全文获取类型
收费全文 | 2753篇 |
免费 | 127篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 27篇 |
综合类 | 3篇 |
化学工业 | 753篇 |
金属工艺 | 98篇 |
机械仪表 | 67篇 |
建筑科学 | 106篇 |
矿业工程 | 2篇 |
能源动力 | 83篇 |
轻工业 | 322篇 |
水利工程 | 9篇 |
石油天然气 | 2篇 |
无线电 | 293篇 |
一般工业技术 | 552篇 |
冶金工业 | 112篇 |
原子能技术 | 19篇 |
自动化技术 | 440篇 |
出版年
2023年 | 24篇 |
2022年 | 44篇 |
2021年 | 97篇 |
2020年 | 55篇 |
2019年 | 56篇 |
2018年 | 53篇 |
2017年 | 55篇 |
2016年 | 88篇 |
2015年 | 68篇 |
2014年 | 113篇 |
2013年 | 208篇 |
2012年 | 203篇 |
2011年 | 220篇 |
2010年 | 181篇 |
2009年 | 174篇 |
2008年 | 164篇 |
2007年 | 122篇 |
2006年 | 133篇 |
2005年 | 103篇 |
2004年 | 78篇 |
2003年 | 78篇 |
2002年 | 74篇 |
2001年 | 34篇 |
2000年 | 40篇 |
1999年 | 37篇 |
1998年 | 38篇 |
1997年 | 49篇 |
1996年 | 37篇 |
1995年 | 38篇 |
1994年 | 31篇 |
1993年 | 22篇 |
1992年 | 14篇 |
1991年 | 22篇 |
1990年 | 14篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 13篇 |
1986年 | 4篇 |
1985年 | 14篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1973年 | 4篇 |
排序方式: 共有2888条查询结果,搜索用时 15 毫秒
101.
Ana C. Borges A. Jayakrishnan Pierre-Etienne Bourban Christopher J.G. Plummer Dominique P. Pioletti Jan-Anders E. Månson 《Materials science & engineering. C, Materials for biological applications》2012,32(8):2235-2241
Poly(oxyethylene 20 sorbitan) monolaurate (Tween® 20) methacrylates were synthesized by coupling methacryloyl chloride (MeOCl) to Tween 20 in the presence of 4-(N,N-dimethylamino) pyridine, using THF as a solvent, in order to investigate their suitability as precursors for photopolymerizable hydrogels in tissue engineering applications. The degree of substitution could be controlled by adjusting the molar ratio of MeOCl and Tween 20, giving three different monomers: Tween 20 monomethacrylate, Tween 20 dimethacrylate and Tween 20 trimethacrylate. Combined 1 H NMR and MALDI-TOF MS confirmed these monomers to be of high purity and to have polydispersities less than 1.3. It was shown that aqueous solutions of the monomers were photoactive, all the methacrylate groups reacting within 30 minutes exposure to a UV light intensity of 145 mW/cm2. Aqueous Tween 20 trimethacrylate was then combined with N-vinyl-2-pyrrolidone (NVP), giving tough copolymer hydrogels on photopolymerization, whose swelling ratios and swelling rates could be tuned by varying the Tween 20 trimethacrylate content. The use of a flexible spacer with a multifunctional monomer gives a permanent three-dimensional network, whilst maintaining degrees of swelling of between 60 and 85%, with potential for a wide range of biological and non-biological applications. 相似文献
102.
Dominique Gay Nazha Selmaoui-Folcher Jean-Fran?ois Boulicaut 《Knowledge and Information Systems》2012,30(1):87-111
Feature construction has been studied extensively, including for 0/1 data samples. Given the recent breakthroughs in closedness-related
constraint-based mining, we are considering its impact on feature construction for classification tasks. We investigate the
use of condensed representations of frequent itemsets based on closedness properties as new features. These itemset types
have been proposed to avoid set counting in difficult association rule mining tasks, i.e. when data are noisy and/or highly
correlated. However, our guess is that their intrinsic properties (say the maximality for the closed itemsets and the minimality
for the δ-free itemsets) should have an impact on feature quality. Understanding this remains fairly open, and we discuss these issues
thanks to itemset properties on the one hand and an experimental validation on various data sets (possibly noisy) on the other
hand. 相似文献
103.
Sofie Van Regenmortel Liesbeth De Donder Sarah Dury An-Sofie Smetcoren Nico De Witte Dominique Verté 《Journal of population ageing》2016,9(4):315-344
In the last decade, there has been a growing awareness regarding social exclusion. Considering the ageing population and the likelihood of older people being socially excluded, the aims of this article are to: (1) review existing studies concerning social exclusion in later life; and (2) identify how environmental and life-course perspectives are presented in studies focusing on social exclusion in later life. A systematic review in seven scientific databases was conducted to explore the peer-reviewed evidence. In total, 26 articles were included and analysed. Findings describe the variety of methods, conceptualisation, dimensions and measures used in this recent area of research. Determinants of social exclusion in later life are discussed and life-course and environmental perspectives are examined. The discussion highlights the complex character of the concept and measurement of social exclusion, and the presence of general and age-specific dimensions of social exclusion in later life. The time and context relativity and the need for life-course and environmental perspectives on social exclusion in later life are discussed. Finally, future directions of research are discussed. 相似文献
104.
