全文获取类型
收费全文 | 1195篇 |
免费 | 81篇 |
国内免费 | 85篇 |
专业分类
电工技术 | 77篇 |
综合类 | 122篇 |
化学工业 | 159篇 |
金属工艺 | 59篇 |
机械仪表 | 73篇 |
建筑科学 | 60篇 |
矿业工程 | 45篇 |
能源动力 | 28篇 |
轻工业 | 157篇 |
水利工程 | 13篇 |
石油天然气 | 27篇 |
武器工业 | 7篇 |
无线电 | 126篇 |
一般工业技术 | 102篇 |
冶金工业 | 92篇 |
原子能技术 | 20篇 |
自动化技术 | 194篇 |
出版年
2021年 | 4篇 |
2020年 | 13篇 |
2019年 | 18篇 |
2018年 | 17篇 |
2017年 | 12篇 |
2016年 | 20篇 |
2015年 | 20篇 |
2014年 | 26篇 |
2013年 | 24篇 |
2012年 | 34篇 |
2011年 | 24篇 |
2010年 | 17篇 |
2009年 | 31篇 |
2008年 | 33篇 |
2007年 | 40篇 |
2006年 | 50篇 |
2005年 | 28篇 |
2004年 | 61篇 |
2003年 | 145篇 |
2002年 | 208篇 |
2001年 | 172篇 |
2000年 | 65篇 |
1999年 | 44篇 |
1998年 | 37篇 |
1997年 | 13篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1989年 | 5篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1983年 | 4篇 |
1963年 | 4篇 |
1958年 | 4篇 |
1957年 | 3篇 |
1943年 | 12篇 |
1942年 | 13篇 |
1941年 | 9篇 |
1940年 | 8篇 |
1939年 | 8篇 |
1938年 | 6篇 |
1937年 | 8篇 |
1933年 | 3篇 |
1931年 | 3篇 |
1929年 | 3篇 |
1928年 | 3篇 |
1921年 | 3篇 |
1915年 | 4篇 |
排序方式: 共有1361条查询结果,搜索用时 31 毫秒
91.
92.
93.
M Orth M Hanisch G Kr?ning M Porsch-Ozcürümez H Wieland C Luley 《Canadian Metallurgical Quarterly》1998,44(7):1459-1465
A time-consuming sample preparation and measuring procedure is required for the quantitation of retinyl palmitate by HPLC. We developed a fluorometric method for the determination of total retinyl esters in chylomicrons, chylomicron remnants, and VLDL. This method is precise, sensitive, rapid, simple, and particularly useful for large-scale studies of postprandial lipid metabolism. Because the turbidity of postprandial lipemic samples interferes with the fluorescence measurement, all samples were incubated for 10 min with a clearing buffer containing esterase and detergents. This buffer eliminates the turbidity and hydrolyzes all retinyl esters to retinol. The fluorescence signal (excitation wavelength, 330 nm; emission wavelength, 490 nm) was linear from 0.1 mg/L up to 4 mg/L retinyl palmitate, and the CVs were 3.6% within-run and 5.1% within-series. A first application studied postprandial lipoproteins, which were first separated by ultracentrifugation and then subjected to size exclusion chromatography. Fluorescence analysis revealed that the chylomicron density fraction contains large amounts of chylomicron remnants. 相似文献
94.
95.
Ludwig von Bernus Werner Rathgeb Rudi Schmid Friedrich Mohr Michael Krning 《Nuclear Engineering and Design》1994,151(2-3)
A tendency towards growing requirements for the inspection of austenitic piping can be observed in several countries. In Germany the revised KTA rule demands the UT inspection of austenitic and dissimilar metal welds in piping with diameters of 200 mm or more.On the basis of experience gained from austenitic piping with integranular stress corrosion cracking (IGSCC), longitudinal waves and mode conversion techniques are used. Depending on the geometry, material and grain orientation, spurious signals can be observed which require additional evaluation or analysis measurements.A promising new technique is based on horizontally polarized shear (SH) waves generated by electromagnetic acoustic transducers (EMATs). Investigations in the laboratory and field inspections showed that SH waves are well suited for the detection of longitudinal flaws, especially where the weld can be examined from one side only.For the complete solution of a given inspection problem SH waves can be combined with well-known standard techniques in order to provide redundant information for the characterization and sizing of indications.The investigation of possibilities of SH waves showed that the problem of cast austenitic steel inspection might not be solved using this technique. However, measurements using low frequency UT transducers showed promising results. 相似文献
96.
