全文获取类型
收费全文 | 18678篇 |
免费 | 740篇 |
国内免费 | 44篇 |
专业分类
电工技术 | 228篇 |
综合类 | 24篇 |
化学工业 | 3570篇 |
金属工艺 | 466篇 |
机械仪表 | 396篇 |
建筑科学 | 948篇 |
矿业工程 | 108篇 |
能源动力 | 600篇 |
轻工业 | 1616篇 |
水利工程 | 171篇 |
石油天然气 | 63篇 |
无线电 | 1442篇 |
一般工业技术 | 3358篇 |
冶金工业 | 3426篇 |
原子能技术 | 116篇 |
自动化技术 | 2930篇 |
出版年
2023年 | 118篇 |
2021年 | 317篇 |
2020年 | 234篇 |
2019年 | 270篇 |
2018年 | 368篇 |
2017年 | 378篇 |
2016年 | 413篇 |
2015年 | 338篇 |
2014年 | 513篇 |
2013年 | 1219篇 |
2012年 | 825篇 |
2011年 | 1166篇 |
2010年 | 800篇 |
2009年 | 829篇 |
2008年 | 930篇 |
2007年 | 871篇 |
2006年 | 759篇 |
2005年 | 743篇 |
2004年 | 594篇 |
2003年 | 541篇 |
2002年 | 526篇 |
2001年 | 333篇 |
2000年 | 303篇 |
1999年 | 329篇 |
1998年 | 356篇 |
1997年 | 298篇 |
1996年 | 295篇 |
1995年 | 290篇 |
1994年 | 281篇 |
1993年 | 251篇 |
1992年 | 254篇 |
1991年 | 154篇 |
1990年 | 231篇 |
1989年 | 198篇 |
1988年 | 166篇 |
1987年 | 165篇 |
1986年 | 155篇 |
1985年 | 187篇 |
1984年 | 197篇 |
1983年 | 162篇 |
1982年 | 170篇 |
1981年 | 168篇 |
1980年 | 142篇 |
1979年 | 163篇 |
1978年 | 122篇 |
1977年 | 120篇 |
1976年 | 162篇 |
1975年 | 124篇 |
1974年 | 105篇 |
1973年 | 108篇 |
排序方式: 共有10000条查询结果,搜索用时 672 毫秒
991.
The electrokinetic chromatographic separation of a series of inorganic and organic anions was achieved by utilizing an electrolyte system comprising a cationic soluble polymer (poly(diallydimethylammonium chloride, PDDAC) and a neutral beta-cyclodextrin (beta-CD) as pseudostationary phases. The separation mechanism was a combination of electrophoresis, ion-exchange (IE) interactions with PDDAC, and hydrophobic interactions with beta-CD. The extent of each chromatographic interaction was independently variable, allowing for control of the separation selectivity of the system. IE interactions could be varied by changing either the PDDAC concentration or the concentration of a competing ion (e.g., chloride) in the BGE, while the hydrophobic interactions could be varied by changing the concentration of beta-CD. The separation system was very robust, with the reproducibility of the migration times being <0.7% RSD. A mathematical model that predicted the mobilities of analytes under varying experimental conditions was derived and was shown to give good correlation (r2 = 0.9804) between predicted and experimental migration times. Parameters derived from the model were in good agreement with the ion-exchange and hydrophobic characteristics of the analytes. The model was also applied successfully to the optimization of conditions for the separation of a mixture of analytes or for conditions under which particular analytes migrated in a desired order. That is, the opportunity to tune the separation selectivity has been demonstrated. 相似文献
992.
The design and performance of an easily constructed spectroelectrochemical cell suitable for batch and flow injection measurements are described. The cell is fabricated from a commercially available 5-mm quartz cuvette and employs 60 ppi reticulated vitreous carbon as the working electrode, resulting in a reasonable compromise between optical sensitivity and thin-layer electrochemical behavior. The spectroelectrochemical traits of the cell in both batch and flow modes were evaluated using aqueous ferricyanide and compare favorably to those reported previously for similar cells. 相似文献
993.
Two new applications using multiple ion isolations in the cell of a Fourier transform-ion cyclotron resonance mass spectrometer equipped with an electrospray ionization source are described. A procedure that uses multiple ion isolations of an analyte and calibrants for internal calibration at each stage in a MSn experiment, under high-resolution exact-mass conditions, for structural characterization/elucidation of angiotensin I and rapamycin is illustrated. Fragment ion mass accuracies < 1.0 ppm are demonstrated and routinely achieved. Purification of a mixture is illustrated by isolating multiple charge states of a protein-drug complex from residual protein for further MSn studies to elucidate the site of covalent drug bonding using IRMPD for a mixture of epidermal growth factor receptor (EGFr) protein and EGFr-drug complex. The procedure developed for multiple ion isolations is referred to as multi-CHEF, multiple correlated harmonic excitation fields, in which tailored waveforms are used to notch out multiple mass regions of a spectrum with minimal off-resonance excitation. 相似文献
994.
