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   1191篇
  免费   118篇
  国内免费   7篇
综合类   37篇
化学工业   83篇
金属工艺   1篇
机械仪表   14篇
建筑科学   8篇
矿业工程   1篇
能源动力   3篇
轻工业   1074篇
石油天然气   13篇
无线电   4篇
一般工业技术   58篇
冶金工业   8篇
原子能技术   3篇
自动化技术   9篇
  2024年   10篇
  2023年   31篇
  2022年   34篇
  2021年   56篇
  2020年   57篇
  2019年   57篇
  2018年   69篇
  2017年   52篇
  2016年   56篇
  2015年   58篇
  2014年   42篇
  2013年   112篇
  2012年   102篇
  2011年   85篇
  2010年   49篇
  2009年   38篇
  2008年   49篇
  2007年   61篇
  2006年   47篇
  2005年   38篇
  2004年   39篇
  2003年   34篇
  2002年   22篇
  2001年   18篇
  2000年   16篇
  1999年   8篇
  1998年   9篇
  1997年   11篇
  1996年   5篇
  1995年   7篇
  1994年   6篇
  1993年   5篇
  1992年   4篇
  1991年   4篇
  1989年   4篇
  1988年   3篇
  1987年   2篇
  1986年   4篇
  1985年   5篇
  1984年   6篇
  1980年   1篇
排序方式: 共有1316条查询结果,搜索用时 62 毫秒
1.
Objectives: Examine the effectiveness of an intervention to increase fruits and vegetables (FV) consumption among smokers. Design: Cluster-randomized trial of 20 public housing developments; 10 randomly assigned to an FV intervention and 10 to a smoking cessation intervention. Main outcome measures: Usual (past 7 days) and past 30 days change in daily FV intake at 8 weeks and 6 months postbaseline. Results: Greater increases were seen in the FV group. At Week 8 and Month 6, the FV group had consumed 1.58 (p = .001) and 0.78 (p = .04), respectively, more daily FV servings in the past 7 days than the cessation group. At the same time points, the FV group had consumed 3.61 (p = .01) and 3.93 (p = .01), respectively, more FV servings in the past 30 days than the cessation group. Completing more motivational interviewing sessions (p = .02) and trying more recipes (p = .02) led to significantly greater increases at Month 6 among FV participants. Conclusions: Motivational interviewing counseling and lifestyle modification through trying out healthy recipes may be effective in helping a high-risk population increase their FV intake. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
2.
Monitoring of nitrate (NO3-) and nitrite (NO2-) content in agricultural products in Slovenia has been carried out since 1996. The results of monitoring over the period 1996-2002 are presented. During this time 924 samples of 14 different agricultural products (potato, lettuce, apples, carrot, silage maize, cabbage, grapes, peaches, string beans, cereals, pears, cucumbers, strawberries and tomato) were analysed. The samples were taken at the time of maturity directly from growing sites and they were analysed using segmented flow analysis. The average nitrate contents were the highest in lettuce (1074 mg kg-1), cabbage (881 mg kg-1), string beans (298 mg kg-1) and carrot (264 mg kg-1), and they were moderately high in potato (158 mg kg-1), silage maize (122 mg kg-1), strawberries (94 mg kg-1), cucumbers (93 mg kg-1) and cereals (49 mg kg-1). Low nitrate contents (below 6 mg kg-1) were found in fruit (grapes, peaches, apples and pears) and tomato. With the exception of cereals (8.9 mg kg-1), apples (1.5 mg kg-1), potato (1.2 mg kg-1) and pears (1.0 mg kg-1) the content of nitrites did not exceed 0.5 mg kg-1. It may be concluded that the results of the monitoring were in most cases similar to the results of investigations obtained in other countries.  相似文献   
3.
4.
开放式热风干燥(AD)工艺以其设备成本低、操作和维修简单等特点,在国内大批量脱水蔬菜生产中仍占有较高的比例。但开放式AD蔬菜的能耗高,故对其进行节能技术研究是项急需而有意义的。我们可以从AD工艺前处理、AD和其它干燥方法联合、干燥系统改进、余热回收以及工艺参数再优化等5个方面来降低AD蔬菜生产中的能耗。  相似文献   
5.
本实验发明了一种化合物组合:新型乳化剂、天然植物碱、纳米降解剂、助溶剂、天然香型和水等组成。通过试验筛选出最佳配方,并且测定了该清洁剂的去污能力、杀菌能力、对残留农药降解效果、泡沫性能、表面张力和稳定性。结果表明,该产品制备简便、综合洗洁性能好,具有较大市场前景。  相似文献   
6.
