全文获取类型
收费全文 | 3214篇 |
免费 | 226篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 16篇 |
综合类 | 2篇 |
化学工业 | 1213篇 |
金属工艺 | 26篇 |
机械仪表 | 82篇 |
建筑科学 | 107篇 |
矿业工程 | 1篇 |
能源动力 | 80篇 |
轻工业 | 992篇 |
水利工程 | 14篇 |
石油天然气 | 15篇 |
无线电 | 95篇 |
一般工业技术 | 393篇 |
冶金工业 | 70篇 |
原子能技术 | 4篇 |
自动化技术 | 333篇 |
出版年
2024年 | 10篇 |
2023年 | 49篇 |
2022年 | 233篇 |
2021年 | 255篇 |
2020年 | 121篇 |
2019年 | 121篇 |
2018年 | 134篇 |
2017年 | 145篇 |
2016年 | 133篇 |
2015年 | 108篇 |
2014年 | 176篇 |
2013年 | 261篇 |
2012年 | 249篇 |
2011年 | 242篇 |
2010年 | 154篇 |
2009年 | 169篇 |
2008年 | 162篇 |
2007年 | 159篇 |
2006年 | 94篇 |
2005年 | 92篇 |
2004年 | 69篇 |
2003年 | 57篇 |
2002年 | 43篇 |
2001年 | 29篇 |
2000年 | 28篇 |
1999年 | 20篇 |
1998年 | 23篇 |
1997年 | 23篇 |
1996年 | 22篇 |
1995年 | 12篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有3443条查询结果,搜索用时 16 毫秒
961.
Induction of crystallization influences the retention of volatile compounds in freeze-dried marolo pulp 总被引:1,自引:0,他引:1
Tânia Sulamytha Bezerra Cristina Guimarães Pereira Mônica Elisabeth Torres Prado Eduardo Valério de Barros Vilas Boas 《Drying Technology》2018,36(10):1250-1262
The effects of sucrose, maltodextrin, and ethanol as prefreezing treatments on the retention of volatile compounds in freeze-dried marolo pulp were evaluated. The volatile compounds were extracted using a solid-phase microextraction technique and investigated by gas chromatography combined with mass spectrometry. The transition temperatures, X-ray diffraction-derived microstructures, particle sizes, and scanning electron microscopy images were examined. The optimum inducer concentrations which produced typically amorphous structures were maltodextrin up to 60.0?g/L and lower ethanol and sucrose concentrations, which were optimized to achieve maximum retention of volatile substances compared with the original fruit pulp. 相似文献
962.
Alex Gomez-Gomez Paula Aguilera Klaus Langohr Gregori Casals Cristina Pavon Josep Marcos Jordi To-Figueras Oscar J. Pozo 《International journal of molecular sciences》2022,23(6)
Acute intermittent porphyria (AIP) is an inherited rare hepatic disorder due to mutations within the hydroxymethylbilane gene. AIP patients with active disease overproduce aminolevulinic acid (ALA) and porphobilinogen (PBG) in the liver which are exported inducing severe neurological attacks. Different hepatic metabolic abnormalities have been described to be associated with this condition. The goal of this research was to explore the metabolome of symptomatic AIP patients by state-of-the art liquid chromatography-tandem mass spectrometry (LC-MS/MS). A case versus control study including 18 symptomatic AIP patients and 33 healthy controls was performed. Plasmatic levels of 51 metabolites and 16 ratios belonging to four metabolic pathways were determined. The results showed that the AIP patients presented significant changes in the two main areas of the metabolome under study: (a) the tryptophan/kynurenine pathway with an increase of tryptophan in plasma together with increase of the kynurenine/tryptophan ratio; and (b) changes in the tricarboxylic acid cycle (TCA) including increase of succinic acid and decrease of the fumaric acid/succinic acid ratio. We performed a complementary in vitro study adding ALA to hepatocytes media that showed some of the effects on the TCA cycle were parallel to those observed in vivo. Our study confirms in plasma previous results obtained in urine showing that AIP patients present a moderate increase of the kynurenine/tryptophan ratio possibly associated with inflammation. In addition, it also reports changes in the mitochondrial TCA cycle that, despite requiring further research, could be associated with an energy misbalance due to sustained overproduction of heme-precursors in the liver. 相似文献
963.
