全文获取类型
收费全文 | 891篇 |
免费 | 78篇 |
专业分类
电工技术 | 12篇 |
综合类 | 11篇 |
化学工业 | 243篇 |
金属工艺 | 17篇 |
机械仪表 | 5篇 |
建筑科学 | 51篇 |
矿业工程 | 3篇 |
能源动力 | 40篇 |
轻工业 | 32篇 |
水利工程 | 2篇 |
石油天然气 | 4篇 |
武器工业 | 4篇 |
无线电 | 117篇 |
一般工业技术 | 165篇 |
冶金工业 | 85篇 |
原子能技术 | 1篇 |
自动化技术 | 177篇 |
出版年
2024年 | 3篇 |
2023年 | 32篇 |
2022年 | 31篇 |
2021年 | 74篇 |
2020年 | 48篇 |
2019年 | 27篇 |
2018年 | 43篇 |
2017年 | 32篇 |
2016年 | 48篇 |
2015年 | 32篇 |
2014年 | 62篇 |
2013年 | 63篇 |
2012年 | 49篇 |
2011年 | 65篇 |
2010年 | 40篇 |
2009年 | 38篇 |
2008年 | 32篇 |
2007年 | 37篇 |
2006年 | 13篇 |
2005年 | 17篇 |
2004年 | 19篇 |
2003年 | 11篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 10篇 |
1998年 | 21篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有969条查询结果,搜索用时 250 毫秒
161.
Elina Siirola Francesco G. Mutti Barbara Grischek Sebastian F. Hoefler Walter M. F. Fabian Gideon Grogan Wolfgang Kroutil 《Advanced Synthesis \u0026amp; Catalysis》2013,355(9):1703-1708
Prochiral bicyclic diketones were transformed to a single diastereomer of 3‐substituted cyclohexylamine derivatives via three consecutive biocatalytic steps. The two chiral centres were set up by a C C hydrolase (6‐oxocamphor hydrolase) in the first step and by an ω‐transaminase in the last step. The esterification of the intermediate keto acid was catalysed by a lipase in the second step if possible. For two substrates the C C hydrolytic step as well as the esterification could be run simultaneously in a one‐pot cascade in an organic solvent. In one example, the reaction mixture of the first two steps could be directly subjected to bio‐amination in an organic solvent without the need to change the reaction medium. Depending on the choice of the ω‐transaminase employed and the substrate the cis‐ as well as the trans‐diastereomers could be obtained in optically pure forms. 相似文献
162.
Vera J. Meyer Liang Fu Fabian Marquardt Meike Niggemann 《Advanced Synthesis \u0026amp; Catalysis》2013,355(10):1943-1947
A cycloisomerization of enynes with a benign calcium catalyst is presented exploring a complementary reactivity to that usually found in transition and noble metal‐catalyzed reactions. Thereby, a systematic investigation of the π‐activation of alkynes with reactive carbocations has been realized and ketones of various ring sizes were easily accessed. We are certain that these basic investigations will pave the way for the elaboration of further reactions based on the reaction principles discovered in the area of noble metal catalysis. 相似文献
163.
Enhancing the performances of analog circuits with sub-volt supplies becomes a great challenge for circuit designers. Techniques such as bulk-driven (BD) and quasi-floating gate (QFG) count among the suitable ones for ultra-low voltage (ULV) operation capability with extended input voltage range and simple CMOS circuitry. However, in comparison to the conventional gate-driven (GD) MOS transistor (MOST), these techniques suffer from several disadvantages such as low transconductance value and bandwidth that limit their applicability for some applications. Therefore, the idea of merging the BD and QFG techniques to eliminate their drawbacks appears as efficacious solution. This new merging is named bulk-driven quasi-floating gate (BD-QFG)* technique and in order to demonstrate its advantages in compassion to BD and QFG ones, this paper presents a comparison study of three ULV differential difference current conveyor (DDCC) blocks based on BD, QFG and BD-QFG techniques. The significant increment of the transconductance and the bandwidth values of the BD-QFG are clearly observed. The proposed CMOS structures of the DDCCs work at ±300 mV supply voltage and 18.5 µW power consumption. The simulation results using 0.18 µm CMOS n-Well process from TSMC show the features of the proposed circuits. 相似文献
164.
Eduardo Augusto Bezerra Fabian Vargas Michael Paul Gough 《Journal of Electronic Testing》2001,17(2):163-174
This paper revises and introduces to the field of reconfigurable computer systems, some traditional techniques used in the fields of fault-tolerance and testing of digital circuits. The target area is that of on-board spacecraft electronics, as this class of application is a good candidate for the use of reconfigurable computing technology. Fault tolerant strategies are used in order for the system to adapt itself to the severe conditions found in space. In addition, the paper describes some problems and possible solutions for the use of reconfigurable components, based on programmable logic, in space applications. 相似文献
165.
