全文获取类型
收费全文 | 1523篇 |
免费 | 36篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 18篇 |
综合类 | 1篇 |
化学工业 | 238篇 |
金属工艺 | 74篇 |
机械仪表 | 19篇 |
建筑科学 | 66篇 |
能源动力 | 48篇 |
轻工业 | 168篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 147篇 |
一般工业技术 | 237篇 |
冶金工业 | 355篇 |
原子能技术 | 5篇 |
自动化技术 | 176篇 |
出版年
2023年 | 6篇 |
2022年 | 10篇 |
2021年 | 20篇 |
2020年 | 11篇 |
2019年 | 14篇 |
2018年 | 16篇 |
2017年 | 25篇 |
2016年 | 24篇 |
2015年 | 36篇 |
2014年 | 35篇 |
2013年 | 59篇 |
2012年 | 45篇 |
2011年 | 79篇 |
2010年 | 56篇 |
2009年 | 62篇 |
2008年 | 69篇 |
2007年 | 62篇 |
2006年 | 49篇 |
2005年 | 54篇 |
2004年 | 45篇 |
2003年 | 53篇 |
2002年 | 45篇 |
2001年 | 32篇 |
2000年 | 27篇 |
1999年 | 46篇 |
1998年 | 108篇 |
1997年 | 63篇 |
1996年 | 60篇 |
1995年 | 54篇 |
1994年 | 59篇 |
1993年 | 36篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 25篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 18篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1971年 | 3篇 |
排序方式: 共有1560条查询结果,搜索用时 31 毫秒
101.
Contrast agents in acute myocardial infarction 总被引:2,自引:0,他引:2
Hemmingsson A Bjerner T Ericsson A Johansson L Ahlström H 《Magma (New York, N.Y.)》2001,12(2-3):96-98
The experimental design in examination of acute myocardial infarctions should be valid in terms of flow, perfusion and re-flow
after intervention. The contrast agents concentration in experimental studies can be measured by microdialysis. We have assessed
the usefulness of different extracellular and blood pool contrast agents for visualization of the area at risk in coronary
artery occlusions. The double contrast technique, where Dy-DTPA-BMA was combined with Gd-DTPA-BMA yielded a superior infarct
visualization. Blood pool agents for example NC100/150 injection is also promising in first path myocardial perfusion imaging. 相似文献
102.
Zibar D. Johansson L. A. Chou H.-F. Ramaswamy A. Rodwell M. Bowers J. E. 《Photonics Technology Letters, IEEE》2007,19(9):686-688
A novel phase-locked coherent demodulator, based on a sampling phase-locked loop, is presented and investigated theoretically. The demodulator is capable of operating at high frequencies, by using optical sampling to downconvert the high-frequency input radio-frequency signal to the frequency range of the baseband loop. We develop a detailed theoretical model of the (sampling) phase-locked coherent demodulator and perform detailed numerical simulations. The simulation results show that the operation of the sampling demodulator resembles the operation of the baseband demodulator for very short optical pulses (<2 ps). Furthermore, we investigate how the signal-to-noise ratio of the demodulator is affected by timing and amplitude jitter of the pulsed optical source 相似文献
103.
Klamkin J. Ramaswamy A. Johansson L. A. Chou H.-F. Sysak M. N. Raring J. W. Parthasarathy N. DenBaars S. P. Bowers J. E. Coldren L. A. 《Photonics Technology Letters, IEEE》2007,19(3):149-151
Waveguide uni-traveling-carrier photodiodes (UTC-PDs) have been fabricated and tested. Output saturation currents greater than 40 mA at 1 GHz are demonstrated for a 10 mumtimes150mum photodiode (PD). The third-order intermodulation distortion is also measured and exhibits a third-order output intercept point of 43 dBm at 20 mA and 34 dBm at 40 mA for this same PD. UTC-PDs with geometries of 5 mumtimes100 mum and 10 mumtimes100 mum are also compared and it is shown that a wider waveguide PD has improved saturation characteristics due to the lower optical power density which reduces the saturation at the front end of the device 相似文献
104.
Rolf Johansson Michael Verhaegen Chun Tung Chou Anders Robertsson 《International journal of control》2013,86(10):988-995
This paper presents theory and algorithms for validation in system identification of state-space models from finite input-output sequences in a subspace model identification framework. Our formulation includes the problem of rank-deficient residual covariance matrices, a case which is encountered in applications with mixed stochastic-deterministic input-output properties as well as for cases where outputs are linearly dependent. Similar to the case of prediction-error identification, it is shown that the resulting model can be decomposed into an input-output model and a stochastic innovations model. Using the Riccati equation, we have designed a procedure to provide a reduced-order stochastic model that is minimal with respect to system order as well as the number of stochastic inputs thereby avoiding several problems appearing in standard application of stochastic realization to the model validation problem. 相似文献
105.
