全文获取类型
收费全文 | 1606篇 |
免费 | 138篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 9篇 |
综合类 | 1篇 |
化学工业 | 655篇 |
金属工艺 | 15篇 |
机械仪表 | 22篇 |
建筑科学 | 60篇 |
矿业工程 | 1篇 |
能源动力 | 39篇 |
轻工业 | 347篇 |
水利工程 | 13篇 |
石油天然气 | 5篇 |
无线电 | 85篇 |
一般工业技术 | 248篇 |
冶金工业 | 48篇 |
原子能技术 | 6篇 |
自动化技术 | 191篇 |
出版年
2023年 | 20篇 |
2022年 | 146篇 |
2021年 | 216篇 |
2020年 | 82篇 |
2019年 | 61篇 |
2018年 | 69篇 |
2017年 | 54篇 |
2016年 | 75篇 |
2015年 | 65篇 |
2014年 | 84篇 |
2013年 | 111篇 |
2012年 | 99篇 |
2011年 | 120篇 |
2010年 | 92篇 |
2009年 | 70篇 |
2008年 | 71篇 |
2007年 | 64篇 |
2006年 | 46篇 |
2005年 | 43篇 |
2004年 | 33篇 |
2003年 | 21篇 |
2002年 | 24篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 16篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1990年 | 1篇 |
1989年 | 6篇 |
1988年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有1745条查询结果,搜索用时 31 毫秒
91.
Corrado Costa Paolo Menesatti Jacopo Aguzzi Stefano D’Andrea Francesca Antonucci Valentina Rimatori Federico Pallottino Marco Mattoccia 《Food and Bioprocess Technology》2010,3(1):43-48
The actual Italian production of clams is chiefly sustained by the native Tapes decussatus and the fortuitously imported Tapes philippinarum. Both species are commercialized as “Vongola verace”, but the commercial value of T. philippinarum is lower. The discrimination of species by sight is usually difficult and it cannot be done by observation based on shell
morphology but only when animals open their valves hence displaying the two siphons. In this study, we propose a new, noninvasive
method to discriminate individuals of both species based on the analysis of the external shape of their shells. Accordingly,
in sympatric populations at two sites of the Po river outlet, we have chosen individuals (63 for T. decussatus and 57 for T. philippinarum) of comparable commercial size for which a certain genetic discrimination was previously done. Pictures of the left side
valve were taken for all specimens. Their profiles were analyzed with the elliptic Fourier analysis. The mean outline for
each species was graphically extracted. The coefficients of the harmonic equations were analyzed by multivariate classification
(partial least squares discriminant analysis [PLSDA]). Results showed a high percentage of correct classification of individuals
of both species (96.6%). Contour analysis reflected the overall shell shape and thus identified morphological aspects that
were difficult to recognize and quantify in sight. The high percentage of correct classifications obtained by combining the
analysis of elliptic Fourier harmonics with PLSDA demonstrated the feasibility of this method to discriminate species with
a high level of resemblance. 相似文献
92.
Andrea Bianconi Gelsomina Aruta Francesca Rizzo Luca Francesco Salvati Pietro Zeppa Diego Garbossa Fabio Cofano 《International journal of molecular sciences》2022,23(8)
Despite the multidisciplinary management in the treatment of glioblastomas, the average survival of GBM patients is still 15 months. In recent years, molecular biomarkers have gained more and more importance both in the diagnosis and therapy of glial tumors. At the same time, it has become clear that non neoplastic cells, which constitute about 30% of glioma mass, dramatically influence tumor growth, spread, and recurrence. This is the main reason why, in recent years, scientific research has been focused on understanding the function and the composition of tumor microenvironment and its role in gliomagenesis and recurrence. The aim of this review is to summarize the most recent discovery about resident microglia, tumor-associated macrophages, lymphocytes, and the role of extracellular vesicles and their bijective interaction with glioma cells. Moreover, we reported the most recent updates about new therapeutic strategies targeting immune system receptors and soluble factors. Understanding how glioma cells interact with non-neoplastic cells in tumor microenvironment is an essential step to comprehend mechanisms at the base of disease progression and to find new therapeutic strategies for GBM patients. However, no significant results have yet been obtained in studies targeting single molecules/pathways; considering the complex microenvironment, it is likely that only by using multiple therapeutic agents acting on multiple molecular targets can significant results be achieved. 相似文献
93.
Antonio Di Bartolomeo Aniello Pelella Xiaowei Liu Feng Miao Maurizio Passacantando Filippo Giubileo Alessandro Grillo Laura Iemmo Francesca Urban Shi‐Jun Liang 《Advanced functional materials》2019,29(29)
Few‐layer palladium diselenide (PdSe2) field effect transistors are studied under external stimuli such as electrical and optical fields, electron irradiation, and gas pressure. The ambipolar conduction and hysteresis are observed in the transfer curves of the as‐exfoliated and unprotected PdSe2 material. The ambipolar conduction and its hysteretic behavior in the air and pure nitrogen environments are tuned. The prevailing p‐type transport observed at atmospheric pressure is reversibly turned into a dominant n‐type conduction by reducing the pressure, which can simultaneously suppress the hysteresis. The pressure control can be exploited to symmetrize and stabilize the transfer characteristics of the device as required in high‐performance logic circuits. The transistors are affected by trap states with characteristic times in the order of minutes. The channel conductance, dramatically reduced by the electron irradiation during scanning electron microscope imaging, is restored after an annealing of several minutes at room temperature. The work paves the way toward the exploitation of PdSe2 in electronic devices by providing an experiment‐based and deep understanding of charge transport in PdSe2 transistors subjected to electrical stress and other external agents. 相似文献
94.
