全文获取类型
收费全文 | 3197篇 |
免费 | 202篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 62篇 |
综合类 | 1篇 |
化学工业 | 855篇 |
金属工艺 | 43篇 |
机械仪表 | 74篇 |
建筑科学 | 152篇 |
矿业工程 | 1篇 |
能源动力 | 102篇 |
轻工业 | 243篇 |
水利工程 | 10篇 |
石油天然气 | 3篇 |
武器工业 | 1篇 |
无线电 | 290篇 |
一般工业技术 | 581篇 |
冶金工业 | 139篇 |
原子能技术 | 27篇 |
自动化技术 | 819篇 |
出版年
2024年 | 5篇 |
2023年 | 41篇 |
2022年 | 131篇 |
2021年 | 150篇 |
2020年 | 77篇 |
2019年 | 89篇 |
2018年 | 98篇 |
2017年 | 92篇 |
2016年 | 143篇 |
2015年 | 113篇 |
2014年 | 146篇 |
2013年 | 221篇 |
2012年 | 203篇 |
2011年 | 232篇 |
2010年 | 193篇 |
2009年 | 193篇 |
2008年 | 179篇 |
2007年 | 165篇 |
2006年 | 118篇 |
2005年 | 93篇 |
2004年 | 117篇 |
2003年 | 97篇 |
2002年 | 63篇 |
2001年 | 50篇 |
2000年 | 42篇 |
1999年 | 36篇 |
1998年 | 28篇 |
1997年 | 24篇 |
1996年 | 35篇 |
1995年 | 27篇 |
1994年 | 25篇 |
1993年 | 19篇 |
1992年 | 21篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 11篇 |
1988年 | 3篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 16篇 |
1984年 | 17篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1975年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有3403条查询结果,搜索用时 0 毫秒
101.
Marco Biondi Sabato Fusco Andrew L. Lewis Paolo A. Netti 《Journal of materials science. Materials in medicine》2013,24(10):2359-2370
Drug-eluting beads (DEBs) are embolising devices in clinical use for the treatment of liver cancer by transarterial chemoembolisation. In this study, release kinetics of doxorubicin (DOX) and irinotecan (IRI) were investigated by experimental evaluations and mathematical modeling, based on Langmuir isotherm and two phenomenological models (Boyd/Bhaskar) developed to determine the actual mechanisms controlling drug release rate. The model was validated through release studies, in particular by assessing how drug loading, ionic strength of the release medium and device swelling during release influence drug release kinetics. Results demonstrated that IRI is released much faster than DOX, and that DEB volume strongly depends upon drug loading and fractional release. This effect was properly taken into account in developing the mathematical model. Experimental results were well fit by numerical simulations, and two different rate-controlling mechanisms were found to govern DOX and IRI delivery. 相似文献
102.
103.
104.
Renato Bacchetta Paolo Tremolada Cristiano Di Benedetto Nadia Santo Umberto Fascio Giuseppe Chirico Anita Colombo Marina Camatini Paride Mantecca 《Carbon》2012,50(12):4607-4618
Lethal and teratogenic potentials of carbon nanoparticles (CNPs) in their amorphous form were investigated by the standardized Frog Embryo Teratogenesis Assay-Xenopus (FETAX), a 96-h in vitro whole-embryo toxicity test based on the amphibian Xenopus laevis. Embryos were acutely exposed to 1, 10, 100 and 500 mg/L CNP suspensions and evaluated for lethality, malformations and growth inhibition. Larvae were processed for histological and ultrastructural analyses to detect the main affected organs, to look for specific lesions at the subcellular level and to image and track CNPs into tissues. Only the highest CNP suspension resulted in being embryolethal for X. laevis larvae, while malformed larva percentages significantly differed from controls starting from 100 mg/L. The stomach and gut were the preferential CNP accumulation sites, on the contrary, the digestive epithelium remained intact. The analyses showed the presence of isolated nanoparticles and/or aggregates in different secondary target organs. CNPs were found in circulating erythrocytes. The research confirms the good tolerance of X. laevis towards pure elemental carbon in its nanoparticulate amorphous form, but highlights the possibility of CNP transfer toward all body areas. 相似文献
105.
