全文获取类型
收费全文 | 27402篇 |
免费 | 700篇 |
国内免费 | 33篇 |
专业分类
电工技术 | 340篇 |
综合类 | 14篇 |
化学工业 | 6068篇 |
金属工艺 | 529篇 |
机械仪表 | 474篇 |
建筑科学 | 1172篇 |
矿业工程 | 334篇 |
能源动力 | 660篇 |
轻工业 | 1797篇 |
水利工程 | 226篇 |
石油天然气 | 245篇 |
无线电 | 1754篇 |
一般工业技术 | 4188篇 |
冶金工业 | 6297篇 |
原子能技术 | 268篇 |
自动化技术 | 3769篇 |
出版年
2022年 | 249篇 |
2021年 | 415篇 |
2020年 | 271篇 |
2019年 | 351篇 |
2018年 | 434篇 |
2017年 | 377篇 |
2016年 | 488篇 |
2015年 | 396篇 |
2014年 | 621篇 |
2013年 | 1692篇 |
2012年 | 956篇 |
2011年 | 1220篇 |
2010年 | 934篇 |
2009年 | 983篇 |
2008年 | 1164篇 |
2007年 | 1087篇 |
2006年 | 995篇 |
2005年 | 896篇 |
2004年 | 760篇 |
2003年 | 730篇 |
2002年 | 719篇 |
2001年 | 503篇 |
2000年 | 404篇 |
1999年 | 462篇 |
1998年 | 483篇 |
1997年 | 461篇 |
1996年 | 500篇 |
1995年 | 462篇 |
1994年 | 472篇 |
1993年 | 447篇 |
1992年 | 433篇 |
1991年 | 277篇 |
1990年 | 417篇 |
1989年 | 396篇 |
1988年 | 348篇 |
1987年 | 412篇 |
1986年 | 356篇 |
1985年 | 448篇 |
1984年 | 468篇 |
1983年 | 406篇 |
1982年 | 384篇 |
1981年 | 310篇 |
1980年 | 310篇 |
1979年 | 365篇 |
1978年 | 305篇 |
1977年 | 242篇 |
1976年 | 223篇 |
1975年 | 250篇 |
1974年 | 222篇 |
1973年 | 226篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Production of aromatics by catalytic fast pyrolysis of cellulose in a bubbling fluidized bed reactor 下载免费PDF全文
Pranav U. Karanjkar Robert J. Coolman George W. Huber Michael T. Blatnik Saba Almalkie Stephen M. de Bruyn Kops Triantafillos J. Mountziaris William C. Conner 《American Institute of Chemical Engineers》2014,60(4):1320-1335
Catalytic fast pyrolysis of cellulose was studied at 500°C using a ZSM‐5 catalyst in a bubbling fluidized bed reactor constructed from a 4.92‐cm ID pipe. Inert gas was fed from below through the distributor plate and from above through a vertical feed tube along with cellulose. Flowing 34% of the total fluidization gas through the feed tube led to the optimal mixing of the pyrolysis vapors into the catalyst bed, which experimentally corresponded to 29.5% carbon aromatic yield. Aromatic yield reached a maximum of 31.6% carbon with increasing gas residence time by changing the catalyst bed height. Increasing the hole‐spacing in the distributor plate was shown to have negligible effect on average bubble diameter and hence did not change the product distribution. Aromatic yields of up to 39.5% carbon were obtained when all studied parameters were optimized. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1320–1335, 2014 相似文献
992.
Jesus Palomino Oviedo Robert Metz John Schulz Ralf‐Peter Tressel Frank Pudel 《化学,工程师,技术》2014,86(8):1249-1259
Protein samples of rapeseed were prepared with different compositions as protein isolate, protein concentrate and acetylated protein concentrate. They showed functional properties which are consolidated in the coating. The manufactured protein samples were tested in a pilot‐scale paperboard coating plant. The results indicated that the use of rapeseed proteins in the coating preparation is technically feasible and that the color and roughness of the coated paperboard show no negative effect on the quality. Industry printing experiments with this coated paperboard achieved the standard quality. 相似文献
993.
