全文获取类型
收费全文 | 874篇 |
免费 | 40篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 222篇 |
金属工艺 | 14篇 |
机械仪表 | 26篇 |
建筑科学 | 29篇 |
能源动力 | 24篇 |
轻工业 | 50篇 |
水利工程 | 2篇 |
石油天然气 | 4篇 |
无线电 | 56篇 |
一般工业技术 | 112篇 |
冶金工业 | 227篇 |
原子能技术 | 6篇 |
自动化技术 | 132篇 |
出版年
2023年 | 11篇 |
2022年 | 36篇 |
2021年 | 52篇 |
2020年 | 19篇 |
2019年 | 17篇 |
2018年 | 18篇 |
2017年 | 21篇 |
2016年 | 30篇 |
2015年 | 24篇 |
2014年 | 35篇 |
2013年 | 36篇 |
2012年 | 30篇 |
2011年 | 39篇 |
2010年 | 22篇 |
2009年 | 39篇 |
2008年 | 27篇 |
2007年 | 25篇 |
2006年 | 25篇 |
2005年 | 26篇 |
2004年 | 19篇 |
2003年 | 15篇 |
2002年 | 14篇 |
2001年 | 14篇 |
2000年 | 18篇 |
1999年 | 18篇 |
1998年 | 49篇 |
1997年 | 23篇 |
1996年 | 30篇 |
1995年 | 16篇 |
1994年 | 19篇 |
1993年 | 12篇 |
1992年 | 4篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 16篇 |
1975年 | 5篇 |
1974年 | 3篇 |
排序方式: 共有914条查询结果,搜索用时 688 毫秒
92.
OBJECTIVE: To evaluate the association between admission serum concentrations of the actin-scavenger, Gc-globulin, and the subsequent development of multiple organ failure in patients with fulminant hepatic failure. DESIGN: Retrospective study. SETTING: A hepatologic intensive care unit. PATIENTS: Seventy-nine patients with hepatic encephalopathy grade 3 or 4. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Serum admission concentrations of both total and nonactin-complexed (free) Gc-globulin were determined. The development of cardiovascular failure, renal failure, pulmonary failure, intracranial hypertension, and infections were recorded in each patient. Both total and free Gc-globulin values were significantly lower in the patients, compared with normal controls. The Gc-globulin values were significantly reduced in patients who subsequently developed cardiovascular failure (p < .01), intracranial hypertension (p < .001), and infections (p < .001), compared with those patients who did not. No differences were found between patients with and without pulmonary or renal failure. Patients with total Gc-globulin values in the lowest quintile had on average 2.6 organ failures, whereas patients with Gc-globulin concentrations in the highest quintile had 0.9 organ failures. The corresponding figures for the lowest and highest quintiles of free Gc-globulin were 3.0 and 1.1 organ failures, respectively. Both total and free Gc-globulin were inversely correlated to the number of organ failures (p < .005 in both cases). Patients with multiple organ failure (> or = 2 organ failures) had significantly reduced Gc-globulin values compared with patients without multiple organ failure (p < .0001). CONCLUSIONS: In patients with fulminant hepatic failure, the lowest admission Gc-globulin concentrations were associated with the subsequent development of cardiovascular failure, intracranial hypertension, and infections. Lack of Gc-globulin correlated significantly with the development of multiple organ failure and may be pathogenetically involved in this condition. 相似文献
93.
94.
Shang H. Okorn-Schimdt H. Ott J. Kozlowski P. Steen S. Jones E.C. Wong H.-S.P. Hanesch W. 《Electron Device Letters, IEEE》2003,24(4):242-244
In this letter, we report germanium (Ge) p-channel MOSFETs with a thin gate stack of Ge oxynitride and low-temperature oxide (LTO) on bulk Ge substrate without a silicon (Si) cap layer. The fabricated devices show 2 /spl times/ higher transconductance and /spl sim/ 40% hole mobility enhancement over the Si control with a thermal SiO/sub 2/ gate dielectric, as well as the excellent subthreshold characteristics. For the first time, we demonstrate Ge MOSFETs with less than 100-mV/dec subthreshold slope. 相似文献
95.
