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   255篇
  免费   26篇
  国内免费   1篇
电工技术   3篇
化学工业   79篇
金属工艺   2篇
机械仪表   9篇
建筑科学   19篇
能源动力   7篇
轻工业   47篇
水利工程   4篇
无线电   11篇
一般工业技术   46篇
冶金工业   26篇
原子能技术   3篇
自动化技术   26篇
  2024年   1篇
  2023年   5篇
  2022年   6篇
  2021年   33篇
  2020年   15篇
  2019年   10篇
  2018年   13篇
  2017年   11篇
  2016年   7篇
  2015年   9篇
  2014年   18篇
  2013年   8篇
  2012年   19篇
  2011年   18篇
  2010年   18篇
  2009年   16篇
  2008年   8篇
  2007年   9篇
  2006年   12篇
  2005年   7篇
  2004年   10篇
  2003年   6篇
  2002年   4篇
  2001年   3篇
  2000年   2篇
  1999年   3篇
  1998年   2篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1993年   1篇
  1992年   2篇
  1990年   1篇
  1988年   1篇
  1980年   1篇
排序方式: 共有282条查询结果,搜索用时 312 毫秒
101.
In this work, the solubility of carbon dioxide, CO2, in pentaerythritol tetraheptanoate (PEC7) and in pentaerythritol tetranonanoate (PEC9) has been performed from 283 to 348 K and pressures up to 7.5 MPa in an isochoric high-pressure gas solubility apparatus. The solubility values are very similar in terms of mole fractions of CO2 in both pentaerythritol esters. The experimental gas solubility data, together with those available in the literature for other CO2 + pentaerythritol tetraester systems, were satisfactorily correlated with the PC-SAFT equation of state. The average absolute deviations of the gas solubility correlations were less than 3.9% for all the systems. In addition, PC-SAFT model was applied in a semi-predictive manner: the pure component's molecular parameters and the binary interaction parameter optimized from solubility data were used to calculate the types of the phase diagram as well as the densities and excess molar volumes in broad temperature and pressure ranges. The results obtained show the robustness of the model and these parameters to calculate properties not included in the fitting procedure.  相似文献   
102.
The present study examined age and cultural differences in cognitive and affective components of subjective well-being. A sample of 188 American and Chinese young and older adults completed surveys measuring self-life satisfaction, perceived family's life satisfaction, positive affect, and negative affect. Across cultures, older adults reported lower negative affect than did young adults. Americans reported higher self-life satisfaction, perceived family's life satisfaction, and positive affect than did Chinese. In addition, perceived family's life satisfaction was more related to self-life satisfaction for Chinese than for Americans. Findings are discussed in light of socioemotional selectivity theory and theories on culture and self-construal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
103.
Perinatal hypoxic-ischemic (HI) brain injury, often in conjunction with an inflammatory insult, is the most common cause of death or disability in neonates. Therapeutic hypothermia (TH) is the standard of care for HI encephalopathy in term and near-term infants. However, TH may not always be available or efficacious, creating a need for novel or adjunctive neurotherapeutics. Using a near-term model of inflammation-sensitized HI brain injury in postnatal day (P) 17 ferrets, animals were randomized to either the control group (n = 43) or the HI-exposed groups: saline vehicle (Veh; n = 42), Ur (uridine monophosphate, n = 23), Epo (erythropoietin, n = 26), or TH (n = 24) to test their respective therapeutic effects. Motor development was assessed from P21 to P42 followed by analysis of cortical anatomy, ex vivo MRI, and neuropathology. HI animals took longer to complete the motor assessments compared to controls, which was exacerbated in the Ur group. Injury resulted in thinned white matter tracts and narrowed cortical sulci and gyri, which was mitigated in Epo-treated animals in addition to normalization of cortical neuropathology scores to control levels. TH and Epo treatment also resulted in region-specific improvements in diffusion parameters on ex vivo MRI; however, TH was not robustly neuroprotective in any behavioral or neuropathological outcome measures. Overall, Ur and TH did not provide meaningful neuroprotection after inflammation-sensitized HI brain injury in the ferret, and Ur appeared to worsen outcomes. By comparison, Epo appears to provide significant, though not complete, neuroprotection in this model.  相似文献   
104.
We consider two approaches to the stable marriage problem: proposal algorithms and describing the stable matching polytope using linear inequalities. We illuminate the relationship between the two approaches. Beginning with a set of linear inequalities that describe the stable matching polytope, we describe a process of refining the set of linear inequalities by eliminating redundant constraints and pruning the preference lists to eliminate unattainable assignments. We show that it is trivial to use the pruned preference lists to find the firm-optimal and worker-optimal stable matchings. We then describe a new procedure that combines a proposal algorithm and our refining process to find a stable matching that does not favor one group over the other. Finally, we apply our refining process to problems in which couples submit preferences over pairs of positions.  相似文献   
105.
