全文获取类型
收费全文 | 2780篇 |
免费 | 38篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 19篇 |
化学工业 | 431篇 |
金属工艺 | 22篇 |
机械仪表 | 36篇 |
建筑科学 | 81篇 |
矿业工程 | 11篇 |
能源动力 | 25篇 |
轻工业 | 220篇 |
水利工程 | 12篇 |
石油天然气 | 4篇 |
无线电 | 280篇 |
一般工业技术 | 229篇 |
冶金工业 | 1191篇 |
原子能技术 | 21篇 |
自动化技术 | 238篇 |
出版年
2022年 | 11篇 |
2021年 | 26篇 |
2020年 | 16篇 |
2019年 | 19篇 |
2018年 | 24篇 |
2017年 | 16篇 |
2016年 | 15篇 |
2015年 | 27篇 |
2014年 | 30篇 |
2013年 | 94篇 |
2012年 | 43篇 |
2011年 | 75篇 |
2010年 | 55篇 |
2009年 | 76篇 |
2008年 | 66篇 |
2007年 | 88篇 |
2006年 | 60篇 |
2005年 | 59篇 |
2004年 | 55篇 |
2003年 | 56篇 |
2002年 | 56篇 |
2001年 | 40篇 |
2000年 | 43篇 |
1999年 | 64篇 |
1998年 | 345篇 |
1997年 | 230篇 |
1996年 | 151篇 |
1995年 | 89篇 |
1994年 | 64篇 |
1993年 | 87篇 |
1992年 | 50篇 |
1991年 | 49篇 |
1990年 | 39篇 |
1989年 | 29篇 |
1988年 | 34篇 |
1987年 | 44篇 |
1986年 | 32篇 |
1985年 | 27篇 |
1984年 | 26篇 |
1983年 | 28篇 |
1982年 | 20篇 |
1981年 | 37篇 |
1980年 | 28篇 |
1979年 | 16篇 |
1978年 | 20篇 |
1977年 | 57篇 |
1976年 | 75篇 |
1975年 | 28篇 |
1974年 | 13篇 |
1973年 | 17篇 |
排序方式: 共有2820条查询结果,搜索用时 15 毫秒
101.
Oulad Haj Khadija Schneider Stéphanie Maire Gilbert Zyade Souad Ziyad Mahfoud Garin François 《Topics in Catalysis》2001,16(1-4):205-208
To better understand N2 formation in the selective catalytic reduction of NO
x
by propene under oxidative atmosphere, we studied the catalytic behavior of bimetallics. Surface segregation phenomena may provoke geometric and electronic modifications of the catalytic active sites. To explain our results we invoked: (i) the facile way to oxidize the bimetallic aggregates, (ii) the presence of atoms with low coordination number able to be oxidized first and (iii) an eventual formation of like vic-diNO
x
species on such bimetallics leading to N2 formation. 相似文献
102.
103.
William J. R. Gilbert Stephen J. Johnson Jyun‐Syung Tsau Jenn‐Tai Liang Aaron M. Scurto 《应用聚合物科学杂志》2017,134(10)
Polyacrylamides are often used in water‐based hydraulic fracturing for natural gas and oil production. However, residual polymer remaining in the fractured rock can limit production. A novel approach for degrading partially hydrolyzed polyacrylamide (HPAM) was investigated using hydrogen peroxide and horseradish peroxidase (HRP). This sustainable HRP/H2O2 system degraded the polymer in solution, reducing its viscosity in both pure water and brine solutions. Molecular weight measurements confirmed that the viscosity reduction was due to a significant degradation of the polymer backbone and not primarily by other mechanisms such as amide hydrolysis or rearrangement, and so forth. The reduction in viscosity and molecular weight was first order with respect to H2O2 concentration. The kinetics of viscosity reduction and molecular weight are closely correlated which would allow the quicker and simpler viscosity method to help engineer future processes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44560. 相似文献
104.
Ronald G. Pinnick Steven C. Hill Paul Nachman J. David Pendleton Gilbert L. Fernandez Michael W. Mayo 《Aerosol science and technology》2013,47(4):653-664
We have constructed a laser-based particle counter that detects the fluorescence, as well as the elastic scattering, from individual airborne particles as they traverse a laser beam. This fluorescence particle counter (FPC) can detect fluorescence from μm-sized Bacillus subtilis spore agglomerates when illuminated with intense light at 488 nm from an argon ion laser, either ~ 0.7 kW cm?2 extracavity or ~ 50 kW cm?2 intracavity. We suspect that flavins in the spores are the molecules primarily responsible for the fluorescence, because the peak fluorescence emission of the biological materials at this excitation wavelength is in the range 530–550 nm, which is characteristic of flavins. Fluorescence from kaolin, hematite, and polystyrene particles was not detectable; the lack of fluorescence indicates that the FPC may be able to differentiate between biological and nonbiological aerosols. The FPC samples aerosol-laden air at a rate of ~ 1 mL s?1, and is capable of measuring aerosol concentrations up to several thousand per milliliter. The FPC may be helpful in detecting and characterizing airborne bacteria and other airborne particles of biological origin. 相似文献
105.