One Question,Multiple Answers: Biochemical and Biophysical Screening Methods Retrieve Deviating Fragment Hit Lists 下载免费PDF全文
Dr. Johannes Schiebel Nedyalka Radeva Dr. Helene Köster Dr. Alexander Metz Timo Krotzky Dr. Maren Kuhnert Prof. Wibke E. Diederich Prof. Andreas Heine Dr. Lars Neumann Dr. Cedric Atmanene Dominique Roecklin Dr. Valérie Vivat‐Hannah Dr. Jean‐Paul Renaud Dr. Robert Meinecke Dr. Nina Schlinck Dr. Astrid Sitte Franziska Popp Dr. Markus Zeeb Prof. Gerhard Klebe 《ChemMedChem》2015,10(9):1511-1521
Fragment‐based lead discovery is gaining momentum in drug development. Typically, a hierarchical cascade of several screening techniques is consulted to identify fragment hits which are then analyzed by crystallography. Because crystal structures with bound fragments are essential for the subsequent hit‐to‐lead‐to‐drug optimization, the screening process should distinguish reliably between binders and non‐binders. We therefore investigated whether different screening methods would reveal similar collections of putative binders. First we used a biochemical assay to identify fragments that bind to endothiapepsin, a surrogate for disease‐relevant aspartic proteases. In a comprehensive screening approach, we then evaluated our 361‐entry library by using a reporter‐displacement assay, saturation‐transfer difference NMR, native mass spectrometry, thermophoresis, and a thermal shift assay. While the combined results of these screening methods retrieve 10 of the 11 crystal structures originally predicted by the biochemical assay, the mutual overlap of individual hit lists is surprisingly low, highlighting that each technique operates on different biophysical principles and conditions. 相似文献
994.
Synthetic and Biological Studies of Sesquiterpene Polygodial: Activity of 9‐Epipolygodial against Drug‐Resistant Cancer Cells 下载免费PDF全文
Dr. Ramesh Dasari Annelise De Carvalho Derek C. Medellin Kelsey N. Middleton Dr. Frédéric Hague Marie N. M. Volmar Prof. Liliya V. Frolova Dr. Mateus F. Rossato Jorge J. De La Chapa Nicholas F. Dybdal‐Hargreaves Akshita Pillai Prof. Véronique Mathieu Prof. Snezna Rogelj Prof. Cara B. Gonzales Prof. João B. Calixto Prof. Antonio Evidente Dr. Mathieu Gautier Dr. Gnanasekar Munirathinam Prof. Rainer Glass Prof. Patricia Burth Dr. Stephen C. Pelly Prof. Willem A. L. van Otterlo Prof. Robert Kiss Prof. Alexander Kornienko 《ChemMedChem》2015,10(12):2014-2026
Polygodial, a terpenoid dialdehyde isolated from Polygonum hydropiper L., is a known agonist of the transient receptor potential vanilloid 1 (TRPV1). In this investigation a series of polygodial analogues were prepared and investigated for TRPV1‐agonist and anticancer activities. These experiments led to the identification of 9‐epipolygodial, which has antiproliferative potency significantly exceeding that of polygodial. 9‐Epipolygodial was found to maintain potency against apoptosis‐resistant cancer cells as well as those displaying the multidrug‐resistant (MDR) phenotype. In addition, the chemical feasibility for the previously proposed mechanism of action of polygodial, involving the formation of a Paal–Knorr pyrrole with a lysine residue on the target protein, was demonstrated by the synthesis of a stable polygodial pyrrole derivative. These studies reveal rich chemical and biological properties associated with polygodial and its direct derivatives. These compounds should inspire further work in this area aimed at the development of new pharmacological agents, or the exploration of novel mechanisms of covalent modification of biological molecules with natural products. 相似文献
995.
Robert S. Janesheski Lori J. Groven Steven F. Son 《Propellants, Explosives, Pyrotechnics》2014,39(4):609-616
Typically characterizing home made explosives (HMEs) requires many large scale experiments, which is prohibitive given the large number of materials in use. A small scale experiment was developed to characterize HMEs such as ammonium nitrate‐fuel oil mixtures. A microwave interferometer is applied to small scale confined transient experiments, yielding time resolved characterization of a failing detonation that is initiated with an ideal explosive booster charge. Experiments were performed with ammonium nitrate and two fuel compositions (diesel fuel and mineral oil). It was observed that the failure dynamics were influenced by factors such as the chemical composition, confiner thickness, and applied shock wave strength. Thin steel walled confiners with 0.71 mm wall thickness experienced detonation failure and decoupling of the shock wave from the reaction zone. Confiners with a wall thickness of 34.9 mm showed a decrease in propagation speed and a steady reactive wave was achieved. Varying the applied shock strength by using an attenuator showed corresponding changes in the initial overdriven reactive wave velocity in the HMEs. The distance to detonation failure was also shown to depend on the attenuator length when thin wall confinement was used. This experimental method is shown to be repeatable and can be performed with little required material (about 2 g). The data obtained could be useful to model development and validation, as well as quantifying detonability of materials. 相似文献
996.
997.
Solubility information for CO2 in different ionic liquids, ILs, in part can potentially be used to select a specific IL for the separation of CO2 from hydrocarbon fluids. Unfortunately, not all CO2–IL systems have been experimentally described at similar temperatures and pressures; therefore, a direct comparison of performance by process simulation is not always possible. In the extreme cases, the design of a CO2 separation process may require predicting the CO2–IL equilibria for which there are no available solubility data. To address the need for this information, a semi‐empirical correlation was developed to estimate the dissolution of CO2 in CO2–IL solvent systems. The theoretical COSMO–RS calculation method was used to calculate the chemical potential of CO2 in a wide variety of ILs and the Soave–Redlich–Kwong equation was used to calculate the fugacity coefficient of the CO2 vapour phase. The model was correlated with available literature data, yielding an average error of AAR = 23% and small bias. © 2012 Canadian Society for Chemical Engineering 相似文献
998.
