全文获取类型
收费全文 | 395847篇 |
免费 | 4788篇 |
国内免费 | 1714篇 |
专业分类
电工技术 | 7709篇 |
综合类 | 353篇 |
化学工业 | 59471篇 |
金属工艺 | 17173篇 |
机械仪表 | 11396篇 |
建筑科学 | 10101篇 |
矿业工程 | 1328篇 |
能源动力 | 10316篇 |
轻工业 | 37642篇 |
水利工程 | 3340篇 |
石油天然气 | 4296篇 |
武器工业 | 5篇 |
无线电 | 47656篇 |
一般工业技术 | 72943篇 |
冶金工业 | 79614篇 |
原子能技术 | 7634篇 |
自动化技术 | 31372篇 |
出版年
2021年 | 2667篇 |
2019年 | 2491篇 |
2018年 | 4117篇 |
2017年 | 4046篇 |
2016年 | 4334篇 |
2015年 | 3282篇 |
2014年 | 5470篇 |
2013年 | 17432篇 |
2012年 | 9343篇 |
2011年 | 13162篇 |
2010年 | 10581篇 |
2009年 | 12023篇 |
2008年 | 12514篇 |
2007年 | 12553篇 |
2006年 | 11249篇 |
2005年 | 10451篇 |
2004年 | 10005篇 |
2003年 | 9726篇 |
2002年 | 9702篇 |
2001年 | 9875篇 |
2000年 | 9108篇 |
1999年 | 9838篇 |
1998年 | 25509篇 |
1997年 | 17981篇 |
1996年 | 13829篇 |
1995年 | 10369篇 |
1994年 | 8994篇 |
1993年 | 8811篇 |
1992年 | 6310篇 |
1991年 | 6161篇 |
1990年 | 5671篇 |
1989年 | 5594篇 |
1988年 | 5514篇 |
1987年 | 4753篇 |
1986年 | 4664篇 |
1985年 | 5485篇 |
1984年 | 4946篇 |
1983年 | 4547篇 |
1982年 | 4229篇 |
1981年 | 4275篇 |
1980年 | 4007篇 |
1979年 | 3887篇 |
1978年 | 3814篇 |
1977年 | 4664篇 |
1976年 | 6580篇 |
1975年 | 3287篇 |
1974年 | 3207篇 |
1973年 | 3222篇 |
1972年 | 2675篇 |
1971年 | 2468篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The trends in high density interconnection (HDI) multichip module (MCM) techniques that have the potential to reduce interconnection cost and production time are described. The implementation in laminated dielectric (MCM-L) technology of a workstation processor core illustrates current substrate technology capabilities. The design, routing, layout and thermal management of the processor core are described. Thin-film deposited dielectric (MCM-D) technology is discussed as a cost-effective method for future interconnection applications 相似文献
62.
Most divers and diving medicine specialists know that application of normobaric oxygen as first aid after a bubble disease incident is highly effective. However, as yet technical difficulties acted as a deterrent to using normobaric oxygen at the diving site. This can now be overcome by a newer technique. To be efficient, any therapy of bubble disease should follow three main principles: maximal partial pressure of inhaled oxygen (i.e. 100 kpa in normobaric, and 280 kpa in hyperbaric conditions); minimal partial pressure of inhaled nitrogen, which should ideally be near zero; immediate start of therapy, if possible at the diving site, but not later than 2 hours after the onset of the first symptoms. However, it has to be borne in mind that for an efficient normobaric oxygenation (100%), the standard apparatus design without oxygen reservoir is obsolete, for it offers at most 40% oxygen to the lungs. Currently the following technical approaches for an efficient normobaric oxygenation are available: open one-way systems with tightly fitting mask and oxygen reservoir bag (type Ambu or Leardal, etc.); open systems with on-demand regulation and tightly fitting mouth piece (type SCUBA, or Bird-respirator); closed systems with CO2 absorber (type oxygen rebreathing diving gear). The closed system is a genuine technical advance, because it needs 15 times less oxygen than open systems (about 90 liters oxygen for a 3-hours oxygenation run). Such an apparatus is thus of light weight, far less cumbersome, and nevertheless highly efficient. The therapy should start immediately at the site of the mishap and be maintained during the transport to the next HBO-unit (usually 3 to 6 hours).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
63.
