全文获取类型
收费全文 | 17868篇 |
免费 | 1373篇 |
国内免费 | 49篇 |
专业分类
电工技术 | 223篇 |
综合类 | 18篇 |
化学工业 | 4146篇 |
金属工艺 | 627篇 |
机械仪表 | 1292篇 |
建筑科学 | 319篇 |
矿业工程 | 5篇 |
能源动力 | 707篇 |
轻工业 | 1488篇 |
水利工程 | 97篇 |
石油天然气 | 14篇 |
无线电 | 3225篇 |
一般工业技术 | 4084篇 |
冶金工业 | 852篇 |
原子能技术 | 230篇 |
自动化技术 | 1963篇 |
出版年
2024年 | 18篇 |
2023年 | 230篇 |
2022年 | 309篇 |
2021年 | 589篇 |
2020年 | 443篇 |
2019年 | 502篇 |
2018年 | 560篇 |
2017年 | 653篇 |
2016年 | 703篇 |
2015年 | 602篇 |
2014年 | 841篇 |
2013年 | 1199篇 |
2012年 | 1257篇 |
2011年 | 1540篇 |
2010年 | 1106篇 |
2009年 | 1110篇 |
2008年 | 1011篇 |
2007年 | 791篇 |
2006年 | 694篇 |
2005年 | 612篇 |
2004年 | 565篇 |
2003年 | 534篇 |
2002年 | 508篇 |
2001年 | 383篇 |
2000年 | 338篇 |
1999年 | 319篇 |
1998年 | 422篇 |
1997年 | 291篇 |
1996年 | 218篇 |
1995年 | 159篇 |
1994年 | 130篇 |
1993年 | 117篇 |
1992年 | 82篇 |
1991年 | 68篇 |
1990年 | 64篇 |
1989年 | 72篇 |
1988年 | 46篇 |
1987年 | 45篇 |
1986年 | 28篇 |
1985年 | 40篇 |
1984年 | 22篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 10篇 |
1974年 | 2篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Selvaraj?Rengaraj Younghun?Kim Cheol?Kyun?Joo Kyunghee?Choi Jongheop?YiEmail author 《Korean Journal of Chemical Engineering》2004,21(1):187-194
The removal of copper from aqueous solution by ion exchange resins, such as 1200H and IRN97H, is described. Effect of initial
metal ion concentration, agitation time and pH on adsorption capacities of ion exchange resins was investigated in a batch
mode. The adsorption process, which is pH dependent, shows maximum removal of copper in the pH range 2–7 for an initial copper
concentration of 10 mg/L. The experimental data have been analyzed by using the Freundlich, Langmuir, Redlich-Peterson, Temkin
and Dubinin-Radushkevich isotherm models. The batch sorption kinetics have been tested for a first-order, pseudo-first order
and pseudo-second order kinetic reaction models. The rate constants of adsorption for all these kinetic models have been calculated.
Results showed that the intraparticle diffusion and initial sorption into resins of Cu(II) in the ion exchange resins was
the main rate limiting step. The uptake of copper by the ion exchange resins was reversible and thus has good potential for
the removal/recovery of copper from aqueous solutions. We conclude that such ion exchange resins can be used for the efficient
removal of copper from water and wastewater.
This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University. 相似文献
992.
We investigated the crystallization and orientation development in melt spinning and tubular blown film extrusion of several different types of polypropylenes, including conventional high tacticity isotactic polypropylenes (iPP) and metallocene catalyst low tacticity iPPs and syndiotactic polypropylenes (sPP). The fiber and film samples were characterized by wide‐angle X‐ray diffraction (WAXD), birefringence and differential scanning calorimetry (DSC). In melt spinning iPP, we found that the mesomorphic structure of iPP is more readily formed in lower tacticity fibers, and significant amounts of hexagonal β‐form crystals are found in low tacticity iPP fibers spun at high draw‐down ratios. Low tacticity iPP fibers exhibited a significant decrease in the crystalline chain‐axis orientation at high draw‐down ratios, resulting from increased epitaxially branched lamellae. Melt‐spun sPP fibers exhibit Form I helical structure at low spinning speeds and Form III zigzag all trans structure at high spinning speeds. We found that the level of spinline stress is the governing factor for this structural change. Melt‐spun sPP fibers exhibit much higher chain‐axis (c‐axis) orientation factors (fc) and lower birefringence than iPP fibers spun at the same spinline stresses. In tubular blown sPP films, the a‐axis of Form I unit cell tends to orient perpendicular to the film surface, while the b‐axis of monoclinic α unit cell does so in iPP blown films. 相似文献
993.
Saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) show different effects on the development of insulin resistance.
In this study, we compared the effect of dietary SFA and MUFA on the insulin signaling pathway in the skeletal muscle of a
type 2 diabetic animal model. Twenty-nine-week-old male Otsuka Long-Evans Tokushima fatty (OLETF) rats were randomly divided
into three groups and fed one of the following diets for 3 weeks; a normal chow diet, an SFA (lard oil) enriched or a MUFA
(olive oil) enriched high-fat diet. The vastus lateralis muscle was used for analyses. Insulin tolerance test showed improved
insulin sensitivity in rats fed the MUFA diet, as compared to those fed the SFA diet (p < 0.001). The SFA diet reduced IRS-1 expression and phosphorylated PI3K levels in skeletal muscle, as compared with a chow
diet (p < 0.001, respectively). On the contrary, muscle IRS-2 expression and phosphorylated ERK1/2 was significantly increased in
rats fed the SFA diet (p < 0.001, respectively). Membrane translocation of glucose transporter type 4 decreased in the skeletal muscle of rats fed
the SFA diet, as compared to those fed a chow diet (p < 0.001). These changes in insulin signaling pathway in skeletal muscle were not observed in rats fed the MUFA diet. In conclusion,
the beneficial effect of dietary MUFA on insulin sensitivity is associated with a conserved IRS-1/PI3K insulin signaling pathway
which was altered by dietary SFA. 相似文献
994.
The influence of backwashing on biological perchlorate reduction was evaluated in two laboratory scale fixed bed biofilm reactors using 1- or 3-mm glass beads as support media. Influent perchlorate concentrations were 50 microg/L and acetate was added as the electron donor at a concentration of 2 mg C/L. Perchlorate removal was evaluated at various influent dissolved oxygen (DO) concentrations. Complete perchlorate removal was achieved with an influent DO concentration of 1mg/L resulting in bulk phase DO concentrations below the detection limit of 0.01 mg/L. The influence of increasing influent DO concentrations for 12 h periods was evaluated before and after individual backwash events. Partial perchlorate removal was achieved with an influent DO concentration of 3.5 mg/L before a strong backwash (bulk phase DO concentrations of approximately 0.2mg/L), while no perchlorate removal was observed after the strong backwash at the same influent DO level (bulk phase DO concentrations of approximately 0.8 mg/L). The immediate effect of backwashing depended on influent DO concentrations. With influent DO concentrations of 1 mg/L, strong backwashing resulted in a brief (<12 h) increase of effluent perchlorate concentrations up to 20 microg/L; more pronounced effects were observed with influent DO concentrations of 3mg/L. Daily weak backwashing had a small and, over time, decreasing negative influence on perchlorate reduction, while daily strong backwashing ultimately resulted in the breakdown of perchlorate removal with influent DO concentrations of 3 mg/L. 相似文献
995.
