全文获取类型
收费全文 | 1108篇 |
免费 | 22篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 2篇 |
综合类 | 3篇 |
化学工业 | 114篇 |
金属工艺 | 4篇 |
机械仪表 | 6篇 |
建筑科学 | 24篇 |
矿业工程 | 3篇 |
能源动力 | 8篇 |
轻工业 | 120篇 |
水利工程 | 5篇 |
石油天然气 | 3篇 |
无线电 | 13篇 |
一般工业技术 | 74篇 |
冶金工业 | 699篇 |
原子能技术 | 1篇 |
自动化技术 | 53篇 |
出版年
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 14篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 10篇 |
2017年 | 11篇 |
2016年 | 10篇 |
2015年 | 8篇 |
2014年 | 16篇 |
2013年 | 26篇 |
2012年 | 25篇 |
2011年 | 43篇 |
2010年 | 20篇 |
2009年 | 15篇 |
2008年 | 28篇 |
2007年 | 25篇 |
2006年 | 18篇 |
2005年 | 17篇 |
2004年 | 17篇 |
2003年 | 17篇 |
2002年 | 11篇 |
2000年 | 7篇 |
1999年 | 24篇 |
1998年 | 177篇 |
1997年 | 117篇 |
1996年 | 70篇 |
1995年 | 59篇 |
1994年 | 31篇 |
1993年 | 42篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 16篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 9篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1977年 | 25篇 |
1976年 | 64篇 |
1975年 | 9篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1971年 | 2篇 |
排序方式: 共有1132条查询结果,搜索用时 0 毫秒
31.
32.
Juliana Starling Cleiton Moreira da Silva Maria Sylvia Silva Dantas Ângelo de Fátima Rodrigo L. Oréfice 《International Journal of Adhesion and Adhesives》2011,31(7):767-774
In an attempt to enrich the world of dentistry through the development of new materials, this study proposes to synthesize and incorporate a monomer containing the N-hydroxysuccinimide (NHS) ester reactive group to a dental adhesive. As such, this study developed a simple method to obtain NHS esters by employing acrylic acid (AA) and NHS in the presence of EDC (N-ethyl-N′-(3-dimethylaminopropyl)carbodiimide), from an aprotic medium. The experimental N-acryloxysuccinimide (NSA) monomer was analyzed by infrared spectroscopy (FTIR) and nuclear magnetic resonance of hydrogen (1H NMR). This monomer was then incorporated within a prepared dental adhesive, in a 5% proportion. The modified adhesive, containing NSA, was applied to the dental surface of bovine teeth to obtain an adhesive/dentin interface in vitro. The characterization of this interface by Raman spectroscopy presented the formation of new amide bonds. Moreover, through scanning electron microscopy (SEM), it became possible to observe an intense penetration of this modified adhesive on the dental surface. Considering the outcome, it can be concluded that the synthesized NSA monomer provided a favorable condition for the dental adhesives to interact chemically with the dentin collagen fibers. 相似文献
33.
Porous Perovskite Fibers – Preparation by Wet Phase Inversion Spinning and Catalytic Activity 下载免费PDF全文
Sandy Kaiser Erik Reichelt Sylvia E. Gebhardt Matthias Jahn Alexander Michaelis 《化学工程与技术》2014,37(7):1146-1154
Porous perovskite (LaMnO3) fibers were prepared by means of wet phase inversion spinning. The influence of different spinning procedures, slurry and coagulation bath composition on fiber shape and pore morphology was studied. The catalytic activity of the prepared fibers was tested for carbon monoxide oxidation as a model reaction in a differential recycle reactor. The results revealed that by suitable choice of process conditions porous catalytically active fibers can be prepared. Catalytic measurements confirmed that the catalytic fibers exhibit an open structure that allows full utilization of the catalytically active surface without intraparticle diffusional limitations. 相似文献
34.
