全文获取类型
收费全文 | 2321篇 |
免费 | 70篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 20篇 |
综合类 | 3篇 |
化学工业 | 654篇 |
金属工艺 | 35篇 |
机械仪表 | 34篇 |
建筑科学 | 169篇 |
矿业工程 | 62篇 |
能源动力 | 43篇 |
轻工业 | 227篇 |
水利工程 | 54篇 |
石油天然气 | 1篇 |
无线电 | 173篇 |
一般工业技术 | 303篇 |
冶金工业 | 181篇 |
原子能技术 | 17篇 |
自动化技术 | 420篇 |
出版年
2021年 | 24篇 |
2018年 | 25篇 |
2017年 | 22篇 |
2016年 | 61篇 |
2015年 | 54篇 |
2014年 | 76篇 |
2013年 | 88篇 |
2012年 | 135篇 |
2011年 | 122篇 |
2010年 | 81篇 |
2009年 | 87篇 |
2008年 | 94篇 |
2007年 | 94篇 |
2006年 | 135篇 |
2005年 | 59篇 |
2004年 | 47篇 |
2003年 | 51篇 |
2002年 | 54篇 |
2001年 | 30篇 |
2000年 | 42篇 |
1999年 | 43篇 |
1998年 | 38篇 |
1997年 | 34篇 |
1996年 | 30篇 |
1995年 | 25篇 |
1994年 | 39篇 |
1993年 | 37篇 |
1992年 | 28篇 |
1991年 | 34篇 |
1990年 | 36篇 |
1989年 | 29篇 |
1988年 | 24篇 |
1987年 | 23篇 |
1986年 | 24篇 |
1985年 | 28篇 |
1984年 | 35篇 |
1983年 | 23篇 |
1982年 | 34篇 |
1981年 | 36篇 |
1980年 | 23篇 |
1979年 | 32篇 |
1978年 | 25篇 |
1977年 | 27篇 |
1976年 | 31篇 |
1975年 | 30篇 |
1974年 | 32篇 |
1973年 | 21篇 |
1972年 | 21篇 |
1971年 | 20篇 |
1970年 | 28篇 |
排序方式: 共有2396条查询结果,搜索用时 15 毫秒
61.
Based on the solidification theory for metal alloys, a simple recipe for the controlled processing of globular microstructures without external stirring is presented: Firstly, small solidification nuclei must be distributed homogeneously throughout a melt. In New Rheocasting (NRC) these nuclei are formed by forced homogeneous nucleation due to partial quenching of the melt, while in Super Rheocasting (SRC) the nuclei are “second phase particles” in specially designed alloys, which are grown in a controlled fashion in a certain temperature range. Potential alloy compositions for SRC are provided. Secondly, given these melts with small particles in them, globular growth can be assured by utilizing the Gibbs‐Thomson “self healing effect” and slow further cooling to allow diffusion in the melt and to suppress constitutional supercooling. This simple recipe is applicable to various ferrous and non‐ferrous alloys. If an SRC alloy is cooled more rapidly than necessary for globular growth of the primary phase, but is held sufficiently long in the SRC range for dispersoid formation, these dispersoids can act as potent grain refiners and possibly enhance elevated temperature properties. A combination of both processes by using SRC alloys in the NRC equipment may lead to pressure tight castings with low porosity and finer grain structure than can be achieved with NRC on its own, and consequently, better mechanical properties. 相似文献
62.
63.
Helmut Haselmann 《Journal of microscopy》1983,129(1):1-2
Melamine-formaldehyde, a universally used technical aminoplast, can be modified into a water-compatible electron microscopic embedding medium. The complete processing of tissues—from fixation to sectioning—is described in this paper. It produces stable sections showing remarkable ultrastructural detail. 相似文献
64.
For dynamically measuring position in three degrees of freedom laser tracking systems are well known. Up to now no possibility to measure also orientation using the same laser beam has been known. We present a technique to incorporate orientation measurement into a laser tracking system that requires only minor changes in the existing hardware. The method is based on the analysis of an image of the reflected laser beam intensity distribution. In this image the edges of a slightly modified retroreflector represent a function of the orientation of the end-effector holding the retroreflector. It is shown that from this image the orientation can be determined uniquely and in real time.
A laser tracking system including position and orientation measurement constitutes an instrument to accurately determine robot performance as well as to acquire hints on how to improve robot models and control algorithms. 相似文献
65.
The properties of edge-type dislocations are strongly dependent on the temperature at which they have been introduced into the crystal. Dislocations produced at T < 0·6 Tm (Tm melting point) exhibit a richer variety of properties than those introduced at T > 0·6 Tm: in germanium a strong increase of the hole density, in silicon an electron para-magnetic resource (EPR)-signal, showing many fine details, and several peaks in the deep level transient spectroscopy (DLTS)-signal, are only found after low-temperature deformation. The increase in the hole density has been ascribed to point defect clouds, which surround the dislocation, and seem to control their mobility. The clouds are not stable at the deformation temperature. The electrical and optical properties of edge-type dislocations, introduced at T > 0·6 Tm into germanium, can be interpreted in terms of a half-filled one-dimensional band (for T ≥ 50 K), which might be due to dangling bonds in the dislocation core. In silicon the experimental data indicate a similar form of the local energy spectrum at dislocations. 相似文献
66.
67.
68.
Datenschutz und Datensicherheit - DuD - 相似文献
69.
Professional order‐picking in deep cold‐storage depots (i.e., storing, picking, and dispatching of frozen groceries) requires employees to remain working at temperatures of approximately ?24°C for a whole workday. Actually, a well‐regulated organization of working times and breaks has not been established, and no competent knowledge exists as to whether an additional age‐differentiated organization is necessary. To assess the physiological effects while working in deep cold, 30 male subjects (Ss) were classified into two age groups (20‐ to 35‐year‐olds and 40‐ to 65‐year‐olds). In whole workday tests, possible age‐dependent effects on the strain were measured to guarantee the preservation of the subjects' ability to work in the long run. For the objectification of the physiological strain, heart rate and skin surface temperature were registered continuously, and blood pressure and body core temperature were measured and recorded discretely during cold exposures of 80, 100, and 120 min, separated by 20‐min warming‐up breaks. Systematic differences of blood pressure could not be found. The heart rate values indicated a high physiological strain for both younger and older Ss, with work‐related increases above the resting level of 30 bpm and more. Due to increases over time, endurance level sometimes was exceeded. Age‐related differences in skin temperature could not be recorded, but the ability to generate heat deteriorated with advancing age, which is shown by more substantial decreases of body core temperature in the group of 40‐ to 65‐year‐olds taken at the tympanum. Regarding physiological strain brought about by maximum heart rate decreasing with age and declined heat generation, correspondingly adapted workday break regimes have to be provided for older employees to ensure their ability to work in the long run. © 2011 Wiley Periodicals, Inc. 相似文献
70.
Monir Tabatabai Bernd Garska Urs Fischer Norbert Moszner Andreas Utterodt Helmut Ritter 《Polymer International》2012,61(3):407-412
Calix[4]arenes were double alkylated with various alkylhalogenides and the residual OH functions were subsequently dimethacrylated with methacryloyl chloride. The successful synthesis of polymerizable calixarenes was proved using 1H NMR spectroscopy, matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry and differential scanning calorimetry. The polymerization behaviour was confirmed by copolymerization with methacrylic acid methyl ester. Furthermore, the flexural strength, the flexural modulus of elasticity, the exothermic course of the photo‐curing reaction and the polymerization shrinkage of experimental dental filling composites containing the modified calixarenes were evaluated. Copyright © 2012 Society of Chemical Industry 相似文献