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   854篇
  免费   45篇
  国内免费   4篇
电工技术   13篇
综合类   2篇
化学工业   181篇
金属工艺   15篇
机械仪表   20篇
建筑科学   20篇
能源动力   36篇
轻工业   53篇
水利工程   2篇
石油天然气   1篇
无线电   123篇
一般工业技术   160篇
冶金工业   101篇
原子能技术   1篇
自动化技术   175篇
  2024年   3篇
  2023年   13篇
  2022年   35篇
  2021年   58篇
  2020年   49篇
  2019年   46篇
  2018年   52篇
  2017年   49篇
  2016年   36篇
  2015年   33篇
  2014年   31篇
  2013年   60篇
  2012年   58篇
  2011年   53篇
  2010年   32篇
  2009年   36篇
  2008年   25篇
  2007年   20篇
  2006年   23篇
  2005年   23篇
  2004年   17篇
  2003年   18篇
  2002年   17篇
  2001年   6篇
  2000年   4篇
  1999年   6篇
  1998年   11篇
  1997年   4篇
  1996年   11篇
  1995年   8篇
  1994年   3篇
  1993年   6篇
  1992年   12篇
  1991年   5篇
  1990年   7篇
  1989年   2篇
  1988年   4篇
  1987年   9篇
  1986年   4篇
  1985年   5篇
  1982年   1篇
  1980年   2篇
  1979年   1篇
  1978年   2篇
  1977年   1篇
  1976年   2篇
排序方式: 共有903条查询结果,搜索用时 15 毫秒
91.
Chromium ferrocyanide gel shows a great affinity for Ag+, Cu2+, Tl+, Zn2+, Co2+, Cd2+, Mn2+ and Fe3+ and has been used to separate and recover some heavy metal ions viz. Tl+, Hg2+, Mg2+, Fe3+ etc. Some of these can be completely eluted from the columns of this exchanger material and the compound can be used to treat waste water rich in heavy metal ions.  相似文献   
92.
An instrumented data glove with a wireless interface provides convenient and natural human-computer interaction for people with speech or hearing impairments.  相似文献   
93.
Waste heat is generally dissipated from process water to atmospheric air in cooling towers. In the present study, a novel design is used to extract more amount of heat without any additional energy input by incorporating secondary ambient air in an induced draft wet cooling tower. In addition, more fresh air is induced in the tower from the rain zone, which increases the effectiveness at any value of the water to air flow rate (L/G ratio). Moreover, tower characteristics, range, and evaporation loss were also increased due to the novel design. It is noteworthy that secondary fresh air increases effectiveness, heat rejection, and tower characteristics by 10.12%, 19.65%, and 26.11%, respectively, and decreases approach by 16.32% at 0.55 L/G ratio, 44°C inlet water temperature, 29.7°C dry bulb temperature, and 18.4°C inlet air wet bulb temperature.  相似文献   
94.
Portlandite (Ca(OH)2; also known as calcium hydroxide or hydrated lime), an archetypal alkaline solid, interacts with carbon dioxide (CO2) via a classic acid–base “carbonation” reaction to produce a salt (calcium carbonate: CaCO3) that functions as a low-carbon cementation agent, and water. Herein, we revisit the effects of reaction temperature, relative humidity (RH), and CO2 concentration on the carbonation of portlandite in the form of finely divided particulates and compacted monoliths. Special focus is paid to uncover the influences of the moisture state (i.e., the presence of adsorbed and/or liquid water), moisture content and the surface area-to-volume ratio (sa/v, mm−1) of reactants on the extent of carbonation. In general, increasing RH more significantly impacts the rate and thermodynamics of carbonation reactions, leading to high(er) conversion regardless of prior exposure history. This mitigated the effects (if any) of allegedly denser, less porous carbonate surface layers formed at lower RH. In monolithic compacts, microstructural (i.e., mass-transfer) constraints particularly hindered the progress of carbonation due to pore blocking by liquid water in compacts with limited surface area to volume ratios. These mechanistic insights into portlandite's carbonation inform processing routes for the production of cementation agents that seek to utilize CO2 borne in dilute (≤30 mol%) post-combustion flue gas streams.  相似文献   
95.
