全文获取类型
收费全文 | 1270篇 |
免费 | 19篇 |
国内免费 | 7篇 |
学科分类
工业技术 | 1296篇 |
出版年
2017年 | 11篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 68篇 |
2012年 | 17篇 |
2011年 | 18篇 |
2010年 | 28篇 |
2009年 | 26篇 |
2008年 | 21篇 |
2007年 | 15篇 |
2006年 | 25篇 |
2005年 | 21篇 |
2004年 | 33篇 |
2003年 | 32篇 |
2002年 | 17篇 |
2001年 | 17篇 |
2000年 | 19篇 |
1999年 | 17篇 |
1998年 | 91篇 |
1997年 | 84篇 |
1996年 | 58篇 |
1995年 | 57篇 |
1994年 | 33篇 |
1993年 | 43篇 |
1992年 | 37篇 |
1991年 | 35篇 |
1990年 | 23篇 |
1989年 | 23篇 |
1988年 | 22篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 12篇 |
1984年 | 16篇 |
1983年 | 22篇 |
1982年 | 11篇 |
1981年 | 17篇 |
1980年 | 17篇 |
1979年 | 22篇 |
1978年 | 13篇 |
1977年 | 37篇 |
1976年 | 58篇 |
1975年 | 6篇 |
1969年 | 7篇 |
1968年 | 6篇 |
1967年 | 9篇 |
1966年 | 8篇 |
1965年 | 5篇 |
1955年 | 6篇 |
1948年 | 5篇 |
排序方式: 共有1296条查询结果,搜索用时 0 毫秒
1.
R.N. ARNOLD K.K. SCHELLER S.C. ARP S.N. WILLIAMS D.M. SCHAEFER 《Journal of food science》1993,58(1):28-33
The effect of long-term feeding (252 days) of three supplemental levels of α-tocopheryl acetate (actual 0, 360 and 1290 IU/head/day) on meat quality was evaluated in Holstein and beef breed steers. Tissue vitamin E concentrations were increased by each increment of supplementation. The color display life of fresh beef under simulated retail conditions was extended 2 to 5 days by vitamin E and lipid oxidation was markedly reduced. Microbial population was not affected by level of supplementation. No deterioration in sensory quality occurred for steaks from supplemented steers that were displayed until the time steaks from unsupplemented steers discolored. 相似文献
2.
J. T. DICKINSON L. C. JENSEN W. DAVID WILLIAMS 《Journal of the American Ceramic Society》1985,68(5):235-240
We present measurements of the electron, positive ion, and photon emission accompanying the fracture in vacuum of poly-crystalline 95/5 lead zirconate-titanate. The intensities of the charged-particle components of this fractoemission are shown to depend strongly on the direction (relative to the direction of fracture) and magnitude of polarization. The most intense emission is observed when the fracture surfaces are perpendicular to the polarization direction. The emission intensity increases monotonically with polarization. These results are interpreted in terms of a model involving charge separation on the fracture surfaces leading to a microdischarge during fracture. Implications to the interpretation of triboluminesence effects are discussed. 相似文献
3.
Joel P. Martin J. Edward Swan II Robert J. Moorhead II Zhanping Liu Shangshu Cai 《Computer Graphics Forum》2008,27(3):991-998
We present the results from a user study looking at the ability of observers to mentally integrate wind direction and magnitude over a vector field. The data set chosen for the study is an MM5 (PSU/NCAR Mesoscale Model) simulation of Hurricane Lili over the Gulf of Mexico as it approaches the southeastern United States. Nine observers participated in the study. This study investigates the effect of layering on the observer's ability to determine the magnitude and direction of a vector field. We found a tendency for observers to underestimate the magnitude of the vectors and a counter‐clockwise bias when determining the average direction of a vector field. We completed an additional study with two observers to try to uncover the source of the counter‐clockwise bias. These results have direct implications to atmospheric scientists, but may also be able to be applied to other fields that use 2D vector fields. 相似文献
4.
