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排序方式: 共有126条查询结果,搜索用时 15 毫秒
21.
Yann Sarazin Pierre de Frmont Liana Annunziata Michel Duc Jean‐Franois Carpentier 《Advanced Synthesis \u0026amp; Catalysis》2011,353(8):1367-1374
Combinations of the discrete neutral allyl ansa‐lanthanidocenes {Me2C(Cp)(Flu)}Nd[1,3‐ (SiMe3)2C3H3] and rac‐{Me2C(Ind)2}Y[1,3‐ (SiMe3)2C3H3] with di(n‐butyl)magnesium constitute efficient binary catalytic systems for the stereocontrolled coordinative chain transfer polymerization of styrene, yielding near‐perfect syndio‐ and isospecific polystyrenes, respectively, with high activities and productivities. By adjusting the amount of di(n‐butyl)magnesium, up to 200 polymer chains can be generated per lanthabide center, and good control of the molecular weight features enables the tailoring of low to medium molecular weight polymers. 相似文献
22.
Edd JF Horowitz L Davalos RV Mir LM Rubinsky B 《IEEE transactions on bio-medical engineering》2006,53(7):1409-1415
This paper reports results of in vivo experiments that confirm the feasibility of a new minimally invasive method for tissue ablation, irreversible electroporation (IRE). Electroporation is the generation of a destabilizing electric potential across biological membranes that causes the formation of nanoscale defects in the lipid bilayer. In IRE, these defects are permanent and lead to cell death. This paper builds on our earlier theoretical work and demonstrates that IRE can become an effective method for nonthermal tissue ablation requiring no drugs. To test the capability of IRE pulses to ablate tissue in a controlled fashion, we subjected the livers of male Sprague-Dawley rats to a single 20-ms-long square pulse of 1000 V/cm, which calculations had predicted would cause nonthermal IRE. Three hours after the pulse, treated areas in perfusion-fixed livers exhibited microvascular occlusion, endothelial cell necrosis, and diapedeses, resulting in ischemic damage to parenchyma and massive pooling of erythrocytes in sinusoids. However, large blood vessel architecture was preserved. Hepatocytes displayed blurred cell borders, pale eosinophilic cytoplasm, variable pyknosis and vacuolar degeneration. Mathematical analysis indicates that this damage was primarily nonthermal in nature and that sharp borders between affected and unaffected regions corresponded to electric fields of 300-500 V/cm. 相似文献
23.
Bogdan Crisan Olga Soritau Mihaela Baciut Radu Campian Liana Crisan Grigore Baciut 《Particulate Science and Technology》2013,31(2):168-173
Although experimental studies in vitro and vivo have been numerous, the effects of laser irradiation on human fibroblast cells are poorly understood. The aim of this study was to assess the influence on three different laser wavelengths on nanoparticles components of the human fibroblast cells from oral tumor. The cells were irradiated by 830, 920, and 2940 nm laser wavelength. The irradiated cells were incubated and their mitochondrial activity was assessed by the MTT assay at 24, 48, and 72 h. It can be concluded that the laser light with 830 nm wavelength stimulates mitochondrial activity compared to the other two wavelengths, which produce inhibition. 相似文献
24.
25.
Preparation and characterisation of new-polyaluminum chloride-chitosan composite coagulant 总被引:1,自引:0,他引:1
In this study, the formulation of a novel polyaluminum chloride-chitosan composite coagulant that improves the coagulation process for natural organic matter (NOM) removal was investigated. The performance of the composite coagulant was tested using two water sources (synthetic and natural water) to develop a better understanding on the behaviour of the composite coagulant. Fourier Transform-Infra red (FT-IR) spectroscopy, ferron analysis and zeta potential studies were performed to characterise the composite coagulant. FT-IR analysis showed that there is an intermolecular interaction between Al species and chitosan molecules, while ferron analysis indicated that the distributions of Ala, Alb, and Alc in PACl-chitosan are different from those in PACl. At a low Al dosage (2.16 mg L−1), a much higher removal of NOM from synthetic water, as evidenced from UV254 and Dissolved Organic Carbon (DOC) measurements, was achieved by the composite coagulants in comparison to that removed by PACl or PACl and chitosan added separately. For natural water from the Myponga Reservoir, both polyaluminum chloride (PACl) and PACl-chitosan composite coagulants demonstrated similar dissolved organic carbon (DOC) percentage removal, whereas PACl-chitosan gave a slight improvement in removing the UV254 absorbing components of NOM. 相似文献
26.
The efficiency of using nanostructured silver in technological processes of making red wine has been studied with the purpose of substituting sulfur dioxide. For preparation of research objects, we used dry wine material of red grape variety "Saperavi". After completion of malolactic fermentation, the second racking the wine material off the lees and its treatment with antiseptics were carried out. Sulfur dioxide (Kadifit) and different doses of nanostructured silver were used. Microbiological investigation was performed on the presence of lactic bacteria after completion of malolactic fermentation and racking off the lees. The investigation of phenolic compounds was conducted at the following stages of technological processes: (1) after completion of alcoholic fermentation and racking off the lees; (2) after completion of malolactic fermentation; (3) after the second racking off the lees and treatment with antiseptics. By means of the HPLC analysis, the amounts ofcatechins, phenolcarbonic acids and flavonols were determined. It has been established that after conduction of malolactic fermentation in the process of racking the wine material off the lees and storage, the application of 0.6 mg/L of nano-silver for blocking of lactic-acid bacteria and inhibition of oxidation of phenolic compounds has the same effect as sulfitization with 50 mg/L of Kadifit. 相似文献
27.
