全文获取类型
收费全文 | 6902篇 |
免费 | 925篇 |
国内免费 | 177篇 |
专业分类
电工技术 | 100篇 |
综合类 | 328篇 |
化学工业 | 2530篇 |
金属工艺 | 204篇 |
机械仪表 | 101篇 |
建筑科学 | 284篇 |
矿业工程 | 121篇 |
能源动力 | 207篇 |
轻工业 | 1831篇 |
水利工程 | 74篇 |
石油天然气 | 197篇 |
武器工业 | 8篇 |
无线电 | 537篇 |
一般工业技术 | 1024篇 |
冶金工业 | 161篇 |
原子能技术 | 89篇 |
自动化技术 | 208篇 |
出版年
2024年 | 30篇 |
2023年 | 118篇 |
2022年 | 148篇 |
2021年 | 226篇 |
2020年 | 258篇 |
2019年 | 269篇 |
2018年 | 277篇 |
2017年 | 334篇 |
2016年 | 275篇 |
2015年 | 350篇 |
2014年 | 424篇 |
2013年 | 527篇 |
2012年 | 434篇 |
2011年 | 513篇 |
2010年 | 402篇 |
2009年 | 394篇 |
2008年 | 348篇 |
2007年 | 429篇 |
2006年 | 329篇 |
2005年 | 292篇 |
2004年 | 241篇 |
2003年 | 244篇 |
2002年 | 198篇 |
2001年 | 119篇 |
2000年 | 121篇 |
1999年 | 101篇 |
1998年 | 79篇 |
1997年 | 67篇 |
1996年 | 56篇 |
1995年 | 55篇 |
1994年 | 42篇 |
1993年 | 44篇 |
1992年 | 50篇 |
1991年 | 43篇 |
1990年 | 33篇 |
1989年 | 24篇 |
1988年 | 21篇 |
1987年 | 18篇 |
1986年 | 9篇 |
1985年 | 23篇 |
1984年 | 15篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有8004条查询结果,搜索用时 0 毫秒
31.
MODELING AND PREDICTIVE CONTROL OF MIMO NONLINEAR SYSTEMS USING WIENER-LAGUERRE MODELS 总被引:1,自引:0,他引:1
Prabirkumar Saha S. H. Krishnan V. S. R. Rao Sachin C. Patwardhan 《Chemical Engineering Communications》2004,191(8):1083-1119
In this work, a Weiner-type nonlinear black box model was developed for capturing dynamics of open loop stable MIMO nonlinear systems with deterministic inputs. The linear dynamic component of the model was parameterized using orthogonal Laguerre filters while the nonlinear state output map was constructed either using quadratic polynomial functions or artificial neural networks. The properties of the resulting model, such as open loop stability and steady-state behavior, are discussed in detail. The identified Weiner-Laguerre model was further used to formulate a nonlinear model predictive control (NMPC) scheme. The efficacy of the proposed modeling and control scheme was demonstrated using two benchmark control problems: (a) a simulation study involving control of a continuously operated fermenter at its optimum (singular) operating point and (b) experimental verification involving control of pH at the critical point of a neutralization process. It was observed that the proposed Weiner-Laguerre model is able to capture both the dynamic and steady-state characteristics of the continuous fermenter as well as the neutralization process reasonably accurately over wide operating ranges. The proposed NMPC scheme achieved a smooth transition from a suboptimal operating point to the optimum (singular) operating point of the fermenter without causing large variation in manipulated inputs. The proposed NMPC scheme was also found to be robust in the face of moderate perturbation in the unmeasured disturbances. In the case of experimental verification using the neutralization process, the proposed control scheme was found to achieve much faster transition to a set point close to the critical point when compared to a conventional gain-scheduled PID controller. 相似文献
32.
33.
本工作是在非离子凝胶的分子热力学模型基础,引入Donnan平衡项和大分子离子链的静电排斥项对凝胶自由能的贡献,建立了一个新的离子凝胶的分子热力学模型。该模型在解释离子凝胶的PH敏感性及其各种影响因素,以及预测PH溶胀曲线方面都取得了较好的效果。 相似文献
34.
