全文获取类型
收费全文 | 1688篇 |
免费 | 40篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 50篇 |
综合类 | 20篇 |
化学工业 | 401篇 |
金属工艺 | 20篇 |
机械仪表 | 23篇 |
建筑科学 | 109篇 |
矿业工程 | 10篇 |
能源动力 | 32篇 |
轻工业 | 175篇 |
水利工程 | 20篇 |
石油天然气 | 18篇 |
无线电 | 128篇 |
一般工业技术 | 289篇 |
冶金工业 | 258篇 |
原子能技术 | 17篇 |
自动化技术 | 160篇 |
出版年
2023年 | 15篇 |
2021年 | 21篇 |
2020年 | 17篇 |
2019年 | 19篇 |
2018年 | 22篇 |
2016年 | 16篇 |
2015年 | 25篇 |
2014年 | 39篇 |
2013年 | 89篇 |
2012年 | 58篇 |
2011年 | 85篇 |
2010年 | 52篇 |
2009年 | 65篇 |
2008年 | 69篇 |
2007年 | 70篇 |
2006年 | 60篇 |
2005年 | 47篇 |
2004年 | 53篇 |
2003年 | 32篇 |
2002年 | 40篇 |
2001年 | 17篇 |
2000年 | 29篇 |
1999年 | 20篇 |
1998年 | 26篇 |
1997年 | 22篇 |
1996年 | 17篇 |
1995年 | 25篇 |
1994年 | 20篇 |
1993年 | 20篇 |
1992年 | 19篇 |
1991年 | 30篇 |
1990年 | 23篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 27篇 |
1984年 | 27篇 |
1983年 | 22篇 |
1982年 | 28篇 |
1981年 | 21篇 |
1980年 | 21篇 |
1979年 | 17篇 |
1978年 | 23篇 |
1975年 | 19篇 |
1974年 | 27篇 |
1973年 | 20篇 |
1972年 | 26篇 |
1970年 | 20篇 |
1968年 | 13篇 |
1967年 | 15篇 |
1966年 | 15篇 |
排序方式: 共有1730条查询结果,搜索用时 31 毫秒
71.
Reductive dehalogenation of tetrachloroethene (PCE), trichloroethene (TCE), cis-1,2-dichloroethene (DCE), and vinyl chloride (VC) was examined in four cultures containing Dehalococcoides-like microorganisms. Dechlorination and growth kinetics were compared using a Monod growth-rate model for multiple electron acceptor usage with competition. Included were the Victoria mixed culture containing Dehalococcoides species strain VS (from Victoria, TX), the mixed culture KB-1/VC (from southern Ontario), the Pinellas mixed culture (from Pinellas, FL), and D. ethenogenes strain 195. All cultures, with the exception of D. ethenogenes strain 195, grew with VC as catabolic electron acceptor. A dilution method was developed that allows a valid comparison to be made of dehalogenating kinetics between different mixed cultures. Using this procedure, maximum growth rates on VC were found to be similar for strain VS and KB-1/VC (0.42-0.49 +/- 0.02 d(-1)) but slower for the Pinellas culture (0.28 +/- 0.01 d(-1)). The 16S rRNA gene sequences were determined to ensure that no cross contamination between cultures had occurred. Following enrichment of the VC dechlorinating microorganisms on VC, the cultures were amended with DCE, TCE, or PCE. The three mixed cultures failed to dechlorinate PCE or did so very slowly. However, the dilution technique indicated that all experienced growth on TCE and DCE as well as on VC. Maximum growth rates on DCE alone were quite similar (0.43-0.46 d(-1)), while the Pinellas culture grew faster on TCE alone (0.49 d(-1)) than did the other two mixed cultures (0.33-0.35 d(-1)). Half-velocity and inhibition constants for growth on TCE were also determined for the three mixed cultures; both constants were found to be essentially equal and the same for the different cultures, varying between only 8.6 and 10.5 microM. The ability of the strain VS, KB-1/VC, and Pinellas cultures to utilize TCE rapidly with conversion to ethene is quite different from that of any other reported microorganism. It was separately confirmed with more traditional cell-counting techniques that strain VS coupled TCE, as well as DCE and VC, utilization with growth. This is the first report of an organism obtaining energy for growth through every step in the reduction of TCE to ethene. Also, as suggested by the dilution technique, the dehalogenating organisms in the KB-1/VC and Pinellas cultures appear to obtain growth from TCE utilization as well. Such ability to grow while dehalogenating TCE to ethene will be an important advantage for their use in bioaugmentation. 相似文献
72.
