全文获取类型
收费全文 | 2280篇 |
免费 | 105篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 17篇 |
综合类 | 3篇 |
化学工业 | 390篇 |
金属工艺 | 48篇 |
机械仪表 | 26篇 |
建筑科学 | 53篇 |
矿业工程 | 5篇 |
能源动力 | 69篇 |
轻工业 | 189篇 |
水利工程 | 7篇 |
石油天然气 | 8篇 |
无线电 | 319篇 |
一般工业技术 | 338篇 |
冶金工业 | 636篇 |
原子能技术 | 13篇 |
自动化技术 | 268篇 |
出版年
2024年 | 5篇 |
2023年 | 36篇 |
2022年 | 55篇 |
2021年 | 100篇 |
2020年 | 72篇 |
2019年 | 86篇 |
2018年 | 76篇 |
2017年 | 75篇 |
2016年 | 111篇 |
2015年 | 56篇 |
2014年 | 82篇 |
2013年 | 113篇 |
2012年 | 97篇 |
2011年 | 106篇 |
2010年 | 89篇 |
2009年 | 72篇 |
2008年 | 78篇 |
2007年 | 53篇 |
2006年 | 40篇 |
2005年 | 45篇 |
2004年 | 28篇 |
2003年 | 29篇 |
2002年 | 34篇 |
2001年 | 27篇 |
2000年 | 29篇 |
1999年 | 32篇 |
1998年 | 188篇 |
1997年 | 126篇 |
1996年 | 76篇 |
1995年 | 46篇 |
1994年 | 40篇 |
1993年 | 34篇 |
1992年 | 24篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 10篇 |
1988年 | 13篇 |
1987年 | 25篇 |
1986年 | 13篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 24篇 |
1976年 | 32篇 |
1972年 | 2篇 |
排序方式: 共有2389条查询结果,搜索用时 15 毫秒
21.
PV Kumar 《Canadian Metallurgical Quarterly》1994,38(5):702-706
From 1980 to 1992, five cases of Askin tumor were diagnosed by fine needle aspiration cytology at the Shiraz University Hospitals, Namazi, Faghihi and Beheshti, Iran. All patients were female, their ages ranging between 15 and 22 years. Three of them had a mass on the right side and two on the left side of the chest. Chest roentgenography revealed no bone involvement. Two tumors involved the lungs and pleura. Urinary catecholamine levels were within normal limits. The fine needle aspiration smears revealed many small, round malignant cells with indistinct cytoplasm, a high nuclear/cytoplasmic ratio and prominent, multiple nucleoli. Homer-Wright rosettes were seen frequently. The cells were often arranged in rows simulating rouleaux formation. They were positively stained by periodic acid-Schiff stain. The histologic sections confirmed the cytologic diagnosis of Askin tumor. Four of the patients died within 7-11 months after treatment began. 相似文献
22.
AN Reshetilov DA Efremov PV Iliasov AM Boronin NI Kukushskin RV Greene TD Leathers 《Canadian Metallurgical Quarterly》1998,13(7-8):795-799
Amperometric biosensors register oxygen depletion in response to analyte catabolism, and thus are limited by the availability of dissolved oxygen. Microbial sensors containing immobilized cells of Gluconobacter oxydans were hyperoxygenated to 400% of control levels and the effects on sensor responses to glucose were determined. Oxygenated perfluorodecalin (a completely fluorinated organic substance) was as effective in hyperoxygenation as direct sparging with O2, increasing sensor base medium oxygen concentrations from 9.3 to 37 mg/l. Hyperoxygenation enhanced maximal biosensor response amplitudes, particularly at high cell loading densities. Maximal response rates were also improved, although less dramatically. Results suggest that hyperoxygenation may be a new general approach for modulating biosensor responses. 相似文献
23.
PV Simonov 《Canadian Metallurgical Quarterly》1997,27(5):585-591
We have used a previously described model of bilateral radiation-induced lung disease in the rat (Ward et al., Radiat. Res., 136, 15-21, 1993) to study the role of hyaluronan in this process. Hyaluronan was measured in the bronchoalveolar lavage fluid, serum and lung tissue of rats after gamma irradiation or sham irradiation. Four weeks after irradiation, during peak alveolitis (12-fold increase in protein in the lavage, 7-fold increase in lavaged cells) hyaluronan was elevated 5.5-fold in serum and 1.5-fold in the bronchoalveolar lavage fluid. Histochemical staining demonstrated hyaluronan was in the intra-alveolar edema fluid but was not increased in the alveolar walls; hyaluronan, measured by high-performance liquid chromatography, also was not elevated in lavaged lung tissue. Hyaluronan was not increased in bron-choalveolar lavage fluid, serum or lung tissue during pulmonary edema (2 weeks) or fibrosis (6 to 20 weeks). The administration of methylprednisolone significantly decreased the alveolitis, including the increase in hyaluronan in the alveolar space and serum, but did not suppress fibrosis. It appears that hyaluronan is a marker of inflammation and cannot be used as a serum marker to predict the onset of radiation pneumonitis. Furthermore, an increase in interstitial hyaluronan does not appear to be a necessary precursor in the evolution of radiation fibrosis. 相似文献
24.
25.
