首页 | 官方网站   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   6198篇
  免费   175篇
  国内免费   6篇
工业技术   6379篇
  2023年   33篇
  2022年   104篇
  2021年   112篇
  2020年   65篇
  2019年   90篇
  2018年   101篇
  2017年   106篇
  2016年   103篇
  2015年   88篇
  2014年   138篇
  2013年   338篇
  2012年   244篇
  2011年   378篇
  2010年   251篇
  2009年   271篇
  2008年   261篇
  2007年   276篇
  2006年   265篇
  2005年   224篇
  2004年   191篇
  2003年   182篇
  2002年   182篇
  2001年   113篇
  2000年   113篇
  1999年   123篇
  1998年   129篇
  1997年   128篇
  1996年   135篇
  1995年   102篇
  1994年   109篇
  1993年   116篇
  1992年   110篇
  1991年   51篇
  1990年   84篇
  1989年   93篇
  1988年   79篇
  1987年   90篇
  1986年   77篇
  1985年   95篇
  1984年   63篇
  1983年   66篇
  1982年   43篇
  1981年   55篇
  1980年   45篇
  1979年   44篇
  1977年   35篇
  1976年   23篇
  1975年   30篇
  1974年   23篇
  1973年   23篇
排序方式: 共有6379条查询结果,搜索用时 15 毫秒
161.
In light of the increasing interest in the development of functional food, several researches have focused on the production of food grade emulsifiers of nutritional interest, especially enriched in the eicosapentaenoic (EPA) and docosahexaenoic acids (DHA). The aim of this paper is to make a review of the production of monoacylglycerols (MAG) and diacylglycerols (DAG) obtained from different feedstock, mainly fish oil. A section of this paper is dedicated to the raw materials used as feedstock for these emulsifiers production. The health benefits of these partial acylglycerols are outlined. The chemical and enzymatic methods for producing these esters of glycerol are discussed, focusing on glycerolysis reactions. Recent advances on the lipase-catalyzed production of these partial acylglycerols in alternative reaction media and systems are also reviewed.  相似文献   
162.
ABSTRACT: Lowbush or wild blueberries ( Vaccinium angustifolium Ait.) and soy protein offer many complementary health benefits; thus, combinations of these 2 foods may appeal to health-conscious consumers. Four frozen dessert formulations were prepared with soy protein isolate and different amounts of blueberry concentrate and puree. Fat content (3% or 10%) was adjusted with soybean oil and nondairy creamer. Consumers ( n = 40) from the campus community used a 9-point hedonic scale to assess acceptability. The 10% fat content and 8.6% blueberry concentrate formulation received the highest overall acceptability (6.63, P < 0.05), compared with formulations with 10% fat and 17.2% blueberry concentrate and 3% fat and 12.9% blueberry concentrate. More than 1 /3 of the panelists are trying to increase blueberry consumption, 20% want to increase soy, and 20% want to eat more of both foods. Development of palatable desserts combining lowbush blueberries and soy protein could lead to increased consumption of both healthy ingredients.  相似文献   
163.
The effects of growth temperature and salinity on the cellular fatty acids were investigated on Aeromonas caviae, Aeromonas hydrophila and Aeromonas sobria. Under optimal growth conditions, fatty acids patterns were dominated by even-numbered chains C(16:0), C(16:1cis9), C(18:1cis11), C(12:0) and C(14:0). Growth temperature modifications induced, in the three Aeromonas species, important changes in fatty acid (i) unsaturation, (ii) branching and (iii) chain length. An important decrease in the C(18:1cis11) fatty acid content was observed for the three species below 15 degrees C and above 25 degrees C. The evolution of C(18:1cis11) and C(16:0) showed a mirror image for the three Aeromonas species. Low NaCl concentrations did not elicit significant changes in the fatty acids content of the three Aeromonas species. However, for high NaCl concentration in the medium, the growth ability was related to an important decrease of the unsaturated to saturated fatty acids ratio indicating a membrane rigidification. Thermal and salinity adaptations were branched fatty acid-dependent for A. caviae, whereas this phenomenon was less significant for A. hydrophila and A. sobria.  相似文献   
164.
Treatment of BV2 microglial cells with blueberry extracts has been shown to be effective in reducing lipopolysaccharide (LPS)-induced proinflammatory mediators such as nitric oxide (NO), tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), inducible NO synthase (iNOS), and cyclooxygenase 2 (COX2). The current study explored the possibility that the down-regulation of iNOS and COX2 by blueberry extracts was mediated through NF-κB signaling pathway. A column-purified fraction of polyphenol-enriched blueberry extract (PC18) was used to treat LPS-activated BV2 cells. The results thus far showed that blueberry polyphenols significantly suppressed iNOS and COX2 promoter activities. In addition, blueberry polyphenols inhibited NF-κB nuclear translocation in LPS-activated BV2 cells. These findings suggested that the beneficial effects of blueberries may involve direct modulation of oxidative stress and/or inflammatory signaling cascades.  相似文献   
165.
