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   257篇
  免费   10篇
  国内免费   2篇
电工技术   5篇
化学工业   46篇
金属工艺   4篇
建筑科学   11篇
矿业工程   1篇
能源动力   8篇
轻工业   23篇
水利工程   1篇
石油天然气   3篇
无线电   66篇
一般工业技术   48篇
冶金工业   30篇
原子能技术   1篇
自动化技术   22篇
  2024年   1篇
  2022年   5篇
  2021年   2篇
  2020年   7篇
  2019年   6篇
  2018年   4篇
  2017年   3篇
  2016年   10篇
  2015年   6篇
  2014年   6篇
  2013年   8篇
  2012年   5篇
  2011年   11篇
  2010年   8篇
  2009年   14篇
  2008年   7篇
  2007年   13篇
  2006年   9篇
  2005年   22篇
  2004年   14篇
  2003年   13篇
  2002年   8篇
  2001年   5篇
  2000年   9篇
  1999年   5篇
  1998年   17篇
  1997年   11篇
  1996年   1篇
  1995年   6篇
  1994年   2篇
  1992年   4篇
  1991年   3篇
  1987年   1篇
  1986年   2篇
  1985年   1篇
  1984年   1篇
  1983年   2篇
  1982年   1篇
  1980年   2篇
  1979年   2篇
  1977年   1篇
  1976年   4篇
  1973年   1篇
  1968年   2篇
  1967年   1篇
  1966年   1篇
  1963年   1篇
  1961年   1篇
排序方式: 共有269条查询结果,搜索用时 15 毫秒
171.
The production of malt whisky involves the mashing of barley malt, followed by the fermentation of the resulting wort without further treatment. While this process has many parallels to the production of an all‐malt beer, one of the main differentiating steps during substrate preparation is the inclusion of a boiling step for the wort in the production of beer. Other than the destructive action of the boiling process on microorganisms, the boiling also destroys all malt enzyme activity. Since a typical whisky wash is not boiled it carries through a certain proportion of microbial activity associated with the malt, but more importantly it retains some enzyme activity that has been activated during the malting and mashing processes. The changes in sugars and dextrins during both mashing and fermentation of the resulting wash were investigated. Evidence of the continuous amylolytic activity during an unboiled, all‐malt wash fermentation is shown; while no ongoing amylolytic activity could be deduced during the fermentation of a boiled all‐malt wort. Furthermore, the data suggests that the amylolytic activity during mashing and fermentation are different with regards to α‐amylase action linked to its multiple‐attack action pattern as a function of substrate conformation, temperature, and effectiveness of potential hydrolytic events.  相似文献   
172.
The yeast vacuole has been shown to exhibit morphological responses to environmental conditions when exposed to worts of different gravity during fermentation. Marked effects of high gravity wort (20° Plato) on yeast morphology compared to more conventional wort gravity (12° Plato) were observed. High gravity worts caused vacuolar enlargement compared to conventional gravity wort. These results suggested that yeast cells experienced severe alterations with the vacuolar tonoplast when exposed to high osmotic pressure and elevated levels of ethanol.  相似文献   
173.
Data-driven science and technology have helped achieve meaningful technological advancements in areas such as materials/drug discovery and health care, but efforts to apply high-end data science algorithms to the areas of glass and ceramics are still limited. Many glass and ceramic researchers are interested in enhancing their work by using more data and data analytics to develop better functional materials more efficiently. Simultaneously, the data science community is looking for a way to access materials data resources to test and validate their advanced computational learning algorithms. To address this issue, The American Ceramic Society (ACerS) convened a Glass and Ceramic Data Science Workshop in February 2018, sponsored by the National Institute for Standards and Technology (NIST) Advanced Manufacturing Technologies (AMTech) program. The workshop brought together a select group of leaders in the data science, informatics, and glass and ceramics communities, ACerS, and Nexight Group to identify the greatest opportunities and mechanisms for facilitating increased collaboration and coordination between these communities. This article summarizes workshop discussions about the current challenges that limit interactions and collaboration between the glass and ceramic and data science communities, opportunities for a coordinated approach that leverages existing knowledge in both communities, and a clear path toward the enhanced use of data science technologies for functional glass and ceramic research and development.  相似文献   
174.
