全文获取类型
收费全文 | 2090篇 |
免费 | 93篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 20篇 |
综合类 | 11篇 |
化学工业 | 442篇 |
金属工艺 | 50篇 |
机械仪表 | 51篇 |
建筑科学 | 90篇 |
矿业工程 | 8篇 |
能源动力 | 57篇 |
轻工业 | 129篇 |
水利工程 | 4篇 |
石油天然气 | 5篇 |
无线电 | 140篇 |
一般工业技术 | 413篇 |
冶金工业 | 386篇 |
原子能技术 | 15篇 |
自动化技术 | 365篇 |
出版年
2024年 | 5篇 |
2023年 | 23篇 |
2022年 | 34篇 |
2021年 | 67篇 |
2020年 | 50篇 |
2019年 | 55篇 |
2018年 | 49篇 |
2017年 | 40篇 |
2016年 | 63篇 |
2015年 | 53篇 |
2014年 | 54篇 |
2013年 | 129篇 |
2012年 | 98篇 |
2011年 | 137篇 |
2010年 | 98篇 |
2009年 | 88篇 |
2008年 | 103篇 |
2007年 | 111篇 |
2006年 | 76篇 |
2005年 | 69篇 |
2004年 | 51篇 |
2003年 | 55篇 |
2002年 | 52篇 |
2001年 | 41篇 |
2000年 | 27篇 |
1999年 | 36篇 |
1998年 | 79篇 |
1997年 | 37篇 |
1996年 | 52篇 |
1995年 | 46篇 |
1994年 | 17篇 |
1993年 | 25篇 |
1992年 | 20篇 |
1991年 | 17篇 |
1990年 | 17篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 22篇 |
1986年 | 11篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1977年 | 9篇 |
1976年 | 23篇 |
1975年 | 5篇 |
1972年 | 4篇 |
1971年 | 7篇 |
排序方式: 共有2186条查询结果,搜索用时 6 毫秒
71.
Prabhakaran Thandapani Mangalaraja Ramalinga Viswanathan Marcus Vinícius-Araújo Andris F. Bakuzis Fanny Béron Arun Thirumurugan Juliano C. Denardin Jose A. Jiménez Ali Akbari-Fakhrabadi 《Journal of the American Ceramic Society》2020,103(9):5086-5097
The study demonstrates the performance of heating efficiency in single-phase and binary phase spinel ferrite nanosystems. Ferrimagnetic cobalt ferrite (CoFe2O4) (CFO) and superparamagnetic copper ferrite/copper oxide (CuFe2O4/CuO) (CuF) nanosystems of different particle sizes were synthesized through a microwave-assisted coprecipitation method. The heating behavior was observed in range of both field amplitudes (8-24 kA/m at 516 kHz) and frequencies (325-973 kHz at 12 kA/m). The heating efficiency was analyzed and compared by means of particle size, magnetization, effective anisotropy constant, and Néel relaxation mechanism. Indeed, the heating rate was maximized in larger ferrite particles with low effective anisotropy constant. Moreover, though the magnetization and effective anisotropy constant of single-phase CoFe2O4 nanoparticles were higher, the binary phase CuFe2O4/CuO nanosystems of similar crystallite size (28 nm) exhibited superior heating efficiency (4.21°C/s). For a field amplitude and frequency of 24 kA/m and 516 kHz, the heating rate of CuF and CFO ferrites with different crystallite sizes decreased in the order of 4.21 > 2.14 > 0.58 > 0.52°C/s for 29 nm > 25 nm > 12 nm > 15 nm, respectively. The results emphasize that binary phase ferrite nanoparticles are better thermoseeds than the single-phase ferrites for the magnetic hyperthermia application. 相似文献
72.
Marcus Conrad Christian A. Sldner Heinrich Sticht 《International journal of molecular sciences》2022,23(3)
The histamine H1 receptor (H1R) is a G protein-coupled receptor (GPCR) and represents a main target in the treatment of allergic reactions as well as inflammatory reactions and depressions. Although the overall effect of antagonists on H1 function has been extensively investigated, rather little is known about the potential modulatory effect of ions or sequence variants on antagonist binding. We investigated the dynamics of a phosphate ion present in the crystal structure and of a sodium ion, for which we determined the position in the allosteric pocket by metadynamics simulations. Both types of ions exhibit significant dynamics within their binding site; however, some key contacts remain stable over the simulation time, which might be exploited to develop more potent drugs targeting these sites. The dynamics of the ions is almost unaffected by the presence or absence of doxepin, as also reflected in their small effect (less than 1 kcal·mol−1) on doxepin binding affinity. We also examined the effect of four H1R sequence variants observed in the human population on doxepin binding. These variants cause a reduction in doxepin affinity of up to 2.5 kcal·mol−1, indicating that personalized medical treatments that take into account individual mutation patterns could increase precision in the dosage of GPCR-targeting drugs. 相似文献
73.
