全文获取类型
收费全文 | 406篇 |
免费 | 16篇 |
专业分类
电工技术 | 8篇 |
综合类 | 1篇 |
化学工业 | 146篇 |
金属工艺 | 3篇 |
机械仪表 | 10篇 |
建筑科学 | 5篇 |
能源动力 | 8篇 |
轻工业 | 22篇 |
水利工程 | 5篇 |
无线电 | 47篇 |
一般工业技术 | 89篇 |
冶金工业 | 28篇 |
原子能技术 | 1篇 |
自动化技术 | 49篇 |
出版年
2023年 | 2篇 |
2022年 | 15篇 |
2021年 | 21篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 9篇 |
2017年 | 10篇 |
2016年 | 7篇 |
2015年 | 16篇 |
2014年 | 10篇 |
2013年 | 26篇 |
2012年 | 19篇 |
2011年 | 19篇 |
2010年 | 14篇 |
2009年 | 12篇 |
2008年 | 12篇 |
2007年 | 17篇 |
2006年 | 9篇 |
2005年 | 12篇 |
2004年 | 14篇 |
2003年 | 16篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 14篇 |
1997年 | 10篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1986年 | 3篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 7篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有422条查询结果,搜索用时 15 毫秒
81.
Eva Kiss Gertrud Forika Reka Mohacsi Zsuzsanna Nemeth Tibor Krenacs Magdolna Dank 《International journal of molecular sciences》2021,22(7)
Dietary methyl-donors play important roles in physiological processes catalyzed by B vitamins as coenzymes, and are used for complementary support in oncotherapy. Our hypothesis was that methyl-donors can not only assist in tolerating cancer treatment but may also directly interfere with tumor growth and proliferation. Therefore, we investigated the proposed cancer inhibitory effects of methyl-donors (in a mixture of L-methionine, choline chloride, folic acid, and vitamin B12) on MCF7 and T47D breast cancer as well as A549 and H1650 lung cancer cell lines. Indeed, methyl-donor treatment significantly reduced the proliferation in all cell lines, possibly through the downregulation of MAPK/ERK and AKT signaling. These were accompanied by the upregulation of the pro-apoptotic Bak and Bax, both in MCF7 and H1650 cells, at reduced anti-apoptotic Mcl-1 and Bcl-2 levels in MCF7 and H1650 cells, respectively. The treatment-induced downregulation of p-p53(Thr55) was likely to contribute to protecting the nuclear localization and apoptosis inducing functions of p53. The presented features are known to improve the sensitivity of cancer therapy. Therefore, these data support the hypothesis, i.e., that methyl-donors may promote apoptotic signaling by protecting p53 functions through downregulating both the MAPK/ERK and the AKT pathways both in breast and lung adenocarcinoma cell lines. Our results can emphasize the importance and benefits of the appropriate dietary supports in cancer treatments. However, further studies are required to confirm these effects without any adverse outcome in clinical settings. 相似文献
82.
Sylva Prerostova Petre I. Dobrev Vojtech Knirsch Jana Jarosova Alena Gaudinova Barbara Zupkova Ilja T. Pril Tibor Janda Betislav Brzobohatý Jan Skalk Radomira Vankova 《International journal of molecular sciences》2021,22(5)
Plant survival in temperate zones requires efficient cold acclimation, which is strongly affected by light and temperature signal crosstalk, which converge in modulation of hormonal responses. Cold under low light conditions affected Arabidopsis responses predominantly in apices, possibly because energy supplies were too limited for requirements of these meristematic tissues, despite a relatively high steady-state quantum yield. Comparing cold responses at optimal light intensity and low light, we found activation of similar defence mechanisms—apart from CBF1–3 and CRF3–4 pathways, also transient stimulation of cytokinin type-A response regulators, accompanied by fast transient increase of trans-zeatin in roots. Upregulated expression of components of strigolactone (and karrikin) signalling pathway indicated involvement of these phytohormones in cold responses. Impaired response of phyA, phyB, cry1 and cry2 mutants reflected participation of these photoreceptors in acquiring freezing tolerance (especially cryptochrome CRY1 at optimal light intensity and phytochrome PHYA at low light). Efficient cold acclimation at optimal light was associated with upregulation of trans-zeatin in leaves and roots, while at low light, cytokinin (except cis-zeatin) content remained diminished. Cold stresses induced elevation of jasmonic acid and salicylic acid (in roots). Low light at optimal conditions resulted in strong suppression of cytokinins, jasmonic and salicylic acid. 相似文献
83.
84.
85.
Catalin Croitoru Cosmin Spirchez Daniel Cristea Aurel Lunguleasa Mihai Alin Pop Tibor Bedo Ionut Claudiu Roata Mihai Alexandru Luca 《应用聚合物科学杂志》2018,135(22)
In this article, poly(vinyl chloride) (PVC) sandwich‐structured hybrid composites with amorphous calcium carbonate and wood‐filled cores were obtained by compression molding. It has been determined that wood addition up to a weight ratio of 33% reported to the total filler amount is beneficial in improving both the inter‐filler and filler‐matrix interfacial adhesion, which alongside with the promoting of the amorphous PVC matrix crystallization is responsible for an increase up to 34% in the flexural strength of the composites, compared to unfilled PVC. The hybrid filled composites present up to 35% lower friction coefficients and up to 20% higher Brinell hardness values than the composites filled with calcium carbonate alone. Subsequently, wood addition determines an increase in the oxidation onset temperature for PVC and an increase with up to 20% in the sound and thermal‐insulative properties of the composites, compared to unfilled PVC. The dominating dispersive part of the composites surface energy aids in improving the mass and dimensional stability of the assembly to both water and dilute hydrochloric acid aqueous solutions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46317. 相似文献
86.
