全文获取类型
收费全文 | 1694篇 |
免费 | 45篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 70篇 |
综合类 | 3篇 |
化学工业 | 311篇 |
金属工艺 | 44篇 |
机械仪表 | 42篇 |
建筑科学 | 41篇 |
能源动力 | 60篇 |
轻工业 | 133篇 |
水利工程 | 5篇 |
石油天然气 | 9篇 |
无线电 | 238篇 |
一般工业技术 | 218篇 |
冶金工业 | 413篇 |
原子能技术 | 32篇 |
自动化技术 | 126篇 |
出版年
2023年 | 10篇 |
2022年 | 16篇 |
2021年 | 28篇 |
2020年 | 11篇 |
2019年 | 5篇 |
2018年 | 24篇 |
2017年 | 26篇 |
2016年 | 27篇 |
2015年 | 22篇 |
2014年 | 33篇 |
2013年 | 66篇 |
2012年 | 49篇 |
2011年 | 72篇 |
2010年 | 62篇 |
2009年 | 69篇 |
2008年 | 57篇 |
2007年 | 65篇 |
2006年 | 49篇 |
2005年 | 48篇 |
2004年 | 36篇 |
2003年 | 49篇 |
2002年 | 52篇 |
2001年 | 41篇 |
2000年 | 41篇 |
1999年 | 44篇 |
1998年 | 151篇 |
1997年 | 97篇 |
1996年 | 87篇 |
1995年 | 54篇 |
1994年 | 43篇 |
1993年 | 46篇 |
1992年 | 20篇 |
1991年 | 33篇 |
1990年 | 11篇 |
1989年 | 17篇 |
1988年 | 18篇 |
1987年 | 20篇 |
1986年 | 16篇 |
1985年 | 27篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1977年 | 7篇 |
1976年 | 13篇 |
1975年 | 5篇 |
1972年 | 5篇 |
1971年 | 2篇 |
排序方式: 共有1745条查询结果,搜索用时 2 毫秒
11.
Poly(L-ornithine)s having various azo-contents in the side chains were synthesized by the water-soluble carbodiimide procedure. The photochemical properties of the polypeptides poly[Nδ-p-(phenylazo)benzoyl-L-ornithine] (PPABLO) containing 3–77 mol% azobenzene were investigated by absorption and circular dichroism spectroscopy in hexafluoro-2-propanol (HFIP) or water, and in HFIP-water or methanol-water solvent mixtures. The photochromism of the dichroic bands of the PPABLOs containing 20–77 mol% azobenzene in the visible and ultraviolet wavelength regions was found to be mostly reversible as a function of irradiation time at different wavelengths due to the photostationary state (above 80% trans-cis photoisomerization) of the azo aromatic moieties. The PPABLO containing 3.2 mol% azobenzene in water exhibited conformational changes from random coil to helix by the addition of methanol or sodium dodecyl sulphate (SDS). The photo-induced conformational change was observed in HFIP-water-SDS solvent mixtures, while no conformational change was seen in water and HFIP-water solvent mixtures. 相似文献
12.
13.
Y Nakajima O Mikami M Yoshioka Y Motoi T Ito Y Ishikawa M Fuse K Nakano K Yasukawa 《Canadian Metallurgical Quarterly》1997,62(3):297-298
The presence of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) activities was determined in milk and serum of cows with naturally occurring coliform mastitis (CFM). TNF-alpha was detected in the sera from 26 of 32 cows with CFM. TNF-alpha levels were higher in the sera than in the milk. IL-6 was high in the sera of surviving CFM animals, but was low in animals that died and in healthy controls. Furthermore, the mean level of IL-6 was 20-fold higher in the milk than in the sera of mastitic cows. The level of IL-6 in the serum was correlated to that in the milk in individual animals. The presence of IL-6 and TNF-alpha in the sera appears to relate to severe clinical condition of CFM, in the milk whereas they may play a role in generating inflammation of the mammary gland. 相似文献
14.
K Nakano S Ohta K Nishimaki T Miki S Matuda 《Canadian Metallurgical Quarterly》1997,350(9088):1367-1368
15.
16.
Y Ota Y Nakano H Yamaguchi K Yoshida T Shirafuji A Adachi 《Canadian Metallurgical Quarterly》1993,20(8):1055-1057
In a 63-year-old male patient with gastric cancer having multiple liver metastases, the metastatic lesions responded well to postoperative staggered intraarterial infusion therapy with MTX and 5-FU. The intraarterial infusion therapy was administered once a week. A total of 5 courses of this therapy produced marked regression of liver metastases and remarkable necrosis. The effect was thus rated as PR. The patient is healthy and has been successfully rehabilitated. His dose is oral 5-FU (200 mg x 2). 相似文献
17.
18.
Matsugi J. Mizoh Y. Nakano T. Nakamura K. Sakakima H. 《Electronics Packaging Manufacturing, IEEE Transactions on》2005,28(3):206-212
It is well known that giant magnetoresistive (GMR) heads used for hard disk drives (HDD) are very sensitive to electrostatic discharge (ESD). In this paper, we describe a method of categorizing ESD damage modes from a standpoint of magnetic influences on the heads as observed by quasi-static test (QST) characteristics as well as electromagnetic characteristics like off-track profiles. In addition, we report an example of GMR stack interlayer diffusion which is one type of hard ESD damage. We also present an example of ESD damage that happened in an actual production process and its preventive measures as guidelines. 相似文献
19.
Double-band operation (85 and 900 MHz) of a collinear monopole antenna is numerically demonstrated. The antenna consists of three linear wires connected with two coils, and has a height of 67 cm. One coil acts as a phase compensation element to increase the gain and the other as a decoupling element for use in the mobile telephone band.<> 相似文献
20.
An analytical expression for conjugate signals is developed for a case where three rectangular pulses with the same center frequency are injected into a two-level system. The Maxwell's equation is solved with the slowly varying envelope approximation and with the perturbative third-order nonlinear polarization expression of a two-level system. Numerical examples are discussed in such a way that the input pulsewidth is changed relative to the energy relaxation and dephasing times. As the optical pulsewidth becomes short, ripples appear in the signal pulse due to the beat between the optical field and the resonant oscillation of the atomic system 相似文献