Hallstrom AP Stein PK Schneider R Hodges M Schmidt G Ulm K 《IEEE transactions on bio-medical engineering》2004,51(8):1414-1420
Decreased left ventricular ejection fraction is the most commonly used risk factor for identification of patients at high-risk for lethal ventricular arrhythmic events. Twenty-four-hour electrocardiographic (ECG) approaches to risk stratification include: counts of ventricular premature contractions (VPCs), measures of heart rate variability (HRV), and heart rate turbulence (HRT) which has two components, turbulence onset and turbulence slope (TS). Refinement of these ECG risk stratifiers could enhance their clinical utility. We explored the structural relationships between heart rate (HR) and HRV and HRT measures. Our goal was to separate out the component of these measures due to the underlying average heart rate (HR), thus potentially reducing the variability of the measures and increasing their power to stratify risk. We proposed re-scaling tachograms of heart-beat intervals so that the re-scaled tachogram has a HR of 75 (or equivalently an average interval of 800 ms) and calculating HRV and HRT from the rescaled time series. We also explored the relationship between the number of VPCs and HRT. We showed that TS is structurally related to the number of VPCs (and hence to the length of the ECG recording). We proposed an adjusted TS that is independent of the number of VPCs. We also addressed the ability of shorter ECG recording to estimate HRV and HRT measures. We evaluated standard and rescaled HRV and HRT measures using qualifying ambulatory ECG recordings from 744 patients in the Cardiac Arrhythmia Suppression Trial. We found that measures based on the rescaled tachogram had reduced variance (20% to 40%). Correlations between measures were also substantially reduced. We also found substantial circadian effects on some, but not all HRV indices, not explained by the circadian pattern in HR and possibly pointing to additional measures for risk prediction. In conclusion, we found that adjusting for HR and the number of VPCs in heart-beat related ambulatory ECG measures has the potential to significantly improve the power of these measures to risk stratify cardiac patients. 相似文献
73.
For a polydisperse nanoparticle ensemble the evaluation of time-resolved laser-induced incandescence (LII) measurements yields a weighted average value for the primary nanoparticle size. Although this value is sufficient for narrow size distributions, a comprehensive characterization of a particle-evolution process requires the reconstruction of the size distribution. An easy-to-use online approach is presented to evaluate the LII signal regarding higher moments of the distribution. One advantage of this approach is that the size distribution results in a deceleration of the LII signal decay with time after the laser pulse. Therefore LII signal-decay curves are evaluated in two different time intervals after the laser pulse, providing information about the desired distribution parameters that has been tested successfully with experimental curves taken in different soot-formation processes. 相似文献
74.
Rigidity, as measured by the paper-and-pencil water jar test and actual presence of the jars, were not found to be highly related. The paper-and-pencil version was found to elicit more behavior categorized as rigid. The results were interpreted as not favoring either measure as an adequate measure of rigidity, but of problem solving ability. From Psyc Abstracts 36:04:4CE91W. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
75.
The anodic behaviour of Ga(As1-xPx) in basic media and under illumination has been investigated by measuring the electrode characteristics and the interfacial capacity values. These measurements are interpreted using Gärtner's classical model. The diffusion length of minority carriers and the gap value have been calculated. It is necessary to assume a recombination on the surface to explain the variation to the photolyse current density with the potential. This process may be attributed to a centre for which it has been possible to evaluate the energy level. 相似文献
76.
