全文获取类型
收费全文 | 737篇 |
免费 | 27篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 19篇 |
综合类 | 2篇 |
化学工业 | 169篇 |
金属工艺 | 13篇 |
机械仪表 | 18篇 |
建筑科学 | 15篇 |
矿业工程 | 2篇 |
能源动力 | 22篇 |
轻工业 | 48篇 |
水利工程 | 9篇 |
无线电 | 75篇 |
一般工业技术 | 212篇 |
冶金工业 | 81篇 |
原子能技术 | 9篇 |
自动化技术 | 75篇 |
出版年
2024年 | 6篇 |
2023年 | 8篇 |
2022年 | 14篇 |
2021年 | 29篇 |
2020年 | 30篇 |
2019年 | 30篇 |
2018年 | 28篇 |
2017年 | 26篇 |
2016年 | 16篇 |
2015年 | 12篇 |
2014年 | 26篇 |
2013年 | 51篇 |
2012年 | 31篇 |
2011年 | 42篇 |
2010年 | 29篇 |
2009年 | 33篇 |
2008年 | 29篇 |
2007年 | 28篇 |
2006年 | 30篇 |
2005年 | 34篇 |
2004年 | 17篇 |
2003年 | 15篇 |
2002年 | 19篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 14篇 |
1997年 | 12篇 |
1996年 | 16篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 13篇 |
1990年 | 2篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有769条查询结果,搜索用时 15 毫秒
41.
Pradhan AS 《Radiation protection dosimetry》2002,101(1-4):173-178
X and gamma rays continue to remain the main contributors to the dose to humans. As these photons of varying energies are encountered in various applications, the study of photon energy response of a dosemeter is an important aspect to ensure the accuracy in dose measurement. Responses of dosemeters have to be experimentally established because for luminescence dosemeters, they depend not only on the effective atomic number (ratio of mass energy absorption coefficients of dosemeter and tissue) of the detector, but also considerably on the luminescence efficiency and the material surrounding the dosemeters. Metal filters are generally used for the compensation of energy dependence below 200 keV and/or to provide photon energy discrimination. It is noted that the contribution to Hp(0.07) could be measured more accurately than Hp(10). For the dosemeters exhibiting high photon energy-dependent response, estimation of the beta component of Hp(0.07) becomes very difficult in the mixed field of beta radiation and photons of energy less than 100 keV. Recent studies have shown that the thickness and the atomic number of metal filters not only affect the response below 200 keV but also cause a significant over-response for high energy (>6 MeV) photons often encountered in the environments of pressurised heavy water reactors and accelerators. 相似文献
42.
AJ Chohan AD Kugelmass M Kida LR Pennington CA Sivaram 《Canadian Metallurgical Quarterly》1998,14(3):463-465
A cardiac transplant recipient with multiple coronary artery fistulae draining into the right ventricle is described. These fistulae presumably resulted from repeated endomyocardial biopsies. The diagnosis of coronary artery fistulae was made at the annual coronary arteriography. The magnitude of the shunt remained small over eight years of follow-up. 相似文献
43.
44.
Xing Fang David B. Thompson Theodore G. Cleveland Pratistha Pradhan 《Canadian Metallurgical Quarterly》2007,133(4):314-322
Time of concentration (Tc) is the time required for runoff to travel from the hydraulically most distant point to the outlet of a watershed. The Natural Resources Conservation Service (NRCS) velocity method commonly is used to estimate Tc for hydrologic analysis and design. The NRCS velocity method applies the physical concept that travel time is a function of runoff flow length and flow velocity. Time of concentration for 96 Texas watersheds is independently estimated by three research teams using the NRCS velocity method. Drainage areas of the 96 watersheds considered in the study are approximately 0.8–440.3?km2 (0.3–170?mi2). Digital elevation models having a grid size of 30?m were used to derive watershed physical characteristics using ArcGIS or HEC-GeoHMS. Average channel width was estimated from 1?m or 1?ft digital orthoimagery quarter quadrangle or aerial photography. Each team made independent decisions to estimate parameters needed for different flow segments for the NRCS velocity method. Estimates of time of concentration made by three research teams are compared, and both graphic comparison and statistical summary demonstrate that time of concentration estimated using the NRCS velocity method is subject to large variation, dependent on the analyst-derived parameters used to estimate flow velocity. Because of the propensity for different analysts to arrive at different results, caution is required in application of the NRCS velocity method to estimate Tc. 相似文献
45.
