全文获取类型
收费全文 | 3680篇 |
免费 | 198篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 19篇 |
综合类 | 1篇 |
化学工业 | 835篇 |
金属工艺 | 77篇 |
机械仪表 | 114篇 |
建筑科学 | 154篇 |
矿业工程 | 7篇 |
能源动力 | 87篇 |
轻工业 | 898篇 |
水利工程 | 53篇 |
石油天然气 | 33篇 |
无线电 | 203篇 |
一般工业技术 | 672篇 |
冶金工业 | 400篇 |
原子能技术 | 17篇 |
自动化技术 | 311篇 |
出版年
2024年 | 8篇 |
2023年 | 29篇 |
2022年 | 67篇 |
2021年 | 133篇 |
2020年 | 85篇 |
2019年 | 96篇 |
2018年 | 112篇 |
2017年 | 101篇 |
2016年 | 115篇 |
2015年 | 95篇 |
2014年 | 144篇 |
2013年 | 237篇 |
2012年 | 242篇 |
2011年 | 323篇 |
2010年 | 181篇 |
2009年 | 177篇 |
2008年 | 219篇 |
2007年 | 198篇 |
2006年 | 179篇 |
2005年 | 103篇 |
2004年 | 87篇 |
2003年 | 107篇 |
2002年 | 108篇 |
2001年 | 73篇 |
2000年 | 49篇 |
1999年 | 51篇 |
1998年 | 114篇 |
1997年 | 78篇 |
1996年 | 58篇 |
1995年 | 57篇 |
1994年 | 29篇 |
1993年 | 39篇 |
1992年 | 16篇 |
1991年 | 25篇 |
1990年 | 4篇 |
1989年 | 13篇 |
1988年 | 16篇 |
1987年 | 5篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 13篇 |
1983年 | 4篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 12篇 |
1974年 | 3篇 |
排序方式: 共有3881条查询结果,搜索用时 531 毫秒
991.
Gas–liquid interfacial area in the oxygen absorption to oil‐in‐water emulsions in an airlift reactor
The present work includes an exhaustive study about gas–liquid interfacial area between gas phase and liquid heterogeneous medium generated in an airlift bioreactor. The system studied is composed by water, methyl ricinoleate (MR), and Tween‐80, since it is the base of the medium used for the production of γ‐decalactone, a peach‐like aroma compound of industrial interest that can be produced biotechnologically through the biotransformation of ricinoleic acid, by the yeast Yarrowia lipolytica. Experimental results allow describing the hydrodynamic behaviour of the gas phase into the biphasic medium. 相似文献
992.
Anchovy fish meal with an approximate uniform moisture content of 10% was used for this study. Vapor adsorption isotherms were determined at 25 ° C, 35 ° C and 45 ° C. The differential and integral thermodynamic properties were estimated using the Othmer method. The isosteric heat or differential enthalpy, as a function of moisture content, showed a maximum value around 4.5 g of water/100 g d. s. The heat of sorption increased gradually with an increase in sorbed water until reaching its maximum value near the monolayer, and at a given moisture content, decreasing with temperature. The molar entropy values obtained were high at low water contents and fell to a minimum near the monolayer value. 相似文献
993.
Flávio C. Cabrera Deuber L. S. Agostini Renivaldo J. dos Santos Silvio R. Teixeira Miguel A. Rodríguez‐Pérez Aldo E. Job 《应用聚合物科学杂志》2013,130(1):186-192
Natural rubber/gold nanoparticles membranes (NR/Au) were studied by ultrasensitive detection and chemical analysis through surface‐enhanced Raman scattering and surface‐enhanced resonance Raman scattering in our previous work (Cabrera et al., J. Raman Spectrosc. 2012, 43, 474). This article describes the studies of thermal stability and mechanical properties of SERS‐active substrate sensors. The composites were prepared using NR membranes obtained by casting the latex solution as an active support (reducing/establishing agents) for the incorporation of colloidal gold nanoparticles (AuNPs). The nanoparticles were synthesized by in situ reduction at different times. The characterization of these sensors was carried out by thermogravimetry, differential scanning calorimetry, scanning electron microscopy (SEM) microscopy, and tensile tests. It is suggested an influence of nanoparticles reduction time on the thermal degradation of NR. There is an increase in thermal stability without changing the chemical properties of the polymer. For the mechanical properties, the tensile rupture was enhanced with the increase in the amount of nanoparticles incorporated in the material. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
994.
Patrícia Valentão Pedro Trindade Daniela Gomes Paula Guedes de Pinho Teresa Mouga Paula B. Andrade 《Food chemistry》2010
The chemical composition of green Codium tomentosum Stackhouse and red Plocamium cartilagineum (Linnaeus) P.S. Dixon seaweeds from the Atlantic Ocean surrounding Portugal was studied. For the first time, the profile of organic acids was analysed in these matrices: seven and four organic acids were detected in green and red species, respectively. In P. cartilagineum these compounds were present in vestigial amounts, whilst C. tomentosum exhibited a higher content, with oxalic acid being the main compound. Phenolics, UV-absorbing compounds, were absent in both species. Volatiles profile was also determined for the first time and a total of 41 compounds were identified, which included alcohols, aldehydes, esters, halogenated compounds, ketones, monoterpenes (namely terrestrial ones), norisoprenoid derivatives, amongst others. Norisoprenoid derivatives and aldehydes were predominant. The main volatiles in green and red seaweeds were limonene and benzophenone, respectively. Additionally, both species revealed considerable antioxidant activity against both reactive oxygen (superoxide radical) and reactive nitrogen (nitric oxide) species, in a concentration-dependent manner. 相似文献
995.
