全文获取类型
收费全文 | 1231篇 |
免费 | 31篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 71篇 |
综合类 | 3篇 |
化学工业 | 279篇 |
金属工艺 | 43篇 |
机械仪表 | 23篇 |
建筑科学 | 21篇 |
能源动力 | 38篇 |
轻工业 | 81篇 |
水利工程 | 2篇 |
无线电 | 94篇 |
一般工业技术 | 179篇 |
冶金工业 | 248篇 |
原子能技术 | 67篇 |
自动化技术 | 115篇 |
出版年
2022年 | 11篇 |
2021年 | 22篇 |
2020年 | 13篇 |
2019年 | 6篇 |
2018年 | 16篇 |
2017年 | 13篇 |
2016年 | 18篇 |
2015年 | 16篇 |
2014年 | 24篇 |
2013年 | 66篇 |
2012年 | 42篇 |
2011年 | 67篇 |
2010年 | 52篇 |
2009年 | 49篇 |
2008年 | 46篇 |
2007年 | 55篇 |
2006年 | 56篇 |
2005年 | 46篇 |
2004年 | 44篇 |
2003年 | 30篇 |
2002年 | 41篇 |
2001年 | 22篇 |
2000年 | 19篇 |
1999年 | 23篇 |
1998年 | 104篇 |
1997年 | 78篇 |
1996年 | 49篇 |
1995年 | 30篇 |
1994年 | 22篇 |
1993年 | 29篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 11篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1973年 | 6篇 |
1972年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有1264条查询结果,搜索用时 437 毫秒
1.
S Harino M Motokura N Nishikawa M Fukuda A Sasaoka JE Grunwald 《Canadian Metallurgical Quarterly》1994,117(3):302-307
We studied the ocular findings of two adult patients with the Eisenmenger's syndrome who had atrial septal defects that were diagnosed before the age of 10 years but not operated on and pulmonary hypertension. Both eyes of these patients showed microaneurysms, multiple small blot hemorrhages, or capillary dilation in the temporal peripheral fundus. Multiple microaneurysms and retinal collaterals were confirmed by fluorescein angiography. One of the patients developed bilateral rubeosis iridis with slow progression. These retinal lesions and the rubeosis iridis are probably related to chronic ocular ischemia caused by chronic systemic hypoxia. 相似文献
2.
We investigated liquid crystallization of liquid crystalline polyester BB-5 during isothermal annealing by digital high-fidelity microscope and light scattering. A liquid crystalline spherical domain having a radius of micrometers appeared by annealing at around 180 °C. The domain grew dendritically in all directions. Neighboring liquid crystalline regions coalesced and then interconnected. The interconnected structure changed to a co-continuous two-phase structure with increasing ordering of the liquid crystalline phase, and the interface between the liquid crystalline phase and the isotropic phase became smoother over time. Liquid crystallization stopped before volume filling the whole space, and the liquid crystalline phase and isotropic phase coexisted. The liquid crystalline region became narrower with an increase in the temperature of the liquid crystallization. Such structural development is different from the liquid-liquid phase separation via spinodal decomposition, and it may be attributed to the segregation of non-liquid crystallizable low molecular weight molecules from the growth front by fractionation of the molecular weight distribution during the liquid crystallization in terms of the instability of the diffusion-controlled interface. 相似文献
3.
K Jin-no M Tanimizu I Hyodo Y Nishikawa Y Hosokawa H Endo T Doi K Mandai H Ishitsuka 《Canadian Metallurgical Quarterly》1998,82(7):1260-1267
BACKGROUND: Platelet-derived endothelial cell growth factor (PD-ECGF) is an angiogenic factor that is expressed in various cancer tissues. Little is known regarding plasma PD-ECGF levels in patients with chronic liver disease such as chronic hepatitis (CH), cirrhosis, and hepatocellular carcinoma (HCC) with cirrhosis. The expression of PD-ECGF in HCC tissues also remains to be clarified. METHODS: Plasma PD-ECGF levels in patients with chronic liver disease were determined with an enzyme-linked immunoadsorbent assay system using the mouse monoclonal antibodies specific to PD-ECGF. These were cross-sectionally compared among groups of normal persons, CH, cirrhosis, and HCC patients. The HCC patients were classified into two groups based on TNM stage: early and advanced stage disease groups. PD-ECGF expressions in HCC tissues were immunohistologically examined. RESULTS: The plasma PD-ECGF levels from the normal individuals and those with CH, cirrhosis, and HCC specimens were 4.2+/-0.5, 4.3+/-0.6, 4.6+/-1.1, and 6.0 +/-2.5 U/mL, respectively. The plasma PD-ECGF concentration was highest in HCC (P < 0.05). No significant difference was found among the normal subjects, CH, and cirrhosis specimens. Plasma PD-ECGF concentrations were significantly higher in the advanced stage disease HCC group compared with the early stage disease group (6.75+/-2.62 U/mL vs. 4.19+/-0.34 U/mL) (P < 0.05). Immunohistochemical expression of PD-ECGF in HCC cells increased significantly compared with normal liver cells (P < 0.05). CONCLUSIONS: Circulating PD-ECGF plasma level might be a new tumor marker for progression in patients with HCC. Immunohistological findings correspond to elevation of the plasma PD-ECGF in HCC patients. It is possible that increased production of PD-ECGF in HCC cells causes abundant neovascularization. 相似文献
4.
