全文获取类型
收费全文 | 843篇 |
免费 | 49篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 3篇 |
综合类 | 1篇 |
化学工业 | 377篇 |
金属工艺 | 11篇 |
机械仪表 | 19篇 |
建筑科学 | 32篇 |
能源动力 | 24篇 |
轻工业 | 121篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 25篇 |
一般工业技术 | 167篇 |
冶金工业 | 23篇 |
原子能技术 | 5篇 |
自动化技术 | 78篇 |
出版年
2024年 | 5篇 |
2023年 | 18篇 |
2022年 | 118篇 |
2021年 | 75篇 |
2020年 | 36篇 |
2019年 | 40篇 |
2018年 | 21篇 |
2017年 | 37篇 |
2016年 | 27篇 |
2015年 | 18篇 |
2014年 | 34篇 |
2013年 | 54篇 |
2012年 | 46篇 |
2011年 | 64篇 |
2010年 | 36篇 |
2009年 | 42篇 |
2008年 | 44篇 |
2007年 | 29篇 |
2006年 | 44篇 |
2005年 | 12篇 |
2004年 | 20篇 |
2003年 | 17篇 |
2002年 | 18篇 |
2001年 | 9篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1963年 | 2篇 |
排序方式: 共有895条查询结果,搜索用时 15 毫秒
791.
Tatiana G. Fedulina Muza F. Kiryushina Sergey M. Shevchenko Andrey V. Pranovich 《木材化学与工艺学杂志》2017,37(4):241-250
The effects of alkali and polar aprotic solvent on the aromatic carbons signals in 13C NMR (Carbon-13 nuclear magnetic resonance) spectra of lignin model compounds and spruce milled wood lignin (MWL) were studied. It was found that in 1 M aqueous NaOH signal shifts of C-1 and C-4 carbon atoms in the aromatic ring were the most noticeable in lignin models with free phenolic hydroxyl groups, which are ionized under the conditions. A similar effect in the spectra of the studied model compounds was observed in 0.5 M aqueous NaOD-deuterated dimethyl sulfoxide (DMSO) mixture (DMSO: water ratio 3:7 v/v). The model data help explaining changes in the 13C NMR spectra of MWL and lignin in situ dissolved in spruce kraft black liquor caused by ionization. In the 13C NMR spectra of spruce black liquor the signals of phenolic and non-phenolic lignin units are clearly separated and do not overlap with the signals of the carbon atoms of carbohydrates and other aliphatic products of wood degradation. The data obtained are useful in understanding the important role of solvation and ionization processes leading to lignin solubilization. 相似文献
792.
Gregianini TS Porto DD Do Nascimento NC Fett JP Henriques AT Fett-Neto AG 《Journal of chemical ecology》2004,30(10):2023-2036
Brachycerine is a monoterpenoid indole alkaloid accumulated in Psychotria brachyceras plants (Rubiaceae). To better understand the accumulation patterns of this alkaloid, we investigated its content in different plant organs from field-grown trees, throughout the seasons, during seedling development, and in response to potential biotic factors regulating its biosynthesis. Quantification by RP-HPLC showed that aerial vegetative organs (green stems, young and old leaves) yielded similar amounts of brachycerine [0.1-0.2% dry weight (DW)]. Brachycerine was not detected in roots. In reproductive structures, the highest brachycerine amounts (0.3% DW) were found in inflorescences. Alkaloid concentration decreased in mature fruits (0.045% DW). The lowest concentration in reproductive organs was observed in quiescent seeds (0.004% DW). Apparently, brachycerine content dropped during radicle emission in germinating seeds. During seedling development, an increase in leaf content from 0.02 to 0.1% DW was observed between the stages of 2 and 14 leaves, respectively. Salicylic acid did not affect brachycerine content. A doubling of alkaloid content was observed in wounded plants, and a threefold induction occurred with jasmonic acid treatment, suggesting that brachycerine biosynthesis is regulated by jasmonate production. 相似文献
793.
