全文获取类型
收费全文 | 1195篇 |
免费 | 46篇 |
专业分类
电工技术 | 6篇 |
综合类 | 5篇 |
化学工业 | 308篇 |
金属工艺 | 31篇 |
机械仪表 | 12篇 |
建筑科学 | 20篇 |
能源动力 | 8篇 |
轻工业 | 120篇 |
水利工程 | 7篇 |
无线电 | 101篇 |
一般工业技术 | 184篇 |
冶金工业 | 348篇 |
原子能技术 | 9篇 |
自动化技术 | 82篇 |
出版年
2023年 | 10篇 |
2022年 | 10篇 |
2021年 | 22篇 |
2020年 | 20篇 |
2019年 | 13篇 |
2018年 | 20篇 |
2017年 | 17篇 |
2016年 | 24篇 |
2015年 | 23篇 |
2014年 | 19篇 |
2013年 | 35篇 |
2012年 | 33篇 |
2011年 | 55篇 |
2010年 | 40篇 |
2009年 | 41篇 |
2008年 | 33篇 |
2007年 | 37篇 |
2006年 | 41篇 |
2005年 | 22篇 |
2004年 | 24篇 |
2003年 | 32篇 |
2002年 | 34篇 |
2001年 | 33篇 |
2000年 | 31篇 |
1999年 | 36篇 |
1998年 | 96篇 |
1997年 | 64篇 |
1996年 | 49篇 |
1995年 | 37篇 |
1994年 | 21篇 |
1993年 | 34篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 20篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 16篇 |
1976年 | 17篇 |
1975年 | 5篇 |
1966年 | 7篇 |
排序方式: 共有1241条查询结果,搜索用时 15 毫秒
1.
2.
Iryna Smokovych Manja Krüger Michael Scheffler 《Journal of the European Ceramic Society》2019,39(13):3634-3642
Silica-based coating systems were developed using polymer derived ceramics (PDCs) technology. Ceramic composites on the base of a SiO2 and SiNO matrix and homogeneously distributed Mo5SiB2, SiB6, Si and B fillers were manufactured. The coating systems have low porosity and provide a high oxidation resistance up to 100 h at 800 °C and 1100 °C in air. The influence of temperature and atmosphere of pyrolysis on the polymer precursor, the volume fraction of filler materials on the chemical composition of compacts as well as their high-temperature oxidation protection was investigated. 相似文献
3.
4.
5.
6.
7.
Biodegradation of monoaromatic hydrocarbons in aquifer columns amended with hydrogen peroxide and nitrate 总被引:1,自引:0,他引:1
The ability of indigenous microorganisms to degrade benzene, toluene, ethylbenzene and xylenes (BTEX) in laboratory scale flow-through aquifer columns was tested separately with hydrogen peroxide (110 mg/l) and nitrate (330 mg/l as NO3−) amendments to air-saturated influent nutrient solution. The continuous removal of individual components from all columns relative to the sterile controls provided evidence for biodegradation. In the presence of hydrogen peroxide, the indigeneous microorganisms degraded benzene and toluene (> 95%), meta- plus para-xylene (80%) and ortho-xylene (70%). Nitrate addition resulted in 90% removal of toluene and 25% removal of ortho-xylene. However, benzene, ethylbenzene, meta- and para-xylene concentrations were not significantly reduced after 42 days of operation. Following this experiment, low dissolved oxygen (< 1 mg/l) conditions were initiated with the nitrate-amended column influent in order to mimic contaminated groundwater conditions distal from a nutrient injection well. Toluene continued to be effectively degraded (> 90%), and more than 25% of the benzene, 40% of the ethylbenzene, 50% of the meta- plus para-xylenes and 60% of the ortho-xylene were removed after several months of operation. 相似文献
8.
J.-P. Han S.M. Koo E.M. Vogel E.P. Gusev C. DEmic C.A. Richter J.S. Suehle 《Microelectronics Reliability》2005,45(5-6):783
Anomalous threshold voltage roll-up behavior, commonly referred as reverse short channel effect (RSCE), has been observed in high-k (HfO2 on SiON buffer, Al2O3 on SiON buffer) gated submicron nMOSFETs, while the SiO2 or SiON control samples show normal short channel effect (SCE) behavior. The possible causes such as inhomogeneous channel doping profile and gate oxide thickness variation near S/D ends have been ruled out. The results indicate that interface trap density that dependents on channel length is the main cause of the RSCE observed here. In addition, oxide charge also plays a role. 相似文献
9.
10.
RF Maier B Bialobrzeski A Gross M Vogel JW Dudenhausen M Obladen 《Canadian Metallurgical Quarterly》1995,86(6):973-977
OBJECTIVE: To assess the risk for acute and chronic fetal hypoxia in twin pregnancies. METHODS: We investigated 50 sets of twins (24-38 weeks' gestation, 660-3200 g birth weight) admitted consecutively to our neonatal intensive care unit. Seventy-six infants were appropriate for gestational age (AGA; tenth to 90th percentile), 20 were small for gestational age (SGA; below the tenth percentile), and four were large for gestational age (above the 90th percentile). Twenty-six singleton AGA term newborns served as controls. Umbilical arterial pH was used as a marker for acute and umbilical venous erythropoietin concentration for chronic fetal hypoxia. The results are given as median followed by quartiles. RESULTS: We identified 40 sets of diamniotic-dichorionic twins and ten sets of diamniotic-monochorionic twins with transplacental vascular shunts. In the second-born twin, umbilical arterial pH was lower (7.29, 7.23-7.33) than in the firstborn (7.31, 7.25-7.34) (P = .03), and the incidence of a low pH (less than 7.20) was higher (19 versus 11%). Two second-born twins and none of the firstborn twins had an umbilical arterial pH less than 7.05. In SGA twins, the erythropoietin concentration was elevated (34.8, 22.8-325 mU/mL) compared with that in AGA twins (16.2, 8.2-26.6 mU/mL) (P < .01). In AGA twins, erythropoietin concentration did not differ from that in AGA singleton newborns (19.6, 14.7-31.6 mU/mL). In 12 of 17 twin sets with weight discordancy greater than 15% and in all five twin sets with weight difference greater than 25%, erythropoietin concentration was higher in the smaller twin. The proportion of infants and of complete sets with elevated erythropoietin levels was higher (P < .01) in monochorionic than in dichorionic pregnancies. CONCLUSION: The second-born twin is at increased risk for acute birth asphyxia. Fetal growth restriction in twin pregnancies is associated with chronic fetal hypoxia. Monochorionic twins are at higher risk for chronic fetal hypoxia than are dichorionic twins. 相似文献