全文获取类型
收费全文 | 997篇 |
免费 | 55篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 14篇 |
综合类 | 1篇 |
化学工业 | 263篇 |
金属工艺 | 19篇 |
机械仪表 | 38篇 |
建筑科学 | 27篇 |
矿业工程 | 3篇 |
能源动力 | 32篇 |
轻工业 | 17篇 |
水利工程 | 5篇 |
石油天然气 | 4篇 |
无线电 | 75篇 |
一般工业技术 | 290篇 |
冶金工业 | 40篇 |
原子能技术 | 21篇 |
自动化技术 | 205篇 |
出版年
2024年 | 1篇 |
2023年 | 14篇 |
2022年 | 47篇 |
2021年 | 48篇 |
2020年 | 30篇 |
2019年 | 32篇 |
2018年 | 26篇 |
2017年 | 34篇 |
2016年 | 37篇 |
2015年 | 35篇 |
2014年 | 44篇 |
2013年 | 57篇 |
2012年 | 64篇 |
2011年 | 79篇 |
2010年 | 39篇 |
2009年 | 50篇 |
2008年 | 59篇 |
2007年 | 52篇 |
2006年 | 48篇 |
2005年 | 39篇 |
2004年 | 40篇 |
2003年 | 33篇 |
2002年 | 24篇 |
2001年 | 14篇 |
2000年 | 10篇 |
1999年 | 14篇 |
1998年 | 19篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 12篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 2篇 |
1967年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有1054条查询结果,搜索用时 0 毫秒
21.
Graph structure in the Web 总被引:11,自引:0,他引:11
Andrei Broder Ravi Kumar Farzin Maghoul Prabhakar Raghavan Sridhar Rajagopalan Raymie Stata Andrew Tomkins Janet Wiener 《Computer Networks》2000,33(1-6)
The study of the Web as a graph is not only fascinating in its own right, but also yields valuable insight into Web algorithms for crawling, searching and community discovery, and the sociological phenomena which characterize its evolution. We report on experiments on local and global properties of the Web graph using two AltaVista crawls each with over 200 million pages and 1.5 billion links. Our study indicates that the macroscopic structure of the Web is considerably more intricate than suggested by earlier experiments on a smaller scale. 相似文献
22.
Andrei Chychko Lidong Teng Seshadri Seetharaman 《Metallurgical and Materials Transactions B》2012,43(5):1078-1085
The kinetics of slag foaming by limestone particles was studied at 1773?K (1500?°C) with the aid of an X-ray imaging system. Two models were implemented to describe the decrease in foam height with the time on the basis of the lowering of the average temperature and CaO shell formation during decomposition reaction. The energy impact of carbonate additions was studied on an industrial scale in a 100-ton electric arc furnace (EAF). It was found that, in the case of the addition of carbonates after the scrap is completely molten, the heat effects for limestone and dolomite (2255 and 2264?kJ/kg, respectively) were only 70?pct from theoretical values. Comparing these values with similar additions during the scrap melting stage shows that the energy requirements in the case of carbonate additions to steel bath are much smaller. It was found from the trial heats with dolomite addition to the steel bath that the partial substitution of lime by raw dolomite can be made without an increase in energy consumption. 相似文献
23.
24.