Elmira Khusnutdinova Anastasiya Petrova Zulfia Zileeva Ulyana Kuzmina Liana Zainullina Yulia Vakhitova Denis Babkov Oxana Kazakova 《International journal of molecular sciences》2021,22(18)
A series of A-ring modified oleanolic and ursolic acid derivatives including C28 amides (3-oxo-C2-nicotinoylidene/furfurylidene, 3β-hydroxy-C2-nicotinoylidene, 3β-nicotinoyloxy-, 2-cyano-3,4-seco-4(23)-ene, indolo-, lactame and azepane) were synthesized and screened for their cytotoxic activity against the NCI-60 cancer cell line panel. The results of the first assay of thirty-two tested compounds showed that eleven derivatives exhibited cytotoxicity against cancer cells, and six of them were selected for complete dose–response studies. A systematic study of local SARs has been carried out by comparative analysis of potency distributions and similarity relationships among the synthesized compounds using network-like similarity graphs. Among the oleanane type triterpenoids, C2-[4-pyridinylidene]-oleanonic C28-morpholinyl amide exhibited sub-micromolar potencies against 15 different tumor cell lines and revealed particular selectivity for non-small cell lung cancer (HOP-92) with a GI50 value of 0.0347 μM. On the other hand, superior results were observed for C2-[3-pyridinylidene]-ursonic N-methyl-piperazinyl amide 29, which exhibited a broad-spectrum inhibition activity with GI50 < 1 μM against 33 tumor cell lines and <2 μM against all 60 cell lines. This compound has been further evaluated for cell cycle analysis to decipher the mechanism of action. The data indicate that compound 29 could exhibit both cytostatic and cytotoxic activity, depending on the cell line evaluated. The cytostatic activity appears to be determined by induction of the cell cycle arrest at the S (MCF-7, SH-SY5Y cells) or G0/G1 phases (A549 cells), whereas cytotoxicity of the compound against normal cells is nonspecific and arises from apoptosis without significant alterations in cell cycle distribution (HEK293 cells). Our results suggest that the antiproliferative effect of compound 29 is mediated through ROS-triggered apoptosis that involves mitochondrial membrane potential depolarization and caspase activation. 相似文献
28.
An investigation of the effects of some additives on zinc electrowinning from a weak acidic sulphate electrolyte prepared from an industrial waste product has been carried out. Experiments were done in the presence of additives such as aluminium sulphate, animal glue and an extract of horse-chestnut nuts (HCE), used alone or in different mixtures.Using a rotating disc electrode (RDE) and cyclic voltammetry, the influence of the additives on the polarization curves and on the voltammograms was studied. SEM was used to determine the structure and the morphology of deposits.The results indicated that the additives tested exert a beneficial effect on the quality of the zinc deposits. They increase the cathodic polarization and promote levelling. Al2(SO4)3 influences the reduction of zinc ions, increasing the nucleation overpotential and the deposition rate of zinc on the cathode. The conjoint use of Al2(SO4)3, animal glue and HCE results in smooth, slightly bright deposits, showing a beneficial effect of the mixture on zinc electrodeposition. The analysis of deposit purity suggested that the additives inhibit the discharge rate of impurity metal ions, such as copper and lead, whose deposition is diffusion controlled. 相似文献
29.
Liana Popesco 《Language Resources and Evaluation》1986,20(4):289-295
The article introduces an experimental system which produces multilingual semantic translations from relatively short texts
from a given context.
The system was conceived as an investigation instrument whose characteristics are the following:
—the elaboration of a single analyzer and generator able to receive, in the form of data, specific information concerning
national language, within the limits of a given area of application;
—the use of exclusively semantic internal representation, whose formation is derived from “frames” (an object is defined as
a list of “attribute-value” couples, permitting recursion);
—a single knowledge-base is used for each natural language as initial data (the grammar transmitted was of a semantic-syntacticatn type);
—the structure of grammar used in computer language processing being rarely as well adapted to analysis as to generation,
the system itself is provided with the possibility of transforming and reorganizing the information for more efficient use
at one stage of processing (thus, theatns are used directly in analysis, whereas for the purposes of generation they are “explored” and their information reorganized);
—to produce a text, the use of general structuring principles (independent of language) are experimented with. These principles
are given in the form of metarules. The application of these metarules to the restructured grammar of a natural language produces
specific structuration rules, peculiar to this language.
Although the system was conceived for any conceptual area or language, the present knowledge-base of the system (the experimental
support) is based on a collection of elementary exercises in three-dimensional geometry written in Rumanian and in French.
She does research in the CNRS group C.F. Picard headed by Professor Pitrat, University of Paris 6. 相似文献
30.
Liana Stoll Rosane Rech Simone Hickmann Flôres Sonia Marli Bohrz Nachtigall Alessandro de Oliveira Rios 《应用聚合物科学杂志》2018,135(33)
The use of vivid packaging colors is a strategy to attract consumers' attention and interest. In this context, the awareness of harmful effects caused by the use of synthetic colorants has led to an increasing interest in naturally derived alternatives. The use of carotenoids as colorants for polymeric materials represents an environmentally friendly way of obtaining colored packaging. The incorporation of carotenoids extracts rich in bixin, lycopene, and β‐carotene into poly(lactic acid) films was evaluated, where the presence of carotenoids (100 μg/g) reduced oxygen permeability and presented a lubricant effect, increasing films elasticity up to 50%. No effect on films crystallinity was observed. Carotenoids reduced films transparency and bixin was the most stable carotenoid at dark and light conditions. The color stability of films, evaluated through kinetic parameters of color degradation, presented Chroma half‐life times (40 °C/light) of 111, 51, and 5 days for bixin, lycopene, and β‐carotene, respectively. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46585. 相似文献