全文获取类型
收费全文 | 366篇 |
免费 | 16篇 |
专业分类
电工技术 | 4篇 |
综合类 | 4篇 |
化学工业 | 62篇 |
金属工艺 | 4篇 |
机械仪表 | 12篇 |
建筑科学 | 27篇 |
能源动力 | 35篇 |
轻工业 | 34篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 44篇 |
一般工业技术 | 54篇 |
冶金工业 | 33篇 |
原子能技术 | 18篇 |
自动化技术 | 43篇 |
出版年
2023年 | 7篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 17篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 17篇 |
2015年 | 6篇 |
2014年 | 12篇 |
2013年 | 33篇 |
2012年 | 22篇 |
2011年 | 33篇 |
2010年 | 26篇 |
2009年 | 32篇 |
2008年 | 17篇 |
2007年 | 21篇 |
2006年 | 18篇 |
2005年 | 9篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有382条查询结果,搜索用时 31 毫秒
21.
Homayun K. Navaz Ali Zand Theresa Atkinson Albert Nowakowski Amir Gat Sari Paikoff 《American Institute of Chemical Engineers》2014,60(6):2346-2353
A computational fluid dynamics model based on a finite difference solution to mass and momentum conservation equations (Navier–Stokes equations) for a liquid droplet transport between two porous or nonporous contacting surfaces (CSs) is developed. The CS dynamic (equation of motion) and the spread of the incompressible liquid available on the primary surface for transfer are coupled with the Navier–Stokes equations. The topologies of the spread dynamic between and inside both surfaces (primary and CSs) are compared with experimental data. The amount of mass being transferred into the CS, predicted by the model, is also compared to the experimental measurements. The impact of the initial velocity on the spread topology and mass transfer into the pores is addressed. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2346–2353, 2014 相似文献
22.
Françoise Martz Laura Jaakola Riitta Julkunen-Tiitto Sari Stark 《Journal of chemical ecology》2010,36(9):1017-1028
Bilberry is a characteristic field layer species in the boreal forests and is an important forage plant for herbivores of
the North European ecosystem. Bilberry leaves contain high levels of phenolic compounds, especially hydroxycinnamic acids,
flavonols, catechins, and proanthocyanidins. We investigated the phenolic composition of bilberry leaves in two studies, one
following foliar development in forest and open areas, and the other along a wide geographical gradient from south to north
boreal forests in Finland. An analysis of bilberry leaves collected in open and forest areas showed that major phenolic changes
appeared in the first stages of leaf development, but, most importantly, synthesis and accumulation of flavonoids was delayed
in the forest compared to the high light sites. Sampling along a geographical gradient in the boreal zone indicated that leaves
from higher latitudes and higher altitudes had greater soluble phenolic and flavonol levels, higher antioxidant capacity,
and lower contents of chlorogenic acid derivatives. The ecological significance of the results is discussed. 相似文献
23.
In this article, a new computational approach is investigated to predict the crack propagation inside some smart structures equipped with surface-bonded piezoelectric layers; meanwhile, the electromechanical coupling is exploited. The current industrial need of analyzing rather irregular geometries motivates resorting to a numerical approach. Therefore, the finite element method (FEM) is used to predict both the fracture behavior and the coupled response of piezoelectric material through a suitable interoperation of the two computational environments, available in some commercial code like the ABAQUS©. The two solutions are then coupled by means of a subroutine, in this case operated through the ISIGHT© tool. After a preliminary analysis and a validation, results of some numerical simulations are shown to highlight some significant peculiarities of the coupled behavior of the piezoelectric material. 相似文献
24.
