全文获取类型
收费全文 | 647篇 |
免费 | 22篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 6篇 |
化学工业 | 114篇 |
金属工艺 | 9篇 |
机械仪表 | 2篇 |
建筑科学 | 54篇 |
能源动力 | 18篇 |
轻工业 | 85篇 |
水利工程 | 1篇 |
石油天然气 | 18篇 |
无线电 | 24篇 |
一般工业技术 | 74篇 |
冶金工业 | 179篇 |
原子能技术 | 1篇 |
自动化技术 | 85篇 |
出版年
2024年 | 4篇 |
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 19篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 18篇 |
2017年 | 14篇 |
2016年 | 17篇 |
2015年 | 6篇 |
2014年 | 13篇 |
2013年 | 56篇 |
2012年 | 21篇 |
2011年 | 35篇 |
2010年 | 32篇 |
2009年 | 30篇 |
2008年 | 35篇 |
2007年 | 36篇 |
2006年 | 22篇 |
2005年 | 24篇 |
2004年 | 21篇 |
2003年 | 17篇 |
2002年 | 20篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 28篇 |
1997年 | 17篇 |
1996年 | 17篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 12篇 |
1991年 | 3篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 8篇 |
1969年 | 1篇 |
排序方式: 共有670条查询结果,搜索用时 12 毫秒
61.
Gonzalo Allo Ayala 《TEST》1977,28(2-3):3-22
Sumario En la primera parte de este trabajo, se estudia la existencia de estrategias óptimas, en el modelo teórico (Pa F, ρ (Pa,f)) (ref. 3), generalización de un S-juego, dondeP
a es un conjunto de probabilidades finitamente aditivas, yF un subconjunto convexo de funciones reales acotadas. A continuación se analizan las clases de estrategias y se obtiene una
clase de estrategiasp
a-Bayes, más amplia que la de Bayes β, y Bayes extendida βo, que tiene la propiedad de contener siempre a la clase de estrategias admisibles. Se demuestra su completitud con hipótesis
adicionales, y se obtienen resultados relativos a estrategias σ-aditivas, como casos particulares.
Trabajo realizado con la beca March de Matemáticas, convocatoria 1973–74. 相似文献
62.
63.
64.
P. B. A. Fechine M. J. S. da Rocha M. R. P. Santos F. M. M. Pereira A. S. de Menezes J. M. A. Almeida J. C. Góes A. P. Ayala A. S. B. Sombra 《Journal of Materials Science: Materials in Electronics》2008,19(10):973-980
In this article we will study the structural and electrical properties of PbTiO3 (PTO) screen-printed thick films. These properties can change with synthetic routes employed for synthesis of PTO. The ceramic powder has been synthesized by mechanical alloying and solid state route. This material crystallizes in the tetragonal system, with space group P4mm and unit cell dimensions a = b = 3.904, c = 4.152 Å, and Z = 1. From our results, it was observed that PTO obtained by mechanical alloying provides smaller crystallite size. The Rietveld refinement showed that the samples synthesized by mechanical alloying and solid state route crystallize in the tetragonal system but with different cell parameters. The Raman shifts of these films agree with modes from literature. However, some displacements happen, because the morphology and structural characteristics of the thick films are different, compared to single crystal and thin film. The photomicrographs of the PTO thick films showed that the choice of synthetic routes obtained samples with different microstructures. 相似文献
65.
Laura A Miller Kathy A Stubblefield Robert D Lipschutz Blair A Lock Todd A Kuiken 《IEEE transactions on neural systems and rehabilitation engineering》2008,16(1):46-50
Targeted reinnervation is a surgical technique developed to increase the number of myoelectric input sites available to control an upper-limb prosthesis. Because signals from the nerves related to specific movements are used to control those missing degrees-of-freedom, the control of a prosthesis using this procedure is more physiologically appropriate compared to conventional control. This procedure has successfully been performed on three people with a shoulder disarticulation level amputation and three people with a transhumeral level amputation. Performance on timed tests, including the box-and-blocks test and clothespin test, has increased two to six times. Options for new control strategies are discussed. 相似文献
66.
