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   7572篇
  免费   567篇
  国内免费   187篇
电工技术   42篇
综合类   497篇
化学工业   2318篇
金属工艺   189篇
机械仪表   91篇
建筑科学   326篇
矿业工程   238篇
能源动力   45篇
轻工业   3293篇
水利工程   156篇
石油天然气   46篇
武器工业   10篇
无线电   207篇
一般工业技术   381篇
冶金工业   354篇
原子能技术   30篇
自动化技术   103篇
  2024年   35篇
  2023年   134篇
  2022年   238篇
  2021年   275篇
  2020年   258篇
  2019年   217篇
  2018年   209篇
  2017年   220篇
  2016年   208篇
  2015年   243篇
  2014年   365篇
  2013年   416篇
  2012年   569篇
  2011年   611篇
  2010年   422篇
  2009年   371篇
  2008年   324篇
  2007年   538篇
  2006年   495篇
  2005年   394篇
  2004年   340篇
  2003年   256篇
  2002年   226篇
  2001年   160篇
  2000年   162篇
  1999年   117篇
  1998年   131篇
  1997年   92篇
  1996年   63篇
  1995年   68篇
  1994年   46篇
  1993年   35篇
  1992年   21篇
  1991年   12篇
  1990年   11篇
  1989年   8篇
  1988年   8篇
  1987年   5篇
  1986年   5篇
  1985年   7篇
  1984年   1篇
  1982年   4篇
  1981年   1篇
  1980年   2篇
  1978年   1篇
  1976年   1篇
  1955年   1篇
排序方式: 共有8326条查询结果,搜索用时 0 毫秒
991.
萝卜红色素是我国《食品添加剂使用卫生标准》(GB2760)允许使用的天然着色剂之一,应用广泛;本文就萝卜红色素的化学研究进展进行了综述。  相似文献   
992.
浸泡处理对红芸豆的物理性质及蒸煮品质的影响   总被引:2,自引:0,他引:2  
以红芸豆为原料,探讨不同浸泡温度(25、45、65℃)对芸豆物理性质及蒸煮品质的影响。结果表明:芸豆在浸泡过程中,随着浸泡温度升高与时间延长,其吸水率、体积膨胀率、固形物溶出率等均呈增加的趋势,平衡吸水率常数则呈下降趋势;浸泡温度的提高有利于达到浸泡平衡及缩短浸泡时间。在加工性能方面,45℃下浸泡可显著缩短煮豆时间并提高煮熟红芸豆的品质。  相似文献   
993.
Different amino acid derivatives were synthesized during cultivation of a Monascus species. Derivatives exhibiting an inhibitory activity against HMG-CoA reductase were screened by in vitro tests. The threonine derivative had a high inhibitory activity of 38% while four other derivatives showed a greater than 23% activity. The orange monascus pigment showed a high activity of 36%. In vivo tests using female C57BL/6 mice were performed with the threonine derivative and orange pigment. Changes in the cholesterol and lipid levels in mice due to addition of the pigments were investigated. The total cholesterol (TC) level of mouse serum was reduced by 8–9% with the threonine derivative and by 16% with orange pigment. Supplementation with the threonine derivative and orange pigment decreased the LDL cholesterol level by 18–26% and increased the HDL cholesterol level by 1–9%. The atherogenic index (AI) value was reduced by 23–27% with pigment supplementation. The anti-atherosclerosis effect of monascus pigments can be induced by control of the lipid content in the serum rather than in the liver of mice.  相似文献   
994.
BACKGROUND: Red clover (Trifolium pratense L.), a widely used fodder, has recently received considerable interest as a valuable source of isoflavones for many health‐related applications. The aim of this study was to analyse the concentrations of four isoflavones, daidzein, genistein, formononetin and biochanin A, in extracts of leaves, stems, roots and different coloured flowers from red clover by high‐performance liquid chromatography and to determine the antifungal activities of the extracts. RESULTS: Among greenhouse‐grown samples the highest amounts of daidzein and genistein were found in petioles (0.11–0.28 and 0.30–0.54 mg g?1 respectively), while leaves were rich in formononetin and biochanin A (5.57–9.05 and 10.94–14.59 mg g?1 respectively). High formononetin concentrations were found in roots, but very little biochanin A. Among field‐grown samples the highest concentrations of daidzein and genistein were detected in stems collected in August (0.24 and 0.55 mg g?1 respectively), while the highest amounts of formononetin and biochanin A were found in young leaves collected in June (7.47 and 9.69 mg g?1 respectively). Most of the extracts inhibited the growth of Drechslera teres, while the root extract showed the strongest effect against Microdochium nivale. CONCLUSION: High levels of bioactive compounds found not only in inflorescences but also in roots, leaves and stems suggest that red clover may be an inexpensive and valuable resource for many applications. Copyright © 2007 Society of Chemical Industry  相似文献   
995.
