全文获取类型
收费全文 | 10223篇 |
免费 | 416篇 |
国内免费 | 51篇 |
专业分类
电工技术 | 189篇 |
综合类 | 33篇 |
化学工业 | 1333篇 |
金属工艺 | 176篇 |
机械仪表 | 273篇 |
建筑科学 | 633篇 |
矿业工程 | 17篇 |
能源动力 | 280篇 |
轻工业 | 654篇 |
水利工程 | 68篇 |
石油天然气 | 40篇 |
武器工业 | 3篇 |
无线电 | 1767篇 |
一般工业技术 | 1676篇 |
冶金工业 | 1504篇 |
原子能技术 | 53篇 |
自动化技术 | 1991篇 |
出版年
2023年 | 54篇 |
2022年 | 108篇 |
2021年 | 157篇 |
2020年 | 110篇 |
2019年 | 140篇 |
2018年 | 208篇 |
2017年 | 200篇 |
2016年 | 242篇 |
2015年 | 207篇 |
2014年 | 246篇 |
2013年 | 601篇 |
2012年 | 534篇 |
2011年 | 602篇 |
2010年 | 458篇 |
2009年 | 492篇 |
2008年 | 587篇 |
2007年 | 537篇 |
2006年 | 514篇 |
2005年 | 412篇 |
2004年 | 320篇 |
2003年 | 330篇 |
2002年 | 282篇 |
2001年 | 246篇 |
2000年 | 243篇 |
1999年 | 254篇 |
1998年 | 521篇 |
1997年 | 323篇 |
1996年 | 254篇 |
1995年 | 218篇 |
1994年 | 139篇 |
1993年 | 146篇 |
1992年 | 107篇 |
1991年 | 80篇 |
1990年 | 69篇 |
1989年 | 67篇 |
1988年 | 62篇 |
1987年 | 58篇 |
1986年 | 51篇 |
1985年 | 76篇 |
1984年 | 47篇 |
1983年 | 31篇 |
1982年 | 49篇 |
1981年 | 42篇 |
1980年 | 35篇 |
1979年 | 38篇 |
1978年 | 25篇 |
1977年 | 24篇 |
1976年 | 48篇 |
1975年 | 21篇 |
1973年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Optical scattering in beef steak to predict tenderness using hyperspectral imaging in the VIS-NIR region 总被引:1,自引:0,他引:1
Kim Cluff Govindarajan Konda Naganathan Jeyamkondan Subbiah Renfu Lu Chris R. Calkins Ashok Samal 《Sensing and Instrumentation for Food Quality and Safety》2008,2(3):189-196
The objective of this research is to develop a non-destructive method for predicting cooked beef tenderness using optical
scattering of light on fresh beef muscle tissue. A hyperspectral imaging system (λ = 496–1,036 nm) that consists of a CCD
camera and an imaging spectrograph, was used to acquire beef steak images. The hyperspectral image consisted of 120 bands
with spectral intervals of 4.54 nm. Sixty-one fresh beef steaks, including 44 strip loin and 17 tenderloin cuts, were collected.
After imaging, the steaks were cooked and Warner-Bratzler shear (WBS) force values were collected as tenderness references.
The optical scattering profiles were derived from the hyperspectral images and fitted to the modified Lorentzian function.
Parameters, such as the peak height, full scattering width at half maximum (FWHM), and the slope around the FWHM were determined
at each wavelength. Stepwise regression was used to identify 7 key wavelengths and parameters. The parameters were then used
to predict the WBS scores. The model was able to predict WBS scores with an R = 0.67. Optical scattering implemented with hyperspectral imaging shows limited success for predicting current status of tenderness
in beef steak. 相似文献
102.
日益精密且成本逐渐下降的的显示技术使人们对下一代户内、户外广告的"数字化"充满了期待。然而运行显示网络必不可少的"大脑"是不容忽略的。下面综述了成功的数字广告系统的软件需求,以及这些系统的工作方式。 相似文献
103.