Chemical contaminants, health indicators, and reproductive biomarker responses in fish from the Colorado River and its tributaries 总被引:3,自引:1,他引:2
Hinck JE Blazer VS Denslow ND Echols KR Gross TS May TW Anderson PJ Coyle JJ Tillitt DE 《The Science of the total environment》2007,378(3):376-402
Common carp (Cyprinus carpio), black bass (Micropterus spp.), and channel catfish (Ictalurus punctatus) were collected from 14 sites in the Colorado River Basin (CRB) to document spatial trends in accumulative contaminants, health indicators, and reproductive biomarkers. Organochlorine residues, 2,3,7,8-tetrachlorodibenzo-p-dioxin-like activity (TCDD-EQ), and elemental contaminants were measured in composite samples of whole fish, grouped by species and gender, from each site. Selenium (Se) and mercury (Hg) concentrations in fish were elevated throughout the CRB, and pesticide concentrations were greatest in fish from agricultural areas in the Lower Colorado River and Gila River. Selenium concentrations exceeded toxicity thresholds for fish (>1.0 microg/g ww) at all CRB sites except the Gila River at Hayden, Arizona. Mercury concentrations were elevated (>0.1 microg/g ww) in fish from the Yampa River at Lay, Colorado; the Green River at Ouray National Wildlife Refuge (NWR), Utah and San Rafael, Utah; the San Juan River at Hogback Diversion, New Mexico; and the Colorado River at Gold Bar Canyon, Utah, Needles, California, and Imperial Dam, Arizona. Concentrations of p,p'-DDE were relatively high in fish from the Gila River at Arlington, Arizona (>1.0 microg/g ww) and Phoenix, Arizona (>0.5 microg/g ww). Concentrations of other formerly used pesticides including toxaphene, total chlordanes, and dieldrin were also greatest at these two sites but did not exceed toxicity thresholds. Currently used pesticides such as Dacthal, endosulfan, gamma-HCH, and methoxychlor were also greatest in fish from the Gila River downstream of Phoenix. Total polychlorinated biphenyls (PCBs; >0.11 microg/g ww) and TCDD-EQs (>5 pg/g ww) exceeded wildlife guidelines in fish from the Gila River at Phoenix. Hepatic ethoxyresorufin O-deethylase (EROD) activity was also relatively high in carp from the Gila River at Phoenix and in bass from the Green River at Ouray NWR. Fish from some sites showed evidence of contaminant exposure as indicated by fish health indicators and reproductive biomarker results. Multiple health indicators including altered body and organ weights and high health assessment index scores may be associated with elevated Se concentrations in fish from the Colorado River at Loma, Colorado and Needles. Although grossly visible external or internal lesions were found on most fish from some sites, histopathological analysis determined many of these to be inflammatory responses associated with parasites. Edema, exophthalmos, and cataracts were noted in fish from sites with elevated Se concentrations. Intersex fish were found at seven of 14 sites and included smallmouth bass (M. dolomieu), largemouth bass (M. salmoides), catfish, and carp and may indicate exposure to endocrine disrupting compounds. A high proportion of smallmouth bass from the Yampa River at Lay (70%) was intersex but the cause of this condition is unknown. Male carp, bass, and catfish with low concentrations of vitellogenin were common in the CRB. Comparatively high vitellogenin concentrations (>0.2 mg/mL) were measured in male bass from the Green River at Ouray NWR and the Colorado River at Imperial Dam and indicate exposure to estrogenic or anti-androgenic chemicals. Anomalous reproductive biomarkers including low GSI and gonadal abnormalities (calcifications, edema, and parasites) observed in fish downstream of Phoenix are likely related to the poor water-quality of the Gila River in this area. 相似文献
67.
Forty men and women were given the Moral Judgment Interview (MJI) while drinking in a natural setting and were asked a series of questions about whether they should and would drive impaired. In a second testing in an academic context, these subjects were given an alternate form of the MJI and were asked whether they drove on the previous occasion. Forty additional men and women completed the MJI in an academic context and responded to the impaired driving questions hypothetically. Results revealed that Ss scored lower on moral maturity in the social drinking contexts than in the academic contexts, especially when highly intoxicated. Ss responding hypothetically attributed more moral integrity to themselves than to others, indicating they would not drive impaired. The self-righteousness of these attributions was apparent in the behavior of Ss who drove to the social drinking settings—all but 1 drove home, however impaired. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
68.
69.
A variation of the conditional discrimination procedure defines relations between stimuli (e.g., gestural signs and their referents) and has been used to study language comprehension in California sea lions. Animals followed instructions given by a trainers' gestures designating properties of size, brightness, and location (adjectives); types of objects (nouns); and actions (verbs). The signs could be combined and recombined according to a conditional sequence or syntax. In the present study, the experimenters sought to determine whether adjectives for size had an absolute meaning (small and large), and a comparative meaning (smaller and larger). A sea lion was given experience with signs designating standards small and large spheres in commands such as large ball mouth. On transposition tests, the small ball was removed and the previously designated large ball was paired with an even larger one. The results show that the adjectives had both an absolute and a relative meaning. Object choices and searching behavior revealed that the S processed information about the relation of size as well as about the specific characteristics of sizes of spheres that instantiated the relations. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
70.
Based on the isolobal analogy of ZnCp (Cp = η5-C5H5) and ZnR (R = alkyl or aryl group) fragments with hydrogen atom and fragment [Zn(CO)2] with a CH2 carbene, the following complexes [(ZnCp)2{µ-Zn(CO)2}], 1, [(ZnPh)2{µ-Zn(CO)2}], 2, [(ZnPh){µ-Zn(CO)2}(ZnCp)], 3, [(ZnCp)2{µ-Zn2(CO)4}], 4, [(ZnPh)2{µ-Zn2(CO)4}], 5, [(ZnPh){µ-Zn(CO)2}2(ZnCp)], 6, [Zn3(CO)6], 7 and [Zn5(CO)10], 8, were built. These polynuclear zinc compounds are isolobally related to simple hydrocarbons (methane, ethane, cyclopropane and cyclopentane). They have been studied by density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) to compare the nature and topology of the Zn–Zn bond with previous studies. There are bond critical points (BCPs) between each pair of adjacent Zn centers in complexes 1–8 with Zn–Zn distances within the range 2.37–2.50 Å. The nature of the Zn–Zn bond in these complexes can be described as polar rather than pure covalent bonds. Although in a subtle way, the presence of different ligands and zinc oxidation states introduces asymmetry and polarity in the Zn–Zn bond. In addition, the Zn–Zn bond is delocalized in nature in complex 7 whereas it can be described as a localized bond for the remaining zinc complexes here studied. 相似文献