全文获取类型
收费全文 | 384469篇 |
免费 | 5291篇 |
国内免费 | 1335篇 |
专业分类
电工技术 | 7634篇 |
综合类 | 509篇 |
化学工业 | 57423篇 |
金属工艺 | 14836篇 |
机械仪表 | 12424篇 |
建筑科学 | 9862篇 |
矿业工程 | 1417篇 |
能源动力 | 9669篇 |
轻工业 | 36667篇 |
水利工程 | 3508篇 |
石油天然气 | 4431篇 |
武器工业 | 72篇 |
无线电 | 50618篇 |
一般工业技术 | 73351篇 |
冶金工业 | 67336篇 |
原子能技术 | 7203篇 |
自动化技术 | 34135篇 |
出版年
2021年 | 2671篇 |
2019年 | 2744篇 |
2018年 | 4351篇 |
2017年 | 4479篇 |
2016年 | 4786篇 |
2015年 | 3224篇 |
2014年 | 5547篇 |
2013年 | 16893篇 |
2012年 | 9166篇 |
2011年 | 12676篇 |
2010年 | 9939篇 |
2009年 | 11289篇 |
2008年 | 12452篇 |
2007年 | 12578篇 |
2006年 | 11344篇 |
2005年 | 10416篇 |
2004年 | 10092篇 |
2003年 | 9812篇 |
2002年 | 9591篇 |
2001年 | 9557篇 |
2000年 | 9115篇 |
1999年 | 9213篇 |
1998年 | 19821篇 |
1997年 | 14602篇 |
1996年 | 11801篇 |
1995年 | 9384篇 |
1994年 | 8489篇 |
1993年 | 8189篇 |
1992年 | 6756篇 |
1991年 | 6354篇 |
1990年 | 6122篇 |
1989年 | 5876篇 |
1988年 | 5597篇 |
1987年 | 4929篇 |
1986年 | 4820篇 |
1985年 | 5703篇 |
1984年 | 5316篇 |
1983年 | 4862篇 |
1982年 | 4567篇 |
1981年 | 4602篇 |
1980年 | 4300篇 |
1979年 | 4179篇 |
1978年 | 3967篇 |
1977年 | 4690篇 |
1976年 | 5803篇 |
1975年 | 3655篇 |
1974年 | 3490篇 |
1973年 | 3523篇 |
1972年 | 2848篇 |
1971年 | 2671篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
971.
K. O. Boltar I. D. Burlakov A. M. Filachev E. A. Klimanov V. P. Ponomarenko V. N. Solyakov V. I. Stafeev 《Optical Memory & Neural Networks》2007,16(4):234-247
The recent researches and technological developments of middle and long wavelength infrared HgCdTe photovoltaic detectors
are presented. Structure, topology, design and performance of HgCdTe photodiodes, silicon readout electronics, Focal Plane
Arrays both staring and time delay and integration types, thermal imagers are discussed. Negative differential conductance,
bistability and high frequency oscillations under background infrared radiation in HgCdTe photodiodes are reported. 相似文献
972.
E. P. Velikhov N. N. Ponomarev-Stepnoi V. G. Volkov G. G. Gorodetskii Yu. A. Zverkov O. P. Ivanov S. M. Koltyshev V. D. Muzrukova S. G. Semenov V. E. Stepanov A. V. Chesnokov A. D. Shisha 《Atomic Energy》2007,102(5):375-381
This article is devoted to work done in 2002–2006 as part of the unified project Reabilitatsiya to rehabilitate radiation
hazardous objects and sections of the radioactively contaminated territory of the Russian Science Center Kurchatov Institute.
The main objects of the rehabilitation work were old storage sites built for radioactive wastes on the territory of the Institute
when military and civilian nuclear technologies were under development. The structural features of the storage sites, including
the volumes and characteristics of the wastes stored, are presented. The salient aspects of the disposal sites, taken into
account during the rehabilitation work, are discussed. The organization of the rehabilitation operations and the sequence
in which they are performed, the special features of the technical design solutions used, the technological methods, and ways
for conducting the work are described.
__________
Translated from Atomnaya énergiya, Vol. 102, No. 5, pp. 300–306, May, 2007. 相似文献
973.
N.W. Alnaser R. Flanagan S.E. Al-Khalifa R. Mumtaz S. El-Masri W.E. Alnaser 《Building and Environment》2007
The Bahrain International Circuit (BIC) is considered as one of the best international racing car track in terms of technical aspects and architectural quality. Two Formula 1 races have been hosted in the Kingdom of Bahrain, in 2004 and 2005, at BIC. The BIC had recently won the award of the best international racing car circuit. 相似文献
974.
A. A. Aliev A. V. Suetina A. V. Elistratov A. D. Davydov A. G. Rakhshtadt 《Metal Science and Heat Treatment》2007,49(1-2):75-77
The effect of tempering temperature on the structure, wear resistance, and corrosive properties of steel 08Kh14AN4MDB is studied.
The results of mechanical and corrosion tests are used for constructing an optimization matrix for determining the optimum
tempering temperature.
__________
Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 29–32, February, 2007. 相似文献
975.
