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   48456篇
  免费   5499篇
  国内免费   3026篇
电工技术   3115篇
技术理论   1篇
综合类   3898篇
化学工业   7517篇
金属工艺   2805篇
机械仪表   3186篇
建筑科学   3456篇
矿业工程   1279篇
能源动力   1148篇
轻工业   5321篇
水利工程   1124篇
石油天然气   1978篇
武器工业   464篇
无线电   5714篇
一般工业技术   5563篇
冶金工业   1816篇
原子能技术   583篇
自动化技术   8013篇
  2024年   125篇
  2023年   758篇
  2022年   1402篇
  2021年   1969篇
  2020年   1524篇
  2019年   1331篇
  2018年   1515篇
  2017年   1582篇
  2016年   1520篇
  2015年   2127篇
  2014年   2673篇
  2013年   3276篇
  2012年   3771篇
  2011年   4202篇
  2010年   3809篇
  2009年   3744篇
  2008年   3590篇
  2007年   3361篇
  2006年   3079篇
  2005年   2545篇
  2004年   1822篇
  2003年   1391篇
  2002年   1319篇
  2001年   1102篇
  2000年   817篇
  1999年   615篇
  1998年   374篇
  1997年   313篇
  1996年   263篇
  1995年   207篇
  1994年   176篇
  1993年   151篇
  1992年   108篇
  1991年   89篇
  1990年   62篇
  1989年   52篇
  1988年   36篇
  1987年   33篇
  1986年   26篇
  1985年   11篇
  1984年   10篇
  1983年   9篇
  1982年   16篇
  1980年   6篇
  1979年   11篇
  1978年   9篇
  1977年   10篇
  1976年   13篇
  1975年   9篇
  1970年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Applied Composite Materials - The paper presents a study on the ballistic performance of 3D woven wadded through-the-thickness angle-interlock fabrics (TTAI) fabric reinforced composites. Their...  相似文献   
2.
IEC61508等标准提出了几种计算安全仪表系统需求时平均失效概率的方法,但是,对于具有冗余配置的复杂系统,随着组件数量的增加,系统的中间状态数量快速增长,用户难以构建马尔可夫模型,即便借助计算机来建模运算也较为耗时。提出了一种同型“K oo N”简并状态的马尔可夫建模的通用方法,首先是根据降级状态进行判断,将符合条件的状态进行简并,然后对标记为危险失效状态的概率进行计算。通过严格的理论推导,该简并状态方法可以在不损失精度的前提下简化马尔可夫建模。  相似文献   
3.
4.
5.
The structural diversity of polyphenols and the inherent limitations of current extraction techniques pose a challenge to extract polyphenols using a simple and green method. Hence, in this study, a method was developed to simultaneously fractionate multiple classes of polyphenols by only varying ethanol-water solutions. Honeybush tea, which is rich in polyphenols, was selected as a model for this study. Solvent extraction followed by solid-phase extraction (SPE) was developed to obtain a polyphenol-rich fraction from six honeybush samples. Based on a gradient elution programme (10%, 30%, 50%, 70% and 90% (v/v) ethanol-water solution) of SPE, the Strata X cartridge showed a better recovery of most targeted polyphenols under 0.9 mL of the drying volume and 1 mL min−1 of the dispensing speed. The elution programme for fractionating most polyphenols was as follows: single elution with 50% ethanol, followed by twice elution with 70% ethanol. The antioxidant capacity was used to analyse the differences among the polyphenol-rich fractions from six honeybush samples. Principal component analysis (PCA) revealed that unfermented C. genistoides (GG) has the greatest antioxidant capacity among the honeybush species studied. Additionally, mangiferin, isomangiferin and vicenin-2 were the main contributors to the antioxidant capacity in six honeybush fractions according to the correlation study.  相似文献   
6.
7.
Feng  Yingrui  Hu  Kang  Zhang  Min  Ding  Wei  Kong  Xiangkai  Sheng  Zhigao  Liu  Qiangchun 《Journal of Materials Science》2022,57(1):204-216
Journal of Materials Science - Rationally designing microwave absorption materials with highly efficient and tunable bandwidth is in great demand but remains a huge challenge. In this study,...  相似文献   
8.
Lin  Ruijin  He  Yuanrong  Xu  Min 《Wireless Networks》2022,28(6):2733-2741
Wireless Networks - In order to improve the transmission stability of sensor networks, a sensitive data mining method based on Pan Boolean algebra is proposed. According to the output correctness,...  相似文献   
9.
The muon radiography imaging technique for high-atomic-number objects(Z) and large-volume objects via muon transmission imaging and muon multiple scattering imaging remains a popular topic in the field of radiation detection imaging. However, few imaging studies have been reported on low and medium Z objects at the centimeter scale. This paper presents an imaging system that consists of three layers of a position-sensitive detector and four plastic scintillation detectors. It acquires data by co...  相似文献   
10.
There has been a recent line of work to automatically detect the emotions of posts in social media. In literature, studies treat posts independently and detect their emotions separately. Different from previous studies, we explore the dependence among relevant posts via authors' backgrounds, since the authors with similar backgrounds, e.g., "gender", "location", tend to express similar emotions. However, personal attributes are not easy to obtain in most social media websites. Accordingly, we propose two approaches to determine personal attributes and capture personal attributes between different posts for emotion detection: the Joint Model with Personal Attention Mechanism (JPA) model is used to detect emotion and personal attributes jointly, and capture the attributes-aware words to connect similar people; the Neural Personal Discrimination (NPD) model is employed to determine the personal attributes from posts and connect the relevant posts with similar attributes for emotion detection. Experimental results show the usefulness of personal attributes in emotion detection, and the effectiveness of the proposed JPA and NPD approaches in capturing personal attributes over the state-of-the-art statistic and neural models.  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