全文获取类型
收费全文 | 2168篇 |
免费 | 89篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 18篇 |
综合类 | 2篇 |
化学工业 | 627篇 |
金属工艺 | 71篇 |
机械仪表 | 48篇 |
建筑科学 | 79篇 |
矿业工程 | 5篇 |
能源动力 | 64篇 |
轻工业 | 191篇 |
水利工程 | 11篇 |
石油天然气 | 1篇 |
无线电 | 206篇 |
一般工业技术 | 462篇 |
冶金工业 | 101篇 |
原子能技术 | 36篇 |
自动化技术 | 341篇 |
出版年
2023年 | 9篇 |
2021年 | 47篇 |
2020年 | 25篇 |
2019年 | 26篇 |
2018年 | 41篇 |
2017年 | 51篇 |
2016年 | 47篇 |
2015年 | 35篇 |
2014年 | 71篇 |
2013年 | 131篇 |
2012年 | 128篇 |
2011年 | 159篇 |
2010年 | 114篇 |
2009年 | 123篇 |
2008年 | 136篇 |
2007年 | 110篇 |
2006年 | 113篇 |
2005年 | 80篇 |
2004年 | 68篇 |
2003年 | 63篇 |
2002年 | 78篇 |
2001年 | 42篇 |
2000年 | 40篇 |
1999年 | 33篇 |
1998年 | 39篇 |
1997年 | 38篇 |
1996年 | 27篇 |
1995年 | 29篇 |
1994年 | 25篇 |
1993年 | 28篇 |
1992年 | 16篇 |
1991年 | 18篇 |
1990年 | 21篇 |
1989年 | 18篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 13篇 |
1984年 | 16篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1976年 | 16篇 |
1975年 | 10篇 |
1974年 | 9篇 |
1973年 | 7篇 |
1972年 | 7篇 |
排序方式: 共有2263条查询结果,搜索用时 502 毫秒
71.
Quintana C Wu TD Delatour B Dhenain M Guerquin-Kern JL Croisy A 《Microscopy research and technique》2007,70(4):281-295
Neurodegenerative diseases induce morphological and chemical alterations in well-characterized regions of the brain. Understanding their pathological processes requires the use of methods that assess both morphological and chemical alterations in the tissues. In the past, microprobe approaches such as scanning electron microscopy combined with an X-ray spectrometer, Proton induced X-ray emission, secondary ion mass spectrometry (SIMS), and laser microprobe mass analysis have been used for the study of pathological human brain with limited success. At the present, new SIMS instruments have been developed, such as the NanoSIMS-50 ion microprobe, that allow the simultaneous identification of five elements with high sensitivity, at subcellular spatial resolution (about 50-100 nm with the Cs(+) source and about 150-200 nm with O(-) source). Working in scanning mode, 2D distribution of five elements (elemental maps) can be obtained, thus providing their exact colocalization. The analysis can be performed on semithin or ultrathin embedded sections. The possibility of using transmission electron microscopy and SIMS on the same ultrathin sections allows the correlation between structural and analytical observations at subcellular and ultrastructural level to be established. Our observations on pathological brain areas allow us to establish that the NanoSIMS-50 ion microprobe is a highly useful instrument for the imaging of the morphological and chemical alterations that take place in these brain areas. In the human brain our results put forward the subcellular distribution of iron-ferritin-hemosiderin in the hippocampus of Alzheimer disease patients. In the thalamus of transgenic mice, our results have shown the presence of Ca-Fe mineralized amyloid deposits. 相似文献
72.
Process scale-up remains a considerable challenge for environmental applications of non-thermal plasmas.Undersanding the impact of reactor hydrodynamics in the performance of the process is a key step to overcome this challenge.In this work,we apply chemical engineering concepts to analyse the impact that different non-thermal plasma reactor configurations and regimes,such as laminar or plug flow,may have on the reactor performance.We do this in the particular context of the removal of pollutants by non-thermal plasmas,for which a simplified model is available.We generalise this model to different reactor configurations and,under certain hypotheses,we show that a reactor in the laminar regime may have a behaviour significantly different from one in the plug flow regime,often assumed in the non-thermal plasma literature.On the other hand,we show that a packed-bed reactor behaves very similarly to one in the plug flow regime.Beyond those results,the reader will find in this work a quick introduction to chemical reaction engineering concepts. 相似文献
73.