S Ikezaki A Nishikawa F Furukawa T Imazawa M Mitsui T Enami M Takahashi 《Canadian Metallurgical Quarterly》1995,(113):44-50
A 13-week subchronic toxicity study of josamycin was performed in male and female F344 rats to determine the maximum tolerable dose (MTD) for subsequent investigation of the carcinogenicity. As animals refused to take diet containing 5.0% josamycin in our preliminary study, dose levels in the present study were determined as 0, 0.16, 0.32, 0.63, 125 and 2.5% in diet. Rats were randomly allocated to 6 groups, each consisting of 10 males and 10 females. No animal died during the administration period and no group showed significant changes in body weight gain. Definite toxicity of josamycin was not noted in hematological and serum biochemical examinations. Histopathological examinations revealed no particular findings related to josamycin administration except cecal enlargement in the 1.25 and 2.5% groups. based on the results of the present study, it was concluded that the MTD of josamycin in 2.5% in diet, because the dietary dose level of 2.5% proved to exert no significant toxicological signs. 相似文献
5.
6.
Nelly RahmanApriyanti Isanasari Ririn AnggraeniSuharto Honggokusumo Masatoshi Iguchi Toru MasukoKohji Tashiro 《Polymer》2003,44(1):283-288
To investigate the mechanism of high elongation of natural rubber attained by the ‘racking method’, a strip of smoked-sheet was elongated up to 150 times in length, by stretching rapidly at room temperature and forcing to shrink at 75-80 °C repeatedly. On X-ray diffraction, a typical fibre pattern with an amorphous ring appeared already at ×10 (stretch ratio=10). The degree of crystallinity increased to the level of 17-18% at ×20 and turned to decrease after ×60, but the degree of crystallite orientation reached at a high level already at ×10 and did not change significantly and the half-height width of reflection profiles stayed almost at a constant level, while the Young's modulus increased up to ca. 300 MPa at ×100 and then fell rather discontinuously. It was assumed that some fractions of chain segments between entanglements were gradually broken in each step of stretching operation, rather than disentangled and slipped. 相似文献
7.
Tooru Tanaka Toshiyuki Yamaguchi Akihiro Wakahara Akira Yoshida Ryoichi Taniguchi Yatsuka Matsuda Masatoshi Fujishiro 《Solar Energy Materials & Solar Cells》2003,75(1-2):115-120
Radiation damages due to 8 MeV electron irradiation in electrical properties of CuInSe2 thin films have been investigated. The n-type CuInSe2 films in which the carrier concentration was about 3×1016 cm−3, were epitaxially grown on a GaAs(0 0 1) substrate by RF diode sputtering. No significant change in the electrical properties was observed under the electron fluence <3×1016 e cm−2. As the electron fluence exceeded 1017 e cm−2, both the carrier concentration and Hall mobility slightly decreased. The carrier removal rate was estimated to be about 0.8 cm−1, which is slightly lower than that of III–V compound materials. 相似文献
8.
9.
T Kimura I Hashimoto M Nishikawa JI Fujisawa 《Canadian Metallurgical Quarterly》1996,78(11-12):1075-1080
Human immunodeficiency virus type-1 (HIV-1) Rev acts by inducing the specific nucleocytoplasmic transport of a class of incompletely spliced RNAs that encodes the viral structural proteins. The transfection of HeLa cells with a rev-defective HIV-1 expression plasmid, however, resulted in the export of overexpressed, intron-containing species of viral RNAs, possibly through a default process of nuclear retention. Thus, this system enabled us to directly compare Rev+ and Rev+ cells as to the usage of RRE-containing mRNAs by the cellular translational machinery. Biochemical examination of the transfected cells revealed that although significant levels of gag and env mRNAs were detected in both the presence and absence of Rev, efficient production of viral proteins was strictly dependent on the presence of Rev. A fluorescence in situ hybridisation assay confirmed these findings and provided further evidence that even in the presence of Rev, not all of the viral mRNA was equally translated. At the early phase of RNA export in Rev+ cells, gag mRNA was observed throughout both the cytoplasm and nucleoplasm as uniform fine stippling. In addition, the mRNA formed clusters mainly in the perinuclear region, which were not observed in Rev+ cells. In the presence of Rev, expression of the gag protein was limited to these perinuclear sites where the mRNA accumulated. Subsequent staining of the cytoskeletal proteins demonstrated that in Rev+ cells gag mRNA is colocalized with beta-actin in the sites where the RNA formed clusters. In the absence of Rev, in contrast, the gag mRNA failed to associate with the cytoskeletal proteins. These results suggest that in addition to promoting the emergence of intron-containing RNA from the nucleus, Rev plays an important role in the compartmentation of translation by directing RRE-containing mRNAs to the beta-actin to form the perinuclear clusters at which the synthesis of viral structural proteins begins. 相似文献
10.
M Nishikawa P Chowdhury K Takaori GT Blevins PL Rayford 《Canadian Metallurgical Quarterly》1998,9(2):26-30
Excitability of functionally different alpha-motoneurons was studied in 62 patients with gunshot injuries of nervous trunks of lower extremities both before and during process of rehabilitation by means of physical factors. The correlation of reactions of spinal cord motoneurons and the degree of injuries of nervous trunks was observed. Neuroapraxia of nervous trunks was accompanied by multidirectional alterations in reflex activity of large and small alpha-motoneurons. It was depressed in axonothermesis and lost in simultaneous full anatomic interruption of ischiatic nerve and trunks of both fibular and tibial nerves. Under influence of physical factors the function of motoneurons was normalized in neuroapraxia and was improved in axonothermesis of nervous trunks. 相似文献