全文获取类型
收费全文 | 20953篇 |
免费 | 570篇 |
国内免费 | 28篇 |
专业分类
电工技术 | 278篇 |
综合类 | 16篇 |
化学工业 | 3899篇 |
金属工艺 | 314篇 |
机械仪表 | 378篇 |
建筑科学 | 1220篇 |
矿业工程 | 117篇 |
能源动力 | 585篇 |
轻工业 | 1597篇 |
水利工程 | 179篇 |
石油天然气 | 205篇 |
武器工业 | 1篇 |
无线电 | 1513篇 |
一般工业技术 | 3269篇 |
冶金工业 | 5137篇 |
原子能技术 | 194篇 |
自动化技术 | 2649篇 |
出版年
2022年 | 130篇 |
2021年 | 242篇 |
2020年 | 186篇 |
2019年 | 247篇 |
2018年 | 289篇 |
2017年 | 285篇 |
2016年 | 345篇 |
2015年 | 259篇 |
2014年 | 417篇 |
2013年 | 1229篇 |
2012年 | 739篇 |
2011年 | 961篇 |
2010年 | 748篇 |
2009年 | 737篇 |
2008年 | 948篇 |
2007年 | 958篇 |
2006年 | 776篇 |
2005年 | 790篇 |
2004年 | 635篇 |
2003年 | 634篇 |
2002年 | 575篇 |
2001年 | 405篇 |
2000年 | 351篇 |
1999年 | 379篇 |
1998年 | 590篇 |
1997年 | 464篇 |
1996年 | 436篇 |
1995年 | 411篇 |
1994年 | 334篇 |
1993年 | 379篇 |
1992年 | 312篇 |
1991年 | 205篇 |
1990年 | 277篇 |
1989年 | 319篇 |
1988年 | 231篇 |
1987年 | 256篇 |
1986年 | 260篇 |
1985年 | 316篇 |
1984年 | 308篇 |
1983年 | 262篇 |
1982年 | 256篇 |
1981年 | 242篇 |
1980年 | 200篇 |
1979年 | 207篇 |
1978年 | 199篇 |
1977年 | 219篇 |
1976年 | 217篇 |
1975年 | 195篇 |
1974年 | 176篇 |
1973年 | 157篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The effects of glycol methacrylate as a dehydrating agent on the dimensional changes of liver tissue
The dimensional changes of liver sections during the course of processing with glycol methacrylate (GMA) or with ethanol are described. Tissue processing with ethanol served as a control. During prolonged processing steps (24 h each), linear shrinkage of tissue specimens dehydrated with GMA at room temperature was 13.2%. Subsequent infiltration with GMA resulted in trivial swelling, and polymerization in slight shrinkage (2.3%). In comparison, processing with cold GMA resulted in shrinkage during dehydration (about 10.8%), a slight swelling in pure GMA, followed by shrinkage during polymerization (2.2%). Short routine processing schedules resulted in similar shrinkage/swelling patterns, although precise values differed slightly. In all experiments, ethanolic dehydration resulted in smaller dimensional tissue changes than did GMA dehydration. The dimensional changes of tissue sections during stretching on water, mounting and drying compensated for the major part of the shrinkage manifested during processing. 相似文献
102.
It is proposed that when solving an arithmetic word problem, unsuccessful problem solvers base their solution plan on numbers and keywords that they select from the problem (the direct translation strategy), whereas successful problem solvers construct a model of the situation described in the problem and base their solution plan on this model (the problem-model strategy). Evidence for this hypothesis was obtained in 2 experiments. In Experiment 1, the eye fixations of successful and unsuccessful problem solvers on words and numbers in the problem statement were compared. In Experiment 2, the degree to which successful and unsuccessful problem solvers remember the meaning and exact wording of word problems was examined. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
103.
Timothy G. Trucano Dennis E. Grady Glenn D. Kubiak Marlin E. Kipp Richard E. Olson Archie Farnsworth 《International Journal of Impact Engineering》1995,17(4-6):873-890
xtreme
ltra
iolet
ithography (EUVL) seeks to apply radiation in a wavelength region centered near 13 nm to produce microcircuits having feature sizes 0.1 micron or less. A critical requirement for the commercial application of this technology is the development of an economical, compact source of this radiation which is suitable for lithographic applications. A good candidate is a laser-plasma source, which is generated by the interaction of an intermediate intensity laser pulse (up to 1012 W/cm2) with a metallic target. While such a source has radiative characteristics which satisfy the needs of an EUVL source, the debris generated during the laser-target interaction strikes at the economy of the source. Here, we review the use of concepts and computer modeling, originally developed for hypervelocity impact analysis, to study this problem. 相似文献
104.
105.
The constraint satisfaction problem is known to be NP-hard in general, but a number of restrictions of the problem have been identified over the years which ensure tractability. This paper introduces two simple methods of combining two or more tractable classes over disjoint domains, in order to synthesise larger, more expressive tractable classes. We demonstrate that the classes so obtained are genuinely novel, and have not been previously identified. In addition, we use algebraic techniques to extend the tractable classes which we identify, and to show that the algorithms for solving these extended classes can be less than obvious. 相似文献
106.
Green R.P.M. Crofts G.J. Hubbard W. Udaiyan D. Dong Hwan Kim Damzen M.J. 《Quantum Electronics, IEEE Journal of》1996,32(3):371-377
We demonstrate that self-induced gain gratings can provide nonlinear optical feedback that results in single frequency selection and passive self Q-switching of a conventional linear laser cavity. An experimental Nd:YAG laser system is described that yields a temporally-smooth 20 ns pulse at 1.064 μm. In addition, we show that the feedback has phase-conjugate properties that permit “flower-like” mode formation even though the azimuthal symmetry of the cavity is broken 相似文献
107.
108.
Richard Kerner 《Computational Materials Science》1994,2(3-4):500-508
109.
110.