Betina Royer Natali F. Cardoso Tatiana Calvete Roy E. Bruns 《Chemical Engineering Communications》2013,200(5):775-790
Factorial and central composite design experiments were performed to maximize the percentage removal of hydrolyzed reactive red 194 (HRR) from a simulated textile effluent by using Brazilian pine fruit wastes. Solution pH, initial dye concentration, contact time, and adsorbent mass levels were systematically varied for both untreated and acid-treated wastes. Biosorbent dosage of 9.0 g L?1, pH of 2.0, and at least 7–8 h contact time resulted in 98% dye removal for the acid-treated wastes and 88% for the untreated wastes. Adsorption isotherms were determined for both materials at the optimized conditions, and the equilibrium data was better fitted to the Sips isotherm model. 相似文献
794.
Ines Nitoi Tatiana Oncescu Petruta Oancea 《Journal of Industrial and Engineering Chemistry》2013,19(1):305-309
Because application of classical treatment methods cannot allow an easily Lindane (gamma 1α,2α,3β,4α,5α,6β-hexachlorocyclohexane) degradation, development of more powerful water treatment techniques, like advanced oxidation processes (AOPs), was necessary. The degradation of lindane (γ-HCH) has been studied using the photo-Fenton reaction. The degradation kinetics under irradiation was optimized in respect to H2O2 concentration and Fe2+ concentration at a constant lindane concentration. The degradation rate follows pseudo-first order kinetics with respect to lindane and organic clorine mineralization. Application of photo-Fenton system also assures total organic carbon removal with 95% efficiency at 2 h irradiation. The possible pathways of lindane photodegradation is also proposed. 相似文献
795.
Evgeny E. Beketov Elena V. Isaeva Nina D. Yakovleva Grigory A. Demyashkin Nadezhda V. Arguchinskaya Anastas A. Kisel Tatiana S. Lagoda Egor P. Malakhov Valentin I. Kharlov Egor O. Osidak Sergey P. Domogatsky Sergey A. Ivanov Petr V. Shegay Andrey D. Kaprin 《International journal of molecular sciences》2021,22(21)
The study was aimed at the applicability of a bioink based on 4% collagen and chondrocytes for de novo cartilage formation. Extrusion-based bioprinting was used for the biofabrication. The printing parameters were tuned to obtain stable material flow. In vivo data proved the ability of the tested bioink to form a cartilage within five to six weeks after the subcutaneous scaffold implantation. Certain areas of cartilage formation were detected as early as in one week. The resulting cartilage tissue had a distinctive structure with groups of isogenic cells as well as a high content of glycosaminoglycans and type II collagen. 相似文献
796.
Tommaso Montecchi Enxhi Shaba Domiziana De Tommaso Fabrizio Di Giuseppe Stefania Angelucci Luca Bini Claudia Landi Cosima Tatiana Baldari Cristina Ulivieri 《International journal of molecular sciences》2021,22(15)
Reactive astrocytes are a hallmark of neurodegenerative disease including multiple sclerosis. It is widely accepted that astrocytes may adopt alternative phenotypes depending on a combination of environmental cues and intrinsic features in a highly plastic and heterogeneous manner. However, we still lack a full understanding of signals and associated signaling pathways driving astrocyte reaction and of the mechanisms by which they drive disease. We have previously shown in the experimental autoimmune encephalomyelitis mouse model that deficiency of the molecular adaptor Rai reduces disease severity and demyelination. Moreover, using primary mouse astrocytes, we showed that Rai contributes to the generation of a pro-inflammatory central nervous system (CNS) microenvironment through the production of nitric oxide and IL-6 and by impairing CD39 activity in response to soluble factors released by encephalitogenic T cells. Here, we investigated the impact of Rai expression on astrocyte function both under basal conditions and in response to IL-17 treatment using a proteomic approach. We found that astrocytes and astrocyte-derived extracellular vesicles contain a set of proteins, to which Rai contributes, that are involved in the regulation of oligodendrocyte differentiation and myelination, nitrogen metabolism, and oxidative stress. The HIF-1α pathway and cellular energetic metabolism were the most statistically relevant molecular pathways and were related to ENOA and HSP70 dysregulation. 相似文献
797.
798.
