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   747986篇
  免费   9095篇
  国内免费   2199篇
电工技术   13595篇
综合类   956篇
化学工业   115712篇
金属工艺   30142篇
机械仪表   23455篇
建筑科学   17140篇
矿业工程   5092篇
能源动力   19395篇
轻工业   60455篇
水利工程   8849篇
石油天然气   17938篇
武器工业   76篇
无线电   81843篇
一般工业技术   151690篇
冶金工业   131868篇
原子能技术   18537篇
自动化技术   62537篇
  2021年   6782篇
  2019年   6444篇
  2018年   11139篇
  2017年   11370篇
  2016年   11912篇
  2015年   7573篇
  2014年   12805篇
  2013年   34130篇
  2012年   19972篇
  2011年   27160篇
  2010年   21678篇
  2009年   24390篇
  2008年   24759篇
  2007年   24481篇
  2006年   21176篇
  2005年   19386篇
  2004年   18803篇
  2003年   18333篇
  2002年   17719篇
  2001年   17304篇
  2000年   16481篇
  1999年   16636篇
  1998年   39167篇
  1997年   28315篇
  1996年   21925篇
  1995年   16899篇
  1994年   15120篇
  1993年   14942篇
  1992年   11352篇
  1991年   11004篇
  1990年   10740篇
  1989年   10490篇
  1988年   9987篇
  1987年   9043篇
  1986年   8872篇
  1985年   9940篇
  1984年   9068篇
  1983年   8592篇
  1982年   7804篇
  1981年   7914篇
  1980年   7654篇
  1979年   7584篇
  1978年   7537篇
  1977年   8309篇
  1976年   10557篇
  1975年   6666篇
  1974年   6412篇
  1973年   6481篇
  1972年   5524篇
  1971年   5078篇
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
121.
122.
123.
This study evaluated several physical and sensory parameters of different types of cheese available in the Polish market. The measurements of textural properties were conducted in an Instron universal testing machine, while the colour properties of cheeses were measured using a Minolta chromameter. The chemical composition was determined by means of the near‐infrared spectroscopy (NIRs). Moreover, a trained sensory panel was invited to assess the cheese texture‐related properties. Generally, cheeses with reduced fat content were characterised by higher hardness, adhesiveness, cohesiveness and elasticity. Texture‐related parameters of cheese with canola oil were comparable to that of most of full‐fat cheeses. The correlation analysis between physical and sensory attributes related to cheese textural properties indicated the potential applications of TPA, shear and penetration tests (= 0.766, = 0.75 and = 0.765, respectively) for the evaluation of sensory properties related to the hardness. Meanwhile, the elasticity of cheese obtained from sensory evaluation was strongly correlated with the elasticity determined from the shear test (= 0.722) and moderately correlated with the elasticity from penetration test (= 0.588), indicating a need to refine the method of penetration test. In addition, cheeses exhibited higher meltability during convection heating at 230 °C than microwave heating. The values of meltability for cheese with reduced fat content were lower than those of full‐fat cheese.  相似文献   
124.
Water Resources Management - A number of models have been developed to simulate seawater intrusion in coastal aquifers, which differ in the accuracy level and computational demands, based on the...  相似文献   
125.
126.
127.
128.
Lévy flights have gained prominence for analysis of animal movement. In a Lévy flight, step-lengths are drawn from a heavy-tailed distribution such as a power law (PL), and a large number of empirical demonstrations have been published. Others, however, have suggested that animal movement is ill fit by PL distributions or contend a state-switching process better explains apparent Lévy flight movement patterns. We used a mix of direct behavioural observations and GPS tracking to understand step-length patterns in females of two related butterflies. We initially found movement in one species (Euphydryas editha taylori) was best fit by a bounded PL, evidence of a Lévy flight, while the other (Euphydryas phaeton) was best fit by an exponential distribution. Subsequent analyses introduced additional candidate models and used behavioural observations to sort steps based on intraspecific interactions (interactions were rare in E. phaeton but common in E. e. taylori). These analyses showed a mixed-exponential is favoured over the bounded PL for E. e. taylori and that when step-lengths were sorted into states based on the influence of harassing conspecific males, both states were best fit by simple exponential distributions. The direct behavioural observations allowed us to infer the underlying behavioural mechanism is a state-switching process driven by intraspecific interactions rather than a Lévy flight.  相似文献   
129.
130.
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