全文获取类型
收费全文 | 5382篇 |
免费 | 58篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 53篇 |
综合类 | 6篇 |
化学工业 | 1120篇 |
金属工艺 | 106篇 |
机械仪表 | 106篇 |
建筑科学 | 330篇 |
矿业工程 | 11篇 |
能源动力 | 124篇 |
轻工业 | 495篇 |
水利工程 | 37篇 |
石油天然气 | 24篇 |
无线电 | 289篇 |
一般工业技术 | 976篇 |
冶金工业 | 1040篇 |
原子能技术 | 61篇 |
自动化技术 | 672篇 |
出版年
2022年 | 54篇 |
2021年 | 65篇 |
2020年 | 55篇 |
2019年 | 93篇 |
2018年 | 115篇 |
2017年 | 77篇 |
2016年 | 94篇 |
2015年 | 61篇 |
2014年 | 104篇 |
2013年 | 348篇 |
2012年 | 167篇 |
2011年 | 213篇 |
2010年 | 197篇 |
2009年 | 180篇 |
2008年 | 207篇 |
2007年 | 204篇 |
2006年 | 191篇 |
2005年 | 169篇 |
2004年 | 149篇 |
2003年 | 157篇 |
2002年 | 129篇 |
2001年 | 104篇 |
2000年 | 93篇 |
1999年 | 84篇 |
1998年 | 153篇 |
1997年 | 126篇 |
1996年 | 88篇 |
1995年 | 91篇 |
1994年 | 98篇 |
1993年 | 86篇 |
1992年 | 68篇 |
1991年 | 70篇 |
1990年 | 70篇 |
1989年 | 76篇 |
1988年 | 73篇 |
1987年 | 48篇 |
1986年 | 65篇 |
1985年 | 71篇 |
1984年 | 82篇 |
1983年 | 69篇 |
1982年 | 67篇 |
1981年 | 68篇 |
1980年 | 53篇 |
1979年 | 65篇 |
1978年 | 75篇 |
1977年 | 60篇 |
1976年 | 61篇 |
1975年 | 44篇 |
1974年 | 41篇 |
1973年 | 45篇 |
排序方式: 共有5450条查询结果,搜索用时 0 毫秒
1.
2.
Roger L. Kemp 《Cities》1985,2(3):252-255
Since the early 1970s, local governments in the USA have faced limited tax income combined with double-digit inflation. As a result, every local service from fire prevention to recreation has had to be closely scrutinized. Local administrators and politicians have evolved new and innovative retrenchment management policies to respond to both the demands of citizens and the fewer dollars available. A combination of denial of new programmes and public sector pay austerity, with public education and use of community organizations is providing ways to stretch limited funds. The reality in many communities across the USA is that local government and its services will not be growing in the future. 相似文献
3.
Sabha Kesraoui-Ouki Christopher R. Cheeseman Roger Perry 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,59(2):121-126
This paper assesses the potential of natural zeolite utilization as a low-cost ion-exchange and sorbent material in pollution control and recovery of metals. The improvement of the purity of natural zeolites coupled with their chemical modification capabilities in order to provide specific properties may provide a cost-effective alternative for the treatment of heavy metal contaminated soil and water. The application of natural zeolites in industrial pollution control is becoming important and the level of technical effort is increasingly expanding. The extent of application is unlikely to be related solely to their low cost, but also to improved properties and performance characteristics, which will advance the practical implementation of natural zeolites' technology. 相似文献
5.
Toshiaki Nishihata Mayumi Ishizaka Sigeharu Yokohama Alice C. Martino Roger E. Gordon 《Drug development and industrial pharmacy》1993,19(20):2679-2698
The effects of particle size and food on the absolute bioavailability of U-78875 in dogs after oral administration of either a suspension or tablet dosage form were investigated. A reduction of particle size caused a significant increase in bioavailability along with an increase in dissolution rate. Additionally, both suspension and tablet dosage forms administered after food caused an increase in bioavailability. Thus, to accelerate drug dissolution, a reduction of U-78875 particle size from the unmilled state is important for the optimization of formulation compositions. To increase the bioavailability of U-78875, postprandial dosing should be considered. 相似文献
6.
The issue of generic scaling laws able to adequately predict (within better than 20%) cratering in semi-infinite targets and perforations through finite thickness targets was revisited. The approach used was to apply physical logic for hydrodynamics in a consistent manner able to account for chunky-body impacts such that the only variables needed are those directly related to known material properties for both the impactor and target. The analyses were compared and verified versus CTH hydrodynamic code calculations and existing experimental data. Comparisons with previous scaling laws were also performed to identify which (if any) were good for generic purposes. This paper is a short synopsis of the full report [1] available through the NASA Langley Research Center, LDEF Science Office. 相似文献
7.
MRI techniques were developed and employed for non-destructive and noninvasive study of seedcoat cracking in low moisture soybean kernels during heated air drying. Proton density image and transient moisture distribution profile of a single soybean kernel can be obtained using MRI. These MRI techniques proved to be particularly useful for the continuous observation of initiation and propagation of seedcoat cracking during the entire period of drying process without interruption.
The proton density images of soybean kernels showed that seedcoat cracking was initiated perpendicular to the long axis of the kernel near the hilum. The transient moisture distribution profiles in soybean kernels during drying indicate that moisture gradient developed during drying was higher in the seedcoat than in the cotyledon. Drying temperature and initial average moisture content were positively correlated with the soyhean seedcoat crackig. The location of the 相似文献
The proton density images of soybean kernels showed that seedcoat cracking was initiated perpendicular to the long axis of the kernel near the hilum. The transient moisture distribution profiles in soybean kernels during drying indicate that moisture gradient developed during drying was higher in the seedcoat than in the cotyledon. Drying temperature and initial average moisture content were positively correlated with the soyhean seedcoat crackig. The location of the 相似文献
8.
9.
10.
Roger Zetter 《Cities》1985,2(1):24-33
This profile of Nicosia, the capital of Cyprus, focuses on a crucial aspect of its historical growth and emerging planning responses: the issue of urban land. In Nicosia, as elsewhere, an understanding of land markets and the actors and agencies involved in development processes is indispensable for the management of urban change and the effective implementation of planning strategies for future growth. The provision of land which is affordable and available to urban dwellers has become a central issue, especially in the developing world. Accordingly, the relationship between planning policies and land issues, so long ignored by many planning systems, has become the new focus of current practice and research. 相似文献