Comparison of the bone modeling effects caused by curved and straight nickel–titanium intramedullary nails 总被引:1,自引:0,他引:1
Kujala S Tuukkanen J Jämsä T Danilov A Pramila A Ryhänen J 《Journal of materials science. Materials in medicine》2002,13(12):1157-1161
Nitinol (NiTi) shape memory metal alloy makes it possible to prepare functional implants. A curved intramedullary NiTi nail has been shown to cause bending of the bone, bone thickening, increase in cortical area, and reduction in bone longitudinal growth. The purpose of the present study was to find out whether these changes are caused by the bending force of the curved nail or by the intramedullary nailing itself. Pre-shaped intramedullary NiTi nails were implanted in the cooled martensitic form into the medullary cavity of the right femur in 12 rats, where they started to restore their austenitic form, causing a bending force. Straight nails were used as controls in another 12 rats. After 12 weeks, the operated femurs were compared with their non-operated contralateral counterparts and the differences were compared between the groups. Anteroposterior radiographs demonstrated bone bowing only in the curved nail group. Retardation of longitudinal growth was observed in both groups, showing that the growth effect seems to be due to the intramedullary nailing itself. Increase in bone cross-sectional area and cortical thickness were found in both groups. However, this increase was more evident with the curved nail, indicating that the bending force of the functional nail seems to induce these changes. 相似文献
25.
B Splavski G Sari? D Vrankovi? K Glavina B Mursi? G Blagus 《Canadian Metallurgical Quarterly》1998,117(6-7):360-363
Twenty-two patients with spinal injury were evaluated by plain radiography immediately after hospital admission. In 14 patients whose condition was stable, we performed computed tomography (CT) scanning through the involved segments. To provide better planning before neurosurgical management, we divided the vertebral column in thirds. According to this division, we concluded that these injuries are mostly extensive, severely damaging all three thirds of the vertebral column and accompanying neural structures in the majority of cases. The information acquired by Ct concerning bony fragments, bone destruction, dural tear, spinal cord and nerve root compression, and neural damage directly influenced the surgical management. All patients except one underwent surgery while associated injuries of other organs were given priority in management. Injuries of the thoracic and the lumbar spine were the most common ones, frequently found in association with lesions of nearby organs. Penetrating injuries with a dural lesion were present in the majority of cases, while spinal cord injury was obvious in some. They were all well visualized using spinal CT scanning. Our view is that the role of CT is essential in guiding surgical management of war missile injuries to the spine. 相似文献
26.
C Moali JL Boucher MA Sari DJ Stuehr D Mansuy 《Canadian Metallurgical Quarterly》1998,37(29):10453-10460
A detailed comparison of the oxidation of five compounds closely related to L-arginine (Arg) by purified recombinant neuronal and macrophage NO synthases (NOS I and NOS II) was performed. Homo-L-arginine (homo-Arg) is oxidized by both NOSs in the presence of NADPH with major formation of NO and homo-L-citrulline, with a molar ratio of close to 1, and minor formation of N omega-hydroxyhomo-L-arginine (homo-NOHA). Oxidation of homo-NOHA by the two NOSs also leads to NO and homocitrulline in a 1:1 molar ratio. On the contrary, N omega-hydroxynor-L-arginine (nor-NOHA) is a very poor substrate of NOS I and II, which fails to produce significant amounts of nitrite. The catalytic efficiency of both NOSs markedly decreases in the order Arg > NOHA > homo-Arg > homo-NOHA, as shown by the 20- and 10-fold decrease of kcat/Km observed for NOS I and NOS II, respectively, when comparing Arg to homo-NOHA. The greater loss of catalytic efficiency for homo-Arg, when compared to that for Arg, appears to occur at the first step (N-hydroxylation) of the reaction. In that regard, it is noteworthy that the Vm values for NOHA and homo-NOHA oxidation are very similar (about 1 and 2 micromol of NO min-1 mg of protein-1 for NOS I and II, respectively). In fact, lengthening of the Arg chain by one CH2 leads not only to markedly decreased kcat/Km but also to clear disturbances in NOS functioning. This is shown by a greater accumulation of the N omega-hydroxyguanidine intermediate (homo-NOHA:homocitrulline ratio between 0.2 and 0.4) and an increased consumption of NADPH for NO formation (between 2.0 and 2.6 mol of NADPH consumed for the formation of 1 mol of NO in the case of homo-Arg, instead of 1.5 mol in the case of Arg). Most of the above results could be interpreted by comparing the possible positionings of the various substrates relative to the two NOS active oxygen species which are believed to be responsible for the two steps of the reaction. 相似文献
27.
