全文获取类型
收费全文 | 1164篇 |
免费 | 140篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 20篇 |
综合类 | 3篇 |
化学工业 | 346篇 |
金属工艺 | 24篇 |
机械仪表 | 12篇 |
建筑科学 | 57篇 |
矿业工程 | 5篇 |
能源动力 | 38篇 |
轻工业 | 93篇 |
水利工程 | 6篇 |
石油天然气 | 2篇 |
无线电 | 116篇 |
一般工业技术 | 225篇 |
冶金工业 | 110篇 |
原子能技术 | 10篇 |
自动化技术 | 238篇 |
出版年
2024年 | 3篇 |
2023年 | 31篇 |
2022年 | 46篇 |
2021年 | 76篇 |
2020年 | 50篇 |
2019年 | 67篇 |
2018年 | 68篇 |
2017年 | 67篇 |
2016年 | 71篇 |
2015年 | 53篇 |
2014年 | 68篇 |
2013年 | 70篇 |
2012年 | 64篇 |
2011年 | 94篇 |
2010年 | 40篇 |
2009年 | 41篇 |
2008年 | 47篇 |
2007年 | 53篇 |
2006年 | 35篇 |
2005年 | 17篇 |
2004年 | 17篇 |
2003年 | 16篇 |
2002年 | 10篇 |
2001年 | 13篇 |
2000年 | 9篇 |
1999年 | 12篇 |
1998年 | 33篇 |
1997年 | 18篇 |
1996年 | 13篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1980年 | 3篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1971年 | 2篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1942年 | 2篇 |
1908年 | 2篇 |
1904年 | 2篇 |
排序方式: 共有1305条查询结果,搜索用时 46 毫秒
231.
Adrian Körzendörfer Philipp Temme Eberhard Schlücker Jörg Hinrichs Stefan Nöbel 《Journal of dairy science》2018,101(5):3866-3877
Machinery such as pumps used for the commercial production of fermented milk products cause vibrations that can spread to the fermentation tanks. During fermentation, such vibrations can disturb the gelation of milk proteins by causing texture defects including lumpiness and syneresis. To study the effect of vibrations on yogurt structure systematically, an experimental setup was developed consisting of a vibration exciter to generate defined vibrational states and accelerometers for monitoring. During the fermentation of skim milk, vibrations (frequency sweep: 25 to 1,005 Hz) were introduced at different pH (5.7 to 5.1, step width 0.1 units) for 200 s. Physical properties of set gels (syneresis, firmness) and resultant stirred yogurts (visible particles, rheology, laser diffraction) were analyzed. Vibrational treatments at pH 5.5 to 5.2 increased syneresis, gel firmness, and the number of large particles (d > 0.9 mm); hence, this period was considered critical. The particle number increased from 34 ± 5 to 242 ± 16 particles per 100 g of yogurt due to vibrations at pH 5.4. In further experiments, yogurts were excited with fixed frequencies (30, 300, and 1,000 Hz). All treatments increased syneresis, firmness, and particle formation. As the strongest effect was observed by applying 30 Hz, the amplitude was set to vibration accelerations of a = 5, 10, 15, 20, and 25 m/s2 in the final experiments. The number of large particles was increased due to each treatment and a positive correlation with the amplitude was found. We concluded that vibrations during gelation increase the collision probability of aggregating milk proteins, resulting in a compressed set gel with syneresis. Resultant stirred yogurts exhibit large particles with a compact structure leading to a reduced water-holding capacity and product viscosity. 相似文献
232.
233.
