全文获取类型
收费全文 | 2064篇 |
免费 | 122篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 22篇 |
综合类 | 2篇 |
化学工业 | 526篇 |
金属工艺 | 25篇 |
机械仪表 | 33篇 |
建筑科学 | 68篇 |
矿业工程 | 1篇 |
能源动力 | 89篇 |
轻工业 | 195篇 |
水利工程 | 8篇 |
石油天然气 | 5篇 |
无线电 | 165篇 |
一般工业技术 | 330篇 |
冶金工业 | 204篇 |
原子能技术 | 25篇 |
自动化技术 | 489篇 |
出版年
2024年 | 5篇 |
2023年 | 18篇 |
2022年 | 78篇 |
2021年 | 105篇 |
2020年 | 53篇 |
2019年 | 92篇 |
2018年 | 76篇 |
2017年 | 76篇 |
2016年 | 89篇 |
2015年 | 75篇 |
2014年 | 87篇 |
2013年 | 145篇 |
2012年 | 135篇 |
2011年 | 149篇 |
2010年 | 125篇 |
2009年 | 113篇 |
2008年 | 99篇 |
2007年 | 77篇 |
2006年 | 74篇 |
2005年 | 48篇 |
2004年 | 57篇 |
2003年 | 34篇 |
2002年 | 23篇 |
2001年 | 20篇 |
2000年 | 21篇 |
1999年 | 19篇 |
1998年 | 21篇 |
1997年 | 24篇 |
1996年 | 25篇 |
1995年 | 32篇 |
1994年 | 23篇 |
1993年 | 12篇 |
1992年 | 3篇 |
1991年 | 27篇 |
1990年 | 24篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 21篇 |
1983年 | 6篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有2187条查询结果,搜索用时 7 毫秒
1.
DNA double-strand breaks are very genotoxic lesions that can result in chromosome aberrations. The current view is that DNA double-strand breaks are repaired most efficiently through homologous recombination in yeast and simple end-joining in mammalian cells. However, recent experiments reveal that both repair pathways are conserved from yeast to mammals, including humans. The challenge ahead is to put the different pieces of the jigsaw together into coherent mechanisms for both pathways and to determine their relative contributions to ionizing-radiation resistance and to the prevention of genetic instability and carcinogenesis. 相似文献
2.
3.
Emilio Marengo Valentina Longo Elisa Robotti Marco Bobba Fabio Gosetti Orfeo Zerbinati Silvana Di Martino 《应用聚合物科学杂志》2008,109(6):3975-3982
Principal component regression (PCR), partial least squares (PLS), StepWise ordinary least squares regression (OLS), and back‐propagation artificial neural network (BP‐ANN) are applied here for the determination of the propylene concentration of a set of 83 production samples of ethylene–propylene copolymers from their infrared spectra. The set of available samples was split into (a) a training set, for models calculation; (b) a test set, for selecting the correct number of latent variables in PCR and PLS and the end point of the training phase of BP‐ANN; (c) a production set, for evaluating the predictive ability of the models. The predictive ability of the models is thus evaluated by genuine predictions. The model obtained by StepWise OLS turned out to be the best one, both in fitting and prediction. The study of the breakdown number of samples to be included in the training set showed that at least 52 experiments are necessary to build a reliable and predictive calibration model. It can be concluded that FTIR spectroscopy and OLS can be properly employed for monitoring the synthesis or the final product of ethylene–propylene copolymers, by predicting the concentration of propylene directly along the process line. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
4.
5.
This paper reports off-lattice Monte Carlo simulations of highly-branched comb homopolymers weakly adsorbed on a flat, featureless surface showing only covolume and dispersion interactions with the adsorbate. A minimal coarse-grained model, described by hard spheres connected by harmonic springs, was employed. The interaction energy of the adsorbed combs and linear chains is first discussed as a function of the molecular mass and of the number of beads in contact with the surface. The molecular size is then investigated as a function of backbone length and branching density at a fixed arm size. The apparent swelling exponents of the adsorbed combs are larger than those of the corresponding linear chains, and much larger than that of the free molecules. This result indicates a surface-induced stiffening of the comb backbone, further studied through the persistence length lpers. It is found that lpers increases upon adsorption over the free-molecule value, more so the larger is the branching density. Finally, the thickness of the adsorbed layer, the surface-induced molecular anisotropy and the molecular aspect ratio are investigated as a function of branching density and molecular mass. 相似文献
6.
7.
8.
9.
In this paper we discuss about geographic representations as a basis for describing, organizing, accessing and understanding heterogeneous shared information on the web. Maps are popular on the web, because of the reference to space, the most important domain of human experience, the proliferation of location aware devices and services and the availability of a set of tools that enable an heterogeneous population of users to explore and even modify these representations.Metaphorical maps, representing concepts and relations of a specific knowledge domain with symbols taken from another well known and widely used domain, couple the benefits of cartographic representation with the power and intuitiveness of the metaphor, permitting the communication and sharing of such knowledge.We introduce a classification of maps based on antinomies between real and imaginary worlds, and between direct and metaphoric knowledge; we argue that cartography can be used as a visual language for organizing and sharing knowledge related to different semantic domains, supporting our arguments with examples. Finally, we define a set of functions and related data structures able to support a user in browsing cartographic representations using state-of-art tools and systems available on the web. 相似文献
10.
Vehicular sensor networks are an emerging network paradigm, suitable for various applications in vehicular environment making use of vehicles’ sensors as data sources and Inter-Vehicle Communication systems for the transmissions. We present a solution, based on vehicular sensor networks, for gathering data from a certain geographic area while satisfying with a specific delay bound. The method leverages the time interval during which the query is active in order to make the gathering process efficient, properly alternating data muling and multi-hop forwarding strategies like in delay-bounded routing protocols. Simulations show that our proposed solution succeeds in performing efficient data gathering outperforming other solutions. 相似文献