全文获取类型
收费全文 | 3025篇 |
免费 | 221篇 |
国内免费 | 4篇 |
学科分类
工业技术 | 3250篇 |
出版年
2023年 | 29篇 |
2022年 | 18篇 |
2021年 | 133篇 |
2020年 | 76篇 |
2019年 | 90篇 |
2018年 | 99篇 |
2017年 | 92篇 |
2016年 | 143篇 |
2015年 | 113篇 |
2014年 | 147篇 |
2013年 | 222篇 |
2012年 | 203篇 |
2011年 | 232篇 |
2010年 | 194篇 |
2009年 | 190篇 |
2008年 | 179篇 |
2007年 | 168篇 |
2006年 | 119篇 |
2005年 | 94篇 |
2004年 | 118篇 |
2003年 | 98篇 |
2002年 | 62篇 |
2001年 | 48篇 |
2000年 | 39篇 |
1999年 | 32篇 |
1998年 | 31篇 |
1997年 | 18篇 |
1996年 | 31篇 |
1995年 | 29篇 |
1994年 | 24篇 |
1993年 | 21篇 |
1992年 | 20篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 11篇 |
1987年 | 12篇 |
1986年 | 5篇 |
1985年 | 15篇 |
1984年 | 17篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有3250条查询结果,搜索用时 9 毫秒
101.
Emanuele Moretti Paolo Peretti Lorenzo Palestini Stefania Cecchi Francesco Piazza 《Signal, Image and Video Processing》2011,5(2):185-190
In implementing digital signal processing (DSP) algorithms for audio real-time applications, one is frequently faced with
problems regarding incompatibilities between the hardware buffer length (the internal buffer of a professional sound card)
and the software buffer size imposed by the underlying algorithm (due to i.e. multirate or FFT constraints). This mismatch
is solved by proper frame size conversion algorithms which inevitably introduce delay. In this context, this paper presents
a buffering scheme together with a theoretical proof of the minimum delay property shown by it. Some examples derived from
frequently encountered issues in DSP applications are reported. 相似文献
102.
Blade vibration reduction is an important task in high performance turbo machinery for power generation, in order to avoid the risk of blade failure due to the overcoming of fatigue limit. A possible way to obtain this result is a contact related phenomenon, i.e. by physically limiting the vibration amplitude on the blade tip leaving a small gap between the shrouds of adjacent blades. When the relative displacement between adjacent blades exceeds the gap, in a certain vibration mode of the blade row, a contact occurs between the shrouds, the relative motion is restricted and energy is dissipated by friction and impact during the contact. This is called the snubbing mechanism.In this paper, an original simplified model of bladed disks, in which the snubbing mechanism can occur, is presented and numerical integration in time domain furnishes the time histories of the vibrations of the blades. The level of vibration reduction is then evaluated in some different modes that could be excited for instance by the fluid flow. It is also shown that unlucky combinations of system and excitation parameters can effect also a certain magnification instead of a reduction of the vibration amplitudes.Experimental results on single blade and blade groups of a steam turbine are used to tune the parameters of the system. 相似文献
103.
Lourdes Vázquez-Gómez Enrico Verlato Sandro Cattarin Nicola Comisso Paolo Guerriero Marco Musiani 《Electrochimica acta》2011,(5):2237
Electrocatalysts for methanol oxidation were prepared through a two stage deposition process: porous cobalt layers were deposited, by cathodic reduction of Co2+ ions, and then modified by spontaneous deposition of Pd. A basic sulphate solution and a mildly acid chloride solution were compared as media for the electrodeposition of Co. Deposits with the highest surface roughness were obtained in the chloride solution, at large current densities. Pd was deposited onto the Co porous layers by immersing them in acid deaerated PdCl2 solutions, at open circuit. The Pd loading and the Pd surface area were estimated by UV–visible spectroscopy and by cyclic voltammetry, respectively. The Pd-modified Co electrodes were tested as anodes for methanol oxidation and compared to the similarly prepared Pd-modified Ni electrodes. The former exhibited better stability of performance and higher methanol oxidation peak currents per unit Pd mass, ca. 200 A g−1. 相似文献
104.
105.
The catalytic dehydration of fructose (FRU) to 5-hydroxymethylfurfural (HMF) usually runs with the formation of several side products. Among these, levulinic acid (LA) is often reported as the product of a consecutive reaction of HMF re-hydration. In this work, side reactions of the dehydration of FRU performed in very green conditions (water as solvent and niobic acid as solid catalyst) are taken into account. Experimental evidences are given that, in the used conditions: i) HMF is a final stable product, ii) no formation of LA, either deriving from a consecutive reaction of HMF or directly from FRU transformation, was observed, and iii) LA does not react to give condensation products with any other chemical species present in the reaction mixture. 相似文献
106.
