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   9341篇
  免费   689篇
  国内免费   321篇
电工技术   406篇
综合类   411篇
化学工业   1668篇
金属工艺   441篇
机械仪表   439篇
建筑科学   626篇
矿业工程   158篇
能源动力   317篇
轻工业   580篇
水利工程   124篇
石油天然气   311篇
武器工业   34篇
无线电   1513篇
一般工业技术   1334篇
冶金工业   683篇
原子能技术   80篇
自动化技术   1226篇
  2024年   18篇
  2023年   122篇
  2022年   208篇
  2021年   333篇
  2020年   206篇
  2019年   198篇
  2018年   257篇
  2017年   262篇
  2016年   276篇
  2015年   270篇
  2014年   401篇
  2013年   574篇
  2012年   512篇
  2011年   635篇
  2010年   571篇
  2009年   533篇
  2008年   585篇
  2007年   465篇
  2006年   477篇
  2005年   350篇
  2004年   302篇
  2003年   306篇
  2002年   279篇
  2001年   231篇
  2000年   216篇
  1999年   226篇
  1998年   292篇
  1997年   224篇
  1996年   210篇
  1995年   164篇
  1994年   136篇
  1993年   95篇
  1992年   69篇
  1991年   53篇
  1990年   43篇
  1989年   44篇
  1988年   32篇
  1987年   24篇
  1986年   23篇
  1985年   13篇
  1984年   8篇
  1983年   7篇
  1982年   7篇
  1981年   9篇
  1980年   15篇
  1979年   13篇
  1978年   7篇
  1976年   13篇
  1975年   9篇
  1974年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The intratracheal instillation of xanthine-xanthine oxidase caused a marked decrease in dynamic respiratory compliance, indicating airway constriction. The constriction was significantly attenuated by fullerenol-1, but not by other agents or receptor antagonists.  相似文献   
92.
The fracture toughness J Ic (ρ) and fractal dimension D f of fractured surfaces of CuNiAl single crystal have been measured at temperatures in the range 20 °C to 120 °C, in which thermoelastic martensitic transformation takes place. The parent phase has higher fracture toughness than the martensite phase due to stress-induced transformation. The relationship between J Ic (ρ) and D f has been studied. It was found that log J Ic (ρ) is linearly related to D f if the failure involves a single mechanism. The slope of the plot may either be positive or negative for brittle or ductile failure, respectively. The difference in the J Ic (ρ)-D f correlation can be understood in terms of the micromechanism of fracture.  相似文献   
93.
黄仕香  赖爱平 《特种结构》2007,24(3):61-62,92
本文给出了用加强板加大管道截面系数来增加架空输水管道跨越距离的设计方法及其计算过程,并用实例说明了用此种方法加强大跨度管道的有效性和合理性。  相似文献   
94.
An approach to aid decision making for urban water management is presented that is based on the concept of trade-off sacrifice level in pairwise comparisons between criteria, modelled using fuzzy logic. This approach is illustrated by a case study - selection of alternative water supplies for a Sydney household. Four key decision making criteria covering health, economic, environment and technical aspects are selected: annual probability of infection, life cycle energy use, life cycle cost and reliability. The decision making problem is to select between cases with different volume and application of recycled greywater and rainwater in light of the four criteria. Decision maker's preference is expressed by five levels of trade-off sacrifice between pairs of criteria. The decision makers can assign their preferences for sacrifice level by linguistic assessment and the output trade-off weight (TOW). Measures of decision makers' perceived trade-off level are modelled by a rule-based fuzzy logic control system. The final analysis shows the performance for each sacrifice class for each case, to aid overall decision making with stakeholders.  相似文献   
95.
1.27-/spl mu/m InGaAs: Sb-GaAs-GaAsP vertical-cavity surface-emitting lasers (VCSELs) were grown by metal-organic chemical vapor deposition and exhibited excellent performance and temperature stability. The threshold current changes from 1.8 to 1.1 mA and the slope efficiency falls less than /spl sim/35% as the temperature raised from room temperature to 70/spl deg/C. With a bias current of only 5 mA, the 3-dB modulation frequency response was measured to be 8.36 GHz, which is appropriate for 10-Gb/s operation. The maximal bandwidth is measured to be 10.7 GHz with modulation current efficiency factor (MCEF) of /spl sim/5.25 GHz/(mA)/sup 1/2/. These VCSELs also demonstrate high-speed modulation up to 10 Gb/s from 25/spl deg/C to 70/spl deg/C.  相似文献   
96.
赖玲  文莉 《食品与药品》2006,8(1B):8-11
食品安全.在2005年中仍然纷纷扰扰:食品与家庭每个成员的健康息息相关,而维护全家人的健康,则是女主人义不容辞的责任。我们一起来听听.于她们而言.2005年最关心的食品安全问题是什么?[编者按]  相似文献   
97.
In this paper, a technique is proposed for the rendering of transparent objects interactively using the method of refractive rendering. In the proposed technique, the refractive rendering algorithm is performed in two stages, namely the pre‐computation stage and the shading stage. In the pre‐computation stage, ray‐traced information, including directions and positions of rays, are generated by a ray tracing process and are stored in a set of ray lists. In the shading stage, these data are retrieved from the ray lists for computing the shading of an object. Using the proposed technique, photorealistic image of transparent objects and gemstones with various cuttings, material properties, lighting and background can be rendered interactively. By combining the refractive rendering technique with conventional shading techniques, jewelry and crystal designs can be rendered at a much higher speed comparing with conventional ray tracing techniques.  相似文献   
98.
5Cu/(10NiO-NiFe2O4) cermet inert anodes were prepared by cold-pressing and sintering process, and the effect of superheat degree of melting K3AlF6-Na3AlF6-AlF3 on their anticorrosion performance was studied under electrolysis conditions. The results show that, the fluctuation of cell becomes small with increasing of superheat degree, which is helpful to inhibit the formation of cathodic encrustation; the concentration of impurities from inert anode in bath goes up to certain degree, but it is far smaller than those in traditional high-temperature bath. Increasing the superheat degree of melting K3AlF6-Na3AlF6-AlF3 has unconspicuous effect on the contents of impurities in cathodic aluminum. The total mass fractions of Fe, Ni and Cu in aluminum are 15.38% and 15.09% respectively under superheat degree of 95 and 195 ℃. From micro-topography of anode used view, increasing the superheat degree can aggravate corrosion of metal Cu in inert anode, and has negative influence on electrical conductivity of electrode to some extent.  相似文献   
99.
蛋白质与原卟啉Ⅸ及复合物发光机理探讨   总被引:1,自引:0,他引:1  
对原卟啉Ⅸ(ProtoporphyrinⅨ)与蛋白质结合物的吸收、荧光的激发、发射光谱等的研究,表明了在光作用下,其可见区发光(λmax635nm左右)与卟啉有关,而紫外区发光(λmax422nm左右)与蛋白质的色氨酸残基有关,其光谱特性与临床诊断选择的癌固有荧光特征峰基本相符。该研究结果为探讨癌的发光机理积累了有益资料.  相似文献   
100.
Reported here is a rapid, sensitive and relatively inexpensive procedure using gas chromatography with nitrogen-phosphorus detection (GC-NPD) to quantify buspirone levels in brains of rats. The analyte was directly extracted from brain homogenate with toluene after basification and then subjected to GC-NPD analysis using a capillary column. The calibration curves were linear over the range of 10 to 320 ng per 2 ml of brain homogenate, with typical r2 values >0.99. The assay was highly reproducible and gave peaks with excellent chromatographic properties.  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