Multicomponent pyrochlore solid solutions with and without uranium incorporation were fabricated and their thermal-mechanical properties were characterized. Multicomponent pyrochlore solid solutions without uranium exhibit comparable thermal conductivity and higher mechanical strength compared to baseline single component rare-earth titanate pyrochlore (A2Ti2O7). Uranium incorporation reduces hardness as compared with single component compositions. High entropy pyrochlore with uranium displays the highest thermal conductivity within multicomponent pyrochlore solid solutions with significantly better mechanical properties than UO2. The measured thermal conductivity correlates well with A-site cation mixing entropy and a modified size disorder parameter, and thus the size disorder and mixing entropy could be good indicators for predicting thermal conductivity of multicomponent pyrochlore solid solutions. This work opens up the possibility of designing multicomponent oxide solid solutions by controlling their chemical disorder/mixing entropy to achieve acceptable thermal-mechanical properties, desired radiation and corrosion performance for potential nuclear waste form and inert matrix fuel applications.  相似文献   
175.
The transport of hydrated ions through narrow pores is important for a number of processes such as the desalination and filtration of water and the conductance of ions through biological channels. Here, molecular dynamics simulations are used to systematically examine the transport of anionic drinking water contaminants (fluoride, chloride, nitrate, and nitrite) through pores ranging in effective radius from 2.8 to 6.5 Å to elucidate the role of hydration in excluding these species during nanofiltration. Bulk hydration properties (hydrated size and coordination number) are determined for comparison with the situations inside the pores. Free energy profiles for ion transport through the pores show energy barriers depend on pore size, ion type, and membrane surface charge and that the selectivity sequence can change depending on the pore size. Ion coordination numbers along the trajectory showed that partial dehydration of the transported ion is the main contribution to the energy barriers. Ion transport is greatly hindered when the effective pore radius is smaller than the hydrated radius, as the ion has to lose some associated water molecules to enter the pore. Small energy barriers are still observed when pore sizes are larger than the hydrated radius due to re‐orientation of the hydration shell or the loss of more distant water. These results demonstrate the importance of ion dehydration in transport through narrow pores, which increases the current level of mechanistic understanding of membrane‐based desalination and transport in biological channels.  相似文献   
176.
塑造地域性的城市特色——以贵港市城市风貌规划为例   总被引:1,自引:0,他引:1  
陈玉  李响  覃初波 《规划师》2009,25(12):33-36
贵港城市风貌规划以地域特色的规划表达为重点,以主题演绎的设计手法为载体,对贵港地域性城市特色要素进行了演绎,以塑造“南国荷城”为核心内容,从分区规划、分项规划、风貌演绎等方面提出贵港城市风貌的控制措施和实施意向,并结合局部片区进行意向性城市设计,以使贵港的城市风貌得到较大的转变和提升。  相似文献   
177.
Haulage networks are vital to underground mining operations as they constitute the arteries through which blasted ore is transported to surface. In the sublevel stoping method and its variations, haulage drifts are excavated in advance near the ore block that will be mined out. Numerical modeling is a technique that is frequently employed to assess the redistribution of mining-induced stresses, and to compare the impact of different stope sequence scenarios on haulage network stability. In this study, typical geological settings in the Canadian Shield were replicated in a numerical model with a steeply-dipping tabular orebody striking EW. All other formations trended in the same direction except for two dykes on either side of the orebody with a WNW–ESE strike. Rock mass properties and in situ stress measurements from a case study mine were used to calibrate the model. Drifts and crosscuts were excavated in the footwall and two stope sequence scenarios – a diminishing pillar and a center-out one – were implemented in 24 mining stages. A combined volumetric-numerical analysis was conducted for two active levels by comparing the extent of unstable rock mass at each stage using shear, compressive, and tensile instability criteria. Comparisons were made between the orebody and the host rock, between the footwall and hanging wall, and between the two stope sequence scenarios. It was determined that in general, the center-out option provided a larger volume of instability with the shear criterion when compared to the diminishing pillar one (625,477 m3 compared to 586,774 m3 in the orebody; 588 m3 compared to 403 m3 in the host rock). However, the reverse was true for tensile (134,298 m3 compared to 128,834 m3 in the orebody; 91,347 m3 compared to 67,655 m3 in the host rock) instability where the diminishing pillar option had the more voluminous share.  相似文献   
178.
