全文获取类型
收费全文 | 9188篇 |
免费 | 507篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 128篇 |
综合类 | 52篇 |
化学工业 | 2271篇 |
金属工艺 | 241篇 |
机械仪表 | 212篇 |
建筑科学 | 618篇 |
矿业工程 | 28篇 |
能源动力 | 301篇 |
轻工业 | 893篇 |
水利工程 | 88篇 |
石油天然气 | 72篇 |
武器工业 | 1篇 |
无线电 | 690篇 |
一般工业技术 | 1554篇 |
冶金工业 | 610篇 |
原子能技术 | 83篇 |
自动化技术 | 1873篇 |
出版年
2023年 | 79篇 |
2022年 | 119篇 |
2021年 | 362篇 |
2020年 | 197篇 |
2019年 | 219篇 |
2018年 | 301篇 |
2017年 | 248篇 |
2016年 | 332篇 |
2015年 | 253篇 |
2014年 | 362篇 |
2013年 | 663篇 |
2012年 | 506篇 |
2011年 | 655篇 |
2010年 | 452篇 |
2009年 | 512篇 |
2008年 | 475篇 |
2007年 | 432篇 |
2006年 | 358篇 |
2005年 | 309篇 |
2004年 | 284篇 |
2003年 | 273篇 |
2002年 | 198篇 |
2001年 | 141篇 |
2000年 | 145篇 |
1999年 | 121篇 |
1998年 | 138篇 |
1997年 | 148篇 |
1996年 | 114篇 |
1995年 | 92篇 |
1994年 | 83篇 |
1993年 | 93篇 |
1992年 | 62篇 |
1991年 | 62篇 |
1990年 | 64篇 |
1989年 | 71篇 |
1988年 | 49篇 |
1987年 | 48篇 |
1986年 | 51篇 |
1985年 | 54篇 |
1984年 | 64篇 |
1983年 | 48篇 |
1982年 | 41篇 |
1981年 | 42篇 |
1980年 | 41篇 |
1979年 | 33篇 |
1978年 | 35篇 |
1977年 | 36篇 |
1976年 | 48篇 |
1975年 | 41篇 |
1973年 | 37篇 |
排序方式: 共有9715条查询结果,搜索用时 15 毫秒
71.
Fluorescence microscopy techniques have become important tools in mitosis research. The well-known disadvantages of fluorescence microscopy, rapid bleaching, phototoxicity and out-of-focus contributions blurring the in-focus image are obstacles which still need to be overcome. Confocal fluorescence microscopy has the potential to improve our capabilities of analyzing cells, because of its excellent depth-discrimination and image processing power. We have been using a confocal fluorescence microscope for the study of the mechanism of poleward chromosome movement, and report here (1) a cell preparation technique, which allows labeling of fixation sensitive spindle antigens with acceptable microtubule preservation; (2) the use of image processing methods to represent the spatial distribution of various labeled elements in pseudocolour; (3) a novel immunoelectron microscopic labeling method for microtubules, which allows the visualization of their distribution in semithin sections at low magnification; and (4) a first attempt to study microtubule dynamics with a confocal fluorescence microscope in living cells, microinjected with rhodamine labeled tubulin. Our experience indicates that confocal fluorescence microscopy provides real advantages for the study of spatial colocalization of antigens in the mitotic spindle. It does not, however, overcome the basic limits of resolution of the light microscope. Therefore, it has been necessary to use an electron microscopic method. Our preliminary results with living cells show that it is possible to visualize the entire microtubule network in stereo, but that the sensitivity of the instrument is still too low to perform dynamic time studies. It will be worthwhile to further develop this new type of optical instrumentation and explore its usefulness on both fixed and living cells. 相似文献
72.
The Steady radial distribution of chemical species in a wire‐to‐cylinder ozone generator filled with pure oxygen has been computed by applying four different plasma chemistry models of increasing complexity. The most complete model considers ten species (e, O2 +, O2 ?, O3 ?, O?, O2, O2(1Δg), O2(1∑g +), O and O3) and 79 reactions, including ionization by electron impact, electron attachment and detachment, electron-ion recombination, charge transfer, etc. The chemical model is coupled with the electrical model through Poisson's equation. The spatially averaged ozone density has been computed as a function of the current intensity and compared with the experimental values obtained by UV spectroscopy. 相似文献
73.
van Gelderen Amos; Schoonen Rob; de Glopper Kees; Hulstijn Jan; Simis Annegien; Snellings Patrick; Stevenson Marie 《Canadian Metallurgical Quarterly》2004,96(1):19
The authors report results of a study into the role of components of first-language (L1; Dutch) and second-language (L2; English) reading comprehension. Differences in the contributions of components of L1 and L2 reading comprehension are analyzed, in particular processing speed in L1 and L2. Findings indicate that regression weights of the L1 and L2 components are different. Although correlations between most processing speed components and reading comprehension are substantial, there are no unique contributions to the explanation of either L1 or L2 reading comprehension when linguistic and metacognitive knowledge are accounted for. In addition, L1 reading comprehension is shown to have a large contribution to L2 reading comprehension, supporting theories of L1-L2 transfer of reading skills. Results are discussed from a developmental perspective. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
74.
