全文获取类型
收费全文 | 11127篇 |
免费 | 753篇 |
国内免费 | 480篇 |
专业分类
电工技术 | 1796篇 |
技术理论 | 8篇 |
综合类 | 1662篇 |
化学工业 | 1027篇 |
金属工艺 | 90篇 |
机械仪表 | 172篇 |
建筑科学 | 1951篇 |
矿业工程 | 989篇 |
能源动力 | 775篇 |
轻工业 | 495篇 |
水利工程 | 680篇 |
石油天然气 | 828篇 |
武器工业 | 11篇 |
无线电 | 134篇 |
一般工业技术 | 430篇 |
冶金工业 | 824篇 |
原子能技术 | 25篇 |
自动化技术 | 463篇 |
出版年
2024年 | 19篇 |
2023年 | 80篇 |
2022年 | 184篇 |
2021年 | 237篇 |
2020年 | 315篇 |
2019年 | 253篇 |
2018年 | 219篇 |
2017年 | 256篇 |
2016年 | 329篇 |
2015年 | 354篇 |
2014年 | 697篇 |
2013年 | 685篇 |
2012年 | 761篇 |
2011年 | 771篇 |
2010年 | 657篇 |
2009年 | 629篇 |
2008年 | 598篇 |
2007年 | 714篇 |
2006年 | 671篇 |
2005年 | 608篇 |
2004年 | 556篇 |
2003年 | 498篇 |
2002年 | 461篇 |
2001年 | 320篇 |
2000年 | 339篇 |
1999年 | 273篇 |
1998年 | 183篇 |
1997年 | 154篇 |
1996年 | 126篇 |
1995年 | 88篇 |
1994年 | 70篇 |
1993年 | 49篇 |
1992年 | 40篇 |
1991年 | 49篇 |
1990年 | 27篇 |
1989年 | 22篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 3篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1963年 | 2篇 |
1959年 | 2篇 |
1958年 | 2篇 |
1956年 | 2篇 |
1955年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
粟类作物是一类籽粒小、抗旱、耐贫瘠的一年生作物的统称,多种植和消费在亚洲和非洲的发展中国家,我国栽培面积比较大的是谷子和糜子。与种植和消费情况不同,亚洲、欧洲和美洲相对发达国家的政府更重视粟类作物的科学研究及其科研投入。我国国家自然科学基金资助发表的粟类研究论文居世界之首,欧洲委员会、英国研究与创新署、美国国家科学基金会资助的粟类研究论文数量排名紧跟其后。梳理了近5年发表的粟类科研论文,印度最多,其次是我国和美国。基于粟类作物富含膳食纤维、蛋白质、矿物质、多酚等,其具有多方面的健康功效,因此粟类的食品科学技术和植物科学成为最热的研究领域。最后阐述了国内外传统的和工业化的粟类产品情况。 相似文献
2.
《Journal of dairy science》2022,105(3):2708-2717
Each cow in a group has different nutritional requirements even if the group is formed by cows of similar age, number of lactations, and lactation stage. Common dairy farm management setup does not support formulating a diet that accurately matches individual nutritional requirements for each cow; therefore, a proportion of cows in the group will be overfed and another proportion underfed. Overfeeding and underfeeding cows increases the risk of metabolic diseases, decreases milk production, and increases nutrient waste. Consequently, profitability of dairy farms and the environment are negatively affected. Nutritional grouping is a management strategy that aims to allocate lactating cows homogeneously according to their nutritional requirements. Groups of cows with more uniform nutritional requirements facilitates the formulation of more accurate diets for the group. Current availability of large data streams on dairy farms facilitates the design of algorithms to implement nutritional grouping. Our review summarizes important factors to consider when grouping cows, describes nutritional grouping approaches, and summarizes benefits of implementing nutritional grouping in dairy farms. 相似文献
3.
Chemical filters are the most important devices for removing gas-phase pollutants in clean rooms. However, the testing concentration of chemical filters is too high for reflecting their performance in a real clean room environment. This study tested the adsorption performance of chemical filters in the two most commonly used shapes at different concentrations. Then, the Langmuir equation and Wheeler-Jonas kinetic equation were combined to establish an adsorption performance prediction model of chemical filters under actual conditions. The predicted values of the model were in good agreement with the experimental results, which indicated the high accuracy of the prediction model. The model does not need to test the microscopic parameters of the adsorbent and can maintain high accuracy at low concentrations. A fast method for calculating the service life of chemical filters was also presented. Based on this model, the total cost of using a chemical filter with a high carbon content in microelectronic clean rooms could be decreased by 45% due to decreasing the number of filter replacements over 3 months. So a chemical filter with a high carbon content should be preferred over a filter with low resistance in microelectronic clean rooms. 相似文献
4.
