全文获取类型
收费全文 | 133943篇 |
免费 | 18710篇 |
国内免费 | 13965篇 |
专业分类
电工技术 | 11752篇 |
技术理论 | 8篇 |
综合类 | 17520篇 |
化学工业 | 11128篇 |
金属工艺 | 4395篇 |
机械仪表 | 10091篇 |
建筑科学 | 12876篇 |
矿业工程 | 4587篇 |
能源动力 | 6104篇 |
轻工业 | 4372篇 |
水利工程 | 8663篇 |
石油天然气 | 7265篇 |
武器工业 | 2085篇 |
无线电 | 10917篇 |
一般工业技术 | 11875篇 |
冶金工业 | 4663篇 |
原子能技术 | 1331篇 |
自动化技术 | 36986篇 |
出版年
2024年 | 752篇 |
2023年 | 2114篇 |
2022年 | 4092篇 |
2021年 | 4679篇 |
2020年 | 5046篇 |
2019年 | 4380篇 |
2018年 | 4190篇 |
2017年 | 5194篇 |
2016年 | 5978篇 |
2015年 | 6215篇 |
2014年 | 8240篇 |
2013年 | 8795篇 |
2012年 | 9811篇 |
2011年 | 10606篇 |
2010年 | 8363篇 |
2009年 | 8681篇 |
2008年 | 8702篇 |
2007年 | 9851篇 |
2006年 | 8516篇 |
2005年 | 7487篇 |
2004年 | 6025篇 |
2003年 | 5262篇 |
2002年 | 4136篇 |
2001年 | 3419篇 |
2000年 | 2976篇 |
1999年 | 2267篇 |
1998年 | 1918篇 |
1997年 | 1570篇 |
1996年 | 1481篇 |
1995年 | 1288篇 |
1994年 | 1051篇 |
1993年 | 747篇 |
1992年 | 614篇 |
1991年 | 485篇 |
1990年 | 384篇 |
1989年 | 324篇 |
1988年 | 201篇 |
1987年 | 129篇 |
1986年 | 100篇 |
1985年 | 98篇 |
1984年 | 104篇 |
1983年 | 47篇 |
1982年 | 67篇 |
1981年 | 35篇 |
1980年 | 49篇 |
1979年 | 48篇 |
1978年 | 16篇 |
1974年 | 9篇 |
1959年 | 19篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
本文给出计算H2O-NH3-CO2三元体系在温度323.15K~473.15K、压力0.2MPa~8.0MPa、液相NH,摩尔分率≤0.3、富氨区条件下汽液平衡的UNIQUAC模型及其参数,模型的计算结果与试验数据吻合。该模型可用于尿素生产装置中蒸发冷凝、循环吸收以及水解精馏等过程的设备计算。 相似文献
992.
P. Muthuswamy C. R. Ranganathan V. Murugappan P. Santhy G. Ramanathan 《Nutrient Cycling in Agroecosystems》1990,23(3):135-140
A mathematical model has been proposed for predicting the changes in soil nitrogen status due to continuous fertilization in a continuous cropping sequence. The model also enabled the prediction of the steady state of soil nitrogen for a specified fertilizer practice.The model was applied to six years nitrogen availability data of four fertilizer practices in finger millet-maize-cowpea sequence followed in the Long Term Fertilizer Experiments conducted at Tamil Nadu Agricultural University, Coimbatore, India. The agreement between the predicted soil nitrogen status by the model and the actuals was proved by employing reliability index. 相似文献
993.
Cheng-Liang Chang Hsuan Chang Yuan-Cheng Chang 《Journal of the Chinese Institute of Chemical Engineers》2007
A hybrid mathematic model for pervaporation is proposed which incorporates the concepts of solution-diffusion model and pore model. The model allows performance prediction as well as the establishment of the internal concentration and pressure profiles within the membrane. The model parameters specific to the particular membrane and mixture system are determined using liquid sorption and pervaporation experimental data. The model is experimentally examined using ethanol–water mixtures and poly(dimethyl siloxane)–poly(vinyldiene fluoride) (PDMS–PVDF) composite membranes. The characteristics of flux and separation factor predicted using the model are in fair agreement with the experimental data under various feed concentrations and downstream pressures for different membrane arrangements, including single-layer, reverse single-layer and double-layer PDMS–PVDF composite membranes. Internal profiles of pressure, concentration and component mole fraction can be established using the model. Concentration polarization phenomena for ethanol and water are located at membrane interfaces and vapor–liquid interfaces, respectively. Performances of several different membrane designs are compared using the model. 相似文献
994.
