全文获取类型
收费全文 | 1883篇 |
免费 | 68篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 21篇 |
综合类 | 2篇 |
化学工业 | 425篇 |
金属工艺 | 47篇 |
机械仪表 | 31篇 |
建筑科学 | 95篇 |
矿业工程 | 3篇 |
能源动力 | 49篇 |
轻工业 | 132篇 |
水利工程 | 14篇 |
石油天然气 | 3篇 |
无线电 | 103篇 |
一般工业技术 | 339篇 |
冶金工业 | 298篇 |
原子能技术 | 10篇 |
自动化技术 | 380篇 |
出版年
2023年 | 22篇 |
2022年 | 42篇 |
2021年 | 66篇 |
2020年 | 38篇 |
2019年 | 36篇 |
2018年 | 48篇 |
2017年 | 48篇 |
2016年 | 55篇 |
2015年 | 69篇 |
2014年 | 66篇 |
2013年 | 119篇 |
2012年 | 100篇 |
2011年 | 128篇 |
2010年 | 82篇 |
2009年 | 82篇 |
2008年 | 104篇 |
2007年 | 88篇 |
2006年 | 77篇 |
2005年 | 57篇 |
2004年 | 56篇 |
2003年 | 40篇 |
2002年 | 32篇 |
2001年 | 27篇 |
2000年 | 26篇 |
1999年 | 44篇 |
1998年 | 89篇 |
1997年 | 55篇 |
1996年 | 36篇 |
1995年 | 16篇 |
1994年 | 22篇 |
1993年 | 25篇 |
1992年 | 4篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1977年 | 10篇 |
1976年 | 27篇 |
1975年 | 3篇 |
1973年 | 5篇 |
1972年 | 4篇 |
排序方式: 共有1952条查询结果,搜索用时 62 毫秒
81.
The mechanical power that is transferred to a liquid via the shaft of an agitator is obtained from a measurement of the electrical power flowing into the electric motor within an accuracy of less than 5%. The accuracy obtained is limited by the calibration procedure. As the implementation of an electric power measurement is both simple and comparatively inexpensive, the technique is suitable for a continuous monitoring of the power used by agitators in the process industries. 相似文献
82.
Linden (Tilia cordata) bark was shown to contain an antifeedant effective against the large pine weevil, Hylobius abietis. Soxhlet extraction of inner and outer bark resulted in an extract that showed antifeedant activity in a microfeeding assay. The extract was fractionated by chromatography on silica gel using gradient elution with solvents of increasing polarity. The content of the fractions obtained was monitored by thin layer- and gas chromatography. Fractions of similar chemical composition were merged. Two of the 17 fractions showed antifeedant activity in the microfeeding assay. Nonanoic acid was identified in both of these fractions. Subsequent testing in the microfeeding assay showed that nonanoic acid possessed strong antifeedant activity against H. abietis adults. 相似文献
83.
Heidi Markus Päivi Mäki-Arvela Narendra Kumar Natalya V. Kul’kova Patrik Eklund Rainer Sjöholm Bjarne Holmbom Tapio Salmi Dmitry Yu. Murzin 《Catalysis Letters》2005,103(1-2):125-131
The natural lignan hydroxymatairesinol was hydrogenolysed to a potential anticarcinogenic substance matairesinol over different carbon-supported palladium catalysts. The reaction was conducted in 2-propanol at 70 °C under hydrogen flow in a stirred glass reactor. The catalysts were characterised by N2-physisorption, CO pulse chemisorption and pH measurement of aqueous catalyst slurries. The most active catalyst (Degussa-Hüls) gave yields of matairesinol over 90% in 4 h. It was concluded that the acidity of the catalyst had a profound influence on the reaction rate. 相似文献
84.
Strohm E Herzner G Kaltenpoth M Boland W Schreier P Geiselhardt S Peschke K Schmitt T 《Journal of chemical ecology》2008,34(5):575-583
Females of the European beewolf, Philanthus triangulum, possess a large glove-shaped gland in the head, the postpharyngeal gland (PPG). They apply the content of the PPG to their
prey, paralyzed honeybees, where it delays fungal infestation. Here, we describe the chemical composition of the gland by
using combined GC-MS, GC-FTIR, and derivatization. The PPG of beewolves contains mainly long-chain unsaturated hydrocarbons
(C23–C33), lower amounts of saturated hydrocarbons (C14–C33), and minor amounts of methyl-branched hydrocarbons (C17–C31).
Additionally, the hexane-soluble gland content is comprised of small amounts of an unsaturated C25 alcohol, an unknown sesquiterpene,
an octadecenylmethylester, and several long-chain saturated (C25, C27) and unsaturated (C23–C27) ketones, some of which have
not yet been reported as natural products. Surprisingly, we found a dimorphism with regard to the major component of the PPG
with some females having (Z)-9-pentacosene, whereas others have (Z)-9-heptacosene as their predominant component. The biological relevance of the compounds for the prevention of fungal growth
on the prey and the significance of the chemical dimorphism are discussed. 相似文献
85.
Today's automation industry is driven by the need for an increased productivity, higher flexibility, and higher individuality, and characterized by tailor-made and more complex control solutions. In the processing industry, logic controller design is often a manual, experience-based, and thus an error-prone procedure. Typically, the specifications are given by a set of informal requirements and a technical flowchart and both are used to be directly translated into the control code. This paper proposes a method in which the control program is constructed as a sequential function chart (SFC) by transforming the requirements via clearly defined intermediate formats. For the purpose of analysis, the resulting SFC can be translated algorithmically into timed automata. A rigorous verification can be used to determine whether all specifications are satisfied if a formal model of the plant is available which is then composed with the automata model of the logic controller (LC). 相似文献
86.
