全文获取类型
收费全文 | 1410篇 |
免费 | 24篇 |
专业分类
电工技术 | 17篇 |
化学工业 | 199篇 |
金属工艺 | 70篇 |
机械仪表 | 19篇 |
建筑科学 | 61篇 |
能源动力 | 44篇 |
轻工业 | 126篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 147篇 |
一般工业技术 | 227篇 |
冶金工业 | 350篇 |
原子能技术 | 5篇 |
自动化技术 | 161篇 |
出版年
2023年 | 5篇 |
2022年 | 9篇 |
2021年 | 18篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 14篇 |
2017年 | 22篇 |
2016年 | 20篇 |
2015年 | 32篇 |
2014年 | 30篇 |
2013年 | 55篇 |
2012年 | 42篇 |
2011年 | 66篇 |
2010年 | 51篇 |
2009年 | 52篇 |
2008年 | 55篇 |
2007年 | 58篇 |
2006年 | 40篇 |
2005年 | 46篇 |
2004年 | 42篇 |
2003年 | 43篇 |
2002年 | 43篇 |
2001年 | 30篇 |
2000年 | 26篇 |
1999年 | 46篇 |
1998年 | 107篇 |
1997年 | 62篇 |
1996年 | 59篇 |
1995年 | 51篇 |
1994年 | 59篇 |
1993年 | 35篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 23篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 18篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1971年 | 3篇 |
排序方式: 共有1434条查询结果,搜索用时 46 毫秒
101.
Kristofer Fredin Erik M.J. Johansson Tobias Blom Maria Hedlund Stefan Plogmaker Hans Siegbahn Klaus Leifer Håkan Rensmo 《Synthetic Metals》2009,159(1-2):166-170
We describe a method to fill thin films of nanoporous TiO2 with solid organic hole-conducting materials and demonstrate the procedure specifically for use in the preparation of dye-sensitized solar cells. Cross-sections of the films were investigated by scanning electron microscopy and it was observed that a hot molten organic material fills pores that are 10 μm below the surface of the film. We characterized the incident photon to current conversion efficiency properties of the solid TiO2/organic dye/organic hole-conductor heterojunctions and the spectra show that the dye is still active after the melting process. 相似文献
102.
The load sharing between phases and the evolution of micro- and macrostresses during cyclic loading has been investigated
in a 1.5-mm cold-rolled sheet of the duplex stainless steel SAF 2304. X-ray diffraction (XRD) stress analysis and transmission
electron microscopy (TEM) show that even if the hardness and yield strength are higher in the austenitic phase, more plastic
deformation will occur in this phase due to the residual microstresses present in the material. The origin of the microstresses
is the difference in coefficients of thermal expansion between the two phases, which leads to tensile microstresses in the
austenite and compressive microstresses in the ferrite. The microstresses were also found to increase from 50 to 140 MPa in
the austenite during the first 100 cycles when cycled in tension fatigue with a maximum load of 500 MPa. The cyclic loading
response of the material was, thus, mainly controlled by the plastic properties of the austenitic phase. It was also found
that initial compressive macrostresses on the surface increased from −40 to 50 MPa during the first 103 cycles. After the initial increase of microstresses and macrostresses, no fading of residual stresses was found to occur
for the following cycles. A good correlation was found between the internal stress state and the microstructure evolution.
The change in texture during cyclic fatigue showed a sharpening of the deformation texture in the ferritic phase, while no
significant changes were found in the austenitic phase. 相似文献
103.
104.
F Nayeri R Cameron E Chryssanthou L Johansson C S?derstr?m 《Canadian Metallurgical Quarterly》1997,29(6):635-638
A 48-year-old woman with no cardiovascular risk factors was admitted to the hospital because of acute dyspnea. At 27-year-old, she developed Hodgkin's disease, that was successfully treated with splenectomy, combined chemotherapy (nitrogen mustard, vincristine, procarbazine, prednisone-MOPP regimen) and radiotherapy (4500 rads). At 43-year-old the lymphoma relapsed and she had further chemotherapy with doxorubicin, bleomycin, vinblastina and dacarbazine. After this treatment, she had an episode of pulmonary edema, attributed to doxorubicin acute cardiotoxicity. She responded to digitalis and diuretics and was discharged with an electrocardiogram (ECG) showing left bundle branch block and a normal echocardiogram. The patient enjoyed good health for several years and 4 months before the present admission the ECG and echocardiogram were unchanged. On this admission there were signs of left ventricular failure with acute pulmonary edema, and a new soft apical murmur (3-4 Levine). The patient required endotracheal intubation and high doses of diuretics, digitalis and vasodilators. The cardiac enzymes were negative, the serial ECGs confirmed left bundle branch block, while the echocardiogram showed moderate to severe mitral regurgitation, akinesia of the interventricular septum and inferior wall with dilation of the left ventricle. A previous silent myocardial infarction was suspected. After recovery, she underwent cardiac catheterization confirming akinesia of the interventricular septum and inferior wall with moderate mitral regurgitation, while coronary angiography showed a critical ostial stenosis of the right coronary artery. In view of a dipyridamole-thallium scan negative for myocardial viability, reperfusion was not attempted. With changes in radiotherapeutic techniques, the incidence of radiation-induced heart disease (pericarditis, myocarditis, conduction abnormalities and, rarely, occlusive coronary artery disease) is declining. Nevertheless, after irradiation of the chest and mediastinum a longterm cardiological follow-up is useful in selecting patients at higher risk of radiation-induced coronary artery disease, who will eventually require coronary angiography and reperfusion intervention. 相似文献
105.