Sunghee Lee Bora Choi Seung-Muk Yi GwangPyo Ko 《The Science of the total environment》2009,407(20):5308-5314
An Asian dust event, also sometimes known as a Yellow Sand event, is a seasonal meteorological phenomenon affecting East Asia, typically in the early spring. Because of the significant ecological and health effects of these events on East Asia, and the large amount of dust that is transported from the desert in China to Korea and Japan, these events have been receiving increased attention. It is likely that these storms often provide long-range transport to various microorganisms. However, despite a certain level of attention to the chemical analysis of these storms, microbiological studies of Yellow Sand dust have been scarce. We collected a total of 30 microbiological air samples using a PM2.5 cyclone sampler in Seoul, Korea from April 2007 to March 2008. Six of these samples were collected during Yellow Sand events, while 24 were from non-Yellow Sand events. Chemical analysis was performed on the samples using a thermal–optical transmittance (TOT) method. Total nucleic acids were also extracted, and the 16S rDNA was amplified by PCR and analyzed by denaturing gradient gel electrophoresis (DGGE). Dendrogram analysis, based on DGGE, indicated that the microbial profiles from the Yellow Sand were distinctive from those of the non-Yellow Sand samples. Microorganisms identified in Yellow Sand samples included Aquabacterium sp., Flavobacteriales bacterium sp., Prevotellaceae bacterium sp., and others, whereas microorganisms in non-Yellow Sand samples included Propionibacterium sp., Bacillus sp., Acinetobacter sp., and others. These results suggest that, as a result of Yellow Sand events, humans in the affected regions are exposed to communities of microorganisms that might cause various adverse health effects. 相似文献
996.
A basic reseach of tailored blank welding between a low carbon steel sheet and a STS 304 stainless steel sheet was carried
out with CO2 laser beam. The materials used in this work were a low carbon steel sheet with a thickness of 0.9 mm and a STS 304 stainless
steel sheet with the same thickness. Experiments were carried out by applying the Taguchi method to obtain optimized conditions
in order to apply this tailored blank laser welding method in the practical manufacturing process. In order to compare the
laser welding results with the conventional welding process, GTA welding was carried out for the same materials. Optical microscopy,
SEM and XRD analyses were performed to observe the microstructures and to analyze the various phases. A tensile test, hardness
test and Erichsen test were performed to evaluate the formability of welded specimens. In addition, immersion test was carried
to estimate corrosion resistance. A WDS analysis showed that laser welding resulted in almost the same dilution of both low
carbon steel and stainless steel in welded metal, meanwhile, GTA welding resulted in more dilution of stainless steel due
to its slower heat conductivity. The formability of the laser welded specimen reached 83% of that in base metal. On the other
hand, it was 63% in the case of GTA welding. During the tension test, base metal was fractured in the case of a laser welded
specimen, meanwhile the welded zone was fractured in the case of the GTA welded specimen. The corrosion test showed that weight
loss per unit area was less in the laser welded specimen than that of the GTA welded specimen. 相似文献
997.
Sunwoo Park Hueseok Choi Kihong Ryu Sayup Kim Youngho Kim 《Journal of Mechanical Science and Technology》2009,23(1):204-211
In this study, biomechanical characteristics during the whole process of gait initiation for twenty normal healthy volunteers
were determined by the motion analysis with six near-infrared cameras, four forceplates, and an EMG system. Gait initiation,
a transitional movement phenomenon from quiet stance to steady-state walking, involves a series of muscular activities, GRFs,
movements of COP and COM, and joint motions. Results showed that the location of the net COP to be most lateral during double
limb stance at the beginning of gait initiation. During gait initiation, changes in anteroposterior components of GRFs were
first found and then changes in vertical components followed. Hip and knee motions were found before the ankle joint motion.
Walking speed, step length, and stride length gradually increased until the second step. The interaction between the COM and
COP is tightly regulated to control the trajectory of the COM and thereby control total body balance.
This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo
Sun-Woo Park received a B.S. degree in Biomedical Engineering from Yonsei University in 2006. He is currently a M.S. candidate in the
Department of Biomedical Engineering, Yonsei University, Korea. His research interests in the area of Human Movement and detection
of gait phase using motion sensors.
Hue-Seok Choi received a B.S. degree in Computer Engineering from Daejeon University in 2004. He is currently a P.D. candidate at the Department
of Biomedical Engineering at Yonsei University, Korea. His research interests are in the area of Human Movement and Rehabilitation
Engineering.
