全文获取类型
收费全文 | 514474篇 |
免费 | 7947篇 |
国内免费 | 1785篇 |
专业分类
电工技术 | 9840篇 |
综合类 | 526篇 |
化学工业 | 78360篇 |
金属工艺 | 17976篇 |
机械仪表 | 15065篇 |
建筑科学 | 14792篇 |
矿业工程 | 1173篇 |
能源动力 | 13704篇 |
轻工业 | 54744篇 |
水利工程 | 4054篇 |
石油天然气 | 2269篇 |
武器工业 | 17篇 |
无线电 | 67982篇 |
一般工业技术 | 95056篇 |
冶金工业 | 93328篇 |
原子能技术 | 7028篇 |
自动化技术 | 48292篇 |
出版年
2021年 | 3188篇 |
2019年 | 3034篇 |
2018年 | 4559篇 |
2017年 | 4649篇 |
2016年 | 4995篇 |
2015年 | 4132篇 |
2014年 | 6909篇 |
2013年 | 23851篇 |
2012年 | 12211篇 |
2011年 | 17672篇 |
2010年 | 13641篇 |
2009年 | 15636篇 |
2008年 | 16901篇 |
2007年 | 17350篇 |
2006年 | 15566篇 |
2005年 | 14554篇 |
2004年 | 14139篇 |
2003年 | 13807篇 |
2002年 | 13428篇 |
2001年 | 13631篇 |
2000年 | 12613篇 |
1999年 | 13150篇 |
1998年 | 28776篇 |
1997年 | 21298篇 |
1996年 | 16977篇 |
1995年 | 13448篇 |
1994年 | 12039篇 |
1993年 | 11488篇 |
1992年 | 8956篇 |
1991年 | 8502篇 |
1990年 | 8114篇 |
1989年 | 7860篇 |
1988年 | 7501篇 |
1987年 | 6414篇 |
1986年 | 6318篇 |
1985年 | 7712篇 |
1984年 | 7143篇 |
1983年 | 6368篇 |
1982年 | 5995篇 |
1981年 | 5877篇 |
1980年 | 5512篇 |
1979年 | 5394篇 |
1978年 | 5024篇 |
1977年 | 6117篇 |
1976年 | 8043篇 |
1975年 | 4259篇 |
1974年 | 4033篇 |
1973年 | 3941篇 |
1972年 | 3176篇 |
1971年 | 2792篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
941.
The state of the art of debugging is examined. A debugged process model that serves as the basis of a general debugging framework is described. The relationship of the model to traditional debugging processes and support tools is discussed. A minimal set of requirements for a general debugging framework is described in terms of both the theory behind debugging methodologies and the support tools. An execution monitor, Eden, that serves as a debugging tool within this general framework is described 相似文献
942.
The dynamical systems theory developed by Zufiria [1], Zufiria and Guttalu [2, 3], and Guttalu and Zufiria [4] is applied to the stability analysis of control systems in which the feedback control law requires in real time the solution of a set of nonlinear algebraic equations. Since a small sampling period is assumed, the stability and performance of the controlled process can be studied with a continuous-time formulation. A singularly perturbed system is used to model both the dynamics of the system being controlled and a numerical iterative algorithm required to compute the control law. An updating control procedure has been proposed based on the iterative nature of the control algorithm. The results obtained by Zufiria [1] regarding the behavior of a dynamical system that models the numerical algorithms lead to a considerable simplification in the analysis. For the case of a control problem involving inverse kinematics, the numerical algorithm that solves for inverse kinematics can be considered as an observer (or an estimator) of the state-space variables. The study provides an estimate of the required speed of computations to preserve the stability of the controller.Recommended by E .P. Ryan 相似文献
943.
The structure and ac properties of ZrO2 thin film capacitors were studied as a function of deposition temperature. Zirconia films deposited on molybdenum electrodes were polycrystalline. The monoclinic phase was the major phase detected in the films deposited at temperatures between 300—600 °C. At lower deposition temperatures (190–200 °C), the cubic phase was the major crystalline phase formed. A major (111̄) and a minor (111) fiber axis were observed for the monoclinic phase. Average crystallite size increased from 118 to 484 Å for the (111̄) and 175 to 265 Å for the (111) crystallites as deposition temperature increased from 200 to 600 °C. Ac conduction in Mo-ZrO2-Mo structures at fields < 0.05 MV/cm was dominated by electron hop with a frequency independent loss behavior between 25 and 150 °C. Between 150 and 325 °C, a σd ∝ fy dependence was observed where y depended on measurement and deposition temperatures. The remanence of interfacial polarization was suggested as an additional loss mechanism in this temperature range and for frequencies of 60-105 Hz. 相似文献
944.
