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   8681篇
  免费   740篇
  国内免费   265篇
电工技术   503篇
技术理论   1篇
综合类   571篇
化学工业   1486篇
金属工艺   358篇
机械仪表   438篇
建筑科学   550篇
矿业工程   232篇
能源动力   226篇
轻工业   872篇
水利工程   153篇
石油天然气   506篇
武器工业   60篇
无线电   852篇
一般工业技术   1060篇
冶金工业   670篇
原子能技术   72篇
自动化技术   1076篇
  2024年   42篇
  2023年   147篇
  2022年   254篇
  2021年   357篇
  2020年   253篇
  2019年   218篇
  2018年   269篇
  2017年   284篇
  2016年   274篇
  2015年   341篇
  2014年   428篇
  2013年   549篇
  2012年   545篇
  2011年   592篇
  2010年   479篇
  2009年   447篇
  2008年   487篇
  2007年   461篇
  2006年   467篇
  2005年   335篇
  2004年   273篇
  2003年   234篇
  2002年   204篇
  2001年   228篇
  2000年   194篇
  1999年   200篇
  1998年   276篇
  1997年   203篇
  1996年   144篇
  1995年   111篇
  1994年   92篇
  1993年   68篇
  1992年   37篇
  1991年   28篇
  1990年   21篇
  1989年   22篇
  1988年   21篇
  1987年   13篇
  1986年   10篇
  1985年   7篇
  1984年   6篇
  1983年   11篇
  1982年   9篇
  1980年   5篇
  1979年   5篇
  1978年   3篇
  1977年   10篇
  1976年   11篇
  1975年   2篇
  1974年   3篇
排序方式: 共有9686条查询结果,搜索用时 31 毫秒
81.
介绍了无润滑空气压缩机冷却水系统结垢的危害性,阐述了清洗的原理,提出了清洗时应注意的工艺参数,操作时的注意事项和由此带来的经济效益。  相似文献   
82.
金属闪光外墙乳胶漆的研制及性能研究   总被引:1,自引:0,他引:1  
以丙烯酸酯及有机硅单体为原料合成了核-壳型硅丙乳液,用自制分散剂将闪光铝粉分散成水性闪光铝粉浆,并成功分散于硅丙乳液中,加入进口助剂,配制成水性金属闪光外墙乳胶漆.讨论了基料的玻璃化温度、单体的加入方式、引发剂、乳化剂、反应温度、聚合工艺和pH等对乳胶漆性能的影响.  相似文献   
83.
Straarup EM  Porsgaard T  Mu H  Hansen CH  Høy CE 《Lipids》2005,40(7):677-684
In this study we examined the lymphatic transport in rats of FA after administration of interesterified oils containing CLA, with emphasis on the location of CLA and octanoic acid in the TAG. The oils were produced by enzymatic interesterification. Eight oils with different structures or FA profiles were examined in this study: MCM, CMC, OCO, and COC, where M was expected to be octanoic acid and O oleic acid. In group 1, C was CLA as a mixture of the two CLA isomers c9, t11 or t10, c12, and in group 2, C was mainly the isomer t10, c12. Rats were subjected to cannulation of the mesenteric lymph duct, and the following day they were intragastrically administered one of the oils and lymph samples were collected for 24 h. The lymphatic transport of total FA from 0 to 8 h in group 1 was significantly (P < 0.05) higher for the OCO-1 and the COC-1 oils than for the CMC-1 oil. Similarly, in group 2 the transport was higher for the OCO-2 oil than for the CMC-2 oil. The recovery of both of the CLA isomers examined was similar (50-70%) and independent of the isomer, oil structure, and FA profile, whereas more octanoic acid was recovered from the CMC oils than from the MCM oils. The results indicated that the FA profiles and the position of octanoic acid had only a minor influence on the absorption of CLA.  相似文献   
84.
85.
