全文获取类型
收费全文 | 789篇 |
免费 | 57篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 226篇 |
金属工艺 | 17篇 |
机械仪表 | 23篇 |
建筑科学 | 34篇 |
矿业工程 | 1篇 |
能源动力 | 11篇 |
轻工业 | 124篇 |
水利工程 | 13篇 |
石油天然气 | 19篇 |
无线电 | 54篇 |
一般工业技术 | 146篇 |
冶金工业 | 83篇 |
原子能技术 | 2篇 |
自动化技术 | 86篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 6篇 |
2021年 | 28篇 |
2020年 | 18篇 |
2019年 | 11篇 |
2018年 | 36篇 |
2017年 | 24篇 |
2016年 | 42篇 |
2015年 | 27篇 |
2014年 | 43篇 |
2013年 | 63篇 |
2012年 | 61篇 |
2011年 | 59篇 |
2010年 | 44篇 |
2009年 | 38篇 |
2008年 | 43篇 |
2007年 | 49篇 |
2006年 | 35篇 |
2005年 | 28篇 |
2004年 | 25篇 |
2003年 | 24篇 |
2002年 | 12篇 |
2001年 | 11篇 |
2000年 | 12篇 |
1999年 | 10篇 |
1998年 | 24篇 |
1997年 | 16篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有846条查询结果,搜索用时 15 毫秒
91.
Valérie Finidori-Logli Anne-Geneviève Bagnères Dirk Erdmann Wittko Francke Jean-Luc Clément 《Journal of chemical ecology》1996,22(11):2063-2079
The sexual behavior of the ectoparasitoidDiglyphus isaea is described. Recognition of the female by the male occurs at close range. Males initiate courtship behavior in the presence of a living female regardless of age, as well as in the presence of a female killed by freezing. Courtship behavior is not observed in the presence of a dead female washed with organic solvents but could be elicited using a lure covered with a female organic extract. These findings demonstrate that each sex develops a specific chemical signature that can be dissolved in hexane and transferred to a lure. Analysis of organic extracts by gas chromatography revealed chemical dimorphism between the two sexes. Gas chromatography coupled with mass spectrometry showed that the main components in females were esters of medium-chain fatty acids and long-chain 11-alcohols. There were few hydrocarbons. Female esters, which were present in only small proportions in males, were recovered in the nonhydrocarbon fraction obtained after fractionation of the total extract on a silica-filled microcolumn as a mixture containing 11-heneicosyl, 11-docosyl, 11-tricosyl, 11-tetracosyl, and 11-pentacosyl octanoate, and 11-docosyl, 11-tricosyl, 11-tetracosyl, and 11-pentacosyl decanoate. These results demonstrate that there is a specific gender-related chemical signature. 相似文献
92.
Mde L Chauffaille RM Valério CM Diniz MM Sim?es S Enokihara N Michalany KV Ferreira JA Martinez KM Hassun AN Atallah J Kerbauy 《Canadian Metallurgical Quarterly》1998,116(1):1625-1628
The authors present a rare case of Langerhans cell histiocytosis in a 31 year old female patient with vulvar, peri-anal and oral lesions, diabetes insipidus, pulmonary skin and bone infiltrations. Skin biopsy immunohistochemistry presented positive S100 protein and vimentin, but the diagnosis was done with the demonstration of Birbeck granules with electronic microscopy. The treatment was based on systematical chemotherapy although vulvar lesion has a bad response to chemotherapy. 相似文献
93.
94.
The complete sets of spectra of the optical fundamental functions for amorphous and polycrystalline beryllium oxides in the energy range 0–40 eV are determined and compared for the first time. The general features of the spectra and their dependence on the long-range order are revealed. The basic parameters of the optical transitions in the range 0–40 eV for amorphous and polycrystalline BeO are obtained for the first time. 相似文献
95.
The complete sets of spectra of the optical fundamental functions for porous films and single crystals of palladium oxide are determined in the range 1–6 eV. The main features of these functions and their dependences on the long-range order perfection of the structure are revealed. 相似文献
96.
97.
Victoria Fernández Azahara Díaz Álvaro Blanco Jesús Val 《Journal of the science of food and agriculture》2009,89(13):2323-2330
BACKGROUND: A strategy to supply Ca directly to fruits as a tool for improving peach quality has been devised and tested under field conditions. Since peaches in the area of study (Calanda, Spain) are routinely bagged shortly after thinning, a method based on the application of Ca gels to the fruit surface was introduced. The effect of surface treatments was assessed in terms of quality, nutrient balance and surface deposition. RESULTS: Application of Ca‐containing formulations increased mesocarp and exocarp Ca concentrations, providing evidence for the penetration of Ca through the peach skin. Surface Ca treatments had a particular mode of deposition and in some instances improved the shelf life of fruits without affecting their quality. CONCLUSION: Surface treatment with Ca‐containing gels appears to be a viable approach to increase fruit Ca, quality and storability of bagged peach cultivars and should be optimised in future studies. Copyright © 2009 Society of Chemical Industry 相似文献
98.
M del Val Gomez FG Gallardo J Cobo JM Castro-Beiras 《Canadian Metallurgical Quarterly》1995,36(12):2211-2213
The purpose of this study was to investigate the significance of abnormal 67Ga-citrate skull uptake in AIDS patients with mycobacterioses. METHODS: Gallium-67 scans of 39 HIV-positive patients who have been diagnosed with mycobacterioses were analyzed; the scans of 15 consecutive HIV-positive patients without mycobacterioses were also reviewed as a control group. The skull was chosen to assess bone marrow uptake because of the absence of overlapping structures. RESULTS: Twenty-nine of 39 (74%) patients with mycobacterial infections had disseminated disease. Gallium-67 uptake in the skull was visualized in 24 of these 29 patients (82%). One of the patients without disseminated disease and one patient in the control group (n = 15) showed skull uptake. CONCLUSION: Abnormal 67Ga skull uptake appears to be a sensitive (82%) and specific (82%) indicator of disseminated mycobacterial infection in HIV-positive patients. 相似文献
99.
100.
Comments that criterion-related validity studies are often not technically feasible because sample sizes are inadequate for necessary statistical power (e.g., .90). Effect sizes are frequently overestimated because of a failure to consider the combined effects of range restriction and criterion unreliability, both of which attenuate validity coefficients. Restricted validities must therefore be estimated by applying appropriate correction formulas. In this study the corrections are made for the multiple prediction case. Required sample sizes, determined using the univariate power model, are presented for a range of unit-weighted predictors, for varying degrees of restriction, and for power levels of .50 and .90. The advantage of multiple predictors is shown by comparing their required sample size to that of the best single predictor. For a given power, effect size is clearly the major determinant of required sample size. Implications for applied research are discussed. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献