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   260篇
  免费   16篇
  国内免费   6篇
电工技术   1篇
综合类   14篇
化学工业   17篇
机械仪表   4篇
建筑科学   24篇
能源动力   16篇
轻工业   124篇
水利工程   21篇
石油天然气   14篇
无线电   9篇
一般工业技术   8篇
冶金工业   12篇
原子能技术   3篇
自动化技术   15篇
  2024年   2篇
  2023年   2篇
  2022年   5篇
  2021年   8篇
  2020年   4篇
  2019年   4篇
  2018年   8篇
  2017年   8篇
  2016年   7篇
  2015年   8篇
  2014年   15篇
  2013年   15篇
  2012年   18篇
  2011年   24篇
  2010年   11篇
  2009年   22篇
  2008年   21篇
  2007年   7篇
  2006年   12篇
  2005年   6篇
  2004年   9篇
  2003年   6篇
  2002年   6篇
  2001年   8篇
  2000年   9篇
  1999年   2篇
  1998年   5篇
  1997年   3篇
  1996年   7篇
  1995年   6篇
  1994年   8篇
  1993年   2篇
  1988年   2篇
  1987年   1篇
  1985年   1篇
排序方式: 共有282条查询结果,搜索用时 750 毫秒
1.
Home ownership has been associated with health, social and economic benefits. However, a decline in ownership has been observed over the past decade in New Zealand. Minority groups, including Pacific people, have been disadvantaged in the housing sector. This study investigated housing tenure and the relationship between tenure and health among mothers of a birth cohort of Pacific children in New Zealand. Findings showed that most families lived in state or private rental accommodation with few (15.4 per cent) owning their own homes. Homeowners were more likely to be older, partnered and have higher incomes. Better mental health was observed for homeowners compared to renters. Findings can inform housing and public health policy for Pacific families.  相似文献   
2.
叠后高分辨率资料处理方法及应用效果   总被引:2,自引:0,他引:2  
高分辨率勘探是一项系统工程,它由多个环节组成。甚至叠后高发辨率资料处理也是由多个环节组成。本文介绍的叠后高分辨率资料处理流程主要包括Lp模自适应预测统计反褶积,高频成分补偿,振幅补偿及有色成分校正。文中还就处理流程中各种方法的合理组合,各种方法自身参数的合理选取作了试验和探讨,最后给出了处理实例。  相似文献   
3.
School psychologists are generally not provided with the knowledge and skills to address both educational and psychosocial issues of Asian American and Pacific Islander students. The present study is the first of its kind in examining 36 independent (i.e., demographic, social, cultural, psychological) variables in association with four school outcomes (i.e., grade point average, absences, suspensions, and school infractions) with a large sample of Caucasian, Filipino, Native Hawaiian, Japanese, mixed/non-Hawaiian, and "other" Hawai'i high school students (N = 2,833). Given the relatively unique sample in question and the sheer number of variables, an exploratory approach was utilized with the goal of determining the most robust independent variables, with the unique inclusion of Hawaiian cultural identification. A cross-validation technique was used, whereby stepwise regressions were performed for each of two cross-validation samples; only common variables were retained in a final stepwise model for each of the four school outcomes. The results indicated that, remarkably, substance use accounted for the most variance (i.e., 8.4% -16.1 %) in the four school measures. Further analyses detailed the relationship, including the finding that smoking cigarettes regularly, accounted for the most variance compared to the other five substance use items. Further research and implications of the findings are discussed, including the need for prevention and intervention programs that incorporate substance use as a component, both within and outside of school environments. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
4.
利用1951-2002年NCEP/NCAR再分析资料、CPC(气候预测中心)Nino3区海表温度序列和NOAA的ERSST资料,研究了ENSO与我国东部夏季雨型的相互关系及其年代际变化.结果表明:我国东部夏季雨型对ENSO事件的响应在1978年有一个明显的突变,在突变前,降水雨型与赤道东太平洋的海温为弱的负相关,而在突变后转为显著的正相关;滑动相关结果显示,近20 a是整个研究时段中二者相关性最强的时期;东亚夏季风和ENSO的相互关系在1978年也经历了一次明显的年代际变化,由弱的正相关转为显著的负相关.这可能是引起ENSO和夏季雨型异常关系年代际变化的原因.  相似文献   
5.