Julin Santiago-Moreno Beln Pequeo Belen Martinez-Madrid Cristina Castao Paula Bveda Rosario Velzquez Adolfo Toledano-Díaz Manuel lvarez-Rodríguez Heriberto Rodríguez-Martínez 《International journal of molecular sciences》2022,23(6)
This work identified the presence of AQPs in frozen-thawed sperm of wild ruminants and assessed the influence of the interaction between photoperiod and thyroxine on AQP expression, and on testosterone secretion. Thyroxine and melatonin were administered to ibexes. In a second experiment, performed in mouflons, circulating thyroxine was reduced via treatment with propylthiouracil (PTU), and an artificial long day (LD) photoperiod established. In the ibexes, the melatonin treatment increased the blood plasma testosterone concentration, reduced the cryoresistance ratio (CR) for sperm viability and the presence of an intact acrosome, and increased the percentage of sperm with AQP7 in the acrosome and of AQP3 and AQP10 in the midpiece. In the mouflons, neither the PTU treatment, the LD, nor the combination of both affected the CR of any sperm variable. The percentage of sperm with AQP3 increased in the post-acrosome region but decreased in the tail in the LD+PTU group. The percentage of sperm with AQP10 in the principal piece and endpiece was lower in the PTU+LD group than in the control and LD groups. The influence of photoperiod/melatonin on AQP expression might be indirectly exerted through changes in the testosterone concentration, and thus ultimately affect sperm cryoresistance. 相似文献
964.
Filippo Fornasiero Cristina Scapin Maurizio Vitadello Paola Pizzo Luisa Gorza 《International journal of molecular sciences》2022,23(6)
The endoplasmic reticulum (ER) chaperone Grp94/gp96 appears to be involved in cytoprotection without being required for cell survival. This study compared the effects of Grp94 protein levels on Ca2+ homeostasis, antioxidant cytoprotection and protein–protein interactions between two widely studied cell lines, the myogenic C2C12 and the epithelial HeLa, and two breast cancer cell lines, MDA-MB-231 and HS578T. In myogenic cells, but not in HeLa, Grp94 overexpression exerted cytoprotection by reducing ER Ca2+ storage, due to an inhibitory effect on SERCA2. In C2C12 cells, but not in HeLa, Grp94 co-immunoprecipitated with non-client proteins, such as nNOS, SERCA2 and PMCA, which co-fractionated by sucrose gradient centrifugation in a distinct, medium density, ER vesicular compartment. Active nNOS was also required for Grp94-induced cytoprotection, since its inhibition by L-NNA disrupted the co-immunoprecipitation and co-fractionation of Grp94 with nNOS and SERCA2, and increased apoptosis. Comparably, only the breast cancer cell line MDA-MB-231, which showed Grp94 co-immunoprecipitation with nNOS, SERCA2 and PMCA, increased oxidant-induced apoptosis after nNOS inhibition or Grp94 silencing. These results identify the Grp94-driven multiprotein complex, including active nNOS as mechanistically involved in antioxidant cytoprotection by means of nNOS activity and improved Ca2+ homeostasis. 相似文献
965.
This paper presents an Application-specific Run-Time managEment (ARTE) framework to tackle the problem of managing computational resources in an application specific multi-core system. The ARTE framework run-time goal is to minimize applications’ response times while meeting the applications’ computational demands and fitting within the available power budget. 相似文献
966.
967.
Valerio Cristofori Donatella Caruso Gabriele Latini Mario Dell’Agli Corrado Cammilli Eddo Rugini Cristina Bignami Rosario Muleo 《European Food Research and Technology》2011,232(3):397-403
Pomegranate is getting an increasing attention for its health-promoting effects. Collection and characterization of plants of local sources has been performed, and five accessions have been propagated and cultivated in a collection field for extra situ investigations. Accessions differ for pomological traits and chemical composition. Three of them, MG1, MG2, and MG3, belong to typology with low-medium acidity and high sugar content, while the other two, Tordimonte A and B, belong to typology with high acidity. In the juice and in the peels’ extract of Tordimonte A accession a high level of punicalin has been found through chromatographic determinations, while the presence of punicalagin was found in the juice of accession MG1. The accessions MG1, MG2, and MG3 seem particularly suitable for direct commercialization of fruits due to the fruit traits and quality (sweet varieties), while Tordimonte A and B could be valuable for juice processing (sour varieties). 相似文献
968.
