首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9140篇
  免费   1028篇
  国内免费   523篇
电工技术   1202篇
综合类   932篇
化学工业   1086篇
金属工艺   292篇
机械仪表   483篇
建筑科学   1017篇
矿业工程   325篇
能源动力   133篇
轻工业   359篇
水利工程   206篇
石油天然气   403篇
武器工业   89篇
无线电   802篇
一般工业技术   1268篇
冶金工业   392篇
原子能技术   48篇
自动化技术   1654篇
  2024年   26篇
  2023年   87篇
  2022年   185篇
  2021年   198篇
  2020年   253篇
  2019年   197篇
  2018年   181篇
  2017年   267篇
  2016年   333篇
  2015年   327篇
  2014年   793篇
  2013年   525篇
  2012年   830篇
  2011年   843篇
  2010年   691篇
  2009年   624篇
  2008年   578篇
  2007年   706篇
  2006年   629篇
  2005年   523篇
  2004年   349篇
  2003年   317篇
  2002年   285篇
  2001年   219篇
  2000年   190篇
  1999年   105篇
  1998年   83篇
  1997年   61篇
  1996年   56篇
  1995年   46篇
  1994年   36篇
  1993年   20篇
  1992年   22篇
  1991年   16篇
  1990年   8篇
  1989年   9篇
  1988年   5篇
  1987年   7篇
  1986年   5篇
  1985年   7篇
  1984年   4篇
  1983年   5篇
  1978年   3篇
  1966年   4篇
  1965年   3篇
  1961年   3篇
  1960年   4篇
  1959年   3篇
  1958年   2篇
  1957年   2篇
排序方式: 共有10000条查询结果,搜索用时 210 毫秒
1.
A appropriate size with three-dimension(3 D) channels for lithium diffusion plays an important role in constructing highperforming LiNi_(0.5)Mn_(1.5)O_4(LNMO) cathode materials, as it can not only reduce the transport path of lithium ions and electrons, but also reduce the side effects and withstand the structural strain in the process of repetitive Li~+ intercalation/deintercalation. In this work, an e fficient method for designing the hollow LNMO microsphere with 3 D channels structure by using polyethylene oxide(PEO) as soft template agent assisted solvothermal method is proposed. Experimental results indicate that PEO can make the reagents mingle evenly and nucleate slowly in the solvothermal process, thus obtaining a homogeneous distribution of carbonate precursors. In the final LNMO products, the hollow 3 D channels structure obtained by the decomposition of PEO and carbonate precursor in the calcination can provide abundant electroactive zones and electron/ion transport paths during the charge/discharge process, which benefits to improve the cycling performance and rate capability. The LNMO prepared by adding 1 g PEO possesses the most outstanding electrochemical performance, which presented an excellent discharge capacity of 143.1 mAh g~(-1) at 0.1 C and with a capacity retention of 92.2% after 100 cycles at 1 C. The superior performance attributed to the 3 D channels structure of hollow microspheres, which provide uninterrupted conductive systems and therefore achieve the stable transfer for electron/ion.  相似文献   
2.
A new aqueous slurry-based laminated object manufacturing process for porous ceramics is proposed: firstly, an organic mesh sheet is pre-paved as a pore-forming template before slurry layer scraping; secondly, the 2D pattern is built with laser outline cutting of the dried mesh–ceramic composite layer; finally, the pore structure is formed after degreasing and sintering. Alumina parts with porosities of 51.5 %, round hole diameters of 80 ± 5 μm were fabricated using 70 wt. % solid content slurry and 100 mesh nylon net. Using an organic mesh as the framework and template not only reduces the risk of damage of the green body but also ensures the regularity, uniformity and connectivity of the micron scaled pore network. The layer-by-layer drying method avoids the delamination phenomenon and improves the paving density. The new method can realize the flexible design of the pore structure by using various organic mesh templates.  相似文献   
3.