Maxwell A. Astle Graham A. Rance Hannah J. Loughlin Thomas D. Peters Andrei N. Khlobystov 《Advanced functional materials》2019,29(17)
The principle of a “catalytic nanosponge” that combines the catalysis of organosulfur oxidation and sequestration of the products from reaction mixtures is demonstrated. Group VI metal oxide nanoparticles (CrOx, MoOx, WOx) are embedded within hollow graphitized carbon nanofibers (GNFs), which act as nanoscale reaction vessels for oxidation reactions used in the decontamination of fuel. When immersed in a model liquid alkane fuel contaminated with organosulfur compounds (benzothiophene, dibenzothiophene, dimethyldibenzothiophene), it is found that MoO2@GNF nanoreactors, comprising 30 nm molybdenum dioxide nanoparticles grown within the channel of GNFs, show superior abilities toward oxidative desulfurization (ODS), affording over 98% sulfur removal at only 5.9 mol% catalyst loading. The role of the carbon nanoreactor in MoO2@GNF is to enhance the activity and stability of catalytic centers over at least 5 cycles. Surprisingly, the nanotube cavity can selectively absorb and remove the ODS products (sulfoxides and sulfones) from several model fuel systems. This effect is related to an adsorptive desulfurization (ADS) mechanism, which in combination with ODS within the same material, yields a “catalytic nanosponge” MoO2@GNF. This innovative ODS and ADS synergistic functionality negates the need for a solvent extraction step in fuel desulfurization and produces ultralow sulfur fuel. 相似文献
25.
With the increasing interest in biopolymer nanofibers for diverse applications, the characterization of these materials in the physiological environment has become of equal interest and importance. This study performs first-time simulated body fluid (SBF) degradation and tensile mechanical analyses of blended fish gelatin (FGEL) and polycaprolactone (PCL) nanofibrous meshes prepared by a high-throughput free-surface alternating field electrospinning. The thermally crosslinked FGEL/PCL nanofibrous materials with 84–96% porosity and up to 60 wt% PCL fraction demonstrate mass retention up to 88.4% after 14 days in SBF. The trends in the PCL crystallinity and FGEL secondary structure modification during the SBF degradation are analyzed by Fourier transform infrared spectroscopy. Tensile tests of such porous, 0.1–2.2 mm thick FGEL/PCL nanofibrous meshes in SBF reveal the ultimate tensile strength, Young's modulus, and elongation at break within the ranges of 60–105 kPa, 0.3–1.6 MPa, and 20–70%, respectively, depending on the FGEL/PCL mass ratio. The results demonstrate that FGEL/PCL nanofibrous materials prepared from poorly miscible FGEL and PCL can be suitable for selected biomedical applications such as scaffolds for skin, cranial cruciate ligament, articular cartilage, or vascular tissue repair. 相似文献
26.
Isaac Zentner Luz‐Jeannette Sierra Ayesha K. Fraser Lina Maciunas Marie K. Mankowski Dr. Andrei Vinnik Dr. Peter Fedichev Roger G. Ptak Dr. Julio Martín‐García Dr. Simon Cocklin 《ChemMedChem》2013,8(3):426-432
The development of drug resistance remains a critical problem for current HIV‐1 antiviral therapies, creating a need for new inhibitors of HIV‐1 replication. We previously reported on a novel anti‐HIV‐1 compound, N2‐(phenoxyacetyl)‐N‐[4‐(1‐piperidinylcarbonyl)benzyl]glycinamide ( 14 ), that binds to the highly conserved phosphatidylinositol (4,5)‐bisphosphate (PI(4,5)P2) binding pocket of the HIV‐1 matrix (MA) protein. In this study, we re‐evaluate the hits from the virtual screen used to identify compound 14 and test them directly in an HIV‐1 replication assay using primary human peripheral blood mononuclear cells. This study resulted in the identification of three new compounds with antiviral activity; 2‐(4‐{[3‐(4‐fluorophenyl)‐1,2,4‐oxadiazol‐5‐yl]methyl})‐1‐piperazinyl)‐N‐(4‐methylphenyl)acetamide ( 7 ), 3‐(2‐ethoxyphenyl)‐5‐[[4‐(4‐nitrophenyl)piperazin‐1‐yl]methyl]‐1,2,4‐oxadiazole ( 17 ), and N‐[4‐ethoxy‐3‐(1‐piperidinylsulfonyl)phenyl]‐2‐(imidazo[2,1‐b][1,3]thiazol‐6‐yl)acetamide ( 18 ), with compound 7 being the most potent of these hits. Mechanistic studies on 7 demonstrated that it directly interacts with and functions through HIV‐1 MA. In accordance with our drug target, compound 7 competes with PI(4,5)P2 for MA binding and, as a result, diminishes the production of new virus. Mutation of residues within the PI(4,5)P2 binding site of MA decreased the antiviral effect of compound 7 . Additionally, compound 7 displays a broadly neutralizing anti‐HIV activity, with IC50 values of 7.5–15.6 μM for the group M isolates tested. Taken together, these results point towards a novel chemical probe that can be used to more closely study the biological role of MA and could, through further optimization, lead to a new class of anti‐HIV‐1 therapeutics. 相似文献
27.
