全文获取类型
收费全文 | 1563201篇 |
免费 | 26324篇 |
国内免费 | 7029篇 |
专业分类
电工技术 | 34612篇 |
综合类 | 6456篇 |
化学工业 | 274107篇 |
金属工艺 | 64980篇 |
机械仪表 | 44187篇 |
建筑科学 | 47350篇 |
矿业工程 | 11557篇 |
能源动力 | 50400篇 |
轻工业 | 119869篇 |
水利工程 | 15726篇 |
石油天然气 | 37837篇 |
武器工业 | 150篇 |
无线电 | 198043篇 |
一般工业技术 | 292165篇 |
冶金工业 | 193431篇 |
原子能技术 | 34234篇 |
自动化技术 | 171450篇 |
出版年
2021年 | 15611篇 |
2020年 | 11969篇 |
2019年 | 14709篇 |
2018年 | 17169篇 |
2017年 | 16492篇 |
2016年 | 22064篇 |
2015年 | 17554篇 |
2014年 | 28790篇 |
2013年 | 88093篇 |
2012年 | 37066篇 |
2011年 | 50652篇 |
2010年 | 43936篇 |
2009年 | 51846篇 |
2008年 | 46923篇 |
2007年 | 44306篇 |
2006年 | 45877篇 |
2005年 | 40878篇 |
2004年 | 42781篇 |
2003年 | 42527篇 |
2002年 | 41360篇 |
2001年 | 38522篇 |
2000年 | 36729篇 |
1999年 | 36378篇 |
1998年 | 54837篇 |
1997年 | 45160篇 |
1996年 | 39060篇 |
1995年 | 32876篇 |
1994年 | 30510篇 |
1993年 | 30466篇 |
1992年 | 26682篇 |
1991年 | 23775篇 |
1990年 | 24072篇 |
1989年 | 23159篇 |
1988年 | 21651篇 |
1987年 | 19920篇 |
1986年 | 19234篇 |
1985年 | 22545篇 |
1984年 | 22508篇 |
1983年 | 20456篇 |
1982年 | 19442篇 |
1981年 | 19612篇 |
1980年 | 18202篇 |
1979年 | 18621篇 |
1978年 | 17908篇 |
1977年 | 18074篇 |
1976年 | 19713篇 |
1975年 | 16070篇 |
1974年 | 15543篇 |
1973年 | 15659篇 |
1972年 | 13122篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
831.
1 引言石磨水洗牛仔布的成本是非常高的 ,但由于客户喜欢陈旧、磨损的外观 ,所以这种高成本又是十分必要的。那么 ,如何将这么高的成本降下来呢 ?通常的做法是把工厂转移到劳动力低廉的发展中国家。如果有着悠久历史的纺织品公司因为劳动力成本较高而不再具有竞争力 ,他们将不得不寻找另外一种可替代石磨水洗而同样能获得满意外观的方法。这是一种似乎对于我们具有实际意义的想法 ,它似乎具有逻辑性又很合理 ,但是这可能吗 ?当然 ,这种方法必须工艺简单 ,保证附加成本较低 ;必须可连续生产 ,以保证产量较高 ;必须可在常规设备上采用现有工… 相似文献
832.
833.
Parameterisation of slant-Haar transforms 总被引:1,自引:0,他引:1
Agaian S. Tourshan K. Noonan J.P. 《Vision, Image and Signal Processing, IEE Proceedings -》2003,150(5):11
A parameterisation of the slant-Haar transform is presented, which includes an existing version of the slant-Haar transform. An efficient algorithm for the slant-Haar transform is developed and its computational complexity is estimated. The parametric slant-Haar transforms are compared to the Karhunen-Loeve transform. The parametric slant-Haar is shown to perform better than the commonly used slant-Haar and slant-Hadamard transforms for the first-order Markov model and also performs better than the discrete cosine transform for images approximated by the generalised image correlation model 相似文献
834.
835.
Codecasa L. D'Amore D. Maffezzoni P. Batty W. 《Components and Packaging Technologies, IEEE Transactions on》2004,27(1):87-95
In this paper, the multipoint moment matching method for model order reduction of discretized linear thermal networks is extended to distributed linear thermal networks. As a result, from the analytical canonical forms of distributed linear thermal networks, reduced thermal networks are derived analytically. This direct construction of the reduced network, from the exact analytical solutions, avoids the inevitable inaccuracies inherent in conventional surface and volume meshing. It allows nearly exact reduced thermal network construction by domain decomposition for arbitrarily complicated structures. 相似文献
836.
837.
Lepikhin P. P. Romashchenko V. A. Tarasovskaya S. A. Korbach V. G. 《Strength of Materials》2003,35(1):52-59
The exactness and stability of the Wilkins method in the investigation of the stress-strain state of axisymmetric anisotropic elastic shells, including thick-walled ones, have been studied for different values of artificial viscosity, pulse load rise and fall time, and different deformation process durations. A comparison of numerical calculations, performed by means of an application software package developed by V. A. Romashchenko on the basis of the Wilkins method, with experimental results, known numerical data, and with calculations using the computation kernel LS-DYNA 3D has been carried out. 相似文献
838.
Navid Ehsan Mingyan Liu Roderick J. Ragland 《International Journal of Communication Systems》2003,16(6):513-534
Performance enhancing proxies (PEPs) are widely used to improve the performance of TCP over high delay‐bandwidth product links and links with high error probability. In this paper we analyse the performance of using TCP connection splitting in combination with web caching via traces obtained from a commercial satellite system. We examine the resulting performance gain under different scenarios, including the effect of caching, congestion, random loss and file sizes. We show, via analysing our measurements, that the performance gain from using splitting is highly sensitive to random losses and the number of simultaneous connections, and that such sensitivity is alleviated by caching. On the other hand, the use of a splitting proxy enhances the value of web caching in that cache hits result in much more significant performance improvement over cache misses when TCP splitting is used. We also compare the performance of using different versions of HTTP in such a system. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
839.
P.D. Dragic 《Photonics Technology Letters, IEEE》2004,16(8):1822-1824
We present a narrow linewidth, injection-seeded Q-switched Er fiber ring oscillator, that provides over 600 /spl mu/W of average output power at 500 Hz, with 1.2 /spl mu/J per pulse, before the output appears to be significantly affected by stimulated Brillouin scattering. This laser configuration provides multiple advantages in LIDAR systems because it offers the possibility of broad and rapid tunability. 相似文献
840.
J. B. Quinn G. E. Schumacher L. W. Schultheis 《Journal of Failure Analysis and Prevention》2004,4(1):41-46
Several days after heart surgery, a patient discovered his upper right canine tooth had broken at the root. Such tooth damage,
recognized post-operatively, is usually assumed to be caused by blunt mechanical force from an instrument used by the anesthesiologist
during placement of a breathing tube at the start of surgery.
In this case, the patient had saved the crown portion of the broken tooth, and it was possible to examine the root fracture
characteristics. The curvature and direction of the crack path and natural tooth situation suggested that failure could be
described through a cantilever beam model. This was confirmed when a whole extracted sample tooth was embedded and broken
by a measured force in a manner consistent with the model. The resulting fracture surface matched that of the patient’s broken
canine tooth. However, the high load and force direction necessary to fracture the root was inconsistent with forces applied
during the anesthesia procedure. The failure analysis and further investigation indicated tooth clenching on the breathing
tube during recovery was the likely cause of fracture.
This paper presents an alternate explanation for intubation-related dental injury, demonstrates the practicality of fractographic
analysis of biological materials, and introduces a methodology for simulating in vitro tooth settings for mechanical testing. 相似文献