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   928篇
  免费   20篇
  国内免费   1篇
电工技术   80篇
综合类   3篇
化学工业   305篇
金属工艺   23篇
机械仪表   40篇
建筑科学   12篇
能源动力   170篇
轻工业   76篇
石油天然气   2篇
无线电   38篇
一般工业技术   118篇
冶金工业   22篇
原子能技术   15篇
自动化技术   45篇
  2023年   2篇
  2022年   10篇
  2021年   13篇
  2020年   4篇
  2019年   10篇
  2018年   13篇
  2017年   13篇
  2016年   21篇
  2015年   12篇
  2014年   28篇
  2013年   54篇
  2012年   34篇
  2011年   66篇
  2010年   46篇
  2009年   42篇
  2008年   54篇
  2007年   52篇
  2006年   38篇
  2005年   37篇
  2004年   46篇
  2003年   46篇
  2002年   35篇
  2001年   12篇
  2000年   22篇
  1999年   19篇
  1998年   31篇
  1997年   16篇
  1996年   24篇
  1995年   13篇
  1994年   13篇
  1993年   13篇
  1992年   7篇
  1991年   7篇
  1990年   12篇
  1989年   5篇
  1988年   6篇
  1987年   2篇
  1986年   9篇
  1985年   13篇
  1984年   3篇
  1983年   5篇
  1982年   7篇
  1981年   4篇
  1980年   4篇
  1979年   5篇
  1978年   9篇
  1977年   4篇
  1976年   3篇
  1975年   3篇
  1971年   1篇
排序方式: 共有949条查询结果,搜索用时 15 毫秒
111.
The anatomical and morphological distribution of the G proteins G(o), G(i1) and 2, and Gs alpha-subunits in rat forebrain sections was determined using immunohistochemical techniques. Diffuse G(o) labeling occurred in the neuropil throughout the cortex, superficial layers of the entorhinal cortex, thalamus, several white matter fiber tracts, and hippocampus. G(i1) and 2 immunoreactivity was also located in the neuropil but produced a more fibrous pattern. Fibrous labeling of G(i1) and 2 was observed in the cortex, amygdala, hippocampal subfield CA3, and several white matter fiber tracts. Both G(o) and G(i1) and 2 labeling was present in the pencil fibers within the striatum and lateral geniculate nucleus. Gs labeling, in contrast to G(o) and G(i1) and 2, was generally cytoplasmic. Cytoplasmic Gs labeling was observed in the thalamus, habenula, dentate, geniculate nucleus, hypothalamus, and hippocampus. Intense Gs labeling was observed in the striatum parenchyma, choroid plexus, and infundibular stem. Based on our results, we conclude that the G proteins G(o), G(i1) and 2, and Gs are anatomically distributed differently throughout the brain. The diffuse neuropil labeling of G(o), fibrous neuropil labeling of G(i1) and 2, and cytoplasmic labeling of Gs strongly suggests that the G proteins are also differentially distributed morphologically within a neuron. The differential anatomical and cellular location of G proteins in the CNS may contribute to the coupling specificity between neurotransmitter receptors and G proteins.  相似文献   
112.
113.
Manufacturing conditions of coal-derived caking substances (SRC) were investigated to determine the effects of these conditions on the chemical and caking properties of the additives. The solvent-refined coal (SRC) produced in the early stage of digestion at the lower temperature, of which β- and γ-fractions were 55 and 35 wt %, respectively, consisted of a heterogeneous mixture characterized by a low aromaticity, long side-chains, and a large, average molecular weight. The Roga index of the SRC was large but its total dilatation was small. As the digestion proceeded, the condensation and the cycloaromatization reactions improved the homogeneous nature and decreased the molecular weight by the breakage of side-chains, dealkylation, and deoxidation, leading to increases in the γ-fraction and total dilation by decreases in the β-fraction and Roga index. Such trends were more marked when the conversion exceeded 90 wt %. The relation between structure and the caking properties of the SRC are discussed.  相似文献   
114.
