全文获取类型
收费全文 | 2178篇 |
免费 | 37篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 16篇 |
化学工业 | 235篇 |
金属工艺 | 22篇 |
机械仪表 | 42篇 |
建筑科学 | 56篇 |
矿业工程 | 3篇 |
能源动力 | 43篇 |
轻工业 | 74篇 |
水利工程 | 14篇 |
石油天然气 | 3篇 |
无线电 | 120篇 |
一般工业技术 | 253篇 |
冶金工业 | 1229篇 |
原子能技术 | 10篇 |
自动化技术 | 108篇 |
出版年
2022年 | 13篇 |
2021年 | 21篇 |
2020年 | 12篇 |
2019年 | 16篇 |
2018年 | 13篇 |
2017年 | 13篇 |
2016年 | 13篇 |
2015年 | 19篇 |
2014年 | 20篇 |
2013年 | 58篇 |
2012年 | 33篇 |
2011年 | 42篇 |
2010年 | 45篇 |
2009年 | 41篇 |
2008年 | 58篇 |
2007年 | 55篇 |
2006年 | 28篇 |
2005年 | 49篇 |
2004年 | 29篇 |
2003年 | 27篇 |
2002年 | 30篇 |
2001年 | 23篇 |
2000年 | 27篇 |
1999年 | 52篇 |
1998年 | 384篇 |
1997年 | 220篇 |
1996年 | 150篇 |
1995年 | 77篇 |
1994年 | 80篇 |
1993年 | 84篇 |
1992年 | 16篇 |
1991年 | 19篇 |
1990年 | 23篇 |
1989年 | 33篇 |
1988年 | 26篇 |
1987年 | 28篇 |
1986年 | 9篇 |
1985年 | 25篇 |
1984年 | 12篇 |
1983年 | 16篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 20篇 |
1979年 | 7篇 |
1978年 | 12篇 |
1977年 | 49篇 |
1976年 | 98篇 |
1973年 | 7篇 |
1970年 | 6篇 |
1941年 | 6篇 |
排序方式: 共有2228条查询结果,搜索用时 15 毫秒
1.
Indium separation using ion exchange resins from acidic polymetallic and very diluted solutions are investigated. Since the selectivity of commercial ion exchange resins have proven to be too low for an effective separation from solutions with high content of other metals, Lewatit® TP 208 was impregnated with common extractants to enhance its properties. By resin impregnation with D2EHPA and Cyanex 272, not only the selective indium recovery was reached but also the resin capacity was increased approx. two times. The best loading and elution performance were shown by Cyanex 272-impregnated Lewatit® TP 208, increasing the indium purity in the eluate from 0.75 % to 85 %. 相似文献
2.
Katharina M. A. Kaiser 《应用聚合物科学杂志》2020,137(40):49230
Plastic-based multilayer packaging has an important function on the packaging market, but is currently not recyclable as the polymer layers used are usually thermodynamically immiscible. This work therefore follows the approach to prepare separable multilayer packaging using a packaging adhesive modified with thermally unstable adducts, and proposes a corresponding recycling process. For this purpose, typical multilayer structures (polyethylene (PE)// polyethylene terephtalate (PET), PET//aluminum, and PE//aluminum) were prepared by curing furan-/maleimide-functionalized polyurethane (PU)-prepolymers with a three-functional cross-linking agent. Adhesions of up to over 3N per 15 mm test specimen were measured or substrate failures of PET films were observed. However, heating in dimethylsulfoxide, the retro-Diels–Alder reaction takes place and the cross-linked adhesive turns thermoplastic and dissolves in the solvent. Thus, the laminate separates and the pure PE, PET, and aluminum foils can be recovered without any PU residue. 相似文献
3.