Large dynamical changes in thermalizing glassy systems are triggered by trajectories crossing record sized barriers, a behavior revealing the presence of a hierarchical structure in configuration space. The observation is here turned into a novel local search optimization algorithm dubbed record dynamics optimization, or RDO. RDO uses the Metropolis rule to accept or reject candidate solutions depending on the value of a parameter akin to the temperature and minimizes the cost function of the problem at hand through cycles where its ‘temperature’ is raised and subsequently decreased in order to expediently generate record high (and low) values of the cost function. Below, RDO is introduced and then tested by searching for the ground state of the Edwards–Anderson spin-glass model, in two and three spatial dimensions. A popular and highly efficient optimization algorithm, parallel tempering (PT), is applied to the same problem as a benchmark. RDO and PT turn out to produce solutions of similar quality for similar numerical effort, but RDO is simpler to program and additionally yields geometrical information on the system’s configuration space which is of interest in many applications. In particular, the effectiveness of RDO strongly indicates the presence of the above mentioned hierarchically organized configuration space, with metastable regions indexed by the cost (or energy) of the transition states connecting them. 相似文献
106.
Irene Appolloni Sebastiano Curreli Sara Caviglia Manuela Barilari Eleonora Gambini Aldo Pagano Paolo Malatesta 《International journal of molecular sciences》2012,13(11):14667-14678
Tumor progression is a key aspect in oncology. Not even the overexpression of a powerful oncogenic stimulus such as platelet derived growth factor-B (PDGF-B) is sufficient per se to confer full malignancy to cells. In previous studies we showed that neural progenitors overexpressing PDGF-B need to undergo progression to acquire the capability to give rise to secondary tumor following transplant. By comparing the expression profile of PDGF-expressing cells before and after progression, we found that progressed tumors consistently downregulate the expression of the antiproliferative gene Btg2. We therefore tested whether the downregulation of Btg2 is sufficient and necessary for glioma progression with loss and gain of function experiments. Our results show that downregulation of Btg2 is not sufficient but is necessary for tumor progression since the re-introduction of Btg2 in fully progressed tumors dramatically impairs their gliomagenic potential. These results suggest an important role of Btg2 in glioma progression. Accordingly with this view, the analysis of public datasets of human gliomas showed that reduced level of Btg2 expression correlates with a significantly worse prognosis. 相似文献
107.
The problem of assigning radio resources and transmission formats to users in the downlink of an OFDMA network is addressed. In particular, a single cell environment with a realistic interference model and a margin adaptive approach is considered, i.e., the aim is of minimizing the total transmission power while maintaining a certain given rate for each user. The computational complexity issues of the problem are discussed, and an approximation analysis is presented. Heuristic approaches, based on rounding techniques and graph models, are also proposed. Computational experiences show that, in a comparison with a commercial state-of-the-art optimization solver and with alternatives from the literature, the proposed algorithms are effective in terms of solution quality and CPU times. 相似文献
108.
109.
Matteo Ottavian Pierantonio Facco Massimiliano Barolo Paolo Berzaghi Severino Segato Enrico Novelli Stefania Balzan 《Journal of food engineering》2012
This study investigated the possibility of using near-infrared spectroscopy (NIRS) for the authentication of Asiago d’allevo, a protected designation of origin cheese from northern Italy. Latent variable models applied on spectral data were developed and used to estimate several chemical properties and to classify the available dataset according to the location and management of the cheesemaking factory (lowland and alpine), the ripening age (6, 12, 18 and 36 months), the altitude of milk production (low, medium, medium–high and high), and the period of the year of the cheese production (May, July and September). The variable importance in projection index was used to identify the most informative spectral regions for discrimination. Results showed that NIR spectra can be used both to accurately estimate several chemical properties and to classify the samples according to the different experimental conditions under investigation with the same discrimination capacity provided by traditional chemical analysis. 相似文献
110.
Mahmoud Abdellatief Andrea Lausi Jasper R. Plaisier Paolo Scardi 《Metallurgical and Materials Transactions A》2014,45(1):123-128
The growth process of nanocrystalline fluorite was studied by in situ synchrotron radiation X-ray diffraction. The two studied samples had comparable crystalline domain size, but quite different content of lattice defects as a result of the different preparation procedures: ball milling of coarse CaF2 powder or coprecipitation of CaCl2 and NH4F. It is shown that the high dislocation density in the ball-milled fluorite is responsible for a recrystallization process above 773 K (500 °C), which is not observed in the chemically synthesized fluorite. The linear thermal expansion coefficients of both nanocrystalline powders, as obtained and also from the in situ X-ray diffraction data, show a smaller increase with temperature than suggested by the literature on coarse-grained fluorite. 相似文献