Groshek Frank; Kerfoot Erin; McKenna Vanessa; Polackwich Alan S.; Gallagher Michela; Holland Peter C. 《Canadian Metallurgical Quarterly》2005,119(1):202
In Pavlovian appetitive conditioning, rats often acquire 2 classes of conditioned responses: those whose form is determined by the reinforcer, and those whose form is determined by characteristics of the conditioned stimulus (CS). Consistent with the results of previous lesion studies, reversible inactivation of amygdala central nucleus function during pairings of an auditory CS with food prevented the acquisition of conditioned orienting responses specific to auditory CSs, whereas food-related conditioned behaviors were acquired normally. Neither inactivation nor posttraining neurotoxic lesions of the central nucleus affected the expression of previously acquired conditioned orienting. Thus, although the central nucleus is critical to the acquisition of information required for conditioned orienting to auditory cues, it is not needed for maintaining this information for later use. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
96.
Claude Boulay Stéphanie Staquet Brice Delsaute Jérôme Carette Michela Crespini Oumaya Yazoghli-Marzouk Érick Merliot Sandrine Ramanich 《Materials and Structures》2014,47(1-2):141-155
Monitoring the evolution of an early age set of parameters on concrete is necessary to predict the early age behaviour of structures. The difficulty lies in the fact that this monitoring must be automatic because the concrete hardening process takes place over a long period after the casting. This paper presents a new methodology and an apparatus, specifically designed at IFSTTAR, to monitor the hardening process of a concrete. Mainly, the Young’s modulus can be monitored in compression. Measurements start soon after having cast the concrete and the sample temperature is completely controlled so that the concrete maturity is well mastered. The performances of this apparatus, obtained on an ordinary concrete, are compared to more classical measurements using an extensometer mounted on the sample just after the setting time and to ultrasonic measurements. In these cases, the temperatures were not controlled and results have to be expressed in equivalent time. A comparison with another method developed and used at ULB by using the same concrete, in the frame of a joined cooperation between our two laboratories is achieved. This test set up is based on the so called Temperature Stress Testing Machine (TSTM). This device has been specifically designed with a control of the concrete maturity by the use of a dummy specimen only submitted to free deformations (thermal, shrinkage). The TSTM allows compressive and tensile testing starting just after the setting time. In addition, concrete properties, such as compressive and tensile strength, have been characterized at early age. These values have been used for the design of the loading histories applied in the automatic tests. The heat released by the cement hydration has also been measured in order to express the results on a maturity scale. 相似文献
97.
Enrico Binetti Marinella Striccoli Teresa Sibillano Cinzia Giannini Rosaria Brescia Andrea Falqui Roberto Comparelli Michela Corricelli Raffaele Tommasi Angela Agostiano M Lucia Curri 《Science and Technology of Advanced Materials》2015,16(5)
Colloidal semiconductor nanocrystals, with intense and sharp-line emission between red and near-infrared spectral regions, are of great interest for optoelectronic and bio-imaging applications. The growth of an inorganic passivation layer on nanocrystal surfaces is a common strategy to improve their chemical and optical stability and their photoluminescence quantum yield. In particular, cation exchange is a suitable approach for shell growth at the expense of the nanocrystal core size. Here, the cation exchange process is used to promote the formation of a CdS passivation layer on the surface of very small PbS nanocrystals (2.3 nm in diameter), blue shifting their optical spectra and yielding luminescent and stable nanostructures emitting in the range of 700–850 nm. Structural, morphological and compositional investigation confirms the nanocrystal size contraction after the cation-exchange process, while the PbS rock-salt crystalline phase is retained. Absorption and photoluminescence spectroscopy demonstrate the growth of a passivation layer with a decrease of the PbS core size, as inferred by the blue-shift of the excitonic peaks. The surface passivation strongly increases the photoluminescence intensity and the excited state lifetime. In addition, the nanocrystals reveal increased stability against oxidation over time. Thanks to their absorption and emission spectral range and the slow recombination dynamics, such highly luminescent nano-objects can find interesting applications in sensitized photovoltaic cells and light-emitting devices. 相似文献
98.
