全文获取类型
收费全文 | 2631篇 |
免费 | 127篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 32篇 |
综合类 | 11篇 |
化学工业 | 370篇 |
金属工艺 | 141篇 |
机械仪表 | 122篇 |
建筑科学 | 110篇 |
矿业工程 | 12篇 |
能源动力 | 57篇 |
轻工业 | 265篇 |
水利工程 | 11篇 |
石油天然气 | 10篇 |
无线电 | 325篇 |
一般工业技术 | 413篇 |
冶金工业 | 381篇 |
原子能技术 | 13篇 |
自动化技术 | 489篇 |
出版年
2023年 | 17篇 |
2022年 | 30篇 |
2021年 | 64篇 |
2020年 | 33篇 |
2019年 | 53篇 |
2018年 | 63篇 |
2017年 | 66篇 |
2016年 | 88篇 |
2015年 | 59篇 |
2014年 | 87篇 |
2013年 | 178篇 |
2012年 | 110篇 |
2011年 | 146篇 |
2010年 | 114篇 |
2009年 | 148篇 |
2008年 | 135篇 |
2007年 | 122篇 |
2006年 | 131篇 |
2005年 | 131篇 |
2004年 | 95篇 |
2003年 | 95篇 |
2002年 | 83篇 |
2001年 | 45篇 |
2000年 | 37篇 |
1999年 | 48篇 |
1998年 | 100篇 |
1997年 | 71篇 |
1996年 | 68篇 |
1995年 | 52篇 |
1994年 | 28篇 |
1993年 | 46篇 |
1992年 | 21篇 |
1991年 | 16篇 |
1990年 | 17篇 |
1989年 | 17篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 17篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 7篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 15篇 |
1975年 | 6篇 |
1973年 | 5篇 |
1972年 | 4篇 |
排序方式: 共有2762条查询结果,搜索用时 15 毫秒
1.
Shin Hansub Sim Sungyong Kwon Hyukyoon Hwang Sangheum Lee Younho 《International Journal of Information Security》2022,21(1):25-36
International Journal of Information Security - This paper deals with a well-known problem in the area of the smudge attacks: when a user draws a pattern to unlock the pattern lock on a smartphone... 相似文献
2.
Karim Gharbi Louise Matthews James Bron Ron Roberts Alan Tinch Michael Stear 《Journal of the Royal Society Interface》2015,12(110)
Sea lice threaten the welfare of farmed Atlantic salmon and the sustainability of fish farming across the world. Chemical treatments are the major method of control but drug resistance means that alternatives are urgently needed. Selective breeding can be a cheap and effective alternative. Here, we combine experimental trials and diagnostics to provide a practical protocol for quantifying resistance to sea lice. We then combined quantitative genetics with epidemiological modelling to make the first prediction of the response to selection, quantified in terms of reduced need for chemical treatments. We infected over 1400 young fish with Lepeophtheirus salmonis, the most important species in the Northern Hemisphere. Mechanisms of resistance were expressed early in infection. Consequently, the number of lice per fish and the ranking of families were very similar at 7 and 17 days post infection, providing a stable window for assessing susceptibility to infection. The heritability of lice numbers within this time window was moderately high at 0.3, confirming that selective breeding is viable. We combined an epidemiological model of sea lice infection and control on a salmon farm with genetic variation in susceptibility among individuals. We simulated 10 generations of selective breeding and examined the frequency of treatments needed to control infection. Our model predicted that substantially fewer chemical treatments are needed to control lice outbreaks in selected populations and chemical treatment could be unnecessary after 10 generations of selection. Selective breeding for sea lice resistance should reduce the impact of sea lice on fish health and thus substantially improve the sustainability of Atlantic salmon production. 相似文献
3.
The design of a microstrip‐fed annular‐ring slot antenna (ARSA) with circular polarization (CP) radiation is initially studied. To obtain CP radiation with broad 3‐dB axial ratio (AR) bandwidth that can cover the WiMAX 2.3 GHz (2305–2320 MHz, 2345–2360 MHz) and WLAN 2.4 GHz (2400–2480 MHz) bands, a novel technique of extending an inverted L‐shaped slot from the bottom section of the annular‐ring is proposed. To suppress the harmonic modes induced by the CP ARSA, the technique of integrating a defected ground structure into the annular‐ring slot is further introduced. From the measured results, 10‐dB impedance bandwidth and 3‐dB AR bandwidth of 44.86 and 9.68% were achieved by the proposed harmonic suppressed CP ARSA. Furthermore, average gain and radiation efficiency of ~4.7 dBic and 71%, respectively, were also exhibited across the bands of interest. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:337–345, 2015. 相似文献
4.
Ron Wilson 《电子设计技术》2006,13(11):126-126
无线USB的前途似乎无与伦比——它能消除那些把大家桌面弄得像鼠窝一样小小的不怎么灵便的电缆。但事实上,只有需要大量的外设时无线USB设备才有优势,而且它必须非常微型而廉价,否则带来的麻烦远多于缠绕的电缆。因此,插在PC USB端口作为无线基站的硬件锁就必须有尽可能高的集成度。但一片芯片中要包含USB有线接口、控制器、无线基带和RF电路,技术上还无法实现。下面我们将看到一家供应商Wisalr的一种可量产参考设计,它是如何接近于解决这个问题的。 相似文献
5.
