全文获取类型
收费全文 | 1643篇 |
免费 | 109篇 |
国内免费 | 45篇 |
专业分类
电工技术 | 32篇 |
综合类 | 62篇 |
化学工业 | 565篇 |
金属工艺 | 25篇 |
机械仪表 | 39篇 |
建筑科学 | 98篇 |
矿业工程 | 9篇 |
能源动力 | 171篇 |
轻工业 | 94篇 |
水利工程 | 17篇 |
石油天然气 | 49篇 |
武器工业 | 9篇 |
无线电 | 45篇 |
一般工业技术 | 464篇 |
冶金工业 | 22篇 |
原子能技术 | 20篇 |
自动化技术 | 76篇 |
出版年
2024年 | 3篇 |
2023年 | 18篇 |
2022年 | 34篇 |
2021年 | 36篇 |
2020年 | 34篇 |
2019年 | 35篇 |
2018年 | 38篇 |
2017年 | 41篇 |
2016年 | 48篇 |
2015年 | 34篇 |
2014年 | 56篇 |
2013年 | 134篇 |
2012年 | 58篇 |
2011年 | 83篇 |
2010年 | 68篇 |
2009年 | 69篇 |
2008年 | 79篇 |
2007年 | 79篇 |
2006年 | 67篇 |
2005年 | 75篇 |
2004年 | 51篇 |
2003年 | 78篇 |
2002年 | 60篇 |
2001年 | 42篇 |
2000年 | 33篇 |
1999年 | 47篇 |
1998年 | 29篇 |
1997年 | 34篇 |
1996年 | 34篇 |
1995年 | 38篇 |
1994年 | 26篇 |
1993年 | 25篇 |
1992年 | 22篇 |
1991年 | 25篇 |
1990年 | 25篇 |
1989年 | 28篇 |
1988年 | 20篇 |
1987年 | 22篇 |
1986年 | 27篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有1797条查询结果,搜索用时 15 毫秒
61.
A thermodynamic property model with new mixing rules using the Helmholtz free energy is presented for the binary mixture of
methane and hydrogen sulfide based on experimental Pρ Tx data, vapor–liquid equilibrium data, and critical-point properties. The binary mixture of methane and hydrogen sulfide shows
vapor–liquid–liquid equilibria and a divergence of the critical curve. The model represents the existing experimental data
accurately and describes the complicated behavior of the phase equilibria and the critical curve. The uncertainty in density
calculations is estimated to be 2%. The uncertainty in vapor–liquid equilibrium calculations is 0.02 mole fraction in the
liquid phase and 0.03 mole fraction in the vapor phase. The model also represents the critical points with an uncertainty
of 2% in temperature and 3% in pressure. Graphical and statistical comparisons between experimental data and the available
thermodynamic models are discussed 相似文献
62.
An integrated system for the acquisition, normalisation and recognition of moving faces in dynamic scenes is introduced. Four face recognition tasks are defined and it is argued that modelling person-specific probability densities in a generic face space using mixture models provides a technique applicable to all four tasks. The use of Gaussian colour mixtures for face detection and tracking is also described. Results are presented using data from the integrated system. 相似文献
63.
Geoffrey M. Rowe Jay N. Meegoda Andris Jumikis Mark J. Sharrock Nishantha Bandara Chamil H. Hettiarachchi 《Canadian Metallurgical Quarterly》2004,130(6):924-934
Abstract: This paper describes the research funded by the New Jersey Department of Transportation to develop an automated technology to monitor segregation during construction of hot-mix asphalt concrete pavements. A Laser-based system was used to measure surface texture and to detect segregation. Two segregated test sections and a control test section were tested to evaluate the applicability of Laser texture method to detect and quantify segregation. Laser texture data were gathered from all three sections. Ratios of texture in segregated areas to that in nonsegregated areas were set as the basis for detection of different levels of segregation. By combining the level of segregation and extent of segregation, an AREA index was developed to determine the acceptability of a pavement section. Based on AREA index, pay adjustment factors were proposed to reduce the payment to account for loss of pavement life due to segregation. Further remedial actions were proposed to correct segregated pavement sections with acceptable AREA index. Based on the above concepts, Windows-based computer program NJTxtr was developed to detect and quantify segregation. This computer program uses the Laser-equipment-collected pavement texture data and determines whether the pavement section is acceptable or unacceptable based on the level of segregation within a pavement section, and provides bonus or penalties to the contractor. The paper describes a novel technology using laser and associated software for construction quality control of asphalt concrete pavements. The proposed methodology was applied to detect segregation in an interstate highway section in New Jersey, and this section was repaved based on visual observation and recommendation from this study. 相似文献
64.
