全文获取类型
收费全文 | 1042篇 |
免费 | 39篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 22篇 |
综合类 | 2篇 |
化学工业 | 243篇 |
金属工艺 | 27篇 |
机械仪表 | 25篇 |
建筑科学 | 7篇 |
能源动力 | 20篇 |
轻工业 | 55篇 |
无线电 | 89篇 |
一般工业技术 | 193篇 |
冶金工业 | 317篇 |
原子能技术 | 26篇 |
自动化技术 | 57篇 |
出版年
2022年 | 8篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 15篇 |
2017年 | 11篇 |
2016年 | 13篇 |
2015年 | 15篇 |
2014年 | 19篇 |
2013年 | 52篇 |
2012年 | 24篇 |
2011年 | 31篇 |
2010年 | 26篇 |
2009年 | 39篇 |
2008年 | 35篇 |
2007年 | 27篇 |
2006年 | 26篇 |
2005年 | 29篇 |
2004年 | 20篇 |
2003年 | 22篇 |
2002年 | 21篇 |
2001年 | 23篇 |
2000年 | 26篇 |
1999年 | 35篇 |
1998年 | 133篇 |
1997年 | 74篇 |
1996年 | 39篇 |
1995年 | 34篇 |
1994年 | 28篇 |
1993年 | 35篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 19篇 |
1981年 | 19篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 16篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1972年 | 5篇 |
排序方式: 共有1083条查询结果,搜索用时 15 毫秒
71.
Interannual variations in terrestrial carbon cycle over tropical rainforests affect the global carbon cycle. Terrestrial ecosystem models show the interannual relationship between climate changes due to El Niño‐Southern Oscillation (ENSO) and net primary production over tropical rainforests. However, we need an independent analysis using satellite‐based vegetation index and climate parameters. In the present study, we extracted the ENSO‐related interannual variations from time‐series in Normalized Difference Vegetation Index (NDVI) and climate data from 1981 to 2000, and analysed their relevance. We detected relationships among NDVI, ENSO, and climate parameters from long‐term data with negative NDVI–ENSO, NDVI–temperature, and positive NDVI–precipitation relations. These correlations suggest that interannual variability in vegetation activities over tropical rainforests could be extracted from NDVI time‐series despite noise components in NDVI data, and that interannual changes in precipitation and temperature caused by ENSO play a more important role in vegetation activities over tropical rainforests than in incoming surface solar radiation. 相似文献
72.
73.
74.
75.
3-Fluorobenzoic acid adsorbed on Au(1 1 1), Au(1 0 0) and Au(1 1 0) electrodes has been investigated using in situ IR reflection spectroscopy, UV-visible reflectivity measurements, and differential capacity measurements. As determined by IR reflection spectroscopy, the vertically adsorbed 3-fluorobenzoate is the predominant species at positive potentials, and the flat-lying type is adsorbed at negative potentials. In the UV-visible reflectivity measurements, the reflectivity changes for the vertically adsorbed and flat-lying 3-fluorobenzoates on the Au(1 0 0) electrode were observed at different frequency regions. No UV-visible reflectivity signal was observed for the Au(1 1 0) electrode, and it was proved that the UV-visible reflectivity change has a strong single crystal surface dependence. For the vertical configuration, a large contribution between the 5d orbital of Au and the 2p orbital of oxygen in 3-fluorobenzoate was found for the cluster model by DFT calculation. 相似文献
76.
Naoki Uchida Yoshie Maitani Yoshiharu Machida Masayuki Nakagaki Tsuneji Nagai 《Drug development and industrial pharmacy》1991,17(12):1625-1634
The nasal drug absorption and the effect of absorption promoters have been studied in rabbits. Nasal mucosa excised from rabbits was mounted as a flat sheet in an in vitro chamber. The result indicates that the change in the porosity of the membrane by pretreatment with bile salts increased the permeability coefficient of sodium chloride in the nasal membrane. The permeabilities of dextran derivatives were enhanced by pretreatment with sodium glycocholate (GC). The permeability coefficient (P) of fluorescein isothiocyanate diethylaminoethyl dextran 相似文献
77.