Influence of Solute Content and Solidification Parameters on Grain Refinement of Aluminum Weld Metal
Philipp Schempp Carl Edward Cross Andreas Pittner Michael Rethmeier 《Metallurgical and Materials Transactions A》2013,44(7):3198-3210
Grain refinement provides an important possibility to enhance the mechanical properties (e.g., strength and ductility) and the weldability (susceptibility to solidification cracking) of aluminum weld metal. In the current study, a filler metal consisting of aluminum base metal and different amounts of commercial grain refiner Al Ti5B1 was produced. The filler metal was then deposited in the base metal and fused in a GTA welding process. Additions of titanium and boron reduced the weld metal mean grain size considerably and resulted in a transition from columnar to equiaxed grain shape (CET). In commercial pure aluminum (Alloy 1050A), the grain-refining efficiency was higher than that in the Al alloys 6082 and 5083. Different welding and solidification parameters influenced the grain size response only slightly. Furthermore, the observed grain-size reduction was analyzed by means of the undercooling parameter P and the growth restriction parameter Q, which revealed the influence of solute elements and nucleant particles on grain size. 相似文献
234.
Rennert R Neundorf I Jahnke HG Suchowerskyj P Dournaud P Robitzki A Beck-Sickinger AG 《ChemMedChem》2008,3(2):241-253
Now that the human genome has been decoded, the demand for novel therapeutic concepts, such as gene and stem cell therapy, is higher than ever before. Although new and better pharmaceutical agents are available, their efficient delivery to the intracellular site of action is still a serious challenge. A possible solution to this problem is the use of cell-penetrating peptides as delivery vectors, including derivatives of human calcitonin (hCT). The aim of this study was to synthesise novel branched hCT-derived peptides for the noncovalent delivery of nucleic acids. The uptake of the resulting oligocationic peptides into various cell lines as well as primary cells was monitored by fluorescence microscopy. To determine the appropriate peptide-plasmid charge ratios for efficient cell transfection, electromobility shift assays were carried out. Finally, flow cytometric and fluorescence microscopic studies of gene expression highlighted two novel hCT-derived peptides as highly effective in the delivery of noncovalently complexed plasmid DNA. Thus, the absence of cytotoxicity paired with highly efficient cell internalisation and transfection rates, in primary cells as well, make both peptides powerful candidates as drug delivery vectors, especially for plasmid DNA, for both in vivo and ex vivo therapeutic applications. 相似文献
235.
Zhao J Wang Z Mashayekhi H Mayer P Chefetz B Xing B 《Environmental science & technology》2012,46(10):5369-5377
Adsorption of phenanthrene on carbon nanotubes (CNTs) was examined in the presence of pulmonary surfactant (Curosurf) and its main components, dipalmitoyl phosphatidylcholine (DPPC) and bovine serum albumin (BSA). A passive-dosing method based on equilibrium partitioning from a preloaded polymer was successfully employed to measure phenanthrene binding and speciation at controlled freely dissolved concentrations while avoiding phase separation steps. Curosurf, DPPC, and BSA could all linearly solubilize phenanthrene, and phenanthrene solubilization by Curosurf was 4 times higher than individual components (DPPC or BSA). In the presence of Curosurf, DPPC or BSA, adsorption of phenanthrene by multiwalled CNTs (MWCNTs) was suppressed, showing competitive adsorption between pulmonary surfactant (or DPPC, BSA) and phenanthrene. Competitive adsorption between Curosurf and phenanthrene was the strongest. Therefore, when phenanthrene-adsorbed CNTs enter the respiratory tract, phenanthrene can be desorbed due to both solubilization and competition. The bioaccessibility of phenanthrene adsorbed on three MWCNTs in the respiratory tract would be positively related to the size of their outer diameters. Moreover, the contribution of solubilization and competition to desorption of phenanthrene from MWCNTs was successfully separated for the first time. These findings demonstrate the two mechanisms on how pulmonary surfactants can enhance desorption and thus possibly biological absorption of phenanthrene adsorbed on CNTs. 相似文献
236.