Wenfei Tian Yi Zheng Weiqun Wang Donghai Wang Michael Tilley Guorong Zhang Zhonghu He Yonghui Li 《Comprehensive Reviews in Food Science and Food Safety》2022,21(3):2274-2308
The health benefits of whole wheat consumption can be partially attributed to wheat's phytochemicals, including phenolic acids, flavonoids, alkylresorcinols, carotenoids, phytosterols, tocopherols, and tocotrienols. It is of increasing interest to produce whole wheat products that are rich in bioactive phytochemicals. This review provides the fundamentals of the chemistry, extraction, and occurrence of wheat phytochemicals and includes critical discussion of several long-lasting issues: (1) the commonly used nomenclature on distribution of wheat phenolic acids, namely, soluble-free, soluble-conjugated, and insoluble-bound phenolic acids; (2) different extraction protocols for wheat phytochemicals; and (3) the chemistry and application of in vitro antioxidant assays. This review further discusses recent advances on the effects of genotypes, environments, field management, and processing techniques including ultrafine grinding, germination, fermentation, enzymatic treatments, thermal treatments, and food processing. These results need to be interpreted with care due to varied sample preparation protocols and limitations of in vitro assays. The bioaccessibility, bioavailability, metabolism, and potential health benefits of wheat phytochemicals are also reviewed. This comprehensive and critical review will benefit scientific researchers in the field of bioactive compounds of cereal grains and also those in the cereal food industry to produce high-quality functional foods. 相似文献
5.
This paper offers an overall picture of the importance of Strategic Environmental Assessment (SEA) in Romania and its opportunities and constraints. The role, scope and effectiveness of SEA in Romania are presented in two good practice examples and examined in order to highlight the strengths and weaknesses of the procedure at national and local scale. In practice, the number of SEA procedures is very high due to the legislation in force, and it is increasingly effective in decision-making about programmes and plans. SEA can be viewed as a great opportunity for the implementation of sustainable development in practice. It also continues to be an important procedural and decisional instrument for management and monitoring of socioeconomic development, spatial planning and environmental protection in Romania. 相似文献
6.
迁钢二炼钢厂自投入使用210 t钢包全程加盖技术及工艺后,取得了显著效果,平均出钢温度降低10 ℃,钢包热周转使用率长期保持在85%以上,取消了钢包在线烘烤,降低了煤气消耗,有效地保证了钢包洁净度,提高了钢包包衬寿命。实践生产运行表明,炼钢生产中钢包全程加盖工艺是一项节能、环保、降耗的先进技术,为迁钢二炼钢厂取得了显著的经济效益。但在一段时间内,该工艺运行稳定性较差,通过现场生产数据归纳分析,从中找出了影响钢包加、揭盖的因素,并制定了控制措施;同时,岗位要掌握其操作要点及主要设备,才能提高运行稳定性。 相似文献
7.
针对我国建材行业传统使用的常压固定床煤气发生炉及化肥行业固定床间歇气化炉面临淘汰,无烟煤市场萎缩的情况,提出以晋城无烟煤为原料,利用赛鼎碎煤加压气化技术,生产适合建材行业大规模使用的工业燃气。以无烟煤为原料的河北沙河年产26亿m^3工业清洁燃气项目为基础,对无烟煤与天然气价格、项目经济性的关系进行了分析,结果表明,以晋城无烟块煤运到河北沙河的到厂价935元/t计算,盈亏平衡天然气价约2.26元/m^3;以沙河工业天然气到户售价2.5元/m^3计算,盈亏平衡到厂煤价约1 077元/t,项目经济性较好。 相似文献
8.
Grigorii V. Teplykh 《Industry and innovation》2018,25(1):53-83
This paper investigates how the recent crisis of 2008 changed relations between innovation and firm performance in Western Europe. We apply a structural framework of CDM modelling, which incorporates different stages of the knowledge creation process and takes into account the complex nature of innovations. The study is based on a balanced panel data of 420 listed manufacturing firms from the U.K., Germany and France. All the information is gathered from common sources, thereby reducing subjectivity, a typical problem in the field. We found, the crisis resulted in appreciable changes in the model. The most important evidence is enhancement of the role of firm resources in the post-recession period. We also reveal larger barriers for innovations, increased uncertainty and lower state dependence in R&D engagement, product creation and economic performance. These results could indicate the ‘cleaning effect’ of the crisis, which has worsened the business environment and enhanced competition. 相似文献
9.
10.