全文获取类型
收费全文 | 151683篇 |
免费 | 19508篇 |
国内免费 | 14348篇 |
专业分类
电工技术 | 19037篇 |
技术理论 | 12篇 |
综合类 | 19630篇 |
化学工业 | 7499篇 |
金属工艺 | 3087篇 |
机械仪表 | 9005篇 |
建筑科学 | 7115篇 |
矿业工程 | 3729篇 |
能源动力 | 3286篇 |
轻工业 | 5333篇 |
水利工程 | 3124篇 |
石油天然气 | 2938篇 |
武器工业 | 1549篇 |
无线电 | 26523篇 |
一般工业技术 | 10360篇 |
冶金工业 | 2922篇 |
原子能技术 | 836篇 |
自动化技术 | 59554篇 |
出版年
2024年 | 1089篇 |
2023年 | 3008篇 |
2022年 | 5515篇 |
2021年 | 6025篇 |
2020年 | 6222篇 |
2019年 | 4683篇 |
2018年 | 4135篇 |
2017年 | 4782篇 |
2016年 | 5119篇 |
2015年 | 5714篇 |
2014年 | 9368篇 |
2013年 | 9281篇 |
2012年 | 10926篇 |
2011年 | 11498篇 |
2010年 | 8906篇 |
2009年 | 9624篇 |
2008年 | 9882篇 |
2007年 | 11199篇 |
2006年 | 9657篇 |
2005年 | 8610篇 |
2004年 | 7295篇 |
2003年 | 6315篇 |
2002年 | 5055篇 |
2001年 | 4255篇 |
2000年 | 3571篇 |
1999年 | 2957篇 |
1998年 | 2226篇 |
1997年 | 1833篇 |
1996年 | 1545篇 |
1995年 | 1251篇 |
1994年 | 981篇 |
1993年 | 695篇 |
1992年 | 534篇 |
1991年 | 400篇 |
1990年 | 343篇 |
1989年 | 282篇 |
1988年 | 180篇 |
1987年 | 105篇 |
1986年 | 76篇 |
1985年 | 81篇 |
1984年 | 60篇 |
1983年 | 65篇 |
1982年 | 58篇 |
1981年 | 22篇 |
1980年 | 20篇 |
1979年 | 18篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
Kum‐Il Lee Yong‐Sik Yim Sang‐Wook Chung Jiaqiu Wei Jong Il Rhee 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(9):1036-1045
A two‐dimensional (2D) spectrofluorometer was used to monitor various fermentation processes with recombinant E coli for the production of 5‐aminolevulinic acid (ALA). The whole fluorescence spectral data obtained during a process were analyzed using artificial neural networks, ie self‐organizing map (SOM) and feedforward backpropagation neural network (BPNN). The SOM‐based classification of the whole spectral data has made it possible to qualitatively associate some process parameters with the normalized weights and variances, and to select some useful combinations of excitation and emission wavelengths. Based on the classified fluorescence spectra a supervised BPNN algorithm was used to predict some of the process parameters. It was also shown that the BPNN models could elucidate some sections of the process's performance, eg forecasting the process's performance. Copyright © 2005 Society of Chemical Industry 相似文献
43.
In this paper, genetic algorithm is used to help improve the tolerance of feedforward neural networks against an open fault. The proposed method does not explicitly add any redundancy to the network, nor does it modify the training algorithm. Experiments show that it may profit the fault tolerance as well as the generalisation ability of neural networks. 相似文献
44.
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
45.
The scope of the present work is the application of a particular class of strain energy function, based on the logarithmic strain, for the prediction of the twisting moment and axial force of a rubber circular cylinder under combined extension and torsion. The strain energy function involves four material parameters three of which are determined by fitting published experimental data from simple tensile and compression tests of natural rubber. One of the parameters of the proposed model has physical meaning, and it is equal to one ninth of the initial modulus of elasticity of the material. Hence, the number of unknown parameters is reduced to three. The logarithmic strain energy function is then applied to a combined extension and torsion problem of a rubber circular cylinder to check its performance for more complicated deformations. The results are compared with corresponding experimental and theoretical solutions available in the literature to validate the proposed model. It is found that the proposed strain energy function apart from predicting the common modes of deformations is also capable to determine more complicated types of deformation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
46.
47.
Yeon Seok Kim 《Polymer》2008,49(2):570-578
Monodispersed copolymer emulsions with different glass transition temperatures were synthesized to investigate the effect of room temperature polymer matrix modulus on the electrical properties of carbon black (CB) filled segregated network composites. The emulsion with the highest modulus at room temperature produced composites with the lowest percolation threshold. The threshold for a composite made from a copolymer latex containing an equal ratio of butyl acrylate and methyl methacrylate (BA5) is 1.5 vol%, while the percolation threshold for the much lower modulus BA7 (7:3 BA/MMA ratio) is 4.93 vol%. The microstructure of each composite shows significant differences in the level of CB dispersion within the polymer matrix. Higher modulus polymer particles push the CB more efficiently into the interstitial space between them, resulting in a lower percolation threshold. This modulus effect was confirmed by increasing the drying temperature, where the moduli of latexes (BA5, BA5.5, and BA6) were more similar and the percolation thresholds for three composites also become closer to one another. 相似文献
48.
Yu. S. Yakovlev 《Cybernetics and Systems Analysis》2003,39(5):765-776
Distinctive features of architectural-structural organization and use of memory networks are considered with the aim of choosing an optimal configuration in designing distributed computer systems. 相似文献
49.
Veysel T. Yilmaz Evrim Senel Canan Kazak 《Journal of Inorganic and Organometallic Polymers and Materials》2008,18(3):407-413
The reaction of [Cu(sac)2(H2O)4] · 2H2O with 2-methylpyrazine (mpyz) leads two complexes, concomitant crystallization of a mononuclear complex [Cu(sac)2(mpyz)(H2O)2] (1) and a polymeric complex [Cu(sac)2(μ-mpyz)]n (2). Both complexes have been characterized by elemental analyses, magnetic measurements, FT-IR and ESR, TG-DTA and single-crystal
X-ray diffraction analyses. Single-crystal X-ray analyses show that complex 1 consists of discrete molecules in which the copper(II) ions exhibits a square-pyramidal coordination geometry. The individual
molecules of 1 are connected into a hydrogen-bonded chain structure, which is further assembled to form a three-dimensional network by π–π stacking interactions.
Complex 2 is an 1D coordination polymer in which copper(II) centers are bridged by the mpyz ligand. The chains are further assembled
to form two-dimensional frameworks by π–π and C–H···π stacking interactions. 相似文献
50.
分析实现永州电力通信交换网集中操作和维护的必要性,介绍了实现程控交换机远程操作和维护的两种方式,总结在实践过程中所得到的经验和教训。 相似文献