全文获取类型
收费全文 | 48345篇 |
免费 | 5716篇 |
国内免费 | 3155篇 |
专业分类
电工技术 | 4168篇 |
综合类 | 4865篇 |
化学工业 | 4805篇 |
金属工艺 | 2061篇 |
机械仪表 | 6753篇 |
建筑科学 | 1917篇 |
矿业工程 | 1124篇 |
能源动力 | 1752篇 |
轻工业 | 983篇 |
水利工程 | 840篇 |
石油天然气 | 1833篇 |
武器工业 | 907篇 |
无线电 | 6198篇 |
一般工业技术 | 4571篇 |
冶金工业 | 1118篇 |
原子能技术 | 305篇 |
自动化技术 | 13016篇 |
出版年
2024年 | 87篇 |
2023年 | 653篇 |
2022年 | 1070篇 |
2021年 | 1379篇 |
2020年 | 1503篇 |
2019年 | 1295篇 |
2018年 | 1319篇 |
2017年 | 1716篇 |
2016年 | 2004篇 |
2015年 | 2218篇 |
2014年 | 3053篇 |
2013年 | 3009篇 |
2012年 | 3411篇 |
2011年 | 4036篇 |
2010年 | 2861篇 |
2009年 | 3129篇 |
2008年 | 3075篇 |
2007年 | 3639篇 |
2006年 | 3091篇 |
2005年 | 2635篇 |
2004年 | 2164篇 |
2003年 | 1938篇 |
2002年 | 1530篇 |
2001年 | 1265篇 |
2000年 | 1066篇 |
1999年 | 767篇 |
1998年 | 579篇 |
1997年 | 483篇 |
1996年 | 415篇 |
1995年 | 367篇 |
1994年 | 306篇 |
1993年 | 245篇 |
1992年 | 192篇 |
1991年 | 145篇 |
1990年 | 116篇 |
1989年 | 121篇 |
1988年 | 73篇 |
1987年 | 42篇 |
1986年 | 31篇 |
1985年 | 31篇 |
1984年 | 29篇 |
1983年 | 12篇 |
1982年 | 17篇 |
1981年 | 16篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 15篇 |
1956年 | 5篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
本文建立了PC结构施工全过程的BIM模型及有限元分析模型,对施工过程进行数值模拟与动态、静态监测,对装配式结构进行了结构性能评价,为结构可视化施工监测提供了技术支持。 相似文献
92.
The solvent-dependent polymorphism of the active pharmaceutical ingredient (API) carbamazepine is interpreted from calculations of the solid-state and API-solvent intermolecular interactions. These simulations suggested that apolar solute-solute interactions could be disrupted by apolar solvents. In contrast, the polar solute-solute interactions were found to be easily disrupted by polar and protic solvents. This is consistent with experimental observations that the crystallization of the metastable form II is more dominant in apolar solvents. The Mercury program remains the gold standard in terms of usability; however, further expansion into more complex simulation techniques could make this package of even greater use in pharmaceutical manufacturing workflows. 相似文献
93.
94.
本文介绍ACS-15电子计价秤示值误差测量结果不确定度的评定方法,并通过实际测量,计算出7.5kg秤量点的标准不确定度、合成标准不确定度及扩展不确定度。 相似文献
95.
《Current Opinion in Solid State & Materials Science》2020,24(1):100797
This paper reviews recent studies, that not only includes both experiments and modeling components, but celebrates a close coupling between these techniques, in order to provide insights into the plasticity and failure of polycrystalline metals. Examples are provided of studies across multiple-scales, including, but not limited to, density functional theory combined with atom probe tomography, molecular dynamics combined with in situ transmission electron miscopy, discrete dislocation dynamics combined with nanopillars experiments, crystal plasticity combined with digital image correlation, and crystal plasticity combined with in situ high energy X-ray diffraction. The close synergy between in situ experiments and modeling provides new opportunities for model calibration, verification, and validation, by providing direct means of comparison, thus removing aspects of epistemic uncertainty in the approach. Further, data fusion between in situ experimental and model-based data, along with data driven approaches, provides a paradigm shift for determining the emergent behavior of deformation and failure, which is the foundation that underpins the mechanical behavior of polycrystalline materials. 相似文献
96.
