全文获取类型
收费全文 | 1569篇 |
免费 | 22篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 104篇 |
综合类 | 1篇 |
化学工业 | 287篇 |
金属工艺 | 45篇 |
机械仪表 | 24篇 |
建筑科学 | 42篇 |
能源动力 | 47篇 |
轻工业 | 117篇 |
水利工程 | 1篇 |
石油天然气 | 5篇 |
无线电 | 174篇 |
一般工业技术 | 200篇 |
冶金工业 | 398篇 |
原子能技术 | 31篇 |
自动化技术 | 117篇 |
出版年
2022年 | 16篇 |
2021年 | 15篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 23篇 |
2016年 | 19篇 |
2015年 | 14篇 |
2014年 | 26篇 |
2013年 | 56篇 |
2012年 | 47篇 |
2011年 | 62篇 |
2010年 | 52篇 |
2009年 | 48篇 |
2008年 | 55篇 |
2007年 | 61篇 |
2006年 | 49篇 |
2005年 | 38篇 |
2004年 | 34篇 |
2003年 | 45篇 |
2002年 | 31篇 |
2001年 | 26篇 |
2000年 | 22篇 |
1999年 | 37篇 |
1998年 | 149篇 |
1997年 | 98篇 |
1996年 | 63篇 |
1995年 | 45篇 |
1994年 | 44篇 |
1993年 | 37篇 |
1992年 | 19篇 |
1991年 | 20篇 |
1990年 | 12篇 |
1989年 | 20篇 |
1988年 | 17篇 |
1986年 | 22篇 |
1985年 | 21篇 |
1984年 | 18篇 |
1983年 | 15篇 |
1982年 | 17篇 |
1981年 | 14篇 |
1980年 | 20篇 |
1979年 | 25篇 |
1978年 | 15篇 |
1977年 | 13篇 |
1976年 | 22篇 |
1975年 | 11篇 |
1974年 | 13篇 |
1973年 | 12篇 |
1972年 | 10篇 |
排序方式: 共有1593条查询结果,搜索用时 0 毫秒
61.
A hierarchical command structure and separate drafting and display files allow ease of use and quick response in this 2-D drawing system. 相似文献
62.
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
63.
Stubenrauch C.F. Newell A.C. Repjar A.G. MacReynolds K. Tamura D.T. Larsen F.H. Lemanczyk J. Behe R. Portier G. Zehren J.C. Hollmann H. Hunter J.D. Gentle D.G. de Vreede J.P.M. 《Antennas and Propagation, IEEE Transactions on》1996,44(10):1367-1374
An international intercomparison of horn gain and polarization measurements at X-band has previously been completed. There were seven participating laboratories with the National Institute of Standards and Technology serving as the pilot laboratory. Two X-band pyramidal standard gain horns with a nominal gain of 22 dB served as the traveling standards. Quantities measured included on-axis fixed frequency gain at 8, 10, and 12 GHz, swept frequency gain between 8-12 GHz and polarization characteristics at the three fixed frequencies. All laboratories performed the fixed frequency-gain measurements. The swept-frequency and polarization measurements were optional, with four laboratories performing swept-frequency measurements and three laboratories measuring polarization. The results of the gain measurements generally agreed within the reported uncertainties which were of the order of 0.1 dB or less 相似文献
64.
65.
Shinichi Tamura 《Pattern recognition》1982,15(6):477-483
This paper deals with a separation of strongly touching clusters using a concept of n-connectedness between pattern pairs, i.e., the number of paths between patterns. This new concept is similar to the concept of n-connectedness of graphs. Classification algorithms based on the number of independent paths and edge-disjoint paths are presented. It is shown that the latter has a transitivity. Finally, a simpler algorithm, i.e., a classification method based on the total number of paths, is presented. The proposed algorithm may be seen as an intermediate one between the ordinary connectedness algorithm and the maximal complete subgraph (MCS) algorithm. 相似文献
66.
Nobuhiko Onda Kunio Furusawa Noriko Yamaguchi Masatoshi Tokiwa Yasumasa Hirai 《应用聚合物科学杂志》1980,25(10):2363-2372
In a study of polyacrylamide in solutions we have required the rapid characterization on chromatographies. The application to the aqueous solution of the GPC using controlled-porosity glass has been examined from both the viewpoint of the effect of salt addition and the GPC mechanism. An adequate addition to neutral salt, 0.005M KCI to the eluent, gave rise to the elution behaviors being in accord with the hydrodynamic volume concept of the GPC separation. 相似文献
67.
For designing a fibre structure, the influence of structural parameters on optical loss is investigated experimentally for a graded-index fibre. The fibre with large cladding/outer-layer index difference and small cladding thickness is found to have large excess loss near excitation points, such as a launching point and a splicing point. 相似文献
68.
69.
The electrolytic reduction of ferricyanide and the electrolytic oxidation of ferrocyanide have been carried out with exposing the magnetic field of 1000 or 1800 gauss. The current clearly increased after the magnetic exposure. The maximum current was obtained when the magnetic flux directed in parallel with the surface of electrode. These are speculated in terms of magnetohydrodynamic mechanism. The current decrease caused by relaxation process was observed after the removal of magnetic flux. The relaxation time obtained was temperature-dependent. Therefore the values of apparent transition energy, Etrans, were determined from the Arrhenius' plots of relaxation time against temperature. The magnitude of Etrans was dependent on the concentration of ferricyanide or ferrocyanide, and the viscosity and the conductivity of electrolyte solution. The activation energy of viscosity of electrolyte solution was compared with Etrans. As a conclusion, it was suggested that Etrans may be influenced by the velocity of magnetohydrodynamic flow, which was controlled by the diffusion current in electrolysis and the viscosity of electrolyte solution. 相似文献
70.