Streit D.C. Oki A.K. Umemoto D.K. Velebir J.R. Stolt K.S. Yamada F.M. Saito Y. Hafizi M.E. Bui S. Tran L.T. 《Electron Device Letters, IEEE》1991,12(9):471-473
The authors have developed a modified MBE growth process to produce high-gain n-p-n GaAs-AlGaAs heterojunction bipolar transistors (HBTs) with a mean time to failure (MTTF) of 1.5×108 h at 125°C. Beryllium incorporation and diffusion are controlled through a combination of reduced substrate temperature and increased As/Ga flux ratio during MBE growth, resulting in extremely stable HBT profiles. The authors also demonstrate graded InGaAs surface layers with nonalloyed refractory metal contacts that significantly improve ohmic reliability compared to alloyed AuGe contacts. The ability to produce robust HBTs by MBE is critically important to this technology 相似文献
26.
JR Kerr D Kane B Crowley N Leonard S O''Briain PV Coyle F Mulcahy 《Canadian Metallurgical Quarterly》1997,8(3):184-186
We report a 16-year-old boy, born to consanguineous parents, with mental retardation, gait disturbances and dysarthria; brain magnetic resonance showed features consistent with rhombencephalosynapsis. This condition is characterised by a hypoplastic single-lobed cerebellum. The interest of this case is the presence of common ancestors, pointing to an autosomal recessive inheritance of the malformation. 相似文献
27.
In the research presented here, we explore the use of a low‐energy plasma to deposit thin silicone polymer films using tetramethyldisiloxane (TMDSO) (H(CH3)2? Si? O? Si? (CH3)2H) on the surface of an ethylene propylene diene elastomeric terpolymer (EPDM) in order to enhance the surface hydrophobicity, lower the surface energy and improve the degradation/wear characteristics. The processing conditions were varied over a wide range of treatment times and discharge powers to control the physical characteristics, thickness, morphology and chemical structure of the plasma polymer films. Scanning electron microscopy (SEM) shows that pore‐free homogeneous plasma polymer thin films of granular microstructure composed of small grains are formed and that the morphology of the granular structure depends on the plasma processing conditions, such as plasma power and time of deposition. The thicknesses of the coatings were determined using SEM, which confirmed that the thicknesses of the deposited plasma‐polymer films could be precisely controlled by the plasma parameters. The kinetics of plasma‐polymer film deposition were also evaluated. Contact angle measurements of different solvent droplets on the coatings were used to calculate the surface energies of the coatings. These coatings appeared to be hydrophobic and had low surface energies. X‐ray photoelectron spectroscopy (XPS) and photoacoustic Fourier‐transform infrared (PA‐FT‐IR) spectroscopy were used to investigate the detailed chemical structures of the deposited films. The optimum plasma processing conditions to achieve the desired thin plasma polymer coatings are discussed in the light of the chemistry that takes place at the interfaces. Copyright © 2004 Society of Chemical Industry 相似文献
28.
Rami Dana Irina Kiruschev Phong Dinh Tran Pascal Doppelt Yishay Manassen 《Israel journal of chemistry》2008,48(2):87-97
A new design for a dual-tip scanning tunneling microscope (STM) is presented. The design is a variation on the mechanically controllable break-junction with two electron beam-induced deposition nano-tips. The new design enables one to scan surfaces simultaneously with two probes having a nano-gap separation. By collecting the lateral current flowing between the tips, the transconductance map can then be compared with the STM images for local characterizations of the electron transport. Since the lateral beam carries the property of the density of states of the surface at momentum space, the dispersion of the electronic structure should give an orientation and position dependence of the local transconductance current. In addition, the reduced terminal separation, on the order of the characteristic mesoscopic length scales, is likely to be sensitive to a variety of typically observed interactions and interference effects. 相似文献
29.
RR Edelman H Hatabu E Tadamura W Li PV Prasad 《Canadian Metallurgical Quarterly》1996,2(11):1236-1239
The imaging of regional ventilation in the lungs is essential for the evaluation of a variety of pathological conditions, such as emphysema, pneumonia and pulmonary embolism. We propose a novel approach for ventilation scanning, using magnetic resonance imaging (MRI) and inhaled molecular oxygen as a contrast agent, that directly depicts transfer of oxygen across the alveolus into the pulmonary vasculature. Molecular oxygen is only weakly paramagnetic but produces substantial signal changes in the lungs because of their large surface area. Ventilation defects were shown in a patient with bullous emphysema, and ventilation-perfusion mismatches were shown in two patients with pulmonary embolism. 相似文献
30.
Molecular models of an oligodeoxynucleotide-peptide conjugate complexed to an RNA hairpin loop were constructed to assess the effect of stereoisomerism at the point of attachment of the peptide to the oligodeoxynucleotide on the affinity of the conjugate for an RNA target. The peptide portion of the oligodeoxynucleotide-peptide conjugate, (L-lysine)8, was covalently attached to the N-allyl group of (D)- or (L)-aspartic alcohol that was incorporated into the interior of an antisense oligodeoxynucleotide. The stereocenter in the oligodeoxynucleotide interior originates from either (D)- or (L)-aspartic alcohol. The oligodeoxynucleotide portion of the oligodeoxynucleotide-peptide conjugate forms Watson-Crick base pairs with the single-stranded RNA that flanks the RNA hairpin loop. The positively charged peptide makes specific electrostatic contacts with the negatively charged phosphate backbone of the RNA hairpin loop when attached to the N-allyl of (D)-aspartic alcohol but does not have the proper orientation to make these electrostatic contacts when attached to the N-allyl of (L)-aspartic alcohol. This modelling study emphasizes the importance of stereocontrol at the point of branching in synthesizing oligodeoxynucleotide-peptide conjugates for binding of RNA hairpin loops. 相似文献