Scarano S Ermini ML Spiriti MM Mascini M Bogani P Minunni M 《Analytical chemistry》2011,83(16):6245-6253
Surface plasmon resonance imaging (SPRi) was used as the transduction principle for the development of optical-based sensing for transgenes detection in human cell lines. The objective was to develop a multianalyte, label-free, and real-time approach for DNA sequences that are identified as markers of transgenosis events. The strategy exploits SPRi sensing to detect the transgenic event by targeting selected marker sequences, which are present on shuttle vector backbone used to carry out the transfection of human embryonic kidney (HEK) cell lines. Here, we identified DNA sequences belonging to the Cytomegalovirus promoter and the Enhanced Green Fluorescent Protein gene. System development is discussed in terms of probe efficiency and influence of secondary structures on biorecognition reaction on sensor; moreover, optimization of PCR samples pretreatment was carried out to allow hybridization on biosensor, together with an approach to increase SPRi signals by in situ mass enhancement. Real-time PCR was also employed as reference technique for marker sequences detection on human HEK cells. We can foresee that the developed system may have potential applications in the field of antidoping research focused on the so-called gene doping. 相似文献
99.
Minella M Rogora M Vione D Maurino V Minero C 《The Science of the total environment》2011,409(18):3463-3471
A model-based approach is here developed and applied to predict the long-term trends of indirect photochemical processes in the surface layer (5 m water depth) of Lake Maggiore, NW Italy. For this lake, time series of the main parameters of photochemical importance that cover almost two decades are available. As a way to assess the relevant photochemical reactions, the modelled steady-state concentrations of important photogenerated transients (•OH, 3CDOM* and CO3-•) were taken into account. A multivariate analysis approach was adopted to have an overview of the system, to emphasise relationships among chemical, photochemical and seasonal variables, and to highlight annual and long-term trends. Over the considered time period, because of the decrease of the dissolved organic carbon (DOC) content of water and of the increase of alkalinity, a significant increase is predicted for the steady-state concentrations of the radicals •OH and CO3−•. Therefore, the photochemical degradation processes that involve the two radical species would be enhanced. Another issue of potential photochemical importance is related to the winter maxima of nitrate (a photochemical •OH source) and the summer maxima of DOC (•OH sink and 3CDOM* source) in the lake water under consideration. From the combination of sunlight irradiance and chemical composition data, one predicts that the processes involving •OH and CO3−• would be most important in spring, while the reactions involving 3CDOM* would be most important in summer. 相似文献
100.
Can Bayram John A. Ott Kuen‐Ting Shiu Cheng‐Wei Cheng Yu Zhu Jeehwan Kim Manijeh Razeghi Devendra K. Sadana 《Advanced functional materials》2014,24(28):4492-4496
A method of forming cubic phase (zinc blende) GaN (referred as c‐GaN) on a CMOS‐compatible on‐axis Si (100) substrate is reported. Conventional GaN materials are hexagonal phase (wurtzite) (referred as h‐GaN) and possess very high polarization fields (~MV/cm) along the common growth direction of <0001>. Such large polarization fields lead to undesired shifts (e.g., wavelength and current) in the performance of photonic and vertical transport electronic devices. The cubic phase of GaN materials is polarization‐free along the common growth direction of <001>, however, this phase is thermodynamically unstable, requiring low‐temperature deposition conditions and unconventional substrates (e.g., GaAs). Here, novel nano‐groove patterning and maskless selective area epitaxy processes are employed to integrate thermodynamically stable, stress‐free, and low‐defectivity c‐GaN on CMOS‐compatible on‐axis Si. These results suggest that epitaxial growth conditions and nano‐groove pattern parameters are critical to obtain such high quality c‐GaN. InGaN/GaN multi‐quantum‐well structures grown on c‐GaN/Si (100) show strong room temperature luminescence in the visible spectrum, promising visible emitter applications for this technology. 相似文献