Munmun Maiti Leentje Persoons Prof. Graciela Andrei Prof. Robert Snoeck Prof. Jan Balzarini Prof. Piet Herdewijn 《ChemMedChem》2013,8(6):985-993
Among the many prodrug approaches aimed at delivering nucleoside monophosphates into cells, the phosphoramidate ProTide approach is one that has shown success, which has made it possible for some of the phosphoramidates to enter into clinical trials. Herein, we report the synthesis and antiviral activity of a series of phosphoramidate ProTides designed to bypass the thymidine kinase (TK) dependence of the parent nucleoside analogues. Phosphoramidate derivatives of (E)‐5‐(2‐bromovinyl)‐2′‐deoxyuridine (BVDU) that contain L ‐alanine or pivaloyloxymethyl iminodiacetate (IDA‐POM) exhibit anti‐HSV‐1 and anti‐VZV activity in cell cultures, but they largely lost antiviral potency against TK‐deficient virus strains. Among deazapurine nucleosides and their phosphoramidate derivatives, the 7‐deazaadenine containing nucleosides and their phosphoramidate triester derivatives showed weak antiviral activity against VZV. Apparently, intracellular nucleotide delivery with these phosphoramidates is partly successful. However, none of the compound prodrugs showed superior activity to their parent drugs. 相似文献
28.
Most recent data on hairy systems demonstrated their excellent adhesion and high reliability of contact. In contrast to smooth systems, some hairy systems seem to operate with dry adhesion and do not require supplementary fluids in the contact area. Contacting surfaces in such devices are subdivided into patterns of micro- or nanostructures with a high aspect ratio (setae, hairs, pins). The size of single points gets smaller and their density gets higher as the body mass increases. Previous authors explained this general trend by applying the JKR theory, according to which splitting up the contact into finer subcontacts increases adhesion. Fundamental importance of contact splitting for adhesion on smooth and rough substrata has been previously explained by a very small effective elastic modulus of the fibre array. This article provides the first experimental evidence of adhesion enhancement by division of contact area. A patterned surface made out of polyvinylsiloxane (PVS) has significantly higher adhesion on a glass surface than a smooth sample made out of the same material. This effect is even more pronounced on curved substrata. An additional advantage of patterned surfaces is the reliability of contact on various surface profiles and the increased tolerance to defects of individual contacts. 相似文献
29.
Artur Noole Maksim Oeka Tnis Pehk Mario
eren Ivar Jrving Mark R. J. Elsegood Andrei V. Malkov Margus Lopp Tnis Kanger 《Advanced Synthesis \u0026amp; Catalysis》2013,355(5):829-835
3‐Chlorooxoindoles have emerged as versatile precursors in the synthesis of spirocyclopropyl oxindoles. High enantio‐ and diastereoselectivity was attained under conditions of both iminium/enamine and H‐bonding catalysis. 相似文献
30.
This work presents experimental results on pickup velocity (critical velocity) measurements for a variety of particulate solids. The present experiments together with previously published experiments of a number of researchers encompass about 100 measurements of 24 materials for a wide range of particle sizes, shapes and densities. Based on the experimental results, three zones are defined by establishing simple relationships between the Reynolds and Archimedes numbers. The empirical relationships were further modified by taking into account the pipe diameter and particle shape (sphericity). The three-zone model was shown to reasonably correlate to Geldart's classification groups. 相似文献