Ki-Hong Ryu received a B.S. and M.S. degrees in Biomedical Engineering from Yonsei University in 1998 and 2001, respectively. He is currently
a P.D. candidate in the Department of Biomedical Engineering, Yonsei University, Korea. His research interests are in the
area of Human Movement and Gait Training System using Functional Electrical Stimulation.
Sa-Yup Kim received a B.S. degree in Electrical Engineering from Yeungnam University in 2002 and M.S. degrees in Biomedical Engineering
from Yonsei University in 2006. He is currently working from Korea Institute of Industrial Technology in Cheonan, Korea.
Young-Ho Kim received a B.S. degree in Mechanical Engineering from Hanyang University in 1982. He then went on to receive his M.S. and
Ph.D. degrees from University of Iowa in 1989 and 1991, respectively. He is currently a Professor in the Department of Biomedical
Engineering, Yonsei University, Korea. His research interests are in the area of Human Movement, Rehabilitation Engineering,
and Biomechanics. 相似文献
998.
Jung II-Ho Hwi Seo Jong Choi Sung-Jin Tae-Won Park Jang-Bom Chai 《Journal of Mechanical Science and Technology》2005,19(1):336-342
The DC motor of a vehicle may cause noise and vibration due to high-speed revolution, which can make a driver feel uncomfortable There have been various studies attempting to solve these problems, mostly focusing on the causes of noise and vibration and a means of preventing them The CAE methodology is more efficient than a real test for the purpose of looking for various design parameters to reduce the noise and vibration of the DC motor In this study, a design process for reducing brush noise is presented with the use of a computer model, which is made by using a multi-body dynamics program (DADS) The design parameters to reduce the brush noise and vibration were proposed using a computer model They were used to reduce the noise and vibration of the DC motor and verified by the test tesults of the fan DC motor in the vehicle This method may be applicable to various DC motors 相似文献
999.
Dong Won Lee Young Dug Bae Suk Kwon Kim Bong Guen Hong Hyun Kyu Jung Jeong Yong Park Yong Hwan Jeong Byung Kwon Choi 《Fusion Engineering and Design》2009,84(7-11):1160-1163
In order to verify the integrity of the first wall (FW) of the International Thermonuclear Experimental Reactor (ITER), especially for preparing its qualification program by ITER-O, Be/Cu/SS mock-ups, which were the same size as the qualification mock-ups, were fabricated and tested at the TSEFEY, an e-beam facility, in Efremov, Russia. These mock-ups were joined with a 316 L austenitic stainless steel (SS316L) block for a structural material, CuCrZr for a heat sink material and SS316L tubes for a coolant and then, joined with three Be tiles for an armor material. A hot isostatic pressing (HIP) was used as manufacturing methods at a 1050 °C, 100 MPa for 2 h for a Cu/SS joining and at a 580 °C, 100 MPa for 2 h for a Be/(Cu/SS) joining. Two mock-ups were fabricated by using 1 μmCr/10 μmCu of an interlayer between the Be tile and Cu block. The high heat flux (HHF) tests were performed at 1.5 and 2.0 MW/m2 heat fluxes for each mock-up. The given conditions and the expected fatigue lifetime were evaluated from a preliminary analysis with ANSYS. Both mock-ups survived for up to 1000 and 268 cycles at 1.5 and 2.0 MW/m2 heat fluxes, respectively. They are higher than the expected numbers of cycles to a failure. 相似文献
1000.
Daily meat consumption produces a lot of bone waste, and dumped bone waste without treatment would result in environmental hazards. Conventional treatment methods of waste bones have some disadvantages. Herein, an investigation of bone waste treated using thermal plasma technology is presented. A high-temperature plasma torch operated at 25.2 kW was used to treat bone waste for seven minutes. The bone waste was finally changed into vitric matter and lost 2/3 of its weight after the treatment. The process was highly efficient, economical, convenient, and fuel-free. This method could be used as an alternative for disposal of bone waste, small infectious animals, hazardous hospital waste, etc. 相似文献