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   1912篇
  免费   121篇
  国内免费   47篇
电工技术   10篇
综合类   63篇
化学工业   43篇
金属工艺   123篇
机械仪表   268篇
建筑科学   156篇
矿业工程   11篇
能源动力   30篇
轻工业   17篇
水利工程   3篇
石油天然气   16篇
武器工业   6篇
无线电   134篇
一般工业技术   186篇
冶金工业   9篇
原子能技术   11篇
自动化技术   994篇
  2024年   2篇
  2023年   20篇
  2022年   15篇
  2021年   32篇
  2020年   32篇
  2019年   23篇
  2018年   24篇
  2017年   52篇
  2016年   63篇
  2015年   74篇
  2014年   113篇
  2013年   100篇
  2012年   95篇
  2011年   145篇
  2010年   90篇
  2009年   111篇
  2008年   113篇
  2007年   101篇
  2006年   86篇
  2005年   89篇
  2004年   79篇
  2003年   99篇
  2002年   64篇
  2001年   59篇
  2000年   53篇
  1999年   44篇
  1998年   39篇
  1997年   45篇
  1996年   29篇
  1995年   36篇
  1994年   32篇
  1993年   19篇
  1992年   19篇
  1991年   14篇
  1990年   5篇
  1989年   14篇
  1988年   7篇
  1987年   6篇
  1986年   8篇
  1985年   6篇
  1984年   7篇
  1983年   1篇
  1982年   5篇
  1981年   2篇
  1980年   1篇
  1979年   4篇
  1977年   1篇
  1975年   1篇
  1974年   1篇
排序方式: 共有2080条查询结果,搜索用时 15 毫秒
1.
The present paper proposes a new method for axis identification in discrete axially symmetrical geometric models. This method is based on-a-never-used-before property of the axially symmetrical surfaces for which the symmetry line of any section curve of the surface (or of a portion of it in the case of an incomplete axially symmetrical surface) always intersects the axis of symmetry of the surface. Thus the working principle of the method makes it very robust to local defectiveness, measurement noise and outliers.In order to compare it with the most cited methods presented in literature, several types of tests have been designed and performed. The robustness of those methods, on the one hand, has been evaluated by defining the Statistical Confidence Boundary at 1σ confidence level. The trueness of the method, on the other hand, has been evaluated on geometric models obtained by measuring real objects. The high robustness, which characterizes the proposed method, makes it particularly suitable for product geometric inspection where high accuracy is required.  相似文献   
2.
3.
Steel box sections are usually fabricated from flat plates which are welded at the corners. The welding process can introduce residual stresses and geometric imperfections into the sections which can influence their strength. For some thin-walled sections, large periodic geometric imperfections have been observed in manufactured sections. Subsequent investigations have indicated that the imperfections are in fact buckling deformations i.e. the box section has buckled due to welding residual stresses prior to any application of external load. The welding procedure and the behaviour of the box sections under load has been modelled using a finite element analysis that accounts for both geometric and material non-linearities. Tests have been carried out on box sections with a range of width to thickness ratios for the plate elements. Modelling has been shown to give good correlation with the test results. The conditions for buckling to take place as a result of the welding process have been established. A design method has been proposed.  相似文献   
4.
The draft Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) contains Cryptosporidium log-inactivation CT tables (ozone-in-water concentration [residual], “C” times contact time, T). Depending on water temperature, Cryptosporidium CT values that are listed are 15 to 25 times greater than CT values for equivalent Giardia log-inactivation credit. The elevated operating dose required for Cryptosporidium log-inactivation credit has the potential to increase disinfection by-product (DBP) formation (e.g., bromate). Calculating CT value accurately will minimize ozone dose, which will decrease operating cost and lower DBP formation, and at the same time maintain disinfection protection through implementation of scientifically based safety factors. Various methods are available for calculating CT value. The method chosen depends largely on the available information concerning ozone residual characteristics and hydrodynamic features of the ozone contactor, plus local regulatory requirements. Four methods are discussed in this paper. Each method can be used to calculate Giardia, virus, and Cryptosporidium log-inactivation credit.  相似文献   
5.
6.
Controllability of One Spin and Two Interacting Spins   总被引:1,自引:0,他引:1  
Mathematics of Control, Signals, and Systems - ?We consider the problem of steering control for the systems of one spin ½ particle and two interacting spin ½ particles in an...  相似文献   
7.
8.
用相干态的方法得到旋转磁场中自旋为j的粒子的态矢量的严格表达式,由此可计算相干态和叠加相干态的Abaronov-Anandan相位(AA相让).并具有清楚的物理图象.  相似文献   
9.
10.
This paper presents Bayes estimators for the reliability measures of the individual components in a multi-component systems in the presence of masked system life test data. The life time distributions of the system components are assumed to be geometric with different parameters. Two-sided Bayesian probability intervals of the parameters are also derived. Numerical simulation study is given in order to: (i) explain how one can apply the theoretical results obtained, (ii) study the influence of the sample size and masking level on the accuracy of point estimates.  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