In membrane filtration, solution environment factors such as pH and solvent density are important in controlling the filtration
rate and the rejection of the particles and/or the macromolecules. The filtration rate and the rejection in membrane filtration
have been investigated from physicochemical aspects. It was shown that the properties of the filter cake formed on the membrane
surface play a vital role in determining the filtration rate in mem-brane filtration. It was clearly demonstrated that such
filtration behaviors as the filtration rate and the rejection are highly dependent on the electrical nature of the particles
and/or the macromolecules. Furthermore, it was shown that the solvent density ρ has a large effect on the steady filtration
rate in upward ultrafiltration. 相似文献
35.
Polyaspartate is an excellent Pb2+‐binding agent in comparison with some polyaspartamide derivatives with different side chains, in that it possesses a higher Pb2+ uptake and a lower Pb2+ equilibrium concentration. Equilibrium sorption data for Pb2+ on polyaspartate can be well fitted with the Freundlich and Langmuir models. Experimental results show that a crosslinked polyaspartate hydrogel is superior to poly(acrylic acid)‐based resins and polystyrene‐based chelating resins. IR spectra and X‐ray photoelectron spectra reveal that the polyaspartate hydrogel binds Pb2+ by both an ion‐exchange mechanism and a chelating mechanism. The polyaspartate hydrogel is also an effective agent for the removal of Pb2+ from glycyrrhizin. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2215–2220, 2005 相似文献
36.
Equilibrium exchange isotherms were determined for the exchange of Cu2+ with NaZSM-5 at varying Cu(Ac)2 concentrations in solutions of constant volume and zeolite weight. At low Cu2+ levels the solid scavenged all the copper ions. When copper could be detected in the equilibrated solutions, overexchange was observed. The extent of overexchange was higher at pH 6 than at pH 4. These results were analyzed in relation to catalytic activity.On leave from the Central Institute for Chemistry, Hungarian Academy of Sciences, H1525 Budapest, Hungary. 相似文献
37.
《Journal of Process Control》2014,24(7):1023-1037
In this research the use of a feedback PID-like fuzzy controller scheme for pH control is presented to deal with instability problems near the equivalence point in neutralization processes. State space analysis of the titration curves and a fuzzy clustering algorithm based on calculating a measure of potential derived from the square distance of the pH data are complementary applied to define the membership structure and the fuzzy sets of the controller. To test the performance of the controller, both simulated and experimental runs were used. The fuzzy controller was tested for compensating step-change perturbations of propionic acidic flow rates, propionic acid concentration, and buffering conditions. Stationary cycling behavior has been observed for large loads of acidic flow rates. It was found that though the rejection time was strongly dependent on the mean residence time of the liquid solutions, the proposed controller keep the neutralization process operating close to the specified set point of pH = 7. 相似文献
38.
为了探究影响GH5家族β-甘露聚糖酶最适pH的各种因素,利用该酶的序列信息,构建了基于氨基酸组成的β-甘露聚糖酶理化性质与其最适pH的相关性模型。结果表明:该酶N端氨基酸序列是影响其最适pH的重要因素,在243个理化性质中有17个呈极显著相关,其中7个呈正相关。优化的转移能量参数相关性最高,为0.78:7个正相关的理化性质中,与螺旋相关的理化性质占3个。优化的转移能量参数和螺旋是影响pH稳定性的最重要的因素。所建立的模型为研究该酶酸碱适应性机理提供了一种简单有效的方法。 相似文献
39.
40.
The hydrogenation of diene‐based polymers via diimide is a very attractive alternative to the conventional catalytic hydrogenation route based on gaseous molecular hydrogen. However, serious crosslinking always accompanies it and limits the end‐use properties of the polymers. Gel formation in polymers that are hydrogenated via diimide has been investigated in detail through an inspection of all the chemical reactions involved in the process. The results indicate that hydrogen peroxide decomposition, some reactions related to oxygen, and the redox reaction between hydrogen peroxide and hydrazine are capable of generating radicals. However, radicals generated in the aqueous phase do not appear to initiate the crosslinking of diene‐based polymers in the latex form. It is proposed that the primary radicals giving rise to crosslinking are generated in the polymer phase in situ, and the step responsible for generating these organic radicals is possibly the diimide disproportionation reaction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1122–1125, 2005 相似文献