Thermally stimulated current was measured to determine trap distribution and charging and discharging mechanisms in a Metal-Nitride-Oxide-Semiconductor (MNOS) diode with 16 Å oxide thickness. By changing gate voltage, heating rate and the initial flat-band voltage, the memory traps near the nitride-oxide interface were separated from the others. The general formula was derived for the thermally stimulated current in an MNOS diode and was applied to obtain the trap distribution as well as effective emission time constants. The results indicate that the memory traps are distributed 50 Å deep into the nitride film from the nitride-oxide interface. The energy level lies at around 2·55 eV from the bottom of the nitride conduction band. The charging and discharging mechanism is the cascade connection of tunneling and thermal excitation or trapping. The obtained trap distribution and the charge transfer mechanism are successful for interpreting the write-in and retention characteristics.  相似文献   
115.
The heat capacity of C70 has been measured by adiabatic calorimetry between 14 and 320 K. The orientational phase transition is observed as a broad hump in the heat capacity curve, which is strongly influenced by small amount of solvent remaining in the sample.  相似文献   
116.
BACKGROUND: Ergothioneine (ESH), a potent antioxidant, has been found in certain edible mushrooms. Our previous research showed that ESH extracted from the edible mushroom Flammulina velutipes has a positive effect on the colour stability of beef and tuna meat. The purpose of the present study was to compare the efficacy and applicability of ESH extracts prepared from different mushroom species as a colour stabilizer in fish meats. RESULTS: Levels of ESH higher than 2.8 mg mL?1 were found in extracts prepared from the fruiting bodies of F. velutipes, Lentinula edodes, Pleurotus cornucopiae and Pleurotus eryngii and the processing waste of F. velutipes. When 1 mL of each of the extracts was added to 100 g of minced bigeye tuna and yellowtail meats, the bright‐red colour remained after 5 and 2 days, respectively, of ice storage. The anti‐discoloration efficacy of 1 mL of the extracts prepared from 10 g of the fresh waste portion of F. velutipes was similar to that of its fruiting body or 0.5 g kg?1 of sodium ascorbate when added to 100 g of minced bigeye tuna meat under ice storage. CONCLUSION: The results of this study clearly showed that ESH prepared from different mushroom species stabilized the colour of fish meats, and the extract from the F. velutipes was the most effective. Copyright © 2010 Society of Chemical Industry  相似文献   
117.
Chotimarkorn C  Ohshima T  Ushio H 《Lipids》2006,41(3):295-300
A fluorescent image analysis method was developed to evaluate lipid hydroperoxide formation in fish muscle. The lipid hydroperoxides generated in white and dark fish muscles during storage at 5–6°C oxidized 3-perylene diphenylphosphine located in the tissue to yield the fluorescent derivative, 3-perylene diphenylphosphine oxide (3-PeDPPO). 3-PeDPPO thus obtained was determined by digital fluorescent image analysis. The 3-PeDPPO fluorescence intensity of white and dark muscle increased during low-temperature storage (0–24 h) and was clearly correlated with total lipid hydroperoxide levels in muscle extracts, which were determined by using HPLC based on a triphenylphosphine oxidation method (R 2=0.954). These results suggest that 3-PeDPPO fluorescence, coupled with fluorescent image analysis, is a novel tool for direct determination of lipid hydroperoxides in fish muscle without a need for extraction of lipid.  相似文献   
118.
We report the design and fabrication of a novel electrode-supported honeycomb solid oxide fuel cell (SOFC), that can generate high volumetric power density. Among various cell designs, honeycomb SOFCs are suitable for compact SOFC modules because they have a large surface electrode area per unit volume. We have succeeded in fabricating a cathode-supported honeycomb SOFC via extrusion of a LaSrMnO3 honeycomb monolith and through the use of a new slurry injection method for the channel surface coating using electrolyte/anode bi-layers. The fabricated honeycomb SOFCs exhibited high volumetric power densities of approximately 1.2 W/cm3 at 600°C under a wet H2 fuel flow.  相似文献   
119.
120.
Journal of Mechanical Science and Technology - The acoustic noise and flow condition of tandem propellers in a horizontal axis-type tidal stream power unit, which is composed of counter-rotating...  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