Paraoxonase 1 (PON 1) has antioxidant and cardioprotective properties and is abnormally low in type 2 diabetic serum. This
study aimed to determine the effect of type 2 diabetes and meals rich in saturated fat and oleic acid on PON1 activity in
chylomicrons and very low density lipoproteins (VLDL). PON1 arylesterase activity was measured in chylomicrons and VLDL that
were isolated in serum from 20 patients with type 2 diabetes and 20 age- and gender-matched, overweight controls 3 h after
meals rich in cream or olive oil in a randomized, cross-over study. Chylomicron–PON1 activity (45%, P = 0.02), ratio chylomicron–PON1/chylomicron–triacylglycerides (TAG) (42%, P = 0.03) and chylomicron–protein content (46%, P < 0.001) were significantly lower in patients with type 2 diabetes compared with controls after the olive oil meal with comparable
findings after the meal rich in cream. After ingestion of olive oil, chylomicron–PON1 activity was significantly higher in
controls (P = 0.01) and marginally higher (P = 0.06) in diabetic patients and chylomicron–TAG were significantly (P < 0. 05) higher in both groups of subjects, compared with values after ingestion of cream. VLDL–PON1 increased (two-fold)
significantly (P < 0.003) during both meals. Chylomicron-PON1 activity was correlated significantly with chylomicron–protein (P < 0.001, n = 40) and with postprandial serum PON1 activity (P ≤ 0.001, n = 40). Our data suggest that type 2 diabetes is associated with abnormally low chylomicron–PON1 activity after fatty meals
and this may be linked to lower chylomicron–protein content and serum PON1 activity. Switching from saturated fat to olive
oil in the meal increases PON1 activity in the chylomicron fraction largely due to increased numbers of chylomicron particles. 相似文献
35.
F Germani A Pesce A Venturini L Moens M Bolognesi S Dewilde M Nardini 《International journal of molecular sciences》2012,13(7):8025-8037
The nerve tissue mini-hemoglobin from Cerebratulus lacteus (CerHb) displays an essential globin fold hosting a protein matrix tunnel held to allow traffic of small ligands to and from the heme. CerHb heme pocket hosts the distal TyrB10/GlnE7 pair, normally linked to low rates of O(2) dissociation and ultra-high O(2) affinity. However, CerHb affinity for O(2) is similar to that of mammalian myoglobins, due to a dynamic equilibrium between high and low affinity states driven by the ability of ThrE11 to orient the TyrB10 OH group relative to the heme ligand. We present here the high resolution crystal structures of CerHb in the unligated and carbomonoxy states. Although CO binds to the heme with an orientation different from the O(2) ligand, the overall binding schemes for CO and O(2) are essentially the same, both ligands being stabilized through a network of hydrogen bonds based on TyrB10, GlnE7, and ThrE11. No dramatic protein structural changes are needed to support binding of the ligands, which can freely reach the heme distal site through the apolar tunnel. A lack of main conformational changes between the heme-unligated and -ligated states grants stability to the folded mini-Hb and is a prerequisite for fast ligand diffusion to/from the heme. 相似文献
36.
Dr. Marcel Culcasi Dr. Caroline Delehedde Dr. Mathieu Esgulian Dr. Mathieu Cassien Dr. Mathieu Chocry Prof. Dr. Antal Rockenbauer Dr. Sylvia Pietri Dr. Sophie Thétiot-Laurent 《Chembiochem : a European journal of chemical biology》2023,24(8):e202200749
The mitochondrion, an essential organelle involved in cellular respiration, energy production, and cell death, is the main cellular source of reactive oxygen species (ROS), including superoxide. Mitochondrial diseases resulting from uncontrolled/excess ROS generation are an emerging public health concern and there is current interest in specific mitochondriotropic probes to get information on in-situ ROS production. As such, nitrones vectorized by the triphenylphosphonium (TPP) cation have recently drawn attention despite reported cytotoxicity. Herein, we describe the synthesis of 13 low-toxic derivatives of N-benzylidene-1-diethoxyphosphoryl-1-methylethylamine N-oxide (PPN) alkyl chain-grafted to a pyridinium, triethylammonium or berberinium lipophilic cation. These nitrones showed in-vitro superoxide quenching activity and EPR/spin-trapping efficiency towards biologically relevant free radicals, including superoxide and hydroxyl radicals. Their mitochondrial penetration was confirmed by 31P NMR spectroscopy, and their anti-apoptotic properties were assessed in Schwann cells treated with hydrogen peroxide. Two pyridinium-substituted PPNs were identified as potentially better alternatives to TPP nitrones conjugates for studying mitochondrial oxidative damage. 相似文献
37.
Michael K. Cinibulk Gareth Thomas Sylvia M. Johnson 《Journal of the American Ceramic Society》1992,75(8):2044-2049
The oxidation behavior and microstructure of the oxidized surfaces of RE2 Si2 O7 –Si3 N4 ceramics were investigated. The high oxidation resistance of these materials at 1400°C is attributed to the minimization of amorphous phases via devitrification to disilicates that are in equilibrium with SiO2 , the oxidation product of Si3 N4 . Crystals of RE2 Si2 O7 grew out of the surface silicate in prefered orientations that were dictated by crystal structure. The morphology of the microstructure of the oxidized surfaces was shown to be partially dependent on the concentration of impurities; the presence of Ca was found to coincide with the growth of Gd2 Si2 O7 and Dy2 Si2 O7 crystals with high aspect ratios. 相似文献
38.