Thomas Ingram Sandra Storm Philipp Glembin Stephan Bendt Désirée Huber Tanja Mehling Prof. Dr.‐Ing. Irina Smirnova 《化学,工程师,技术》2012,84(6):840-848
Aqueous nonionic surfactant solutions split into two phases if the temperature is increased beyond a certain temperature, the so‐called cloud point temperature. Presently many different types of nonionic surfactants are produced commercially, out of these numerous have been considered as potential solvent for the cloud point extraction. In this work the crucial thermophysical properties of nonionic surfactants are investigated to determine the potential of surfactant systems for extraction processes. Phase equilibria of the binary system Triton X‐114/water and the ternary system Triton X‐114/water/phenol were measured. Based on these data the cloud point extraction was implemented in a continuous stirred extraction column. It was found, that increasing temperature within the column reduces the loss of surfactant and leads to an increasing enrichment factor. This work demonstrates that surfactant/water systems represent a suitable alternative to conventional solvents and can effectively be processed in continuous extraction columns. 相似文献
237.
In this paper we consider the design of spectrally efficient time-limited pulses for ultra-wideband (UWB) systems using an overlapping pulse position modulation scheme. For this we investigate an orthogonalization method, which was developed in 1950 by Löwdin [1] and [2]. Our objective is to obtain a set of N orthogonal (Löwdin) pulses, which remain time-limited and spectrally efficient for UWB systems, from a set of N equidistant translates of a time-limited optimal spectral designed UWB pulse. We derive an approximate Löwdin orthogonalization (ALO) by using circulant approximations for the Gram matrix to obtain a practical filter implementation as a tapped-delay-line [7]. We show that the centered ALO and Löwdin pulses converge pointwise to the same square-root Nyquist pulse as N tends to infinity. The set of translates of the square-root Nyquist pulse forms an orthonormal basis for the shift-invariant-space generated by the initial spectral optimal pulse. The ALO transformation provides a closed-form approximation of the Löwdin transformation, which can be implemented in an analog fashion without the need of analog to digital conversions. Furthermore, we investigate the interplay between the optimization and the orthogonalization procedure by using methods from the theory of shift-invariant-spaces. Finally we relate our results to wavelet and frame theory. 相似文献
238.
Andreas Hohenleutner Susanna Schmidbauer Rudolf Vasold Dominik Joosten Philipp Stoessel Herwig Buchholz Burkhard König 《Advanced functional materials》2012,22(16):3406-3413
This work reports the combinatorial synthesis and screening of phosphorescent iridium complexes as solution processable emitters for OLEDs. The approach taken here allows for the rapid synthesis, isolation, spectroscopic characterization and identification of the libraries based on chromatographic methods. Subsequent analysis of the irradiation induced degradation provides insight on the stability of the complexes under continuous excitation. The method is versatile and can easily be applied to other metal complexes or organic dyes for various applications, e.g., in electroluminescence, photovoltaics and sensing. 相似文献
239.
Total and size-segregated Pt and Pd emission factors from on-road vehicles were measured in the Kaisermühlen Tunnel in Vienna, Austria. Aerosol sampling was performed simultaneously inside and outside the tunnel during April and May 2005. Analysis of the acid-digested aerosol samples was performed using a preconcentration procedure with subsequent on-line detection by electro-thermal atomic absorption spectrometry (ETAAS). Inside the tunnel distinctly increased Pt and Pd concentrations were found with highest levels in total suspended particulate matter samples and reduced concentrations in the size-segregated PM10 and PM2.5 samples. Emission factors were calculated from concentration differences between tunnel inside and tunnel outside samples, the distance between tunnel entrance and sampling location, the ventilation rate, and the number of vehicles passing through the tunnel. Emission rates observed for Pt ranged from 38 +/- 5.9 to 146 +/- 13 ng veh(-1) km(-1), whereas the emission factors of Pd varied between 13 +/- 2.1 and 42 +/- 4.1 ng veh(-1) km(-1). Variations in the emission rates were assumed to originate from alterations in traffic conditions. Size-segregated investigations revealed that the major part of Pt and Pd emissions were released in the coarse aerosol mode (size fraction > PM10), nevertheless a considerable fraction (approximately 12% and approximately 22% respectively) was emitted in the inhalable PM2.5 fraction. 相似文献
240.
Christoph Jacoby Nadine Borg Philipp Heusch Martina Sauter Florian Bönner Reinhard Kandolf Karin Klingel Jürgen Schrader Ulrich Flögel 《Magma (New York, N.Y.)》2014,27(1):101-106