全文获取类型
收费全文 | 5456篇 |
免费 | 199篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 70篇 |
综合类 | 27篇 |
化学工业 | 1243篇 |
金属工艺 | 179篇 |
机械仪表 | 115篇 |
建筑科学 | 298篇 |
矿业工程 | 4篇 |
能源动力 | 113篇 |
轻工业 | 392篇 |
水利工程 | 13篇 |
石油天然气 | 10篇 |
无线电 | 422篇 |
一般工业技术 | 988篇 |
冶金工业 | 1098篇 |
原子能技术 | 96篇 |
自动化技术 | 589篇 |
出版年
2021年 | 68篇 |
2020年 | 41篇 |
2019年 | 79篇 |
2018年 | 86篇 |
2017年 | 71篇 |
2016年 | 106篇 |
2015年 | 93篇 |
2014年 | 131篇 |
2013年 | 222篇 |
2012年 | 198篇 |
2011年 | 230篇 |
2010年 | 187篇 |
2009年 | 179篇 |
2008年 | 192篇 |
2007年 | 196篇 |
2006年 | 180篇 |
2005年 | 148篇 |
2004年 | 162篇 |
2003年 | 127篇 |
2002年 | 135篇 |
2001年 | 112篇 |
2000年 | 143篇 |
1999年 | 159篇 |
1998年 | 276篇 |
1997年 | 189篇 |
1996年 | 170篇 |
1995年 | 109篇 |
1994年 | 97篇 |
1993年 | 91篇 |
1992年 | 69篇 |
1991年 | 78篇 |
1990年 | 67篇 |
1989年 | 84篇 |
1988年 | 61篇 |
1987年 | 74篇 |
1986年 | 42篇 |
1985年 | 43篇 |
1984年 | 47篇 |
1983年 | 57篇 |
1982年 | 46篇 |
1981年 | 38篇 |
1980年 | 55篇 |
1979年 | 47篇 |
1978年 | 56篇 |
1977年 | 67篇 |
1976年 | 93篇 |
1975年 | 42篇 |
1974年 | 53篇 |
1973年 | 51篇 |
1970年 | 34篇 |
排序方式: 共有5657条查询结果,搜索用时 15 毫秒
41.
Dieter Ullmann 《NTM》2006,14(1):1-8
A lot of publications on the acoustics of theatres and churches were published around the turn of the 18th to the 19th century.The
authors were architects who were interested in acoustical problems. Chladni was the first physicist who published on the acoustics
of rooms, he introduced the term “reverberation” into this field. His publications on this subject are reviewed. They have
been the basis for the great progress of room acoustics since 1900.
Zum 250. Geburtstag des Gelehrten 相似文献
Zum 250. Geburtstag des Gelehrten 相似文献
42.
Slab casting for hot rolled steel and strip casting using the twin roll casting (TRC) method are compared in terms of inclusions evolution. There are differences of the processes, mainly the use of casting flux in CC of slabs, or pool shapes and sizes in terms of TRC, particularly when roll diameters vary. The inclusion evolution of alumina in a low carbon steel grade was estimated. By modelling particle growth rate, coagulation and deposition, an ‘agglomeration index’ was created to describe the probability of clogging in the SEN. Similarly the growth of secondary alumina precipitation during cooling of the melt in the pool by Stokes collision and turbulent collision was estimated in terms of forming large particles which are able to float‐up. Influences of melt superheat or caster size were taken into account. 相似文献
43.
Reinhold Kleiner Dieter Koelle John Clarke 《Journal of Low Temperature Physics》2007,149(5-6):230-260
We investigate the characteristics and noise performance of rf Superconducting Quantum Interference Devices (SQUIDs) by solving
the corresponding Langevin equations numerically and optimizing the model parameters with respect to noise energy. After introducing
the basic concepts of the numerical simulations, we give a detailed discussion of the performance of the SQUID as a function
of all relevant parameters. The best performance is obtained in the crossover region between the dispersive and dissipative
regimes, characterized by an inductance parameter β′
L
≡2π
LI
0/Φ
0≈1; L is the loop inductance, I
0 the critical current of the Josephson junction, and Φ
0 the flux quantum. In this regime, the lowest (intrinsic) values of noise energy are a factor of about 2 above previous estimates
based on analytical approaches. However, several other analytical predictions, such as the inverse proportionality of the
noise energy on the tank circuit quality factor and the square of the coupling coefficient between the tank circuit and the
SQUID loop, could not be well reproduced. The optimized intrinsic noise energy of the rf SQUID is superior to that of the
dc SQUID at all temperatures. Although for technologically achievable parameters this advantage shrinks, particularly at low
thermal fluctuation levels, we give examples for realistic parameters that lead to a noise energy comparable to that of the
dc SQUID even in this regime.