106.
H Seeman-Lodding S H?ggmark C Jern S Jern G Johansson O Wins? B Biber 《Canadian Metallurgical Quarterly》1997,41(9):1114-1123
BACKGROUND: The key regulator of intravascular fibrinolysis, tissue-type plasminogen activator (t-PA), is released from a dynamic endothelial storage pool. The aim of the study was to investigate regional t-PA net release and uptake rates in response to infra-renal aortic cross-clamping (AXC) and declamping (DC). METHODS: Anesthetized pigs were studied during 5 min of AXC, followed by a 35-min declamping (DC) period. Arterio-venous concentration gradients of total and active t-PA, as well as respective plasma flows, were simultaneously obtained across the preportal, hepatic, coronary and pulmonary vascular beds. Plasma levels of total t-PA (ELISA with purified porcine t-PA as standard), and active t-PA (spectrophotometric functional assay) were determined. RESULTS: Prior to AXC, we found a high net release rate of total t-PA across the preportal vascular bed (1700 ng.min-1 P < 0.001), and a high hepatic net uptake (4900 ng.min-1, P < 0.001), while coronary and pulmonary t-PA net fluxes were small and variable. AXC per se did not induce significant alterations in net fluxes of t-PA. Following DC, preportal and coronary net releases of total t-PA increased (to 2900 ng.min-1 and 60 ng.min-1, respectively). Despite an increase in hepatic net uptake of total t-PA (to 6100 ng.min-1) after DC, a significant increase in hepatic venous total t-PA occurred. CONCLUSIONS: The release and uptake of t-PA is indicated to be dynamic and organ-specific. DC induces an acute profibrinolytic reaction in preportal organs. The high hepatic t-PA uptake capacity restricts preportal profibrinolytic events to affect the systemic circulation. 相似文献
107.
Heikki Kallio Saska Tuomasjukka Anu Johansson Raija Tahvonen Niina Nieminen Olli Sjvall Juha‐Pekka Kurvinen Hanna Kivini 《European Journal of Lipid Science and Technology》2005,107(2):101-106
Currant oils have special health properties due to their moderate contents of α‐linolenic, γ‐linolenic and stearidonic acids. The distribution of fatty acids (FA) in the triacylglycerols (TAG) may affect the beneficial effects. Seed oils of wild northern red currant (NRC) (Ribes spicatum L.) from Northern Finland and of wild alpine currant (AC) (R. alpinum L.) from the South‐West coast of Finland were investigated. The purified TAG were analysed by tandem mass spectrometry by applying the ammonia negative ion chemical ionisation – collision‐induced dissociation method. Molecular weight fractions rich in C18:3 FA and C18:4 FA were investigated. Of the total oil, the molecular weight species 54:7 (ACN:DB), 54:8 and 54:9 were more abundant in NRC than in AC, being 21.0%, 15.8%, 7.4% and 16.2%, 11.2%, 4.8%, respectively (p <0.05). The species 52:6 was more abundant in AC (3.1%) than in NRC (2.6%) (p <0.05). The preferential order of FA to be in the sn‐2 position in both berries was typically C18:1 > C18:2 > C18:4 > C18:3. No difference was observed between relative locations of C16:0 FA and C18:3 FA in either of the oils. Within the TAG consisting of FA combinations C18:3/C18:3/C18:1 (54:7), C18:1 was more preferentially in the sn‐2 position (p <0.05) in AC (93.2%) than in NRC (74.6%), and in the case of C18:3, the preference was vice versa. Within the molecular weight species 54:9, FA combination C18:4/C18:3/C18:2, linoleic acid preferentially occupied the secondary position (p <0.005) in both berries, and the proportion of the TAG regioisomer pair sn‐C18:3‐C18:4‐C18:2 + sn‐C18:2‐C18:4‐C18:3 was more abundant (30.2%) in NRC than in AC (15.3%). Within the TAG species 52:6, proportions of all the existing combinations, C16:0/C18:3/C18:3, C16:0/C18:4/C18:2 and C16:1/C18:3/C18:2, varied between the two berry species (p <0.005). 相似文献
108.
109.
Eva Johansson Karel Miskovsky Karl-Johan Loorents 《Journal of Materials Engineering and Performance》2009,18(3):299-304
There is a need for an effective method to estimate the quality of crushed rock aggregates and its usability in the early
stages of project planning, e.g., for road and railway constructions and quarry prospecting. The proposed method is based
on mineralogical and petrographic analyses of drill cuttings and analysis of the coarse fraction to estimate the homogeneity/heterogeneity
of the bedrock. The geological analyses are followed by an estimation of the rock materials’ mechanical properties and their
potential technical usability. Development and practical applicability (field and laboratory) of the method have been performed
and correlated to three road projects from regions of different geological and climatic zones in Sweden. The study confirms
the capability of the proposed method as a surveying tool. 相似文献
110.
Fredrik Johansson Martin Kanje Cecilia Eriksson Linsmeier Lars Wallman 《IEEE transactions on bio-medical engineering》2008,55(4):1447-1449
xonal outgrowth on smooth and porous silicon surfaces was studied in organ culture. The pore size of the silicon substrata varied between 100 and 1500 nm. We found that axons preferred to grow and elongate on porous silicon surfaces only when pores of (150-500 nm) are available. 相似文献