全文获取类型
收费全文 | 11976篇 |
免费 | 1002篇 |
国内免费 | 700篇 |
专业分类
电工技术 | 1006篇 |
综合类 | 991篇 |
化学工业 | 1616篇 |
金属工艺 | 1049篇 |
机械仪表 | 2336篇 |
建筑科学 | 673篇 |
矿业工程 | 327篇 |
能源动力 | 466篇 |
轻工业 | 702篇 |
水利工程 | 230篇 |
石油天然气 | 343篇 |
武器工业 | 138篇 |
无线电 | 982篇 |
一般工业技术 | 1801篇 |
冶金工业 | 460篇 |
原子能技术 | 80篇 |
自动化技术 | 478篇 |
出版年
2024年 | 81篇 |
2023年 | 200篇 |
2022年 | 322篇 |
2021年 | 355篇 |
2020年 | 448篇 |
2019年 | 343篇 |
2018年 | 355篇 |
2017年 | 415篇 |
2016年 | 426篇 |
2015年 | 473篇 |
2014年 | 717篇 |
2013年 | 883篇 |
2012年 | 767篇 |
2011年 | 837篇 |
2010年 | 583篇 |
2009年 | 658篇 |
2008年 | 597篇 |
2007年 | 794篇 |
2006年 | 717篇 |
2005年 | 569篇 |
2004年 | 476篇 |
2003年 | 418篇 |
2002年 | 357篇 |
2001年 | 306篇 |
2000年 | 251篇 |
1999年 | 199篇 |
1998年 | 217篇 |
1997年 | 183篇 |
1996年 | 154篇 |
1995年 | 119篇 |
1994年 | 101篇 |
1993年 | 64篇 |
1992年 | 68篇 |
1991年 | 48篇 |
1990年 | 42篇 |
1989年 | 26篇 |
1988年 | 24篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1966年 | 2篇 |
1965年 | 1篇 |
1959年 | 3篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
71.
酸化水解-活性污泥-生物接触氧化工艺处理有机污水 总被引:2,自引:0,他引:2
介绍了采用酸化水解——活性污泥——生物接触氧化工艺处理含有山梨醇、甘露醇、蔗糖、醋酸乙烯、甲基纤维素的有机污水。该工艺具有出水水质稳定,操作简单、管理方便,能耗低等优点,是处理该类有机污水的有效方法。 相似文献
72.
Joon‐Seop Kim Min‐Chul Hong Yeon Hwa Nah Yeonhee Lee Seunghee Han Hyun Eui Lim 《应用聚合物科学杂志》2002,83(11):2500-2504
The wetting properties of polystyrene‐based ionomers treated with plasma source ion implantation (PSII) were investigated by the measurement of water contact angles. When sulfonated ionomers were aged for a few days, the hydrophobic recovery for the ionomers became much slower than that for the nonionic polymers. However, when the samples were aged over 20 days, the water contact angle of the ionomers converged with that of the nonionic polymer. Thus, it was concluded that the ionic interaction between the ionic groups and the presence of ionic groups together resulted in the slow hydrophobic recovery and that the aging effect was significant for the ionomers. For the methacrylate ionomer of low ion content, on the other hand, it was found that the PSII treatment produced only a small change in hydrophobic recovery behavior. Thus, it was suggested that the low ionic content coupled with the small size of the ionic unit might cause changes only of a very insignificant degree in hydrophobic recovery behavior. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2500–2504, 2002 相似文献
73.
In the field of biomaterials and biomedical devices, surface activation has been focused on creating functional groups capable of preferential adsorption of biologically active species (proteins, enzymes, cells, drugs, etc.). In this way an interface can be created between the synthetic material and the biological medium, with the aim of increasing the compatibility of the implant with the human organism. In our experiments a dielectric barrier discharge (DBD), in helium at atmospheric pressure, was used as the source of energy capable of creating active centers that render the functionalized surface favorable to immobilization of biological molecules. Retention of immunoglobulin (IgG) and heparin biomolecules on polyamide‐6 (PA‐6) surfaces after treatment by the DBD was analyzed by atomic force microscopy, adhesion evaluation, and measurement of the contact angle titration in order to assess this incorporation on the treated surfaces. The marked adsorption of the biomolecules on the active sites created by DBD on the exposed surfaces also was related to a complex set of processes, such as enhanced roughness, increased surface wettability, and modified distribution of cationic and anionic groups on the treated surfaces. All these factors could promote interfacial interactions between the specific groups of the biomolecules existing in the biological medium and the type of cationic and/or anionic groups present on the surface. The efficiency of the DBD treatment showed that the DBD technique is useful for preactivation of the polymer surface for immobilization of other biologically active species (such as drugs and enzymes). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1985–1990, 2003 相似文献
74.
Bhuvanesh Gupta Jns Hilborn Christopher Plummer Isabelle Bisson Peter Frey 《应用聚合物科学杂志》2002,85(9):1874-1880
Graft polymerization of acrylic acid onto plasma‐treated poly(ethylene terephthalate) (PET) films was used to prepare surfaces suitable for collagen immobilization by dip‐coating. Such surfaces could be used as matrices for smooth muscle cell cultures in tissue engineering. Contact angle measurements showed that plasma‐treated and grafted PET films undergo considerable surface reorganization during storage under ambient conditions. However, after collagen immobilization the contact angle remained relatively stable. The amount of collagen initially attached to the film surface increased with increasing poly(acrylic acid) graft density, but subsequent washing in water led to significant collagen loss. This loss could nevertheless be substantially reduced by thermal crosslinking of the collagen in the range 110–130 °C. Atomic force microscopy (AFM) observations suggested that the washed crosslinked collagen has a very similar structure to that of the un‐crosslinked collagen. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1874–1880, 2002 相似文献
75.
