全文获取类型
收费全文 | 3363篇 |
免费 | 452篇 |
国内免费 | 256篇 |
专业分类
电工技术 | 131篇 |
综合类 | 357篇 |
化学工业 | 481篇 |
金属工艺 | 179篇 |
机械仪表 | 113篇 |
建筑科学 | 265篇 |
矿业工程 | 214篇 |
能源动力 | 133篇 |
轻工业 | 168篇 |
水利工程 | 112篇 |
石油天然气 | 18篇 |
武器工业 | 12篇 |
无线电 | 686篇 |
一般工业技术 | 449篇 |
冶金工业 | 143篇 |
原子能技术 | 11篇 |
自动化技术 | 599篇 |
出版年
2024年 | 12篇 |
2023年 | 62篇 |
2022年 | 177篇 |
2021年 | 171篇 |
2020年 | 134篇 |
2019年 | 124篇 |
2018年 | 95篇 |
2017年 | 120篇 |
2016年 | 151篇 |
2015年 | 148篇 |
2014年 | 200篇 |
2013年 | 225篇 |
2012年 | 250篇 |
2011年 | 240篇 |
2010年 | 168篇 |
2009年 | 182篇 |
2008年 | 192篇 |
2007年 | 198篇 |
2006年 | 176篇 |
2005年 | 171篇 |
2004年 | 132篇 |
2003年 | 133篇 |
2002年 | 103篇 |
2001年 | 98篇 |
2000年 | 74篇 |
1999年 | 52篇 |
1998年 | 53篇 |
1997年 | 36篇 |
1996年 | 33篇 |
1995年 | 36篇 |
1994年 | 27篇 |
1993年 | 8篇 |
1992年 | 15篇 |
1991年 | 10篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 5篇 |
1973年 | 1篇 |
1965年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有4071条查询结果,搜索用时 15 毫秒
31.
Sanja Ramljak Matthias Schmitz Cendrine Repond Inga Zerr Luc Pellerin 《International journal of molecular sciences》2021,22(4)
The effect of a cellular prion protein (PrPc) deficiency on neuroenergetics was primarily analyzed via surveying the expression of genes specifically involved in lactate/pyruvate metabolism, such as monocarboxylate transporters (MCT1, MCT2, MCT4). The aim of the present study was to elucidate a potential involvement of PrPc in the regulation of energy metabolism in different brain regions. By using quantitative real-time polymerase chain reaction (qRT-PCR), we observed a marked reduction in MCT1 mRNA expression in the cortex of symptomatic Zürich I Prnp−/− mice, as compared to their wild-type (WT) counterparts. MCT1 downregulation in the cortex was accompanied with significantly decreased expression of the MCT1 functional interplayer, the Na+/K+ ATPase α2 subunit. Conversely, the MCT1 mRNA level was significantly raised in the cerebellum of Prnp−/− vs. WT control group, without a substantial change in the Na+/K+ ATPase α2 subunit expression. To validate the observed mRNA findings, we confirmed the observed change in MCT1 mRNA expression level in the cortex at the protein level. MCT4, highly expressed in tissues that rely on glycolysis as an energy source, exhibited a significant reduction in the hippocampus of Prnp−/− vs. WT mice. The present study demonstrates that a lack of PrPc leads to altered MCT1 and MCT4 mRNA/protein expression in different brain regions of Prnp−/− vs. WT mice. Our findings provide evidence that PrPc might affect the monocarboxylate intercellular transport, which needs to be confirmed in further studies. 相似文献
32.
Ahmad Hassan Chaudhry Shafa Nayab Syed Bilal Hussain Muqarrab Ali Zhiyong Pan 《International journal of molecular sciences》2021,22(4)
The productivity of agricultural produce is fairly dependent on the availability of nutrients and efficient use. Magnesium (Mg2+) is an essential macronutrient of living cells and is the second most prevalent free divalent cation in plants. Mg2+ plays a role in several physiological processes that support plant growth and development. However, it has been largely forgotten in fertilization management strategies to increase crop production, which leads to severe reductions in plant growth and yield. In this review, we discuss how the Mg2+ shortage induces several responses in plants at different levels: morphological, physiological, biochemical and molecular. Additionally, the Mg2+ uptake and transport mechanisms in different cellular organelles and the role of Mg2+ transporters in regulating Mg2+ homeostasis are also discussed. Overall, in this review, we critically summarize the available information about the responses of Mg deficiency on plant growth and development, which would facilitate plant scientists to create Mg2+-deficiency-resilient crops through agronomic and genetic biofortification. 相似文献
33.
