全文获取类型
收费全文 | 24713篇 |
免费 | 2594篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 1482篇 |
综合类 | 874篇 |
化学工业 | 10601篇 |
金属工艺 | 430篇 |
机械仪表 | 538篇 |
建筑科学 | 1087篇 |
矿业工程 | 206篇 |
能源动力 | 258篇 |
轻工业 | 2194篇 |
水利工程 | 172篇 |
石油天然气 | 77篇 |
武器工业 | 1篇 |
无线电 | 842篇 |
一般工业技术 | 4543篇 |
冶金工业 | 604篇 |
原子能技术 | 74篇 |
自动化技术 | 3336篇 |
出版年
2023年 | 759篇 |
2022年 | 478篇 |
2021年 | 947篇 |
2020年 | 865篇 |
2019年 | 741篇 |
2018年 | 779篇 |
2017年 | 566篇 |
2016年 | 884篇 |
2015年 | 1056篇 |
2014年 | 1133篇 |
2013年 | 1871篇 |
2012年 | 951篇 |
2011年 | 889篇 |
2010年 | 1195篇 |
2009年 | 1295篇 |
2008年 | 771篇 |
2007年 | 714篇 |
2006年 | 516篇 |
2005年 | 503篇 |
2004年 | 490篇 |
2003年 | 433篇 |
2002年 | 377篇 |
2001年 | 251篇 |
1999年 | 188篇 |
1998年 | 342篇 |
1997年 | 222篇 |
1996年 | 290篇 |
1995年 | 274篇 |
1994年 | 221篇 |
1993年 | 285篇 |
1992年 | 212篇 |
1991年 | 174篇 |
1990年 | 198篇 |
1989年 | 222篇 |
1988年 | 173篇 |
1987年 | 208篇 |
1986年 | 220篇 |
1985年 | 190篇 |
1984年 | 218篇 |
1983年 | 209篇 |
1982年 | 187篇 |
1981年 | 236篇 |
1980年 | 188篇 |
1979年 | 186篇 |
1977年 | 176篇 |
1976年 | 188篇 |
1975年 | 232篇 |
1974年 | 210篇 |
1973年 | 383篇 |
1972年 | 229篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Christilin D. M. Annie Brighty Mary Dr M. Safish 《Multimedia Tools and Applications》2021,80(13):19441-19457
Multimedia Tools and Applications - While denoising 3D MRI, structural preservation is a very critical process in the medical region. However, Rician noise in MRI has affected the image quality... 相似文献
102.
Corrosion of oil-fired domestic boilers Depending on the surface temperature of the flue gas side the corrosion of oil fired domestic boilers proceeds either mainly by acid corrosion or by oxygen corrosion:
- – At surface temperatures of 60°C and higher the corrosion mechanism of acid corrosion prevails and the corrosion rates amount to 0.1–0.3 mm/year (values referred to continuous burner operation). The corrosion products consist of soluble iron(II)- and iron(III)sulfates. Higher corrosion rates can be attributed to an appreciable catalytic formation of sulfur trioxide on the corrosion products formed on the convective heating surfaces.
- – At surface temperatures of 40°C the mechanism of oxygen corrosion already dominates and the corrosion rates are about ten times higher (1.5–3 mm/year, referred to continous burner operation). The high portion of ioron oxide hydrates, especially goethit (α-FeOOH), makes the corrosion products difficult to remove.
- – Distinctly reduced service lives are also expected for the so called reduced temperature boilers (“Niedertemperaturkessel”) and low temperature boiers (“Tieftemperaturkessel”): According to the manufacturers these boilers may be operated at boiler water temperatures well below 60°C, as they are equipped with constructive measures to enhance the surface temperature on the flue gas side. However, these measures are only fully effective under stationary conditions.
103.
A novel stylus based profiling instrument has been developed for rapid measurement of small surface areas. Outlined in the following paper are some of the key features of the prototype system including the wideband stylus pick-up and the dedicated scanning traverse mechanism. In addition, some preliminary results obtained by scanning the instrument over several different surfaces are presented. 相似文献
104.
Stefan Luidold Helmut Antrekowitsch Robert Ressel 《International Journal of Refractory Metals and Hard Materials》2007,25(5-6):423-432
In the last years, a variety of processes respectively process steps have been investigated for the production of niobium powder. This is due to the fact that niobium capacitors could be a viable alternative to tantalum capacitors from a performance, availability, and price point of view. The reduction of niobium pentoxide by magnesium results in fine powders with high specific surface area but has the disadvantages of a very exothermic nature and the formation of magnesium niobate. It is shown in this work that the application of a continuously operating cyclone reactor and the use of niobium(IV) oxide as raw material solve these problems. A good control of the highly exothermic reaction within the cyclone reactor was achieved in the cyclone reactor by the ratio between gas flow rate and powder flow rate as well as by a proper preheating of the gas. 相似文献
105.
