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41.
Jaroslav Kahovec 《Polymer Bulletin》1981,4(12):731-733
Summary Two methods of the introduction of aldehyde group into polystyrene skeleton are described. 相似文献
42.
Toxicity increases in ice containing monochlorophenols upon photolysis: environmental consequences 总被引:4,自引:0,他引:4
Bláha L Klánová J Klán P Janosek J Skarek M Růzicka R 《Environmental science & technology》2004,38(10):2873-2878
The toxic effects of photoproducts formed upon the photolysis of 2- and 4-chlorophenol (CP) frozen solutions in polycrystalline ice phase were determined with a bacterial luminescence test (Vibrio fisheri), and in vitro biomarker assay for dioxin-like effects (inductions of AhR-dependent luciferase in H4IIE-luc cells) and compared to the toxic effects of products of the same photoreaction in aquatic phase. Coupling photoproducts formed in ice samples (3'-chlorobiphenyl-2,4'-diol and 3-chlorobiphenyl-2,2'-diol from 2-CP photolysis and 5-chlorobiphenyl-2,4'-diol from 4-CP photolysis) were found to be more toxic to V. fisheri than parent CPs and elicited significant inductions of dioxin-like effects (the effective concentrations EC50 approximately 3 x 10(-5) mol L(-1) corresponded to known weaker ligands of AhR, such as nonplanar polychlorinated biphenyls or polycyclic aromatic hydrocarbons). To complete the picture, a photoproduct formed from 4-CP (5-chlorobiphenyl-2,4'-diol) was synthesized, and a detailed toxicity assessment with purified compound confirmed the results obtained with irradiated samples. Our findings support a recently proposed model according to which solar radiation can trigger the formation of new types of organic pollutants in polar ice or tropospheric ice cloud particles, presenting possibly greater risk to the environment than the parent compounds. 相似文献
43.
Two criticality dosimetry systems were tested by Czech participants during the intercomparison held in Valduc, France, June 2002. The first consisted of the thermoluminescent detectors (TLDs) (Al-P glasses) and Si-diodes as passive neutron dosemeters. Second, it was studied to what extent the individual dosemeters used in the Czech routine personal dosimetry service can give a reliable estimation of criticality accident exposure. It was found that the first system furnishes quite reliable estimation of accidental doses. For routine individual dosimetry system, no important problems were encountered in the case of photon dosemeters (TLDs, film badge). For etched track detectors in contact with the 232Th or 235U-Al alloy, the track density saturation for the spark counting method limits the upper dose at approximately 1 Gy for neutrons with the energy >1 MeV. 相似文献
44.
A finite element method often leads to large sparse symmetric and positive definite systems of linear equations. We consider parallel solvers based on the Schur complement method on homogeneous parallel machines with distributed memory. A finite element mesh is partitioned by graph partitioning. Such partitioning results in submeshes with similar numbers of elements and, consequently, submatrices of similar sizes. The submatrices are partially factorised. The time spent on the partial factorisation can be different, i.e., disbalanced, because methods exploiting the sparsity of submatrices are used. This paper proposes a Quality Balancing heuristic that modifies classic mesh partitioning so that the partial factorisation times are balanced, which saves overall computation time, especially for time dependent mechanical and nonstationary transport problems. 相似文献
45.
Josef Jirák Ladislav Koudelka Jaroslav Pospíšil Petr Mošner Lionel Montagne Laurent Delevoye 《Journal of Materials Science》2007,42(20):8592-8598
Glasses of the ternary system ZnO–Bi2O3–P2O5 were prepared and studied in two compositional series 50ZnO–xBi2O3–(50 − x)P2O5 and (50 − y)ZnO–yBi2O3–50P2O5. Two distinct glass-forming regions were found in the 50ZnO–xBi2O3–(50 − x)P2O5 glass series with x = 0–10 and 20–35 mol.% Bi2O3. All prepared Bi2O3-containing glasses reveal a high chemical durability. Small additions of Bi2O3 (∼5 mol.%) improve thermal stability of glasses. All glasses crystallize on heating within the temperature range of 505–583 °C.
Structural studies by Raman and 31P MAS NMR spectroscopies showed the rapid depolymerisation of phosphate chains within the first region with x = 0–15 and the presence of isolated Q0 phosphate units within the second region with x = 20–35. Raman studies showed that bismuth is incorporated in the glass structure in BiO6 units and their vibrational bands were observed within the spectral region of 350–700 cm−1. The evolution of properties and the spectroscopic data are both in accordance with a network former effect of Bi2O3. 相似文献
46.
Ivan Ostrovský Eva Pavlíková Jaroslav Blaško Renáta Górová Róbert Kubinec Milan Margetín Ladislav Soják 《International Dairy Journal》2009,19(9):545-549
The profile variations of approximately 70 fatty acids (FAs) in milk of ewes consuming total mixed rations (TMR) and grazing natural pasture were determined. Milk of ewes grazing pasture in May and September in the Slovak Republic contained 3-times more conjugated linoleic acid (CLA) (P < 0.001) and trans-vaccenic acid (TVA) (P < 0.001), and 2-times more α-linolenic acid (ALA) (P < 0.001) than that of ewes fed TMR. A doubling of the CLA and TVA contents of milk of ewes fed with TMR was achieved by changing to meadow hay containing a higher ALA content. Less availability of vegetation and lower ALA pasture content in summer (P < 0.001) caused a 2-fold decrease (P < 0.001) of CLA and TVA contents when compared with data obtained in May. With grass re-growth and an increase in pasture ALA content in September, the CLA and TVA contents rose to values similar to those obtained in May (P > 0.05). No significant differences in the FA composition in milk of ewes grazing on summer pasture at higher altitude were observed. 相似文献
47.
48.
Polyaniline is one of the most important conducting and responsive polymers. A molecular mechanism for the oxidation of aniline is proposed. This mechanism explains the specific features of aniline oligomerization and polymerization in various acidity ranges. The formation of polyaniline precipitates, colloids and thin films is reviewed and discussed on the basis of the chemistry of aniline oxidation. The generation of nanostructures, i.e. granules, nanotubes, nanowires and microspheres, is also considered. Oligomers containing phenazine constitutional units play an important role in self‐assembly to form templates. Polyaniline chains then grow from these templates and produce the various individual morphologies. Copyright © 2008 Society of Chemical Industry 相似文献
49.
Michal Hoznedl Ladislav Tajc Jaroslav Krejcik Lukas Bednar Kamil Sedlak Jiri Linhart 《Frontiers of Energy and Power Engineering in China》2009,3(3):321-329
In the past, increased attention was given to the development of an optimal shape for the inlet part of LP turbine casings
in SKODA POWER. A double-flow design is typically used for high power output turbines. An optimized shape for the internal
diffuser has been found, which transforms the kinetic energy of steam into increased pressure, thus effectively increasing
the thermodynamic efficiency of the stage. Some conclusions have been drawn from laboratory experiments, others derived directly
from on-site measurements at power plants. The conclusions from the development of double-flow turbines form the basis for
the design of the single-flow turbine arrangement. Single-flow design is typically used for lower output turbines. There are
still some limitations in applying this arrangement. The designer needs to resolve the bearing position and how to ensure
access to them. Reinforcing the ribs and supports are used, therefore, to ensure the rigidity of the entire casing. The optimization
of the single-flow diffuser shape is therefore the subject of the study presented below. 相似文献
50.