Bianca Stoean Dumitrita Rugina Monica Focsan Ana-Maria Craciun MÎdÎlina Nistor Tamas Lovasz Alexandru Turza Ioan-Dan Porumb Emese Gl Castelia Cristea Luminita Silaghi-Dumitrescu Simion Astilean Luiza Ioana Gaina 《International journal of molecular sciences》2021,22(6)
We report here the synthesis and structural characterization of novel cationic (phenothiazinyl)vinyl-pyridinium (PVP) dyes, together with optical (absorption/emission) properties and their potential applicability as fluorescent labels. Convective heating, ultrasound irradiation and mechanochemical synthesis were considered as alternative synthetic methodologies proficient for overcoming drawbacks such as long reaction time, nonsatisfactory yields or solvent requirements in the synthesis of novel dye (E)-1-(3-chloropropyl)-4-(2-(10-methyl-10H-phenothiazin-3-yl)vinyl)pyridin-1-ium bromide 3d and its N-alkyl-2-methylpyridinium precursor 1c. The trans geometry of the newly synthesized (E)-4-(2-(7-bromo-10-ethyl-10H-phenothiazin-3-yl)vinyl)-1-methylpyridin-1-ium iodide 3b and (E)-1-methyl-4-(2-(10-methyl-10H-phenothiazin-3-yl)vinyl)pyridin-1-ium tetrafluoroborate 3a′ was confirmed by single crystal X-ray diffraction. A negative solvatochromism of the dyes in polar solvents was highlighted by UV-Vis spectroscopy and explanatory insights were supported by molecular modeling which suggested a better stabilization of the lowest unoccupied molecular orbitals (LUMO). The photostability of the dye 3b was investigated by irradiation at 365 nm in different solvents, while the steady-state and time-resolved fluorescence properties of dye 3b and 3a′ in solid state were evaluated under one-photon excitation at 485 nm. The in vitro cytotoxicity of the new PVP dyes on B16-F10 melanoma cells was evaluated by WST-1 assay, while their intracellular localization was assessed by epi-fluorescence conventional microscopy imaging as well as one- and two-photon excited confocal fluorescence lifetime imaging microscopy (FLIM). PVP dyes displayed low cytotoxicity, good internalization inside melanoma cells and intense fluorescence emission inside the B16-F10 murine melanoma cells, making them suitable staining agents for imaging applications. 相似文献
34.
Oleksandr Gryshkov Vitalii Mutsenko Dmytro Tarusin Diaa Khayyat Ortwin Naujok Ekaterina Riabchenko Yuliia Nemirovska Arseny Danilov Alexander Y. Petrenko Birgit Glasmacher 《International journal of molecular sciences》2021,22(6)
Alginate as a versatile naturally occurring biomaterial has found widespread use in the biomedical field due to its unique features such as biocompatibility and biodegradability. The ability of its semipermeable hydrogels to provide a favourable microenvironment for clinically relevant cells made alginate encapsulation a leading technology for immunoisolation, 3D culture, cryopreservation as well as cell and drug delivery. The aim of this work is the evaluation of structural properties and swelling behaviour of the core-shell capsules for the encapsulation of multipotent stromal cells (MSCs), their 3D culture and cryopreservation using slow freezing. The cells were encapsulated in core-shell capsules using coaxial electrospraying, cultured for 35 days and cryopreserved. Cell viability, metabolic activity and cell–cell interactions were analysed. Cryopreservation of MSCs-laden core-shell capsules was performed according to parameters pre-selected on cell-free capsules. The results suggest that core-shell capsules produced from the low viscosity high-G alginate are superior to high-M ones in terms of stability during in vitro culture, as well as to solid beads in terms of promoting formation of viable self-assembled cellular structures and maintenance of MSCs functionality on a long-term basis. The application of 0.3 M sucrose demonstrated a beneficial effect on the integrity of capsules and viability of formed 3D cell assemblies, as compared to 10% dimethyl sulfoxide (DMSO) alone. The proposed workflow from the preparation of core-shell capsules with self-assembled cellular structures to the cryopreservation appears to be a promising strategy for their off-the-shelf availability. 相似文献
35.
