全文获取类型
收费全文 | 880610篇 |
免费 | 12681篇 |
国内免费 | 2569篇 |
专业分类
电工技术 | 16083篇 |
综合类 | 805篇 |
化学工业 | 132748篇 |
金属工艺 | 33856篇 |
机械仪表 | 25735篇 |
建筑科学 | 21987篇 |
矿业工程 | 4253篇 |
能源动力 | 23930篇 |
轻工业 | 76699篇 |
水利工程 | 8764篇 |
石油天然气 | 15537篇 |
武器工业 | 53篇 |
无线电 | 101945篇 |
一般工业技术 | 171613篇 |
冶金工业 | 170060篇 |
原子能技术 | 18008篇 |
自动化技术 | 73784篇 |
出版年
2021年 | 7602篇 |
2020年 | 5708篇 |
2019年 | 7030篇 |
2018年 | 12088篇 |
2017年 | 11886篇 |
2016年 | 12650篇 |
2015年 | 8663篇 |
2014年 | 14377篇 |
2013年 | 40268篇 |
2012年 | 22687篇 |
2011年 | 31392篇 |
2010年 | 25169篇 |
2009年 | 28322篇 |
2008年 | 29091篇 |
2007年 | 28554篇 |
2006年 | 25201篇 |
2005年 | 22864篇 |
2004年 | 21913篇 |
2003年 | 21662篇 |
2002年 | 20820篇 |
2001年 | 21049篇 |
2000年 | 19633篇 |
1999年 | 20648篇 |
1998年 | 52320篇 |
1997年 | 37209篇 |
1996年 | 28706篇 |
1995年 | 21617篇 |
1994年 | 19028篇 |
1993年 | 18764篇 |
1992年 | 13663篇 |
1991年 | 13063篇 |
1990年 | 12730篇 |
1989年 | 12413篇 |
1988年 | 11817篇 |
1987年 | 10372篇 |
1986年 | 10247篇 |
1985年 | 11500篇 |
1984年 | 10742篇 |
1983年 | 9867篇 |
1982年 | 9206篇 |
1981年 | 9326篇 |
1980年 | 8940篇 |
1979年 | 8609篇 |
1978年 | 8378篇 |
1977年 | 10061篇 |
1976年 | 13356篇 |
1975年 | 7347篇 |
1974年 | 6953篇 |
1973年 | 6968篇 |
1972年 | 5911篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
911.
Ana M. García José M. Villora Diego A. Moreno Carlos Ranninger Pío Callejas M. Flora Barba 《Journal of the American Ceramic Society》2003,86(12):2200-2202
The objective of this research was to study the removal of cadmium and lead from an aqueous solution through a biological treatment. For this purpose a glass-ceramic material was manufactured from industrial and urban wastes. Biofilms of microorganisms found in wastewater were developed on its surface, and continuous tests were conducted in the presence and absence of the biofilm to analyze the glass-ceramic's ability to remove the heavy metals from an aqueous environment. The results suggest that this bioremediation process, developed on an industrial scale, could represent an alternative to the chemical processes currently used. 相似文献
912.
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
913.
914.
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
915.
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
916.
A model for vibrations of a beam with a slider is derived, analysed and numerically simulated. It describes a viscoelastic beam that is clamped at one end to a vibrating device, while the other end moves between two stops attached to a slider. The contact is described by the normal compliance or by the Signorini conditions. The existence of weak solutions is established using the theory of set-valued pseudomonotone operators. The model is discretized using fourth-order spatial discretization, the solutions are numerically simulated and their results presented. The dynamics of the vibrations are depicted and so are the noise characteristics of the system. 相似文献
917.
Mathematical models of thermomechanical processes which are based on the laws of rational thermodynamics of irreversible processes are treated. Singular features of the unsteady-state behavior of a continuous medium are demonstrated within different models, such as a medium with internal parameters of state, a medium with memory, and a medium of the velocity type. 相似文献
918.
Meghelli M. Rylyakov A.V. Zier S.J. Sorna M. Friedman D. 《Solid-State Circuits, IEEE Journal of》2003,38(12):2147-2154
A 43-Gb/s receiver (Rx) and transmitter (Tx) chip set for SONET OC-768 transmission systems is reported. Both ICs are implemented in a 0.18-/spl mu/m SiGe BiCMOS technology featuring 120-GHz f/sub T/ and 100 GHz f/sub max/. The Rx includes a limiting amplifier, a half-rate clock and data recovery unit, a 1:4 demultiplexer, a frequency acquisition aid, and a frequency lock detector. Input sensitivity for a bit-error rate less than 10/sup -9/ is 40 mV and jitter generation better than 230 fs rms. The IC dissipates 2.4 W from a -3.6-V supply voltage. The Tx integrates a half-rate clock multiplier unit with a 4:1 multiplexer. Measured clock jitter generation is better than 170 fs rms. The IC consumes 2.3 W from a -3.6-V supply voltage. 相似文献
919.
M. Riad Manaa Laurence E. Fried Evan J. Reed 《Journal of Computer-Aided Materials Design》2003,10(2):75-97
In this article, we review recent atomistic computational techniques to study the electronic structure aspects and chemistry
of energetic materials at high-pressure and/or high temperature. While several mechanisms have been proposed for the initial
events of energetic materials at high-pressure, we explore the validity of a proposed shear-induced local metallization via
molecular bond bending in the insensitive explosive TATB. We study the effect of high-stress (both uniform and uniaxial) on
the electronic energy band-gap and the first chemical event of a prototypical energetic material, that of nitromethane. We
also determine chemical reactions rate laws and decomposition mechanisms from a quantum-based molecular dynamics simulation
of HMX, a widely used explosive material, at conditions of high density and temperature similar to that encounter under detonation.
Finally, we review a new multi-scale computational tool recently developed to model the shock-induced chemistry of energetic
materials at the atomistic level, and report its applicability to shocked solid nitromethane.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
920.
Separation tests using hollow-fibre modules were performed for the difficult selective extraction of trivalent actinides over fission lanthanides from acidic media. This article shows that with 2,6-di(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine as the extractant, up to 94% americium could be extracted from 1.0 kmol/m3 HNO3, with minimal lanthanide co-extraction. Using a synergistic mixture of bis(chlorophenyl)dithiophosphinic acid and tri-n-octyl phosphine oxide, tests were performed on extraction, lanthanide scrubbing and stripping. In the extraction test, up to 99.99% americium could be extracted from 0.5 kmol/m3 HNO3, with approximately one third of the lanthanides being co-extracted. Mass transfer calculations using a consistent set of input data showed good agreement with the experiments. 相似文献