相似文献
44.
Multiresolution is currently one of the main schemes used in CAD modeling for representing objects, particularly when large-scale geometric data must be transferred interactively over a network, as in the case of collaborative design. Increasingly complex products and growing competition have turned design into a collaborative team effort. Furthermore, the widespread development of Internet viewers has also necessitated the transfer and display of large-scale CAD models over networks. In order to reduce the volume of transferred data, efforts have been made to transfer CSG (Constructive Solid Geometry) models rather than those based on B_rep (Boundary Representation). This paper presents an original new method for speeding up data transfer by using multiresolution CSG models at different levels of details (LOD). The multiresolution CSG algorithm generates a hierarchy of multiresolution CSG trees; at each level, the shape is further approximated and represented by a smaller number of CSG primitives. The paper analyzes the proposed algorithm, and demonstrates its feasibility. 相似文献
45.
Alexander Babich Konstantinos Mavrommatis Dieter Senk Heinrich Wilhelm Gudenau 《国际钢铁研究》2004,75(7):428-432
This contribution deals with advanced educational technologies needed to equip customers from higher education institutions, research and industry with efficient tools supporting their work and operating new skills‐training methods. The challenges are reducing the training costs, improving quality and increasing the number of graduates in engineering departments. The concept of a Virtual Lab based on the combination of various teaching methods and tools is presented. Principles of mathematisation in metallurgical education and training are discussed. An example of online course designed in the form of Virtual Lab is demonstrated. 相似文献
46.
Exposure to turbulence, an environmental stimulus, produces behavioral adaptation in the Aplysia siphon-withdrawal response (SWR). The authors show that the duration and spatial extent of turbulence influence adaptation recovery. In terms of duration, recovery in whole animals and reduced preparations (tail, siphon, and CNS) was more rapid after longer exposures to turbulence (10 min) than after briefer exposures (10 s-5 min). In terms of spatial extent, recovery in reduced preparations was more rapid after diffuse turbulence (tail and siphon together) compared with focal turbulence (siphon alone). Furthermore, spatial extent and duration interact: Duration regulates recovery only when turbulence is diffuse. Results suggest that SWR adaptation reflects a composite of cellular processes, including short-term synaptic enhancement in L30 inhibitory interneurons. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
47.
SS Burkhart SP Fischer WM Nottage JC Esch FA Barber D Doctor J Ferrier 《Canadian Metallurgical Quarterly》1996,12(6):704-708
The primary purpose of this investigation was to compare tissue fixation security by simple sutures versus mattress sutures in transosseous rotator cuff repair. These two repair techniques were each performed in 17 human cadaver shoulders, with two bone tunnels being used for the repair by two simple sutures and two other bone tunnels being used for the repair by one mattress suture. The repairs were loaded to failure in a servohydraulic materials test system. Rotator cuff repair by simple sutures was found to be significantly stronger than repair by mattress sutures (P = .0007). The average ultimate load to failure for the simple suture construct (189.62 N) was 39.72% greater than that for the mattress suture construct (135.71 N). Most of the failures occurred by suture breakage at the knot. Load-sharing by multiple suture tails and multiple knots in the simple suture configuration likely contributed to its superior strength characteristics compared with the mattress suture configuration. 相似文献
48.
49.
B. Gerharz A. Du Chesne G. Lieser E. W. Fischer W. Z. Cai 《Journal of Materials Science》1996,31(4):1053-1063
The microphase structure of a series of poly (styrene-b-methylphenylsiloxane) (PS-b-PMPS)-diblock copolymers with various compositions and molecular weights has been studied by small-angle X-ray scattering, electron spectroscopic imaging and solid-state nuclear magnetic resonance spectroscopy. This diblock copolymer system is miscible within a distinct range of temperature and molecular weight exhibiting an upper critical solution temperature. The three chosen methods which complement each other can be applied to the chemically unmodified model system. The results of the various measurements correlate to describe the microphase structure, the domain size and the interphase. 相似文献
50.
Chunsheng Lu Robert Danzer Franz Dieter Fischer 《Journal of the American Ceramic Society》2002,85(6):1640-1642
The influence of threshold stress on the estimation of the Weibull statistics is discussed in terms of the Akaike information criterion. Numerical simulations show that, if sample data are limited in number and threshold stress is not too large, the two-parameter Weibull distribution is still a preferred choice. For example, the fit of strength data of glass and ceramics to the two- and three-parameter Weibull distributions is compared. 相似文献