Cardiovascular disease is the leading cause of death in the United States and new treatment options are greatly needed. Oxidative stress is increased following myocardial infarction and levels of antioxidants decrease, causing imbalance that leads to dysfunction. Therapy involving catalase, the endogenous scavenger of hydrogen peroxide (H2O2), has been met with mixed results. When over-expressed in cardiomyocytes from birth, catalase improves function following injury. When expressed in the same cells in an inducible manner, catalase showed a time-dependent response with no acute benefit, but a chronic benefit due to altered remodeling. In myeloid cells, catalase over-expression reduced angiogenesis during hindlimb ischemia and prevented monocyte migration. In the present study, due to the large inflammatory response following infarction, we examined myeloid-specific catalase over-expression on post-infarct healing. We found a significant increase in catalase levels following infarction that led to a decrease in H2O2 levels, leading to improved acute function. This increase in function could be attributed to reduced infarct size and improved angiogenesis. Despite these initial improvements, there was no improvement in chronic function, likely due to increased fibrosis. These data combined with what has been previously shown underscore the need for temporal, cell-specific catalase delivery as a potential therapeutic option.  相似文献   
179.
Encapsulation of drugs within nanocarriers that selectively target malignant cells promises to mitigate side effects of conventional chemotherapy and to enable delivery of the unique drug combinations needed for personalized medicine. To realize this potential, however, targeted nanocarriers must simultaneously overcome multiple challenges, including specificity, stability and a high capacity for disparate cargos. Here we report porous nanoparticle-supported lipid bilayers (protocells) that synergistically combine properties of liposomes and nanoporous particles. Protocells modified with a targeting peptide that binds to human hepatocellular carcinoma exhibit a 10,000-fold greater affinity for human hepatocellular carcinoma than for hepatocytes, endothelial cells or immune cells. Furthermore, protocells can be loaded with combinations of therapeutic (drugs, small interfering RNA and toxins) and diagnostic (quantum dots) agents and modified to promote endosomal escape and nuclear accumulation of selected cargos. The enormous capacity of the high-surface-area nanoporous core combined with the enhanced targeting efficacy enabled by the fluid supported lipid bilayer enable a single protocell loaded with a drug cocktail to kill a drug-resistant human hepatocellular carcinoma cell, representing a 10(6)-fold improvement over comparable liposomes.  相似文献   
180.
In electrospray deposition, a precursor solution, composed of a solute material in a volatile carrier solvent, is atomized into a spray of charged microdroplets under the influence of a strong electric field. As the droplets are in-flight, the carrier solvent evaporates, leaving behind the solute material that can be delivered to a target surface to create a film. In this work, we employ electrospray deposition to create films of UV-photosensitive polyimide. Films were deposited using in-situ UV exposure, where the in-flight droplets and deposited material were exposed to UV during deposition. The characteristics of these films were compared to films exposed to UV only after deposition (referred to as post-UV exposure). The microstructure of the deposited films was notably different for the two exposure modes, in which the in-situ UV exposed films have a wavy/dimpled surface, compared to the flat and smooth surface of the post-UV exposed films. However, thermogravimetric analysis and Fourier transform infrared spectroscopy showed that the UV activation of the in-situ UV and post-UV exposed films was nearly identical. Breakdown testing was conducted to evaluate the dielectric strength of the films. Overall, the in-situ UV and post-UV exposed films exhibited similar breakdown strengths of approx. 430–450 V/μm. The use of in-situ UV exposure cuts in half the processing time for producing thin polyimide films.  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