全文获取类型
收费全文 | 210410篇 |
免费 | 15584篇 |
国内免费 | 7817篇 |
专业分类
电工技术 | 11277篇 |
技术理论 | 14篇 |
综合类 | 11219篇 |
化学工业 | 36681篇 |
金属工艺 | 10632篇 |
机械仪表 | 12091篇 |
建筑科学 | 16646篇 |
矿业工程 | 4950篇 |
能源动力 | 5997篇 |
轻工业 | 13133篇 |
水利工程 | 3258篇 |
石油天然气 | 11090篇 |
武器工业 | 1347篇 |
无线电 | 25879篇 |
一般工业技术 | 27554篇 |
冶金工业 | 11738篇 |
原子能技术 | 2140篇 |
自动化技术 | 28165篇 |
出版年
2024年 | 887篇 |
2023年 | 3300篇 |
2022年 | 5903篇 |
2021年 | 8056篇 |
2020年 | 5886篇 |
2019年 | 5124篇 |
2018年 | 5550篇 |
2017年 | 6321篇 |
2016年 | 5844篇 |
2015年 | 7402篇 |
2014年 | 9674篇 |
2013年 | 12538篇 |
2012年 | 12486篇 |
2011年 | 14198篇 |
2010年 | 11845篇 |
2009年 | 11718篇 |
2008年 | 11159篇 |
2007年 | 10744篇 |
2006年 | 11079篇 |
2005年 | 9858篇 |
2004年 | 6732篇 |
2003年 | 5921篇 |
2002年 | 5399篇 |
2001年 | 4797篇 |
2000年 | 4932篇 |
1999年 | 5693篇 |
1998年 | 5341篇 |
1997年 | 4407篇 |
1996年 | 4022篇 |
1995年 | 3358篇 |
1994年 | 2815篇 |
1993年 | 2237篇 |
1992年 | 1737篇 |
1991年 | 1303篇 |
1990年 | 1055篇 |
1989年 | 915篇 |
1988年 | 712篇 |
1987年 | 537篇 |
1986年 | 431篇 |
1985年 | 366篇 |
1984年 | 237篇 |
1983年 | 225篇 |
1982年 | 188篇 |
1981年 | 158篇 |
1980年 | 143篇 |
1979年 | 106篇 |
1978年 | 76篇 |
1977年 | 66篇 |
1976年 | 83篇 |
1975年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Novel algorithmic features of multimedia applications and advances in VLSI technologies are driving forces behind the new multimedia signal processors. We propose an architecture platform which could provide high performance and flexibility, and would require less external I/O and memory access. It is comprised of array processors to be used as the hardware accelerator and RISC cores to be used as the basis of the programmable processor. It is a hierarchical and scalable architecture style which facilitates the hardware-software codesign of multimedia signal processing circuits and systems. While some control-intensive functions can be implemented using programmable CPUs, other computation-intensive functions can rely on hardware accelerators.To compile multimedia algorithms, we also present an operation placement and scheduling scheme suitable for the proposed architectural platform. Our scheme addresses data reusability and exploits local communication in order to avoid the memory/communication bandwidth bottleneck, which leads to faster program execution. Our method shows a promising performance: a linear speed-up of 16 times can be achieved for the block-matching motion estimation algorithm and the true motion tracking algorithm, which have formed many multimedia applications (e.g., MPEG-2 and MPEG-4). 相似文献
52.
53.
V. S. -Kh. Kim V. A. Samoilov E. M. Sherysheva Chen Yun 《Chemical and Petroleum Engineering》1993,29(8):355-358
Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 8, pp. 9–11, August, 1993. 相似文献
54.
The adoption of asymmetrical digital subscriber lines (ADSL) technology in conjunction with the broadcast digital subscriber lines (BDSL) proposed in this paper could provide a cost effective solution for the introduction of digital video services in the near term. BDSL provides the same digital broadcast video programs to all subscribers through existing twisted pair telephone loops. In this paper, the basics of telephone loop-based digital subscriber lines are first discussed. Then the potential of BDSL is explored in the twisted pair loop plant near end crosstalk (NEXT), far end crosstalk (FEXT), and white noise environment. The capability of BDSL is examined with different serving areas and transmit power levels. The possibility of using orthogonal quadrature amplitude modulation (QAM) to implement a zero guard-band BDSL system is studied. Computer BDSL performance simulations are then presented. The combination of high-bit-rate digital subscriber lines (HDSL), ADSL, and BDSL can provide telephone subscribers many digital broadband services 相似文献
55.
This paper describes a soft switching active snubber for an IGBT operating in a single switch unity power factor three-phase diode rectifier. The soft switching snubber circuit provides zero-voltage turn-off for the main switch. The high turn-off losses of the IGBT due to current tailing are reduced by zero-voltage switching. This allows the circuit to be operated at very high switching frequencies with regulated DC output voltage, high quality input current and unity input power factor. Simulation and experimental results are included 相似文献
56.
Chen L.R. Benjamin S.D. Smith P.W.E. Sipe J.E. 《Quantum Electronics, IEEE Journal of》1998,34(11):2117-2129
We discuss theoretical and experimental studies on the propagation of ultrashort pulses through fiber Bragg gratings. We also consider several applications in optical communications to be found by combining ultrashort pulses and fiber Bragg gratings: a multiwavelength source for wavelength-division-multiplexed systems and a means for implementing optical code-division multiple access 相似文献
57.
58.
Assaderaghi F. Chen J. Solomon R. Chian T.-Y. Ko P.K. Hu C. 《Electron Device Letters, IEEE》1991,12(10):518-520
It has been found that the subthreshold currents of fully depleted silicon-on-insulator (SOI) MOSFETs show a transient behavior under certain front-gate and back-gate voltage conditions. The cause of this anomaly is explained, and applications for the phenomenon are pointed out. Particularly, a simple way to measure the silicon film thickness is suggested 相似文献
59.
针对双组分等温平行反应体系,分析讨论了以提高催化剂活性和选择性为目标时催化剂活性组分的最优分布形式(为δ-函数分布),并给出了确定这种反应体系的催化剂的最佳活性层位置的计算方法。结果表明:以提高选择性为目标的最佳活性层位置比以提高活性为目标的要更靠近催化剂核心,实用的最优位置应介于二者之间。最后,本文还研究了反应动力学级数、本性选择性以及内扩散模数(Thiele 模数)等因素对最佳活性层位置的影响。 相似文献
60.