全文获取类型
收费全文 | 44109篇 |
免费 | 4511篇 |
国内免费 | 2404篇 |
学科分类
工业技术 | 51024篇 |
出版年
2024年 | 200篇 |
2023年 | 573篇 |
2022年 | 1076篇 |
2021年 | 1198篇 |
2020年 | 1427篇 |
2019年 | 1160篇 |
2018年 | 1174篇 |
2017年 | 1357篇 |
2016年 | 1600篇 |
2015年 | 1720篇 |
2014年 | 3335篇 |
2013年 | 2896篇 |
2012年 | 3497篇 |
2011年 | 3530篇 |
2010年 | 2542篇 |
2009年 | 2657篇 |
2008年 | 2390篇 |
2007年 | 3177篇 |
2006年 | 2679篇 |
2005年 | 2165篇 |
2004年 | 1822篇 |
2003年 | 1810篇 |
2002年 | 1431篇 |
2001年 | 1242篇 |
2000年 | 1008篇 |
1999年 | 768篇 |
1998年 | 499篇 |
1997年 | 398篇 |
1996年 | 363篇 |
1995年 | 282篇 |
1994年 | 224篇 |
1993年 | 161篇 |
1992年 | 135篇 |
1991年 | 108篇 |
1990年 | 100篇 |
1989年 | 66篇 |
1988年 | 43篇 |
1987年 | 26篇 |
1986年 | 23篇 |
1985年 | 37篇 |
1984年 | 36篇 |
1983年 | 26篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 13篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1975年 | 4篇 |
1959年 | 4篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
RRN Sailaja 《Polymer International》2005,54(12):1589-1598
Lignin was graft copolymerized with methyl methacrylate using manganic pyrophosphate as initiator. This modified lignin was then blended (up to 50 wt%) with low density polyethylene (LDPE) using a small quantity of poly[ethylene‐co‐(glycidyl methacrylate)] (PEGMA) compatibilizer. The mechanical properties of the blend were substantially improved by using modified lignin in contrast to untreated lignin. Differential scanning calorimetry studies showed loss of crystallinity of the LDPE phase owing to the interaction between the blend components. Thermogravimetric analysis showed higher thermal stability of modified lignin in the domain of blend processing. This suggested that there is scope for useful utilization of lignin, which could also lead to the development of eco‐friendly products. Copyright © 2005 Society of Chemical Industry 相似文献
22.
氨氮监测采用预蒸馏处理后,比色测定结果明显偏低。在样品预蒸馏处理过程中,硼酸作为吸收液,使显色时溶液pH值偏低,导致显色不充分是其主要影响因素。通过采取增加显色剂加入量的方法,解决了显色pH值偏低的问题,得到满意的测定结果。 相似文献
23.
24.
25.
26.
A. K. Srivastava Ram M. Shrestha S. C. Srivastava Rabin Shrestha Dharam Paul 《国际能源研究杂志》2003,27(7):671-685
The power sector in India at present comprises of five separate regional electricity grids having practically no integrated operation in between them. This study analyses the utility planning, environmental and economical effects of integrated power sector development at the national level in which the regional electric grids are developed and operated as one integrated system. It also examines the effects of selected CO2 emission reduction targets in the power sector and the role of renewable power generation technologies in India. The study shows that the integrated development and operation of the power system at the national level would reduce the total cost including fuel cost by 4912 million $, total capacity addition by 2784 MW, while the emission of CO2, SO2 and NOx would be reduced by 231.6 (1.9%), 0.8 (0.9%), 0.4 (1.2%) million tons, respectively, during the planning horizon. Furthermore, the study shows that the expected unserved energy, one of the indices of generation system reliability, would decrease to 26 GWh under integrated national power system from 5158 GWh. As different levels of CO2 emission reduction targets were imposed, there is a switching of generation from conventional coal plants to gas fired plants, clean coal technologies and nuclear based plants. As a result the capacity expansion cost has increased. It was found that wind power plant is most attractive and economical in the Indian perspective among the renewable options considered (Solar, wind and biomass). Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
27.
浅谈建筑企业施工项目部的成本控制 总被引:1,自引:0,他引:1
指出控制工程项目的直接费用要从“四算对比”入手,介绍了施工项目的成本分析方法,阐述了施工项目内部控制的主要措施,以确保施工成本控制在计划成本范围内。 相似文献
28.
High crude oil prices and pollution problems have drawn attention to alternative vehicle technologies and fuels for the transportation sector. The question is: What are the benefits/costs of these technologies for society? To answer this question in a quantitative way, a web-based model (http://vehiclesandfuels.memebot.com) has been developed to calculate the societal life cycle costs, the consumer life cycle costs and the tax for different vehicle technologies. By comparing these costs it is possible to draw conclusions about the social benefit and the related tax structure. The model should help to guide decisions toward optimality, which refers to maximum social benefit. The model was applied to the case of Thailand. The life cycle cost of 13 different alternative vehicle technologies in Thailand have been calculated and the tax structure analyzed. 相似文献
29.
30.