全文获取类型
收费全文 | 27171篇 |
免费 | 3256篇 |
国内免费 | 1923篇 |
专业分类
电工技术 | 1833篇 |
综合类 | 3165篇 |
化学工业 | 4367篇 |
金属工艺 | 1504篇 |
机械仪表 | 1990篇 |
建筑科学 | 3826篇 |
矿业工程 | 1087篇 |
能源动力 | 1448篇 |
轻工业 | 1152篇 |
水利工程 | 1627篇 |
石油天然气 | 1279篇 |
武器工业 | 316篇 |
无线电 | 2292篇 |
一般工业技术 | 3064篇 |
冶金工业 | 868篇 |
原子能技术 | 634篇 |
自动化技术 | 1898篇 |
出版年
2024年 | 141篇 |
2023年 | 453篇 |
2022年 | 786篇 |
2021年 | 882篇 |
2020年 | 1032篇 |
2019年 | 864篇 |
2018年 | 811篇 |
2017年 | 1120篇 |
2016年 | 1059篇 |
2015年 | 1161篇 |
2014年 | 1507篇 |
2013年 | 1794篇 |
2012年 | 1981篇 |
2011年 | 2034篇 |
2010年 | 1524篇 |
2009年 | 1589篇 |
2008年 | 1532篇 |
2007年 | 1804篇 |
2006年 | 1572篇 |
2005年 | 1327篇 |
2004年 | 1102篇 |
2003年 | 915篇 |
2002年 | 798篇 |
2001年 | 692篇 |
2000年 | 617篇 |
1999年 | 509篇 |
1998年 | 422篇 |
1997年 | 396篇 |
1996年 | 343篇 |
1995年 | 295篇 |
1994年 | 256篇 |
1993年 | 182篇 |
1992年 | 166篇 |
1991年 | 143篇 |
1990年 | 140篇 |
1989年 | 103篇 |
1988年 | 79篇 |
1987年 | 50篇 |
1986年 | 40篇 |
1985年 | 29篇 |
1984年 | 23篇 |
1983年 | 8篇 |
1982年 | 17篇 |
1981年 | 9篇 |
1980年 | 16篇 |
1979年 | 3篇 |
1973年 | 2篇 |
1965年 | 2篇 |
1959年 | 3篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
31.
本文讨论了在两个园柱体的环形狭缝中不可压缩流体的流动.在一定的假设下,运用流体力学方程和流体对柱体的作用方程,导出了附加质量和转动惯量、振动频率和衰减系数.并对文(1)中的某些结果进行了必要的修正. 相似文献
32.
K V S Rama Rao 《Bulletin of Materials Science》1993,16(6):491-499
Pseudobinary alloy, Tb0·27Dy0·73Fe2−δ
, belonging to C-15 cubic Laves phase having MgCu2-type structure, possesses large magnetostriction and high magnetomechanical coupling coefficient. The advantages of this
material over existing piezoelectric materials, particularly for SONAR applications, are highlighted. Recent results on the
influence of cobalt (Co) on magnetic and magnetomechanical properties of Tb0·27Dy0·73Fe2 are discussed. 相似文献
33.
C. Llopis F. Revents L. Batet C. Pretel I. Sol 《Nuclear Engineering and Design》2007,237(18):2014-2023
The Technical University of Catalonia (UPC) has been jointly working with the Asociación Nuclear Ascó-Vandellòs (ANAV) for a number of years in order to establish, qualify and use best estimate (BE) models for the reactors under the control of ANAV. ANAV is the consortium that is responsible for operation of the Ascó and Vandellòs-II reactors. The reactors are Westinghouse-design three-loop PWRs with an approximate electrical power of 1000 MW. The existing integral plant models for each plant are currently used for many different purposes among which are support of plant operation and control. Quite a number of studies have been done in order to improve both safety and plant competitiveness. Most of these dynamic analyses were carried out in relation to transients starting at nominal full power or at least, very close to full power. This paper develops a specific use of the Vandellòs-II plant model for operation and control support at low power involving new ranges of system actuation parameters. It also examines scenarios that are somewhat different from those typically analysed. The study starts showing the results of an assessment case, which is a start-up test and provides some additional qualification, and subsequently attempts to establish calculations to support both an improvement in feed water controls and to set up operating recommendations for low-load manual operation of feed water turbo-pump. Both results hopefully, will produce an outcome, which leads to an improvement in safety and reduces reactor trip probability. 相似文献
34.