Hierarchically Structured Magnetic Nanoconstructs with Enhanced Relaxivity and Cooperative Tumor Accumulation 下载免费PDF全文
Ayrat Gizzatov Jaehong Key Santosh Aryal Jeyarama Ananta Antonio Cervadoro Anna Lisa Palange Matteo Fasano Cinzia Stigliano Meng Zhong Daniele Di Mascolo Adem Guven Eliodoro Chiavazzo Pietro Asinari Xuewu Liu Mauro Ferrari Lon J. Wilson Paolo Decuzzi 《Advanced functional materials》2014,24(29):4584-4594
Iron oxide nanoparticles are formidable multifunctional systems capable of contrast enhancement in magnetic resonance imaging, guidance under remote fields, heat generation, and biodegradation. Yet, this potential is underutilized in that each function manifests at different nanoparticle sizes. Here, sub‐micrometer discoidal magnetic nanoconstructs are realized by confining 5 nm ultra‐small super‐paramagnetic iron oxide nanoparticles (USPIOs) within two different mesoporous structures, made out of silicon and polymers. These nanoconstructs exhibit transversal relaxivities up to ≈10 times (r 2 ≈ 835 mm ?1 s?1) higher than conventional USPIOs and, under external magnetic fields, collectively cooperate to amplify tumor accumulation. The boost in r 2 relaxivity arises from the formation of mesoscopic USPIO clusters within the porous matrix, inducing a local reduction in water molecule mobility as demonstrated via molecular dynamics simulations. The cooperative accumulation under static magnetic field derives from the large amount of iron that can be loaded per nanoconstuct (up to ≈65 fg) and the consequential generation of significant inter‐particle magnetic dipole interactions. In tumor bearing mice, the silicon‐based nanoconstructs provide MRI contrast enhancement at much smaller doses of iron (≈0.5 mg of Fe kg?1 animal) as compared to current practice. 相似文献
107.
Benedetto Bozzini Amilcare Barca Francesco Bogani Marco Boniardi Paolo Carlino Claudio Mele Tiziano Verri Alessandro Romano 《Journal of materials science. Materials in medicine》2014,25(6):1425-1434
In this paper we describe the one-pot fabrication of hydroxyapatite (HA)-heparin composites by electrodeposition onto Ti substrates and their characterisation in terms of structure, morphology, heparin content and bioactivity. HA coatings are well known and widely applied osteointegration enhancers, but post-implant healing rate in dental applications is still suboptimal: e.g. coagulation control plays a key role and the incorporation of an anticoagulant is considered a highly desirable option. In this study, we have developed an improved, simple and robust growth procedure for single-phase, pure HA-heparin films of thickness 1/3 μm. HA-heparin, forming nanowires, has the ideal morphology for bone mineralisation. Staining assays revealed homogeneous incorporation of sizable amounts of heparin in the composite films. The bioactivities of the HA and HA-heparin coatings on Ti were compared by HeLa cell proliferation/viability tests and found to be enhanced by the presence of the anticoagulant. 相似文献
108.
Andrew J. Coughlin Jeyarama S. Ananta Nanfu Deng Irina V. Larina Paolo Decuzzi Jennifer L. West 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(3):556-565
Multimodal imaging offers the potential to improve diagnosis and enhance the specificity of photothermal cancer therapy. Toward this goal, gadolinium‐conjugated gold nanoshells are engineered and it is demonstrated that they enhance contrast for magnetic resonance imaging, X‐ray, optical coherence tomography, reflectance confocal microscopy, and two‐photon luminescence. Additionally, these particles effectively convert near‐infrared light to heat, which can be used to ablate cancer cells. Ultimately, these studies demonstrate the potential of gadolinium‐nanoshells for image‐guided photothermal ablation. 相似文献
109.
Duan Li Elisângela Guzi de Moraes Peng Guo Ji Zou Junzhan Zhang Paolo Colombo 《Science and Technology of Advanced Materials》2014,15(4)
Silicon nitride foams were prepared by direct foaming and subsequent rapid sintering at 1600 °C. The intense thermal radiation generated under the pressureless spark plasma sintering condition facilitated necking of Si3N4 grains. The prepared foams possessed a porosity of ~80 vol% and a compressive strength of ~10 MPa, which required only ~30 min for the entire sintering processes. Rapid growth of one-dimensional SiC nanowires from the cell walls was also observed. Thermodynamic calculations indicated that the vapor–liquid–solid model is applicable to the formation of SiC nanowires under vacuum. 相似文献
110.
Giorgina Barbara Piccoli Gabriella Guzzo Federica Neve Vigotti Irene Capizzi Roberta Clari Stefania Scognamiglio Valentina Consiglio Emiliano Aroasio Silvana Gonella Andrea Veltri Paolo Avagnina 《Hemodialysis international. International Symposium on Home Hemodialysis》2014,18(3):590-595
Renal function recovery (RFR), defined as the discontinuation of dialysis after 3 months of replacement therapy, is reported in about 1% of chronic dialysis patients. The role of personalized, intensive dialysis schedules and of resuming low‐protein diets has not been studied to date. This report describes three patients with RFR who were recently treated at a new dialysis unit set up to offer intensive hemodialysis. All three patients were females, aged 73, 75, and 78 years. Kidney disease included vascular‐cholesterol emboli, diabetic nephropathy and vascular and dysmetabolic disease. At time of RFR, the patients had been dialysis‐dependent from 3 months to 1 year. Dialysis was started with different schedules and was progressively discontinued with a “decremental” policy, progressively decreasing number and duration of the sessions. A moderately restricted low‐protein diet (proteins 0.6 g/kg/day) was started immediately after dialysis discontinuation. The most recent update showed that two patients are well off dialysis for 5 and 6 months; the diabetic patient died (sudden death) 3 months after dialysis discontinuation. Within the limits of small numbers, our case series may suggest a role for personalized dialysis treatments and for including low‐protein diets in the therapy, in enhancing long‐term RFR in elderly dialysis patients. 相似文献