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   1540篇
  免费   6篇
  国内免费   1篇
电工技术   1篇
化学工业   43篇
金属工艺   7篇
机械仪表   8篇
建筑科学   13篇
能源动力   5篇
轻工业   17篇
水利工程   4篇
石油天然气   1篇
无线电   10篇
一般工业技术   44篇
冶金工业   1370篇
原子能技术   2篇
自动化技术   22篇
  2019年   2篇
  2018年   8篇
  2017年   6篇
  2016年   2篇
  2015年   4篇
  2014年   5篇
  2013年   10篇
  2012年   8篇
  2011年   9篇
  2010年   10篇
  2008年   11篇
  2007年   2篇
  2006年   9篇
  2005年   10篇
  2004年   5篇
  2003年   7篇
  2002年   5篇
  2001年   3篇
  2000年   4篇
  1999年   46篇
  1998年   425篇
  1997年   227篇
  1996年   153篇
  1995年   90篇
  1994年   70篇
  1993年   89篇
  1992年   12篇
  1991年   20篇
  1990年   21篇
  1989年   17篇
  1988年   29篇
  1987年   23篇
  1986年   14篇
  1985年   13篇
  1984年   3篇
  1983年   8篇
  1982年   11篇
  1981年   11篇
  1980年   15篇
  1979年   2篇
  1978年   7篇
  1977年   27篇
  1976年   61篇
  1975年   4篇
  1974年   2篇
  1973年   2篇
  1972年   2篇
  1971年   2篇
  1966年   3篇
  1929年   2篇
排序方式: 共有1547条查询结果,搜索用时 62 毫秒
91.
Here I review personality research in one non-Western culture, the Philippines. Reports from diverse cultures remind one that personality findings reflect the cultural setting from which they emerge, lead to "cross-indigenous" comparisons between alternative cultural perspectives, and suggest hypotheses about cultural generality versus uniqueness. I illustrate the impact of cultural context on topics studied; on the applicability of concepts, methods, and measures; and on the practice of psychology by using the Philippine case. I also discuss issues regarding the cultural universality versus uniqueness of Filipino personality concepts, current efforts toward developing an indigenous Philippine psychology, and the language issue. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
92.
93.
94.
We have measured the increase in damping of second sound in 0.1% and 0.05%3He-4He solutions upon application of a magnetic field of 10 T. The increase is caused by changes in the thermal conductivity and viscosity of the mixture as the system becomes spin polarized. We show how to fit the data for the viscosity in zero-field to obtain an estimate of the interaction between the3He quasiparticles. It is then possible to predict the viscosity in a field of 10 T using the calculation of Hampson et al. The data agree with the theory to within 2%.  相似文献   
95.
Simulations are becoming an increasingly important part of the weapon design cycle allowing the investigation of more parameters in warhead concepts. This relies on a thorough verification and validation process for the simulation tools, which enables a cost effective approach to down-selecting concepts for full-scale experiments. A key factor in this process applied to the design of warheads to defeat hard (structural) targets is the development of truly physically based material models for geological materials where constants are either derived or measured. The paper describes this general approach and highlights aspects of its initial application to kinetic energy (KE) penetration and suggests areas for future investigation.  相似文献   
96.
We have studied the wavelength dependence of the two‐photon excitation efficiency for a number of common UV excitable fluorescent dyes; the nuclear stains DAPI, Hoechst and SYTOX Green, chitin‐ and cellulose‐staining dye Calcofluor White and Alexa Fluor 350, in the visible and near‐infrared wavelength range (540–800 nm). For several of the dyes, we observe a substantial increase in the fluorescence emission intensity for shorter excitation wavelengths than the 680 nm which is the shortest wavelength usually available for two‐photon microscopy. We also find that although the rate of photo‐bleaching increases at shorter wavelengths, it is still possible to acquire many images with higher fluorescence intensity. This is particularly useful for applications where the aim is to image the structure, rather than monitoring changes in emission intensity over extended periods of time. We measure the excitation spectrum when the dyes are used to stain biological specimens to get a more accurate representation of the spectrum of the dye in a cell environment as compared to solution‐based measurements.  相似文献   
97.
Journal of Porous Materials - Open-cell polyurethane foams have been investigated for various filtration applications to treat industrial byproducts and waste water. Flow-related morphological...  相似文献   
98.
99.
OBJECTIVES: This study assessed the influence of public policies on the immunization status of 2-year old children in the United States. METHODS: Up-to-dateness for the primary immunization series was assessed in a national sample of 8100 children from the 1988 National Maternal and Infant Health Survey and its 1991 Longitudinal Follow-Up. RESULTS: Documented immunization rates of this sample were 33% for poor children and 44% for others. More widespread Medicated coverage was associated with greater likelihood of up-to-dateness among poor children. Up-to-dateness was more likely for poor children with public rather than private sources of routine pediatric care, but all children living in states where most immunizations were delivered in the public sector were less likely to be up to date. Poor children in state with partial vaccine replacement programs were less likely to be up to date than those in free-market purchase states. CONCLUSIONS: While state policies can enhance immunization delivery for poor children, heavy reliance on public sector immunization does not ensure timely receipt of vaccines. Public- and private-sector collaboration is necessary to protect children from vaccine-preventable diseases.  相似文献   
100.
Osteogenesis imperfecta (OI), a heritable disease caused by molecular defects in type I collagen, is characterized by skeletal deformities and brittle bones. The heterozygous and homozygous oim mice (oim/+ and oim/oim) exhibit mild and severe OI phenotypes, respectively, serving as controlled animal models of this disease. In the current study, bone geometry, mechanics, and material properties of 1-year-old mice were evaluated to determine factors that influence the severity of phenotype in OI. The oim/oim mice exhibited significantly smaller body size, femur length, and moment of area compared with oim/+ and wild-type (+/+) controls. The oim/oim femur mechanical properties of failure torque and stiffness were 40% and 30%, respectively, of the +/+ values, and 53% and 36% of the oim/+ values. Collagen content was reduced by 20% in the oim/oim compared with +/+ bone and tended to be intermediate to these values for the oim/+. Mineral content was not significantly different between the oim/oim and +/+ bones. However, the oim/oim ash content was significantly reduced compared with that of the oim/+. Mineral carbonate content was reduced by 23% in the oim/oim bone compared with controls. Mineral crystallinity was reduced in the oim/oim and oim/+ bone compared with controls. Overall, for the majority of parameters examined (geometrical, mechanical, and material), the oim/+ values were intermediate to those of the oim/oim and +/+, a finding that parallels the phenotypes of the mice. This provides evidence that specific material properties, such as mineral crystallinity and collagen content, are indicative and possibly predictive of bone fragility in this mouse model, and by analogy in human OI.  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