Vladimir Sukhorukov Dmitry Voronkov Tatiana Baranich Natalia Mudzhiri Alina Magnaeva Sergey Illarioshkin 《International journal of molecular sciences》2021,22(19)
Aging is associated with a decline in cognitive function, which can partly be explained by the accumulation of damage to the brain cells over time. Neurons and glia undergo morphological and ultrastructure changes during aging. Over the past several years, it has become evident that at the cellular level, various hallmarks of an aging brain are closely related to mitophagy. The importance of mitochondria quality and quantity control through mitophagy is highlighted by the contribution that defects in mitochondria–autophagy crosstalk make to aging and age-related diseases. In this review, we analyze some of the more recent findings regarding the study of brain aging and neurodegeneration in the context of mitophagy. We discuss the data on the dynamics of selective autophagy in neurons and glial cells during aging and in the course of neurodegeneration, focusing on three mechanisms of mitophagy: non-receptor-mediated mitophagy, receptor-mediated mitophagy, and transcellular mitophagy. We review the role of mitophagy in neuronal/glial homeostasis and in the molecular pathogenesis of neurodegenerative disorders, such as Parkinson’s disease, Alzheimer’s disease, and other disorders. Common mechanisms of aging and neurodegeneration that are related to different mitophagy pathways provide a number of promising targets for potential therapeutic agents. 相似文献
799.
Marina I. Nikolaeva Tatiana B. Mikenas Mikhail A. Matsko Ludmila G. Echevskaya Vladimir A. Zakharov 《应用聚合物科学杂志》2010,115(4):2432-2439
Experimental data on the molecular weight distribution (MWD) of polyethylene (PE) produced over a broad number of Ziegler‐Natta catalysts differing in composition and preparation procedure are presented. These catalysts include nonsupported TiCl3 catalyst, four types of supported titanium‐magnesium catalysts (TMC) differing in the content of titanium and the presence of various modifiers in the composition of the support, and a supported catalyst containing VCl4 as an active component instead of TiCl4. The studied catalysts produce PE with different molecular weights within a broad range of polydispersity (Mw/Mn = 2.8–16) under the same polymerization conditions. The heterogeneity of active sites of these catalysts was studied by deconvolution of experimental MWD curves into Flory components assuming a correlation between the number of Flory components and the number of active site types. Five Flory components were found for PE produced over nonsupported TiCl3 catalysts (Mw/Mn = 6.8), and three–four Flory components were found for PE produced over TMC of different composition. A minimal number of Flory components (three) was found for PE samples (Mw/Mn values from 2.8 to 3.3) produced over TMC with a very low titanium content (0.07 wt %) and TMC modified with dibutylphtalate. It was shown that five Flory components are sufficient to fit the experimental MWD curve for bimodal PE (Mw/Mn = 16) produced over VMC. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
800.
Honglu Zhang Dr. Ju He Dr. Tatiana G. Kutateladze Prof. Dr. Takahiro Sakai Dr. Takehiko Sasaki Prof. Dr. Nicolas Markadieu Dr. Christophe Erneux Prof. Dr. Glenn D. Prestwich Prof. Dr. 《Chembiochem : a European journal of chemical biology》2010,11(3):388-395
Metabolically stabilized analogues of PtdIns(3,4,5)P3 have shown long‐lived agonist activity for cellular events and selective inhibition of lipid phosphatase activity. We describe an efficient asymmetric synthesis of two 5‐phosphatase‐resistant analogues of PtdIns(3,4,5)P3, the 5‐methylene phosphonate (MP) and 5‐phosphorothioate (PT). Furthermore, we illustrate the biochemical and biological activities of five stabilized PtdIns(3,4,5)P3 analogues in four contexts. First, the relative binding affinities of the 3‐MP, 3‐PT, 5‐MP, 5‐PT, and 3,4,5‐PT3 analogues to the Grp1 PH domain are shown, as determined by NMR spectroscopy. Second, the enzymology of the five analogues is explored, showing the relative efficiency of inhibition of SHIP1, SHIP2, and phosphatase and tensin homologue deleted on chromosome 10 (PTEN), as well as the greatly reduced ability of these phosphatases to process these analogues as substrates as compared to PtdIns(3,4,5)P3. Third, exogenously delivered analogues severely impair complement factor C5a‐mediated polarization and migration of murine neutrophils. Finally, the new analogues show long‐lived agonist activity in mimicking insulin action in sodium transport in A6 cells. 相似文献