全文获取类型
收费全文 | 166719篇 |
免费 | 68646篇 |
国内免费 | 45670篇 |
专业分类
电工技术 | 27110篇 |
综合类 | 20483篇 |
化学工业 | 20513篇 |
金属工艺 | 24339篇 |
机械仪表 | 5375篇 |
建筑科学 | 10802篇 |
矿业工程 | 12534篇 |
能源动力 | 7846篇 |
轻工业 | 19168篇 |
水利工程 | 7062篇 |
石油天然气 | 11750篇 |
武器工业 | 3485篇 |
无线电 | 27960篇 |
一般工业技术 | 27521篇 |
冶金工业 | 5716篇 |
原子能技术 | 1115篇 |
自动化技术 | 48256篇 |
出版年
2024年 | 1823篇 |
2023年 | 4096篇 |
2022年 | 4308篇 |
2021年 | 4765篇 |
2020年 | 8094篇 |
2019年 | 17684篇 |
2018年 | 19089篇 |
2017年 | 20427篇 |
2016年 | 20172篇 |
2015年 | 18860篇 |
2014年 | 17360篇 |
2013年 | 16310篇 |
2012年 | 15399篇 |
2011年 | 11649篇 |
2010年 | 10632篇 |
2009年 | 7643篇 |
2008年 | 5714篇 |
2007年 | 5191篇 |
2006年 | 4255篇 |
2005年 | 4053篇 |
2004年 | 7164篇 |
2003年 | 5857篇 |
2002年 | 5572篇 |
2001年 | 4875篇 |
2000年 | 4484篇 |
1999年 | 4269篇 |
1998年 | 3928篇 |
1997年 | 3505篇 |
1996年 | 3340篇 |
1995年 | 3399篇 |
1994年 | 2807篇 |
1993年 | 2634篇 |
1992年 | 2557篇 |
1991年 | 1848篇 |
1990年 | 1444篇 |
1989年 | 1364篇 |
1988年 | 1032篇 |
1987年 | 302篇 |
1986年 | 259篇 |
1985年 | 196篇 |
1984年 | 129篇 |
1982年 | 139篇 |
1981年 | 144篇 |
1978年 | 97篇 |
1976年 | 225篇 |
1975年 | 203篇 |
1972年 | 235篇 |
1971年 | 127篇 |
1969年 | 97篇 |
1960年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
992.
用自蔓燃高温合成(SHS)技术及电弧熔融法制备的(Nb,Ti)C固溶体作基体,制备(Nb,Ti)C-35Ni金属陶瓷。结果表明用电弧熔融法制备的(Nb,Ti)C为基的试样具较优的室温力学性能(σ=1630MPa,KIC=18.0MPa),其陶瓷颗粒均匀分行粘结相之中并是包裹结构;而用SHS法制备的(Nb,Ti)C为基的试样其力学性能相对较差,其陶瓷颗粒无包裹结构. 相似文献
993.
Early trials and analysis of a new adhesion test are discussed. The test is designed for measuring the adhesion of paint to
deformable steel sheets as used in building, automotive, and other cladding applications, and does not require detailed knowledge
of the paint mechanical properties. A stiff overlay, such as an epoxy resin, is applied to the coating, and the steel substrate
is peeled away using a roll of well-defined radius to which the steel substrate is constrained. The propagation of a crack
within the paint or at some interface in the paint/metal system depends mostly on the mechanical properties and thickness
of the overlay and the radius of the constraining roll. The test is shown to discriminate better than existing practical adhesion
tests between paints of expected differing adhesion/cohesion, but also presents some inconsistencies that require further
work to resolve.
BHP Institute of Steel Processing and Products, Wollongong NSW 2522, Australia. 相似文献
994.
Joannie W. Chin Eric Byrd Ned Embree Jonathan Martin J. D. Tate 《Journal of Coatings Technology》2002,74(929):39-44
Laboratory ultraviolet (UV) chambers are widely used to obtain weathering data for a wide range of commercial polymer products
including coatings, textiles, elastomers, plastics, and polymeric composites. Although numerous improvements have been made
in the design of UV chambers over the last 80 years, the reproducibility of the exposure results from these chambers has remained
elusive. This lack of reproducibility is attributed to systematic errors in their design, operation, and control which prevent
direct comparisons of the performance of materials exposed in the same environment, comparisons of the performance of the
same material exposed in different laboratories, and the comparison of field and laboratory results. This paper describes
an innovative UV chamber design based on integrating sphere technology that greatly reduces the magnitude of these errors,
as well as provides additional experimental capabilities.
