全文获取类型
收费全文 | 272926篇 |
免费 | 3541篇 |
国内免费 | 292篇 |
专业分类
电工技术 | 4181篇 |
综合类 | 102篇 |
化学工业 | 45458篇 |
金属工艺 | 15505篇 |
机械仪表 | 10586篇 |
建筑科学 | 4930篇 |
矿业工程 | 3807篇 |
能源动力 | 4342篇 |
轻工业 | 14708篇 |
水利工程 | 4371篇 |
石油天然气 | 13102篇 |
武器工业 | 29篇 |
无线电 | 21135篇 |
一般工业技术 | 66593篇 |
冶金工业 | 36941篇 |
原子能技术 | 11185篇 |
自动化技术 | 19784篇 |
出版年
2021年 | 3440篇 |
2020年 | 2784篇 |
2019年 | 3354篇 |
2018年 | 6553篇 |
2017年 | 6819篇 |
2016年 | 7183篇 |
2015年 | 3917篇 |
2014年 | 6338篇 |
2013年 | 12159篇 |
2012年 | 8924篇 |
2011年 | 10362篇 |
2010年 | 8469篇 |
2009年 | 9087篇 |
2008年 | 9223篇 |
2007年 | 8826篇 |
2006年 | 6971篇 |
2005年 | 6080篇 |
2004年 | 5966篇 |
2003年 | 5764篇 |
2002年 | 5524篇 |
2001年 | 5233篇 |
2000年 | 5171篇 |
1999年 | 4524篇 |
1998年 | 8891篇 |
1997年 | 6890篇 |
1996年 | 5072篇 |
1995年 | 4005篇 |
1994年 | 3693篇 |
1993年 | 3904篇 |
1992年 | 3290篇 |
1991年 | 3424篇 |
1990年 | 3535篇 |
1989年 | 3422篇 |
1988年 | 3343篇 |
1987年 | 3324篇 |
1986年 | 3210篇 |
1985年 | 3373篇 |
1984年 | 3312篇 |
1983年 | 3179篇 |
1982年 | 3022篇 |
1981年 | 3095篇 |
1980年 | 3123篇 |
1979年 | 3280篇 |
1978年 | 3514篇 |
1977年 | 3541篇 |
1976年 | 4078篇 |
1975年 | 3241篇 |
1974年 | 3316篇 |
1973年 | 3375篇 |
1972年 | 2989篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Koch B. Hidayat A. Hongbin Zhang Mirvoda V. Lichtinger M. Sandel D. Noe R. 《Photonics Technology Letters, IEEE》2008,20(12):961-963
We demonstrate endless polarization stabilization with a control speed of up to 9 krad/s, over random Poincare sphere trajectories. These are in total >35 Mrad long, are composed in particular of difficult-to-track circles with all radii and orientations, and thereby include all possible worst cases. The maximum polarization mismatch and relative intensity errors are 0.13 rad and 0.43%, respectively. The controller runs on a field-programmable gate array and uses a commercial multistage LiNbO3 polarization transformer as the control device. 相似文献
992.
993.
The Problem of Estimation of Importance Factors as a Symmetric-Lexicographic Problem of Optimization
V. V. Podinovskii 《Automation and Remote Control》2003,64(3):480-492
It is shown that the problem of calculating the importance factors of objects on the basis of their interval paired comparisons, which is set up as a multicriteria problem of the minimization of equally important criteria that manifest themselves as multiplicative residuals of the system of inequalities for the required factors, comes to the sequence of a few problems of linear programming. 相似文献
994.
Carballo V.M.B. Chefdeville M. Fransen M. van der Graaf H. Melai J. Salm C. Schmitz J. Timmermans J. 《Electron Device Letters, IEEE》2008,29(6):585-587
An unpackaged microchip is used as the sensing element in a miniaturized gaseous proportional chamber. This letter reports on the fabrication and performance of a complete radiation imaging detector based on this principle. Our fabrication schemes are based on wafer-scale and chip-scale postprocessing. Compared to hybrid-assembled gaseous detectors, our microsystem shows superior alignment precision and energy resolution, and offers the capability to unambiguously reconstruct 3D radiation tracks on the spot. 相似文献
995.