Crowe T.W. Bishop W.L. Porterfield D.W. Hesler J.L. Weikle R.M. II 《Solid-State Circuits, IEEE Journal of》2005,40(10):2104-2110
The terahertz region of the electromagnetic spectrum, spanning from 100 GHz through 10 THz, is of increasing importance for a wide range of scientific, military and commercial applications. This interest is spurred by the unique properties of this spectral band and the very recent development of convenient terahertz sources and detectors. However, the terahertz band is also extremely challenging, in large part because it spans the transition from traditional electronics to photonics. This paper reviews the importance of this frequency band and summarizes the efforts of scientists and engineers to span the "terahertz technology gap." The emphasis is on solid-state circuits that use nonlinear diodes to translate the functionality of microwave technology to much higher frequencies. 相似文献
5.
6.
NV Zheleznova SL Mukomolov AB Zhebrun FS Noskov II Malkova EP Shargorodskaia AD Al'tshte?n VA Pliutnikova IN Lavrent'eva NN Ptichnikova 《Canadian Metallurgical Quarterly》1996,(5):49-53
The use of a recombinant poxvirus (RPV) strain, expressing HBsAg in the process of reproduction in different bioreactor systems under stationary and bioreactor conditions of cultivation, made it possible to obtain highly purified HBsAg. The identity and purity of HBsAg was confirmed by the analysis of its amino acid composition, SDS electrophoresis in polyacrylamide gel, electron microscopy and high-performance liquid chromatography. Good prospects of the use of RPV-expressed gene engineering HBsAg as the basis vaccines against hepatitis B was demonstrated in 10 experimental batches of vaccine. All batches of the preparation had pronounced immunogenicity and were safe and nontoxic in animal experiments. The ID50 of experimental batches did not exceed 211 ng/ml, which, according to the data of comparative experiments, was lower than, or equal to, corresponding values of analogous foreign commercial preparations, based on plasma or yeast HBsAg. 相似文献
7.
Streifel R.J. Marks R.J. II El-Sharkawi M.A. Kerszenbaum I. 《Energy Conversion, IEEE Transaction on》1996,11(2):312-317
A method for detecting shorted windings in operational turbine-generators is described. The method is based on the traveling wave method described by El-Sharkawi, et. al. (1971). The method is extended in this paper to operational rotors by the application of a neural network feature extraction and novelty detection. The results of successful laboratory experiments are also reported 相似文献
8.
9.
Daniel Grosjean Eric Grosjean II Edwin L. Williams 《Israel journal of chemistry》1994,34(3-4):365-373
The atmospheric oxidation of the unsaturated aldehyde 2-ethyl acrolein, CH2=C(C2H5)CHO, has been studied in laboratory experiments involving the reaction of ozone with 2-ethyl acrolein in the dark (with cyclohexane added to scavenge the hydroxyl radical), and the sunlight irradiation of 2-ethyl acrolein with NO in air. The major carbonyl products of the 2-ethyl acrolein reaction with ozone are formaldehyde, acetaldehyde, and the dicarbonyl ethylglyoxal, CH3CH2COCHO. Sunlight irradiation of 2-ethyl acrolein and NO led to the formation of three carbonyls (formaldehyde, acetaldehyde, and ethylglyoxal) and three peroxyacyl nitrates, (RC(O)OONO2), including PAN (R = CH3), PPN (R = C2H5), and the unsaturated compound EPAN (R = CH2=C(C2H5)). Mechanisms are outlined for the reactions of ozone and of the hydroxyl radical with 2-ethyl acrolein. These mechanisms are consistent with the observed carbonyl and peroxyacyl nitrate products. Thermal decomposition, a major atmospheric removal process for peroxyacyl nitrates, has been studied for EPAN. The decomposition rate of EPAN relative to that of PAN is 0.59–0.73 at 292–294 K and 1 atm of air. Atmospheric implications of these results are discussed. 相似文献
10.
MICHAEL S. BRATAKOS THEODORE F. ZAFIROPOULOS PANAYIOTIS A. SISKOS PANAYIOTIS V. IOANNOU 《Journal of food science》1987,52(3):817-822
The total selenium within a wide variety (315 food items) of Greek foods was determined fluorimetrically. Rich selenium sources were the proteinaceous foods such as fish, meat, bread, and spaghetti. Butter, oils, vegetables, and fruits were poor sources. The selenium content of Greek foods was lower than that of many other countries and resembled more closely that of British foods. From available food consumption data and values in this study, it was estimated that the daily selenium intake of Greeks was 110 μg. 相似文献