全文获取类型
收费全文 | 1525篇 |
免费 | 36篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 86篇 |
综合类 | 4篇 |
化学工业 | 379篇 |
金属工艺 | 30篇 |
机械仪表 | 41篇 |
建筑科学 | 17篇 |
能源动力 | 42篇 |
轻工业 | 107篇 |
水利工程 | 3篇 |
无线电 | 95篇 |
一般工业技术 | 275篇 |
冶金工业 | 314篇 |
原子能技术 | 32篇 |
自动化技术 | 140篇 |
出版年
2023年 | 7篇 |
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 13篇 |
2019年 | 13篇 |
2018年 | 32篇 |
2017年 | 18篇 |
2016年 | 27篇 |
2015年 | 10篇 |
2014年 | 22篇 |
2013年 | 55篇 |
2012年 | 55篇 |
2011年 | 71篇 |
2010年 | 48篇 |
2009年 | 44篇 |
2008年 | 55篇 |
2007年 | 75篇 |
2006年 | 50篇 |
2005年 | 64篇 |
2004年 | 39篇 |
2003年 | 43篇 |
2002年 | 39篇 |
2001年 | 28篇 |
2000年 | 33篇 |
1999年 | 42篇 |
1998年 | 131篇 |
1997年 | 81篇 |
1996年 | 56篇 |
1995年 | 38篇 |
1994年 | 28篇 |
1993年 | 40篇 |
1992年 | 23篇 |
1991年 | 33篇 |
1990年 | 11篇 |
1989年 | 23篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 14篇 |
1978年 | 7篇 |
1977年 | 13篇 |
1976年 | 12篇 |
1972年 | 6篇 |
1971年 | 4篇 |
排序方式: 共有1565条查询结果,搜索用时 15 毫秒
91.
Techniques for measuring aberrations in lenses used in photolithography with printed patterns 总被引:3,自引:0,他引:3
In optical lithography, it is a serious problem that aberrations in projection lenses reduce the imaging quality. Therefore techniques to measure the aberrations are required that will predict the adverse effects of aberrations on lithographic imagery and reduce them. We present a measurement method that uses a fine grating and its imaging condition to quantify coma, astigmatism, and spherical aberration. With this method, these aberrations can be described with simple expressions from the measured results. Application of this method revealed the coma of Zernike polynomials for our krypton fluoride (KrF) excimer-laser scanner. 相似文献
92.
We report a 68-year-old man who had immediate-type heat urticaria with systemic symptoms. Immersing his hand in water at 42 degrees C (heat challenge test) produced an urticarial response, with an increase in the plasma histamine level from 0.26 to 7.64 ng/mL. Administration of oral antihistamines alone did not suppress either the urticarial response or the increase in plasma histamine. However, a combination of antihistamines and desensitization improved the skin lesions and reduced the plasma histamine level. The heat challenge test subsequently provoked a negative response and there was no increase in plasma histamine level 3 months after starting the combination therapy. These results indicate that the histamine level reflected the result of the heat challenge test and the amelioration of the skin eruption. 相似文献
93.
94.
95.
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
96.
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
97.
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
98.
99.
100.
The method has been developed to improve the bitumen product which incorporates an evaporator concentrate from a BWR, with respect to the swelling and leaching. The leachability of the product has been measured by the method recommended by the IAEA. The swelling of the product is successfully prevented by the addition of calcium chloride. The specimen containing the waste up to Wa/B (Weight ratio of Na2SO4 + CaCl2 and bitumen) = 60:40 shows no pronounced swelling, when it is immersed in water. The cumulative fractions of 137Cs and 60Co leached from a specimen which does not contain CaCl2 are 0.65 and 0.2 at the leaching time of 30 days. On the hand, the corresponding value at 100 days for the specimen with calcium chloride addition is 5 × 10?4 for 137Cs and 1 × 10?4 for 60Co. The coating of the specimen surface with a fresh bitumen (5 mm thickness) reduces the leachability further. These results indicate that this method is effective to improve the bitumen product incorporating BWR's evaporator concentrate. 相似文献