Sven Schlumpberger Raymond B. Smith Huanhuan Tian Ali Mani Martin Z. Bazant 《American Institute of Chemical Engineers》2021,67(8):e17274
Shock electrodialysis is a recently developed electrochemical water treatment method that shows promise for water deionization and ionic separations. Although simple models and scaling laws have been proposed, a predictive theory has not yet emerged to fit experimental data and enable system design. Here, we extend and analyze existing “leaky membrane” models for the canonical case of a steady shock in crossflow, as in recent experimental prototypes. Two-dimensional numerical solutions are compared with analytical boundary-layer approximations and experimental data. The boundary-layer theory accurately reproduces the simulation results for desalination, and both models predict the data collapse of the desalination factor with dimensionless current, scaled to the incoming convective flux of cations. The numerical simulation also predicts the water recovery increase with current. Nevertheless, neither approach can quantitatively fit the transition from normal to over-limiting current, which suggests gaps in our understanding of extreme electrokinetic phenomena in porous media. 相似文献
87.
Particularly in fast rolling mills, conventional actuators reach their dynamic limits, when longitudinal thickness variations of the incoming strip shall be reduced with high accuracy by model-predictive roll gap control. Accordingly, the applicability of highly dynamic piezoelectric actuators in combination with electromechanical spindles and a high frequency precision measurement of the thickness in front of the roll gap was examined. Rolling tests in a cold rolling mill for narrow slit strips show that this novel concept is suitable to provide the required dynamic actuation especially at high rolling speed. 相似文献
88.
About 80% of all fire fatalities in Germany occur because of fires in homes. It has been known for some time that modern materials (synonym for materials consisting mostly of synthetic polymers) tend to burn differently from older materials (synonym for materials consisting mostly of fibrous cellulosic substances) and it has been acknowledged that the amount of combustible plastics in homes has increased significantly over the last decades. To investigate the influence of modern furniture and ventilation conditions of fires in homes, a series of four large‐scale tests in two living rooms (LRs) with adjacent rooms (ARs) was performed by BAM and the Frankfurt fire service. Two LRs, one with older furniture and one with modern furniture, were tested twice each. Each test started with the ignition of a paper cushion on an upholstered chair. The influence of modern materials on the fire development was investigated, as well as the influence of the ventilation on the fire development. In all settings, an upholstered chair was the first burning item. Results of the test series show that fires in rooms with modern furniture develop faster than fires in rooms with older furniture. This is true for temperature development in the rooms as well as for smoke production. 相似文献
89.
Sven H. Rouschop Samantha J. Snow Urmila P. Kodavanti Marie-Jos Drittij Lou M. Maas Antoon Opperhuizen Frederik J. van Schooten Alexander H. Remels Roger W. Godschalk 《International journal of molecular sciences》2021,22(14)
Previous research has shown that a perinatal obesogenic, high-fat diet (HFD) is able to exacerbate ozone-induced adverse effects on lung function, injury, and inflammation in offspring, and it has been suggested that mitochondrial dysfunction is implicated herein. The aim of this study was to investigate whether a perinatal obesogenic HFD affects ozone-induced changes in offspring pulmonary oxidant status and the molecular control of mitochondrial function. For this purpose, female Long-Evans rats were fed a control diet or HFD before and during gestation, and during lactation, after which the offspring were acutely exposed to filtered air or ozone at a young-adult age (forty days). Directly following this exposure, the offspring lungs were examined for markers related to oxidative stress; oxidative phosphorylation; and mitochondrial fusion, fission, biogenesis, and mitophagy. Acute ozone exposure significantly increased pulmonary oxidant status and upregulated the molecular machinery that controls receptor-mediated mitophagy. In female offspring, a perinatal HFD exacerbated these responses, whereas in male offspring, responses were similar for both diet groups. The expression of the genes and proteins involved in oxidative phosphorylation and mitochondrial biogenesis, fusion, and fission was not affected by ozone exposure or perinatal HFD. These findings suggest that a perinatal HFD influences ozone-induced responses on pulmonary oxidant status and the molecular control of mitophagy in female rat offspring. 相似文献
90.
Khaldoon O. Al-Nosairy Marc Horbrügger Sven Schippling Markus Wagner Aiden Haghikia Marc Pawlitzki Michael B. Hoffmann 《International journal of molecular sciences》2021,22(7)
The retinal ganglion cells (RGC) may be considered an easily accessible pathophysiological site of degenerative processes in neurological diseases, such as the RGC damage detectable in multiple sclerosis (MS) patients with (HON) and without a history of optic neuritis (NON). We aimed to assess and interrelate RGC functional and structural damage in different retinal layers and retinal sites. We included 12 NON patients, 11 HON patients and 14 healthy controls for cross-sectional multifocal pattern electroretinography (mfPERG) and optical coherence tomography (OCT) measurements. Amplitude and peak times of the mfPERG were assessed. Macula and disc OCT scans were acquired to determine macular retinal layer and peripapillary retinal nerve fiber layer (pRNFL) thickness. In both HON and NON patients the foveal N2 amplitude of the mfPERG was reduced compared to controls. The parafoveal P1 peak time was significantly reduced in HON only. For OCT, parafoveal (pfGCL) and perifoveal (pGCL) ganglion cell layer thicknesses were decreased in HON vs. controls, while pRNFL in the papillomacular bundle sector (PMB) showed reductions in both NON and HON. As the mfPERG derived N2 originates from RGC axons, these findings suggest foveal axonal dysfunction not only in HON, but also in NON patients. 相似文献