Jorge Barrios Alain Piétrus Gonzalo Joya Aymée Marrero Héctor de Arazoza 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2013,17(2):239-253
In this paper we deal with the application of differential inclusions to modeling nonlinear dynamical systems under uncertainty in parameters. In this case, differential inclusions seem to be better suited to modeling practical situations under uncertainty and imprecision than formulations by means of fuzzy differential equations. We develop a practical algorithm to approximate the reachable sets of a class of nonlinear differential inclusion, which eludes the computational problems of a previous set-valued version of the Heun’s method. Our algorithm is based on a complete discretization (time and state space) of the differential inclusion and it suits hardware features, handling the memory used by the method in a controlled fashion during all iterations. As a case of study, we formulate a differential inclusion to model an epidemic outbreak of dengue fever under Cuban conditions. The model takes into account interaction of human and mosquito populations as well as vertical transmission in the mosquito population. It is studied from the theoretical point of view to apply the Practical Algorithm. Also, we estimate the temporal evolution of the different human and mosquito populations given by the model in the Dengue 3 epidemic in Havana 2001, through the computation of the reachable sets using the Practical Algorithm. 相似文献
74.
Alain Doyen Linda Saucier Lucie Beaulieu Yves Pouliot Laurent Bazinet 《Food chemistry》2012,132(3):1177-1184
Recently, a snow crab by-products hydrolysate has demonstrated antibacterial properties due to a peptide with a molecular weight of about 800 Da, but only at high concentration. Consequently, peptide hydrolysate has been fractionated to obtain peptides in a more purified form. The aim of this work was to separate a snow crab by-products hydrolysate by electrodialysis with ultrafiltration membranes (EDUF). EDUF, which allows separation of molecules according to their charges and molecular weights, was used to recover and concentrate the active antibacterial fraction. Two different ultrafiltration membranes (20 and 50 kDa) and two electrical field strengths (2 and 14 V/cm) were used as separation parameters. After EDUF separation, the 300-600 Da peptide molecular weight range was the most recovered with an abundance of 94%. Moreover, fractionation at 14 V/cm with ultrafiltration membranes of 50 kDa allowed the recovery of an anionic fraction which showed antibacterial properties on Escherichia coli ATCC 25922 and Listeria innocua HPB 13. 相似文献
75.
Li‐Chen Ou M. Ronnier Luo Pei‐Li Sun Neng‐Chung Hu Hung‐Shing Chen Shing‐Sheng Guan Andrée Woodcock José Luis Caivano Rafael Huertas Alain Treméau Monica Billger Hossein Izadan Klaus Richter 《Color research and application》2012,37(1):23-43
Psychophysical experiments were conducted in the UK, Taiwan, France, Germany, Spain, Sweden, Argentina, and Iran to assess colour emotion for two‐colour combinations using semantic scales warm/cool, heavy/light, active/passive, and like/dislike. A total of 223 observers participated, each presented with 190 colour pairs as the stimuli, shown individually on a cathode ray tube display. The results show consistent responses across cultures only for warm/cool, heavy/light, and active/passive. The like/dislike scale, however, showed some differences between the observer groups, in particular between the Argentinian responses and those obtained from the other observers. Factor analysis reveals that the Argentinian observers preferred passive colour pairs to active ones more than the other observers. In addition to the cultural difference in like/dislike, the experimental results show some effects of gender, professional background (design vs. nondesign), and age. Female observers were found to prefer colour pairs with high‐lightness or low‐chroma values more than their male counterparts. Observers with a design background liked low‐chroma colour pairs or those containing colours of similar hue more than nondesign observers. Older observers liked colour pairs with high‐lightness or high‐chroma values more than young observers did. Based on the findings, a two‐level theory of colour emotion is proposed, in which warm/cool, heavy/light, and active/passive are identified as the reactive‐level responses and like/dislike the reflective‐level response. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2012 相似文献
76.
