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   90044篇
  免费   10512篇
  国内免费   3229篇
电工技术   7056篇
技术理论   4篇
综合类   8708篇
化学工业   6730篇
金属工艺   3327篇
机械仪表   4677篇
建筑科学   14969篇
矿业工程   3791篇
能源动力   2988篇
轻工业   18261篇
水利工程   5174篇
石油天然气   4453篇
武器工业   653篇
无线电   5494篇
一般工业技术   5485篇
冶金工业   5036篇
原子能技术   567篇
自动化技术   6412篇
  2025年   41篇
  2024年   2007篇
  2023年   2137篇
  2022年   3044篇
  2021年   3596篇
  2020年   3737篇
  2019年   3027篇
  2018年   2583篇
  2017年   3068篇
  2016年   3213篇
  2015年   3381篇
  2014年   6300篇
  2013年   5148篇
  2012年   6550篇
  2011年   6683篇
  2010年   5183篇
  2009年   5383篇
  2008年   4637篇
  2007年   5505篇
  2006年   4941篇
  2005年   4079篇
  2004年   3512篇
  2003年   3125篇
  2002年   2707篇
  2001年   2035篇
  2000年   1748篇
  1999年   1396篇
  1998年   945篇
  1997年   721篇
  1996年   657篇
  1995年   566篇
  1994年   440篇
  1993年   336篇
  1992年   270篇
  1991年   201篇
  1990年   160篇
  1989年   146篇
  1988年   98篇
  1987年   90篇
  1986年   52篇
  1985年   50篇
  1984年   42篇
  1983年   26篇
  1982年   30篇
  1981年   14篇
  1980年   32篇
  1966年   10篇
  1964年   17篇
  1959年   16篇
  1957年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Flour blends of quinoa-wheat containing 0, 5, 10, 15, and 20% of manually dehulled quinoa meal or flour were evaluated for dough mixing and breadmaking properties and liking of the bread by a small panel. Increasing amounts of quinoa meal or flour increased farinograph absorption and dislike of bread for most of the panel. Dough development time increased with increase in meal but decreased with increase in quinoa flour. At 10% inclusion levels differences in liking from control 100% wheat flour bread were smaller for flour or water extracted meal to most of the panel, than with 10% non-extracted meal. This suggests that 10% inclusion of flour or water extracted meal may have potential for further investigation.  相似文献   
22.
23.
A test chamber has been developed in order to provide a small and simple emission testing facility capable of testing construction products in a climate where the important climatic parameters such as temperature, ventilation rate and air velocity can be varied independently around typical indoor values. The test chamber CLIMPAQ is made of panes of window glass. Other main surface materials are stainless steel and eloxated aluminium. The chamber has a volume of 50.9 litres and is designed to meet the requirements for quantifying air pollution. In this investigation human subjects acted as air pollution judges, and chemical characterization of the air pollution was carried out. Carpet, linoleum, wall paint and seal- ant were tested simultaneously in the CLIMPAQ and in four other chambers ranging from a full-scale chamber of 28 m3 to a field and laboratory emission cell of 3.5· 10?5m3. Product ranking is the same in all chambers for the sensory measurements. Emission rates based on sensory measurements differ for all products less than 100 % except for tests in a 3-litre chamber where emission rates were higher. Chemical measurements differ up to approximately 10 times for the same product in different chambers. Deviations appear to be the result of different environmental parameters in the various chambers. Low air concentrations or high specific ventilation rates seem to increase emissions, while differences in air velocities and sink properties may also be the cause of differences in emission rates.  相似文献   
24.
Diced green bell peppers were soaked in a solution of hydrochloric acid or calcium chloride, air-dried to 50% moisture, held in CO2 at 5.8 MPa for 1, 3 or 5 min, and puffed by abruptly releasing the CO2 pressure. Treatment with 1% CaCl2 increased the size of puffed-dried products as compared to a control; however, HCl treatments did not. The treatment with 1 or 2% CaCl2 reduced shrinkage as compared to the control. The 1% CaCl2 treatment may have increased the CO2 saturation rate.  相似文献   
25.
Abstract This study deals with the modeling of air pollution in apartments from laboratory measurements of source strengths, using formaldehyde and Total Volatile Organic Compounds (TVOCs) as model pollutants. The sources in two test apartments were grouped into two: building-related sources and occupant-related sources. The measured source strengths and ventilation rates were used for the prediction of concentrations expected in the apartments. These predictions were compared to measurements in the apartment over 12 months. The conclusions were that the model predictions based on emission rates measured in the laboratory can be used to predict the long-term concentration of the two model pollutants in the apartments. Considering the measured differences in ventilation between the apartments, an occupant emission rate of between 0.2 and 0.3 mg/h/kg body weight could be estimated. Based on previous suggested limits of acceptable exposures of humans to VOCs, an acceptable average emission rate of VOCs from building materials in general was estimated to be about 30 (μ/m2/h. The modeling showed that during the first 200 days, building materials dominated the emissions. After this, sources relating to the occupants dominated. On average about half of the VOC pollution originated from the building materials.  相似文献   
26.
27.
压力容器材料质量控制的几个重要环节   总被引:2,自引:0,他引:2  
高焕丽 《石化技术》2007,14(4):30-33
针对压力容器材料方面存在的问题,从设计、采购、检验、制造等环节进行了分析,根据实际情况确定材料的质量控制要点。材料使用前要通过各种检测手段,判断材料的真实性,确保所用材料合格;并应从设计、选材、采购、计划、填报内容和选择可靠的供应方等方面加以控制,确保材料的正确使用,为压力容器产品的材料控制提供借鉴。  相似文献   
28.
Engineering the surfaces of components to improve the life and performance of parts used in automotive and aerospace engineering is the active area of research. Suitable Thermal/Mechanical/Thermo mechanical surface engineering treatments will produce extensive rearrangement of atoms in metals and alloys and corresponding marked variations in Physical, Chemical and Mechanical properties. Among the more important of these treatments are heat treatment processes such as hardening by Quenching, Induction hardening and Case Carburizing which rely on phase transformations to produce desired changes in mechanical properties. Other processes where phase transformation occur are casting, welding and machining etc. [1] Phase transformation may be homogeneous or heterogeneous. Homogeneous involves rearrangements in the structure of the material taking place simultaneously in all parts of the solid, while the heterogeneous transformation involves structural changes which are more localized. Alternatively they could be called as Isothermal and Nonisothermal transformation. But irrespective of the classification, these transformations alter the structure of the material giving rise to changes in the mechanical and physical properties of the processed material. It is of interest to review some consequences of surface modification in isothermal (Normalizing) and nonisothermal transformations (Machining) of low carbon steels.  相似文献   
29.
梁伟山 《化肥工业》2006,33(3):44-47
针对磷酸二铵(DAP)产品养分波动大、含水量偏高、易结块、颜色变化大等缺点,在生产过程中采取了相应的解决措施,如配矿、联产、设备改造、工艺指标调整等,使DAP装置不仅保持了原有的优点,而且产品质量问题也得到了有效解决。养分基本保持在64.0%~64.6%,水分下降到2.1%~2.2%,结块现象较少,颜色也比较统一。  相似文献   
30.
结合作者的实际工作 ,总结了对工程建设实施“三道质量控制工序”的经验 ,强调了过程质量控制的重要性 ,较为系统地介绍了化工建设项目预验收工作的程序和内容  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