A. Venkateswara Rao Ravindra R. Kalesh D.P. Amalnerkar T. Seth 《Journal of Porous Materials》2003,10(1):23-29
The experimental results on the effect of adding trimethylethoxysilane (TMES) as a co-precursor on the hydrophobicity and physical properties of tetraethoxysilane (TEOS) based silica aerogels, are reported. The molar ratio of TEOS, ethanol (EtOH), water (0.001 M oxalic acid catalyst) was kept constant at 1:5:7 respectively, while the molar ratio of TMES/TEOS (A) was varied from 0 to 0.6. It has been observed that as the A value increases, the gelation time increases. The hydrophobicity was tested by measuring the contact angle, and the surface chemical modification was confirmed by the FTIR spectroscopy studies. The thermal stability of the hydrophobic aerogels was studied in the temperature range from 25 to 800°C. The hydrophobic nature of the aerogel could be maintained up to a temperature of 287°C and above this temperature the aerogels become hydrophilic. The bulk density and the optical transmittance of the aerogels have been found to decrease with increase in A value. The aerogels have been characterized by Fourier transform infrared spectroscopy (FTIR), Optical transmittance, Scanning electron microscopy (SEM), Differential thermal analysis (DTA) and Thermogravimetric analysis (TGA), and Contact angle measurements. 相似文献
76.
77.
Passing of a triangular moderate-intensity pulse through a constant discontinuity is considered. Decay of the shock wave that
passed into the second gas is analyzed. Damping of the detonation wave after burnout of the combustible mixture is discussed.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 4, pp. 102–107, July–August, 2007. 相似文献
78.
We present a simple glue method for fabricating membrane electrode assemblies (MEA) for direct methanol fuel cells (DMFC). Rather than the conventional “dry” hot-pressing method that relies solely on hot-pressing at a high pressure and temperature to form a MEA, the “wet” method developed in this work introduces a binding agent, consisting of Nafion® solution, between a polymer electrolyte membrane (PEM) and an anode/cathode. The introduced binding agent can provide a better adhesion and stronger binding force between a membrane and an electrode, thereby facilitating a better interfacial contact between the electrode and the Nafion® membrane, which has been proved by scanning electron microscopy (SEM) analyses to the cross-sectional morphology of the MEA after long-term operation. The cell performance characterization showed the MEA fabricated by the glue method was more stable in cell performance than that fabricated by the conventional hot-pressing method. Cyclic voltammetry (CV) results also demonstrated the MEA fabricated by the glue method exhibited a higher electrochemical surface area (ESA) as a result of the improved interfacial contact between the Nafion® membrane and the electrodes. Finally, the DMFC with the MEA fabricated by the glue method was characterized by the electrochemical impedance spectroscopy (EIS). 相似文献
79.
The importance of some relative surface characteristics which determines the strength of adhesive joints: specific surface of substrate , relative contact area β and specific contact area β in the adhesion interaction process were emphasised. Existing and potential methods of experimental evaluation of these characteristics were shortly analysed. The durability of the adhesive joints in water media significantly increases with growth of specific surface * of chemically treated substrate evaluated from the SEM micrographs. Specific surface calculated from the experimental data of hexane adsorption measurements for iron particles (particulate model of steel substrate) is more then ten times greater than respective * values. The relative contact area β of the Al2O3 particles (in wide range of ) with PE melt was in a roundabout way evaluated by experimental determination of the affect of on kinetic of peel strength formation of adhesive joints: Al2O3 filled PE-steel. The speculation was based on the ability of Al2O3 to adsorb low-molecular products of contact oxidation of PE which takes place in the process of formation of adhesive joints and determines their strength. The ability of sorption in its turn is proportional to efficient value of β. The availability of the Al2O3 surface was evaluated. 相似文献
80.
Based on nonlinearity contact theory and the geological structure of the Xieqiao Coal Mine in the newly developed Huainan coal field, rock movements, mining fissures and deformation of overlying strata were simulated by using the interface unit of FLAC3D to evaluate the pressure-relief gas drainage in the exploitation of super-remote protected seams. The simulation indicates that the height of the water flowing fractured zone is 54 m in the overlying strata above the protective layer. The maximum relative swelling deformation of the C 13 coal seam is 0.232%,while the mining height is 3.0 m and the distance from the B8 roof to the C13 floor is 129 m, which provides good agreement with a similar experiment and in situ results. The feasibility of exploitation of a super-remote protective coal seam and the performance of the pressure-relief gas drainage in a super-remote protected layer are evaluated by comparisons with practice projects. It demonstrates that the relieved gas in the super-remote protected layers could be better drained and it is feasible to exploit the B8 coal seam before the C13 super-remote protected coal seam. The method is applicable for the study of rock movements, mining fissures and deformation of the overburden, using the interface unit to analyze the contact problems in coal mines. 相似文献