Busarakorn Mahayothee Patchimaporn Udomkun Marcus Nagle Methinee Haewsungcharoen Serm Janjai Joachim Mueller 《European Food Research and Technology》2009,229(2):329-337
The objective of this research was to study the effect of osmotic pretreatment with combined anti-browning agents (acid, glycerol
and/or trehalose) on the colour characteristics of dried litchi after drying and during 5 months of storage compared to samples
without pretreatment. The pretreated samples showed good inhibition of polyphenol oxidase activity when compared with the
control, while the total phenolic contents in the dried products were not reduced. The results demonstrated that water activity,
lightness difference, chroma, degree of browning (DB), and 5-hydroxymethylfurfural values of all pretreated samples increased,
while hue angle decreased with storage time. Samples pretreated with glycerol showed the best potential for browning retardation,
followed by glycerol combined with trehalose, and trehalose, respectively. In addition, the colour parameters were used to
calculate the luminescence values, representing the data in grey scale, which were correlated with a non-enzymatic browning
index. The results showed grey value could be adequately used to represent the DB of dried litchi with r
2 value of 0.92. 相似文献
74.
Stefan Wagner Marcus Moser Christoph Greubel Katrin Peeper Patrick Reichart Astrid Pundt Günther Dollinger 《International Journal of Hydrogen Energy》2013
Hydrogen absorption in thin metal films clamped to rigid substrates results in mechanical stress that changes the hydrogen's chemical potential by ΔμH(σ) = −1.124σ kJ/molH for σ measured in [GPa]. In this paper we show that local stress relaxation by the detachment of niobium hydrogen thin films from the substrate affects the chemical potential on the local scale: using coincident proton–proton scattering at a proton microprobe, the hydrogen concentration is determined with μm resolution, revealing that hydrogen is not homogenously distributed in the film. The local hydrogen solubility of the film changes with its local stress state, mapping the buckled film fraction. In niobium hydrogen thin films loaded up to nominal concentrations in the two-phase coexistence region, the clamped film fraction remains in the solid solution phase, while the buckles represent the hydride phase. These results are compared to a simple model taking the stress impact on the chemical potential into account. 相似文献
75.
Kyeong Yeol Oh Jin Hwan Lee Marcus J. Curtis-Long Jung Keun Cho Jun Young Kim Woo Song Lee Ki Hun Park 《Food chemistry》2010
The seeds of Psoralea corylifolia were extracted into five different polar solvents: chloroform, 50% ethanol in water, ethanol, methanol and water. All extracts were evaluated for glycosidase inhibitory activity. The chloroform extract (CE) showed the lowest IC50 values against α-glucosidase (82.9 μg/ml) and α-mannosidase (132 μg/ml). Chromatography of CE yielded nine phenolic compounds which were identified as isovabachalcone (1), 4′-O-methylbavachalcone (2), isobavachromene (3), corylifolin (4), bavachinin (5), psoralidin (6), neobavaisoflavone (7), corylifol A (8), and bakuchiol (9). All isolated compounds, apart from compound 5, possessed α-glucosidase inhibitory activities. Among them, compounds 6–8 exhibited potent inhibition with IC50s of 13.7, 27.7 and 11.3 μM, respectively. Furthermore, compounds 2 and 6 showed α-mannosidase inhibitory activity. Mechanistic analysis of their inhibition modes against α-glucosidase showed that compounds (6 and 7) were noncompetitive, whereas compound 8 was mixed. Furthermore, the most active glycosidase inhibitors (2, 6–8) were proven to be present in the native seed in high quantities by an HPLC chromatogram. 相似文献
76.