77.
Marcela Trybula Tomasz Gancarz Wladyslaw Gasior Alain Pasturel 《Metallurgical and Materials Transactions A》2014,45(12):5517-5530
Physicochemical properties like density, surface tension, and viscosity of liquid binary Al-Li and Li-Zn alloys have been measured using draining crucible method. The experimentally measured surface-tension values have been compared to theoretical results based either on the Butler model or the compound formation model assuming the existence of the most favored A 1 B 2 and A 2 B 3 clusters. Several models for viscosity calculation have been also applied and discussed in confrontation with measured data. Finally, the clustering effects in the liquid Al-Li and Li-Zn alloys have been examined using two microscopic functions, i.e., the concentration fluctuation function in the long-wavelength limit and the Warren-Cowley short-range order parameter. 相似文献
78.
Maxim Stolyarchuk Julie Ledoux Elodie Maignant Alain Trouv Luba Tchertanov 《International journal of molecular sciences》2021,22(2)
Redox (reduction–oxidation) reactions control many important biological processes in all organisms, both prokaryotes and eukaryotes. This reaction is usually accomplished by canonical disulphide-based pathways involving a donor enzyme that reduces the oxidised cysteine residues of a target protein, resulting in the cleavage of its disulphide bonds. Focusing on human vitamin K epoxide reductase (hVKORC1) as a target and on four redoxins (protein disulphide isomerase (PDI), endoplasmic reticulum oxidoreductase (ERp18), thioredoxin-related transmembrane protein 1 (Tmx1) and thioredoxin-related transmembrane protein 4 (Tmx4)) as the most probable reducers of VKORC1, a comparative in-silico analysis that concentrates on the similarity and divergence of redoxins in their sequence, secondary and tertiary structure, dynamics, intraprotein interactions and composition of the surface exposed to the target is provided. Similarly, hVKORC1 is analysed in its native state, where two pairs of cysteine residues are covalently linked, forming two disulphide bridges, as a target for Trx-fold proteins. Such analysis is used to derive the putative recognition/binding sites on each isolated protein, and PDI is suggested as the most probable hVKORC1 partner. By probing the alternative orientation of PDI with respect to hVKORC1, the functionally related noncovalent complex formed by hVKORC1 and PDI was found, which is proposed to be a first precursor to probe thiol–disulphide exchange reactions between PDI and hVKORC1. 相似文献
79.
Olivier Quéméner Frédéric Joly Alain Neveu 《International Journal of Heat and Mass Transfer》2012,55(4):1197-1207
In this paper, we propose an extension of the amalgam method to reduce advection diffusion problem with time dependent parameters. From a full general basis, this technique consists to select rapidly the most influent modes, and to add to them the remaining modes balanced by a coefficient. The originality of this paper lies in the fast obtention of a full degraded model, used as a reference in a minimization process of the reduced model’s error. Transcribed to the physical space, this error approaches the error between the reduced model and the real physical finite elements model. The treated application is a disk rotating at a variable velocity with time dependent thermal inputs. Comparison between the reduced and the finite elements model gives a gain in term of computational time of 36 for a mean error on the entire domain equal to 0.42%. 相似文献
80.
Thomas Schareina Xiao-Feng Wu Alexander Zapf Alain Cotté Matthias Gotta Matthias Beller 《Topics in Catalysis》2012,55(7-10):426-431
The first copper-catalyzed trifluoromethylation of aryl halides was developed that utilizes inexpensive trifluoroacetates. Providing low concentrations of the most economically attractive and atom-efficient trifluoromethylation reagent this new protocol is advantageous compared to known procedures both economically and ecologically. 相似文献