《Ceramics International》2021,47(23):33280-33285
This study investigated carbon nanotube filtration technology using catalyst particles supported on silicalite-1–biomorphic carbon materials (BCMs). Aqueous solutions of Mn(II), Cu(II), Cr(III), Cd(II), and Pb(II) were used to test the efficiency of heavy metal ions removal. Carbon nanotubes (CNTs) were synthesized and grown on BCMs by the chemical vapor deposition method catalyzed with the catalyst (Co, Fe, and Ni). The synthesized CNTs with Co– and Fe– nanoparticles were typically multi-walled carbon nanotubes, and they showed good crystallinity (ID/IG = 1.05) and yield of (11.10 and 8.86) %. The removal efficiency of Mn(II), Cu(II), Cr(III), Cd(II), and Pb(II) ions using Co-catalyzed CNT filter was 97.57%, 98.01%, 97.89%, 97.42%, and 99.99%, respectively.  相似文献   
4.
本文以膨润土为研究对象,结合膨润土标准化现状,阐述了膨润土在建材、工程、农业以及畜牧业等领域的应用发展。在此基础上,分析了目前国内膨润土标准和膨润土防水毯标准的详细现状,并对标准化现状存在的问题进行详细分析,最后提出建立我国膨润土标准体系的建设性意见。  相似文献   
5.
Online configuration of large-scale systems such as networks requires parameter optimization within a limited amount of time, especially when configuration is needed as a response to recover from a failure in the system. To quickly configure such systems in an online manner, we propose a Probabilistic Trans-Algorithmic Search (PTAS) framework which leverages multiple optimization search algorithms in an iterative manner. PTAS applies a search algorithm to determine how to best distribute available experiment budget among multiple optimization search algorithms. It allocates an experiment budget to each available search algorithm and observes its performance on the system-at-hand. PTAS then probabilistically reallocates the experiment budget for the next round proportional to each algorithm’s performance relative to the rest of the algorithms. This “roulette wheel” approach probabilistically favors the more successful algorithm in the next round. Following each round, the PTAS framework “transfers” the best result(s) among the individual algorithms, making our framework a trans-algorithmic one. PTAS thus aims to systematize how to “search for the best search” and hybridize a set of search algorithms to attain a better search. We use three individual search algorithms, i.e., Recursive Random Search (RRS) (Ye and Kalyanaraman, 2004), Simulated Annealing (SA) (Laarhoven and Aarts, 1987), and Genetic Algorithm (GA) (Goldberg, 1989), and compare PTAS against the performance of RRS, GA, and SA. We show the performance of PTAS on well-known benchmark objective functions including scenarios where the objective function changes in the middle of the optimization process. To illustrate applicability of our framework to automated network management, we apply PTAS on the problem of optimizing link weights of an intra-domain routing protocol on three different topologies obtained from the Rocketfuel dataset. We also apply PTAS on the problem of optimizing aggregate throughput of a wireless ad hoc network by tuning datarates of traffic sources. Our experiments show that PTAS successfully picks the best performing algorithm, RRS or GA, and allocates the time wisely. Further, our results show that PTAS’ performance is not transient and steadily improves as more time is available for search.  相似文献   
6.
主要介绍了2003年EAGE岩石物性测试分析技术取得的新进展。从本届年会看,岩石物理内容主要涉及岩石物理模型建立、时延地震岩石物理与岩石各向异性分析、喷射频率和流体饱和度及其分布预测、岩石物理模拟等新方法、新技术、新成果。在充分考虑岩石物理受当地地质因素影响后,提出岩石物理模版概念,目的是为地质专家方便对岩性和流体的解释提供一种工具。  相似文献   
7.
本文简要地介绍YH-2并行巨型机有关结构设计中对标准化、通用化及模块化的几点考虑。  相似文献   
8.
奎宁印迹聚合物的吸附与识别特性的研究   总被引:3,自引:0,他引:3  
以奎宁为模板分子 ,利用分子印迹技术合成了一种新型的类似于人工受体的印迹聚合物 ,研究了它对奎宁和其它底物的吸附特性和选择性识别能力 ,并对其固相萃取性能做了初步的研究。  相似文献   
9.
概述了钛铜复合棒研制开发及发展历程,并介绍了钛铜复合棒的主要性能,以及钛铜复合棒的标准化情况。  相似文献   
10.
介绍了我国数字电视标准化总体情况,重点介绍接收端的标准化工作现状及数字电视的标准符合性检测情况。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号