研究了一种新型复合果蔬汁饮料的制作工艺。以芹菜、番茄和大白菜作为原材料,采用面包酵母驱除蔬菜所带有的异味,以壳聚糖作为新型澄清剂进行复合果蔬汁饮料的澄清,再采用新型抑菌剂羧甲基壳聚糖进行复合果蔬汁饮料的防腐,通过单因素试验和正交试验最终确定复合果蔬汁饮料的最佳配方。结果表明,复合果蔬汁饮料的最佳配方为:番茄汁60%、芹菜汁20%、大白菜汁20%、浓缩苹果汁0.3%、白砂糖2.5%、柠檬酸0.03%。面包酵母驱除蔬菜异味的用量为0.5%、壳聚糖作为澄清剂的用量为0.4 g/L、羧甲基壳聚糖作为防腐剂的用量为0.15%。  相似文献   
7.
Soil cadmium (Cd) contamination resulted from mining and smelting is a major environmental concern,and health risk associated with Cd exposure to multi-media through muti-pathway is increasing.Cd concentrations in soils,vegetables and paddy rice were investigated,and potential non-carcinogenic and carcinogenic health risks exposure to Cd were estimated at six villages around the Dabaoshan Mine,South China.A total of 87 soil samples were found to exceed the China's maximum permission level (MPL) for Cd,while the highest value of 4.42 mg/kg was found near irrigation ditch associated with Hengshi River in Xinyi (XY) Village.Cd contents in vegetables and rice exceeded the maximum permissible concentration by more than five times in every village.Cadmium accumulation in plants is in the order of celery 〉 lactuca sativa L 〉 Chinese cabbage 〉 Romaine lettuce 〉 asparagus lettuce 〉 mustard 〉 cabbage mustard 〉 cabbage.The mean hazard quotient (HQ) of all villages is in the range of [5.29,25.75],and the mean values of cancer risk for investigated areas are more than 10 times greater than the USEPA (2009) threshold limit value of 10-4.Moreover,human non-carcinogenic and carcinogenic risks are mainly attributable to paddy rice intake,followed by vegetables intake,soil ingestion,inhalation,and dermal contact.The results indicate that Cd has a huge potential risk on human health for the local residents.  相似文献   
8.
湖北省蔬菜产销现状是供大于求,存在小生产与大市场大流通的矛盾日益加剧,蔬菜品质亟待提高,蔬菜产品加工增值环节薄弱等问题,湖北省应结合省情、国情进行全面规划,制定蔬菜生产可持续发展战略。要统筹安排,搞好蔬菜基地布局,推进蔬菜产业化发展;要建立完善的蔬菜产销体系;提高农民素质,实施科技兴菜;要推广无公害蔬菜生产技术,以优质蔬菜占领市场;提高加工转化能力,促进蔬菜增值。  相似文献   
9.
Liquid chromatography coupled to mass spectrometry (LC-MS) is an excellent technique to determine trace levels of polar and thermolabile pesticides and their degradation products in complex matrices. LC-MS can be equipped with several mass analyzers, each of which provides unique features capable to identify, quantify, and resolve ambiguities by selecting appropriate ionization and acquisition parameters. We discuss in this review the use of LC coupled to (quadrupole) time-of-flight mass spectrometry (LC-(Q)ToF-MS) to determine the presence of target and non-target pesticides in water and food. This technique is characterized by operating at a resolving power of 10,000 or more. Therefore, it gives accurate masses for both parent and fragment ions and enables the measurement of the elemental formula of a compound achieving compound identification. In addition, the combination of quadrupole-ToF permits tandem mass spectrometry, provides more structural information, and enhances selectivity. The purpose of this article is to provide an overview on the state of art and applicability of liquid chromatography time-of-flight mass spectrometry (LC-ToF-MS), and liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS) for the analysis of pesticides in environmental matrices and food. The performance of such techniques is depicted in terms of accurate mass measurement, fragmentation, and selectivity. The final section is devoted to describing the applicability of LC-(Q)ToF-MS to routine analysis of pesticides in food matrices, indicating those operational conditions and criteria used to screen, quantify, and identify target and "suspected" pesticides and their degradation products in water, fruits, and vegetables. The potential and future trends as well as limitations of LC-(Q)ToF-MS for pesticide monitoring are highlighted.  相似文献   
10.
蔬菜中甲霜灵残留量的HPLC分析   总被引:6,自引:2,他引:6  
殷春杭  朱国念  钱允辉  王志强 《农药》2006,45(10):686-686,688
用乙酸乙酯和丙酮,采用旋涡震荡法提取,并用活性炭和无水硫酸钠进行净化脱色和脱水。提取液用高效液相色谱仪测定,外标法定量。其特点是方法简便、快速,结果准确。检测波长:220;色谱柱:ZORBAXSB-C184.6mm×150mm;流动相:甲醇与水(体积比为70∶30);流速:1mL/min;进样量:10mL。该方法的相对标准偏差为1.42%~2.93%,平均回收率在83.26%~99.53%之间。  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