全文获取类型
收费全文 | 996篇 |
免费 | 22篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 29篇 |
综合类 | 1篇 |
化学工业 | 99篇 |
金属工艺 | 28篇 |
机械仪表 | 22篇 |
建筑科学 | 18篇 |
矿业工程 | 4篇 |
能源动力 | 16篇 |
轻工业 | 40篇 |
水利工程 | 37篇 |
石油天然气 | 17篇 |
无线电 | 115篇 |
一般工业技术 | 62篇 |
冶金工业 | 406篇 |
原子能技术 | 13篇 |
自动化技术 | 117篇 |
出版年
2021年 | 4篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 11篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 29篇 |
2012年 | 12篇 |
2011年 | 14篇 |
2010年 | 23篇 |
2009年 | 20篇 |
2008年 | 18篇 |
2007年 | 11篇 |
2006年 | 21篇 |
2005年 | 19篇 |
2004年 | 35篇 |
2003年 | 31篇 |
2002年 | 21篇 |
2001年 | 21篇 |
2000年 | 19篇 |
1999年 | 14篇 |
1998年 | 88篇 |
1997年 | 65篇 |
1996年 | 50篇 |
1995年 | 39篇 |
1994年 | 27篇 |
1993年 | 36篇 |
1992年 | 28篇 |
1991年 | 26篇 |
1990年 | 22篇 |
1989年 | 17篇 |
1988年 | 22篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 16篇 |
1978年 | 10篇 |
1977年 | 37篇 |
1976年 | 55篇 |
1975年 | 4篇 |
1973年 | 5篇 |
1972年 | 3篇 |
1971年 | 4篇 |
1969年 | 4篇 |
排序方式: 共有1024条查询结果,搜索用时 31 毫秒
1.
Petroleum asphaltenes have been precipitated in solvent mixtures of n-heptane and toluene at various temperatures, likewise n-heptane asphaltenes have been dissolved in under similar conditions. This give added evidence to apparent hysteresis phenomenon between the two processes. The Asphaltenes have been characterized showing that although data is scattered convergence to certain structural parameters as incipient flocculation is approached. The asphaltenes are seen to consist of an associating and a non-associating part. The solubility of asphaltenes has been correlated/modelled using the Flory-Huggins equation using two different terms for the Flory parameter. A process for evaluation of best choice of solubility parameter and molar volume for the asphaltenes is proposed. Dissolution processes are seen to be best fitted by the equations. Based on these findings the asphaltenes are proposed to be formed by a colloidal and a true solution part. 相似文献
2.
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
3.
4.
II Kalachev AN Baídus' OA Ivanova EA Ganina IA Boldyrev EA Svetoch 《Canadian Metallurgical Quarterly》1997,(6):32-37
Unlike the glanders agent, the superficial structures of the melioidosis agent were demonstrated to be responsible for marked was immunosuppressive activity. Some antigenic fractions suppressing the blast transformation of lymphocytes, reducing the count of T helpers and profoundly potentiating the infection in vivo were isolated from P. pseudomallei cells. The immunogenic and immunosuppressive activities of both agents' superficial structures were studied by high performance chromatography. Antigenic complexes that were able to protect immunized laboratory animals against fatal infections and to prevent bacterial carriage due to the activation of T cells and to the bacterial activity of macrophages were identified. A composition comprising several immunogens was found to provide an additive protective action against both causative agents. Therefore, the composition may be considered to be a prototype of a molecular antipseudomonadic vaccine. 相似文献
5.
The failure characteristic of graphite polyetheretherketone (Gr/PEEK) under compression with a centrally located circular discontinuity was investigated through experimentation and a nonlinear ply-by-ply finite element technique. The stacking sequence of the laminates investigated were: [0 °16], [90 °16], [±45 °]4S [0 °/90 °]4S, and [0 °/ ± 45 0°/90 °]2S. In the experimentation, [90 °]16, [0 °/90 °]4S, and [0 °/ ±45 °/90 °]2S laminates, as well as three of the [0 °]16, failed due to a crack that was normal to the loading direction and initiated from the edge of the hole progressing to the outer edges of the specimen. The [±45 °]4S specimens failed to support the load due to an internal crack that originated from the hole's edge and then traveled at an angle of about 42% to the direction of loading. The finite element method used to analytically model the failure of Gr/PEEK accurately modeled the response of the specimens tested experimentally. 相似文献
6.
Hawkins R.T. II Jones M.D. Pepper S.H. Goll J.H. Ravel M.K. 《IEEE transactions on instrumentation and measurement》1992,41(4):467-475
Deconvolution of measurement system effects from pulse response measurements is demonstrated to yield reproducible, accurate characterization of the impulse response (and vector frequency response) of a photodetector or photoreceiver, as well as the intensity waveform of an optical pulse. Calibration is based on a <3-ps FWHM (full width at half maximum) optical pulse and a 50-GHz 3-dB bandwidth electrical sampling system. Vector characterization of a photodetector/photoreceiver to >40 GHz and an optical pulse source to >30 GHz are demonstrated. Calibration and effects of noise are discussed 相似文献
7.
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
8.
9.
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
10.
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