Allum J. H. J. Tole John R. Weiss Alfred D. 《IEEE transactions on bio-medical engineering》1975,(3):196-202
A digital computer program, MITNYS-II, has been developed for on-line analysis of nystagmus which results from visual, vestibular or caloric stimulation. The program accepts sampled records of eye position and yields cumulative slow phase position, slow phase velocity, instantaneous fast phase frequency and other parameters in 25 ms. In this paper the algorithms by which fast phases are detected, and by which slow phase cumulative eye position is extrapolated across the fast phase interval are described. Extensive tests with vestibular, optokinetic and caloric nystagmus yield reliability figures of the order of 2% for false identification of fast phases and missed fast phases. MITNYS-II has been successfully employed to interpret clinical EOG records, examples of which are presented. 相似文献
77.
Alfred Hoffmann 《国际钢铁研究》1967,38(12):921-928
Untersuchung (röntgenographisch, mikroskopisch und mit der Mikrosonde) des Zerfalls von Wüstitmischkristallen mit Zusatz von Aluminium-, Silizium(IV)-, Phosphor(V)- oder Chrom(III)-oxyd nach isothermischem Halten swischen 200 und 650 °C. Einfluß der Temperatur, der Haltezeit und der Art des Zusatzoxydes auf den Wüstitzerfall. Erörterung und Deutung der Versuchsergebnisse über den Zerfallsablauf mit seinen verschiedenen Teilschritten. 相似文献
78.
Zugversuche an langen Proben aus Spannstahl 145/160 mit rd. 0,45% C, 1,5% Si, 0,6% Mn, 0,4% Cr und 0,15% Cu und Ermittlung der Oleichmaßdehnung unter der Höchstkraft und nach dem Bruch. Messung der Stauchung und Aufnahme der hoch- und niederfrequenten Stoßwellen beim Bruch. 相似文献
79.
We consider the problem of patrolling—i.e.
ongoing exploration of a network by
a decentralized group of simple memoryless robotic agents.
The model for the network is an undirected graph,
and our goal, beyond complete exploration, is to achieve close to uniform
frequency of traversal of the graphs edges.
A simple multi-agent exploration algorithm is presented and analyzed.
It is shown that a single agent following this procedure enters,
after a transient period, a periodic motion
which is an extended Eulerian cycle, during which all edges are
traversed an identical number of times.
We further prove that if the network is Eulerian,
a single agent goes into an Eulerian cycle within
2|E|D steps, |E| being the number of edges in the graph and D
being its diameter. For a team of k agents, we show that after at
most 2( 1 + 1/k) |E|D steps the numbers of
edge visits in the network
are balanced up to a factor of two. In addition, various
aspects of the algorithm are demonstrated by simulations. 相似文献
80.
CYTOCENTERING: a novel technique enabling automated cell-by-cell patch clamping with the CYTOPATCH chip 总被引:4,自引:0,他引:4
Automats for patch clamping suspended cells in whole-cell configuration must (1) bring isolated cells in contact with patch contacts, (2) form gigaseals, and (3) establish stable intracellular access that allows for high quality recording of ionic currents. Single openings in planar substrates seem to be intriguing simple solutions for these problems, but due to the low rate of formation of whole-cell configurations we discarded this approach. Single openings are not suited for both attracting cells to the opening by suction and forming gigaseals with subsequent membrane rupture. To settle the three tasks with a mechanical microstructure we developed the socalled CYTOCENTERING technique to apply to suspended cells the same operation sequence as in conventional patch clamping. With this method we immobilized selected cells from a flowing suspension on the tip of a patch pipette by suction with a success rate of 97% and formed gigaseals with a success rate of 68%. Subsequent whole-cell recordings and intracellular staining with Lucifer yellow proved the stable access to the cytoplasm. Currently, a chip with an embedded suction opening in glass surrounding the microstructured contact pipette is under development. The processing of this CYTOPATCH chip is compatible to large-volume production. The CYTOPATCH automat will allow for fully automated, parallel, and asynchronous whole-cell recordings. 相似文献