全文获取类型
收费全文 | 1893篇 |
免费 | 114篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 476篇 |
金属工艺 | 39篇 |
机械仪表 | 32篇 |
建筑科学 | 77篇 |
矿业工程 | 2篇 |
能源动力 | 59篇 |
轻工业 | 166篇 |
水利工程 | 7篇 |
石油天然气 | 3篇 |
无线电 | 218篇 |
一般工业技术 | 381篇 |
冶金工业 | 101篇 |
原子能技术 | 24篇 |
自动化技术 | 411篇 |
出版年
2023年 | 24篇 |
2022年 | 42篇 |
2021年 | 45篇 |
2020年 | 56篇 |
2019年 | 54篇 |
2018年 | 57篇 |
2017年 | 73篇 |
2016年 | 70篇 |
2015年 | 55篇 |
2014年 | 67篇 |
2013年 | 133篇 |
2012年 | 116篇 |
2011年 | 157篇 |
2010年 | 106篇 |
2009年 | 107篇 |
2008年 | 114篇 |
2007年 | 93篇 |
2006年 | 92篇 |
2005年 | 76篇 |
2004年 | 60篇 |
2003年 | 53篇 |
2002年 | 46篇 |
2001年 | 16篇 |
2000年 | 17篇 |
1999年 | 25篇 |
1998年 | 25篇 |
1997年 | 35篇 |
1996年 | 22篇 |
1995年 | 17篇 |
1994年 | 19篇 |
1993年 | 20篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1954年 | 1篇 |
1935年 | 1篇 |
排序方式: 共有2008条查询结果,搜索用时 0 毫秒
991.
Manel Ziadi Gaëlle Bergot Pascal Courtin Emilie Chambellon Moktar Hamdi Mireille Yvon 《International Dairy Journal》2010,20(1):25-31
Two wild-type Lactococcus lactis strains isolated from naturally Tunisian fermented milk (Leben), and one laboratory strain, were used to investigate the ability of L. lactis to transform amino acids into aroma compounds during milk fermentation. The α-ketoacid acceptor used for leucine transamination, the first step of catabolism, was identified by gas chromatography/mass spectrometry analysis of the 15N-labelled amino acids that formed from 15N-labelled leucine in fermented milk. Furthermore, the amino acids produced or catabolized by the laboratory strain via transamination were identified by comparing the free amino acids in milk fermented with the wild-type strain and the double mutant for aromatic and branched-chain aminotransferases, which cannot transaminate amino acids. The three L. lactis strains strongly catabolized leucine and valine during milk fermentation. The principal amino acid formed via leucine and valine transamination was glutamate indicating that α-ketoglutarate was the principal α-ketoacid acceptor and was generated during milk fermentation. 相似文献
992.
Murielle Juhel-Gaugain Marie-Pierre Fourmond Bernard Delepine Michel Laurentie Brigitte Roudaut Pascal Sanders 《Food Additives & Contaminants》2005,22(3):221-233
Two interlaboratory studies were organized in 2002-2003 in order to check the proficiency of laboratories in confirming the presence of sulfonamide residues in muscle and milk. These studies involved 25 EU National Reference Laboratories (NRLs) from 21 different European countries in charge of statutory monitoring of antimicrobial residues in food of animal origin at a national level. The study was conducted according to international and national guidelines by the Community Reference Laboratory (CRL) in charge of antimicrobial substances. Four different test matrices of sheep muscle and four different test matrices of bovine milk containing different sulfonamide substances were prepared and sent to the participants. Each participant was asked to use his own routine confirmatory method and to analyse each sample in triplicate within a period of about six weeks during which the stability of the materials was checked by the organizer. The sulfonamide content of each material was determined by calculating the robust means of all the results and the deviation of the results from the assigned values was assessed by calculating Z-scores. Overall, results were satisfactory, particularly considering that it was the first proficiency test dealing with sulfonamides organised by the Community Reference Laboratory. 相似文献
993.
994.
Van Dijk Koene R. A.; Van Gerven Pascal W. M.; Van Boxtel Martin P. J.; Van der Elst Wim; Jolles Jelle 《Canadian Metallurgical Quarterly》2008,23(1):119
Recent large-scale longitudinal aging studies question earlier claims that higher education protects against cognitive decline in older age. In the present study, the authors addressed this issue by determining whether educational level had an attenuating effect on the rate of cognitive change assessed with a broad range of neuropsychological tests in a community sample of 872 healthy individuals aged 49 to 81 years at baseline. The participants were followed for 6 years and were tested 3 times (at baseline and at 3 and 6 years after baseline). Results of linear mixed-model analyses showed that education had no significant effect on cognitive change over time. These results are discussed in terms of the age range of the sample, definition and range of education, cognitive measures used, length of the study and number of consecutive assessments, and confounding effect of health. The findings question the extent of the presumed protective effects of higher education on cognitive decline during normal aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
995.
Vincent Gouttenoire Thomas Barois Sorin Perisanu Jean‐Louis Leclercq Stephen T. Purcell Pascal Vincent Anthony Ayari 《Small (Weinheim an der Bergstrasse, Germany)》2010,6(9):1060-1065
Electromechanical resonators are a key element in radio‐frequency telecommunication devices and thus new resonator concepts from nanotechnology can readily find important industrial opportunities. Here, the successful experimental realization of AM, FM, and digital demodulation with suspended single‐walled carbon‐nanotube resonators in a field‐effect transistor configuration is reported. The crucial role played by the electromechanical resonance in demodulation is clearly demonstrated. The FM technique is shown to lead to the suppression of unwanted background signals and the reduction of noise for a better detection of the mechanical motion of nanotubes. The digital data‐transfer rate of standard cell‐phone technology is within the reach of these devices. 相似文献
996.