As an effective approach for multi-input multi-output regression estimation problems, a multi-dimensional support vector regression (SVR), named M-SVR, is generally capable of obtaining better predictions than applying a conventional support vector machine (SVM) independently for each output dimension. However, although there are many generalization error bounds for conventional SVMs, all of them cannot be directly applied to M-SVR. In this paper, a new leave-one-out (LOO) error estimate for M-SVR is derived firstly through a virtual LOO cross-validation procedure. This LOO error estimate can be straightway calculated once a training process ended with less computational complexity than traditional LOO method. Based on this LOO estimate, a new model selection methods for M-SVR based on multi-objective optimization strategy is further proposed in this paper. Experiments on toy noisy function regression and practical engineering data set, that is, dynamic load identification on cylinder vibration system, are both conducted, demonstrating comparable results of the proposed method in terms of generalization performance and computational cost.  相似文献   
86.
Poly(trimethylene terephthalate) (PTT) nano composites were synthesized by in situ polymerization at high temperature with two thermally stable organoclays: 1,2‐dimethylhexadecylimidazolium‐montmorillonite (IMD‐MMT) and dodecyltriphenyl phosphonium‐MMT (C12PPh‐MMT). PTT hybrid fibers with various organoclay contents were melt‐spun at various draw ratios (DRs) to produce monofilaments. The thermomechanical properties and morphologies of the PTT hybrid fibers were characterized using differential scanning calorimetry, thermogravimetric analysis, wide‐angle X‐ray diffraction, electron microscopy, and mechanical tensile properties analysis. The nanostructure of the hybrid fibers was observed by both scanning and transmission electron microscopy, which showed that the clay layers were well dispersed into the matrix polymer, although some clusters or agglomerated particles were also detected. Unlike the hybrids containing IMD‐MMT, the clay layers of the C12PPh‐MMT hybrid fiber were more dispersed into the matrix polymer. The thermal stability and tensile properties of the hybrid fibers increased with increasing clay content for DR = 1. However, as DR increased from 1 to 9 the ultimate strength and initial modulus of the hybrid fibers with IMD‐MMT increased slightly whereas those of C12PPh‐MMT hybrid fibers decreased slightly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4535–4545, 2006  相似文献   
87.
烟气脱硫的发展、技术与产业化探讨   总被引:2,自引:0,他引:2  
庾晋  白木  周洁 《煤化工》2003,31(1):61-64
回顾了我国烟气脱硫的发展历程 ,总结了我国烟气脱硫产业化方面取得的成绩和存在的问题 ,介绍了国际上烟气脱硫发展的基本情况  相似文献   
88.
简要介绍了一种XHM253/20密闭式炼胶机转子铜瓦椭圆的修复方法.该方法简便易行,修复工期短,修复质量高,在实际工作中具有一定参考价值.  相似文献   
89.
Summary A series of poly(ethylene terephthalate) (PET) nanocomposites containing organically-modified mica (HB-Mica) were prepared by in-situ interlayer polymerization of dimethyl terephthalate and ethylene glycol. The PET nanocomposites, which contained organoclay loadings of 0 to 2 wt %, were melt-spun to produce monofilaments with various draw ratios. Some of the clay particles appeared well dispersed within the PET matrix, while others were found to form agglomerates with sizes greater than 20 nm. The addition of a small amount of organoclay was sufficient to improve the thermo-mechanical properties of the PET hybrid fibers. Both the thermal stability and the mechanical tensile properties increased with increasing clay content for draw ratios of 1–16.  相似文献   
90.
随着数字化、信息化技术在物流领域应用的飞速发展,各种各样的仓储管理系统日益受到关注。本文介绍的基于IOS平台的小型仓储管理系统是利用IOS设备对货物信息进行采集,通过SQLite数据库技术、ZXing库等软硬件方式构建的业务系统,可以较好地适应中小规模用户数据交互的需求。同时,系统具备造价低廉、操作便捷等优点。  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