全文获取类型
收费全文 | 2604篇 |
免费 | 171篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 12篇 |
综合类 | 4篇 |
化学工业 | 778篇 |
金属工艺 | 8篇 |
机械仪表 | 39篇 |
建筑科学 | 97篇 |
矿业工程 | 1篇 |
能源动力 | 46篇 |
轻工业 | 533篇 |
水利工程 | 22篇 |
石油天然气 | 13篇 |
无线电 | 97篇 |
一般工业技术 | 292篇 |
冶金工业 | 592篇 |
原子能技术 | 12篇 |
自动化技术 | 231篇 |
出版年
2024年 | 12篇 |
2023年 | 31篇 |
2022年 | 128篇 |
2021年 | 143篇 |
2020年 | 54篇 |
2019年 | 65篇 |
2018年 | 102篇 |
2017年 | 94篇 |
2016年 | 109篇 |
2015年 | 73篇 |
2014年 | 111篇 |
2013年 | 166篇 |
2012年 | 139篇 |
2011年 | 167篇 |
2010年 | 125篇 |
2009年 | 121篇 |
2008年 | 118篇 |
2007年 | 102篇 |
2006年 | 95篇 |
2005年 | 86篇 |
2004年 | 65篇 |
2003年 | 56篇 |
2002年 | 56篇 |
2001年 | 31篇 |
2000年 | 34篇 |
1999年 | 28篇 |
1998年 | 32篇 |
1997年 | 31篇 |
1996年 | 35篇 |
1995年 | 23篇 |
1994年 | 29篇 |
1993年 | 22篇 |
1992年 | 34篇 |
1990年 | 23篇 |
1989年 | 22篇 |
1988年 | 17篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 15篇 |
1984年 | 22篇 |
1982年 | 8篇 |
1981年 | 23篇 |
1980年 | 7篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 6篇 |
1972年 | 6篇 |
排序方式: 共有2777条查询结果,搜索用时 15 毫秒
91.
Anna Siskova Jan Kral Jana Drabova Klara Cervena Kristyna Tomasova Jiri Jungwirth Tomas Hucl Pavel Kohout Sandra Summerova Ludmila Vodickova Pavel Vodicka Veronika Vymetalkova 《International journal of molecular sciences》2022,23(14)
A colorectal adenoma, an aberrantly growing tissue, arises from the intestinal epithelium and is considered as precursor of colorectal cancer (CRC). In this study, we investigated structural and numerical chromosomal aberrations in adenomas, hypothesizing that chromosomal instability (CIN) occurs early in adenomas. We applied array comparative genomic hybridization (aCGH) to fresh frozen colorectal adenomas and their adjacent mucosa from 16 patients who underwent colonoscopy examination. In our study, histologically similar colorectal adenomas showed wide variability in chromosomal instability. Based on the obtained results, we further stratified patients into four distinct groups. The first group showed the gain of MALAT1 and TALAM1, long non-coding RNAs (lncRNAs). The second group involved patients with numerous microdeletions. The third group consisted of patients with a disrupted karyotype. The fourth group of patients did not show any CIN in adenomas. Overall, we identified frequent losses in genes, such as TSC2, COL1A1, NOTCH1, MIR4673, and GNAS, and gene gain containing MALAT1 and TALAM1. Since long non-coding RNA MALAT1 is associated with cancer cell metastasis and migration, its gene amplification represents an important event for adenoma development. 相似文献
92.
Grevenstuk T Gonçalves S Domingos T Quintas C van der Hooft JJ Vervoort J Romano A 《Journal of the science of food and agriculture》2012,92(8):1638-1642
BACKGROUND: The aim of this study was to investigate the growth‐inhibiting efficacy of Drosera intermedia extracts (water, methanol and n‐hexane) against four food spoilage yeasts and five filamentous fungi strains responsible for food deterioration and associated with mycotoxin production, in order to identify potential antimycotic agents. RESULTS: The n‐hexane extract showed a broad activity spectrum against all tested microorganisms, followed, in activity, by the methanol and water extracts. The major component of the n‐hexane extract was purified using a solid‐phase extraction column and identified as plumbagin. Results show that high‐purity plumbagin can be produced from D. intermedia cultures following a simple and effective isolation procedure. A sample of purified plumbagin was tested against the same panel of microorganisms and high growth‐inhibiting capacity was observed. Minimum inhibitory concentrations less than 2 µg mL?1 were obtained against the filamentous fungi. In the case of the species Aspergillus fumigatus, A. niger and A. flavus , activities comparable to miconazole were obtained. CONCLUSION: The results obtained provided evidence of the antimycotic activity of plumbagin, suggesting that D. intermedia could be the source of an interesting compound for the food industry as an alternative to preservatives. Copyright © 2011 Society of Chemical Industry 相似文献
93.
Abstract The constituents of the essential oil extracted from the needles and twigs of white spruce - Picea glauca (Moench) Voss -by steam distillation are analyzed by GC-MS and GC with authentic samples. The analysis allows for the Identification of 39 constituents. 相似文献
94.
Franziska Punt Stefan Doose Ann-Christin Böttcher Prof. Dr.-Ing. Sandra Breitung-Faes Prof. Dr.-Ing. Arno Kwade 《化学,工程师,技术》2023,95(1-2):59-67
To investigate the mechanical processes of Li-ion battery recycling in more detail, models for the different unit processes are to be developed. Here, model approaches for the cutting mill and the zig-zag-sifter are presented. These models are to be used in dynamic flow sheet simulations, with which the individual unit processes as well as the combination to a small process chain were simulated. Thereby, the dynamic interactions between the process steps were investigated, which can be used later for optimization and regulation of the processes. The particle sizes after the cutting mill process as well as the mass flow between the processes influence the separation behavior of the sifter. These changes in the separation function due to an increasing mass flow out of the mill are shown. 相似文献
95.
