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   137221篇
  免费   21486篇
  国内免费   3598篇
电工技术   5923篇
技术理论   11篇
综合类   5732篇
化学工业   34027篇
金属工艺   5716篇
机械仪表   7041篇
建筑科学   9984篇
矿业工程   2545篇
能源动力   3737篇
轻工业   12654篇
水利工程   1987篇
石油天然气   5811篇
武器工业   594篇
无线电   18600篇
一般工业技术   23679篇
冶金工业   6022篇
原子能技术   979篇
自动化技术   17263篇
  2024年   282篇
  2023年   1548篇
  2022年   2257篇
  2021年   3836篇
  2020年   4167篇
  2019年   5380篇
  2018年   5614篇
  2017年   6231篇
  2016年   6405篇
  2015年   7318篇
  2014年   8448篇
  2013年   10595篇
  2012年   8789篇
  2011年   8754篇
  2010年   8337篇
  2009年   7975篇
  2008年   7334篇
  2007年   7022篇
  2006年   7083篇
  2005年   6188篇
  2004年   4650篇
  2003年   4355篇
  2002年   4086篇
  2001年   3687篇
  2000年   3760篇
  1999年   3471篇
  1998年   2751篇
  1997年   2220篇
  1996年   2023篇
  1995年   1676篇
  1994年   1403篇
  1993年   1012篇
  1992年   781篇
  1991年   623篇
  1990年   476篇
  1989年   413篇
  1988年   344篇
  1987年   198篇
  1986年   176篇
  1985年   116篇
  1984年   103篇
  1983年   68篇
  1982年   67篇
  1981年   59篇
  1980年   42篇
  1979年   36篇
  1978年   15篇
  1977年   35篇
  1976年   16篇
  1975年   15篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product.  相似文献   
43.
Hou  Jianhua  Ye  Jiantao 《Scientometrics》2020,124(2):1631-1662
Scientometrics - In traditional research, the application of quantitative measurement on the value and influence of uncited papers is not feasible owing to the lack of data. The rapid advancement...  相似文献   
44.
To improve the convertibility of reconfigurable manufacturing system (RMS), the concept of delayed reconfigurable manufacturing system (D-RMS) was proposed. RMS and D-RMS are both constructed around part family. However, D-RMS may suffer from ultra-long system problem with unacceptable idle machines using generic RMS part families. Besides, considering the complex basic system structure of D-RMS, machine selection of D-RMS should be addressed, including dedicated machine, flexible machine, and reconfigurable machine. Therefore, a system design method for D-RMS based on part family grouping and machine selection is proposed. Firstly, a part family grouping method is proposed for D-RMS that groups the parts with more former common operations into the same part family. The concept of longest relative position common operation subsequence (LPCS) is proposed. The similarity coefficient among the parts is calculated based on LPCS. The reciprocal value of the operation position of LPCS is adopted as the characteristic value. The average linkage clustering (ALC) algorithm is used to cluster the parts. Secondly, a machine selection method is proposed to complete the system design of D-RMS, including machine selection rules and the dividing point decision model. Finally, a case study is given to implement and verify the proposed system design method for D-RMS. The results show that the proposed system design method is effective, which can group parts with more former common operations into the same part family and select appropriate machine types.  相似文献   
45.
既有公共建筑能耗中,围护结构节能潜力巨大。以兰州某既有办公建筑为例,采用DeST-C软件模拟围护结构不同材料厚度、窗型,得出系列负荷,通过对数据分析、比较,得出如下结论:外墙外保温适宜材料为50mm的挤塑板,最大热负荷节能率为45.66%;屋面适宜保温材料为65mm的挤塑板,最大热负荷节能率为4.25%;外窗各个朝向全部更换玻璃,推荐选用内张膜中空玻璃(双膜),最大热负荷节能率为7.36%;单独更换南向外窗材料,推荐选用真空镀膜复合中空玻璃,最大热负荷节能率为1.78%。  相似文献   
46.
Lin  Haicheng  Huang  Wantong  Zhao  Kun  Qiao  Shuang  Liu  Zheng  Wu  Jian  Chen  Xi  Ji  Shuai-Hua 《Nano Research》2020,13(1):133-137
Nano Research - The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures. Combining the molecular beam...  相似文献   
47.
48.
49.
50.
Pinhão seed is an unconventional source of starch and the pines grow up in native forests of southern Latin America. In this study, pinhão starch was adjusted at 15, 20 and 25% moisture content and heated to 100, 110 and 120 °C for 1 h. A decrease in λ max (starch/iodine complex) was observed as a result of increase in temperature and moisture content of HMT. The ratio of crystalline to amorphous phase in pinhão starch was determined via Fourier transform infra red by taking 1045/1022 band ratio. A decrease in crystallinity occurred as a result of HMT. Polarised light microscopy indicated a loss of birefringence of starch granules under 120 °C at 25% moisture content. Granule size distribution was further confirmed via scanning electron microscopy which showed the HMT effects. These results increased the understanding on molecular and structural properties of HMT pinhão starch and broadened its food and nonfood industrial applications.  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