J.A. Bakken L. Barone D. Braun M. Caillat C. Dionisi C. Dor H. Elmamouni F. Ferroni G.L. Grazer J.T. He R. Herbiet B. Ille P. Lecomte E. Longo P.F. Loverre Y.S. Lu J.P. Martin U. Micke R.P. Mount P.A. Pirou H.-G. Sander D. Schmitz M. Schneegans D.P. Stickland R.L. Sumner K.L. Tung E. Valente M. Vivargent 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1985,228(2-3):294-302
A calorimeter of 25 bismuth germanate (BGO) crystals equipped with silicon photodiode readout has been tested at the CERN SPS in the energy range 1–50 GeV. The response for electrons has been shown to be linear in this energy range and the rms resolution obtained (
) is approximately 1%, for E > 4 GeV. The electron/pion separation was found to be better than 1:500 in the energy range 1–20 GeV. Data on lateral and longitudinal shower development were compared with the results of a Monte Carlo simulation using the SLAC-EGS program and found to be in good agreement. 相似文献
945.
Billardon M. Elleaume P. Ortega J. Bazin C. Bergher M. Velghe M. Deacon D. Petroff Y. 《Quantum Electronics, IEEE Journal of》1985,21(7):805-823
In this paper we review the results obtained in the last two years with the Orsay free electron laser. 相似文献
946.
J. M. Parpia W. P. Kirk P. S. Kobiela Z. Olejniczak 《Journal of Low Temperature Physics》1985,60(1-2):57-72
The ac susceptibility of lanthanum-diluted cerium magnesium nitrate has been compared to the temperature scales as derived
from the (P, T) relation determined by Halperin and that was measured recently by Greywall. It is found that the susceptibility does
not obey a simple Curie-Weiss law over the temperature range between 1 and 50 mK. The results of these calibrations are also
used to determine the temperatures for the second-order phase transitions into the superfluid phases of3He at several pressures. TheseT
c(P) values are compared to results of earlier experiments that used thermometry based on the susceptibility of platinum as well
as other thermometry techniques. 相似文献
947.
W. S. Walston I. M. Bernstein A. W. Thompson 《Metallurgical and Materials Transactions A》1991,22(6):1443-1451
The microstructure of a single-crystal nickel-base superalloy, PWA 1480, has been varied by heat treatment and hot isostatic
pressing in order to study the role of the γ/yγ′ eutectic and porosity on subsequent tensile behavior. The level of porosity
was found not to affect any of the tensile properties, while the γ/γ′ eutectic strongly influenced ductility. Eliminating
the γ/γ′ eutectic increased ductility which was attributed to the cleavage fracture of this constituent. It is proposed that
such cleavage of the γ/γ′ eutectic is initiated by the stress created from impinging slip bands, promoting shear localization,
and final fracture along {111} slip planes. The precise nature of this fracture process is discussed with emphasis on the
role of the γ/′ micro-structure. The deformation structure of PWA 1480 was also studied, and while different in some respects
from many other single-crystal superalloys, its fracture process appears to be similar.
Formerly Graduate Student, Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University. 相似文献
948.
949.
In this paper we suggest a new statistical method of correcting the results of hot-line experiments for the effects of background sources and we use the new method to reassess the adequacy of three probability distributions proposed in the literature for image spread from line sources. The data are from sources labelled with 125I in semi-thin resin sections 0·4-0·8 μm in thickness. The new method reveals that two of the models describe the empirical distributions more closely than earlier analysis had suggested, and it confirms an increasing relationship between half distance of image spread and the thickness of the source. However, it also confirms that considerable ‘inter hot-line’ experimental variation remains, even after background correction. This suggests that multiple experiments are needed to produce reliable estimates of half distance. 相似文献
950.
The Highway Loss Data Institute (HLDI) compiles injury and collision claim information from major insurance companies. These data have indicated that a disproportionately large number of injury claims are made for small cars. As a result, it might be concluded that small cars increase injury risk to their occupants. Recent advertisements by a major automobile manufacturer suggest a similar conclusion should be drawn from these data. In this paper it is shown that the apparent higher injury risk attributed to small cars can reflect the behavior of persons driving small cars. The number of injury claim accidents per collision claim accident is examined as an alternative measure of injury risk. Possible problems in interpretation are discussed. 相似文献