全文获取类型
收费全文 | 5620篇 |
免费 | 594篇 |
国内免费 | 76篇 |
专业分类
电工技术 | 114篇 |
技术理论 | 1篇 |
综合类 | 91篇 |
化学工业 | 1419篇 |
金属工艺 | 219篇 |
机械仪表 | 390篇 |
建筑科学 | 139篇 |
矿业工程 | 49篇 |
能源动力 | 301篇 |
轻工业 | 460篇 |
水利工程 | 37篇 |
石油天然气 | 120篇 |
武器工业 | 10篇 |
无线电 | 902篇 |
一般工业技术 | 1139篇 |
冶金工业 | 185篇 |
原子能技术 | 52篇 |
自动化技术 | 662篇 |
出版年
2024年 | 6篇 |
2023年 | 79篇 |
2022年 | 53篇 |
2021年 | 210篇 |
2020年 | 199篇 |
2019年 | 187篇 |
2018年 | 212篇 |
2017年 | 226篇 |
2016年 | 235篇 |
2015年 | 212篇 |
2014年 | 320篇 |
2013年 | 402篇 |
2012年 | 402篇 |
2011年 | 456篇 |
2010年 | 378篇 |
2009年 | 360篇 |
2008年 | 359篇 |
2007年 | 211篇 |
2006年 | 225篇 |
2005年 | 223篇 |
2004年 | 192篇 |
2003年 | 179篇 |
2002年 | 140篇 |
2001年 | 120篇 |
2000年 | 90篇 |
1999年 | 105篇 |
1998年 | 85篇 |
1997年 | 70篇 |
1996年 | 74篇 |
1995年 | 47篇 |
1994年 | 54篇 |
1993年 | 24篇 |
1992年 | 23篇 |
1991年 | 24篇 |
1990年 | 18篇 |
1989年 | 22篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有6290条查询结果,搜索用时 31 毫秒
991.
Hong J Ko SO Khang G Mun MS 《Journal of materials science. Materials in medicine》2008,19(7):2589-2594
Cortical bone is a composite material consisting of a porous elastic solid and viscous fluid. It is well known that the intraosseous fluid circulates as a result of a bone fluid pressure gradient in the porous space of the cortical bone. When a time-dependent mechanical load is applied to the bone, intraosseous fluid flow occurs through the interconnected pore space in the bone. Bone fluid flow leads to a strain generated streaming potential (SGP). However, there is no experimental study on the relationship between the generation of intraosseous pressure and the SGP. The purpose of this study was to obtain the relationship between SGP and intraosseous pressure generations in cortical bone. In order to understand the issue, a drained, one-dimensional experimental setup for fluid-filled cortical bone samples with four different strain rates was used to simultaneously measure the intraosseous pressure and SGP. The results revealed a significant correlation (r = 0.98, p = 0.02) between the generation of the SGP and the intraosseous pressure, which indicates that an intraosseous pressure gradient produces a SGP in cortical bone. 相似文献
992.
Preparation and lead ion removal property of hydroxyapatite/polyacrylamide composite hydrogels 总被引:3,自引:0,他引:3
We report the synthesis of hydroxyapatite/polyacrylamide (HAp/PAAm) composite hydrogels with various HAp contents by free radical polymerization and their removal capability of Pb(2+) ions in aqueous solutions with controlled initial Pb(2+) ion concentrations and pH values of 2-5. The swelling ratio of the composite gels in aqueous solutions decreases with increasing the HAp content in the gels. The composite gel with higher HAp content exhibits the higher removal capacity of Pb(2+) ions owing to the higher adsorption sites for Pb(2+) ions, but shows the slower removal rate of Pb(2+) ions due to the lower degree of swelling. The removal mechanism of Pb(2+) ion is very sensitive to the pH value in aqueous solution, although the removed amount of Pb(2+) ion is nearly same, regardless of pH values of 2-5. The removal mechanism, the dissolution of HAp in the composite gel and subsequent precipitation of hydroxypyromorphite (HPy), is dominant at lower pH 2-3, whereas the mechanism, the adsorption of Pb(2+) ions on the composite gel and following cation exchange reaction between Pb(2+) ions adsorbed and Ca(2+) of HAp, is dominant at higher pH 4-5. The equilibrium removal process of Pb(2+) ions by the composite gels at pH 5 is described well with the Langmuir isotherm model. The equilibrium removal capacities of the composite gels with 30, 50, and 70 wt.% HAp contents are evaluated to be 123, 178, and 209 mg/g, respectively. 相似文献
993.
To lower the operating temperatures in solid oxide fuel cell (SOFC) operations, anode-supported SOFC single cells with a single dip-coated interlayer were fabricated and the effect of the interlayer on the electrolyte structure and the electrical performance was investigated. For the preparation of SOFC single cells, yttria-stabilized zirconia (YSZ) electrolyte, NiO-YSZ anode, and 50% YSZ-50% strontium-doped lanthanum manganite (LSM) cathode were used. In order to characterize the cells, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were utilized and the gas (air) permeability measurements were conducted for gas tightness estimation. When the interlayer was inserted onto NiO-YSZ anode, the surface roughness of anode was diminished by about 40% and dense crack-free electrolytes were obtained. The electrical performance was enhanced remarkably and the maximum power density was 0.57W/cm(2) at 800 degrees C and 0.44W/cm(2) at 700 degrees C. On the other hand, the effect of interlayer on the gas tightness was negligible. The characterization study revealed that the enhancement in the electrical performance was mainly attributed to the increase of ion transmission area of anode/electrolyte interface and the increase of ionic conductivity of dense crack-free electrolyte layer. 相似文献
994.
