全文获取类型
收费全文 | 517篇 |
免费 | 22篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 121篇 |
金属工艺 | 16篇 |
机械仪表 | 10篇 |
建筑科学 | 15篇 |
能源动力 | 14篇 |
轻工业 | 24篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 50篇 |
一般工业技术 | 134篇 |
冶金工业 | 78篇 |
原子能技术 | 6篇 |
自动化技术 | 67篇 |
出版年
2023年 | 7篇 |
2022年 | 14篇 |
2021年 | 21篇 |
2020年 | 7篇 |
2019年 | 7篇 |
2018年 | 19篇 |
2017年 | 23篇 |
2016年 | 29篇 |
2015年 | 12篇 |
2014年 | 28篇 |
2013年 | 46篇 |
2012年 | 25篇 |
2011年 | 28篇 |
2010年 | 20篇 |
2009年 | 33篇 |
2008年 | 24篇 |
2007年 | 17篇 |
2006年 | 18篇 |
2005年 | 18篇 |
2004年 | 5篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 7篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有541条查询结果,搜索用时 250 毫秒
1.
Ponnusamy Nandha Kumar Shangavi Subramanian Uthirapathy Vijayalakshmi Sanjeevi Kannan 《Journal of the American Ceramic Society》2020,103(6):3528-3540
Structurally stable β-Ca3(PO4)2/t-ZrO2 composite mixtures with the aid of Dy3+ stabilizer were accomplished at 1500°C. The precursors comprising Ca2+, P5+, Zr4+, and Dy3+ have been varied to obtain five different combinations. The results revealed the fact that complete phase transformation of calcium-deficient apatite to β-Ca3(PO4)2 occurred only at 1300°C, whereas the evidence of t-ZrO2 crystallization is obvious at 900°C. The dual occupancy of Dy3+ at β-Ca3(PO4)2 and t-ZrO2 structures was evident; however, Dy3+ initially prefers to occupy β-Ca3(PO4)2 lattice until its saturation limit and thereafter accommodates at the lattice site of ZrO2. The typical absorption and emission behavior of Dy3+ were noticed in all the systems and, moreover, the surrounding symmetry of Dy3+ domains has been determined from the luminescence study. All the systems ensured paramagnetic response that is generally contributed by the presence of Dy3+. A gradual increment in the phase content of t-ZrO2 in the composite mixtures ensured a significant improvement in the hardness and Young's modulus of the investigated compositions. 相似文献
2.
V. Thomas Paul S. Saroja P. Hariharan A. Rajadurai M. Vijayalakshmi 《Journal of Materials Science》2007,42(14):5700-5713
This paper presents the results of a study on the microstructural and microchemical variations in a multipass Gas Tungsten
Arc weld (GTAW) of modified 9Cr-1Mo steel. The changes brought about in the steel due to the heating and cooling cycles during
welding and the subsequent effects due to reheating effects during multipass welding are described. Detailed analytical transmission
electron microscopy has been carried to study the type and composition of the primary and secondary phases in this steel.
The systematic changes in microstructural parameters such as Prior Austenite Grain Size, martensite lath size, number density,
size and microchemistry of carbides, have been understood based on the different transformations that the steel undergoes
during the heating and cooling process. Based on the observed microstructure, an attempt has been made to identify distinct
microstructural zones and possible thermal cycles experienced by different regions of the weldment. 相似文献
3.
Hyun-Ho Choi Sang-Yoon Lee Il-Yoon Choi Hyo-Nam Cho Sankaran Mahadevan 《Reliability Engineering & System Safety》2006,91(6):674-688
Until now, in many forensic reports, the failure cause assessments are usually carried out by a deterministic approach so far. However, it may be possible for the forensic investigation to lead to unreasonable results far from the real collapse scenario, because the deterministic approach does not systematically take into account any information on the uncertainties involved in the failures of structures.Reliability-based failure cause assessment (reliability-based forensic engineering) methodology is developed which can incorporate the uncertainties involved in structural failures and structures, and to apply them to the collapsed bridge in order to identify the most critical failure scenario and find the cause that triggered the bridge collapse. Moreover, to save the time and cost of evaluation, an algorithm of automated event tree analysis (ETA) is proposed and possible to automatically calculate the failure probabilities of the failure events and the occurrence probabilities of failure scenarios. Also, for reliability analysis, uncertainties are estimated more reasonably by using the Bayesian approach based on the experimental laboratory testing data in the forensic report. For the applicability, the proposed approach is applied to the Hang-ju Grand Bridge, which collapsed during construction, and compared with deterministic approach. 相似文献
4.
5.
6.
7.
Acceleration and sound measurements during granular discharge from silos are used to show that silo music is a sound resonance produced by silo quake. In tall and narrow silos, the latter is produced by stick-slip friction between the wall and the granular material. For the discharge rates studied, the occurrence of flow pulsations is determined primarily by the surface properties of the granular material and the silo wall. The measurements show that the pulsating motion of the granular material drives the oscillatory motion of the silo. 相似文献
8.
Peida Xu Xiaoyan Su Sankaran Mahadevan Chenzhao Li Yong Deng 《Applied Intelligence》2014,41(3):681-693
As an important tool for knowledge representation and decision-making under uncertainty, Dempster-Shafer evidence theory (D-S theory) has been used in many fields. The application of D-S theory is critically dependent on the availability of the basic probability assignment (BPA). The determination of BPA is still an open issue. A non-parametric method to obtain BPA is proposed in this paper. This method can handle multi-attribute datasets in classification problems. Each attribute value of the dataset sample is treated as a stochastic quantity. Its non-parametric probability density function (PDF) is calculated using the training data, which can be regarded as the probability model for the corresponding attribute. The BPA function is then constructed based on the relationship between the test sample and the probability models. The missing attribute values in datasets are treated as ignorance in the framework of the evidence theory. This method does not have the assumption of any particular distribution. As a result, it can be flexibly used in many engineering applications. The obtained BPA can avoid high conflict between evidence, which is desired in data fusion. Several benchmark classification problems are used to demonstrate the proposed method and to compare against existing methods. The constructed classifier based on the proposed method compares well to the state-of-the-art algorithms. 相似文献
9.
In an attempt to toughen the epoxy resin matrix for fiber-reinforced composite applications, a chemical modification procedure of a commercially available bisphenol-A-based epoxy resin using reactive liquid rubber HTBN [hydroxy-terminated poly(butadiene-co-acrylonitrile)] and TDI (tolylene diisocyanate) is described. The progress of the reaction and the structural changes during modification process are studied using IR spectroscopy, viscosity data, and chemical analysis (epoxy value determination). The studies support the proposition that TDI acts as a coupling agent between the epoxy and HTBN, forming a urethane linkage with the former and an oxazolidone ring with the latter. The chemical reactions that possibly take place during the modification are discussed. 相似文献
10.
Syntactic foam slabs having uncoated microballoons and paraffin oil surface‐treated microballoons were fabricated and tested for short‐beam three‐point bend test. The work points to the role of paraffin oil coating first weakening the interface between the microballoons and the matrix and hence lowering the efficiency of load transfer from matrix to the fillers (i.e., microballoons). This led to an overall decrement of 71% in the experimentally measured strength value compared to the deduced value for uncoated microballoons' specimens. The large strengths for uncoated microballoons specimens can be traced to the presence of the curvilinear marks in the matrix that, incidentally, are absent in the case of paraffin oil coated specimens. These observations are revealed distinctly in the microscopy of test‐failed specimens. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 687–693, 2005 相似文献