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   21529篇
  免费   1974篇
  国内免费   1070篇
电工技术   663篇
技术理论   2篇
综合类   1557篇
化学工业   5589篇
金属工艺   291篇
机械仪表   693篇
建筑科学   2512篇
矿业工程   662篇
能源动力   1410篇
轻工业   1842篇
水利工程   447篇
石油天然气   3462篇
武器工业   65篇
无线电   338篇
一般工业技术   1310篇
冶金工业   1735篇
原子能技术   337篇
自动化技术   1658篇
  2024年   89篇
  2023年   350篇
  2022年   672篇
  2021年   821篇
  2020年   783篇
  2019年   697篇
  2018年   556篇
  2017年   612篇
  2016年   745篇
  2015年   747篇
  2014年   1281篇
  2013年   1346篇
  2012年   1624篇
  2011年   1493篇
  2010年   1209篇
  2009年   1183篇
  2008年   1030篇
  2007年   1321篇
  2006年   1374篇
  2005年   1126篇
  2004年   884篇
  2003年   757篇
  2002年   689篇
  2001年   557篇
  2000年   521篇
  1999年   390篇
  1998年   298篇
  1997年   241篇
  1996年   197篇
  1995年   170篇
  1994年   172篇
  1993年   115篇
  1992年   101篇
  1991年   97篇
  1990年   80篇
  1989年   60篇
  1988年   21篇
  1987年   18篇
  1986年   18篇
  1985年   33篇
  1984年   21篇
  1983年   19篇
  1982年   20篇
  1981年   8篇
  1980年   5篇
  1977年   3篇
  1972年   2篇
  1959年   5篇
  1955年   2篇
  1951年   4篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
91.
山东球墨铸铁管有限公司350m^3高炉投产后,原有的焦炭货场场地小,而焦炭用量增大、供货厂家增多,无法做到混匀人炉。通过采取对焦炭进行分区管理和高架布料混匀改造后,焦炭质量趋向稳定;焦末的生成量从1318%降低到8.9%,提高了焦炭的利用率;同时焦比降低。  相似文献   
92.
潘文丽 《染整技术》2021,43(1):45-47,57
随着乳胶产品的广泛应用,如何鉴定乳胶中的天然成分以及对毒害化学物质的风险监控成为关注的焦点.采用红外光谱法和水提蛋白质法,利用天然乳胶中所含蛋白质的特征,可准确、快速地鉴定天然乳胶与合成聚异戊二烯乳胶.同时分析了乳胶生产过程中存在的危害化学物质风险及检测限量.  相似文献   
93.
With the mine exploitation depth getting deeper and deeper, the mine heat-harm turns into another natural disaster after the five disasters, which are the roof, the gas, the fire, the dust and the flood disaster. Compared with other researches on prevention and cure against the heat-harm, the research on prevention and cure against the heat-harm in constructing mine are less. Referring to the experience of prevention and cure against the heat-harm home and 'abroad, analyzing the characteristic of cooling in the constructing mine, and based on the ground former freezing equipments and the modified mine temporary cooling equipments, the paper proposed four technical projects. By comparing with the four technical projects, the second project is preponderant both in technology and economy and can solve the heat-harm of the constructing mine, which is proved by the forecast and calculation. The project can be widely applied in de-temperature tasks of high temperature and heat-harm mines during the mine constructing period and in the exploiting preparing phase.  相似文献   
94.
章冬梅 《煤炭技术》2007,26(7):96-97
煤矿工业建筑的设计要满足工艺流程的要求和结构体系本身规范的要求,还要体现人性化设计理念。本文通过对准备车间一个单体建筑的设计过程的总结,呼吁整个行业能重视人性化设计理念。  相似文献   
95.
Unlike humans, some animals have evolved a physiological ability to deposit porphyrins, which are pigments produced during heme synthesis in cells, in the skin and associated integument such as hair. Given the inert nature and easiness of collection of hair, animals that present porphyrin-based pigmentation constitute unique models for porphyrin analysis in biological samples. Here we present the development of a simple, rapid, and efficient analytical method for four natural porphyrins (uroporphyrin I, coproporphyrin I, coproporphyrin III and protoporphyrin IX) in the Southern flying squirrel Glaucomys volans, a mammal with hair that fluoresces and that we suspected has porphyrin-based pigmentation. The method is based on capillary liquid chromatography-mass spectrometry (CLC-MS), after an extraction procedure with formic acid and acetonitrile. The resulting limits of detection (LOD) and quantification (LOQ) were 0.006–0.199 and 0.021–0.665 µg mL−1, respectively. This approach enabled us to quantify porphyrins in flying squirrel hairs at concentrations of 3.6–353.2 µg g−1 with 86.4–98.6% extraction yields. This method provides higher simplicity, precision, selectivity, and sensitivity than other methods used to date, presenting the potential to become the standard technique for porphyrin analysis.  相似文献   
96.
