全文获取类型
收费全文 | 3199篇 |
免费 | 33篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 12篇 |
综合类 | 1篇 |
化学工业 | 228篇 |
金属工艺 | 21篇 |
机械仪表 | 41篇 |
建筑科学 | 19篇 |
矿业工程 | 1篇 |
能源动力 | 25篇 |
轻工业 | 54篇 |
水利工程 | 4篇 |
石油天然气 | 3篇 |
无线电 | 109篇 |
一般工业技术 | 195篇 |
冶金工业 | 2395篇 |
原子能技术 | 7篇 |
自动化技术 | 120篇 |
出版年
2022年 | 14篇 |
2021年 | 28篇 |
2020年 | 17篇 |
2019年 | 23篇 |
2018年 | 32篇 |
2017年 | 16篇 |
2016年 | 32篇 |
2015年 | 17篇 |
2014年 | 21篇 |
2013年 | 54篇 |
2012年 | 35篇 |
2011年 | 36篇 |
2010年 | 31篇 |
2009年 | 39篇 |
2008年 | 32篇 |
2007年 | 34篇 |
2006年 | 32篇 |
2005年 | 29篇 |
2004年 | 23篇 |
2003年 | 26篇 |
2002年 | 25篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 68篇 |
1998年 | 698篇 |
1997年 | 415篇 |
1996年 | 251篇 |
1995年 | 141篇 |
1994年 | 129篇 |
1993年 | 156篇 |
1992年 | 27篇 |
1991年 | 31篇 |
1990年 | 23篇 |
1989年 | 41篇 |
1988年 | 38篇 |
1987年 | 46篇 |
1986年 | 34篇 |
1985年 | 30篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 25篇 |
1981年 | 24篇 |
1980年 | 38篇 |
1979年 | 7篇 |
1978年 | 13篇 |
1977年 | 94篇 |
1976年 | 203篇 |
1975年 | 9篇 |
1974年 | 7篇 |
1973年 | 7篇 |
排序方式: 共有3235条查询结果,搜索用时 15 毫秒
51.
In this work, we designed, fabricated and tested a disposable, flow-through amperometric sensor for free chlorine determination in water. The sensor is based on the principle of an electrochemical cell. The substrate, as well as the top microfluidic layer, is made up of a polymer material. The advantages include; (a) disposability from low cost; (b) stable operation range from three-electrode design; (c) fluidic interconnections that provide on line testing capabilities; and (d) transparent substrate which provides for future integration of on-chip optics. The sensor showed a good response and linearity in the chlorine concentration ranging from 0.3 to 1.6 ppm, which applies to common chlorination process for drinking water purification. 相似文献
52.
53.
54.
55.
56.
This paper presents a device proposal based on a junction between an absorbing semiconductor nanorod structure and another window semiconductor layer for solar cell application. The possibility of band gap tuning by varying the diameter of the nanorods along the length, higher absorption coefficient at nanodimensions, the presence of a strong electrical field at the nanorod-window semiconductor nanojunctions and the carrier confinement in lateral direction are expected to result in enhanced absorption and collection efficiency in the proposed device. Process steps, feasibility, technological tasks needed for the realization of the proposed structure and the novelty of the present structure in comparison to the already reported nanostructured solar cells are also discussed. 相似文献
57.
58.