A new software package, Virtual Column 2, is described for the simulation and optimization of the separation of inorganic anions by ion chromatography (IC). The software uses a limited amount of experimental retention data acquired according to a correct experimental design to predict retention times for analytes over a designated search area of eluent compositions. The experimental retention data are used to solve a new retention model, called the linear solvent strength model, empirical approach (LSSM-EA), which then enables prediction of retention times for all eluent compositions in the search area. The theoretical development of LSSM-EA and the processes used for solving the equations are discussed. Virtual Column 2 can be used for eluents containing one or two competing ions, and the software contains retention databases for up to 33 analytes on the Dionex AS9A-HC, AS4A-SC, and AS14A analytical columns with carbonate-bicarbonate eluents and the Dionex AS10, AS15, and AS16 analytical columns with hydroxide eluents (results for the AS10 and AS15 columns are not discussed in the present study). Virtual Column 2 has been evaluated extensively and is shown to give predicted retention times that in most cases agree with experimentally determined data to within 5%. The software has uses in practical IC method development, education and training in IC, and refinement of existing IC methodology. A free version of this program is available by download at www.virtualcolumn.com. 相似文献
995.
Kaspirzhny AV Gogan P Horcholle-Bossavit G Tyc-Dumont S 《Network (Bristol, England)》2002,13(3):357-380
For technical, instrumental and operator-related reasons, three-dimensional reconstructions of neurons obtained from intracellularly stained neuronal pieces scattered in serial sections are blurred by some morphological noise. This noise may strongly invalidate conclusions drawn from models built using the three-dimensional reconstructions and it must be taken into account when retrieving digitized neurons from available databases. We analyse the main generating sources of the noise and its consequences for the 'quality' of the data. We provide tools for detecting and evaluating the noise in any database providing sufficient information is given in the database. We propose a unified format for submitting data and a new neuron viewer/editor to analyse the digitized neurons with our tools. 相似文献
996.
Authors Index
Author Index, Volume 8 (2002) 相似文献997.
998.
Past, Present, and Future 总被引:9,自引:0,他引:9
Paul Gray 《Information Systems Management》2006,23(1):90-93
Thomas L. Friedman. the World Is Flat: A Brief History of the Twenty-First Century. N ew York: Farrar, Straus and Giroux, 2005, 488 pp.
Nicholas G. Carr. Does IT Matter? Information Technology and the Corrosion of Competitive Advantage. Boston: Harvard Business School Press, 2004, 193 pp.
John Hagel III and John Seely Brown. the Only Sustainable Edge: Why Business Strategy Depends on Productive Friction and Dynamic Specialization. Boston: Harvard Business School Press, 2005, 218 pp.
John Markoff. What the Dormouse Said. New York: Viking, 2005, 301 pp. 相似文献
Nicholas G. Carr. Does IT Matter? Information Technology and the Corrosion of Competitive Advantage. Boston: Harvard Business School Press, 2004, 193 pp.
John Hagel III and John Seely Brown. the Only Sustainable Edge: Why Business Strategy Depends on Productive Friction and Dynamic Specialization. Boston: Harvard Business School Press, 2005, 218 pp.
John Markoff. What the Dormouse Said. New York: Viking, 2005, 301 pp. 相似文献
999.
Simulation motion of Virtual Reality (VR) objects and humans has experienced important developments in the last decade. However,
realistic virtual human animation generation remains a major challenge, even if applications are numerous, from VR games to
medical training. This paper proposes different methods for animating virtual humans, including blending simultaneous animations
of various temporal relations with multiple animation channels, minimal visemes for lip synchronisation, and space sites of
virtual human and 3D object models for object grasping and manipulation. We present our work in our natural language visualisation
(animation) system, CONFUCIUS, and describe how the proposed approaches are employed in CONFUCIUS’ animation engine. 相似文献
1000.
Lin Ming-Tzer El-Deiry Paul Chromik Richard R. Barbosa Nicholas Brown Walter L. Delph Terry J. Vinci Richard P. 《Microsystem Technologies》2006,12(10):1045-1051
A specially designed microtensile apparatus capable of carrying out a series of tests on microscale thin films for microelectromechanical system (MEMS) applications at room temperature and at temperature up to 400°C has been developed and tested, and is described here. Several MEMS-applicable thin films were measured with it, including thermally grown silicon dioxide, gold, and gold–vanadium. The silicon dioxide was tested at room temperature. Gold and gold–vanadium films were tested at room temperature and at 200 and 400°C. Examples of these results are presented.
相似文献