全文获取类型
收费全文 | 644篇 |
免费 | 13篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 132篇 |
金属工艺 | 11篇 |
机械仪表 | 16篇 |
建筑科学 | 20篇 |
矿业工程 | 7篇 |
能源动力 | 8篇 |
轻工业 | 43篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
无线电 | 26篇 |
一般工业技术 | 88篇 |
冶金工业 | 236篇 |
原子能技术 | 6篇 |
自动化技术 | 53篇 |
出版年
2021年 | 4篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 7篇 |
2014年 | 22篇 |
2013年 | 14篇 |
2012年 | 16篇 |
2011年 | 19篇 |
2010年 | 12篇 |
2009年 | 21篇 |
2008年 | 19篇 |
2007年 | 13篇 |
2006年 | 15篇 |
2005年 | 24篇 |
2004年 | 11篇 |
2003年 | 6篇 |
2002年 | 13篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 16篇 |
1998年 | 84篇 |
1997年 | 41篇 |
1996年 | 35篇 |
1995年 | 18篇 |
1994年 | 13篇 |
1993年 | 17篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1986年 | 11篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 4篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 17篇 |
1975年 | 6篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1971年 | 6篇 |
1970年 | 4篇 |
1969年 | 4篇 |
1968年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有657条查询结果,搜索用时 265 毫秒
1.
OL Lopez RP Brenner JT Becker RF Ulrich F Boller ST DeKosky 《Canadian Metallurgical Quarterly》1997,48(6):1521-1525
We examined whether either psychotic features (e.g., delusions and hallucinations) or EEG abnormalities are associated with more rapid progression of Alzheimer's disease (AD). AD patients with psychosis have exhibited more EEG abnormalities than those without psychosis, and both abnormal EEG and psychosis have been noted to be predictors of functional and cognitive decline in AD. Ninety-five probable AD patients participating in a longitudinal study of dementia had an EEG and a semistructured psychiatric interview at baseline. Using EEG spectral analysis, we classified records as normal/abnormal based on the parasagittal mean frequency. Patients with abnormal EEGs were more functionally (e.g., Blessed Rating Scale for activities of daily living) and cognitively (e.g., Mini-Mental State) impaired than patients with normal EEG. AD patients with psychosis were only more functionally impaired than patients without psychosis. A two-factor analysis showed no interaction between abnormal EEG and psychosis. In addition, using a Cox proportional hazard model adjusted for age and education, the presence of an abnormal EEG or psychotic symptom at study entry was associated with higher risk of reaching severe cognitive and functional impairment during follow-up. Neither abnormal EEG nor the presence of psychosis predicted death. These results indicate that both abnormal EEG and psychosis are independent predictors of disease progression but not of physical survival. 相似文献
2.
BACKGROUND: Since its foundation in 1960, the International Society of Nephrology (ISN) has pursued the worldwide advancement of education, science and patient care in nephrology. This goal was achieved by means of the Society's journal and the organization of international congresses and symposia. In order to better reach its colleagues and patients in economically less developed countries, the ISN expanded its activities as of 1980 by a large number of specific programs aimed at these regions. METHODS: The first phase of activities included teaching programs, fellowship and visiting scholar programs, and the provision of travel grants to enhance accessibility to the ISN congresses. A second phase consisted of the creation of a library enhancement program, a commission on acute renal failure and--to improve the organization and efficiency--a central commission on global advancement of nephrology (COMGAN). Currently, a third phase has been entered in which all activities have been intensified: (1) under the guidance of COMGAN, supported by a large number of teaching programs and fact finding missions; (2) by establishing a renal sister program; and (3) by initiating commissions on informatics and on clinical trials. RESULTS: As a result, the ISN has reached most parts of the world, previously deprived of contact with renal science and renal patient care. The fellowship program now counts 160 fellows, who spend one or two years in training. The library enhancement program reaches 218 institutions worldwide. ISN membership has soared over the past two years with over 2,500 new members, mostly in the developing countries. They receive Kidney International and other relevant forms of information. Thus far, 135 pairs of renal units in developing and developed countries have been linked for support on a more continuous basis. ISN-sponsored congresses, symposia, and courses are being held in increasing numbers in the developing world. In many of its activities, the ISN closely collaborates with sister organizations, which also contribute financially. In total, the ISN spends annually over $1 million US from its own budget on the programs described above. CONCLUSION: The various programs and initiatives are proving helpful in advancing renal medicine in areas in need. Expansion into supporting similar programs within other medical subspecialties is being explored. 相似文献
3.
4.
5.
Dr. Jana Buchwalter Prof. Dr. Walter Brenner Dr. Rüdiger Zarnekow 《WIRTSCHAFTSINFORMATIK》2002,44(4):345-353
Many companies and purchasing departments only possess a limited knowledge about the modelling of inter-company business processes for electronic procurement. In the past the discussion about electronic procurement was mostly focused on technical aspects. This article introduces a reference process model for procurement auctions. The process model is made up of a basic process, which describes a minimal process for procurement auctions, and a number of process alternatives, which allow for the adoption of the basic process to changing parameters and individual company requirements. 相似文献
6.
A novel generic design for waveguide grating routers is demonstrated in the InP-InGaAsP material system that reduces the chip size by 50%, while still maintaining relaxed processing tolerances. Experimental results confirm no degradation in device performance for the compact design when compared to conventional devices 相似文献
7.
Polarisation insensitive semiconductor optical amplifier withintegrated electroabsorption modulators
Koren U. Miller B.I. Young M.G. Chien M. Raybon G. Brenner T. Ben-Michael R. Dreyer K. Capik R.J. 《Electronics letters》1996,32(2):111-112
The authors demonstrate a 1.55 μm wavelength multiquantum well semiconductor optical amplifier, integrated with bulk layer electroabsorption modulators and passive waveguide beam expanders at the input and output ports. The device has a fibre to fibre gain of 9 dB, an extinction ratio of 15 dB per modulator, a spectral range >35 nm, and polarisation sensitivity <1 dB 相似文献
8.
M. K. Miller S. S. Brenner M. G. Burke 《Metallurgical and Materials Transactions A》1987,18(5):519-523
The addition of palladium to a 4130 steel reduces its sensitivity to stress corrosion cracking and to hydrogen-induced cracking.
The atom probe field-ion microscope has been used to study the microstructure and microchemistry of these palladium-modified
4130 steels with particular emphasis on the distribution of palladium between the various phases and internal interfaces.
The palladium was found to segregate to the ferrite-ferrite lath boundaries to form a mono-atomically thick adsorbate layer.
Palladium-manganese precipitates both at the lath boundaries and in the ferrite matrix were also detected. Most of the palladium
was found to remain in solution in the ferrite. 相似文献
9.
10.
Perception and action are based on the same visual information: distinction between position and velocity. 总被引:2,自引:0,他引:2
Ss were presented with spiders running from left to right at various velocities over a structured background. Motion of the background influenced the perceived velocity of the spider: Motion of the background in the opposite direction than the spider increased the perceived velocity. The perceived position of the spider was not influenced by background motion. Ss were asked to hit the spiders as quickly as possible. Fast spiders were hit with a higher velocity than slow spiders. The same effect was found if the spiders only differed in apparent velocity, induced by motion of the background. The trajectory of the hit was not influenced by motion of the background. The authors concluded that although velocity is nothing but the change of position in time, velocity and position are processed independently. Furthermore, these two separately processed sources of information are used in both perception and action. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献