The first part of the review describes events and newly acquired knowledge that anticipated the making of the HEAL project and its preparatory phase. The pilot study relied on the belief that the total exposure assessment should take into account different pollutants and their relative contribution in the human intake from different environmental media such as air, drinking water, food chain, and soil. The pilot study included exposure assessment to lead and cadmium, nitrogen dioxide, hexachlorobenzene, and DDT-complex. Concurrently, another study on indoor air quality in Kenya and Gambia took place. In its second phase, the project evaluated the actual trends and outlined potential future directions. It was decided that the project should focus on the promotion of exposure studies, particularly in developing countries, and that it should establish a closer relation with health risk assessment and environmental epidemiology. The last part of the review describes the participation of the Institute for Medical Research and Occupational Health in Zagreb, Croatia in the project and in related research activities performed after the pilot phase. 相似文献
28.
Hanna Tölli Sauli Kujala Katri Levonen Timo Jämsä Pekka Jalovaara 《Journal of materials science. Materials in medicine》2010,21(5):1677-1684
Bioactive glasses have been developed as scaffolds for bone tissue engineering but combination with reindeer bone protein extract has not been evaluated. We investigated the effects of bone protein extract implants (5–40 mg dosages) with bioglass (BG) carrier on the healing of rat femur defects. Bioglass implants and untreated defects served as controls. All doses of extract increased bone formation compared with the control groups, and bone union was enhanced with doses of 10 mg or more. In comparison with untreated defect, mean cross-sectional bone area at the defect site was greater when implants with BG + 15 mg of extract or bioglass alone were used, bone density at the defect site was higher in all bioglass groups with and without bone extract, and the BG + 15 mg extract dosage marginally increased bone torsional stiffness in mechanical testing. Bioglass performed well as a carrier candidate for reindeer bone protein extract. 相似文献
29.
This paper investigates the sensitivity of several multiple-access techniques to narrow-band interference. The analysis covers time-division multiple access (TDMA), code-division multiple access (CDMA), and orthogonal frequency-division multiple access (OFDMA). The study is carried out under the assumption that all the considered multiple-access systems occupy the same total bandwidth, and the bit rates of all active users are identical. A major finding of this study is that CDMA with pseudonoise spreading sequences is more sensitive to narrow-band interference than TDMA. We point out that the signal-to-jammer power ratio at the decision device input is in fact identical for both multiple-access techniques, but the amplitude distribution of the jammer term at the threshold detector input is more favorable to TDMA, which turns out to be more robust in terms of bit-error rate. Another finding is that in terms of sensitivity to narrow-band interference, orthogonal CDMA (OCDMA) is closer to TDMA than to CDMA with pseudonoise sequences, because the degradation is not the same for all users. Finally, we discuss the relationship of OCDMA and TDMA and highlight the superiority, in terms of capacity over the narrow-band interference channel, of TDMA to the other multiple-access techniques considered in this paper 相似文献
30.
In this study, polyindole (PIN) and polyindole/kaolinite (PIN/KAO) composite were synthesized by free radical polymerization using FeCl3 as an initiator. Average particle sizes (d50) of PIN and PIN/KAO composite were determined by dynamic light scattering (DLS) as 7.2 and 6.2 μm, respectively. The samples were characterized by FTIR, elemental analysis, DSC/TGA and SEM measurements. Suspensions of KAO, PIN, and PIN/KAO composite were prepared in silicone oil (SO) and the sedimentation stabilities were determined. Electrorheological (ER) properties of these suspensions were studied as a function of dispersed phase concentration, shear rate, shear stress, and temperature; and yield stresses and excess shear stresses determined. Further, dielectric properties of KAO, PIN, and PIN/KAO composite were investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献