全文获取类型
收费全文 | 1021篇 |
免费 | 28篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 38篇 |
综合类 | 2篇 |
化学工业 | 237篇 |
金属工艺 | 21篇 |
机械仪表 | 24篇 |
建筑科学 | 8篇 |
能源动力 | 28篇 |
轻工业 | 62篇 |
水利工程 | 1篇 |
无线电 | 67篇 |
一般工业技术 | 180篇 |
冶金工业 | 298篇 |
原子能技术 | 18篇 |
自动化技术 | 66篇 |
出版年
2023年 | 6篇 |
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 9篇 |
2018年 | 24篇 |
2017年 | 14篇 |
2016年 | 19篇 |
2015年 | 8篇 |
2014年 | 17篇 |
2013年 | 27篇 |
2012年 | 29篇 |
2011年 | 39篇 |
2010年 | 28篇 |
2009年 | 20篇 |
2008年 | 34篇 |
2007年 | 48篇 |
2006年 | 32篇 |
2005年 | 35篇 |
2004年 | 20篇 |
2003年 | 20篇 |
2002年 | 23篇 |
2001年 | 18篇 |
2000年 | 21篇 |
1999年 | 33篇 |
1998年 | 122篇 |
1997年 | 74篇 |
1996年 | 50篇 |
1995年 | 33篇 |
1994年 | 20篇 |
1993年 | 30篇 |
1992年 | 17篇 |
1991年 | 23篇 |
1990年 | 9篇 |
1989年 | 14篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1980年 | 4篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1974年 | 2篇 |
1972年 | 4篇 |
排序方式: 共有1050条查询结果,搜索用时 46 毫秒
71.
72.
73.
A Matsumura O Yanase T Motomiya Y Tokuyasu H Sakurada S Nomura T Teshima Y Hiyoshi M Sugiura 《Canadian Metallurgical Quarterly》1995,18(4):234-235
Sarcoidosis is a multisystem granulomatous disorder of unknown etiology which mainly affects the lungs, skin, the lymphoreticular system, and the heart. We report a case of cardiac sarcoidosis in which a remarkably thin ventricular septum was demonstrated on two-dimensional echocardiography. 相似文献
74.
H Tsushima S Kawata S Tamura N Ito Y Shirai S Kiso Y Imai H Shimomukai Y Nomura Y Matsuda Y Matsuzawa 《Canadian Metallurgical Quarterly》1996,110(2):375-382
BACKGROUND & AIMS: Contribution of transforming growth factor beta 1 (TGF-beta 1) to tumor progression has been suggested. However, little is known about the role of TGF-beta 1 in colorectal cancer. Plasma TGF-beta 1 levels and its expression were analyzed in patients with colorectal cancer. METHODS: Plasma TGF-beta 1 levels were measured in 22 patients with colorectal cancer using a TGF-beta 1 enzyme-linked immunosorbent assay. Expression of TGF-beta 1 messenger RNA and immunohistochemical distribution of the protein in colorectal cancer tissues were examined. RESULTS: Plasma TGF-beta 1 levels in patients with colorectal cancer (14.8 +/- 8.4 ng/mL) were significantly higher than in normal controls (1.9 +/- 1.4; n = 22) (P < 0.001). After curative surgical resection, plasma TGF-beta 1 levels decreased in examined patients from 11.9 +/- 6.7 to 3.8 +/- 1.2 ng/mL (P < 0.01). TGF-beta 1 messenger RNA was about 2 1/2 times more abundant in colorectal cancer tissues than in control (P < 0.01). TGF-beta 1 was detected in the cytoplasm of colorectal cancer cells immunohistochemically. Both TGF-beta 1 messenger RNA expression in colorectal adenocarcinoma tissues and its plasma levels were associated with tumor stage of Dukes' classification (P < 0.05). CONCLUSIONS: These results suggest that plasma TGF-beta 1 levels may reflect overexpression of the gene in colon cancer tissues and are associated with disease progression. 相似文献
75.
Distribution and biliary and fecal excretion of bile acids were examined in Wistar strain male rats of about 300 g body weight.
The pool size of the rats on ordinary diet was 40 mg/rat, biliary secretion was 14 mg/hr, and fecal excretion was 10 mg/day.
Bile acids were mainly located in the small and large intestinal contents, 87% and 10%, respectively; but a portion was found
in the intestinal wall and the liver. Rats fed 2% cholesterol-supplemented diet for a week showed similar values for pool
size and biliary secretion with the rats on ordinary diet, but higher values for fecal excretion and distribution ratio in
the large intestinal contents. Cholic acid was a major component in the bile, small intestinal wall, small intestinal content
and liver, while the bile acid composition ratios were roughly similar to each other, although a relatively large amount of
α-muricholic acid was found in the intentinal wall and liver. Both the wall and content compositions of the large intestine
were similar to that of the feces, in which lithocholic, deoxycholic, α- and β-muricholic acids were the main components,
although the ratios of α- and β-muricholic acids in the large intestinal wall were larger than those in the intestinal contents
or feces. The high concentrations of these bile acids may indicate a difference of transport velocity across the cell membrane,
but the mechanism is not known. 相似文献
76.
77.
We report an experimental result that shows the excitation of surface plasmon polaritons by use of a zeroth-order Bessel beam. From the viewpoint of energy efficiency, the zeroth order Bessel beam is ideal for the local excitation of surface plasmon polaritons on a metal film. We introduce an optical setup using an axicon element in order to carry out the excitation. 相似文献
78.
S. Kimura F. Ogasawara Y. Suzuki R. Nomura Y. Okuda 《Journal of Low Temperature Physics》2004,134(1-2):157-162
When acoustic waves were applied to the solid-liquid interface of 4He perpendicularly, from the solid side, the solid was megted at high temperatures and grown at low temperatures. This means that the direction of the force on the interface was inverted at an inversion temperature, T i. We attributed this effect to the acoustic radiation pressure, which induced crystallization and megting [Phys. Rev. Lett. 90, 075301, (2003)]. Temperature dependence of the interface motion by acoustic waves was investigated in several surface orientations. Anisotropy of T i was found and T i was lower on a vicinal surface than on a rough surface. 相似文献
79.
In emulsion polymerization, the Smith and Ewart theory gives about two or three times the number of polymer particles obtained by experiment. In this paper, a reaction model is proposed which, from the standpoint of reactor design, can give an adequate explanation of the whole course of an emulsion polymerization of monomer highly insoluble in water. Among other things, the generating process of polymer particles is examined in detail. It is demonstrated experimentally that a new parameter proposed here, which represents the degree of difficulty of monomer initiation in micelles, is indispensable in explaining that process. Also confirmed is that monomer initiation takes place more easily in polymer particles than in micelles. According to the new model, the progress of polymerization, i.e., monomer conversion, the number of the polymer particles, and properties of polymer thus produced can be estimated with satisfactory accuracy. Furthermore, approximate equations are derived for easier estimation. 相似文献
80.
A secure optical storage based on a configuration of a joint transform correlator by use of a photorefractive material is presented. A key code designed through the use of an optimized algorithm so that its Fourier transform has a uniform amplitude distribution and a uniformly random phase distribution is introduced. Original two-dimensional data and the key code are placed side-by-side at the input plane. Both of them are stored in a photorefractive material as a joint power spectrum. The retrieval of the original data can be achieved with the same key code. We can record multiple two-dimensional data in the same crystal by angular multiplexing and/or key code multiplexing. 相似文献