The viscoelastic properties of poly(n‐butyl acrylate), poly(ethyl acrylate) and poly(methyl acrylate) melts have been studied using samples that varied in both molar mass and the mol% branched repeat units, these properties having been previously determined by gel permeation chromatography and 13C NMR spectroscopy, respectively. Poly(n‐butyl acrylate) was studied most extensively using seven samples; one sample of poly(n‐butyl acrylate), two samples of poly(ethyl acrylate) and one sample of poly(methyl acrylate) were used to study the effect of side‐group size. Storage and loss moduli were measured over a range of frequency (1 × 10?3 to 1 × 102 rad s?1) at temperatures from Tg + 20 °C to Tg + 155 °C and then shifted to form master curves at Tg + 74 °C through use of standard superposition procedures. The plateau regions were not distinct due to the broad molar mass distributions of the polyacrylates. Hence, the upper and lower limits of shear storage modulus from the nominal ‘plateau’ region of the curves for the seven poly(n‐butyl acrylate) samples were used to calculate the chain molar mass between entanglements, Me, which gave the range 13.0 kg mol?1 < Me < 65.0 kg mol?1. The Graessley–Edwards dimensionless interaction density and dimensionless contour length concentration were calculated for poly(n‐butyl acrylate) using the mean value of plateau modulus (1.2 × 105 Pa) and three different methods for estimation of the Kuhn length; the data fitted closely to the Graessley–Edwards universal plot. The Williams–Landel–Ferry C1 and C2 parameters were determined for each of the polyacrylates; the data for the poly(n‐butyl acrylate) samples indicate an overall reduction in C1 and C2 as the degree of branching increases. Although the values of C1 and C2 were different for poly(n‐butyl acrylate), poly(ethyl acrylate) and poly(methyl acrylate), there is no trend for variation with structure. Thus the viscoelastic properties of the polyacrylate melts are similar to those for other polymer melts and, for the samples investigated, the effect of molar mass appears to dominate the effect of branching. © 2001 Society of Chemical Industry 相似文献
39.
Nadir Erbilgin Jack D. Stein Robert E. Acciavatti Nancy E. Gillette Sylvia R. Mori Kristi Bischel Jonathan A. Cale Carline R. Carvalho David L. Wood 《Journal of chemical ecology》2017,43(2):172-179
Woodwasps in Sirex and related genera are well-represented in North American conifer forests, but the chemical ecology of native woodwasps is limited to a few studies demonstrating their attraction to volatile host tree compounds, primarily monoterpene hydrocarbons and monoterpene alcohols. Thus, we systematically investigated woodwasp-host chemical interactions in California’s Sierra Nevada and West Virginia’s Allegheny Mountains. We first tested common conifer monoterpene hydrocarbons and found that (?)-α-pinene, (+)-3-carene, and (?)-β-pinene were the three most attractive compounds. Based on these results and those of earlier studies, we further tested three monoterpene hydrocarbons and four monoterpene alcohols along with ethanol in California: monoterpene hydrocarbons caught 72.3% of all woodwasps. Among monoterpene hydrocarbons, (+)-3-carene was the most attractive followed by (?)-β-pinene and (?)-α-pinene. Among alcohols, ethanol was the most attractive, catching 41.4% of woodwasps trapped. Subsequent tests were done with fewer selected compounds, including ethanol, 3-carene, and ethanol plus (?)-α-pinene in both Sierra Nevada and Allegheny Mountains. In both locations, ethanol plus (?)-α-pinene caught more woodwasps than other treatments. We discussed the implications of these results for understanding the chemical ecology of native woodwasps and invasive Sirex noctilio in North America. In California, 749 woodwasps were caught, representing five species: Sirex areolatus Cresson, Sirex behrensii Cresson, Sirex cyaneus Fabricius, Sirex longicauda Middlekauff, and Urocerus californicus Norton. In West Virginia 411 woodwasps were caught representing four species: Sirex edwardsii Brullé, Tremex columba Linnaeus, Sirex nigricornis F., and Urocerus cressoni Norton. 相似文献
40.
Cover Picture: Development of Potent and Metabolically Stable APJ Ligands with High Therapeutic Potential (ChemMedChem 21/2016) 下载免费PDF全文