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   3254篇
  免费   189篇
  国内免费   3篇
电工技术   27篇
综合类   3篇
化学工业   694篇
金属工艺   48篇
机械仪表   49篇
建筑科学   269篇
矿业工程   2篇
能源动力   158篇
轻工业   724篇
水利工程   21篇
石油天然气   11篇
无线电   156篇
一般工业技术   638篇
冶金工业   103篇
原子能技术   17篇
自动化技术   526篇
  2023年   29篇
  2022年   19篇
  2021年   50篇
  2020年   40篇
  2019年   58篇
  2018年   132篇
  2017年   118篇
  2016年   118篇
  2015年   115篇
  2014年   127篇
  2013年   225篇
  2012年   172篇
  2011年   223篇
  2010年   170篇
  2009年   145篇
  2008年   170篇
  2007年   180篇
  2006年   180篇
  2005年   111篇
  2004年   97篇
  2003年   120篇
  2002年   101篇
  2001年   74篇
  2000年   67篇
  1999年   59篇
  1998年   48篇
  1997年   38篇
  1996年   35篇
  1995年   33篇
  1994年   30篇
  1993年   22篇
  1992年   18篇
  1991年   14篇
  1990年   18篇
  1989年   11篇
  1987年   9篇
  1986年   15篇
  1985年   23篇
  1984年   34篇
  1983年   27篇
  1982年   14篇
  1981年   21篇
  1980年   25篇
  1979年   15篇
  1978年   9篇
  1977年   12篇
  1976年   14篇
  1975年   9篇
  1974年   12篇
  1973年   14篇
排序方式: 共有3446条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
Hams from Landrace, Duroc and Hampshire pigs slaughtered at ages 6, 7.5 and 9 months were processed to generate Norwegian Parma‐style hams. Lipid contents and the compositions of fatty acid classes (ΣSFA, ΣMUFA, ΣPUFA) within neutral lipids, phospholipids and free fatty acids were determined. Small differences in lipid degradation and composition of the classes were revealed. However, significant sensory differences related to lipids were observed. Breed was more important than age. Dry‐cured Hampshire hams gave a more intense mature odour that may be associated with higher overall lipid degradation. Unexpectedly, these hams also demonstrated high juiciness and tenderness, which could be related to the melting characteristics of the fat. Dry‐cured Duroc hams showed a higher susceptibility towards rancidity, presumably associated with preferential oxidation of n‐6 fatty acids relative to C18:1 n‐9. Dry‐cured Landrace hams showed the lowest juiciness and tenderness, likely due to their lower fat content (marbling).  相似文献   
5.
 A cell vertex finite volume method for the solution of steady compressible turbulent flow problems on unstructured hybrid meshes of tetrahedra, prisms, pyramids and hexahedra is described. These hybrid meshes are constructed by firstly discretising the computational domain using tetrahedral elements and then by merging certain tetrahedra. A one equation turbulence model is employed and the solution of the steady flow equations is obtained by explicit relaxation. The solution process is accelerated by the addition of a multigrid method, in which the coarse meshes are generated by agglomeration, and by parallelisation. The approach is shown to be effective for the simulation of a number of 3D flows of current practical interest. Sponsored by The Research Council of Norway, project number 125676/410 Dedicated to the memory of Prof. Mike Crisfield, a respected colleague  相似文献   
6.
Intensive fertilizer use has led to nitrate contamination of groundwater in many areas. This article examines the possibility of removing nitrates through the construction of artificial wetlands. A pilot study conducted in Denmark has found that the method is effective and economical, at least for small waterworks, though further treatment is necessary before an acceptable microbiological water quality is attained.  相似文献   
7.
Summary Small oscillations of a rotating elasticum with a mass at the free end are investigated with Poincaré-Lindstedt series. It is shown that the mass moves on a figure-eight shaped curve in a direction determined by the sign of the angular velocity and hence that the Coriolis force influences the motion.  相似文献   
8.
The paper describes a new boundary-layer wind tunnel at the Danish Maritime Institute in Lyngby. The wind tunnel is of the open-circuit type and is integrated into a building raised for the purpose. The design was constrained by the need to provide a simulation of the atmospheric boundary layer (without thermal stratification) and alternatively a uniform flow without excessive turbulence.The wind tunnel has a working section of principal dimensions: length 20.8 m, width 2.6 m and height 1.8 m (adjustable from 1.8 to 2.3 m). The maximum wind speed in the working section when empty is about 26 m s?1.Data acquisition, analysis and instrumentation in relation to the new wind tunnel are discussed and, finally, an example of a simulated natural wind is presented.  相似文献   
9.
Working with survivors of political torture and war trauma can trigger strong emotional responses in the therapist. As more survivors seek treatment, it is essential to identify and develop robust support systems for therapists who help their clients confront nearly unspeakable experiences. The emotional reactions of 6 psychotherapists who worked with traumatized survivors in a refugee treatment center were explored. The psychotherapists' reactions were compared with those of therapists who worked in different treatment settings with other presenting problems. The results of the study show that the strong level of responsibility therapists feel for their traumatized clients may hide an emotional strain and may lead to burnout. Suggestions are offered for supporting therapists in this difficult but important work. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
10.
One important area of modern condensed matter research is the investigation of the nature of the superconducting cuprates. Much progress in this field has been obtained with the technique of neutron scattering. We here present a review of neutron scattering studies of the high-temperature superconductor La2?xSrxCuO4, performed at Risø National Laboratory. We review the work on the mapping of the incommensurate spin fluctuations, the investigation of the gap in the fluctuation spectrum, the magnetic properties of the vortices appearing in an applied field, and the quantum critical behaviour of the system. We discuss our findings in the light of results of neutron scattering from other groups, on other cuprate systems, and results from other experimental methods, e.g. NMR, μSR, STM, X-ray diffraction, and ARPES. We end with a discussion on the implications of the experimental results for the progress in the general understanding of high-temperature superconductivity. PACS numbers: 61.12.Ex, 74.20.Mn, 74.72.Dn, 75.25.+z, 78.70.Nx.  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