Within this study relationships between material formulation and processing parameters and the morphology (vacuole formation) of thermotropic systems with fixed domains (TSFD) for overheating protection purposes were investigated. Main aim was on improving light shielding efficiency of TSFD based on UV curable acrylate resins by optimization of selected key parameters including photo‐initiator type and content, type of reactive diluent, radiation intensity/dose, and thermal treatment of layers during manufacturing. Variations of type of reactive diluent and thermal treatment had a minor effect on overheating protection performance. Utilization of photo‐bleaching photo‐initiator of acylphospine oxide type instead of a blend of conventional Type I (α‐hydroxy ketone type) and Type II (benzophenone) photo‐initiators enabled reduction of radiation dose to achieve properly cured layers. The results revealed that a significant reduction of radiation intensity/dose prevented formation of vacuoles. Consequently, light shielding efficiency of TSFD was enhanced significantly. Nevertheless, obtained scattering domain size was inappropriate for optimum light shielding efficiency and requires further optimization strategies. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3299–3310, 2013 相似文献
96.
Mechanisms of strength toss which affect the durability of epoxy adhesive bonds in moist environments were investigated for electroplated zinc and cold rolled steel substrates. Activation energies for adhesion loss, formation of corrosion product on the substrate surface, and moisture diffusion in the adhesive were determined experimentally. For cold rolled steel substrates, the activation energy for adhesion loss was identical, within experimental error, to the measured activation energy for moisture diffusion in the adhesive. Both of these values were substantially less (=40%) than the activation energy for formation of corrosion product. This confirms the previous results of Gledhill and Kinloch (J. Adhesion 6, 315 (1974)), who attributed strength loss to thermodynamic instability of the adhesive/substrate interface due to the presence of moisture. In contrast, for electroplated zinc substrates, activation energies for adhesion loss and corrosion product formation were essentially equal, and were both significantly higher than that for moisture diffusion. Consequently, it was concluded that corrosion of the electroplated zinc layer was responsible for bond strength loss. Formation of corrosion product in the bond was not, therefore, a post-failure phenomenon as was the case for cold rolled steel. 相似文献
97.
Cristina Locatelli Alessandro Minguzzi Alberto Vertova Sandra Rondinini 《Journal of Applied Electrochemistry》2013,43(2):171-179
In this work, SnO2 + IrO2 mixed oxides are studied as electrocatalysts for the oxygen reduction reaction (ORR) in alkaline media by means of voltammetric techniques under controlled mass transfer conditions thanks to the use of rotating (ring) disk electrodes (RDE/RRDE). The oxides, prepared by sol–gel methodology, are supported on the disk electrodes using a thin layer of anionic exchange polymer as gluing agent. The amount of deposited polymer was optimized to avoid any limitation due to the diffusion of reactant/products across the film thickness. The mixed oxides were prepared at the following mole fractions of IrO2: $ x_{{{\text{IrO}}_{ 2} }} $ = 0.15, 0.31, 0.55, 0.73, and 1. The role of composition was studied in terms of the reaction pathways and the relevant fraction of H2O2 production, together with the potentials of the onset of ORR. The fraction of sites able to give proton/hydroxyl and electron transfers is also determined and discussed. The results point to the best performance of low-Ir containing mixtures and to their low sensitivity to the presence of methanol, a key feature in the case of crossover in alkaline direct alcohol fuel cells. 相似文献
98.
Sandra Starke Marco Went Andrea Prager Agnes Schulze 《Reactive and Functional Polymers》2013,73(5):698-702
A novel technique for the covalent immobilization of trypsin in a one-step reaction using low-energy electron beam is described. The enzyme immobilization was applied on poly(ethersulfone) and poly(vinylidene fluoride) microfiltration membranes. For this purpose, the membranes were dipped in an aqueous solution of trypsin followed by electron beam treatment.The effect of irradiation conditions on the immobilization was investigated, as well as the resulting membrane properties with respect to enzymatic activity, immobilized enzyme concentration, pure water flux, scanning electron microscopy, and porosimetry. This technique shall provide a simple, inexpensive method for enzyme immobilization on various polymer membranes and offer a tool for the application in enzymatic membrane reactors. 相似文献
99.
Wittig de Penna E Curia A Calderón S López L Fuenzalida R Hough G 《Archivos latinoamericanos de nutrición》2005,55(1):77-85
The present work was designed in order to obtain the cut off point, to be used in a shelf life study on whole stirred strawberry yogurt. The study was simultaneously carried out in Argentina, Chile and Costa Rica, assaying the same kind of product, elaborated in each one of the countries. The sensory quality parameters obtained from trained panelists and the consumers acceptability, were correlated by using the cut off point methodology through a quality evaluation by the Karlsruhe scale. According to preliminary studies, the storage at 42 degrees C produced considerable damage on parameters such as pH, acidity (volumetric assay), viscosity and sensory quality. For each sample, the cut off point was determined. This value corresponds to the threshold score for the sensory quality, where the consumer starts to perceive negative changes in the product, when comparing with the fresh product. The rejection percentage was also calculated according to the cut off point. The cut off points and the percentage of rejection obtained by the three participating countries were similar. Data obtained from Costa Rica showed changes in color, acidity and rancidity. Argentinean yogurts developed acidity that had a negative effect on texture, appearance and residual flavors. Chilean samples presented a sensory quality that remains almost without change through the studied time. The differences of the deterioration pattern amongst the three countries, demonstrates that the products are different in formulation and elaboration process, in spite of been the same kind of yogurt. This could be explained by differences specified in the regulation of each country. 相似文献
100.