北太平洋涛动是北半球大气中一个显著的、南北向跷跷板式的低频振荡,其演变不仅直接影响北太平洋附近地区的天气和气候,甚至对整个北半球的环流异常、持续以及气候突变都有重要影响.文章综述了北太平洋涛动的时间演变特征、区域变化特征、常用计算方法、北太平洋涛动指数的定义以及它们对天气气候的影响,阐述了需要进一步解决的一些问题,指出了目前关于NPO的研究尚处于初级阶段,对NPO的研究还可以借鉴其他涛动中较为成熟的研究方式和方法.  相似文献   
6.
在研究北太平洋海温异常对黑龙江冰坝的影响中,从预测黑龙江上游冰坝需要出发,利用反映北太平洋海域表面温度变化的分布型指数(该指数较好地表征出海温的年际变化特征及厄尔尼诺和拉尼娜事件),以及黑龙江上游水文站的封江水位距平构建了该站的冰坝预报模型,该模型可以较好地预测出黑龙江上游冰坝,实际预测结果表明,该方法是可行的,在冰坝预报中可以发挥重要作用。  相似文献   
7.
Bullfrogs (Rana catesbeiana), native to eastern North America, were introduced into Oregon in the 1930's. Bullfrogs are highly efficient predators that are known to eat a variety of prey including other amphibians. In laboratory experiments, we investigated whether juvenile Pacific treefrogs (Hyla regilla) recognize adult bullfrogs as a predatory threat. The ability of prey animals to acquire recognition of an introduced predator has important implications for survival of the prey. We found that treefrogs from a population that co-occurred with bullfrogs showed a strong avoidance of chemical cues of bullfrogs. In contrast, treefrogs from a population that did not co-occur with bullfrogs, did not respond to the bullfrog cues. Additional experiments showed that both populations of treefrogs use chemical cues to mediate predation risk. Treefrogs from both populations avoided chemical alarm cues from injured conspecifics.  相似文献   
8.
9.
Physicochemical properties and quality of Pacific white shrimp (Litopenaeus vannamei) treated with alkaline soaking solution (ASS; 0.75% NaOH with 2.5% NaCl) containing 3% monosodium glutamate (MSG), pH 11.5 (ASS+3% MSG) were investigated, in comparison with those treated with mixed phosphates or ASS alone. Muscle proteins underwent conformational changes as evidenced by the shift of Tmax to the lower temperature and the increased negative charge when treated with ASS+3% MSG. This coincided with the higher moisture and NaCl contents (P < 0.05). Such a treatment led to the pronounced swelling of muscle fibrils as visualised by scanning electron microscope. Highest likeness score for all attributes except for flavour was observed in sample treated with ASS+3% MSG. Slightly fishy odour in the treated sample was associated with higher abundance of volatile compounds, especially alcohol and aldehyde. Thus, ASS+3% MSG could be used as the replacer of phosphate and bicarbonate for shrimp processing.  相似文献   
10.
Lipids from cephalothorax and hepatopancreas of Pacific white shrimp (Litopenaeus vannamei) stored in ice for up to 6 days were extracted and characterised. The extraction yields of lipids from hepatopancreas (10.65–12.64%) were higher than those from cephalothorax (2.59–2.88%). However, no changes in the extraction yield were observed during the storage (p > 0.05). The carotenoid contents of lipids from cephalothorax and hepatopancreas slightly increased within the first 2 and 4 days of iced storage (p < 0.05), respectively, but decreased thereafter (p < 0.05). With increasing storage time, a progressive formation of hydroperoxide was found as evidenced by the increase in the absorbance band at 3600–3200 cm−1 in Fourier transform infrared (FTIR) spectra, and increased peroxide values (PVs) (p < 0.05). The increases in thiobarbituric acid reactive substances (TBARS), p-anisidine value (AnV) and free fatty acid (FFA) content of lipids were noticeable when iced storage time increased (p < 0.05). Those changes indicated that lipid oxidation and hydrolysis occurred in both samples. Phospholipids (PL) were the major components in lipids from cephalothorax (82.51% of total lipids). Nevertheless, lipids from hepatopancreas contained triglyceride (TG) and PL as the dominant components (45.35% and 38.03% of total lipids, respectively). A decrease in the TG content with a concomitant increase in free fatty acid was observed at the end of storage (day 6) (p < 0.05). Decreases in unsaturated fatty acids, especially eicosapentaenoic acid (EPA; C20:5(n-3)) and docosahexaenoic acid (DHA; C22:6(n-3)) were noticeable at day 6 of storage (p < 0.05). Thus, the extended storage time resulted in the enhanced deterioration of extracted lipids.  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