Erdmann N Betti M Kollmer F Benninghoven A Grüning C Philipsen V Lievens P Silverans RE Vandeweert E 《Analytical chemistry》2003,75(13):3175-3181
The resonance and nonresonant laser ionization of uranium atoms sputtered from thin metal films and individual micrometer-size uranium oxide particles, respectively, was studied to evaluate a new setup for the analysis of actinide-containing micrometer-size particles. Experiments using nonresonant (193-nm) ionization of atoms and molecules sputtered from micrometer-size uranium oxide particles have shown that the uranium detection efficiencies for sputtered neutral atoms are approximately 2 orders of magnitude higher than for secondary ions. In uranium particles of 0.5-microm diameter, 6 x 10(6) atoms of 235U were easily detected and the isotopic ratio of 235U/238U = 0.0048 +/- 4.6% is in excellent agreement with the certified value. The use of two-color, two-step resonance ionization of the sputtered neutral uranium atoms from thin films was investigated. Several excitation schemes were tested, and a significant population of several low-lying metastable states after ion sputtering was observed. Autoionizing states for double-resonant ionization were determined, and the high selectivity of ionization schemes involving these autoionizing states was illustrated by comparing the flight-time distributions of different sputtered species obtained both by resonance and nonresonant multiphoton (355-nm) laser postionization. Ideally, the options for resonance as well as nonresonant ionization would be combined in a single setup, to obtain a large gain in sensitivity and selectivity. Thus, information about the main components as well as specific isotopic information of a trace element could be obtained from the same single particle. 相似文献
97.
M. Bäcker S. Beging M. Biselli J. Wang W. Zang M.J. Schöning 《Electrochimica acta》2009,54(25):6107-9678
In this study, a concept for a silicon-based modular solid-state sensor system for inline multi-parameter monitoring of cell-culture fermentation processes is presented. The envisaged multi-parameter sensor system consists of two identical sensor modules and is intended for continuous quantification of up to five (bio-)chemical and physical parameters, namely, glucose and glutamine concentration, pH value, electrolyte conductivity and temperature by applying different transducer principles and/or different operation modes. Experimental results for the field-effect electrolyte-insulator-semiconductor (EIS) sterilisable pH sensor and electrolyte conductivity sensor based on interdigitated electrodes are presented. The ongoing autoclaving does not have any significant impact on the pH-sensitive properties of a Ta2O5-gate EIS sensor. Even after 30 autoclaving cycles, the pH sensors show a clear pH response and nearly linear calibration curve with a slope of 57 ± 1 mV/pH. Additional scanning electron microscopy and ellipsometric investigations do not show any visible surface degradation or changes in the thickness of the pH-sensitive Ta2O5 layer. The preliminary results demonstrate the suitability of the developed EIS sensor for an inline pH measurement during a fermentation process. In addition, interdigitated electrodes of different geometries serving as electrolyte conductivity sensor have been tested for measurements in relatively high ionic-strength solutions. 相似文献
98.
99.
It still is a challenging development goal to improve sizing of di discontinuities by using NDT, since essential characteristics, as for instance crack depth extension, in many cases only can be evaluated within the scope of a large scale measurement: New NDT-techniques such as specially designed UT-probes to suit the test problem, and also a substantially extended theoretical background contribute to reliable statements concerning crack depth.The development of imaging UT-reconstruction methods will help to improve this situation. Practical experience with genuine testing problems are needed to judge the evidence of these methods. Experience with manual crack depth measurements is quite useful to create a practicable and reliable instrument based on reconstruction methods. 相似文献
100.
A. Poghossian M.H. Abouzar A. Razavi M. Bäcker N. Bijnens K. Haenen W. Moritz M.J. Schöning 《Electrochimica acta》2009,54(25):5981-1120
A capacitive field-effect EDIS (electrolyte-diamond-insulator-semiconductor) sensor with improved pH and penicillin sensitivity has been realised using a nanocrystalline-diamond (NCD) film as sensitive gate material. The NCD growth process on SiO2 as well as an additional surface treatment in oxidising medium have been optimised to provide high pH-sensitive, non-porous O-terminated films without damage of the underlying SiO2 layer. The surface morphology of O-terminated NCD thin films and the layer structure of EDIS sensors have been studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. To establish the relative coverage of the surface functional groups generated by the oxidation of NCD surfaces, X-ray photoelectron spectroscopy analysis was carried out. The hydrophilicity of NCD thin films has been studied by water contact-angle measurements. A nearly Nernstian pH sensitivity of 54-57 mV/pH has been observed for O-terminated NCD films treated in an oxidising boiling mixture for 80 min and in oxygen plasma. The high pH-sensitive properties of O-terminated NCD have been used to develop an EDIS-based penicillin biosensor. A freshly prepared penicillin biosensor possesses a high sensitivity of 85 mV/decade in the concentration range of 0.1-2.5 mM penicillin G. The lower detection limit is 5 μM. 相似文献