Emanuele Salerno Francesca Martinelli Anna Tonazzini 《International Journal on Document Analysis and Recognition》2013,16(2):177-187
The problem of see-through cancelation in digital images of double-sided documents is addressed. We show that a nonlinear convolutional data model proposed elsewhere for moderate show-through can also be effective on strong back-to-front interferences, provided that the recto and verso pure patterns are estimated jointly. To this end, we propose a restoration algorithm that does not need any classification of the pixels. The see-through PSFs are estimated off-line, and an iterative procedure is then employed for a joint estimation of the pure patterns. This simple and fast algorithm can be used on both grayscale and color images and has proved to be very effective in real-world cases. The experimental results we report in this paper demonstrate that our algorithm outperforms the ones based on linear models with no need to tune free parameters and remains computationally inexpensive despite the nonlinear model and the iterative solution adopted. Strategies to overcome some of the residual difficulties are also envisaged. 相似文献
95.
项目地点:沙特阿拉伯利雅得项目类型:建筑(住宅)开工日期:未知该项目获2005年豪瑞可持续建筑大奖赛非洲中东地区提名奖 相似文献
96.
M.R. ten Breteler J. Feijen P.J. Dijkstra F. Signori 《Reactive and Functional Polymers》2013,73(1):30-38
Hetero-telechelic, low-molecular-weight polylactides (PLAs) were prepared by the zinc-catalyzed ring-opening polymerization of l-lactide or d-lactide using functional initiators and subsequent reaction with termination reagents, yielding –OH, –COOH, –NH2 and –SH as functional chain ends. Structural characterization was performed by molecular weight analysis, NMR spectroscopy and MALDI-TOF mass spectrometry. The thermal behavior of the species was investigated by DSC, which revealed that the modification of the hydroxyl terminus lowered the number of lactic acid units within a PLA chain that can effectively participate in crystallization. Both the Tm and ΔHm values for these polymers were lower compared to those of PLAs of comparable chain length with no modification of the hydroxyl end-group. In stereocomplexes prepared from equimolar amounts of the hetero-telechelic PLLAs and PDLAs, this suppressive effect on Tm and ΔHm was also observed. Modification of the hydroxyl ends to produce –COOH, –NH2 and –SH end groups reduced the stereocomplex Tm values to ~10–20 °C. The lower limit for the crystallization of the stereocomplexes was found at a DP of 5. 相似文献
97.
Gianluca Bianchi Fasani Francesca Bozzano Michele Cercato 《Bulletin of Engineering Geology and the Environment》2011,70(4):533-542
There are many abandoned underground mines beneath the city of Rome, created in the Pleistocene pyroclastic deposits over
thousands of years. These pose a serious public safety risk hence the study was undertaken to better assess the stability
of the underground workings. The Villa de Sanctis public park was selected as a suitable test site, as in this area the cavity
network can be inspected and the different steps of the progressive migration of voids toward the surface can be identified.
In addition to an underground geological survey, geophysical investigations were undertaken to elucidate some key characteristics
of the involved lithological units, including elastic stiffness and layer thickness. Recommendations are made for further
studies of the accessible and inaccessible areas. 相似文献
98.
In many cases masonry buildings present structural problems related to development of local mechanisms under seismic actions. The solution to this weakness has to be chosen taking into account several aspects if the construction is ancient and is gifted of monumental significance. In this paper the case of the Bell Tower of Santa Maria del Carmine (Napoli, Italy) is discussed; the construction has been deeply examined by the writers performing experimental inquires in situ and theoretical analysis with three-dimensional models. While the results obtained in the hypothesis of compact behavior of the structure have pointed out a low risk condition under seismic actions, in contrast the study of local out-of-plane mechanisms, dealt with in detail in this paper, have evidenced an unsafe situation. To avoid such mechanisms, connective systems with tie rods made of glass fiber-reinforced polymer laminates have been designed to be inserted where local verifications are not satisfied. Design, application, and monitoring procedures of this innovative intervention are discussed in detail herein. 相似文献
99.
100.
Thirty commercially available Italian carbonic macerated young red wines, have been analysed by HPLC–DAD–MS with the aim to characterise their pigment composition and find possible correlations with the colour features evaluated by means of spectrophotometric measurements. The composition in anthocyanin monoglucosides, acetates, p-coumarates as well as that in pyranoanthocyanins and direct and ethyl-bridged adducts with flavanols, was studied. Because of the peculiar maceration process, carbonic macerated wines demonstrated to be qualitatively rich in pyranoanthocyanins and pigment adducts. A number of ethyl-bridged anthocyanin isomers was found, together with significant contents of vitisin A and vitisin B (up to 15.5 mg/L as a sum). Malvidin-3-glc-4-vinylphenol was the main pyranoanthocyanin-vinylphenol adduct (up to 1.10 mg/L). The colour features of the wines were broadly distributed as a consequence of the percentage of carbonic macerated wine present in the marketed product. The statistical treatment of the entire data set revealed that pyranoanthocyanins are positively correlated with colour density (while no correlation was found for monoglucosides) and that direct adducts and/or ethyl-bridged compounds can play a role for what concerns the hue of carbonic macerated wines. 相似文献