Etienne Buscail Guillaume Le Cosquer Fabian Gross Marine Lebrin Laetitia Bugarel Cline Deraison Nathalie Vergnolle Barbara Bournet Cyrielle Gilletta Louis Buscail 《International journal of molecular sciences》2021,22(18)
Between 20 to 25% of Crohn’s disease (CD) patients suffer from perianal fistulas, a marker of disease severity. Seton drainage combined with anti-TNFα can result in closure of the fistula in 70 to 75% of patients. For the remaining 25% of patients there is room for in situ injection of autologous or allogenic mesenchymal stem cells such as adipose-derived stem/stromal cells (ADSCs). ADSCs exert their effects on tissues and effector cells through paracrine phenomena, including the secretome and extracellular vesicles. They display anti-inflammatory, anti-apoptotic, pro-angiogenic, proliferative, and immunomodulatory properties, and a homing within the damaged tissue. They also have immuno-evasive properties allowing a clinical allogeneic approach. Numerous clinical trials have been conducted that demonstrate a complete cure rate of anoperineal fistulas in CD ranging from 46 to 90% of cases after in situ injection of autologous or allogenic ADSCs. A pivotal phase III-controlled trial using allogenic ADSCs (Alofisel®) demonstrated that prolonged clinical and radiological remission can be obtained in nearly 60% of cases with a good safety profile. Future studies should be conducted for a better knowledge of the local effect of ADSCs as well as for a standardization in terms of the number of injections and associated procedures. 相似文献
166.
S. Jahanian R. R. Kunde P. V. Kuppa 《Journal of Materials Engineering and Performance》2000,9(1):72-80
Post heat treatment of weldments is one of the most extensively used techniques by the industrial community for relieving
welding residual stresses. Such practice not only delays the manufacturing process, but also increases the cost of manufacturing.
In this article, an idea of a new welding technique, which is a promising tool for relieving welding residual stresses, is
presented. This method is anticipated to reduce the time and cost of the manufacturing process. The first part of the investigation
focuses on simulation of an idea by using an auxiliary heat source for creating a weldment with a more uniform temperature
distribution both spatially and temporally. A subroutine has been developed for optimizing the size of an auxiliary heat input
(AHI). The details of the subroutine and the parameters considered for optimizing the AHI are presented. The results show
that by increasing the stabilizing temperature and size of the AHI, the speed of cooling and spatial temperature gradient
decreases. This may result in reducing the level of residual stresses. 相似文献
167.
Fatigue analysis of complex support structures under wave loading. This paper deals with current results of support structures under wave loading. The applied time history‐based simulation techniques are described. A comparison between simulation results are compared to data measured at a research platform in the German Bight. The special requirements for the fatigue assessment with local concepts are shown using an exemplary support structure for offshore wind energy converters. 相似文献
168.
Anna-Sophie Hager Fabian Lauck Emanuele Zannini Elke K. Arendt 《European Food Research and Technology》2012,235(5):861-871
Due to increased awareness of consumers about the relationship between food and health as well as the requirements of people following a gluten-free diet, the production of cereal products from raw materials other than wheat is of interest. However, the elimination of the visco-elastic gluten protein represents a technological challenge. During this study, response surface methodology was applied to determine optimal formulations for the production of egg pasta from oat and teff flour. Wheat flour was used as a control. The resulting products were characterised regarding firmness and elasticity, stickiness and cooking loss. The results showed that the mechanical texture of oat and teff pasta was comparable to wheat pasta, however, elasticity was significantly reduced. Compositional analysis was carried out on flour raw materials as well as on the final pasta products, showing that regarding fibre and mineral content, oat and teff samples are nutritionally superior to wheat. In addition, the microstructure was investigated by means of scanning electron microscopy, allowing also the observation of structural changes occurring during cooking. Upon cooking, a distinct outer layer can be observed, resulting from protein denaturation and starch gelatinisation. This structural feature is clearly visible for cooked wheat pasta and but is less apparent for teff and oat pasta. 相似文献
169.
170.
Holger Pletsch Ling Peng Fabian Mitschang Andreas Schaper Michael Hellwig David Nette Andreas Seubert Andreas Greiner Seema Agarwal 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(1):201-208
Ultrasound mediated facile ligand exchange method in suspension for the formation of polystyrene?grafted silver nanoparticles is reported. Amazingly, this method allows even grafting of very high molecular weight polystyrenes (up to 217 200 g mol?1) having a single terminal thiol group at the chain end. Detailed studies are carried out to gain insights in the role of molecular weight of the ligands and the mechanism of the ligand exchange reactions. Key factors are determined to be the droplet formation by ultrasonification and low silver content, which enhances the availability of the terminal thiol end group significantly. The extraordinary compatibility of the ligand exchange method in particular regarding high molecular weights is attributed to hydrophilic orientation of the terminal thiol groups at the liquid?liquid interphase. This is proved conclusively by using an in situ method as a reference approach in which agglomeration occurs at considerably lower molecular weights due to the absence of preferred end group orientation within the polymer coil. In homogeneous phase only the chain length is found to be the crucial factor in stabilization of silver nanoparticles. 相似文献