96.
Biochar has been used as an environment-friendly enhancer to improve the hydraulic properties(e.g.suction and water retention) of soil.However,variations in densities alter the properties of the soil-biochar mix.Such density variations are observed in agriculture(loosely compacted) and engineering(densely compacted) applications.The influence of biochar amendment on gas permeability of soil has been barely investigated,especially for soil with diffe rent densities.The maj or obj ective of this study is to investigate the water retention capacity,and gas permeability of biochar-amended soil(BAS) with different biochar contents under varying degree of compaction(DOC) conditions.In-house produced novel biochar was mixed with the soil at different amendment rates(i.e.biochar contents of 0%,5% and 10%).All BAS samples were compacted at three DOCs(65%,80% and 95%) in polyvinyl chloride(PVC)tubes.Each soil column was subjected to drying-wetting cycles,during which soil suction,water content,and gas permeability were measured.A simplified theoretical framework for estimating the void ratio of BAS was proposed.The experimental results reveal that the addition of biochar significantly decreased gas permeability k_g as compared with that of bare soil(BS).However,the addition of 5%biochar is found to be optimum in decreasing kg with an increase of DOC(i.e.k_(g,65%) k_(g,80%) k_(g,95%)) at a relatively low suction range(200 kPa) because both biochar and compaction treatment reduce the connected pores.  相似文献   
97.
98.
The spin-transfer nano-oscillator(STNO) has recently acquired a huge amount of research interest, due to its promising easy tunability along with the miniature size. The output frequency control of an STNO through magnetic field and current has been examined almost to its full extent; however, there are issues that still need to be addressed. Here, we propose a novel way of voltage control of the output frequency of an STNO, and alongside reducing its power requirement.  相似文献   
99.
The addition of NaFeEDTA at only 5% of total iron to ferric pyrophosphate‐fortified Ultra Rice® increased the in vitro soluble iron ten‐fold. Ultra Rice® formulated with NaFeEDTA at 2–7% of total iron, or with Na2EDTA·2H2O at 0.5× the total iron equivalents, increased the soluble iron seven‐ to thirty‐fold. The colour of the batches was acceptable through 20 weeks at 21 °C, but colour stability needs to be evaluated under authentic storage conditions. Although only 34–46% of the initial vitamin A remained after extrusion, 18‐week storage at 30 °C/70% relative humidity, and simulated cooking, there were indications that losses could be decreased by raising the pH (to ~5) and/or using a better protected vitamin A ingredient. The enhancement of soluble iron afforded by low‐level NaFeEDTA or Na2EDTA·2H2O supplementation suggests that this fortification strategy may merit further study as a means of increasing absorbable iron in Ultra Rice®.  相似文献   
100.
Pertussis toxin (PTX) is a required co-adjuvant for experimental autoimmune encephalomyelitis (EAE) induced by immunization with myelin antigen. However, PTX’s effects on EAE induced by the transfer of myelin-specific T helper cells is not known. Therefore, we investigated how PTX affects the Th17 transfer EAE model (Th17-EAE). We found that PTX significantly reduced Th17-EAE by inhibiting chemokine-receptor-dependent trafficking of Th17 cells. Strikingly, PTX also promoted the accumulation of B cells in the CNS, suggesting that PTX alters the disease toward a B-cell-dependent pathology. To determine the role of B cells, we compared the effects of PTX on Th17-EAE in wild-type (WT) and B-cell-deficient (µMT) mice. Without PTX treatment, disease severity was equivalent between WT and µMT mice. In contrast, with PTX treatment, the µMT mice had significantly less disease and a reduction in pathogenic Th17 cells in the CNS compared to the WT mice. In conclusion, this study shows that PTX inhibits the migration of pathogenic Th17 cells, while promoting the accumulation of pathogenic B cells in the CNS during Th17-EAE. These data provide useful methodological information for adoptive-transfer Th17-EAE and, furthermore, describe another important experimental system to study the pathogenic mechanisms of B cells in multiple sclerosis.  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