Melissa Watanabe Lúcia Rejane da Rosa Gama Madruga Cristina Keiko Yamaguchi Adriana Carvalho Pinto Vieira Roseli Jenoveva-Neto 《Water Resources Management》2014,28(11):3815-3828
Water is an essential element to life, and must be available to meet the basic needs of human beings. One of these needs is the production of food, emphasizing the relevance of agribusiness agents in the management of this natural resource. This study discusses how the management of water resources is being conducted by Committees of Watersheds in the State Rio Grande do Sul, focusing on decision making and in social learning. This is an exploratory study, supported by predominantly qualitative analysis. The results showed that the formation of the Committees of Watersheds in the State of Rio Grande do Sul depends on local decisions that are distinct in each region of the State. Evolution in the learning process of the members of the Committees occurs from the existence of conflicts. The conflicts emerge from issues concerning the use of water due to the multiple interests involved and provide discussions and solutions that lead to learning. Decisions taken in the Basin Committees are generally operating and relating to the quantity or quality of water. Social learning is promoted by actions of technical and relational nature offered by the exchange of knowledge and experience among stakeholders and other agents involved. 相似文献
969.
Laura Anfossi Claudio Baggiani Cristina Giovannoli Gianfranco Giraudi 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2013,30(6):800-807
This study aimed at developing sensitive competitive enzyme-linked immunosorbent assays (ELISAs) for the banned Sudan dyes using polyclonal antibodies. Three different formats were developed and characterized in terms of sensitivity, selectivity and rapidity. A competitive indirect ELISA was developed, which showed an IC50 of 3.8 µg l–1. Two competitive direct ELISAs were also developed, in which the antibody was added before or simultaneously with the other reagents; the first showed an IC50 of 8.3 µg l–1 and the latter showed an IC50 of 4.9 µg l–1. Nevertheless, considering dilution of extracts which is needed to offset matrix interference, the limits of detection of the three formats were substantially the same (10 µg kg–1). The antibodies in all three test formats were able to recognize Sudan I and partially Sudan II, III and IV; no cross-reactivity was observed with the five edible dyes. Twenty food samples, including chilli powder, paprika, ketchup, and egg, were extracted by a simple sample preparation and very limited dilution. Extracts were analyzed by the developed competitive direct ELISA with the simultaneous addition of reagents. A good correlation was observed (y = 1.19x–10.0, r 2 = 0.991, n = 20) when the data was compared with that obtained through a conventional HPLC method. 相似文献
970.
Karakecili AG Demirtas TT Satriano C Gümüsderelioglu M Marletta G 《Journal of Bioscience and Bioengineering》2007,104(1):69-77
In this study, chitosan membranes prepared by the solvent casting method were modified with the Arg-Gly-Asp-Ser (RGDS) sequence of fibronectin using the photochemical immobilization technique. The results obtained from attenuated total reflection-Fourier transform infrared spectra and X-ray photoelectron spectroscopy studies confirmed the successful immobilization of RGDS on chitosan membranes. The immobilized peptide concentration was determined by ninhydrin analysis on the order of 10(-7) mol/cm(2). In vitro cell culture studies were performed with L929 mouse fibroblasts to investigate the effect of biomodification on fibroblast cell behaviour in serum-free and 10% serum-containing media. The results obtained from cell culture studies pointed out the specific interactions between biosignal RGDS molecules and fibroblast cells. A triggered cell attachment and proliferation were observed on RGDS-modified chitosan membranes that were more distinguishable in serum-free medium. In addition, the photochemical immobilization technique was realized in the presence of a photomask that was used to immobilize the RGDS molecules in a defined micropattern. L929 mouse fibroblasts attached on the RGDS-micropatterned areas indicating integrin-mediated interactions. 相似文献