Anu R. Pradhan Debra F. Laefer William J. Rasdorf 《Canadian Metallurgical Quarterly》2007,21(2):90-101
A three-tiered, enterprise, geographic information system architecture offers a robust, efficient, and secure platform to potentially revolutionize disaster management by enabling support of all of the phases of governmental activity that must occur before, during, and after a disaster. Presently, both publicly and privately initiated, computer-based systems designed for disaster management cannot meet the real-time data access and analysis needs at crucial stages, especially those occurring during an actual disaster. Impediments are reflective of the proprietary, stand alone, and segregated nature of current systems. This paper proposes an integrated, infrastructure management information system as a reliable and effective alternative. Issues related to sharing data, customizing applications, supporting multiple data formats, querying visually, facilitating ubiquitous computing, and upgrading are all addressed. Achieving maximum flexibility and capacity in a disaster management system relies upon recent advances in the following areas: (1) standardized data specifications; (2) middleware services; and (3) Web-enabled, distributed computing. Key resources in designing and implementing such an arrangement are prototyped in a system that was initially designed for addressing disaster management of urban explosions. The critical details of that system are presented herein. 相似文献
46.
AgInSe2 (AIS) films were grown on n-type Si substrates by the ultra-high-vacuum pulsed laser deposition technique from the AIS target synthesized from high-purity materials. The X-ray diffraction and microscopic studies of the films show that films are textured having terrace-like surface morphology. The optical studies of the films show that the optical band gap is about 1.24 eV. The electrical conductivity of AgInSe2/Si films shows excellent diode characteristics. The photoconductivity of the AgInSe2/Si device shows photocurrent of 2.8 mA at a bias-voltage of − 1 V with an open circuit voltage of 0.15 V. This shows that AIS films are very good absorber material for solar cell technology. 相似文献
47.
Empirical studies in software engineering can involve a variety of organizations, each with their own set of policies and procedures geared at safeguarding the interests and responsibilities of the researchers, students, the collaborating company, the university, and possibly national funding agencies like the National Science Foundation and the National Institute of Health. Each of these organizations have differing goals for participating in these studies and bring widely different cultures and expectations to the table. While policies, procedures, contracts, and agreements set expectations, they by themselves cannot ensure ethical behavior. This position paper describes some of the common approaches to encourage ethical behavior and their limits for enforcing ethical behavior. 相似文献
48.
In the above-named work (see ibid., vol.38, p.51-7, April 1989), S. Lafiti and A. El-Amawy apply, in a straightforward manner, the method developed by A.D. Singh (1985) to calculate lower bounds for the yield of nonplanar interstitial redundancy topologies of processor arrays with spare processors. In their introduction, they claim that the models suggested by I. Koren and D.K. Pradhan (1987) are highly theoretical since the number of states in the Markov model might be very large and the determination of the transition rates might be intractable. They add that applying some empirical rules, as suggested by Koren and Pradhan (1987), can lead to unrealistic results and may require a large number of computations. They also claim that the model of Koren and Pradhan does not suggest an algorithm to replace faulty elements. They conclude that a simpler model, like the one proposed by Singh, is needed for calculating the yield of fault-tolerant processor arrays. In the present comment, Koren and Pradhan respond to the above comments and attempt to clarify the differences between their yield analysis and that of Singh 相似文献
49.
T. V. Narasaiah R. N. P. Choudhary A. K. Pradhan 《Journal of Materials Science》1987,22(10):3571-3575
The Raman and infrared spectra of polycrystalline samples TlH2AsO4, TlD2AsO4, TlH2PO4 and TlD2PO4 have been investigated at 300 K in the frequency ranges 0 to 4000 and 200 to 4000cm–1 respectively. The assignment of lattice, internal, and OH group vibrations has been approximated in terms of symmetry species. Although all the vibrations follow more or less the space group symmetry, the internal vibrations do not completely fulfill the requirements of the symmetry rule. The isotope effect was observed prominently on both compounds in Raman and infrared spectra. An attempt has been made to assign and explain the results. 相似文献
50.
This study examined the effects of procedural justice on state-dependent self-esteem using the group-value model and attribution theory to present competing theoretical perspectives. The group-value model predicts a positive relationship between self-esteem and fair procedures. In contrast, attribution theory suggests procedural fairness interacts with outcome favorability to influence self-esteem. Thus, fair procedures will result in higher self-esteem ratings than unfair procedures when the outcome is positive but will result in lower self-esteem ratings than unfair procedures when the outcome is negative. The results of a laboratory and field study provide converging evidence to support the attribution theory predictions. The results of a 2nd laboratory study suggest that self-esteem is influenced by outcome expectancies, not actual outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献