Fetal and maternal lipoprotein metabolism in human pregnancy complicated by type I diabetes mellitus
Serum lipid, apolipoprotein concentration, and lipoprotein composition were determined in maternal and umbilical venous cord blood at delivery by elective Cesarean section (CS) in 10 singleton, full-term pregnancies with maternal insulin-dependent diabetes mellitus (type I DM), which predated pregnancy, and in 22 nondiabetic pregnancies. The objectives of the study were to determine the influence of maternal type I DM, and hence potential fetal overnutrition on fetal lipid metabolism. There were no significant differences in gestational age, fetal weight, or fetal serum insulin concentration between the type I DM group and those with nondiabetic pregnancies, although fetal venous cord blood glucose was 3.4 mmol/L (3.0-4.5 mmol/L) (median and 25th-75th percentiles) and 2.9 mmol/L (2.0-3.4 mmol/L), respectively, and maternal Hemoglobin A1c [9.6% (8.2-10.7%) and 6.8% (6.3-7.8%), respectively], was significantly greater in the type I DM subjects (P < 0.02 and 0.002 respectively). Plasma nonesterified fatty acid (NEFA) concentrations were lower in the type I DM mothers [0.85 mmol/L (0.56-2.31 mmol/L) compared with 1.14 mmol/L (0.88-1.24 mmol/L] in nondiabetic pregnancies; P < 0.0001). Serum high-density lipoprotein phospholipids (HDL-PL) were increased in type I DM mothers because of elevated HDL2 phospholipid [0.39 mmol/L (0.27-0.48 mmol/L) compared with 0.12 mmol/L (0.06-0.21 mmol/L), respectively, P < 0.01). The maternal HDL cholesterol (C) concentration was not significantly different in the uncomplicated and type I DM pregnancies. However, in the umbilical venous cord blood, serum levels of NEFA [0.49 mmol/L (0.33-1.29 mmol/L) in type I DM compared with 0.13 mmol/L (0.06-0.33 mmol/L) in nondiabetics; P < 0.02)], total cholesterol (TC) [2.87 mmol/L (1.65-4.86 mmol/L) in type I DM compared with 1.65 mmol/L (1.46-1.87 mmol/L) in nondiabetics; P < 0.02]; free cholesterol (FC) [0.97 mmol/L (0.60-1.26 mmol/L) in type I DM compared with 0.62 mmol/L (0.37-0.75 mmol/L) in nondiabetics; P < 0.05), and cholesteryl ester (CE) [1.90 mmol/L (1.44-3.33 mmol/L) in type I DM compared with 1.01 mmol/L (0.83-1.24 mmol/L) in nondiabetics; P < 0.02), triglyceride (TG) (1.06 [0.50-1.91) mmol/L in type I DM compared with 0.29 [0.25-0.36] mmol/l in nondiabetics; P < 0.001), phospholipid (PL) (2.52 [1.73-3.03) mmol/L in type I DM compared with 1.34 [1.27-1.48] mmol/L in nondiabetics; P < 0.01], and the apolipoproteins A-I and B had significantly higher concentrations in type I DM. In umbilical venous cord blood, ratios of HDL-TC and HDL-PL to apo AI, reflecting the lipid content of HDL, were reduced when the mother had type I DM during pregnancy (P < 0.02 and P < 0.0001, respectively). These results indicate that maternal type I DM may lead to a fetal serum lipoprotein composition more closely resembling that seen in the adult. In type I DM, maternal TG and PL and fetal TC, TG, PL, CE, and FC were correlated to NEFA levels (P < 0.05), but not to glucose, insulin secretion, or maternal control of type I DM. These data suggest that the enhanced supply of NEFA to the fetus in type I DM pregnancies may drive the synthesis of cholesterol as well as TGs and PLs. 相似文献
59.
60.
SA Kliewer JT Moore L Wade JL Staudinger MA Watson SA Jones DD McKee BB Oliver TM Willson RH Zetterstr?m T Perlmann JM Lehmann 《Canadian Metallurgical Quarterly》1998,92(1):73-82
PURPOSE: To determine the effects of 28 d of creatine supplementation during training on body composition, strength, sprint performance, and hematological profiles. METHODS: In a double-blind and randomized manner, 25 NCAA division IA football players were matched-paired and assigned to supplement their diet for 28 d during resistance/agility training (8 h x wk[-1]) with a Phosphagen HP (Experimental and Applied Sciences, Golden, CO) placebo (P) containing 99 g x d(-1) of glucose, 3 g x d(-1) of taurine, 1.1 g x d(-1) of disodium phosphate, and 1.2 g x d(-1) of potassium phosphate (P) or Phosphagen HP containing the P with 15.75 g x d(-1) of HPCE pure creatine monohydrate (HP). Before and after supplementation, fasting blood samples were obtained; total body weight, total body water, and body composition were determined; subjects performed a maximal repetition test on the isotonic bench press, squat, and power clean; and subjects performed a cycle ergometer sprint test (12 x 6-s sprints with 30-s rest recovery). RESULTS: Hematological parameters remained within normal clinical limits for active individuals with no side effects reported. Total body weight significantly increased (P < 0.05) in the HP group (P 0.85 +/- 2.2; HP 2.42 +/- 1.4 kg) while no differences were observed in the percentage of total body water. DEXA scanned body mass (P 0.77 +/- 1.8; HP 2.22 +/- 1.5 kg) and fat/bone-free mass (P 1.33 +/- 1.1; HP 2.43 +/- 1.4 kg) were significantly increased in the HP group. Gains in bench press lifting volume (P -5 +/- 134; HP 225 +/- 246 kg), the sum of bench press, squat, and power clean lifting volume (P 1,105 +/- 429; HP 1,558 +/- 645 kg), and total work performed during the first five 6-s sprints was significantly greater in the HP group. CONCLUSION: The addition of creatine to the glucose/taurine/electrolyte supplement promoted greater gains in fat/bone-free mass, isotonic lifting volume, and sprint performance during intense resistance/agility training. 相似文献