The Human Leukocyte Antigen class I (HLA-I) system is an essential part of the immune system that is fundamental to the successful activation of cytotoxic lymphocytes, and an effective subsequent immune attack against both pathogen-infected and cancer cells. The importance of cytotoxic T cell activity and ability to detect foreign cancer-related antigenic peptides has recently been highlighted by the successful application of monoclonal antibody-based checkpoint inhibitors as novel immune therapies. Thus, there is an increased interest in fully characterising the repertoire of peptides that are being presented to cytotoxic CD8+ T cells by cancer cells. However, HLA-I is also known to be present on the surface of extracellular vesicles, which are released by most if not all cancer cells. Whilst the peptide ligandome presented by cell surface HLA class I molecules on cancer cells has been studied extensively, the ligandome of extracellular vesicles remains relatively poorly defined. Here, we will describe the current understanding of the HLA-I peptide ligandome and its role on cancer-derived extracellular vesicles, and evaluate the aspects of the system that have the potential to advance immune-based therapeutic approaches for the effective treatment of cancer.  相似文献   
106.
107.
Digestion of nutrients is an essential function of the newborn infant gut to allow growth and development and understanding infant digestive function is essential to optimize nutrition and oral drug delivery. Ethical considerations prohibit invasive in vivo trials and as a consequence in vitro assays are often conducted. However, the choice of in vitro model parameters are not supported by an exhaustive analysis of the literature and do not mimic precisely the digestive conditions of the infant. This review contains a compilation of the studies which characterized the gastroduodenal conditions in full-term or preterm infants of variable postnatal age from birth up to six months. Important data about healthy full-term infants are reported. The enzymatic (type of enzymes and level of activity) and nonenzymatic (milk-based diet, frequency of feeding, bile salt concentrations) conditions of digestion in infants are shown to differ significantly from those in adults. In addition, the interindividual and developmental variability of the digestive conditions in infants is also highlighted.  相似文献   
108.
Aim: The purpose of this review was to assess existing evidence on the effects of chronic dietary macronutrient composition on substrate oxidation during a fasted state in healthy and overweight subjects. Methods: A systematic review of studies was conducted across five databases. Studies were included if they were English language studies of human adults, ≥19 years, used indirect calorimetry (ventilated hood technique), specified dietary macronutrient composition, and measured substrate oxidation. Results: There was no evidence that variations of a typical, non-experimental diet influenced rate or ratio of substrate utilization, however there may be an upper and lower threshold for when macronutrient composition may directly alter preferences for fuel oxidation rates during a fasted state. Conclusion: This review indicates that macronutrient composition of a wide range of typical, non-experimental dietary fat and carbohydrate intakes has no effect on fasting substrate oxidation. This suggests that strict control of dietary intake prior to fasting indirect calorimetry measurements may be an unnecessary burden for study participants. Further research into the effects of long-term changes in isocaloric macronutrient shift is required.  相似文献   
109.
Search engines play a critical role in the diffusion of online information because they determine what content is easily visible to Web users. Major search engines, such as Google, Microsoft Live Search, and Yahoo!, provide two distinct types of results, organic and paid, each of which uses different mechanisms for selecting and ranking relevant Web pages. Using a third-party trust assurance program from BBB (Better Business Bureau) Online we find that vendors represented by websites in organic and paid results have varying reliability ratings. These ratings, based on overall customer experiences, may range from satisfactory to unsatisfactory. We empirically examine how vendors' reliability ratings from BBB Online are associated with cues (such as type of search result, relative price of a product, and number of sites selling the product) that can be observed or derived from organic and paid search results. Further, we apply a data mining technique to predict the vendors' BBB reliability ratings using those cues and achieve good performance.  相似文献   
110.
We produced case studies of fourteen families based on nine rounds of data collection during the period from June 2008 to October 2009. We focused on fourteen children who were three years old when our visits started and used an ecocultural approach to examine their experiences of learning and playing with technologies at home. The study describes i) which technologies children encounter at home, ii) how family practices influence children’s encounters with technology, and iii) what children are learning through their interactions with technology. We present a framework of four areas of learning that could be supported by technology: acquiring operational skills, extending knowledge and understanding of the world, developing dispositions to learn, and understanding the role of technology in everyday life.  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