Interpretation of scatterometer ocean surface wind vector EOFs over the Northwestern Pacific 总被引:1,自引:0,他引:1
Jiayi Pan Xiao-Hai Yan Quanan ZhengW.Timothy Liu Victor V Klemas 《Remote sensing of environment》2003,84(1):53-68
Satellite scatterometer winds over the northwestern Pacific were analyzed with the vector empirical orthogonal function (VEOF) method. The Hilbert-Huang transform (HHT), a newly developed non-linear and non-stationary time series data processing method, was also employed in the analysis. A combination of European Remote Sensing Satellite (ERS) −1/2 scatterometer, NASA Scatterometer (NSCAT) and NASA's Quick Scatterometer (QuikSCAT) winds covering the period from January 1992 to April 2000 and the area of 0-50°N, 100-148°E constitutes the baseline for this study. The results indicate that annual cycles dominate the two leading VEOF modes. The first VEOF shows the East Asian monsoon features and the second represents a spring-autumn oscillation. We removed the annual signal from the data set and calculated the interannual VEOFs. The first interannual VEOF represents the interannual variability existing in the spring-autumn oscillation. The temporal mode is correlated with the Southern Oscillation Index (SOI), but has a half-year lag with respect to the SOI. The spatial mode of the first interannual VEOF reflects the response of the tropical and extratropical winds to ENSO events. The second interannual VEOF is another ENSO related mode, and the temporal VEOF mode is correlated with the SOI with a correlation coefficient of 0.78, revealing the wind variability over mid-latitudes, which is associated with ENSO events. Further analysis indicated that the wind variability over the coast of East Asia represents anomalies of a Hadley cell. The quasi-biennial oscillation (QBO) was found in the temporal mode, indicating and verifying that the QBO in the wind fields is related to ENSO events. The third VEOF shows the interannaul variability in the winter-summer mode and displays the interannual variability of the East Asian monsoon. The three leading interannual VEOFs are statistically meaningful as confirmed by a significance test. 相似文献
996.
Er. V. Kal’yanov 《Technical Physics Letters》2007,33(12):1015-1017
A mathematical model of a new controllable autooscilatory chaotic system based on inductively coupled Chua’s oscillators is described. Numerical simulations show that, using a chaotizing feedback algorithm, chaotic oscillations in this system can be excited in regimes where only regular oscillations are generated otherwise. 相似文献
997.
A. M. Skorobogatov A. V. Tvardovskii 《Journal of Engineering Physics and Thermophysics》2007,80(3):634-637
A model for calculating of the change in the basic thermodynamic characteristics of a sorbent (internal energy and entropy)
with the phenomenological-thermodynamics method has been developed. Calculations for the systems polycarbonate-carbon dioxide
and polymethylmethacrylate-carbon dioxide have been carried out.
__________
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 3, pp. 198–200, May–June, 2007. 相似文献
998.
A. D. Bulanov P. G. Sennikov V. A. Krylov T. G. Sorochkina L. A. Chuprov O. Yu. Chernova O. Yu. Troshin 《Inorganic Materials》2007,43(4):364-368
Using gas chromatography and high-resolution Fourier-transform IR spectroscopy, we have determined the concentrations of C1–C4 hydrocarbon impurities in isotopically unmodified silicon tetrafluoride before and after fine purification and in 28Si-enriched SiF4. The concentrations of C1–C4 hydrocarbon impurities in silicon tetrafluoride for SiH4 synthesis have been shown to correlate with those in the synthesized silane. 相似文献
999.
D. L. Kuznetsov E. V. Kol’man Yu. S. Surkov V. V. Uvarin I. E. Filatov 《Technical Physics Letters》2007,33(7):604-606
The process of methane conversion in a mixture modeling the natural gas under the action of a periodic nanosecond pulsed electron beam and an electron-beam-induced non-self-sustained discharge has been numerically simulated and studied in experiment. The possibility of methane conversion under the action of electric pulses without significant heating of the processed gas mixture is demonstrated for the first time. The main conversion products in experiment were hydrogen, ethylene, and acetylene. 相似文献
1000.
The paper deals with a new finite element scheme for non-destructive eddy-current testing (ECT) problems involving multiply connected test pieces and differential probes. It concerns a perturbation technique applied to the magnetodynamic h-phi formulation. The unperturbed field (in the absence of the flaw) is conventionally computed in the complete domain. The source of the perturbation problem is then determined by the projection of the unperturbed field in a relatively small region around the defect, the optimum size of which depends on the working frequency. The discretisation of this reduced domain is well adapted to the size of the defect and chosen independently of the dimensions of the excitation probe and the specimen under study. At a discrete level, the voltage change is efficiently computed by integration only over the defect and a layer of elements in the reduced domain that touches the defect's boundary. The accuracy of the proposed perturbation model is illustrated by comparison of the results obtained for different dimensions of the reduced domain with those achieved in the conventional way. The considered test case involves a differential probe scanning the outer surface of a metal tube for the detection of through-wall cracks 相似文献