The aim of the present study was to develop a biological early warning system (BEWS), equipped with six monitoring channels to individually observe the activity of Daphnia magna, using a digital 'Grid Counter', which would trigger an alarm within an appropriate time, and examine the functional performance of the newly developed BEWS for detecting unusual water quality. In order to detect the changes in the activity of D. magna, six relative activity parameter values (Z(a)) were computed from the 6 individual monitoring channels; with the activity data for D. magna calculated every 5 min. The Student's t-test was used to verify the difference between the mean value of the system in a steady state, as a control, and the exposure values during a sudden pollution event. The test results illustrate that the threshold value for the alarm can be at p=0.0093 for 3 consecutive detections. The time period, defined as the average time taken from the detection of hyper to retarded activity of the organism, for Cu concentrations of 50, 100, 200 and 400 ppb were 7.17+/-1.75, 3.94+/-2.02, 1.85+/-0.49 and 1.00+/-0.18 h, respectively. Based on the results of this study, it is proposed that p values from the t-test, with Z(a), are more accurate, stable and predictable parameters for the detection of chemical exposures than the other values, such as the swimming speed and trajectory, etc. Consequently, it would be possible to reduce the number of false alarms and achieve confidence for a system, with the ability of highly accurate detection, such as with the six-channel monitoring system developed in this study. 相似文献
995.
A suspension array for multiplexed immunoassays has been developed using shape-coded silica nanotubes (SNTs) as coding materials. Fabricated by multistep anodization template synthesis, each shape-coded SNT has several segments with different reflectance values depending on their diameters and wall thicknesses. Therefore, the code of each SNT can be "read-out" under a conventional optical microscope. The suspension array with shape-coded SNTs has shown high stability and dispersibility in aqueous buffer media and high detection sensitivity. The SNTs have not shown any visible degradation while submerged in aqueous solution for 7 months, the tubular structure and silanol groups on the inner and outer surfaces allow SNTs to disperse evenly in buffer solution, and the detection limit of an IgG protein is about 6 pM with 1.5 x 10(6) SNTs per mL. We have demonstrated the high selectivity of the SNTs suspension array for the detection of multianalytes in the multiplexed immunoassay experiments. 相似文献
996.
Hyun?Seok?HongEmail author Jun?Woong?Kim Sang?Jin?Jung Chong?Ook?Park 《Journal of Electroceramics》2005,15(2):151-157
Practical small-sized thick film CO2 sensor with self-heater was fabricated with Na β -Alumina (NBA), Na2Ti6O13-TiO2, and Na2CO3 as a solid electrolyte, reference electrode, and a sensing electrode, respectively. The measured EMF from the sensor followed the Nernstian behavior with CO2 concentration change in the range of 400 to 600∘C (350–580 mW power consumption). However, in the aspect of stability, densification of the NBA thick film and prevention of Na2CO3 evaporation were needed. In this study, an Al2O3 porous layer deposited on Na2CO3 was effective in improving the durability during operation of the sensor. It is thought that Al2O3 suppresses evaporation of Na2CO3. 相似文献
997.
998.
Park JS Oh YH Ahn SC Lee SW 《IEEE transactions on pattern analysis and machine intelligence》2005,27(5):805-811
In this paper, we propose a new method of removing glasses from a human frontal facial image. We first detect the regions occluded by the glasses and generate a natural looking facial image without glasses by recursive error compensation using PCA reconstruction. The resulting image has no trace of the glasses frame or of the reflection and shade caused by the glasses. The experimental results show that the proposed method provides an effective solution to the problem of glasses occlusion and we believe that this method can also be used to enhance the performance of face recognition systems. 相似文献
999.
Park J Ryu J Choi SK Seo E Cha JM Ryu S Kim J Kim B Lee SH 《Analytical chemistry》2005,77(20):6571-6580
We present a microfabricated hybrid biopolymer microcantilever, in which the contractile force of self-organized cardiomyocytes can be measured and studied, as a prototype for the development of cell-driven actuators. The microcantilever is made of a flexible, transparent, biocompatible poly(dimethylsiloxane) substrate, using a simple microfabrication technique. Seeding and culturing cardiomyocytes on the specific cantilever allows us to perform highly sensitive, quantitative, and noninvasive measurement of the contractile force of the self-organized cells in real time. The motions of the microcantilever showed good agreement with an analytical solution based on Stoney's equation and finite element modeling (FEM) of the hybrid system. Immunostaining of the cells on the hybrid system showed continuous high-order coalignment of actin filaments and parallel sarcomeric organization in the direction of the longitudinal axis of the microcantilever without structural constraints, such as microgrooves or lines, and proved our FEM and the synchronous contraction of cardiomyocytes. The presented device should facilitate measurement of the contractile force of self-organized cardiomyocytes on a specific area, which may help the understanding of heart failure and the design of optimal hybrid biopolymer actuators, as well as assist development of a microscale cell-driven motor system. 相似文献
1000.
A novel fusion protein system employing the substrate-binding domain (SBD) of poly(hydroxyalkanoate) (PHA) depolymerase was developed for the specific immobilization of proteins on PHA microbeads, and was consequently used for immunoassays. The enhanced green fluorescent protein, red fluorescent protein, and severe acute respiratory syndrome coronavirus envelope protein were used as model proteins, and were selectively and functionally immobilized to the PHA microbeads by fusing them to the SBD. Using this PHA microbead system combined with SBD fusion technology, immunoassays could be successfully carried out. 相似文献