Athanasios Bamis Dimitrios Lymberopoulos Thiago Teixeira Andreas Savvides 《Personal and Ubiquitous Computing》2010,14(6):473-487
The in-house monitoring of elders using intelligent sensors is a very desirable service that has the potential of increasing
autonomy and independence while minimizing the risks of living alone. Because of this promise, the efforts of building such
systems have been spanning for decades, but there is still a lot of room for improvement. Driven by the recent technology
advances in many of the required components, in this article, we present a scalable framework for detailed behavior interpretation.
Our framework supports in-house monitoring of elders using an intelligent gateway and a set of cheap commercially available
sensors, in addition to more advanced camera-based human localization sensors and a client for GPS-enabled mobile phones that
provides monitoring when outdoors. In this article, we report our experiences and present our current progress in three main
components: sensors, middleware, and behavior interpretation mechanisms spanning from simple programmable rule-based alerts
to algorithms for extracting the temporal routines of individuals. 相似文献
996.
997.
Influence of productivity and processing method on physicochemical characteristics of white button mushrooms in Brazil 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Journal of the science of food and agriculture》网站下载免费的PDF全文](/ch/ext_images/free.gif)
998.
José Sereno Paulo Rodrigues-Santos Helena Vala Petronila Rocha-Pereira Rui Alves Jo?o Fernandes Alice Santos-Silva Eugénia Carvalho Frederico Teixeira Flávio Reis 《International journal of molecular sciences》2014,15(5):8979-8997
Cyclosporin A (CsA), a calcineurin inhibitor, remain the cornerstone of immunosuppressive regimens, regardless of nephrotoxicity, which depends on the duration of drug exposure. The mechanisms and biomarkers underlying the transition from CsA-induced renal dysfunction to nephrotoxicity deserve better elucidation, and would help clinical decisions. This study aimed to clarify these issues, using a rat model of short- and long-term CsA (5 mg/kg bw/day) treatments (3 and 9 weeks, respectively). Renal function was assessed on serum and urine; kidney tissue was used for histopathological characterization and gene and/or protein expression of markers of proliferation, fibrosis and inflammation. In the short-term, creatinine and blood urea nitrogen (BUN) levels increased and clearances decreased, accompanied by glomerular filtration rate (GFR) reduction, but without kidney lesions; at that stage, CsA exposure induced proliferating cell nuclear antigen (PCNA), transforming growth factor beta 1 (TGF-β1), factor nuclear kappa B (NF-κβ) and Tumor Protein P53 (TP53) kidney mRNA up-regulation. In the long-term treatment, renal dysfunction data was accompanied by glomerular and tubulointerstitial lesions, with remarkable kidney mRNA up-regulation of the mammalian target of rapamycin (mTOR) and the antigen identified by monoclonal antibody Ki-67 (Mki67), accompanied by mTOR protein overexpression. Transition from CsA-induced renal dysfunction to nephrotoxicity is accompanied by modification of molecular mechanisms and biomarkers, being mTOR one of the key players for kidney lesion evolution, thus suggesting, by mean of molecular evidences, that early CsA replacement by mTOR inhibitors is indeed the better therapeutic choice to prevent chronic allograft nephropathy. 相似文献
999.
1000.
Dr. Riccardo Rubbiani Thomas N. Zehnder Cristina Mari Dr. Olivier Blacque Dr. Koushik Venkatesan Prof. Dr. Gilles Gasser 《ChemMedChem》2014,9(12):2781-2790
Six phosphorescent (2‐phenyl)pyridine (ppy) gold(III) 2,4,6‐tris(trifluoromethyl)phenyl (FMes) complexes were synthesized and investigated for their anticancer potential. The compounds demonstrated strong antiproliferative activity, with EC50 values in the low micromolar range, along with significant accumulation in HeLa cancer cells after treatment for only 6 h (up to 119 ng gold per milligram of protein as measured by high‐resolution continuum source atomic spectroscopy). Enzyme inhibition studies showed interaction of the gold(III) complexes with thioredoxin reductase (TrxR), a key homeostasis‐regulation flavoprotein. TrxR was inhibited with IC50 values in the micromolar range. Furthermore, five of the complexes displayed selectivity toward TrxR against glutathione reductase (GR, a disulfide reductase structurally related to TrxR) by up to >49‐fold. Because no major differences in bioactivity were observed across the series, [(ppy)Au(FMes)(PPh3)OTf] (complex 4 ) was chosen for further in‐depth biological characterization. Complex 4 was also found to interact with guanosine monophosphate in 1H NMR studies under long incubation times. Interestingly, 4 induced a significant increase in intracellular levels of reactive oxygen species, which led to late apoptotic events and cytocidal effects. 相似文献