全文获取类型
收费全文 | 9397篇 |
免费 | 660篇 |
国内免费 | 331篇 |
专业分类
电工技术 | 390篇 |
综合类 | 412篇 |
化学工业 | 1686篇 |
金属工艺 | 450篇 |
机械仪表 | 439篇 |
建筑科学 | 627篇 |
矿业工程 | 172篇 |
能源动力 | 309篇 |
轻工业 | 589篇 |
水利工程 | 119篇 |
石油天然气 | 288篇 |
武器工业 | 37篇 |
无线电 | 1506篇 |
一般工业技术 | 1322篇 |
冶金工业 | 730篇 |
原子能技术 | 90篇 |
自动化技术 | 1222篇 |
出版年
2024年 | 24篇 |
2023年 | 126篇 |
2022年 | 232篇 |
2021年 | 321篇 |
2020年 | 201篇 |
2019年 | 201篇 |
2018年 | 259篇 |
2017年 | 266篇 |
2016年 | 269篇 |
2015年 | 263篇 |
2014年 | 395篇 |
2013年 | 568篇 |
2012年 | 523篇 |
2011年 | 650篇 |
2010年 | 565篇 |
2009年 | 540篇 |
2008年 | 587篇 |
2007年 | 473篇 |
2006年 | 475篇 |
2005年 | 356篇 |
2004年 | 315篇 |
2003年 | 309篇 |
2002年 | 276篇 |
2001年 | 229篇 |
2000年 | 217篇 |
1999年 | 228篇 |
1998年 | 290篇 |
1997年 | 218篇 |
1996年 | 210篇 |
1995年 | 157篇 |
1994年 | 132篇 |
1993年 | 98篇 |
1992年 | 64篇 |
1991年 | 52篇 |
1990年 | 42篇 |
1989年 | 40篇 |
1988年 | 32篇 |
1987年 | 28篇 |
1986年 | 24篇 |
1985年 | 16篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 15篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1976年 | 13篇 |
1975年 | 9篇 |
1974年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
Ming-Ching Lee Chan-Ji Lai Jan-Mou Leu William J. Plant William C. Keller Ken Hayes 《Flow Measurement and Instrumentation》2002,13(5-6):265-270
This article describes a non-contact method for measuring surface velocity and discharge in a natural channel. The X-band pulse (9.36 GHz) radar, developed by the Applied Physics Laboratory of the University of Washington, was used to scan instantaneously the lateral distribution of surface velocity across a river section, according to Bragg scattering from short waves produced by turbulent boils on the surface of the river. Based on the assumption that the vertical velocity distribution follows a universal power or logarithmic law, the discharges were estimated. 相似文献
43.
44.
45.
为使北京谱仪端盖族射计数器更好地工作在自猝灭流光SQS模式下,提高其能量分辨以及线性等指标,用Ar,CO2,Lsobutane三元工作气体对探测器的工作性能进行了仔细研究,找出了一适合于主雇地数器的工作气体,此外,还研究了异丁的纯度对探测器性能的影响。 相似文献
46.
47.
A Saccharomyces cerevisiae sequence cloned by serendipity was found to encode a protein that is a new member of the Ypt/Rab monomeric G-protein family. This sequence shows high homology to the yeast genes SEC4 and YPT1 and, like SEC4 and YPT1, is essential for viability. The sequence was localized to chromosome V based upon hybridization to pulse-field gel-separated yeast chromosomes. The sequence has been deposited in the GenBank data library under Accession Number L17070. 相似文献
48.
49.
An analytical expression for both band-to-band and band-trap-band indirect tunnelings is used to study the gate-induced drain leakage (GIDL) current of MOSFETs measured before and after hot-carrier stress. The voltage and temperature dependence of GIDL are characterized. Both results show that interface traps situated near the midgap participate in the conduction of GIDL, and band-trap-band indirect tunneling could be the major mechanism. This is further supported by the fact that the percentage increase in GIDL induced by hot-carrier stress is about the same as the corresponding increase in interface-trap density. On the other hand, under low-field conditions, trap-assisted Poole–Frenkle emission dominates over tunneling for temperatures even well below room temperature. 相似文献
50.
Tests of univariate and bivariate stochastic ageing 总被引:1,自引:0,他引:1
Concepts of ageing describe how a population of units or systems improves or deteriorates with age. Many classes of life distributions are categorized and defined in the literature according to their ageing properties. An important aspect of such classifications is that the exponential distribution is nearly always a member of each class. The notion of stochastic ageing is important in any reliability analysis, and many test statistics have been developed for testing exponentiality against various ageing alternatives. This paper is an overview of these developments. The author begins with a table of ageing classes together with key references, followed by a brief discussion on the characterization of exponentiality. Test procedures are summarized, and followed by the main review. Tests of exponentiality against other alternatives are explained for randomly censored data. Finally, tests of multivariate ageing properties are listed. Some of the life classes have been derived more recently and, as far as is known, no test statistics have been proposed. On the other hand, several tests are available for some classes. Relative efficiency of a test is discussed whenever appropriate 相似文献