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   566750篇
  免费   6736篇
  国内免费   1004篇
电工技术   10511篇
综合类   466篇
化学工业   90142篇
金属工艺   23337篇
机械仪表   18499篇
建筑科学   12557篇
矿业工程   4313篇
能源动力   14438篇
轻工业   45827篇
水利工程   6958篇
石油天然气   14961篇
武器工业   39篇
无线电   60317篇
一般工业技术   116304篇
冶金工业   95656篇
原子能技术   14684篇
自动化技术   45481篇
  2021年   5500篇
  2019年   5282篇
  2018年   9217篇
  2017年   9419篇
  2016年   9847篇
  2015年   6035篇
  2014年   10253篇
  2013年   26131篇
  2012年   15807篇
  2011年   21129篇
  2010年   16992篇
  2009年   18839篇
  2008年   19086篇
  2007年   18790篇
  2006年   16299篇
  2005年   14755篇
  2004年   14021篇
  2003年   13699篇
  2002年   13254篇
  2001年   12852篇
  2000年   12335篇
  1999年   12021篇
  1998年   27665篇
  1997年   20052篇
  1996年   15633篇
  1995年   12010篇
  1994年   10867篇
  1993年   10619篇
  1992年   8335篇
  1991年   8104篇
  1990年   7994篇
  1989年   7765篇
  1988年   7481篇
  1987年   6750篇
  1986年   6535篇
  1985年   7392篇
  1984年   6703篇
  1983年   6438篇
  1982年   5780篇
  1981年   5897篇
  1980年   5633篇
  1979年   5737篇
  1978年   5663篇
  1977年   6180篇
  1976年   7686篇
  1975年   5109篇
  1974年   4905篇
  1973年   4983篇
  1972年   4279篇
  1971年   4038篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
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   
102.
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   
103.
104.
105.
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   
106.
107.
108.
109.
110.
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