全文获取类型
收费全文 | 1864篇 |
免费 | 4篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 3篇 |
综合类 | 4篇 |
化学工业 | 155篇 |
金属工艺 | 3篇 |
机械仪表 | 97篇 |
建筑科学 | 103篇 |
矿业工程 | 5篇 |
轻工业 | 527篇 |
水利工程 | 18篇 |
石油天然气 | 35篇 |
武器工业 | 2篇 |
无线电 | 115篇 |
一般工业技术 | 696篇 |
冶金工业 | 11篇 |
原子能技术 | 4篇 |
自动化技术 | 93篇 |
出版年
2012年 | 171篇 |
2011年 | 209篇 |
2010年 | 42篇 |
2009年 | 15篇 |
2008年 | 157篇 |
2007年 | 138篇 |
2006年 | 143篇 |
2005年 | 122篇 |
2004年 | 107篇 |
2003年 | 108篇 |
2002年 | 84篇 |
2001年 | 66篇 |
2000年 | 74篇 |
1999年 | 41篇 |
1998年 | 25篇 |
1997年 | 29篇 |
1996年 | 26篇 |
1995年 | 28篇 |
1994年 | 27篇 |
1993年 | 18篇 |
1992年 | 19篇 |
1991年 | 26篇 |
1990年 | 15篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 10篇 |
1986年 | 21篇 |
1985年 | 21篇 |
1984年 | 28篇 |
1983年 | 15篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1959年 | 3篇 |
1958年 | 4篇 |
1957年 | 1篇 |
1956年 | 3篇 |
1955年 | 1篇 |
1954年 | 4篇 |
1948年 | 3篇 |
1946年 | 1篇 |
排序方式: 共有1871条查询结果,搜索用时 0 毫秒
161.
Lutolf RM Vieli A Basler S 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1989,36(5):494-506
For the purpose of the quantitative assessment of subtle disease processes in the cardiovascular system an electronically steered sector scanner that combines echographic imaging and Doppler blood velocity measurements has been developed. The integrated operation of a fast Fourier transform (FFT) Doppler signal processor for the simultaneous blood velocity evaluation of 64 individual gates is among the specific design goals. The instrument incorporates an unusually high degree of digital signal processing, which allows for high integration density, easy manufacturing and high reliability in future designs. The complex Doppler spectra are determined for each of the 64 Doppler gates in real time, and the subsequent computation of the first moment provides a reliable estimate of the mean blood flow velocities at the respective locations. The instantaneous velocity profile along the Doppler beam is displayed together with the calculated volume flow rate and a range-selected complete frequency spectrum. Results of both in vitro and in vivo tests indicate that in the future, a higher degree of digital signal processing could be implemented in complex ultrasonic systems. 相似文献
162.
Haralick RM Shapiro LG 《IEEE transactions on pattern analysis and machine intelligence》1979,(2):173-184
In this first part of a two-part paper we introduce a general consistent labeling problem based on a unit constraint relation T containing N-tuples of units which constrain one another, and a compatibility relation R containing N-tuples of unit-label pairs specifying which N-tuples of units are compatible with which N-tuples of labels. We show that Latin square puzzles, finding N-ary relations, graph or auto-mata homomorphisms, graph colorings, as well as determining satisfiability of propositional logic statements and solving scene and edge labeling problems, are all special cases of the general consistent labeling problem. We then discuss the various approaches that researchers have used to speed up the tree search required to find consistent labelings. Each of these approaches uses a particular look-ahead operator to help eliminate backtracking in the tree search. Finally, we define the ?KP two-parameter class of look-ahead operators which includes, as special cases, the operators other researchers have used. 相似文献
163.
164.
165.
166.
168.
169.
170.
This study reports the synthesis of the first functional cleavable detergent designed specifically for applications in mass spectrometry. Upon cleavage, two inert compounds and the MALDI matrix are formed, eliminating sources of potential interference originating from traditional cleavable detergents. Analysis of peptides demonstrates that MALDI matrix generated in situ results in MALDI spectra equivalent to those prepared using established protocols. Analysis of the membrane protein diacylglycerol kinase was accomplished using the combination detergent/MALDI matrix. Applications of the functional cleavable detergents to the profiling of whole cell lysates results in increased signal-to-noise ratios of many ions and the detection of additional proteins previously not observed. 相似文献