6.
Ron Kimmel Doron Shaked Michael Elad Irwin Sobel 《IEEE transactions on image processing》2005,14(6):796-803
Gamut mapping deals with the need to adjust a color image to fit into the constrained color gamut of a given rendering medium. A typical use for this tool is the reproduction of a color image prior to its printing, such that it exploits best the given printer/medium color gamut, namely the colors the printer can produce on the given medium. Most of the classical gamut mapping methods involve a pixel-by-pixel mapping and ignore the spatial color configuration. Recently proposed spatial-dependent approaches for gamut mapping are either based on heuristic assumptions or involve a high computational cost. In this paper, we present a new variational approach for space-dependent gamut mapping. Our treatment starts with the presentation of a new measure for the problem, closely related to a recent measure proposed for Retinex. We also link our method to recent measures that attempt to couple spectral and spatial perceptual measures. It is shown that the gamut mapping problem leads to a quadratic programming formulation, guaranteed to have a unique solution if the gamut of the target device is convex. An efficient numerical solution is proposed with promising results. 相似文献
7.
Ron Mancini 《电子设计技术》2005,12(12):76-76
输出电压相对于电压参考的短期变化即为噪声。参考电压噪声一般发生在以下两个频段:短期噪声在0.1Hz~10Hz,宽带噪声在10Hz~1kHz。由于噪声电压一般与参考电压成正比,故常用每百万分之一(ppm)来表示噪声,并借此使每百万分之一值恒定。能隙(或带隙)电压参考具有介于3ppm~16ppm之间的噪声电压,但埋入式齐纳电压参考的噪声更低,介于0.1ppm~0.5ppm之间。噪声随参考电流的增加而减小,但增加参考电流并不是大多数电压参考的选项。 相似文献
8.
Chadwin D. Young Gennadi Bersuker Yuegang Zhao Jeff J. Peterson Joel Barnett George A. Brown Jang H. Sim Rino Choi Byoung Hun Lee Peter Zeitzoff 《Microelectronics Reliability》2005,45(5-6):806
Effects of constant voltage stress (CVS) on gate stacks consisting of an ALD HfO2 dielectric with various interfacial layers were studied with time dependent sensing measurements: DC I–V, pulse I–V, and charge pumping (CP) at different frequencies. The process of injected electron trapping/de-trapping on pre-existing defects in the bulk of the high-κ film was found to constitute the major contribution to the time dependence of the threshold voltage (Vt) shift during stress. The trap generation observed with the low frequency CP measurements is suggested to occur within the interfacial oxide layer or the interfacial layer/high-κ interface, with only a minor effect on Vt. 相似文献
9.
Forward displacement solutions are presented for a class of spatial parallel manipulators. In particular, considered are manipulators consisting of a platform supported through passive spherical joints by three branches, each branch having three-revolute joints forming its main arm. Solutions are described for arbitrary main-arm layouts and for all possible cases of redundant (nine, eight, and seven sensors) and non-redundant (six sensors) sensing of branch main-arm joint displacements. It is demonstrated that closed-form forward displacement solutions can be found for all cases of redundant sensing. Furthermore, it is shown that a closed-form solution can be obtained for one of the two possible cases of non-redundant sensing of the main-arm joint displacements. The only case of joint displacement sensing not allowing a closed-form forward displacement solution is two joints sensed per branch, a case that can be expressed as a 16th-order polynomial of a single variable. Due to the importance of having efficient and failure-safe solutions for the forward displacement problem, it is suggested that appropriate redundancy in displacement sensing should be an important consideration in the design of parallel manipulation devices. © 1994 John Wiley & Sons, Inc. 相似文献
10.
T Bakács Z Végh AH Merry RB Sim L Varga Z Kertész G Tusnády E Klein 《Canadian Metallurgical Quarterly》1993,35(3):219-228
The lysis of group AB erythrocytes by human complement was studied by different anti-A and anti-B IgM monoclonal antibodies (mabs) in a 51Cr-release assay. The concentration of membrane-bound immunoglobulin was detected by ELISA, and the amount of C1q and C3 bound to sensitized red cells was measured by using purified, 125I-labelled molecules. We have demonstrated that there is an exponential relationship between the concentration of the sensitizing IgM mabs and C1q binding to the sensitized AB cell. The efficiency of binding was related to the number of antibodies bound; thus, anti-A sensitized cells bound 3-6 times more C1q than anti-B sensitized cells did. AB cells, on the other hand, bound similar amounts of C3 whether anti-A or anti-B was present. The lytic efficiencies of the various IgM mabs during short incubation times were different, suggesting that the complement activation rates vary widely with different antibodies on the AB cell membrane. The binding of C1q to an antibody-sensitized target activates a cascade, whose components may migrate away from the sensitizing antibody; interactions between the activation processes generated by the anti-A and anti-B antibodies may thus occur. Choosing appropriate pairs of anti-A and anti-B mabs for the simultaneous sensitization of AB cells has indeed resulted in stimulation in some and inhibition in other combinations of mabs. It is suggested that stimulation is observed when the activated intermediates are produced in excess, whereas inhibition occurs when a shortage of activated intermediates prevents mutual utilization. 相似文献