全文获取类型
收费全文 | 3447篇 |
免费 | 137篇 |
国内免费 | 132篇 |
专业分类
电工技术 | 63篇 |
综合类 | 306篇 |
化学工业 | 501篇 |
金属工艺 | 195篇 |
机械仪表 | 173篇 |
建筑科学 | 46篇 |
矿业工程 | 27篇 |
能源动力 | 266篇 |
轻工业 | 92篇 |
水利工程 | 7篇 |
石油天然气 | 11篇 |
武器工业 | 10篇 |
无线电 | 623篇 |
一般工业技术 | 780篇 |
冶金工业 | 99篇 |
原子能技术 | 96篇 |
自动化技术 | 421篇 |
出版年
2023年 | 27篇 |
2022年 | 41篇 |
2021年 | 24篇 |
2020年 | 87篇 |
2019年 | 59篇 |
2018年 | 54篇 |
2017年 | 121篇 |
2016年 | 208篇 |
2015年 | 154篇 |
2014年 | 206篇 |
2013年 | 182篇 |
2012年 | 143篇 |
2011年 | 187篇 |
2010年 | 205篇 |
2009年 | 215篇 |
2008年 | 103篇 |
2007年 | 147篇 |
2006年 | 165篇 |
2005年 | 115篇 |
2004年 | 70篇 |
2003年 | 73篇 |
2002年 | 73篇 |
2001年 | 98篇 |
2000年 | 94篇 |
1999年 | 93篇 |
1998年 | 89篇 |
1997年 | 77篇 |
1996年 | 59篇 |
1995年 | 52篇 |
1994年 | 35篇 |
1993年 | 38篇 |
1992年 | 28篇 |
1991年 | 24篇 |
1990年 | 20篇 |
1989年 | 21篇 |
1988年 | 44篇 |
1987年 | 68篇 |
1986年 | 56篇 |
1985年 | 15篇 |
1984年 | 19篇 |
1983年 | 22篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1974年 | 5篇 |
1972年 | 7篇 |
1970年 | 5篇 |
排序方式: 共有3716条查询结果,搜索用时 0 毫秒
1.
We propose all printed and highly stable organic resistive switching device (ORSD) based on graphene quantum dots (G-QDs) and polyvinylpyrrolidone (PVP) composite for non-volatile memory applications. It is fabricated by sandwiching G-QDs/PVP composite between top and bottom silver (Ag) electrodes on a flexible substrate polyethylene terephthalate (PET) at ambient conditions through a cost effective and eco-friendly electro-hydrodynamic (EHD) technique. Thickness of the active layer is measured around 97 nm. The proposed ORSD is fabricated in a 3 × 3 crossbar array. It operates switching between high resistance state (HRS) and low resistance state (LRS) with OFF/ON ratio ∼14 for more than 500 endurance cycles, and retention time for more than 30 days. The switching voltage for set/reset of the devices is ±1.8 V and the bendability down to 8 mm diameter for 1000 cycles are tested. The elemental composition and surface morphology are characterized by XPS, FE-SEM, and microscope. 相似文献
2.
Measuring nonlinear optical response of a specific material in a mixture, not only leads to investigate the behavior of a particular component in various circumstances, but also can be a way to select suitable combination and optimum concentration of additives and therefore obtaining the maximum nonlinear optical signals. In this work, by using dual-arm Z-scan technique, the nonlinear refractive index of Disperse Red1 (DR1) organic dye molecules inside the core of prepared polymeric nanocapsules was measured among various materials which prepared nanocapsules were made of them. Then the measured value was compared with nonlinear refractive index of DR1 solved in dichloromethane. 相似文献
3.
Joaquim Pérez-Losada Elena Roget Xavier Casamitjana 《Canadian Metallurgical Quarterly》2003,129(9):734-737
High vertical wave-number modes clearly dominate the internal wave field during the stratification period in Boadella reservoir in northeast Spain. In this period, the extraction of hypolimnetic water, due to summer irrigation, brought the surface level down by 6 m in one month and the epilimnetic water progressively occupied the whole water column. The temperature profile, with the exception of a few meters at the surface layer, presented an almost constant temperature gradient of about 0.7°C/m. The period of the main vertical mode is 24 h with an amplitude of around 1 m. Thermistor chain records and meteorological data allow us to deduce that this mode is, at least, a third vertical mode forced by the wind, which normally has a typical periodicity of 24 h. However, when the wind changes direction from south to north, the circulation cells developed due to this forced nonstationary oscillation are destroyed. When this occurs, the Bulk Richardson number is Rib ~ 1. Similar vertical structures as a response to wind forcing should be expected in similar systems, although this has not been reported in the literature. 相似文献
4.
5.
Crystals of mixed NdLa heptamolybdates (max. size0.75×0.75×0.75 mm3) grown by silica gel technique were characterized using EDAX, IR, optical and scanning electron micrscopies.X-ray as well as electrn diffraction. The composition of the crystals was determined as (Nd1/2 La1/2 )2 Mo7O24·35H2O.The crystals exhibit varied morpholgies including square and octagonal platelets, cuboids, multifaceted crystal in coalesced and aggregated forms and spherulites.The XRD results indicate crystallinity of the grown material. Electron diffraction results suggest thermal instability of the material. IR results show the presence of peaks due to water and metal-oxygen bonds 相似文献
6.
Fractal Nature of Crack Growth under Different Temperature 总被引:1,自引:0,他引:1
Qunsheng CAO 《材料科学技术学报》1996,12(2):143-148
We have studied numerically a simple crack growth model in a two-dimensional triangular lattice of bonds and nodes which incorporates the sudece of a growing crack bond-breaking probability Pi~ exp{(-Vi+Ei)φ(T)}, where Ei is elastic eneny stored in the i-th bond. Different energy temperature factors φ(T) are employed during crack formation and propagation process with a uniform dilation strain case and a shear case and with periodic boundary condition in the horizontal direction. Our results show that the patterns of the cracks generated are fractal structure and the effective fractal dimensionalities decrease with the increase of the temperature factor φ(T)(the absolute temperature T decreasing). In the paper we also discuss the relation between the effective fractal dimension Deff (the radius Rg Of gyration) and the fractal dimensions D (the radius R of circular), and also give their modification values Ω about two kinds of methods in the lattice model 相似文献
7.
楼滨乔 《核电子学与探测技术》1993,(4)
本文对最基本的HCMOS器件(反相器和与非门)作了γ辐射损伤实验。通过器件性能变化,分析了γ辐射对电路的作用。 相似文献
8.
Residual electrical resistivity due to short-range order has been calculated for Cu100-xAlx (x=9.13,13.56, 14.5 and 14.76 in at pct) alloys using pseudopotential approach, and the results have been discussed in the light of experimental studies of the local-order structure of these alloys. In case of Cu85.5Al14.5, change in the total residual electrical resistivity due to neutron-irradiation effects has been estimated by including contributions from the short-range order and static atomic displacement correction. Our results show a decrease in the residual resistivity in the irradiated Cu-Al solid solution as compared to the unirradiated sample. This is in accordance with the experimental results 相似文献
9.
10.