Henryk Paul Adam Morawiec Thierry Baudin 《Metallurgical and Materials Transactions A》2012,43(12):4777-4793
Early stages of recrystallization in alloys containing complex structure of second phase particles are of considerable practical interest. They were observed for the AA3104 alloy in which large particles occur against the background of randomly distributed dispersoids. The samples were deformed by equal channel angular pressing and then slightly annealed to obtain the state of partial recrystallization. The highly deformed alloy contained a structure of flat grains with the spacing between high-angle grain boundaries ranging from 100 nm to 1 ??m. On annealing, the structure coarsened and got transformed into nearly equiaxed grains by both discontinuous and continuous recrystallization. The nucleation of new grains was observed in statically recrystallized bulk samples using scanning electron microscopy, and during in-situ recrystallization in a transmission electron microscope. Special attention was paid to the nucleation of new grains in areas close to large second phase particles, where a relatively high stored energy was expected to stimulate nucleation. A particular role in the rise of nuclei is attributed to migration of low angle boundaries. During recrystallization at 623 K (350?°C), in most of the observed cases, the growth of grains occurred by coalescence of neighbouring cells and by migration of high-angle grain boundaries. These processes led to nearly equiaxed grains of similar size. Orientation mappings showed that although orientations of new grains were widely scattered, they were not completely random. 相似文献
105.
Motion planning is a fundamental problem in robotics that has motivated research since more than three decades ago. A large variety of algorithms have been proposed to compute feasible motions of multi-body systems in constrained workspaces. In recent years, some of these algorithms have surpassed the frontiers of robotics, finding applications in other domains such as industrial manufacturing, computer animation and computational structural biology. This paper concerns the latter domain, providing a survey on motion planning algorithms applied to molecular modeling and simulation. Both the algorithmic and application sides are discussed, as well as the different issues to be taken into consideration when extending robot motion planning algorithms to deal with molecules. From an algorithmic perspective, the paper gives a general overview of the different extensions to sampling-based motion planners. From the point of view of applications, the survey deals with problems involving protein folding and conformational transitions, as well as protein–ligand interactions. 相似文献
106.
Ahmad Rafsanjani Dominique Derome Falk K. Wittel Jan Carmeliet 《Composites Science and Technology》2012
The hygro-mechanical behavior of a hierarchical cellular material, i.e. growth rings of softwood is investigated using a two-scale micro-mechanics model based on a computational homogenization technique. The lower scale considers the individual wood cells of varying geometry and dimensions. Honeycomb unit cells with periodic boundary conditions are utilized to calculate the mechanical properties and swelling coefficients of wood cells. Using the cellular scale results, the anisotropy in mechanical and swelling behavior of a growth ring in transverse directions is investigated. Predicted results are found to be comparable to experimental data. It is found that the orthotropic swelling properties of the cell wall in thin-walled earlywood cells produce anisotropic swelling behavior while, in thick latewood cells, this anisotropy vanishes. The proposed approach provides the ability to consider the complex microstructure when predicting the effective mechanical and swelling properties of softwood. 相似文献
107.
Faez A.E. Mohammed Rahma Bchitou Ahmed Bouhaouss Saïd Gharby Hicham Harhar Dominique Guillaume Zoubida Charrouf 《Food chemistry》2013
Levels of eight dietary elements were assessed by ICP-AES in virgin edible and beauty argan oil samples prepared from four remote locations of the argan forest, and over a three-year period. The data showed sufficiently little variability to assess that all argan oil samples present, in terms of dietary elements, a similar composition, independently from the tree location within the argan forest. Therefore, adulteration detection by trace element analysis in edible and beauty argan oil is a method that can be generalised. 相似文献
108.
Crack stability is discussed as affected by their presence in statically-indeterminate beams, frames, rings, etc. loaded into the plastic range. The stability of a crack in a section, which has become plastic, is analyzed with the remainder of the structure elastic and with subsequent additional plastic hinges occurring. The reduction of energy absorption characteristics for large deformations is also discussed. The methods of elastic-plastic tearing instability are incorporated to show that in many cases the fully plastic collapse mechanism must occur for complete failure. 相似文献
109.
Jean-François Vanhumbeeck He Tian Dominique Schryvers Joris Proost 《Corrosion Science》2011,(4):1269-1277
The relationship between the microstructural and internal stress evolution during Ti anodising is discussed. Samples anodised galvanostatically to 12 V and 40 V, corresponding to different stages of the internal stress evolution, were examined by in-plane and cross-section transmission electron microscopy. Electron diffraction patterns have been complemented with stoichiometry data obtained from energy loss near edge structure spectra. The sample anodised to 40 V was observed to consist of two regions, with a crystallised inner region adjacent to the metal/oxide interface. Crystallisation of this region is associated with the presence of large compressive internal stresses which build up during anodising up to 12 V. 相似文献
110.