全文获取类型
收费全文 | 5266篇 |
免费 | 3898篇 |
国内免费 | 488篇 |
学科分类
工业技术 | 9652篇 |
出版年
2023年 | 331篇 |
2022年 | 815篇 |
2021年 | 1035篇 |
2020年 | 1006篇 |
2019年 | 452篇 |
2018年 | 422篇 |
2017年 | 269篇 |
2016年 | 375篇 |
2015年 | 138篇 |
2014年 | 62篇 |
2013年 | 164篇 |
2012年 | 118篇 |
2011年 | 171篇 |
2010年 | 132篇 |
2009年 | 141篇 |
2008年 | 122篇 |
2007年 | 124篇 |
2006年 | 116篇 |
2005年 | 220篇 |
2004年 | 215篇 |
2003年 | 147篇 |
2002年 | 131篇 |
2001年 | 70篇 |
2000年 | 187篇 |
1999年 | 459篇 |
1998年 | 85篇 |
1997年 | 109篇 |
1996年 | 120篇 |
1995年 | 149篇 |
1994年 | 249篇 |
1993年 | 184篇 |
1992年 | 209篇 |
1991年 | 218篇 |
1990年 | 278篇 |
1989年 | 284篇 |
1988年 | 207篇 |
1987年 | 25篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1977年 | 4篇 |
1973年 | 3篇 |
1972年 | 30篇 |
1971年 | 11篇 |
1970年 | 4篇 |
1969年 | 5篇 |
1968年 | 4篇 |
1967年 | 4篇 |
1966年 | 3篇 |
1963年 | 3篇 |
排序方式: 共有9652条查询结果,搜索用时 0 毫秒
1.
欧洲主要电信运营商所处国度的经济和人口布局情况不同,竞争环境也有差别,在专线资费方面的做法也有许多不同之处。考虑到地区之间竞争的差异。目前多数国家都取消了地区交叉补贴的做法,但还有一部分国家仍然坚持统一费率。在资费方面的基本促销手段为接合同年限和用户的支出额打折。从2000年到2003年资费演变的基本情况是;接入费扣2Mbit/s以下较低速率的专线租费保持平稳略有下降,较高速率专线的租费则有较大的下调幅虚。 相似文献
2.
本工艺是对原有工艺的改进,突破了原有布帮鞋不能采用无浆贴合的局限性,对原有工艺中的不足有了很大的改进,提高了生产效率,改善了鞋子外观质量,增加了鞋子的美观性。 相似文献
3.
This study, which is based on responses from over 300 individuals in England and Wales, explores how a willingness to use a water-recycling system of specific configuration varies against a number of factors which are linked to system design, system scale, system context, and water-conservation behaviour. Findings show that there is broad willingness to accept in-house water recycling provided that public health is not compromised. 相似文献
4.
5.
Bernhard Steffen
Jens Knoop
《Theoretical computer science》1991,80(2):303-318Constant propagation, the replacement of program terms which represent a unique value at run time by their values, is a classical program optimization method. In spite of being treated for years, constant propagation still has been in the unsatisfactory phase of heuristics. We enhance the known constant propagation techniques to obtain an algorithm which is optimal for programs without loops. Fundamental is the introduction of a new decidable set of constants, the finite constants. This set has two different characterizations: a denotational one, which directly specifies our iterative algorithm and an operational one, which delivers the completeness or optimality of this algorithm for programs without loops. The algorithm is implemented in a commercial compiler project. 相似文献
6.
Kyle A. Crawford
Osama K. Eyada PhD PE
《Computers & Industrial Engineering》1989,17(1-4):298-302The worldwide proliferation of fraudulent materials has brought about the need for a new approach to the control of purchased material quality. Nuclear power, defense, aerospace and many other industries are affected by the supply of poor quality clones that presume to be original replacement parts. Safety considerations abound as these highly defective materials are used in systems that are critical to the preservation of human lives. Commonly utilized quality assurance programs have not effectively stopped the influx of fraudulent materials. These programs fail to concentrate inspection efforts on materials and inspection attributes that would effectively prevent the acceptance of fraudulent materials. herein a solution is presented to this problem in the form of an expert system application. Information commonly available in industry is formulated into a knowledge based system wherein advisories are given to the user regarding key purchased material receipt inspection strategies. 相似文献
7.
M. Reza Ziai
Dileep R. Sule
《Computers & Industrial Engineering》1991,21(1-4):385-389The paper describes a computerized facility layout designer, COMLAD II, for plant layout development. Besides developing an efficient layout, COMLAD II has useful features which allow fixing the departments, changing the shape of the departments and changing the length and width dimensions of the overall layout. 相似文献
8.
P. Worrall BEd MSc K. Peberdy BSc MSc H. McGinn BSc MSc 《Water and Environment Journal》1998,12(2):86-91
In 1993, the Wildfowl and Wetlands Trust constructed a demonstration reedbed treatment system at its Castle Espie Visitor Centre in Northern Ireland. The objectives of the project included (a) the treatment of septic-tank effluent, (b) the protection of water quality in Strangford Lough, and (c) the establishment of a research base for constructed wetland systems. Parallel beds of equally sized sub-surface and surface flow were constructed and planted, and a research project was initiated to provide data on performance. 相似文献
9.
L. Palermo Jr.
M. Rachid
W. S. Venturini 《Engineering Analysis with Boundary Elements》1992,9(4):359-363In this article the direct boundary element formulations of stretching and bending plate problems are combined together to solve thin walled structures and other similar frames. The final system is obtained by assuming each individual plane structural element as a subregion. After the necessary transforms of these equations they can be combined together taking into account the displacement compatibility and equilibrium conditions. 相似文献
10.
H. Hou J. C. Holste
B. E. Gammon
K. N. Marsh 《International Journal of Refrigeration》1992,15(6):365-371This paper reports densities of compressed R134a (1,1,1,2-tetrafluoroethane) determined by using a contiuously weighed pycnometer at 20 K intervals between 180 and 380 K at pressures from slightly greater than the vapour pressure to 70 MPa. The results are accurate to within ±0.1%. Saturated liquid densities derived by extrapolation from the experimental values agree with other reported values to within ±0.3%. 相似文献