Presented at the 79th Annual Meeting of the Federation of Societies for Coatings Technology, on November 4–7, 2001, in Atlanta,
GA.
Building Materials Division. Gaithersburg, MD.
Freeport, TX. 相似文献
995.
On the mechanical behavior of aluminum alloys reinforced by long or short alumina fibers or SiC whiskers 总被引:2,自引:0,他引:2
This study was initiated to examine the dispersion of longitudinal and transverse waves in metal matrix composites in order to obtain the dynamic elastic modulus and to evaluate various models for predicting the composite's macroscopic elastic constants from the properties of its constituents. The materials chosen for this investigation were alumina continuous fibers on the one hand and alumina and SiC short fibers on the other hand, all embedded in an aluminum alloy matrix. In addition, some indications have been obtained experimentally for the acoustoelastic effect in the composite. 相似文献
996.
从BTT-固冲导弹的特点:固冲发动机、导弹外形及控制系统具有强耦合的性质出发,分析了相互影响因素及建立计算模型时的特点。提出了一种BTT-固冲导弹总体一体化设计方法。 相似文献
997.
为深入了解木霉转化子的抗药性,对哈茨木霉及其转化子在PDA培养基上进行平板点植培养和小室培养,其菌体形态于40倍显镜镜下观察,结果显示,转化子的菌落形、菌丝形状、菌丝横隔间隔、孢子颜色、产孢数量均发生一定变化。对传代3年转化子抗药性的测定结果表明,哈茨木霉野生菌在多菌灵质量浓度度为1.0μg/mL时不能生长,而其转化子在多菌灵质量浓度高达1000.0μg/mL时仍能正常生长,说明此转化仍具抗药性且抗药性稳定。 相似文献
998.
Insights into soot formation processes are gained from chemical sampling and thermocouple probing of co-flowing inverse diffusion flames (IDFs), with the oxidizer in the center. The transition from near-to slightly sooting flames and the effects of flame temperature, fuel concentration, and fuel structure (using methane, ethene, propene and 1-butene) are investigated. The aromatic content of IDFS scales with the fuel's sooting tendency, and suggests that the formation of the aromatic ring is a controlling step in soot formation. In addition to the relatively well-established reactions involving C4 and C2 species, benzene may form directly from two C3 species for fuels that readily produce C3 species during pyrolysis and/or oxidative pyrolysis. The total concentration of growth species increases almost linearly with fuel concentration, but depends more weakly on flame temperature than would be expected if pure pyrolysis governed the intermediate hydrocarbon behavior. 相似文献
999.
分布系统中多米诺效应的分析与消除 总被引:3,自引:0,他引:3
分布系统中发生故障后,错误信息在进程间的传播,以及由此引起的系统恢复过程中的多米诺效应是分布系统容错恢复技术所面临的最重要与最困难的问题.目前各种研究工作偏重于具体的系统动态恢复技术.本文的研究重点在于首次揭示多米诺效应本身固有的数量特征及其与分布系统技术参数间的联系,给出多米诺效应动态消除技术,引入系统额外开销的下限,并针对动态技术的缺点,探讨多米诺效应的静态消除技术,为解决困难开辟新途径. 相似文献
1000.
The deformation behavior of several single- and two-phase coarse microstructures has been examined using microhardness measurements.
It has been found that the strength response of a coarse phase in isolation is distinctly different from its response when
it exists in a two-phase system. The second phase alters the mechanical state of the first one andvice versa even in the plastically undeformed condition. This phenomenon is explained in terms of the existence of an appreciable amount
of residual stresses in two-phase coarse microstructures. These stresses primarily arise due to the difference in thermal
expansion coefficients of the phases. The in- fluence of elastic stress field on microhardness response is shown with a new
type of experiment to support the proposed explanation. The present results question the existing expressions for deformation
modeling of multiphase materials because of the uncertainties in the estimation of the average strength of the phases in a
two-phase system. 相似文献