On finite dynamic equations for fluid-saturated porous media 总被引:2,自引:0,他引:2
Summary The paper concerns the relations between two principally different approaches to the formulation of momentum balance equations in porous media theories, namely, the dynamic approach similar to Biot's theory and the modern approach as a result of mixture theories extended by the concept of volume fractions. In particular, it is shown that both approaches necessarily lead to the same type of momentum balance equations and furthermore contain, in a certain sense, within the geometrically linear case, the well-known classical equations of Biot's theory. 相似文献
106.
Prof. Dr. rer. nat. G. Lehner 《Electrical Engineering (Archiv fur Elektrotechnik)》1995,78(4):209-217
Contents We discuss some initial and boundary value problems of one-dimensional electromagnetic field diffusion. The solutions can be given by infinite series in two essentially different (however equivalent) forms, one being the usual Fourier-expansion and the other one being an infinite series of Gaussian exponentials or related functions (as for instance error-functions). The second form can be obtained by using infinitely many images to fulfill initial and boundary conditions. Finally the mathematical relations between the two equivalent types of solutions are discussed in terms of -functions and their transformation properties. The existence of the solutions in these two different forms is very interesting from a numerical point of view also.
Die Diffusion elektromagnetischer Felder, -Funktionen und Spiegelungsmethoden
Übersicht Es werden einige Anfangs- und Randwertprobleme eindimensionaler elektromagnetischer Felddiffusion erörtert. Die Lösungen können in zwei wesentlich verschiedenen (jedoch gleichwertigen) Formen angegeben werden, erstens in Form üblicher Fourier-Reihen und zweitens in Form unendlicher Reihen von Gaußschen Exponentialfunktionen oder damit verwandter Funktionen (z.B. Fehlerfunktionen). Diese zweite Form der Lösungen läßt sich durch die Anwendung unendlich oft wiederholter Spiegelung zur Erfüllung der Rand- und Anfangsbedingung anschaulich interpretieren. Abschließend werden die beiden Lösungstypen mit Hilfe von -Funktionen und deren Transformationseigenschaften erläutert. Die Verfügbarkeit der Lösungen in beiden Formen ist auch numerisch sehr interessant.相似文献
107.
In this paper, an Automated Brain Image Analysis (ABIA) system that classifies the Magnetic Resonance Imaging (MRI) of human brain is presented. The classification of MRI images into normal or low grade or high grade plays a vital role for the early diagnosis. The Non-Subsampled Shearlet Transform (NSST) that captures more visual information than conventional wavelet transforms is employed for feature extraction. As the feature space of NSST is very high, a statistical t-test is applied to select the dominant directional sub-bands at each level of NSST decomposition based on sub-band energies. A combination of features that includes Gray Level Co-occurrence Matrix (GLCM) based features, Histograms of Positive Shearlet Coefficients (HPSC), and Histograms of Negative Shearlet Coefficients (HNSC) are estimated. The combined feature set is utilized in the classification phase where a hybrid approach is designed with three classifiers; k-Nearest Neighbor (kNN), Naive Bayes (NB) and Support Vector Machine (SVM) classifiers. The output of individual trained classifiers for a testing input is hybridized to take a final decision. The quantitative results of ABIA system on Repository of Molecular Brain Neoplasia Data (REMBRANDT) database show the overall improved performance in comparison with a single classifier model with accuracy of 99% for normal/abnormal classification and 98% for low and high risk classification. 相似文献
108.
Dr. Z. Zemánek 《Acta Mechanica》1996,115(1-4):151-159
Summary The use of holographic interferometry for the measurement of large deformations is described. From the nature of holographic interferometry it is evident that large deformations exceed the wave length of the light source used by at least ten times of this size. To obtain holographically identifiable values of large deformations, a method of successive partial lighting is used. It shows how it is possible to keep all the advantages of the holographic method and use it even under conditions which apparently exceed its possibilities of application. 相似文献
109.
Dr.-Ing. Gerd Holbach 《Computer aided design》2010,42(11):953-955
110.
Prof. Dr. Jarke 《WIRTSCHAFTSINFORMATIK》2009,51(1):154-155
Ohne Zusammenfassung
This article is also available in English via http://www.springerlink.com and http://www.bise-journal.org: BISE – Call for
Papers, Issue 3/2010, High-Impact Requirements Engineering. Bus Inf Syst Eng. doi: . 相似文献