全文获取类型
收费全文 | 230953篇 |
免费 | 31820篇 |
国内免费 | 12021篇 |
专业分类
电工技术 | 16553篇 |
技术理论 | 6篇 |
综合类 | 16142篇 |
化学工业 | 43402篇 |
金属工艺 | 12224篇 |
机械仪表 | 13784篇 |
建筑科学 | 17778篇 |
矿业工程 | 6301篇 |
能源动力 | 6703篇 |
轻工业 | 21847篇 |
水利工程 | 5087篇 |
石油天然气 | 9705篇 |
武器工业 | 2187篇 |
无线电 | 29712篇 |
一般工业技术 | 30162篇 |
冶金工业 | 8304篇 |
原子能技术 | 2254篇 |
自动化技术 | 32643篇 |
出版年
2024年 | 1003篇 |
2023年 | 3265篇 |
2022年 | 6412篇 |
2021年 | 8921篇 |
2020年 | 7812篇 |
2019年 | 7991篇 |
2018年 | 8543篇 |
2017年 | 9800篇 |
2016年 | 9473篇 |
2015年 | 12301篇 |
2014年 | 14465篇 |
2013年 | 17395篇 |
2012年 | 17292篇 |
2011年 | 17682篇 |
2010年 | 16764篇 |
2009年 | 15825篇 |
2008年 | 15184篇 |
2007年 | 14414篇 |
2006年 | 13072篇 |
2005年 | 10423篇 |
2004年 | 7677篇 |
2003年 | 6869篇 |
2002年 | 6791篇 |
2001年 | 6009篇 |
2000年 | 4869篇 |
1999年 | 3546篇 |
1998年 | 2038篇 |
1997年 | 1718篇 |
1996年 | 1587篇 |
1995年 | 1349篇 |
1994年 | 1063篇 |
1993年 | 693篇 |
1992年 | 573篇 |
1991年 | 418篇 |
1990年 | 325篇 |
1989年 | 268篇 |
1988年 | 201篇 |
1987年 | 143篇 |
1986年 | 129篇 |
1985年 | 57篇 |
1984年 | 51篇 |
1983年 | 35篇 |
1982年 | 44篇 |
1981年 | 52篇 |
1980年 | 53篇 |
1979年 | 34篇 |
1976年 | 13篇 |
1974年 | 13篇 |
1959年 | 12篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
S. K. Chen A. Serquis G. Serrano K. A. Yates M. G. Blamire D. Guthrie J. Cooper H. Wang S. Margadonna J. L. MacManus‐Driscoll 《Advanced functional materials》2008,18(1):113-120
By applying a combination of characterisation tools, changes in structural and superconducting properties with nominal Mg non‐stoichiometry in MgxB2 are found. The non‐stoichiometry produces enhanced in‐field critical current densities (Jc's) and upper critical field / irreversibility field (Hc2/Hirr(T)) values. Upper critical fields of ~ 21 T (4.2 K) were obtained in nominal Mg‐deficient samples compared to ~ 17 T (4.2 K) for near‐stoichiometric samples. 相似文献
32.
This paper presents an investigation on a single-mode-multimode-single-mode fiber structure. A one-way guided-mode propagation analysis for the circular symmetry waveguide is employed to model the light propagation and the approximated formulations are derived and evaluated concerning the accuracy. Phase conjunction of the multimode interference within the fiber structure is revealed. A simple way to predict and analyze the spectral response of the structure is presented through the space to wavelength mapping with the derived approximated formulations. The prediction of spectral response is verified numerically and experimentally. 相似文献
33.
The ennoblement of corrosion potential (Ecorr) of passive metal immersed in seawater was investigated with electrochemical technology and epifluorescence microscopy. The in situ observation showed that the bacteria number increased on the metal surface according to an exponential law which was in the same way with the ennoblement of Ecorr. At the same time, the anodic polarization current of high‐Mo stainless steel decreased in the initial days. According to the mix‐potential theory and the characteristics of polarization curves of high‐Mo steel in natural seawater, the ennoblement of corrosion potential may be induced by the decrease of the passive current density. 相似文献
34.
