全文获取类型
收费全文 | 1241篇 |
免费 | 84篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 8篇 |
综合类 | 5篇 |
化学工业 | 397篇 |
金属工艺 | 23篇 |
机械仪表 | 16篇 |
建筑科学 | 56篇 |
矿业工程 | 1篇 |
能源动力 | 23篇 |
轻工业 | 233篇 |
水利工程 | 15篇 |
石油天然气 | 3篇 |
无线电 | 52篇 |
一般工业技术 | 160篇 |
冶金工业 | 183篇 |
原子能技术 | 1篇 |
自动化技术 | 151篇 |
出版年
2023年 | 10篇 |
2022年 | 63篇 |
2021年 | 92篇 |
2020年 | 37篇 |
2019年 | 35篇 |
2018年 | 43篇 |
2017年 | 32篇 |
2016年 | 37篇 |
2015年 | 36篇 |
2014年 | 46篇 |
2013年 | 78篇 |
2012年 | 62篇 |
2011年 | 111篇 |
2010年 | 52篇 |
2009年 | 57篇 |
2008年 | 58篇 |
2007年 | 59篇 |
2006年 | 57篇 |
2005年 | 55篇 |
2004年 | 47篇 |
2003年 | 18篇 |
2002年 | 28篇 |
2001年 | 16篇 |
2000年 | 24篇 |
1999年 | 12篇 |
1998年 | 14篇 |
1997年 | 9篇 |
1996年 | 24篇 |
1995年 | 14篇 |
1994年 | 16篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1968年 | 3篇 |
1964年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有1327条查询结果,搜索用时 31 毫秒
81.
The effects of the operating conditions, the initial concentrations of marine diesel fuel (MDF) and the coexisting Pb in the soil, and the ethylene diamine tetra acetic salt (EDTA) in solution on MDF removal by sodium dodecyl sulfate (SDS) washing were extensively investigated with the aim of optimizing the process parameters and determining the MDF removal efficiency by SDS under different contamination conditions. The experimental results from batch tests indicated that the majority of MDF was removed by SDS in the first 2?h, and its optimal pH was nearly neutral. Increasing the SDS concentration linearly increased the MDF removal efficiency. At a given SDS concentration, the removal efficiency was dependent on the existing forms of MDF in soils, and the free phase of MDF was found to be more easily removed than the adsorbed phase. MDF removal by SDS was significantly reduced by the coexisting Pb in soils, which likely forms a complexation with SDS and thereby enhances the partitioning of MDF in the soil by the re-adsorption of released MDF onto the hydrophobic tails of the adsorbed SDS. EDTA alone, or with SDS, could remove MDF, but the remaining MDF in the contaminated soil after EDTA washing became more difficult to be removed by SDS. Therefore, the EDTA washing followed by SDS washing is not recommended for MDF removal. 相似文献
82.
Pepperberg Irene M.; Sandefer Robert M.; Noel Dawn A.; Ellsworth Clare P. 《Canadian Metallurgical Quarterly》2000,114(4):371
Grey parrots (Psittacus erithacus) learn referential English labels when they view and interact with 2 humans who model vocal labeling and who demonstrate referentiality and functionality of a label (I. M. Pepperberg, 1990a). To test if both trainers are necessary, the authors contrasted 2-trainer modeling with training by 1 human who presented targeted labels to a bird in concert with appropriate items, who asked questions, and who would reward attempts at the label with the item. The bird was also tutored by either 1 or 2 interactive humans in conjunction with a conspecific who already used referential labels. Referential labels were learned from multiple live tutors but not a single trainer. Presence of a conspecific enhanced learning compared with single-trainer sessions but did not affect acquisition in 2-human sessions. Specific aspects of paired tutoring seem critical for acquiring referential vocal labels. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
83.
Irene Ramos-Vielba Manuel Fernández-Esquinas Elena Espinosa-de-los-Monteros 《Scientometrics》2010,84(3):649-667
Studies of university–industry collaboration remain subject to important limitations due to the shortage of empirical data
and a lack of consistency in that obtained to date. This article puts into practice a set of universities Third Mission indicators
in a regional innovation system. Selected indicators previously compiled from literature were reorganized and pre-tested.
