全文获取类型
收费全文 | 5816篇 |
免费 | 93篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 38篇 |
综合类 | 1篇 |
化学工业 | 617篇 |
金属工艺 | 125篇 |
机械仪表 | 101篇 |
建筑科学 | 117篇 |
矿业工程 | 5篇 |
能源动力 | 71篇 |
轻工业 | 283篇 |
水利工程 | 19篇 |
石油天然气 | 8篇 |
无线电 | 540篇 |
一般工业技术 | 699篇 |
冶金工业 | 2948篇 |
原子能技术 | 33篇 |
自动化技术 | 312篇 |
出版年
2021年 | 34篇 |
2019年 | 26篇 |
2018年 | 38篇 |
2017年 | 28篇 |
2016年 | 39篇 |
2015年 | 30篇 |
2014年 | 52篇 |
2013年 | 147篇 |
2012年 | 90篇 |
2011年 | 95篇 |
2010年 | 99篇 |
2009年 | 116篇 |
2008年 | 121篇 |
2007年 | 115篇 |
2006年 | 101篇 |
2005年 | 101篇 |
2004年 | 86篇 |
2003年 | 101篇 |
2002年 | 75篇 |
2001年 | 91篇 |
2000年 | 114篇 |
1999年 | 163篇 |
1998年 | 919篇 |
1997年 | 532篇 |
1996年 | 360篇 |
1995年 | 217篇 |
1994年 | 181篇 |
1993年 | 203篇 |
1992年 | 66篇 |
1991年 | 92篇 |
1990年 | 101篇 |
1989年 | 97篇 |
1988年 | 69篇 |
1987年 | 82篇 |
1986年 | 64篇 |
1985年 | 86篇 |
1984年 | 69篇 |
1983年 | 65篇 |
1982年 | 49篇 |
1981年 | 68篇 |
1980年 | 63篇 |
1979年 | 43篇 |
1978年 | 31篇 |
1977年 | 104篇 |
1976年 | 158篇 |
1975年 | 40篇 |
1974年 | 36篇 |
1973年 | 45篇 |
1972年 | 23篇 |
1970年 | 24篇 |
排序方式: 共有5917条查询结果,搜索用时 437 毫秒
161.
Changes in the beam profile of the CO2 laser 10R(26) line, caused by transmission through, and absorption by, CDF3 were studied using an array of pyroelectric detectors. During the propagation of the laser beam through CDF3, nonlinear absorption and self-defocusing of the beam have both been determined from measurements of the effect on the exit beam of fluence, radiant energy, CDF3 pressure, transmission cell length, and distance from the exit of the cell to the detector array. 相似文献
162.
The creep properties of a standard doloma brick (containing 40% MgO) and a magnesia-enriched doloma product (containing 60% MgO) have been compared with the behaviour of CaO-MgO samples having compositions and microstructures similar to those of the pellet raw materials used for manufacture of the fired doloma refractories. The creep strength is shown to be improved not only by magnesia enrichment but also by reducing the impurity levels, particularly the Fe2O3 content. 相似文献
163.
Sodium-alumina electrolyte tubes were prepared from spray dried precursor powders with additions of 2, 5, 10 and 15 wt % ZrO2 made by the sodium zirconate route. The thermal shock behaviour of ring segments cut from the tubes was examined by quenching into water at 0° C. At the 2% ZrO2 level the dispersed ZrO2 particle size was low, <0.5m, and the tetragonal phase was retained. For higher weight fractions, particle coarsening during the-alumina sintering schedule was extensive and the large particles transformed to monoclinic on cooling. At the 15% ZrO2 level the-alumina had a slightly reduced strength and high resistance to thermal shock and to thermal shock damage, quenching into water from 800° C effecting only a 43% reduction in strength. These observations are consistent with the effects of microcracking in the vicinity of second phase ZrO2 particles. 相似文献
164.
165.