尿素装置液相浓度在线自动检测软件的研究 总被引:1,自引:1,他引:1
为了改善尿素装置先进的控制和落后的人工检测物料浓度之间的矛盾,运用化工热力学原理,以及热力学模型组合求解法,研制了液相浓度实时检测软件。并开发了多种软件以适应各类尿素流程(水溶液全循环法、CO2汽提法、氨汽提法)的需要 相似文献
995.
Abstract. The simultaneous switching autoregressive (SSAR) model proposed by Kunitomo and Sato (A non-linearity in economic time series and disequilibrium econometric models. In Theory and Application of Mathematical Statistics (ed. A. Takemura). Tokyo:University of Tokyo Press (in Japanese), 1994; Asymmetry in economic time series and simultaneous switching autoregressive model. Struct. Change Econ. Dyn. , forthcoming (1994).) is a Markovian non-linear time series model. We investigate the finite sample as well as the asymptotic properties of the least squares estimator and the maximum likelihood (ML) estimator. Due to a specific simultaneity involved in the SSAR model, the least squares estimator is badly biased. However, the ML estimator under the assumption of Gaussian disturbances gives reasonable estimates. 相似文献
996.
Krzysztof Kaczmarski Dongmei Zhou Georges Guiochon 《Chemical engineering science》2003,58(11):2325-2338
The adsorption isotherm data of R- and S-1-indanol and of their racemic mixture on cellulose tribenzoate were measured by frontal analysis. These experimental data were fitted to the single-component and the modified competitive Bilangmuir isotherms. The overloaded elution profiles of bands of the pure enantiomers and of the racemic mixture were calculated for different sample sizes, using the best competitive isotherm model and the General Rate Model of chromatography coupled with the generalized Maxwell-Stefan equation that describes the surface diffusion flux. The calculated and the experimental profiles were found to be in excellent agreement in all cases. The parameters of the model of the mass transfer kinetics were derived from the band profiles obtained for the pure enantiomers. The same values of these parameters give an excellent prediction of the profiles of multicomponent bands. The new model described here allows a satisfactory interpretation of the competitive mass transfer kinetics. 相似文献
997.
A predictive model was developed for the fully developed zone of a circulating fluidized bed (CFB) riser reactor operating in the fast fluidization regime that overcomes limitations of existing models. The model accounts for the upward flow of gas and solids in the core and downward flow of the two phases in the annulus. Additionally, a numerical solution methodology for the simulation of a riser reactor employing the hydrodynamic model was devised. A simulation was performed using the fast, main Claus reaction to demonstrate the effects of backmixing in the fast fluidization regime. It was found that the molar flow rates of the reactants leaving a fast fluidized CFB riser reactor were significantly higher than those leaving an identical reactor operating in the pneumatic transport regime. 相似文献
998.
就贵州省化工企业加强质量文化建设必要性和紧迫性作用思考,通过对质量文化内涵的分析,提出我省化工企业应走“质量效益型”的道路,并指出实践中应注意的问题。 相似文献
999.
1000.
The ironmaking blast furnace is regarded as one of the biggest and most complex industrial reactors, because it includes various materials like gas, lump granular materials, liquids and powders and more than 30 major reactions and phase changes in a single reaction vessel. The mathematical simulator of this process developed in this study used the multi-fluid treatment as its framework, since the motions of these materials were governed by different flow mechanisms. The rates of the interactions among the phases and the chemical reactions were evaluated based on kinetic theories. The model successfully reproduced the fields of velocity, temperature and reaction in the furnace and its validity was confirmed. The simulator was also applied to a novel operation, namely the top gas recycling combined with the carbon-composite iron-ore charging and the waste plastics injection, and the advantages in furnace efficiency and environmental load were quantitatively indicated. 相似文献