In human-centered design activities, each designer has his or her own ideas about emotional aspect (or kansei) of new products. It is a key issue to share this vague kansei-idea appropriately at the earliest stage of design activities. This paper shows a novel ontological engineering approach to support kansei-idea sharing. The approach focuses on an idea explanation style as the wisdom of the design team. Ontological engineering has been making contributions to systematize knowledge and vocabulary by modeling them. Needless to say, it is difficult to model the vague kansei-idea itself. However, if the modeled object is shifted from the kansei-idea to the kansei-idea explanation style, it can provide the benefit of modeling. We investigated the effectiveness of the ontological engineering approach, and concluded that to construct an ontological framework of designers’ explanations is especially useful regarding these points: clarification of the essence of the explanation style, discovery of problems in explanations, and analyzing difficulties in acquiring explanation style for novices. From the investigation, what we can support and how a support system should be designed became clear. Furthermore, we built a kansei-idea sharing support system, and obtained the results of its initial trials. 相似文献
78.
Toru Ikegami Tomotake Morita Shunichi Nakayama Hideyuki Negishi Dai Kitamoto Keiji Sakaki Yasunori Oumi Tsuneji Sano Kenji Haraya Hiroshi Yanagishita 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(8):1172-1177
BACKGROUND: Pervaporation employing ethanol‐permselective silicalite membranes as an alternative to distillation is a promising approach for refining low‐concentration bioethanol solutions. However, to make the separation process practicable, it is extremely important to avoid the problems caused by the adsorption of succinate on the membrane during the separation process. In this work, the pervaporation of an ethanol fermentation broth without succinate was investigated, as well as the influence of several fermentation broth nutrient components. RESULTS: Candida krusei IA‐1 produces an extremely low level of succinate. The decrease in permeate ethanol concentration through a silicone rubber‐coated silicalite membrane during the separation of low‐succinate C. krusei IA‐1 fermentation broth was significantly improved when compared with that obtained using Saccharomyces cerevisiae broth. By treating the fermentation broth with activated carbon, bioethanol was concentrated as efficiently as with binary mixtures of ethanol/water. The total flux was improved upto 56% of that obtained from the separation of binary mixtures, compared with 43% before the addition of activated carbon. Nutrients such as peptone, yeast extract and corn steep liquor had a negative effect on pervaporation, but this response was distinct from that caused by succinate. CONCLUSION: For consistent separation of bioethanol from C. krusei IA‐1 fermentation broth by pervaporation, it is useful to treat the low nutrient broth with activated carbon. To further improve pervaporation performance, it will be necessary to suppress the accumulation of glycerol. Copyright © 2009 Society of Chemical Industry 相似文献
79.
The effect of the constituting amino acid residue [Glu(OBzl)] number on the chiral recognition ability was investigated. Chiral recognition sites were prepared from oligopeptide derivatives (constituting amino acid residue number = three–five) by adopting alternative molecular imprinting. It was made clear that with a constituting amino acid residue number of four, the tetrapeptide derivative of Glu(OBzl) is the best candidate material to generate a chiral recognition site among eight types of oligopeptide derivatives in the study. The affinity constant between Ac‐L ‐Trp and a chiral recognition site ranged from 3.4 × 103 to 1.08 × 104 mol?1 dm3, depending on the number of Glu(OBzl) residues in an oligopeptide derivative. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1302–1309, 2005 相似文献
80.
Yoshihiko Nakata Satoshi Ninomiya Chikage Imada Masafumi Nagai Takaaki Aoki Jiro Matsuo Nobutsugu Imanishi 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2005,230(1-4):489-494
We have measured both secondary neutral and ionized particles from an InSb target under 3.0 MeV Si ion bombardment. Measurements of both ions and neutrals have not been carried out so far in the MeV-energy range. The mass spectra and axial emission energy distributions of secondary particles were investigated. Secondary ions were measured with a linear- and a reflective-type time-of-flight technique, whereas secondary neutral particles were photo-ionized by a UV pulsed laser (ArF: 193 nm) and measured with a reflective-type time-of-flight technique. Different results were obtained for neutral particles in comparison with ionized particles. The mean energy of neutral Sb atoms was much lower than that of neutral In atoms, whereas the mean energies of secondary In and Sb ions were nearly equal. 相似文献