C.S. Hathorn  P.N. Gichuhi 《LWT》2008,41(5):803-815
The objective of this study was to compare the chemical, physical, micro-structural, and microbial properties of breads supplemented with sweetpotato flour and high-gluten dough enhancers. Six breads, with and without dough enhancers (DE) and varying percentages of sweetpotato flour (SPF) were processed. Breads were stored at 22±2 °C, and samples were measured on Days 0, 2, 4, 6, and 8. Moisture, ash, fat, aw, color, loaf volume, specific volume, density, texture, and weight loss were analyzed on Day 0, and β-carotene on the Days 0 and 8. The micro-structural and microbial properties of the sweetpotato breads were also compared. The fresh breads (Day 0) had moisture contents ranging from 36.66 to 41.56. β-Carotene was highest in breads containing 65% SPF. All breads were significantly (P<0.05) lighter in color by the last day of storage, while those containing 50% SPF with DE had the highest loaf volumes. Intact and damaged granules, cavities, and protein network were observed on the micrographs of the fresh breads. Further studies to include varying storage conditions, sensory, and consumer properties of the breads are needed.  相似文献   
996.
核桃壳棕色素的提取及性质研究   总被引:2,自引:0,他引:2  
以核桃壳为原料,研究树脂法纯化核桃壳棕色素的方法。结果表明AB-8树脂对核桃壳棕色素有较高的吸附量,用50%乙醇为洗脱剂得到产品质量好,色价高的核桃壳棕色素;该色素水溶性好,在酸性条件下具有较好的稳定性,有一定的耐光性,在适当温度下对热稳定性较好,对低浓度的常用食品添加剂较稳定,是一种价廉宜得、安全可靠,使用方便的天然植物色素,在食品工业中有一定的开发利用潜能。  相似文献   
997.
Heme iron overload has been implicated as the main cause of the increased risk of cancer due to the consumption of red meat. However, fish and shellfish, teas, and spices contain up to five times more iron than red meat. There is insufficient evidence that iron intake in dietary red meat is the primary causal factor for colorectal cancer. In addition, harmful substances produced during the preparation of red meat, including heterocyclic amines (HCAs), polycyclic aromatic hydrocarbons (PAHs), N‐nitroso compounds, and acrylamide, are extrinsic factors that increase carcinogenicity. HCAs are produced during the cooking of red meat, poultry meat, and fish. PAHs may also be produced during the cooking of diverse food groups, such as dairy products, fruits, vegetables, and cereals. The average daily intake of red meat among Korean individuals is 62 g; the amount of PAHs entering the body via red meat is less than the average amount of PAHs the body is exposed to in the air. Therefore, it is difficult to conclude that dietary red meat is the main cause of colorectal cancer. Rather, there may be an intricate influence of multiple factors, including fruit and vegetable intake, alcohol consumption, smoking, overweight, obesity, and stress.  相似文献   
998.
目的建立禽蛋中苏丹红Ⅰ、Ⅱ、Ⅲ、Ⅳ染料残留的液相色谱-串联质谱的检测方法。方法禽蛋样品中的苏丹红经溶解、冷冻离心及过滤提取纯化,经ZorbaxSB-C_(18)(2.1 mm×50 mm, 3.5μm)色谱柱,以乙腈和0.2%的甲酸水溶液为流动相进行等度洗脱,温度为35℃,流速为0.2mL/min,外标法定量。结果在1~50μg/kg的浓度范围内,线性关系良好(r0.99),样品中的检出限0.5μg/kg,分析时间仅为5 min,加标回收率为69.5%~108.2%,相对标准偏差为1.6%~17.5%。结论该方法准确、快速、灵敏度高,适用于禽蛋中苏丹红染料的测定。  相似文献   
999.
目的 建立红参药材高效液相色谱(high performance liquid chromatography, HPLC)指纹图谱分析方法。方法 采用Diamonsil Plus C18色谱柱(250 mm×4.6 mm, 5 μm), 以乙腈–水为流动相梯度洗脱, 柱温30 ℃, 流速为1.0 mL/min, 检测波长为203 nm。通过相似度评价、聚类分析对指纹图谱进行评价。结果 建立的 21批红参的对照指纹图谱, 确定25个共有峰, 通过对照品对比对其中14个共有峰进行了指认, 21批红参药材, 除S4, S20, 其相似度均大于0.97。结论 该方法操作简便、准确可靠、重复性好, 普适性高, 为红参药材质量控制提供有效手段。  相似文献   
1000.
对红辣素中丙酮不溶物进行了研究,选取了脱胶剂、物料比、搅拌时间、搅拌温度作为参数,以红辣素中丙酮不溶物作为评价指标,优化了红辣素脱胶工艺,并由正交试验确定了除去红辣素中丙酮不溶物的最优条件:物料比5∶3 (g/mL),硫酸钾水溶液为40%、,搅拌时间为3h,搅拌温度为50℃。  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