An Ester of β-Hydroxybutyrate Regulates Cholesterol Biosynthesis in Rats and a Cholesterol Biomarker in Humans 下载免费PDF全文
Martin F. Kemper Shireesh Srivastava M. Todd King Kieran Clarke Richard L. Veech Robert J. Pawlosky 《Lipids》2015,50(12):1185-1193
In response to carbohydrate deprivation or prolonged fasting the ketone bodies, β‐hydroxybutyrate (βHB) and acetoacetate (AcAc), are produced from the incomplete β‐oxidation of fatty acids in the liver. Neither βHB nor AcAc are well utilized for synthesis of sterols or fatty acids in human or rat liver. To study the effects of ketones on cholesterol homeostasis a novel βHB ester (KE) ((R)‐3‐hydroxybutyl (R)‐3‐hydroxybutyrate) was synthesized and given orally to rats and humans as a partial dietary carbohydrate replacement. Rats maintained on a diet containing 30‐energy % as KE with a concomitant reduction in carbohydrate had lower plasma cholesterol and mevalonate (?40 and ?27 %, respectively) and in the liver had lower levels of the mevalonate precursors acetoacetyl‐CoA and HMG‐CoA (?33 and ?54 %) compared to controls. Whole liver and membrane LDL‐R as well as SREBP‐2 protein levels were higher (+24, +67, and +91 %, respectively). When formulated into a beverage for human consumption subjects consuming a KE drink (30‐energy %) had elevated plasma βHB which correlated with decreased mevalonate, a liver cholesterol synthesis biomarker. Partial replacement of dietary carbohydrate with KE induced ketosis and altered cholesterol homeostasis in rats. In healthy individuals an elevated plasma βHB correlated with lower plasma mevalonate. 相似文献
999.
Synthesis and properties of cross‐linked polymers from epoxidized rubber seed oil and triethylenetetramine 下载免费PDF全文
Muhammad Yusuf Abduh Muhammad Iqbal Francesco Picchioni Robert Manurung Hero J. Heeres 《应用聚合物科学杂志》2015,132(40)
A series of epoxidized oils were prepared from rubber seed, soybean, jatropha, palm, and coconut oils. The epoxy content varied from 0.03 to 7.4 wt %, in accordance with the degree of unsaturation of the oils (lowest for coconut, highest for rubber seed oil). Bulk polymerization/curing of the epoxidized oils with triethylenetetramine (in the absence of a catalyst) was carried out in a batch setup (1 : 1 molar ratio of epoxide to primary amine groups, 100°C, 100 rpm, 30 min) followed by casting of the mixture in a steel mold (180°C, 200 bar, 21 h) and this resulted in cross‐linked resins. The effect of relevant pressing conditions such as time, temperature, pressure, and molar ratio of the epoxide and primary amine groups was investigated and modeled using multivariable nonlinear regression. Good agreement between experimental data and model were obtained. The rubber seed oil‐derived polymer has a Tg of 11.1°C, a tensile strength of 1.72 MPa, and strain at break of 182%. These values are slightly higher than for commercial epoxidized soybean oil (Tg of 6.9°C, tensile strength of 1.11 MPa, and strain at break of 145.7%). However, the comparison highlights the potential for these novel resins to be used at industrial/commercial level. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42591. 相似文献
1000.
Controlled synthesis and enhanced field emission characteristics of conical carbon nanotubular arrays 总被引:1,自引:0,他引:1
Santoshrupa Dumpala Abdelilah Safir David Mudd Robert W. Cohn Mahendra K. Sunkara Gamini U. Sumanasekera 《Diamond and Related Materials》2009,18(10):1262-1266
Conical carbon nanotubes (CCNTs) with unique structural characteristics arising from their tapered morphologies compared to uniform diameter carbon nanotubes, have been shown to exhibit enhanced field emission properties and support high current densities. Specifically, several CCNT arrays with different morphological characteristics (tip radius, aspect ratio, density and wall structure) were synthesized by variations in the process parameters using a microwave plasma chemical vapor deposition (MWCVD) reactor. The field emission characteristics for a CCNT array sample with a tip radius of 5 nm, density of 108/cm2 and having the highest aspect ratio exhibited a low turn-on electric field (< 0.7 V/μm) and a high field enhancement factor (β > 7500). Other samples with lower emission characteristics were attributed either to the presence of field screening effect resulting from higher CCNT density or due to the corresponding tip and wall characteristics. 相似文献