相似文献
6.
《Journal of the European Ceramic Society》2021,41(15):7572-7584
The delayed failure of SiC fibrous reinforcement has continuously been investigated to warrant the long term performances of Ceramic Matrix Composite (CMC). Chiefly assessed on multifilament tow samples to alleviate some handling difficulties, subcritical crack growth (SCG) parameters are however ruled by structural artifacts which hinder the identification of intrinsic filament behavior. In this paper, we propose to estimate the true filament parameters for 5 fiber types from bundle behavior using a recently communicated Monte Carlo algorithm integrating flaw and stress distributions through a deterministic fracture mechanics law under Paris’ formulation. So computed tow lifetime are broadly dispersed, encompassing raw data, and show a structure-dependent scale effect, revealed by nfilament>ntow where n is the stress exponent. The relationship between SCG coefficient and chemical composition of the substrate is discussed and highlights the major effect of doping elements (Ti or Zr), oxygen or hydrogen content. 相似文献
7.
作为促进绿色出行的重要举措,已
有诸多研究分析建成环境或交通需求管理
对出行行为的影响,但大多数忽视了两者之
间的协同作用。准确分析建成环境、交通需
求管理对出行行为的影响机制,以及其协同
效应,能够为促进我国大城市绿色出行、贯
彻绿色发展理念提供理论支撑和精准施策
依据。本文基于当前研究现状,对建成环境
与出行行为、交通需求管理与出行行为的影
响,以及建成环境和交通需求管理的协同作
用研究进行了总结,并结合我国大城市建成
环境和居民出行特征对学术研究热点问题
进行展望。 相似文献
8.
城市绿地在营造健康的人居环境方
面发挥着重要的作用。大量研究证明了城市
绿地和公共健康的相关性,但仅凭相关性分
析无法得出因果关系。部分学者提出城市绿
地健康影响机制的理论研究并进行了相关的
实证研究。如何定量分析城市绿地对公共健
康的影响机制值得深入探讨。通过梳理城市
绿地健康影响机制的理论基础;采用范围综
述的方法分析现有实证研究中的研究方法、
研究变量和数据获取,讨论造成研究结果不
一致的原因;并从优化研究设计、检验多重理
论路径、多维度评估城市绿地特征3方面提
出改进实证研究的建议。最后,基于有调节
的中介模型和证据综合,提出城市绿地对公
共健康的影响机制。以期完善城市绿地如何
发挥健康效益的认知,也为城市绿地促进公
共健康的循证证据综合提供科学证据。 相似文献
9.
符号学的跨学科研究动态使建筑符号
的“形—意”本原研究或可从早期人类以原始
神话思维为起点建立的“宇宙生成模型和时空
观念”出发进行源流推演性解读,找寻一种根
植于人类文化符号系统“形—意”同构的原型性
解释。本文从梳理形式符号原型研究的理论范
式出发,以甲骨文、金文出现的建筑类文字“宅、
空、室、楹、阑、坛、台”等为研究对象,以象形
文字字形特征的普遍解读方式结合建筑学本体
思考,阐释早期中国建筑在类型、形态上的发展
以及建筑符号象征表意功能传承实现的过程。
管窥建筑作为中国古代“崇天—通天”时空观念
象征符号的“能指与所指”,探析我国早期建筑
类型与形态发展中的文化隐喻与象征。 相似文献
10.
Meifang Luo Chaozhong Guo Xinyi Luo Zhaoxu Li Yuan Qin Weizhong Zhang 《International Journal of Hydrogen Energy》2021,46(2):2117-2127
It is of great urgency to design inexpensive and high-performance oxygen reduction reaction (ORR) electrocatalysts derived from biowastes as substitutes for Pt-based materials in electrochemical energy-conversion devices. Here we propose a strategy to synthesize three-dimensional (3D) porous nitrogen-doped network carbons to catalyze the ORR from two-step pyrolysis engineering of biowaste scale combined with the use of a ZnCl2 activator and a FeCl2 promotor. Electrochemical tests show that the synthesized network carbons have exhibited comparable ORR catalytic activity with a half-wave potential (~0.85 V vs. RHE) and outstanding cyclical stability in comparison to the Pt/C catalyst. Beyond that, a high electron transfer number (~3.8) and a low peroxide yield (<7.6%) can be obtained, indicating a four-electron reaction pathway. The maximum power density is ~68 mW cm?2, but continuous discharge curves (at a constant potential of ~1.30 V) for 12 h are not obviously declined in Zn-air battery tests using synthesized network carbons as the cathodic catalyst. The formation of 3D porous structures with high BET surface area can effectively expose the surface catalytic sites and promote mass transportation to boost the ORR activity. This work may open a new idea to prepare porous carbon-based catalysts for some important reactions in new energy devices. 相似文献