Gilbert C. Walker Yujie Sun Senli Guo John A. Finlay Maureen E. Callow James A. Callow 《The Journal of Adhesion》2013,89(10-11):1101-1118
The mechanical properties of the adhesive produced by spores of the green, marine, fouling alga Ulva linza are reported. Atomic force microscopy studies were performed and nanoindentation data were analyzed using a model for an asymmetric indenter. Freshly secreted adhesive is characterized by multiple layers. We found that the modulus of the outer ~600-nm thick layer was about 0.2 ± 0.1 MPa, whereas the modulus of the inner layer was about 3 ± 1 MPa. Older adhesive showed the formation of a “crust” of harder material with a yield strength of ~20 MPa at a loading rate of 2.5 × 10?6 N · s?1. Mechanical properties under tension are also described, and extension profiles that showed either constant or nonlinear force changes with tip-sample separation were observed. Models for both kinds of behavior are described. The work of adhesion between poly-dimethylsiloxane (PDMS)-coated AFM tips and the adhesive was determined to be less than 1.5 mJ · m?2. 相似文献
106.
Oxygen Vacancy Relaxation and Domain Wall Hysteresis Motion in Cobalt-Doped Barium Titanate Ceramics
Bo Lin Cheng Tim W. Button Maurice Gabbay Gilbert Fantozzi Mario Maglione 《Journal of the American Ceramic Society》2005,88(4):907-911
Mechanical and dielectric loss measurements were carried out in the BaTiO3 ceramics doped with Co at frequencies between 0.01 Hz and 1 MHz as a function of temperature from −150° to 150°C. The relaxation peak observed in the ferroelectric phase with an activation energy of 0.27 eV is assumed to be related to the motion of oxygen vacancies. This peak could be because of the reorientation of an electrical dipole made of oxygen vacancies and Co3+ ions in the lattice. Furthermore, another loss peak located just below the Curie temperature T c could be interpreted as hysteretic motion of the domain walls in a regime where the domain wall density is changing. 相似文献
107.
Laura Montanaro Christophe Perrot Claude Esnouf Gilbert Thollet Gilbert Fantozzi Alfredo Negro 《Journal of the American Ceramic Society》2000,83(1):189-96
The sinterability of two industrial mullite powders, in the presence of MgO as a sintering aid, was investigated. A glassy phase, which was generated during preparation, was present in both powders; this glassy phase had a strong influence on sintering, depending on its content, composition, and spatial distribution. MgO promoted sintering in the presence of a liquid phase, both in the as-received materials and in samples washed with HF, in which most of the pre-existing glassy phase was eliminated. Investigations using transmission electron microscopy, coupled with energy-dispersive spectroscopy, as well as dilatometric measurements and X-ray diffraction data, on washed and unwashed materials and on quenched and slow-cooled samples allowed a better understanding of the influence of MgO and the glassy phase on the sintering behavior and the formation of new phases. Most of the phases, in fact, can be explained by using the MgO–Al2 O3 –SiO2 phase diagram, even in such complex systems. 相似文献
108.
Stephen Patterson Dr. Deuan C. Jones Dr. Emma J. Shanks Dr. Julie A. Frearson Prof. Ian H. Gilbert Prof. Paul G. Wyatt Prof. Alan H. Fairlamb Prof. 《ChemMedChem》2009,4(8):1341-1353
Thirty two analogues of phencyclidine were synthesised and tested as inhibitors of trypanothione reductase (TryR), a potential drug target in trypanosome and leishmania parasites. The lead compound BTCP ( 1 , 1‐(1‐benzo[b]thiophen‐2‐yl‐cyclohexyl) piperidine) was found to be a competitive inhibitor of the enzyme (Ki=1 μM ) and biologically active against bloodstream T. brucei (EC50=10 μM ), but with poor selectivity against mammalian MRC5 cells (EC50=29 μM ). Analogues with improved enzymatic and biological activity were obtained. The structure–activity relationships of this novel series are discussed. 相似文献
109.
110.
Gilbert Audira Petrus Siregar Kelvin H.-C. Chen Marri Jmelou M. Roldan Jong-Chin Huang Hong-Thih Lai Chung-Der Hsiao 《International journal of molecular sciences》2021,22(11)
Recently, medaka has been used as a model organism in various research fields. However, even though it possesses several advantages over zebrafish, fewer studies were done in medaka compared to zebrafish, especially with regard to its behavior. Thus, to provide more information regarding its behavior and to demonstrate the behavioral differences between several species of medaka, we compared the behavioral performance and biomarker expression in the brain between four medaka fishes, Oryzias latipes, Oryzias dancena, Oryzias woworae, and Oryzias sinensis. We found that each medaka species explicitly exhibited different behaviors to each other, which might be related to the different basal levels of several biomarkers. Furthermore, by phenomics and genomic-based clustering, the differences between these medaka fishes were further investigated. Here, the phenomic-based clustering was based on the behavior results, while the genomic-based clustering was based on the sequence of the nd2 gene. As we expected, both clusterings showed some resemblances to each other in terms of the interspecies relationship between medaka and zebrafish. However, this similarity was not displayed by both clusterings in the medaka interspecies comparisons. Therefore, these results suggest a re-interpretation of several prior studies in comparative biology. We hope that these results contribute to the growing database of medaka fish phenotypes and provide one of the foundations for future phenomics studies of medaka fish. 相似文献