全文获取类型
收费全文 | 2043篇 |
免费 | 33篇 |
国内免费 | 46篇 |
专业分类
电工技术 | 27篇 |
综合类 | 68篇 |
化学工业 | 439篇 |
金属工艺 | 184篇 |
机械仪表 | 154篇 |
建筑科学 | 134篇 |
矿业工程 | 62篇 |
能源动力 | 285篇 |
轻工业 | 32篇 |
水利工程 | 5篇 |
石油天然气 | 43篇 |
武器工业 | 7篇 |
无线电 | 108篇 |
一般工业技术 | 283篇 |
冶金工业 | 34篇 |
原子能技术 | 41篇 |
自动化技术 | 216篇 |
出版年
2024年 | 5篇 |
2023年 | 48篇 |
2022年 | 69篇 |
2021年 | 78篇 |
2020年 | 55篇 |
2019年 | 46篇 |
2018年 | 62篇 |
2017年 | 47篇 |
2016年 | 41篇 |
2015年 | 32篇 |
2014年 | 80篇 |
2013年 | 153篇 |
2012年 | 79篇 |
2011年 | 137篇 |
2010年 | 82篇 |
2009年 | 104篇 |
2008年 | 146篇 |
2007年 | 107篇 |
2006年 | 98篇 |
2005年 | 82篇 |
2004年 | 67篇 |
2003年 | 111篇 |
2002年 | 68篇 |
2001年 | 32篇 |
2000年 | 48篇 |
1999年 | 24篇 |
1998年 | 33篇 |
1997年 | 31篇 |
1996年 | 28篇 |
1995年 | 24篇 |
1994年 | 21篇 |
1993年 | 13篇 |
1992年 | 20篇 |
1991年 | 16篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有2122条查询结果,搜索用时 15 毫秒
31.
V. A. Cherenkov 《Journal of Superconductivity》1991,4(4):259-261
The superconducting transition temperature of multilayered superconducting structures of the RVB theory for the S-N(D)-S type is defined taking into account the resonance pair tunneling between superconducting layers. The Josephson array defectivity is considered with the frustration parameters. 相似文献
32.
着重研究了马克思主义执政党建设如何应对当代世界政党政治的执政文化转型问题,认为应当正确认识和处理马克思主义执政党建设与当代世界政党政治的关系,深入研究世界上其他执政党治国理政的成功经验和有益做法,不断提高马克思主义执政党的执政能力和科学化水平。 相似文献
33.
Jason P. Petti 《Engineering Fracture Mechanics》2005,72(1):91-120
This work proposes that the Weibull stress scale parameter, σu, increases with temperature to reflect the increasing microscale toughness of ferritic steels caused by local events that include plastic shielding of microcracks, microcrack blunting, and microcrack arrest. The Weibull modulus, m, then characterizes the temperature invariant, random distribution of microcrack sizes in the material. Direct calibration of σu values at temperatures over the DBT region requires extensive sets of fracture toughness values. A more practical approach developed here utilizes the so-called Master Curve standardized in ASTM Test Method E1921-02 to provide the needed temperature vs. toughness dependence for a material using a minimum number of fracture tests conducted at one temperature. The calibration procedure then selects σu values that force the Weibull stress model to predict the Master Curve temperature dependence of KJc values for the material. At temperatures in mid-to-upper transition, the process becomes more complex as fracture test specimens undergo gradual constraint loss and the idealized conditions of high-constraint, small-scale yielding assumed in E1921-02 gradually degenerate. The paper develops the σu calibration process to incorporate these effects in addition to consideration of threshold toughness effects and the testing of fracture specimens with varying crack-front lengths. Initial illustrations of the calibration process for simpler conditions, i.e. 1T crack-front lengths, use the temperature dependent flow properties and a range of toughness levels for an A533B pressure vessel steel. Then using the extensive fracture toughness data sets for an A508 pressure vessel steel generated recently by Faleskog et al. [Engng. Fract. Mech., in press], the paper concludes with calibrations of both m and σu over the DBT region and assessments of the Master Curve calibration approach developed here. 相似文献
34.
同步和异步时序逻辑电路统一设计的新方法 总被引:3,自引:0,他引:3
张继军 《计算机工程与应用》2003,39(17):136-138,152
介绍了一种新的时序电路的设计理论与方法,实现了同步、异步电路的设计过程的统一。该方法的特点是直接从时序电路的状态转换图(STD)获得触发器的激励条件和时钟脉冲;设计原理简单,易于理解,使设计更直观清楚,比传统方法简便、快捷,避免了对状态方程、驱动方程的复杂计算;该设计方法过程可以采用程序实现,实现了时序电路设计的程序化、自动化。 相似文献
35.