97.
齐洪涛 《山西冶金》2007,30(2):9-10
重点论述了焦炭反应性在高炉碱金属循环富集条件下的变化,并根据国内外研究提出的反应性会发生逆转的概念,分析了太钢高炉生产的实际情况,明确了现行焦炭强度指标对太钢高炉生产的指导意义。  相似文献   
98.
For lead-cooled fast reactors, steam generator tube leakage and/or rupture (SGTL/R) is one of the safety issues. During SGTL/R, high-pressure water from secondary side of main heat exchangers is injected to lower-pressure primary side. It may have significant negative impact on the integrity of structures nearby, the flow and heat transfer capabilities of the primary system and the reactivity of the core. The transport of steam bubbles and subsequent void accumulation in the primary system of SNCLFR-100 were addressed in the paper. Based on ANSYS FLUENT, Lagrangian tracking of steam bubbles (voids) in Eulerian flow field was performed to identify the locations and traces of steam bubbles after SGTL. The core safety characteristics under SGTL/R accident were also evaluated. The results show that the leakage location, bubble size and the liquid contamination all have influence on the void transport. For the contaminated primary system of a lead-cooled fast reactor, the occurrence of SGTL with a low leakage location may significantly affect the normal operation of the reactor.  相似文献   
99.
超级电容器作为一类新兴的能量存储转换器件,因其充放电速度快、寿命长和安全环保的特点而受到推崇。其中,用于超级电容器的电极材料一直是人们的研究重点,综合原料来源、价格和制备工艺等因素,多孔碳电极材料成为首选。盐模板法和KOH化学活化法都是制备多孔碳电极常用的方法,前者产物的孔结构以介孔为主,但操作复杂;后者活化产物比表面积大,可以精确控制多孔碳电极的孔径分布和孔体积,但该法活化后的多孔碳多以微孔为主。若将两者结合,形成优势互补,协同构建合理的碳材料结构,有助于提升多孔碳电极的电化学性能。以锂电负极行业的固废——针状焦的生焦粉为原料,利用模板和化学活化相结合的方法制备电极材料,探索盐(KCl)和碱(KOH)的添加比例对碳电极材料电化学性能的影响。研究结果表明,两种方法相结合制备得到的多孔碳样品的碳结构以表面缺陷较多的无定型碳为主。随着KOH加入量的增加,无定型结构的碳增加,但是加入过量的KOH并不能提高无定型碳的含量。三电极测试分析发现,样品PC-2表现出优异的电容性能,在1 A·g-1的电流密度下,质量比电容达到266.9 A·g-1;在10 A·g-1的高电流密度下,容量保持率高达79.4%。该电极材料的内阻仅为0.67 Ω,并且双电层电容性能有极短的响应时间。当m(生焦粉)∶m(KCl)∶m(KOH)=1∶3∶2时,KCl和KOH的协同活化效果达到了最佳,显著提高了碳电极材料电荷的传输能力,且能有效地缩短电解质离子在材料内部的扩散路径,表现出较快的充放电速度。  相似文献   
100.
The goal of this study was application of corn starch and ground walnut shells in various amounts by weight as biofillers of natural rubber (NR) biocomposites. Additionally, ionic liquid 1-butyl-3-methylimidazolium chloride (BmiCl) and (3-aminopropyl)-triethoxysilane (APTES) were used to increase the activity of biofillers and to improve the curing characteristics of NR composites. The effect of biofillers used and their modification with aminosilane or ionic liquid on the curing characteristics of NR composites and their functional properties, including crosslink density, mechanical properties in static and dynamic conditions, hardness, thermal stability and resistance to thermo-oxidative aging were investigated. Starch and ground walnut shells were classified as inactive fillers, which can be used alternatively to commercial inactive fillers, e.g., chalk. BmiCl and APTES were successfully used to support the vulcanization and to improve the dispersion of biofillers in NR elastomer matrix. Vulcanizates with starch, especially those containing APTES and BmiCl, exhibited improved tensile properties due to the higher crosslink density and homogenous dispersion of starch, which resulted from BmiCl addition. NR filled with ground walnut shells demonstrated improved resistance to thermo-oxidative aging. It resulted from lignin present in walnut shells, the components of which belong to polyphenols, that have an antioxidant activity.  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