全文获取类型
收费全文 | 2515篇 |
免费 | 152篇 |
专业分类
电工技术 | 16篇 |
综合类 | 6篇 |
化学工业 | 656篇 |
金属工艺 | 21篇 |
机械仪表 | 33篇 |
建筑科学 | 155篇 |
矿业工程 | 2篇 |
能源动力 | 46篇 |
轻工业 | 362篇 |
水利工程 | 28篇 |
石油天然气 | 7篇 |
无线电 | 176篇 |
一般工业技术 | 486篇 |
冶金工业 | 373篇 |
原子能技术 | 9篇 |
自动化技术 | 291篇 |
出版年
2024年 | 4篇 |
2023年 | 33篇 |
2022年 | 85篇 |
2021年 | 111篇 |
2020年 | 54篇 |
2019年 | 71篇 |
2018年 | 71篇 |
2017年 | 65篇 |
2016年 | 72篇 |
2015年 | 63篇 |
2014年 | 114篇 |
2013年 | 166篇 |
2012年 | 138篇 |
2011年 | 213篇 |
2010年 | 151篇 |
2009年 | 108篇 |
2008年 | 126篇 |
2007年 | 121篇 |
2006年 | 93篇 |
2005年 | 97篇 |
2004年 | 78篇 |
2003年 | 65篇 |
2002年 | 46篇 |
2001年 | 39篇 |
2000年 | 41篇 |
1999年 | 30篇 |
1998年 | 90篇 |
1997年 | 66篇 |
1996年 | 43篇 |
1995年 | 27篇 |
1994年 | 19篇 |
1993年 | 23篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 14篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1977年 | 6篇 |
1976年 | 12篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1972年 | 5篇 |
排序方式: 共有2667条查询结果,搜索用时 9 毫秒
1.
2.
Corazza G.E. Ferrari G. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2002,48(11):3003-3008
New bounds are proposed for the Marcum Q-function, which is defined by an integral expression where the 0th-order modified Bessel function appears. The proposed bounds are derived by suitable approximations of the 0th-order modified Bessel function in the integration region of the Marcum Q-function. They prove to be very tight and outperform bounds previously proposed in the literature. In particular, the proposed bounds are noticeably good for large values of the parameters of the Marcum Q-function, where previously introduced bounds fail and where exact computation of the function becomes critical due to numerical problems 相似文献
3.
Thermal conductivity of apple and potato samples was measured by means of a specifically designed apparatus based on Fitch's method. The thermal conductivity was determined at various moisture contents at the sample mean temperature of 30 °C. As expected the conductivity decreases with the decrease in moisture content. Thermal conductivity data were correlated with moisture content using a straight line. 相似文献
4.
Functional adhesion of blood and marrow leukemic cells from 14 acute myeloid leukemia patients presenting with hyperleukocytosis was evaluated by performing cytoadhesion assays on purified (extracellular matrix proteins) and non-purified supports (MRC5 fibroblastic cell line). Results, in 30-min chromium release assay, show a mean +/- S.D. adhesion to fibronectin, collagen, and laminin respectively of 30 +/- 17%, 20 +/- 13%, 25 +/- 17% for blood leukemic cells and 18 +/- 11%, 11 +/- 10%, 11 +/- 8% for marrow leukemic cells. These differences between blood and marrow cells were statistically significant (respectively P = 0.005, P = 0.01 and P = 0.002), while no difference was noted regarding adhesion to non-purified supports. The higher adhesion of blood blast cells to purified supports was observed regardless of CD34 expression. No significant difference was observed in the expression of cell surface VLA-molecules (CD29, CD49b, CD49d, CD49e, CD49f) between blood and marrow blast cells. The addition of GM-CSF or G-CSF induced increased adhesion of marrow blasts and decreased adhesion of blood blasts leading to a loss of the difference between blood and marrow cells. In a 60-min chromium release assay, marrow blasts adhered even more than blood leukemic cells to fibronectin. In contrast, marrow blasts from 'aleukemic' acute myeloid leukemia patients did not show any modification regarding their adhesion to extracellular matrix proteins when co-cultured with growth factors. 相似文献
5.
6.
Peter Eaton Andrea Ragusa Caroline Clavel Cristina T Rojas Paul Graham Raúl V Durán Soledad Penadés 《IEEE transactions on nanobioscience》2007,6(4):309-318
Glyconanoparticles which present carbohydrate and amino groups motifs at their surface were produced. These particles were highly stable and soluble in aqueous solutions. The presence of the carbohydrate groups also allowed the inclusion of more strongly binding groups, without affecting solubility. The binding of a model DNA, plasmid by these nanoparticles was studied by atomic force microscopy, transmission electron microscopy, and gel electrophoresis. Significant differences between the nanoparticles based on their affinities for the DNA were found, with implications for their potential use as nonviral gene delivery agents. 相似文献
7.
F. Ferrari M. Bertoni S. Rossi M. C. Bonferoni C. Caramella M. J. Waring M. E. Aulton 《Drug development and industrial pharmacy》1996,22(12):1223-1230
Hydration is believed to modify the mechanical properties (resistance to stress) and the rheological (viscoelastic) properties of hydrocolloid dressings. Rheomechanical properties in turn influence adhesional properties. In this work the relationships between the degree of hydration and the rheomechanical and the adhesive properties of two different commercial dressings (regular and nondispersive) were investigated. The two dressings showed different hydration characteristics. The regular dressing takes up water rapidly and tends to reach saturation after 12 hr. As the dressing swells and loses its integrity there is an accompanying reduction of both rheomechanical and adhesive properties. The nondispersive dressing exhibits a linear water uptake profile over extended periods of hydration up to 4 days. It does not swell and its rheomechanical and adhesive properties remain unchanged after hydration, The comparative evaluation of the results obtained with the various methods points to the relevance of mechanical and viscoelastic properties to the functionality assessment of dressings. 相似文献
8.
The fluctuations observed by recording the picosecond pulses of a mode-locked laser with a synchroscan streak camera are due to the laser jitter and to the variations of the zero crossing of the synchronization. By means of a simple model, it is shown that the dispersions measured when the synchronization is generated from the mode-locker oscillator reflect the instantaneous time phase fluctuations of this oscillator. From the study of the experimental recordings with methods of time series analysis it results that the phase noise of the electronic oscillator is consistent with an underlying low-dimensional strange attractor. 相似文献
9.
R Pérez Ferrari L Lambra?o R Aranda L Ferrabone 《Canadian Metallurgical Quarterly》1993,18(3):229-232
We studied the incidence of infection with Helicobacter pylori in Panamanians with chronic dyspepsia, gastric or duodenal ulcer, gastritis or gastric cancer. The histopathology was positive in 54 (81%) of 66 patients; the urea test was positive in 52 (82.5%) of 63 cases; the impromptu was positive in 51 (79.6) of 64 patients; the endoscopic examination was positive in 64 (82.9%) of 77 examinations. 相似文献
10.
Ferrari A. Ghislotti G. Balsamo S. Spano V. Trezzi F. 《Lightwave Technology, Journal of》2002,20(3):515-518
The behavior of fiber Bragg grating (FBG)-stabilized 980-nm pump lasers is experimentally and theoretically investigated. The subkilohertz noise in the emitted power is related to the coexistence and oscillation between coherence collapsed state and narrow linewidth single-mode (SM) operation. These findings are theoretically discussed by using a multimode time-domain model that accounts for spatial harmonics and includes nonlinear gain. One additional result is an indication that kinks in the L-I curve can be explained by nonlinear mode competition 相似文献