When we speak about capacitance moisture meters for bulk materials we have to face with different values of dielectric permittivity for different bulk materials in dehydrated state, what causes a method error that can be named ‘type uncertainty’. Besides, different varieties of the same material have different values of dielectric permittivity, which depend from geographical origin, processing conditions etc. It can be hardly predicted automatically and type uncertainty can be compensated only in separate situations with the help of preliminary calibration. Main tasks of the research are to develop new comparison principle of moisture measurement with better accuracy due to effective compensation of physical, chemical and granulometric composition influence on the result of moisture measurement, develop new primary and secondary instrument transducers. Moisture sensor consists of four measuring capacitors. Two of them should be filled with a sample, which moisture content should be determined, and other pair of measuring capacitors should be filled with a same substance, but previously dehydrated. Mathematical models, developed to take into account granulometric composition of a bulk material were used to carry out a comparison analysis for three types of instrument measuring transducers. Obtained results proved that suggested principle of moisture measurement provides effective compensation of granulometric composition influence. Developed measuring principle had been experimentally tested what helped to confirm that it provides two times better compensation of different physical and chemical composition for different materials in comparison with the direct comparison method. 相似文献
97.
Jimmy Perdana Arantza Aguirre Zubia Oylum Kutahya Maarten Schutyser 《Drying Technology》2015,33(15-16):1789-1797
Shelf life of probiotic microorganisms can be retained by drying. Spray drying is an economically interesting alternative to freeze drying with that respect. However, the viability can decrease due to the drying process and testing it is laborious and expensive. This research shows that the viability of Lactobacillus plantarum WCFS1 during pilot scale drying can be predicted with kinetics gathered at a single droplet level. Using this approach, it could be demonstrated that the viability of L. plantarum WCFS1 during spray drying is mainly determined by the combination of temperature and moisture content during the first 0.5 seconds after atomization. The combination of a high moisture content and a high temperature appeared most detrimental to the residual viability. Moreover, it was found to be important to take into account the particle size distribution during atomization when predicting viability, since this has a large effect on the moisture content during this first 0.5 seconds. Finally, it was observed that shelf life during storage was mainly determined by the moisture content of the powder. A lower moisture content resulted in a higher viability. Above a moisture content of 6%, shelf life stability rapidly decreased in the applied maltodextrin (DE = 16) matrix. 相似文献
98.
Mathematical Modeling of a Simulated Moving‐Bed Adsorption Process: Parex™ Technology as a Case Study 下载免费PDF全文
Mahdi Rezazadeh Mohammad Seifi Esfahani Amir Rahimi Mohammad Reza Ehsani 《化学工程与技术》2015,38(5):759-768
A simplified dynamic mathematical model for a simulated moving‐bed adsorption process is presented. The model is adopted to simulate the separation process of p‐xylene from the other 8‐carbon aromatics by means of the Parex? technology. Operating conditions and the moving‐bed structure for a commercial plant were used and the performance of the unit was simulated. The model results are in good agreement with the findings of similar existing studies. Comparison of the results of this simplified model with those obtained by other researches indicates a considerable decrease in central processing unit (CPU) time. 相似文献
99.
Oscillating water column based wave energy extracting system has a low efficiency due to the poor performance of its principal power extracting component, the bidirectional turbine. In the present work, flow over a bidirectional impulse turbine was simulated using CFD technique and optimized using multiple surrogates approach. The surrogates being problem dependent may produce unreliable results, if a wrong surrogate is selected. Hence, multiple surrogates such as response surface approximation, radial basis function, Kriging and weighted average surrogates were incorporated in this problem. Same design points were used to generate multiple optima via multiple surrogates to enhance the robustness of the optimization process. Numbers of guide vanes and rotor blades were chosen as the design variables, and the objective was to maximize the blade efficiency. Reynolds-averaged Navier–Stokes equations were solved for analyzing the flow physics. The computed results were used to train the surrogates and find the optimal points via hybrid genetic algorithm. The surrogates were further applied to find the optimal flow parameters by changing flow velocity and turbine speed. The relative efficiency enhancement through our present approach was about 16%. Detailed methodologies, analysis of the results and surrogate applicability have been presented in this paper. 相似文献
100.