Criteria for calculation of the concentration–temperature domain of use of ice slurries are defined, which allows establishing a temperature–concentration chart relating the temperature and the antifreeze mass fraction. It is shown that the shape of the chart depends only on the thermodynamic properties (heat capacity, ice–liquid equilibrium, etc.) of the diluted substance. 相似文献
36.
TES microcalorimeter readout via transformer 总被引:1,自引:0,他引:1
Vitali Sushkov 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2004,530(3):234-250
Readout configuration for Transition Edge Sensor (TES) electrically coupled to a low noise warm front-end via transformer is studied. The study was aimed at the implementation of the readout involved in imaging with microcalorimeter detector arrays using frequency multiplexing technique (Appl. Phys. Lett. 81(1) (2002) 159). A model describing both TES electrothermal reaction and the readout response is investigated. Contribution of electronic noise to TES energy resolution is calculated. Prospective readout architecture with TES electrical biasing from the warm readout side is introduced. The architecture allows building of large imaging detector arrays with TES. It is shown that an unprecedented combination of imaging and spectrometry features can be achieved with TES readout via transformer. 相似文献
37.
Transitions between plant species assemblages are often continuous with the form of the transition dependent on the ‘slope’ of environmental gradients and on the style of self-organization in vegetation. Image segmentation can present misleading or even erroneous results if applied to continuous spatial changes in vegetation. Even methods that allow for multiple-class memberships of pixels presuppose the existence of ideal types of species assemblages that constitute mixtures—an assumption that does not fit the case of continua where any section of a gradient is as ‘pure’ as any other section like in modulations of grassland species composition.Thus, we attempted to spatially model floristic gradients in Bavarian meadows by extrapolating axes of an unconstrained ordination of species data. The models were based on high-resolution hyperspectral airborne imagery. We further modelled the distribution of plant functional response types (Ellenberg indicator values) and the cover values of selected species. The models were made with partial least squares (PLS) regression analyses. The realistic utility of the regression models was evaluated by full leave-one-out cross-validation.The modelled floristic gradients showed a considerable agreement with ground-based observations of floristic gradients (R2=0.71 and 0.66 for the first two axes of ordination). Apart from mapping the most important continuous floristic differences, we mapped gradients in the appearance of plant functional response groups as represented by averaged Ellenberg indicator values for soil pH (R2=0.76), water supply (R2=0.66) and nutrient supply (R2=0.75), while models for the cover of single species were weak.Compared to many other vegetation attributes, plant species composition is difficult to detect with remote sensing techniques. This is partly caused by a lack of compatibility between methods of vegetation ecology and remote sensing. We believe that the present study has the potential to increase compatibility as neither spectral nor vegetation information gets lost by a classifying step. 相似文献
38.
In this paper, a recursive formulation for generating the equations of motion of spatial mechanical systems is presented.
The rigid bodies are replaced by a dynamically equivalent constrained system of particles which avoids introducing any rotational
coordinates. For the open-chain system, the equations of motion are generated recursively along the serial chains using the
concepts of linear and angular momenta. Closed-chain systems are transformed to open-chain systems by cutting suitable kinematic
joints and introducing cut-joint constraints. The formulation is used to carry out the dynamic analysis of multi-link five-point
suspension. The results of the simulation demonstrate the generality and simplicity of the proposed dynamic formulation. 相似文献
39.
R. A. Stern A. Rausch S. Deiker D. Martínez-Galarce L. Shing K. D. Irwin J. N. Ullom G. O’Neil G. Hilton L. Vale 《Journal of Low Temperature Physics》2008,151(3-4):721-726
LMSAL and NIST are developing position-sensitive X-ray strip detectors based on TES microcalorimeter arrays for solar physics.
An important application of these devices will be the study of high temperature (>10 MK) X-ray lines, e.g. Fe XXV, at high
spectral (E/ΔE≥1000) and temporal (sub-ms) resolution. Diagnostics from these lines will provide significant new insights into the physics
of microflares and the early stages of flares. In this paper, we will describe the current status of our laboratory test program
and applicability of our research to future space missions
相似文献
40.