Since the very first resolution of racemic tartaric acid by Pasteur, the importance of resolution and methodology has been on a path of continuous understanding and expansion. The science and chemistry of achieving such targets has changed a lot. The advent of chromatography changed the direction by involving synthetic, semisynthetic, or naturally occurring chiral materials for a direct approach to resolution, where rapid and reversible association occurs to form diastereomers with different stabilities and partition coefficients responsible for overall enantioseparation. It has now reached a stage where the separation of excess enantiomers from nonracemic mixtures has been achieved in a totally achiral environment, which does not appear to be in line with the prevalent concepts of basic stereochemistry. Caution should be exercised when enantiomerically enriched mixtures – obtained by enantioselective synthesis – are chromatographed for purification in preparative organic synthesis. 相似文献
65.
Direct Monte Carlo simulation of internal energies of departure for binary mixtures of geological interest are gathered and compared to those calculated using a linear mixing rule. Simulation results for gas–oil, oil–oil, and oil–water mixtures show that the linear mixing rule used in the Gibbs–Helmholtz Constrained (GHC) equation of state framework gives accurate approximations of binary mixture internal energies of departure. A flowchart for computing internal energies of departure using Monte Carlo simulation is included along with a sensitivity analysis for the GHC mixture energy parameter with respect to uncertainty in internal energies of departure. 相似文献
66.
67.
68.
69.
Zhou Liu Yuyan Zhang Chengliu Chen Tiyun Yang Jidong Wang Ling Guo Peng Liu Tiantian Kong 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(3)
Understanding the mechanical stability of granular‐armored liquid marbles is prerequisite for their applications including encapsulation, sensors, microreactions, and miniaturized liquid storage. Most liquid marbles are armored with agglomerated granular structure which complicates the wetting and interacting states of particles, hence, impeding one from understanding the effect of granular size on the mechanical stability of marbles. In this work, using a custom‐built platform to examine the liquid marbles armored by a single layer of uniform grains, it is revealed that larger microsized grains produce stronger liquid marble. This finding is attributed to the gravity‐induced capillary attraction which dominates the interaction of particles and provides additional tension to the granular network of the marble surface, which enhances the mechanical stability of marbles. In addition, different granular network structures are formed at the marble surface by using a binary mixture of monodisperse grains, and their effect on the mechanical stability of marbles is explored. The understandings offer important insights for application involving liquid marbles and provides guideline to formulate robust marble‐based products. 相似文献
70.
The identification of welded tubes properties considering the weld bead and Heat Affected Zone (HAZ) is important for reliable and accurate finite element simulation of tubular plastic forming processes such as tube hydroforming and rotary draw bending processes. Therefore, a simplified method is proposed to extract the weld bead and HAZ properties. Full size standard tensile specimens cut from the welded tube and comprising the weld parallel to the load direction are extended to failure. Mechanical properties obtained from uniaxial tensile test are correlated with the microhardness data measured across the welded specimen and by using the rule of mixtures; the constitutive model parameters of weld bead and HAZ regions are identified. Accuracy of the proposed method is assessed by comparing finite element simulation predictions to experimental measurements obtained from two mechanical tests: the first one is the uniaxial tensile test performed on specimens comprising the weld line perpendicular to the loading direction and the second test is the free bulge hydroforming test achieved on seamed tubular samples. This investigation has shown that the presented method is practical in use and sufficiently accurate to extract the weld metal properties of seamed tubes. 相似文献