全文获取类型
收费全文 | 4486篇 |
免费 | 41篇 |
国内免费 | 1篇 |
学科分类
工业技术 | 4528篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 3篇 |
2021年 | 23篇 |
2020年 | 14篇 |
2019年 | 18篇 |
2018年 | 13篇 |
2017年 | 24篇 |
2016年 | 22篇 |
2015年 | 15篇 |
2014年 | 27篇 |
2013年 | 43篇 |
2012年 | 42篇 |
2011年 | 61篇 |
2010年 | 31篇 |
2009年 | 28篇 |
2008年 | 36篇 |
2007年 | 24篇 |
2006年 | 24篇 |
2005年 | 17篇 |
2004年 | 11篇 |
2003年 | 17篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 112篇 |
1998年 | 1199篇 |
1997年 | 666篇 |
1996年 | 475篇 |
1995年 | 223篇 |
1994年 | 209篇 |
1993年 | 224篇 |
1992年 | 26篇 |
1991年 | 70篇 |
1990年 | 64篇 |
1989年 | 58篇 |
1988年 | 52篇 |
1987年 | 56篇 |
1986年 | 43篇 |
1985年 | 45篇 |
1983年 | 11篇 |
1982年 | 20篇 |
1981年 | 23篇 |
1980年 | 32篇 |
1979年 | 2篇 |
1978年 | 12篇 |
1977年 | 104篇 |
1976年 | 258篇 |
1975年 | 5篇 |
1955年 | 7篇 |
排序方式: 共有4528条查询结果,搜索用时 15 毫秒
1.
Maria Quitrio Sandra Simes Andreia Ascenso Manuela Carvalheiro Ana Paula Leandro Isabel Correia Ana Silveira Viana Pedro Faísca Lia Ascenso Jesús Molpeceres Maria Manuela Gaspar Catarina Pinto Reis 《International journal of molecular sciences》2021,22(8)
Insulin is a peptide hormone with many physiological functions, besides its use in diabetes treatment. An important role of insulin is related to the wound healing process—however, insulin itself is too sensitive to the external environment requiring the protective of a nanocarrier. Polymer-based nanoparticles can protect, deliver, and retain the protein in the target area. This study aims to produce and characterize a topical treatment for wound healing consisting of insulin-loaded poly-DL-lactide/glycolide (PLGA) nanoparticles. Insulin-loaded nanoparticles present a mean size of approximately 500 nm and neutral surface charge. Spherical shaped nanoparticles are observed by scanning electron microscopy and confirmed by atomic force microscopy. SDS-PAGE and circular dichroism analysis demonstrated that insulin preserved its integrity and secondary structure after the encapsulation process. In vitro release studies suggested a controlled release profile. Safety of the formulation was confirmed using cell lines, and cell viability was concentration and time-dependent. Preliminary safety in vivo assays also revealed promising results. 相似文献
2.
3.
4.
Miguel Muiz‐Calvente Adrin lvarez‐Vzquez Sergio Cicero Jos A.F.O. Correia Abilio M.P. de Jesus Sergio Blasn Alfonso Fernndez‐Canteli Filippo Berto 《Fatigue & Fracture of Engineering Materials & Structures》2019,42(12):2663-2673
The fracture assessment of notched components based on cracked components approaches leads to over‐conservative failure predictions. In the research literature, several approaches are proposed to overcome this problem using an apparent fracture toughness, . Nevertheless, most of these approaches are based on deterministic assumptions despite the large and variable scatter exhibited by for different notch radii (ρ) or temperatures (T). This paper proposes a methodology for deriving a probabilistic field including the effect of temperature on the failure of notched components. First, the theory of critical distances is applied to transform each apparent fracture toughness into the equivalent fracture toughness for ρ = 0. Then, the temperature is supposed to act as a scale effect in the Weibull cumulative distribution function of the equivalent fracture toughness, and the corresponding scale effect function is derived. Finally, the applicability of the proposed methodology is illustrated by an example using two ferritic‐pearlitic steels: S275JR and S355J2. 相似文献
5.
6.
Bianca Moreira Barbosa Jorge Luiz Colodette Dalton Longue Júnior Fernando José Borges Gomes Daniela Correia Martino 《木材化学与工艺学杂志》2014,34(3):178-190
This study focused on the production of furfural from agricultural and industrial biomass residues by a hydrodistillation process. Corncobs, sugarcane bagasse, and eucalypt wood were treated with sulfuric, hydrochloric, and phosphoric acids as catalysts, with different acid concentrations (1.5 to 5.2 mol.L ?1). In addition, the eucalypt liquor from the auto-hydrolysis, kraft-dissolving pulp production process was also investigated as a source of furfural, using sulfuric and hydrochloric acids as a catalyst (0.9 and 3.9 mol.L ?1) . Furfural yields of 30.2, 25.8, and 13.9% were achieved for corncob, sugarcane bagasse, and eucalypt wood, respectively, on the basis of biomass dry weight. The efficiency of conversion from pentose to furfural using eucalypt liquor from the auto-hydrolysis kraft process was 71.5% using HCl 3.9 mol.L ?1 . Due to the presence of a high amount of pentose, corncob produced the highest amount of furfural, followed by sugarcane bagasse and then eucalypt wood. 相似文献
7.