Damien Eynard Pascal Vasseur Cédric Demonceaux Vincent Frémont 《Autonomous Robots》2012,33(1-2):157-172
Knowledge of altitude, attitude and motion is essential for an Unmanned Aerial Vehicle during critical maneuvers such as landing and take-off. In this paper we present a hybrid stereoscopic rig composed of a fisheye and a perspective camera for vision-based navigation. In contrast to classical stereoscopic systems based on feature matching, we propose methods which avoid matching between hybrid views. A?plane-sweeping approach is proposed for estimating altitude and detecting the ground plane. Rotation and translation are then estimated by decoupling: the fisheye camera contributes to evaluating attitude, while the perspective camera contributes to estimating the scale of the translation. The motion can be estimated robustly at the scale, thanks to the knowledge of the altitude. We propose a robust, real-time, accurate, exclusively vision-based approach with an embedded C++ implementation. Although this approach removes the need for any non-visual sensors, it can also be coupled with an Inertial Measurement Unit. 相似文献
997.
Laëtitia Alleron Arbia Khemiri Mohamad Koubar Christian Lacombe Laurent Coquet Pascal Cosette Thierry Jouenne Jacques Frere 《Water research》2013
Legionella pneumophila is the agent responsible for legionellosis. Numerous bacteria, including L. pneumophila, can enter into a viable but not culturable (VBNC) state under unfavorable environmental conditions. In this state, cells are unable to form colonies on standard medium but are still alive. Here we show that VBNC L. pneumophila cells, obtained by monochloramine treatment, were still able to synthesize proteins, some of which are involved in virulence. Protein synthesis was measured using 35S-labeling and the proteomes of VBNC and culturable cells then compared. This analysis allowed the identification of nine proteins that were accumulated in the VBNC state. Among them, four were involved in virulence, i.e., the macrophage infectivity potentiator protein, the hypothetical protein lpl2247, the ClpP protease proteolytic subunit and the 27 kDa outer membrane protein. Others, i.e., the enoyl reductase, the electron transfer flavoprotein (alpha and beta subunits), the 50S ribosomal proteins (L1 and L25) are involved in metabolic and energy production pathways. However, resuscitation experiments performed with Acanthamoeba castellanii failed, suggesting that the accumulation of virulence factors by VBNC cells is not sufficient to maintain their virulence. 相似文献
998.
Hlne Jullien Delphine Brissy Rmy Sylvain Pascal Retailleau Jean‐Valre Naubron Serafino Gladiali Angela Marinetti 《Advanced Synthesis \u0026amp; Catalysis》2011,353(7):1109-1124
Platinum(II) complexes which combine six‐membered N‐heterocyclic carbene‐containing metallacyclic units and monodentate chiral phosphines have been prepared. The key step of their synthesis is the intramolecular oxidative addition of N‐2‐iodobenzylimidazolylidene‐platinum(0)‐diene complexes in the presence of the chiral phosphorus ligands. The platinum(II) metallacycles have been used as well‐defined pre‐catalysts for the enantioselective cycloisomerization of nitrogen‐tethered 1,6‐enynes into 3‐azabicyclo[4.1.0]hept‐4‐enes. High enantiomeric excesses have been obtained with either Monophos or phenyl‐Binepine based catalysts (ees=82–96%), although phenyl‐Binepine outperforms Monophos in these reactions. The absolute configuration of the final 3‐azabicyclo[4.1.0.]heptenes has been established by X‐ray diffraction studies. The method has been extended then to the cycloisomerization of dienynes with enantiotopic vinyl groups. An (S)‐phenyl‐Binepine‐platinum(II) complex allows total diastereoselectivity and high enantioselectivity levels to be attained in these reactions (ees up to 95%) which represent the first enantioselective desymetrizations achieved via enyne cycloisomerizations. 相似文献
999.
Variation in fibre volume fraction is a common characteristic of composites made by an injection moulding process. The effect of this variation on fracture toughness is not yet fully investigated. This paper examines the fracture in fabric carbon/epoxy composite laminates under a wide range of combined mode-I and mode-II delamination. A total of 60 double cantilever beam and edge-notched flexure specimens are manufactured by resin transfer moulding with two different fibre volume fractions. It was observed that increasing the fibre volume fraction decreased the initiation fracture toughness in all mixed-mode ratios. This behaviour is believed to relate to the fact that the initiation fracture energy is dominantly absorbed by the resin-rich regions at the delamination tip. In contrast, an increase in fibre volume fraction was found to increase the propagation fracture toughness at high mode-I contribution where the fibre bridging is believed to be the major energy dissipating mechanism. Fractographic analysis also demonstrated that an increase in contribution of mode-II delamination is accompanied by a decrease in fibre bridging and an increase in shear hackles. 相似文献
1000.
In this paper we present new propositions about the ontology of design and a clarification of its position in the general context of rationality and knowledge. We derive such ontology from a comparison between formal design theories developed in two different scientific fields: Engineering and Set theory. We first build on the evolution of design theories in engineering, where the quest for domain independence and “generativity” has led to formal approaches, likewise C–K theory, that are independent of what has to be designed. Then we interpret Forcing, a technique in Set theory developed for the controlled invention of new sets, as a general design theory. Studying similarities and differences between C–K theory and Forcing, we find a series of common notions like “d-ontologies”, “generic expansion”, “object revision”, “preservation of meaning” and “K-reordering”. They form altogether an “ontology of design” which is consistent with unique aspects of design. 相似文献