Emad Najafidehaghani Ziyang Gan Antony George Tibor Lehnert Gia Quyet Ngo Christof Neumann Tobias Bucher Isabelle Staude David Kaiser Tobias Vogl Uwe Hübner Ute Kaiser Falk Eilenberger Andrey Turchanin 《Advanced functional materials》2021,31(27):2101086
Lateral heterostructures of dissimilar monolayer transition metal dichalcogenides provide great opportunities to build 1D in-plane p–n junctions for sub-nanometer thin low-power electronic, optoelectronic, optical, and sensing devices. Electronic and optoelectronic applications of such p–n junction devices fabricated using a scalable one-pot chemical vapor deposition process yielding MoSe2-WSe2 lateral heterostructures are reported here. The growth of the monolayer lateral heterostructures is achieved by in situ controlling the partial pressures of the oxide precursors by a two-step heating protocol. The grown lateral heterostructures are characterized structurally and optically using optical microscopy, Raman spectroscopy/microscopy, and photoluminescence spectroscopy/microscopy. High-resolution transmission electron microscopy further confirms the high-quality 1D boundary between MoSe2 and WSe2 in the lateral heterostructure. p–n junction devices are fabricated from these lateral heterostructures and their applicability as rectifiers, solar cells, self-powered photovoltaic photodetectors, ambipolar transistors, and electroluminescent light emitters are demonstrated. 相似文献
87.
Jzsef Szekeres Pter Borza Bla Csnyi Wolfram Graf Thomas Huber Patrick Leitner Djuradj Milosevi Momír Paunovi Claudia Pavelescu Tibor Ers 《河流研究与利用》2019,35(7):989-998
We comparatively examined the role of littoral and deep water sampling methods in assessing macroinvertebrate assemblages and in characterizing longitudinal changes in assemblage structure along >2,500‐km–long course of the Danube River, Europe. The effectiveness of detecting taxa corresponded well with an inshore–offshore gradient in sampling (i.e., distance from shore). Nevertheless, each method (i.e., littoral multihabitat sampling, kick and sweep sampling, and deep water dredging) contributed to some degree to overall taxa richness and species composition. Sampling in different depth zones characterized different assemblages, and consequently, inshore–offshore position was at least as important determinant of assemblage structure as longitudinal position of sampling sites in the river. Although we found significant congruency in the spatial variability of assemblages among the sampling methods, the relationships were only moderate. Our study on the large Danube River confirms studies from smaller rivers in other geographic regions that littoral monitoring provides higher taxa richness and more responsive changes to longitudinal gradients than deep water samples. Nevertheless, it also shows that sampling in different depth zones provides supplementary information on assemblage structure. Understanding changes in macroinvertebrate assemblages related to differences in sampling method is crucial to improve the bioassessment and environmental management of large rivers. 相似文献
88.
Tran Thanh Tung Md J. Nine Melinda Krebsz Tibor Pasinszki Campbell J. Coghlan Diana N. H. Tran Dusan Losic 《Advanced functional materials》2017,27(46)
Development of next‐generation sensor devices is gaining tremendous attention in both academia and industry because of their broad applications in manufacturing processes, food and environment control, medicine, disease diagnostics, security and defense, aerospace, and so forth. Current challenges include the development of low‐cost, ultrahigh, and user‐friendly sensors, which have high selectivity, fast response and recovery times, and small dimensions. The critical demands of these new sensors are typically associated with advanced nanoscale sensing materials. Among them, graphene and its derivatives have demonstrated the ideal properties to overcome these challenges and have merged as one of the most popular sensing platforms for diverse applications. A broad range of graphene assemblies with different architectures, morphologies, and scales (from nano‐, micro‐, to macrosize) have been explored in recent years for designing new high‐performing sensing devices. Herein, this study presents and discusses recent advances in synthesis strategies of assembled graphene‐based superstructures of 1D, 2D, and 3D macroscopic shapes in the forms of fibers, thin films, and foams/aerogels. The fabricated state‐of‐the‐art applications of these materials in gas and vapor, biomedical, piezoresistive strain and pressure, heavy metal ion, and temperature sensors are also systematically reviewed and discussed, and their sensing performance is compared. 相似文献
89.
Curing of wood-polyester combitions was studied by recording dielectric spectra as a function of temperature at fixed frequency at different stages of cure and as function of cure-time at fixed temperature. The measurements were preformed by a specially constructed continuously recording spectrometer equipped with linear temperature program. By measuring the shifts of the dielectric transition temperatures it was possible to follow changes of the molecular mobilities in the resin as crosslinking proceeded. By measuring the relative intensities of the dielectric absorption the change of the concentration of the polar groups as a function of cure time could be followed. The existence of a stepwise aftercuring waw revealed. 相似文献
90.
Summary By combining GPC fractionation with IR spectroscopy of ethylene-propylene copolymer (EP) samples, it has been shown that copolymer composition of EP's used in this study does not dep-end on molecular weight. Thus, contrary to earlier investigations by others, molecular weight distributions (MWD) and averages of EP's have been determined by using only experimental data such as GPC traces, universal calibration curve of GPC, and intrinsic viscosities. A comparative study has been carried out by using the MV method (called median value method) and the method of Ogawa and Inaba (OI method) for determination of MWD's and molecular weight averages of EP's. Application of the MV method results in lower molecular weight averages than the use of the equations proposed by Ogawa and Inaba for calculation of Mark-Houwing constants of EP's. However, polydispersities were found to be the same in both methods. The MV method also yields composition depending reliable pairs of Mark-Houwink constants, a and K, for EP's in 1,2,4-trichloro-benzene at 135 °C. 相似文献