A. Sergeev A. Semenov V. Trifonov B. Karasik G. Gol''tsman E. Gershenzon 《Journal of Superconductivity》1994,7(2):341-344
The thermal boundary resistance at the YBaCuO thin film/Al2O3 substrate interface was investigated. The transparency for thermal phonons incident on the interface as well as for phonons moving from the substrate was determined. We have measured a transient voltage response of current-biased films to continuously modulated radiation. The observed knee in the modulation frequency dependence of the response reflects the crossover from the diffusion regime to the contact resistance regime of the heat transfer across the interface. The values of transparency were independently deduced both from the phonon escape time and from the time of phonon return to the film which were identified with peculiarities in the frequency dependence. The results are much more consistent with the acoustic mismatch theory than the diffuse mismatch model.We are grateful to A. Elantev for helpful discussion. We acknowledge the financial support of the Russian Scientific Council on the HTS problem (Project No. 90462). 相似文献
35.
A spherical acoustic resonator was developed for measuring sound velocities in the gaseous phase and ideal-gas specific heats for new refrigerants. The radius of the spherical resonator, being about 5 cm, was determined by measuring sound velocities in gaseous argon at temperatures from 273 to 348 K and pressures up to 240 kPa. The measurements of 23 sound velocities in gaseous HFC-134a (1,1,1,2-tetrafluoroethane) at temperatures of 273 and 298 K and pressures from 10 to 250 kPa agree well with the measurements of Goodwin and Moldover. In addition, 92 sound velocities in gaseous HFC-152a (1,1-difluoroethane) with an accuracy of ±0.01% were measured at temperatures from 273 to 348 K and pressures up to 250 kPa. The ideal-gas specific heats as well as the second acoustic virial coefficients have been obtained for both these important alternative refrigerants. The second virial coefficients for HFC-152a derived from the present sound velocity measurements agree extremely well with the reported second virial coefficient values obtained with a Burnett apparatus.Paper dedicated to Professor Joseph Kestin. 相似文献
36.
Chestnuts were dehydrated by using a combined method of osmotic dehydration followed by air drying. Samples were osmotically pretreated with sucrose (60% w/w) and glucose (56% w/w) for 8 h, air-dried at temperatures of 45, 55, and 65°C, at a relative humidity of 30% and at a velocity of 2.7 m·s-1 and the experimental data of the drying kinetics were obtained. Whole samples were dried with different peelings: (a) removal of endocarp and pericarp (peeled) and (b) additionally the internal rough surface (cut). In all cases, cut chestnuts show greater drying rates than peeled samples, indicating that a significant mass transfer resistance in the layer nearest to the surface takes place. Peeled samples pretreated with sucrose solutions behave in a similar way to untreated samples. For the rest of the samples, the cut samples osmotically treated with sucrose solutions and all the samples treated with the glucose solution, the drying rates decrease during drying. Drying kinetics are successfully modeled by employing a diffusional model that takes the shrinkage into account. The effective coefficient of water diffusion was evaluated and correlated with temperature. The quality of the final product was monitored by color change. In spite of the fact that the total color difference is not modified by the osmotic treatment, the L*, a*, and b* color coordinates of cut samples treated with sucrose and glucose solutions do undergo changes; the L* and a* coordinates change less than the b*. 相似文献
37.
38.
39.
E.F. Thacher 《Energy Conversion and Management》1985,25(4):519-525
With the object of evaluating its importance to thermoelectric generator design, heat loss is introduced into the standard thermoelectric generator design theory. The theory for both the constant hot and cold junction temperatures model and the constant heat input model are so modified. The modification is first order and, therefore, is limited to small leg heat-transfer coefficients. Numerical results using representative properties show that significant differences can exist between the optimum geometry and performance of a generator idealized as lossless and those of a generator designed by the modified theory. The largest differences occur with the constant heat input model. 相似文献