We have undertaken two face-to-face surveys of 737 firms and 765 heads of research teams, respectively. The results test the
validation of indicators and provide a complex map of university–industry linkages as well as some observations on the flexibility
needed to address this issue. 相似文献
84.
A rejoinder to "Psychotherapy research ethics: Continuing the debate on controlled clinical trials."
Imber Stanley D.; Glanz Lawrence M.; Elkin Irene; Sotsky Stuart M.; Boyer Jenny L.; Leber William R. 《Canadian Metallurgical Quarterly》1987,42(12):1132
Responds to C. A. Heflinger's (1987) critique of the present authors (1986) by reiterating their concern for the principle of autonomy. The present authors note that all patients were fully informed about the research plan and their right to withdraw. Nonetheless, the ethical criticism offered by Heflinger regarding randomization cannot be entirely dismissed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
85.
86.
Hall Gordon C. Nagayama; Bansal Anita; Lopez Irene R. 《Canadian Metallurgical Quarterly》1999,11(2):186
Meta-analyses were performed on 25 comparative Minnesota Multiphasic Personality Inventory (MMPI) and MMPI-2 studies of 1,428 male African Americans versus 2,837 male European Americans, 12 studies of 1,053 female African Americans versus 1,470 female European Americans, and 13 studies of 500 male Latino Americans and 1,345 male European Americans. Aggregate effect sizes suggest higher scores for ethnic minority groups than for European Americans on some MMPI/MMPI-2 scales and lower scores on others. However, none of the aggregate effect sizes suggest substantive differences from either a statistical or clinical perspective. The MMPI and MMPI-2 apparently do not unfairly portray African Americans and Latinos as pathological. Effect sizes across studies generally did not vary as a function of sociodemographic variables, research setting, or use of the MMPI versus MMPI-2. It is recommended that additional between- and within-ethnic groups psychopathology research continue. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
ABSTRACT A mathematical model of simultaneous mass, heat and momentum transfer for two-phase flow of a gas and a solid/liquid slurry was developed. The model was applied to calculation of the drying process of coal-water slurry droplets in a gas medium in a steady one-dimensional flow. The model was based on the well-known two-stage drying process for slurry droplets. After the first period of drying, in which the evaporation rate is controlled by the gas phase resistance, the evaporating liquid diffuses through the porous shell (crust) and then, by convection, into the gas medium. Inside the dry external crust of the drop, a wet central core forms, which shrinks as evaporation proceeds. The temperature of the slurry droplet rises. The process ends when the temperature of the dry outer crust reaches the coal ignition temperature in the case of combustion or when the moisture of the particle reaches the final required moisture. The developed model was based on one-dimensional balance equations of mass, energy and momentum for the liquid/solid and gas phases. The system of governing equations was represented by first-order differential equations and solved simultaneously. The numerical solution of the governing equations was obtained using Gear's method. The model permitted calculation 相似文献
88.
In this paper we consider Runge–Kutta discontinuous Galerkin (RKDG) schemes for Vlasov–Poisson systems that model collisionless plasmas. One-dimensional systems are emphasized. The RKDG method, originally devised to solve conservation laws, is seen to have excellent conservation properties, be readily designed for arbitrary order of accuracy, and capable of being used with a positivity-preserving limiter that guarantees positivity of the distribution functions. The RKDG solver for the Vlasov equation is the main focus, while the electric field is obtained through the classical representation by Green’s function for the Poisson equation. A rigorous study of recurrence of the DG methods is presented by Fourier analysis, and the impact of different polynomial spaces and the positivity-preserving limiters on the quality of the solutions is ascertained. Several benchmark test problems, such as Landau damping, the two-stream instability, and the Kinetic Electro static Electron Nonlinear wave, are given. 相似文献
89.
Interfaces between two dissimilar metals have been observed to exhibit a range of atomic structures, from atomically flat to atomically stepped. Using atomic-scale simulation and theory, we study the influence of the intrinsic bimetal interface structure on the nucleation of lattice dislocations. Interface structure is found to have a strong effect on which dislocations are nucleated and the type of nucleation site. We develop a theoretical model that provides criteria for predicting these effects based on key structural relationships between the interface and adjoining crystals. In recognition of these critical conditions, we construct a map that identifies the most likely nucleation site from a given interface. The theory and map developed here can guide efforts to tune interface structures for controlling the strength and deformation of heterogeneous materials. 相似文献
90.