Freddy A. Bernal Dr. Marcel Kaiser Prof. Dr. Bernhard Wünsch Prof. Dr. Thomas J. Schmidt 《ChemMedChem》2020,15(1):68-78
Protozoal infections are still a global health problem, threatening the lives of millions of people around the world, mainly in impoverished tropical and sub-tropical regions. Thus, in view of the lack of efficient therapies and increasing resistances against existing drugs, this study describes the antiprotozoal potential of synthetic cinnamate ester analogues and their structure-activity relationships. In general, Leishmania donovani and Trypanosoma brucei were quite susceptible to the compounds in a structure-dependent manner. Detailed analysis revealed a key role of the substitution pattern on the aromatic ring and a marked effect of the side chain on the activity against these two parasites. The high antileishmanial potency and remarkable selectivity of the nitro-aromatic derivatives suggested them as promising candidates for further studies. On the other hand, the high in vitro potency of catechol-type compounds against T. brucei could not be extrapolated to an in vivo mouse model. 相似文献
4.
D Galasko T Saitoh Y Xia LJ Thal R Katzman LR Hill L Hansen 《Canadian Metallurgical Quarterly》1994,44(10):1950-1951
We determined apolipoprotein E (ApoE) genotypes in 122 autopsied demented patients. The frequency of the ApoE epsilon 4 allele was 39.6% in Alzheimer's disease (AD), 29.0% in the Lewy body variant of AD (LBV), and 6.25% in diffuse Lewy body disease. For AD and LBV patients, the epsilon 4 frequency was significantly higher than that reported in nondemented controls (10 to 15%). Therefore, LBV and AD share ApoE epsilon 4 as a genetic risk factor, providing further evidence that these conditions overlap. 相似文献
5.
6.
7.
This work aims to shed more light on the issue of why smart antennas haven't yet penetrated the market despite all the research efforts that have been put into the technology. The paper looks at this issue from various perspectives and subdivides the discussions into fixed or nomadic and high mobility applications because of the different types of markets, demands, and technological barriers. 相似文献
8.
9.
R. H. Howell P. A. Sterne M. J. Fluss J. H. Kaiser K. Kitazawa H. Kojima 《Journal of Superconductivity and Novel Magnetism》1994,7(1):169-173
High-statistics (>4 × 108 counts), room-temperature measurements of the electron-positron momentum density of La2?x Sr x CuO4 have been performed for samples with Sr concentrations of x=0.0, 0.1, 0.13, and 0.2. These spectra have been analyzed in conjunction with theoretical calculations of the electron-positron momentum density. The metallic samples show features consistent with the presence of a Fermi surface, but its evolution with increasing Sr concentration does not follow the predictions of band theory. These results may indicate the effects of electron-electron correlation on the electron momentum distribution in the Cu-O plane. 相似文献
10.
SA Cook RT Bronson LR Donahue N Ben-Arie MT Davisson 《Canadian Metallurgical Quarterly》1997,8(2):108-112
OBJECTIVE: To discuss the case of an 8-yr-old boy with an aneurysmal bone cyst of the right proximal humerus, including the features imaged on plain film radiography, computed tomography (CT), magnetic resonance imaging (MRI), including spin echo and fast field echo imaging. CLINICAL FEATURES: The patient suffered for 1 yr from intermittent but progressive pain in his right upper arm and shoulder area. There was no history of trauma or known systemic disease. There was decreased range of motion in abduction of the glenohumeral joint and pain on focal pressure along the deltoid muscle. A complete imaging evaluation consisting of plain film radiography, CT and MRI was performed, which revealed the classical imaging features of an aneurysmal bone cyst. An additional cystic lesion was detected by the MRI that was not appreciated on the plain films or CT. INTERVENTION AND OUTCOME: The patient was referred for biopsy to confirm the preliminary diagnosis of aneurysmal bone cyst. No treatment was instituted. CONCLUSION: Evaluation of aneurysmal bone cyst may be completed with CT scanning and more specifically with MRI MRI coronal T2, weighted images are advantageous for visualization of the main cystic lesion and any additional cysts. Fast field echo images show a better contrast between the cyst and bone marrow with extension of the cyst into the epiphysis as evident in this case. Follow-up studies revealed complete healing of the cyst with only residual densities in the humeral metaphyseal area. 相似文献