Mode matching for a passive resonant ring laser gyroscope 总被引:1,自引:0,他引:1
An analytical method of matching the mode of an input laser to the lowest-order mode of a passive resonant ring laser gyro is described, as are the steps in determining the location and focal length of cylindrical mode matching lenses. Results were obtained with no mode matching, with a compromise spherical lens, with horizontal mode matching only, and with the proper cylindrical mode matching lenses. Compared with no mode matching, the latter case shows that the amplitude of the lowest-order mode is increased approximately 2.5 times. In addition, the number and intensity of higher-order modes are reduced to near zero, and the relative intensity of the lowest-order mode to the higher-order mode increased from approximately 5 to approximately 60 times greater. 相似文献
166.
Coastal water protection the Navy way 总被引:1,自引:0,他引:1
167.
Mladejovsky Michael G. Eddington Donald K. Evans Jerald R. Dobelle William H. 《IEEE transactions on bio-medical engineering》1976,(4):286-296
Electrical stimulation of the visual cortex of the brain results in punctate photic sensations called ``phosphenes.' This suggests the concept of producing artificial vision for the blind by implanting arrays of electrodes, producing scoreboard-like displays. Electrical stimulation of the cochlea, VIIIth nerve, and auditory cortex produces analogous auditory sensations called ``audenes,' which might be used to provide artificial hearing for the deaf. 相似文献
168.
In 2002, over a million refrigerated road vehicles, 400,000 refrigerated containers and many thousands of other forms of refrigerated transport systems are used to distribute chilled and frozen foods throughout the world. All these transportation systems are expected to maintain the temperature of the food within close limits to ensure its optimum safety and high quality shelf life.Increasingly, modelling is being used to aid the design and optimisation of food refrigeration systems. Much of this effort has concentrated on the modelling of refrigeration processes that change the temperature of the food such as chilling, freezing and thawing. The purpose of a refrigerated transport system is to maintain the temperature of the food and appears to have attracted less attention from modellers. This paper reviews the work that has been carried out specifically on the modelling of food temperature, microbial growth and other parameters in the transportation of food. 相似文献
169.
Amorphous dihalonaphthalenes that are prepared by vacuum deposition onto a cold Al2O3 surface form electronically excited dimers when optically pumped, and their emission is characteristically red-shifted, broad and featureless compared to the monomeric fluorescence. If the surface is heated, the adlayer undergoes a disorder-to-order transition at a temperature characteristic of the molecule. Since pure crystalline dihalonaphthalenes typically fluoresce and do not exhibit excimeric features, the transition was studied by taking advantage of the changes in the spectral characteristics of the adlayer. These included transmittance, and emission from fluorescence and excimer. The combination of these methods allowed a close look at the surface dynamics of molecules on the surface of Al2O3 as the adlayer was heated from the deposition temperature to desorption.If a bilayer is formed by depositing water onto the surface with the organic adlayer on top, water, with its lower desorption energy, can be made to percolate into the organic layer. The optical probes indicate that the water clearly associates with the organic molecules while the excess water desorbs. By varying the coverage of either the water or the dihalonaphthalene, the stoichiometric composition of the cluster can be determined and are reported here. 相似文献
170.
Blenkhorn P. Evans D. G. 《IEEE transactions on neural systems and rehabilitation engineering》2006,14(4):501-504
This paper presents the architecture of, and the techniques used to build, a screen magnifier for visually impaired people that uses the "high-level" features of the Microsoft Windows operating system. The magnifier uses information from the Desktop Window as its source and overlays this with a topmost, transparent, layered window that contains the magnified image. Issues concerning cursor enlargement, tooltip suppression, and focus tracking are discussed. A stable magnifier results that does not need to use the "dirty" low-level techniques that are typically used to build screen magnifiers. The only known problem of the magnifier is that it fails to suppress the original, unmagnified cursor of the few applications that use custom cursors 相似文献