Environmentally responsive hydrogels have become attractive research subjects for many applications. In this work, a series of pH‐sensitive and color‐changing nanoparticles (nanogels) with core–shell structures were synthesized. The cores were blue latex particles synthesized by a miniemulsion technique with styrene and methacrylic acid as monomers and Neozapon Blue 807 as a dye. The shell was a pH‐sensitive polymer that was precipitation‐polymerized onto the core from 2‐(diethylamino) ethyl methacrylate with N,N′‐methylenebisacrylamide, poly(propylene glycol) diacrylate, and divinylbenzene as crosslinking agents. In the resultant latexes, the color was observed to change from deep blue to pale blue as the pH of the system was changed from a high of 10 to a low of 3. The synthesized latexes and particles (gels) were then characterized with an ultraviolet–visible spectrometer, dynamic light scattering, Fourier transform infrared, and nuclear magnetic resonance. Atomic force microscopy was also used to investigate the different morphologies of the particles after the synthesized latexes were dried at different pH values. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
104.
105.
Yong Chen Xiaofeng Liao Kwok-Wo Wong 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2006,53(7):527-529
An encryption system with discretized skew tent map has been proposed recently by N. Masuda . However, there is a fundamental weakness with this chaotic cryptographic scheme. In this paper, a chosen plaintext attack requiring only two plaintexts is proposed. An improved version of this attack that narrows the key space need to be searched is also suggested. The test results demonstrate that this encryption cryptosystem is easily broken under the proposed chosen plaintext attack. 相似文献
106.
Thailand has recently introduced net metering legislation that provides streamlined procedures for small renewable energy generators to connect to the grid, and guarantees both a market and good prices. The new laws create income opportunities for rural communities based on locally produced, clean, renewable energy supplies and offer significant potential to reduce Thailand's dependence on imported oil and coal. Chris Greacen, Chuenchom Sangarasri Greacen and Rich Plevin report. 相似文献
107.
A new colour quantisation and quadtree based image compression scheme is proposed. The features of the new scheme are that colour palette ordering and requantisation of the decoded image for palette-based monitor displays are not required. Thus, fast decoding and displaying can be achieved 相似文献
108.
Haus H.A. Khatri F.I. Wong W.S. Ippen E.P. Tamura K.R. 《Quantum Electronics, IEEE Journal of》1996,32(6):917-924
The interaction of a soliton of the Nonlinear Schrodinger Equation (NSE) with a weak sinusoidal wave packet is treated analytically. The second-order soliton solution containing the original soliton and a perturbing soliton is expanded to first order in the amplitude of the perturbating soliton. From this expansion, one obtains the associate function of Gordon (1992) and a continuous change of position and phase of the perturbed soliton. One finds that the soliton experiences a second-order change of velocity under the influence of the perturbation. This result is then used to derive the displacement due to a wave packet of general shape, which is also confirmed by computer simulation 相似文献
109.
110.
The tail-flick (TF) technique was used to assess the antinociceptive properties of nifedipine (NIF) given intraperitoneally (i.p.). First, the most suitable intensity of the noxious stimulus (temperature of the bulb) has been ascertained and used in the main study. Male Sprague-Dawley rats received NIF, dissolved in dimethyl sulfoxide (DMSO) at the doses of 0.0, 0.5, 2, 5, 10 and 15 mg/kg, or control with no injection. For the main study, the noxious stimulus was limited to 15 sec (cut-off time) and TF latencies were recorded up to 120 min. The antinociceptive response was expressed as the area under the curve for each rat and analyzed by one-way ANOVA. The antinociceptive response to the lower doses of NIF (0.5 and 2 mg/kg) did not differ from control (no injection) and DMSO alone. Significance was found at 5, 10 and 15 mg NIF with no difference among the doses. However, there was an increasing tendency of the mean values from 0.5 to 15 mg NIF resulting in a positive correlation. The correlation coefficient was 0.32483 (p = 0.015) and regression equation Y = (19.37) x dose + 1320. Our data suggest that spinal mechanisms are involved in NIF-induced antinociception. 相似文献