ABSTRACT: Arrowtooth flounder soluble protein powder (AFSP) and arrowtooth flounder insoluble protein powder (AFISP) were evaluated for their functional, nutritional, and rheological properties. AFSP and AFISP contained 80% and 79% protein and 5.9% and 14.9% fat, respectively. Yield of AFSP (8.6%) was less than AFISP (13.1%). AFSP and AFISP had desirable essential amino acid and mineral contents. Emulsion stability of AFSP was greater than AFISP. Fat and water absorptions (mL/g protein) were 5.2 and 1.8 for AFSP, respectively, and 3.3 and 4.2 for AFISP Mayonnaises made from AFSP had greater emulsion stability than mayonnaise made from AFISP. Mayonnaises from both AFSP and AFISP possessed pseudoplastic and viscoelastic characteristics.  相似文献   
166.
167.
Low rates of triacylglycerol (TAG) biosynthesis were observed in cell-free extracts ofCandida curvata, but rates were increased up to 10-fold by adding either α- or β-cyclodextrins. Spheroplasts, whole or gently disrupted, had higher rates of incorporation of both [U-14C]glycerol 3-phosphate or [1-14C]oleate into triacylglycerol and the intermediates of its biosynthesis: lysophosphatic acid, phosphatidic acid and diacylglycerol. Fatty acyl-CoA synthetase was highest with palmitate, oleate and linoleate but was some 6- to 8-fold lower with stearate. Stearate and stearoyl-CoA were poorly incorporated into lipids. Subcellular fractionation of the spheroplasts into mitochondrial, microsomal, lipid bodies and supernatant fractions diminished the rates of14C incorporation of oleate into triacylglycerol. By comparing the relative specific activities for each activity in each fraction, the fatty acyl-CoA synthetase activity appeared mainly in the lipid bodies, and that for phosphatidic acid formation was mainly in the mitochondrion; other activities were too weak and too dispersed for accurate assessment of their location. Recombining all the subcellular fractions restored triacylglycerol synthesizing activity. Omitting any single fraction from the mixture did not result in restoration of triacylglycerol synthesizing activity. Starvation of the yeast, which leads to utilization of the endogenous lipid reserves, stimulated fatty acyl-CoA synthetase activity, but diminished phosphatidic acid and triacylglycerol biosynthesis indicating probable induction of β-oxidation in the peroxisomes and repression of lipid biosynthesis.  相似文献   
168.
Additive manufacturing, sometimes referred to as 3D printing is a new, rapidly developing technology which has the potential to revolutionize fabrication of certain high value, complex products. Until now conventional elastomers have not been widely used in the additive manufacturing process. The goal of our work was to determine the feasibility of additive manufacturing using ink jet printing of elastomeric latex materials. Particle size, viscosity, and surface tension were measured for five different latex materials—poly(2‐chloro‐1,3‐butadiene), carboxylated styrene‐butadiene rubber, carboxylated butadiene‐acrylonitrile copolymer, natural rubber, and prevulcanized natural rubber. The XSBR latex was predicted as the one most likely to be printable. Printing trials carried out with the XSBR as the ink proved it to be printable, although technical problems of agglomeration and print head clogging need to be addressed and both the material and process need to be optimized for consistent printing to be achieved. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42931.  相似文献   
169.
In a given batch more than 30%–40% of polycrystalline, MgO-doped Al2O3 tubes were converted into single crystals of sapphire by abnormal grain growth (AGG) in the solid state at 1880°C. Most crystals grew 4–10-cm in length in tubes with wall thicknesses of 1/2 and 3/4 mm and outer diameters of 5 and 7 mm, respectively, and had their c -axes oriented ∼ 90° and 45° to the tube axis. Initiation of AGG was associated with low values of bulk MgO concentration near 50 ppm. The unconverted tubes did not develop centimeter-size crystals but instead exhibited millimeter-size grains. The different grain structures in converted and unconverted tubes may be related to nonuniform concentration of MgO in the extruded tubes. The growth front of the migrating crystal boundary was typically nonuniformly shaped, and the interface between the single crystal and the polycrystalline matrix was composed of many "curved" boundary segments indicative of classical AGG in a single-phase material. The average velocities of many migrating crystal boundaries were quite high and reached ∼1.5 cm/h. The average grain boundary mobility at 1880°C was calculated as 2 × 10−10 m3/(N·s), representing the highest value reported so far in Al2O3 and within a factor of 2.5 of the calculated intrinsic mobility. Under similar experimental conditions sapphire crystals did not grow when a codopant of CaO, La2O3, or ZrO2 was added in concentrations of several hundred ppm.  相似文献   
170.
Graphene nanosheets for enhanced lithium storage in lithium ion batteries   总被引:7,自引:0,他引:7  
Graphene nanosheets were synthesized in large quantities using a chemical approach. Field emission electron microscope observation revealed that loose graphene nanosheets agglomerated and crumpled naturally into shapes resembling flower-petals. High resolution transmission electron microscope analysis, Raman spectroscopy and ultraviolet-visible spectroscopy measurements confirmed the graphitic crystalline structure of the graphene nanosheets. The nanosheets exhibited an enhanced lithium storage capacity as anodes in lithium-ion cells and good cyclic performance.  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-23

京公网安备 11010802026262号