This paper addresses current changes in the highly diverse European landscape, and the way these transitions are being treated in policy and landscape management in the fragmented, heterogeneous and dynamic context of today’s Europe. It appears that intersecting driving forces are increasing the complexity of European landscapes and causing polarising developments in agricultural land use, biodiversity conservation and cultural landscape management. On the one hand, multifunctional rural landscapes, especially in peri-urban regions, provide services and functions that serve the citizens in their demand for identity, support their sense of belonging and offer opportunities for recreation and involvement in practical landscape management. On the other hand, industrial agricultural production on increasingly large farms produces food, feed, fibre and energy to serve expanding international markets with rural liveability and accessibility as a minor issue. The intermediate areas of traditionally dominant small and family farms in Europe seem to be gradually declining in profitability. The paper discusses the potential of a governance approach that can cope with the requirement of optimising land-sharing conditions and community-based landscape development, while adapting to global market conditions. 相似文献
8.
Castro-Hermida JA García-Presedo I Almeida A González-Warleta M Correia Da Costa JM Mezo M 《The Science of the total environment》2011,409(13):2451-2459
The aim of the present study was to investigate the environmental dispersal of Cryptosporidium spp. and Giardia duodenalis in two distinct areas (coastal and inland) in Galicia (NW Spain). Faecal samples were collected from healthy asymptomatic domestic (cows and sheep) and wild animals (deer and wild boars) in the selected areas. In each of the selected areas, samples of untreated water (influent) and of treated water (final effluent) were collected from each of the 12 drinking water treatments plants (DWTPs) and 12 wastewater treatment plants (WTPs) under study. Analysis of a single sample from each of the 635 (coastal) and 851 (inland) domestic and wild animals selected at random revealed that the prevalences of cryptosporidiosis and giardiosis in coastal area were 9.2% and 15.9% respectively, and in inland area, 13.7% and 26.7% respectively. In the coastal area, Cryptosporidium spp. oocysts were detected in influent and effluent samples from 2/12 (16.6%) DWTPs and 8/12 (66.6%) WTPs, while G. duodenalis cysts were detected in influent and effluent samples from 3/12 (25.0%) DWTPs and 12/12 (100%) WTPs. The concentrations were notably higher in WTPs; the mean parasite concentrations in the final treated effluent were 10 oocysts per litre and 137.8 cysts per litre for Cryptosporidium and Giardia, respectively. The mean concentration of G. duodenalis cysts per litre was significantly higher (P < 0.05) than the mean concentration of Cryptosporidium spp. oocysts per litre in both the influent and the effluent samples from all the treatment plants. In the coastal area, C. parvum, C. hominis and G. duodenalis assemblages A (I and II) and E were most repeatedly detected. In the inland area, C. parvum, C. andersoni and G. duodenalis assemblages A (I and II), B and E were most frequently identified. 相似文献
9.
F. V. Antunes A. G. Chegini D. Camas L Correia 《Fatigue & Fracture of Engineering Materials & Structures》2015,38(8):983-996
The mean stress has a significant effect on crack propagation life and must be included in prediction models. However, there is no consensus in the fatigue community regarding the dominant mechanism explaining the mean stress effect. The concept of crack closure has been widely used and several empirical models can be found in literature. The stress ratio, R, is usually the main parameter of these models, but present numerical results showed a significant influence of Kmax. A new empirical model is therefore proposed here, dependent on Kmax and ΔK, with four empirical constants. The model also includes the effect of material's yield stress, and two additional parameters were defined to account for stress state and crack closure parameter. A comparison was made with Kujawski's and Glinka's parameters, for a wide range of loading conditions. ΔKeff lies between Kujawski's and Glinka's parameters, and some agreement is evident, although the concepts are quite different. The crack opening model was applied to literature results and was able to collapse da/dN–ΔK curves for different stress ratios to a single master curve. 相似文献
10.
Maarten Sijm Julianna Siciliano de Araújo Alba Ramos Llorca Dr. Kristina Orrling Lydia Stiny An Matheeussen Prof. Dr. Louis Maes Prof. Dr. Iwan J. P. de Esch Dr. Maria de Nazaré Correia Soeiro Dr. Geert Jan Sterk Prof. Dr. Rob Leurs 《ChemMedChem》2019,14(18):1662-1668
Chagas disease is becoming a worldwide problem; it is currently estimated that over six million people are infected. The two drugs in current use, benznidazole and nifurtimox, require long treatment regimens, show limited efficacy in the chronic phase of infection, and are known to cause adverse effects. Phenotypic screening of an in-house library led to the identification of 2,2′-methylenebis(5-(4-bromophenyl)-4,4-dimethyl-2,4-dihydro-3H-pyrazol-3-one), a phenyldihydropyrazolone dimer, which shows an in vitro pIC50 value of 5.4 against Trypanosoma cruzi. Initial optimization was done by varying substituents of the phenyl ring, after which attempts were made to replace the phenyl ring. Finally, the linker between the dimer units was varied, ultimately leading to 2,2′-methylenebis(5-(3-bromo-4-methoxyphenyl)-4,4-dimethyl-2,4-dihydro-3H-pyrazol-3-one (NPD-0228) as the most potent analogue. NPD-0228 has an in vitro pIC50 value of 6.4 against intracellular amastigotes of T. cruzi and no apparent toxicity against the human MRC-5 cell line and murine cardiac cells. 相似文献