H.J. Bolink E. Coronado D. Repetto M. Sessolo E.M. Barea J. Bisquert G. Garcia‐Belmonte J. Prochazka L. Kavan 《Advanced functional materials》2008,18(1):145-150
A new type of bottom‐emission electroluminescent device is described in which a metal oxide is used as the electron‐injecting contact. The preparation of such a device is simple. It consists of the deposition of a thin layer of a metal oxide on top of an indium tin oxide covered glass substrate, followed by the solution processing of the light‐emitting layer and subsequently the deposition of a high‐workfunction (air‐stable) metal anode. This architecture allows for a low‐cost electroluminescent device because no rigorous encapsulation is required. Electroluminescence with a high brightness reaching 5700 cd m–2 is observed at voltages as low as 8 V, demonstrating the potential of this new approach to organic light‐emitting diode (OLED) devices. Unfortunately the device efficiency is rather low because of the high current density flowing through the device. We show that the device only operates after the insertion of an additional hole‐injection layer in between the light‐emitting polymer (LEP) and the metal anode. A simple model that explains the experimental results and provides avenues for further optimization of these devices is described. It is based on the idea that the barrier for electron injection is lowered by the formation of a space–charge field over the metal‐oxide–LEP interface due to the build up of holes in the LEP layer close to this interface. 相似文献
35.
Wei Li Zhang Wei Pan Bin Luo Xi Hua Zou Meng Yao Wang 《Photonics Technology Letters, IEEE》2008,20(9):712-714
A theoretical construction of one-to-many (OTM) and many-to-one (MTO) chaos synchronization communications using semiconductor lasers is presented. One center laser provides strong injections (strong link) to other side lasers, and the side lasers also provide weak injections (weak link) to the center one. Simulation results show that the side lasers synchronize with the center laser through injection-locking. In addition, messages transmitted via the strong links or the weak links experience strong chaos pass filtering, enabling us to realize OTM and MTO communications. 相似文献
36.
37.
38.
Lie‐Fern Hsu 《Quality and Reliability Engineering International》2007,23(2):269-272
He and Grigoryan (Quality and Reliability Engineering International 2002; 18 :343–355) formulated the design of a double‐sampling (DS) s control chart as an optimization problem and solved it with a genetic algorithm. They concluded that the DS s control charts can be a more economically preferable alternative in detecting small shifts than traditional s control charts. We explain that, since they only considered the average sample size when the process is in control, their conclusion is questionable. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
39.
LaNiO3 was synthesized by sol-gel method in which lanthanum nitrate and nickel nitrate were used as start materials and citric acid was used as complex for gel formation.The precursor was dried and subsequently heated at elevated temperature to form the desired product.XRD analysis shows that pure LaNiO3 was synthesized.Electrical conductivity and electrochemical performance of the material were tested.The electrical conductivity decreases from 34.5that there are current peaks in the curve, which is the evidence of the electrochemical activity of LaNiO3. 相似文献
40.
Yanqing Ji Hao Ying John Yen Shizhuo Zhu Daniel C. Barth‐Jones Richard E. Miller R. Michael Massanari 《国际智能系统杂志》2007,22(8):827-845
Discovering unknown adverse drug reactions (ADRs) in postmarketing surveillance as early as possible is highly desirable. Nevertheless, current postmarketing surveillance methods largely rely on spontaneous reports that suffer from serious underreporting, latency, and inconsistent reporting. Thus these methods are not ideal for rapidly identifying rare ADRs. The multiagent systems paradigm is an emerging and effective approach to tackling distributed problems, especially when data sources and knowledge are geographically located in different places and coordination and collaboration are necessary for decision making. In this article, we propose an active, multiagent framework for early detection of ADRs by utilizing electronic patient data distributed across many different sources and locations. In this framework, intelligent agents assist a team of experts based on the well‐known human decision‐making model called Recognition‐Primed Decision (RPD). We generalize the RPD model to a fuzzy RPD model and utilize fuzzy logic technology to not only represent, interpret, and compute imprecise and subjective cues that are commonly encountered in the ADR problem but also to retrieve prior experiences by evaluating the extent of matching between the current situation and a past experience. We describe our preliminary multiagent system design and illustrate its potential benefits for assisting expert teams in early detection of previously unknown ADRs. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 827–845, 2007. 相似文献