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   522篇
  免费   35篇
电工技术   8篇
化学工业   105篇
金属工艺   11篇
机械仪表   12篇
建筑科学   24篇
矿业工程   1篇
能源动力   11篇
轻工业   50篇
无线电   92篇
一般工业技术   92篇
冶金工业   43篇
原子能技术   3篇
自动化技术   105篇
  2023年   5篇
  2022年   8篇
  2021年   26篇
  2020年   6篇
  2019年   16篇
  2018年   22篇
  2017年   12篇
  2016年   23篇
  2015年   12篇
  2014年   13篇
  2013年   29篇
  2012年   37篇
  2011年   44篇
  2010年   20篇
  2009年   26篇
  2008年   36篇
  2007年   29篇
  2006年   17篇
  2005年   13篇
  2004年   15篇
  2003年   13篇
  2002年   9篇
  2001年   9篇
  2000年   6篇
  1999年   11篇
  1998年   20篇
  1997年   13篇
  1996年   6篇
  1995年   4篇
  1994年   6篇
  1993年   3篇
  1992年   9篇
  1991年   5篇
  1989年   1篇
  1988年   5篇
  1987年   3篇
  1985年   1篇
  1983年   4篇
  1982年   4篇
  1981年   2篇
  1980年   3篇
  1978年   2篇
  1977年   1篇
  1976年   2篇
  1975年   1篇
  1973年   1篇
  1972年   2篇
  1971年   1篇
  1970年   1篇
排序方式: 共有557条查询结果,搜索用时 484 毫秒
551.
The electrical resistance of asbestos composite separators stabilized with high concentration ( 40% w/w) of polyphenylene sulfide in 100°C, 30–50 %w/w KOH strongly depends on the initial porosity of the asbestos support. The separators with 0.36 V/w water sorption capacity have 0.20–0.35 Ω. cm2 ohmic drop according to expectations derived from a previous material study. The mechanical strength appears to be related to the separator thickness.  相似文献   
552.
The objective of this cross-sectional herd-level study was to assess the association of calf management practices on source dairy farms with mortality risk on veal farms. From April to October 2016, 52 source dairy farms supplying male calves to 2 veal operations were visited once. A questionnaire was administered that covered all areas of calf management, calves between 1 and 10 d of age were examined using a standardized health scoring system, and blood was taken to evaluate passive transfer of immunoglobulins. The mortality risk for calves from each dairy farm was calculated based on the number of male calves sold from the dairy farm and that died during 2016 at the veal operations. The mean mortality risk was calculated for both veal farms and, based on the veal facility-adjusted mortality risk, dairy farms were classified as high- or low-mortality source farms. Using the information gathered at the 52 source dairy farms, a logistic regression model was used to assess factors associated with being a high-mortality source farm. Suppliers to veal farm 1 had a mean mortality risk of 9.6% and suppliers to veal farm 2 had a mean mortality risk of 4.2%. The lower mortality risk at veal farm 2 was partially influenced by a shorter period of observation. Of the 182 calves examined during the single visit to the source dairy farms, 41% of male calves and 29% of female calves had at least one identifiable health abnormality. The risk of failure of passive transfer on source dairy farms was low, with only 13% of calves tested having <10 mg of IgG/mL of serum. The subset of calves examined at the source dairy farm was not followed prospectively to the veal farms. Using a tube feeder or pail to feed colostrum, bedding male calves on wood shavings or chopped straw at the source dairy farm, and the herd veterinarian not routinely and actively inquiring about the health and performance of calves during regular herd visits were significantly associated with the farm being classified as a high-mortality source dairy farm. Checking the calving pen at an interval of every 3 h or more during the day was associated with a lower probability of being classified as a high-mortality source dairy farm. The results of this study suggest that there are management practices on the source farm that contribute to the risk of mortality on veal farms.  相似文献   
553.
Water deficit causes substantial yield losses that climate change is going to make even more problematic. Sustainable agricultural practices are increasingly developed to improve plant tolerance to abiotic stresses. One innovative solution amongst others is the integration of plant biostimulants in agriculture. In this work, we investigate for the first time the effects of the biostimulant –Leafamine®–a protein hydrolysate on greenhouse lettuce (Lactuca sativa L.) grown under well-watered and water-deficit conditions. We examined the physiological and metabolomic water deficit responses of lettuce treated with Leafamine® (0.585 g/pot) or not. Root application of Leafamine® increased the shoot fresh biomass of both well-watered (+40%) and deficit-irrigated (+20%) lettuce plants because the projected leaf area increased. Our results also indicate that Leafamine® application could adjust the nitrogen metabolism by enhancing the total nitrogen content, amino acid (proline) contents and the total protein level in lettuce leaves, irrespective of the water condition. Osmolytes such as soluble sugars and polyols, also increased in Leafamine®-treated lettuce. Our findings suggest that the protective effect of Leafamine is a widespread change in plant metabolism and could involve ABA, putrescine and raffinose.  相似文献   
554.
555.
We present a new variational method for multi-view stereovision and non-rigid three-dimensional motion estimation from multiple video sequences. Our method minimizes the prediction error of the shape and motion estimates. Both problems then translate into a generic image registration task. The latter is entrusted to a global measure of image similarity, chosen depending on imaging conditions and scene properties. Rather than integrating a matching measure computed independently at each surface point, our approach computes a global image-based matching score between the input images and the predicted images. The matching process fully handles projective distortion and partial occlusions. Neighborhood as well as global intensity information can be exploited to improve the robustness to appearance changes due to non-Lambertian materials and illumination changes, without any approximation of shape, motion or visibility. Moreover, our approach results in a simpler, more flexible, and more efficient implementation than in existing methods. The computation time on large datasets does not exceed thirty minutes on a standard workstation. Finally, our method is compliant with a hardware implementation with graphics processor units. Our stereovision algorithm yields very good results on a variety of datasets including specularities and translucency. We have successfully tested our motion estimation algorithm on a very challenging multi-view video sequence of a non-rigid scene. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.  相似文献   
556.
557.
Maneuvrier  A.  Ceyte  H.  Renaud  P.  Morello  R.  Fleury  P.  Decker  L. M. 《Virtual Reality》2023,27(2):849-861
Virtual Reality - This study aimed to compare a neuropsychological test tapping into executive control function, the Wisconsin Card Sorting Test (WCST), performed in either traditional...  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