Sialon ceramics are a modern type of engineering ceramics with excellent mechanical, thermal and corrosion resistant properties. This paper describes the structure characterisation of porous sialon ceramics. It is possible to significantly improve the strength and crack resistance of sialon ceramics as a result of a reduction of the volume fraction of porosity. 相似文献
75.
Leedham Beth; Meyerowitz Beth E.; Muirhead Jan; Frist William H. 《Canadian Metallurgical Quarterly》1995,14(1):74
We explored the relations between positive expectations and adjustment, adherence, and health in cardiac transplant patients. Thirty-one patients and their nurse completed questionnaires before transplantation and at 3 times after surgery. As predicted, patients' self-reported positive expectations were generally associated with good mood, adjustment to the illness, and quality of life, even in patients who experienced health setbacks. High preoperative expectations predicted later adherence to a complex medical regimen. Positive expectations measured before the transplant predicted a substantial amount of the variance in the nurse's ratings of physical health 6 months after surgery, covarying for adherence behavior and preoperative health. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
76.
A scheme of force variation during the compression of a spring in both elastic and elastic-plastic state is presented. For the elastic state it has been found that equivalent load increments occur with equivalent deflection increments. In the elastic-plastic state equivalent load increments correspond to higher deflection increments. Prestressing the spring increases the range of the elastic deformation of a spring. Equations for the determination of torsional moment during prestressing and relationships of total non-dilatational strain versus elastic strain and radii of elastic zone are also presented. The effect of characteristic spring dimensions and non-dilatational strain on spring deflection has been determined. A nomogram for the determination of the resultant equivalent strain as a function of external load, also considering residual stress distribution, has as well been elaborated. 相似文献
77.
Jan Paca Eva Klapkova Martin Halecky Kim Jones Carlos Riccardo Soccol 《Clean Technologies and Environmental Policy》2007,9(1):69-74
The removal of a mixture of painting solvents from waste air using a biofiltration process was evaluated in this project.
The pollutants removed included hydrophobic (aromatic hydrocarbons) and hydrophilic (water soluble ketones and esters) compounds.
A trickle bed reactor with a defined immobilized mixed culture on polyethylene Pall rings was utilized in this biodegradation
study. The removal efficiencies (RE) of the individual groups of pollutants during loading experiments were determined. An
increase of the aromatic hydrocarbons loading resulted in a drop of their REAROM with no effect on the RE value of ketones. The overloading of ketones caused a rapid drop in REAROM and a small drop in REKET. To achieve a restoration of the biocatalyst degradation properties after the increase in loading, an addition of phosphate
to the aqueous medium was implemented which successfully restored the removal efficiency. 相似文献
78.
In electrophotographic printing, a periodic clustered-dot halftone pattern is preferred for a smooth and stable result. In addition, the screen frequency should be high enough to minimize the visibility of the halftone textures and to ensure good detail rendition. However, at these frequencies, the halftone cell may contain too few pixels to provide a sufficient number of distinct gray levels. This will result in contouring and posterization. The traditional solution is to grow the clusters asynchronously within a repeating block of clusters known as a supercell. The growth of each individual cluster is governed by a microscreen. The order in which the clusters grow within the supercell is determined by a macroscreen. Typically, the macroscreen is a recursive pattern due to Bayer. In highlights and shadows, this ordering results in visible artifacts. Replacing the Bayer screen by a stochastic macroscreen eliminates these artifacts, but results in new artifacts. In this paper, we propose a new composite screen architecture that employs multiple microscreens and multiple macroscreens in the highlights and shadows. These screens are jointly designed by using the direct binary search (DBS) algorithm. 相似文献
79.
Paulussen-Hoogeboom Marja C.; Stams Geert Jan J. M.; Hermanns Jo M. A.; Peetsma Thea T. D. 《Canadian Metallurgical Quarterly》2007,43(2):438
This meta-analytic review (k = 62 studies; N = 7,613 mother-child dyads) shows that effect sizes for the association between child negative emotionality and parenting were generally small and were moderated by sample and measurement characteristics. The association between more child negative emotionality and less supportive parenting was relatively strong in lower socioeconomic status families, reversed in higher socioeconomic status families, and limited to studies with relatively high percentages of participants from ethnic minorities and studies using parent report to assess negative emotionality. Higher levels of child negative emotionality were associated with more restrictive control in samples with less than 75% 1st-born children, as well as in infants and preschoolers, and in studies using parent report or composite measures to assess both negative emotionality and restrictive parenting. Finally, more child negative emotionality was associated with less inductive control. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
80.