全文获取类型
收费全文 | 2924篇 |
免费 | 98篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 136篇 |
综合类 | 3篇 |
化学工业 | 377篇 |
金属工艺 | 66篇 |
机械仪表 | 51篇 |
建筑科学 | 159篇 |
矿业工程 | 10篇 |
能源动力 | 89篇 |
轻工业 | 312篇 |
水利工程 | 19篇 |
石油天然气 | 13篇 |
武器工业 | 1篇 |
无线电 | 320篇 |
一般工业技术 | 359篇 |
冶金工业 | 369篇 |
原子能技术 | 18篇 |
自动化技术 | 737篇 |
出版年
2023年 | 16篇 |
2022年 | 28篇 |
2021年 | 44篇 |
2020年 | 27篇 |
2019年 | 48篇 |
2018年 | 86篇 |
2017年 | 62篇 |
2016年 | 53篇 |
2015年 | 47篇 |
2014年 | 99篇 |
2013年 | 200篇 |
2012年 | 185篇 |
2011年 | 147篇 |
2010年 | 181篇 |
2009年 | 185篇 |
2008年 | 219篇 |
2007年 | 137篇 |
2006年 | 169篇 |
2005年 | 146篇 |
2004年 | 78篇 |
2003年 | 103篇 |
2002年 | 87篇 |
2001年 | 45篇 |
2000年 | 53篇 |
1999年 | 63篇 |
1998年 | 53篇 |
1997年 | 50篇 |
1996年 | 38篇 |
1995年 | 34篇 |
1994年 | 31篇 |
1993年 | 33篇 |
1992年 | 25篇 |
1991年 | 18篇 |
1990年 | 23篇 |
1989年 | 25篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 20篇 |
1985年 | 17篇 |
1984年 | 20篇 |
1983年 | 22篇 |
1982年 | 10篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1976年 | 12篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1971年 | 4篇 |
排序方式: 共有3039条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Thomas S. Lowry John C. Bright Murray E. Close Christina A. Robb Paul A. White Stewart G. Cameron 《国际水资源开发杂志》2003,19(4):579-592
The primary objective of this project is to identify gaps, whether real or perceived, that hinder effective groundwater management in New Zealand. These gaps show as gaps in information, gaps in implementation, gaps in technological and management tools, and gaps in understanding of fundamental processes. The secondary objective is to propose a management strategy to close the identified gaps. Several methods are used to meet these objectives: surveys distributed to selected staff in each regional council; the review of various written reports; the analysis of land-use databases; and private consultation within each regional council. Results show that groundwater management in New Zealand is generally reactionary with the main gaps being in strategic planning and national guidelines. Most gaps appear to be predominantly information and implementation issues. In some cases there are gaps in the understanding of fundamental processes within an aquifer system, including the long-term effects of land-use on groundwater quality. An adaptive management approach is suggested as a means of closing these gaps. 相似文献
5.
Pax genes are expressed in specific patterns in the nervous system during development and in the adult. Recent findings suggest a link between the expression of Pax-2 and axonal guidance. Mice with a targeted deletion of Pax-2 are an excellent tool for studying axonal pathfinding at the molecular level, especially with respect to the optic chiasm. The date reviewed here suggest that Pax-2 regulates the expression of surface molecules involved in contact attraction and that the mutual regulation of the expression of Pax-2 and the Sonic hedgehog gene is of importance in the formation of the chiasm region. 相似文献
6.
7.
Steve Woolgar 《电信纪事》2002,57(3-4):159-179
The importance of rigorous research into the actual impact of the new Information and Communication Technologies (icts) on society in general cannot be overemphasised. The answer to questions concerning the precise effect ofiCTs on interpersonal relations, communication, social inclusion and exclusion, trust and identity are now central to discussion in both commercial and business fora. This paper examines the concept of the “virtual society“ in the light of the findings of the ESRC (Economic and Social Research Council) Virtual Society? Programme (1997–2002). The paper describes the need to rethink the actual approaches used in researching this area of social science at the same time as performing the analyses themselves. The author also highlights the requirement for future research to examine actual on the ground experiences. How are new technologies actually used and by whom? In addition, the author utilises his overview of this large body of research to put forward a useful guide for predicting the use of ICTs in practice. These “5 rules of virtuality” serve as pointers to the experiences that may be encountered in the development and implementation of new technologies. 相似文献
8.
9.
Steve Brightman 《今日电子》2008,(12)
采用WiMedia UWB标准的越来越多
WiMedia通用无线电平台是实现传输速率高达480Mb/s(更高的传输速率正在开发中)无线个人局域网(WPAN)的基础。这个平台并不局限于某一类应用,而是允许同时存在不同的协议适配层,如图1所示。WiMedia规范既规定了一些如无线USB之间相互通信的应用,也规定其他不相互通信的接口同时存在的应用。 相似文献
10.
The draft Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) contains Cryptosporidium log-inactivation CT tables (ozone-in-water concentration [residual], “C” times contact time, T). Depending on water temperature, Cryptosporidium CT values that are listed are 15 to 25 times greater than CT values for equivalent Giardia log-inactivation credit. The elevated operating dose required for Cryptosporidium log-inactivation credit has the potential to increase disinfection by-product (DBP) formation (e.g., bromate). Calculating CT value accurately will minimize ozone dose, which will decrease operating cost and lower DBP formation, and at the same time maintain disinfection protection through implementation of scientifically based safety factors. Various methods are available for calculating CT value. The method chosen depends largely on the available information concerning ozone residual characteristics and hydrodynamic features of the ozone contactor, plus local regulatory requirements. Four methods are discussed in this paper. Each method can be used to calculate Giardia, virus, and Cryptosporidium log-inactivation credit. 相似文献