Peptide Bioconjugates of Electron‐Poor Metallocenes: Synthesis,Characterization, and Anti‐Proliferative Activity 下载免费PDF全文
Marcus Maschke Jens Grohmann Claudia Nierhaus Dr. Max Lieb Prof. Dr. Nils Metzler‐Nolte 《Chembiochem : a European journal of chemical biology》2015,16(9):1333-1342
We report the synthesis of metallocene compounds Cp2M with two different electron‐withdrawing substituents on both cyclopentadienyl rings (hexafluoroacetone (HFA) and chlorobenzoyl ( 1 – 5 ); HFA and COOH ( 6 and 7 ), M=Fe or Ru). The COOH‐containing derivatives were used to synthesize peptide bioconjugates with enkephalin ( 8 and 9 ) and neurotensin ( 10 and 11 ) as well as fluorescein‐labeled neurotensin ( 12 ). All the molecules were fully characterized, including X‐ray structures for 6 and 7 . The physicochemical properties (lipophilicity and electrochemistry) and cytotoxicity on MCF‐7, HT‐29, and PT‐45 cancer cells were evaluated for selected compounds. Electrochemical investigation by cyclic voltammetry revealed that all bis‐substituted metallocenes are up to 300 mV harder to oxidize compared to the monosubstituted 2‐ferrocenylhexafluoropropan‐2‐ol (FcHFA: Δ${E{{{\rm f}\hfill \atop 0\hfill}}}$ =214 mV; disubstituted derivatives: up to Δ${E{{{\rm f}\hfill \atop 0\hfill}}}$ =512 mV; both vs. FcH0/+). For the bis‐substituted compounds, log P determinations by RP‐HPLC showed increased lipophilicity in comparison to the monosubstituted FcHFA and RcHFA. Cellular uptake was investigated by fluorescence microcopy, and this revealed endosomal entrapment for 12 . 相似文献
77.
Produktschonende Betriebs‐ und Designparameter von Wärmeübertragern für temperaturempfindliche Prozessströme 下载免费PDF全文
To allow the calculation of product degradation rates as extension to the currently used thermotechnical design calculations for heat exchangers, a volume‐related, reaction‐kinetic approach was developed. Therefore, a model system was selected and the product protection design parameters were determined for a lab‐scale heat exchanger with the help of simulations. The validation was demonstrated in an experiment. Additionally, the product‐protecting operating parameters for the heat exchanger were calculated with a technically relevant set of compounds. 相似文献
78.
Rakel Lindström Henri Groult Sandrine Zanna Philippe Marcus 《Electrochimica acta》2006,51(23):5001-5011
In order to produce thin films of crystalline V2O5, vanadium metal was thermally oxidised at 500 °C under oxygen pressures between 250 and 1000 mbar for 1-5 min. The oxide films were characterised by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS). The lithium intercalation performance of the oxide films was investigated by cyclic voltammetry (CV), chronopotentiometry and electrochemical impedance spectroscopy (EIS). It was shown that the composition, the crystallinity and the related lithium intercalation properties of the thin oxide films were critically dependent on the oxidation conditions. The formation of crystalline V2O5 films was stimulated by higher oxygen pressure and longer oxidation time. Exposure for 5 min at 750 mbar O2 at 500 °C resulted in a surface oxide film composed of V2O5, and consisting of crystallites up to 200 nm in lateral size. The thickness of the layer was about 100 nm. This V2O5 oxide film was found to have good cycling performance in a potential window between 3.8 and 2.8 V, with a stable capacity of 117 ± 10 mAh/g at an applied current density of 3.4 μA/cm2. The diffusion coefficients corresponding to the two plateaus at 3.4 and 3.2 V were determined from the impedance measurements to (5.2 and 3.0) × 10−13 cm2 s−1, respectively. Beneath the V2O5 layer, lower oxides (mainly VO2) were found close to the metal. At lower oxygen pressure and shorter exposure times, the oxide films were less crystalline and the amount of V4+ increased in the surface oxide film, as revealed by XPS. At intermediate oxygen pressures and exposure times a mixture of crystalline V2O5 and V6O13 was found in the oxide film. 相似文献
79.
80.
Daniela Grimm Herbert Schulz Marcus Krüger Jos Luis Corts-Snchez Marcel Egli Armin Kraus Jayashree Sahana Thomas J. Corydon Ruth Hemmersbach Petra M. Wise Manfred Infanger Markus Wehland 《International journal of molecular sciences》2022,23(6)
Cancer is a disease exhibiting uncontrollable cell growth and spreading to other parts of the organism. It is a heavy, worldwide burden for mankind with high morbidity and mortality. Therefore, groundbreaking research and innovations are necessary. Research in space under microgravity (µg) conditions is a novel approach with the potential to fight cancer and develop future cancer therapies. Space travel is accompanied by adverse effects on our health, and there is a need to counteract these health problems. On the cellular level, studies have shown that real (r-) and simulated (s-) µg impact survival, apoptosis, proliferation, migration, and adhesion as well as the cytoskeleton, the extracellular matrix, focal adhesion, and growth factors in cancer cells. Moreover, the µg-environment induces in vitro 3D tumor models (multicellular spheroids and organoids) with a high potential for preclinical drug targeting, cancer drug development, and studying the processes of cancer progression and metastasis on a molecular level. This review focuses on the effects of r- and s-µg on different types of cells deriving from thyroid, breast, lung, skin, and prostate cancer, as well as tumors of the gastrointestinal tract. In addition, we summarize the current knowledge of the impact of µg on cancerous stem cells. The information demonstrates that µg has become an important new technology for increasing current knowledge of cancer biology. 相似文献