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   415096篇
  免费   5737篇
  国内免费   1479篇
电工技术   6953篇
综合类   2536篇
化学工业   59805篇
金属工艺   18243篇
机械仪表   16186篇
建筑科学   10958篇
矿业工程   2118篇
能源动力   9507篇
轻工业   33991篇
水利工程   4274篇
石油天然气   3932篇
武器工业   5篇
无线电   49231篇
一般工业技术   80685篇
冶金工业   60924篇
原子能技术   4902篇
自动化技术   58062篇
  2021年   2192篇
  2020年   1614篇
  2019年   2021篇
  2018年   22858篇
  2017年   22510篇
  2016年   15788篇
  2015年   3541篇
  2014年   4539篇
  2013年   13859篇
  2012年   12508篇
  2011年   26085篇
  2010年   22318篇
  2009年   20274篇
  2008年   21398篇
  2007年   23873篇
  2006年   9430篇
  2005年   12787篇
  2004年   10621篇
  2003年   10162篇
  2002年   8313篇
  2001年   7693篇
  2000年   6998篇
  1999年   7372篇
  1998年   17235篇
  1997年   12047篇
  1996年   9223篇
  1995年   7097篇
  1994年   6290篇
  1993年   6110篇
  1992年   4488篇
  1991年   4116篇
  1990年   4002篇
  1989年   3797篇
  1988年   3652篇
  1987年   3021篇
  1986年   2859篇
  1985年   3623篇
  1984年   3264篇
  1983年   2965篇
  1982年   2715篇
  1981年   2688篇
  1980年   2506篇
  1979年   2407篇
  1978年   2189篇
  1977年   2456篇
  1976年   3059篇
  1975年   1850篇
  1974年   1721篇
  1973年   1791篇
  1972年   1330篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Palmitoleic acid has been classified as an insulin-sensitizing lipokine, but evidence for this from human studies has been inconsistent. We hypothesized that this is related to either the types of samples or conditions under which samples are collected. We measured plasma palmitoleic acid and total free fatty acids (FFA) using ultra-performance liquid chromatography in blood samples collected from 34 adults under a variety of conditions. We collected duplicate samples of adipose (n = 10), FFA (n = 9), and very low density lipoprotein triacylglycerol (VLDL-TAG) (n = 7) to measure the palmitoleic acid as a percentage of total fatty acids. We tested whether the percentage of palmitoleic acid was correlated with insulin resistance, as measured by homeostatic model of insulin resistance (HOMA-IR). Adipose stearoyl-coenzyme A desaturase 1 (SCD-1) protein was measured by capillary Western blotting. FFA-palmitoleic acid percentage increased as a function of total FFA and was greater (p < 0.005) in females than males. Adipose palmitoleic acid percentage was greater in females than males (p < 0.001), as was adipose SCD-1. Palmitoleic acid was greater in femoral fat than in abdominal fat in both females and males (p < 0.001), and correlated positively with HOMA-IR only in females. The test–retest reliability values for percentage palmitoleic acid were 7 ± 10% for adipose, 24 ± 26% for VLDL, and 53 ± 31% for FFA. Because FFA-palmitoleic acid percentage varies as a function of total FFA, investigators should re-evaluate how palmitoleic acid data is presented. The positive relationship between adipose palmitoleic acid and HOMA-IR in females suggests that it is not a potent insulin-sensitizing lipokine in humans.  相似文献   
92.
93.
94.
The influence of the temperature gradient over the thickness of the cladding of a fuel element of a fast-neutron reactor on the migration of point defects formed in the cladding material due to neutron irradiation has been studied. It has been shown that, under the action of the temperature gradient, the flux of vacancies onto the inner surface of the cladding is higher than the flux of interstitial atoms, which leads to the formation of a specific concentration profile in the cladding with a vacancy-depleted zone near the inner surface. The experimental results on the spatial distribution of pores over the cladding thickness have been presented with which the data on the concentration profiles and vacancy fluxes have been compared.  相似文献   
95.
The Raman spectrum of water adsorbed on a metallic silver surface reveals an anomalously large shift of the vibrational frequency as compared to that in the bulk. The results are compared to data reported by other researchers, and possible interpretations of the observed phenomenon are discussed.  相似文献   
96.
The behavior of a superelastic Cu?14.2% Al?4%Ni single crystal in the case of high reversible strains under a longitudinal bending force was investigated. The effect of strain confinement along the crystal length was revealed and studied. The highest reversible strains (up to 10%) were shown to be confined within the central part of the bent crystal.  相似文献   
97.
X-ray diffraction analysis has been used to study the structure of the α-Zr matrix phase and the precipitation of β-Nb particles upon the annealing of a Zr–2.5% Nb deformed alloy. It has been found that the process of the precipitation of the strengthening β-Nb particles in the alloy is accompanied by the appearance of fields of elastic interphase deformations in the matrix α phase of the alloy due to the difference in the specific atomic volumes of the crystal structures of the matrix and precipitated phases. It has been shown experimentally that, as a result of the presence of interphase deformations in the alloy, the bcc crystal structure of the precipitating β-Nb particles undergoes monoclinic distortions.  相似文献   
98.
99.
The usage of cling wraps is emerging as an easy and cost-effective approach to protect fresh-cut fruits and vegetables from dust, whilst improving visual appeal on retail counters. This study focused on developing an alternate, protein-based packaging material as a food grade cling wrap for food packaging applications. Zein-based cling wraps were produced, and their physical and mechanical characteristics were evaluated and compared with conventionally used chitosan biopolymer films and commercial synthetic polymer films. Antioxidant potential of the prepared films was studied, and the effectiveness of the developed films as anti-browning cling wraps was evaluated using studies conducted on fresh-cut apple slices at ambient conditions. Anti-browning effects were in par with polymeric counterparts; however, zein cling wraps could better prevent weight loss in apple slices. Zein-based films can be adopted as biodegradable food grade cling wraps as an alternative to chitosan and synthetic polymeric materials.  相似文献   
100.
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