Stacy M. Trey Mikael Lundström Daniel Ståhlberg Mats Johansson 《Progress in Organic Coatings》2009,64(2-3):238-246
Sheet molded compound (SMC) is a highly filled, glass fiber reinforced, thermoset material used in trim and body panel automotive parts. When SMC-substrates are coated with conventional thermally cured paints, inherent porosity and entrapped volatiles of the substrate result in popping (“paint pops”) defects. UV-curable primers (UVP) provide an order of magnitude reduction of paint defects in SMC coatings, but typically have poor adhesion. Mercaptan polymers have a long history, dating back to 1928, of use in adhesives and sealant applications. The present study investigates a series of UVPs, showing the effect of resin functionality and thiol functional additive content on the adhesion of the coatings to SMC substrates. The SMC formulation is also considered when evaluating UVP adhesion, regarding variables such as surface chemistry, morphology, and surface area. The present study brings to light how adhesion of acrylate UVP can be enhanced with mercaptan moieties in additive amounts. The effect is most apparent on SMC substrates that have been treated to expose inorganic fillers as opposed to untreated surfaces of polyester. Additionally annealing the films boosts adhesion, but only in thiol containing formulations. This is a result of the decrease in Tgs and modulus of the films with the addition of mercaptans, thus providing better contact with the substrate in comparison to non-thiol containing formulations. 相似文献
106.
A new method for the detection of phospholipid hydroperoxides in the low nanomolar range has been developed by using a high
performance liquid chromatography system combined with a post-column reaction. The detection is based on the oxidation of
Fe(II) to Fe(III) by hydroperoxides and the subsequent formation of an ironthiocyanate complex, which can be determined spectrophotometrically
at 505 nm. By this method it is possible to separate and quantitate phosphatidylethanolamine hydroperoxide and phosphatidylcholine
hydroperoxide formed in erythrocyte ghost membranes during photo-oxidation. 相似文献
107.
Lasers are useful in many applications in medicine and biology. Historically, most laser use has involved heat generated in the interaction of the laser beam with the tissue. Today, however, the spectroscopic aspects of this laser use are playing a more dominant role in a number of applications. In this two-part series, Sune Svanberg and co-workers present illustrations of emerging clinical applications from cooperative work performed by the Lund Institute of Technology and the Lund University Hospital. Part I includes a survey of laser techniques for atomic and molecular analyses of samples of medical interest, spectroscopic analysis of the laser-induced plasma obtained when a high-power pulsed laser beam interacts with tissue, and the use of tumor-seeking agents in combination with laser radiation to provide new possibilities for malignant tumor detection and treatment. Part II, which will appear in the January 1, 1990, issue, describes the use of laser-induced fluorescence for tumor and plaque diagnostics. Different lasers have been used, and research efforts increasingly are being focused on excimer lasers and lasers in the IR region for the ablation of atherosclerotic plaques, cell layer by cell layer. 相似文献
108.
Anders Olsson Jan Oscarsson Erik Serrano Bo Källsner Marie Johansson Bertil Enquist 《Holz als Roh- und Werkstoff》2013,71(3):319-333
Machine strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and bending strength. However, such relationships applied on the market today are rather poor. In this paper, new IPs and a new grading method resulting in more precise strength predictions are presented. The local fibre orientation on face and edge surfaces of wooden boards was identified using high resolution laser scanning. In combination with knowledge regarding basic wood material properties for each investigated board, the grain angle information enabled a calculation of the variation of the local MOE in the longitudinal direction of the boards. By integration over cross-sections along the board, an edgewise bending stiffness profile and a longitudinal stiffness profile, respectively, were calculated. A new IP was defined as the lowest bending stiffness determined along the board. For a sample of 105 boards of Norway spruce of dimension 45 × 145 × 3,600 mm³, a coefficient of determination as high as 0.68–0.71 was achieved between this new IP and bending strength. For the same sample, the coefficient of determination between global MOE, based on the first longitudinal resonance frequency and the board density, and strength was only 0.59. Furthermore, it is shown that improved accuracy when determining the stiffness profiles of boards will lead to even better predictions of bending strength. The results thus motivate both an industrial implementation of the suggested method and further research aiming at more accurately determined board stiffness profiles. 相似文献
109.
110.
Abstract Market-based instruments such as fees or tradable permits can be used to simultaneously regulate point and nonpoint sources of pollution discharge into a river. However, sources of pollution discharge often have more information about their own costs of pollution abatement than do regulators. This information asymmetry may lead to strategic behavior, which can lead to different outcomes under different policies. This paper estimates a Nash payoff of a two-period strategic game using econometrically estimated abatement costs for point and nonpoint source phosphorus discharges in the Minnesota River Basin. Results show that when dischargers of pollutants are strategic, discharge permits may yield lower deadweight losses than discharge fees. 相似文献