Garner H.R. Balog R.P. Luebke K.J. 《IEEE engineering in medicine and biology magazine》2002,21(4):123-125
Given the enormous size of the genome and that there are potentially many other types of measurements we need to do to understand it, it has become necessary to pick and choose one's targets to measure because it is still impossible to evaluate the entire genome all at once. What has emerged is a need to have rapidly customizable microarrays. There are two dominant methods to accomplish custom microarray synthesis, Affymetrix-like microarrays manufactured using light projection rather than semiconductor-like masks used by Affymetrix to mass manufacture their GeneChip/sup TM/ arrays now, or the ink-jet printing method employed by Agilent. The manufacture of these custom Affymetrix-like microarrays can now be done on a digital optical chemistry (DOC) machine developed at the University of Texas Southwestern Medical Center, and this method offers much higher feature numbers and feature density than is possible with ink-jet printed arrays. On a microarray, each feature contains a single genetic measurement. The initial DOC prototype has been described in several publications, but that has now led to a second-generation machine. This machine reliably produces a number of arrays daily, has been deployed against a number of biomedical questions, is being used in new ways and has also led to a number of spin-off technologies. 相似文献
64.
Rapeseed protein concentrate (RC), prepared with 2% hexameta-phosphate, was tested for its functionality and performance in some foods. The RC had good nitrogen solubility, fat absorption, emulsification, and whipping capacities but poor water absorption and gelling properties. It increased the emulsion stability, and protein but lowered the fat content of wieners. It also increased the cooking yield, reduced the shrinkage and tenderized meat patties. Results were similar to soybean isolate except for the poorer color and flavor. The cooking yield of RC supplemented wieners was less than the all-meat control and soybean-supplemented wieners. A 9% RC dispersion mixed with an equal volume of eggwhite produced a meringue of comparable stability and texture to that of eggwhite alone. 相似文献
65.
Nagpal R. Zambonelli F. Sirer E.G. Chaouchi H. Smirnov M. 《Intelligent Systems, IEEE》2006,21(2):50-58
No generally accepted principles and guidelines currently exist to help engineers design local interaction mechanisms that result in a desired global behavior. However, several communities have developed ways of approaching this problem in the context of niched application areas. Because the ideas underlying these approaches are often obscured or underemphasized in technical papers, the authors review the role of self-organization in their work. They provide a better picture of the status of the emerging field of self-organizing systems or autonomic computing. 相似文献
66.
67.
Hayashi M. Tanaka H. Ohara K. Otani T. Suzuki M. 《Lightwave Technology, Journal of》2002,20(2):236-242
An all-optical multiplexing technique using wavelength division multiplexing (WDM)-time division multiplexing (TDM) conversion with an electroabsorption wavelength converter has been proposed and demonstrated. The effectiveness of this WDM-TDM conversion technique for various pulsewidth settings was experimentally investigated. The fluctuation of the signal performance, which was inevitably caused by the coherent crosstalk between adjacent pulses in the conventional optical time division multiplexing (OTDM) technique, were successfully suppressed, even in the case of wide pulse duration. High Q-factor performance has been maintained for a wide range of duty ration from 36% to 74%. By introducing this technique to the optical time division multiplexer, a highly stable and high-quality 40-Gb/s optical signal can be effectively produced without generating the short pulse or setting two tributaries at orthogonal polarization states, and without introducing high-speed electronics for signal multiplexing. The WDM-TDM conversion with an electroabsorption wavelength converter was extended to 60-Gb/s operation by using three 20-Gb/s tributaries. A clear eye opening was confirmed for a waveform after the WDM-TDM conversion of the 60-Gb/s signal 相似文献
68.
S. F. Edwards 《Polymer International》1985,17(2):122-125
Elasticity is discussed as an aspect of viscoelasticity, which is described by the tube model. The effects of both crosslinks and entanglements contribute to this model and a discussion of how these effects can be quantified is given. At high enough concentration, entanglements ensure the existence of elastic effects even without crosslinks, and a theory is presented on how this dynamical phase change comes about. 相似文献
69.
70.