为了研究海洋平台人员疏散过程,定量评估疏散方案的合理性,基于元胞自动机模型开发适用于海洋平台人员逃生疏散的仿真系统,提出在离散模型中精确考虑多种人员速度的方法. 使用真实海洋平台疏散实验数据校核模型参数,并对比商业软件maritimeEXODUS的计算结果,验证仿真系统的可行性. 从疏散时间和出口使用效率对无烟和有烟场景下的人员疏散结果进行对比和量化分析,并提出优化方案. 结果表明:有烟环境不仅折减人员移动速度,延长疏散时间,更会影响人员的路径选择,导致疏散不平衡. 相似文献
36.
37.
38.
一种基于全IP蜂窝网络的实时业务传输机制* 总被引:1,自引:0,他引:1
针对无线蜂窝网络和Internet的业务特点,分析了在信道带宽有限、传输误码率高的无线网络中传输基于IP的实时业务所面临的问题.针对下一代蜂窝网络中基于IP技术实现多媒体业务要求,从无线网络上实际传送的码流角度,结合ROHC机制提出一种在信道传输速率不变的条件下,提高码流传输效率的方法,并且探究了空中链路的全IP机制.从采样编码后输出的净码流和经过封装后的码流两个角度来分析,提出了高效的针对全IP的蜂窝网络的实时交互式语音业务的新方案. 相似文献
39.
Rocío Mato-Basalo Miriam Morente-Lpez Onno J Arntz Fons A. J. van de Loo Juan Fafin-Labora María C. Arufe 《International journal of molecular sciences》2021,22(7)
Mesenchymal stem cells have an important potential in the treatment of age-related diseases. In the last years, small extracellular vesicles derived from these stem cells have been proposed as cell-free therapies. Cellular senescence and proinflammatory activation are involved in the loss of therapeutic capacity and in the phenomenon called inflamm-aging. The regulators of these two biological processes in mesenchymal stem cells are not well-known. In this study, we found that p65 is activated during cellular senescence and inflammatory activation in human umbilical cord-derived mesenchymal stem cell. To demonstrate the central role of p65 in these two processes, we used small-molecular inhibitors of p65, such as JSH-23, MG-132 and curcumin. We found that the inhibition of p65 prevents the cellular senescence phenotype in human umbilical cord-derived mesenchymal stem cells. Besides, p65 inhibition produced the inactivation of proinflammatory molecules as components of a senescence-associated secretory phenotype (SASP) (interleukin-6 and interleukin-8 (IL-6 and IL-8)). Additionally, we found that the inhibition of p65 prevents the transmission of paracrine senescence between mesenchymal stem cells and the proinflammatory message through small extracellular vesicles. Our work highlights the important role of p65 and its inhibition to restore the loss of functionality of small extracellular vesicles from senescent mesenchymal stem cells and their inflamm-aging signature. 相似文献
40.
Laia Lidn Laura Lla-Hierro Mario Nuvolone Adriano Aguzzi Jesús vila Isidro Ferrer Jos Antonio del Río Rosalina Gavín 《International journal of molecular sciences》2021,22(10)
Tau protein is largely responsible for tauopathies, including Alzheimer’s disease (AD), where it accumulates in the brain as insoluble aggregates. Tau mRNA is regulated by alternative splicing, and inclusion or exclusion of exon 10 gives rise to the 3R and 4R isoforms respectively, whose balance is physiologically regulated. In this sense, one of the several factors that regulate alternative splicing of tau is GSK3β, whose activity is inhibited by the cellular prion protein (PrPC), which has different physiological functions in neuroprotection and neuronal differentiation. Moreover, a relationship between PrPC and tau expression levels has been reported during AD evolution. For this reason, in this study we aimed to analyze the role of PrPC and the implication of GSK3β in the regulation of tau exon 10 alternative splicing. We used AD human samples and mouse models of PrPC ablation and tau overexpression. In addition, we used primary neuronal cultures to develop functional studies. Our results revealed a paralleled association between PrPC expression and tau 4R isoforms in all models analyzed. In this sense, reduction or ablation of PrPC levels induces an increase in tau 3R/4R balance. More relevantly, our data points to GSK3β activity downstream from PrPC in this phenomenon. Our results indicate that PrPC plays a role in tau exon 10 inclusion through the inhibitory capacity of GSK3β. 相似文献