A new torque estimator for switched reluctance motor (SRM) drives based on 2-D rotary regression analysis is presented in this paper. The proposed torque estimator is composed of a bicubic regressive polynomial as a function of rotor position and input current. The regressive coefficients can be computed offline or online from the torque characteristics acquired either experimentally or from numerical computation. Furthermore, a torque estimation method by taking mutual coupling into consideration is proposed. It can be seen that the estimated and experimentally obtained self-coupling and mutual-coupling torque characteristics are in good agreement with each other. In addition, the dynamic torque waveforms with and without the mutual coupling, estimated by the proposed estimator, are found to be virtually the same as those obtained from the bicubic spline interpolation for SRM drives with single-pulse voltage, hysteresis current chopping, as well as with voltage pulse width modulation control. The success of all the case studies being reported is a good validation of the usefulness and accuracy of the proposed real-time torque estimator that, as described in this paper, can be used to quickly estimate the instantaneous output torque of SRM drives. 相似文献
976.
977.
van der Steen J.-L.P.J. Esseni D. Palestri P. Selmi L. Hueting R.J.E. 《Electron Devices, IEEE Transactions on》2007,54(8):1843-1851
This paper investigates the validity of the parabolic effective mass approximation (EMA), which is almost universally used to describe the size and bias-induced quantization in n-MOSFETs. In particular, we compare the EMA results with a full-band quantization approach based on the linear combination of bulk bands (LCBB) and study the most relevant quantities for the modeling of the mobility and of the on-current of the devices, namely, the minima of the 2-D subbands, the transport masses, and the electron density of states. Our study deals with both silicon and germanium n-MOSFETs with different crystal orientations and shows that, in most cases, the validity of the EMA is quite satisfactory. The LCBB approach is then used to calculate the values of the effective masses that help improve the EMA accuracy. There are crystal orientations, however, where the 2-D energy dispersion obtained by the LCBB method exhibits features that are difficult to reproduce with the EMA model. 相似文献
978.
Effects of thermal and mechanical treatments on a titanium-based conversion coating for aluminium alloys 总被引:1,自引:0,他引:1
The influence of mechanical deformation and heating on the protective performance of a chromium-free conversion treatment for aluminium alloys has been assessed by polarisation and AC impedance measurements. Protection is unlikely to be seriously compromised by typical production operations. 相似文献
979.
Arash Sarhangi Fard Navid M. Famili Patrick D. Anderson 《Computers & Chemical Engineering》2008,32(7):1471-1481
The main objective of the present work is to modify the traditional mapping method for the simulation of distributive mixing of multiphase flows in geometries involving moving parts such as, internal mixers or twin-screw extruders without a limitation on their geometrical periodicity. The periodicity condition, limits the results of traditional mapping method to tracking mapping mesh between specific discrete time intervals or distances for that geometry is repeated, hence, result is only for fixed orientation of rotors. Imaginary domain method is introduced to track mapping mesh from one state to the next free of geometrical periodicity limitations. In this work the method is introduced and its applicability and accuracy is discussed in details. A two-dimensional (2D) simulation of mixing of two Newtonian fluids with different viscosities in an intermeshing internal mixer is used as a test case study. In this example the key issues of ability to predict mixing state in details for all orientations of rotors is presented. To reduce diffusion errors of mapping method in the boundaries of the rotors, mapping mesh refinement technique that relies upon one single reference mesh is also presented. 相似文献
980.
D. M. Suckling R. W. Peck L. M. Manning L. D. Stringer J. Cappadonna A. M. El-Sayed 《Journal of chemical ecology》2008,34(12):1602-1609
Disruption of Argentine ant trail following and reduced ability to forage (measured by bait location success) was achieved
after presentation of an oversupply of trail pheromone, (Z)-9-hexadecenal. Experiments tested single pheromone point sources and dispersion of a formulation in small field plots. Ant
walking behavior was recorded and digitized by using video tracking, before and after presentation of trail pheromone. Ants
showed changes in three parameters within seconds of treatment: (1) Ants on trails normally showed a unimodal frequency distribution
of walking track angles, but this pattern disappeared after presentation of the trail pheromone; (2) ants showed initial high
trail integrity on a range of untreated substrates from painted walls to wooden or concrete floors, but this was significantly
reduced following presentation of a point source of pheromone; (3) the number of ants in the pheromone-treated area increased
over time, as recruitment apparently exceeded departures. To test trail disruption in small outdoor plots, the trail pheromone
was formulated with carnuba wax-coated quartz laboratory sand (1 g quartz sand/0.2 g wax/1 mg pheromone). The pheromone formulation,
with a half-life of 30 h, was applied by rotary spreader at four rates (0, 2.5, 7.5, and 25 mg pheromone/m2) to 1- and 4-m2 plots in Volcanoes National Park, Hawaii. Ant counts at bait cards in treated plots were significantly reduced compared to
controls on the day of treatment, and there was a significant reduction in ant foraging for 2 days. These results show that
trail pheromone disruption of Argentine ants is possible, but a much more durable formulation is needed before nest-level
impacts can be expected.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献