全文获取类型
收费全文 | 437篇 |
免费 | 6篇 |
国内免费 | 6篇 |
专业分类
教育 | 321篇 |
科学研究 | 58篇 |
各国文化 | 5篇 |
体育 | 27篇 |
综合类 | 22篇 |
信息传播 | 16篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 16篇 |
2018年 | 10篇 |
2017年 | 7篇 |
2016年 | 6篇 |
2015年 | 18篇 |
2014年 | 31篇 |
2013年 | 36篇 |
2012年 | 36篇 |
2011年 | 35篇 |
2010年 | 28篇 |
2009年 | 30篇 |
2008年 | 19篇 |
2007年 | 25篇 |
2006年 | 28篇 |
2005年 | 21篇 |
2004年 | 21篇 |
2003年 | 9篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有449条查询结果,搜索用时 15 毫秒
11.
李琦 《安徽科技学院学报》2001,15(2):24-28
利用 195 3- 1993年全国烤烟单位面积产值、产量和上中等烟比重资料 ,将全国视为一个大区 ,划分全国烤烟高低产值、丰歉和优劣质年景 ,研究高低产值年烤烟产值与产量及上中等烟比重之间的关系 ,结果表明 :高产值年每hm2 烤烟平均产值 2 70 3 .0 3元、产量 16 0 8.75kg、上中等烟比重 49.77% ,气象产值、产量和上中等烟气象比重分别占实际产值、产量和上中等烟比重 17.92 %、11.2 4%和 3 .92 % ,由于气象条件有利使单产增加和上中等烟比重提高而增加的产值分别占气象产值 49.71%和 5 0 2 9% ;低产值年每hm2 烤烟平均产值 15 2 4.90元、产量 10 75 .71kg、上中等烟比重 42 .5 6 % ,气象产值、产量和上中等烟气象比重的绝对值分别占实际产值、产量和上中等烟比重 2 9.97%、18.6 9%和 2 .87% ,由于气象条件不利使单产减少和上中等烟比重降低而减少的产值分别占气象产值 5 2 .91%和47.0 9%。 相似文献
12.
Suneesh Kumar Pachathundikandi Earaly Thomas Varghese 《Indian journal of clinical biochemistry : IJCB》2006,21(2):114-117
Blood zinc protoporphyrin (ZPP), serum total protein (TP), and total cholesterol (TC) levels in automobile workshop workers
in relation to lead toxicity were analysed. In the present study, automobile workshop workers (healthy male workers at an
age between 28 and 35 from four major automobile workshops in Kottayam, Kerala State, India) and the control (male healthy
adults at an age between 28 and 35 residing at Aymanam, a distant village at Kottayam District, Kerala having reduced or no
chance of lead exposure) displayed significant difference in blood lead (BPb) and blood ZZP (BZPP) level. The mean value of
BPb in automobile workshop workers was 15.76±0.33 μg/dl, while in the control it was 8.20±0.15 μg/dl. In automobile workshop
workers, the mean value of BZPP was 34.2±0.62 μg/dl. The control group exhibited a mean of 11.5±0.22 μg/dl. Automobile workshop
workers exhibited significant increase in BZPP was corresponding to the increase in BPb level. The total protein levels estimated
in automobile workshop workers showed significant decrease compared to control individuals, but was within the reference range
of healthy individuals. The mean value of TP level in automobile workshop workers and control was 6.9±0.13 g/dl and 7.71±0.18
g/dl, respectively. There was no significant difference in blood haemoglobin (BHb) level among the automobile workshop workers
and control. The serum TC level in automobile workshop workers showed significant decrease compared to the control individuals,
but was with in the reference range of healthy individuals. The mean level of serum TC in automobile workshop workers was
162.00±3.44 mg/dl and the same in control was 172.86±4.32 mg/dl. The present study affirms occupational lead toxicity in automobile
workshop workers and its effect on serum protein and cholesterol levels. 相似文献
13.
武建国 《湖北广播电视大学学报》2011,31(5):89-90
在冰天雪地、滴水成冰的严寒深冬里,如何才能得到一幅完美的冰雪摄影佳作,关键是如何正确测光,如何正确曝光,这些都是决定拍摄成败的关键。 相似文献
14.
15.
Kelsey H.Collins Graham Z.MacDonald David A.Hart Ruth A.Seerattan Jaqueline L.Rios Raylene A.Reimer Walter Herzog 《运动与健康科学(英文)》2020,9(2):132-139,197
Background:Osteoarthritis is one of the leading causes of pain and disability worldwide,and a large percentage of patients with osteoarthritis are individuals who are also obese.In recent years,a series of animal models have demonstrated that obesity-inducing diets can result in synovial joint damage(both with and without the superimposition of trauma),which may be related to changes in percentage of body fat and a series of low-level systemic inflammatory mediators.Of note,there is a disparity between whether the dietary challenges commence at weaning,representing a weanling onset,or at skeletal maturity,representing an adult onset of obesity.We wished to evaluate the effect ofthe dietary exposure time and the age at which animals are exposed to a high-fat and high-sucrose(HFS) diet to determine whether these factors may result in disparate outcomes,as there is evidence suggesting that these factors result in differential metabolic disturbances.Based on dietary exposure time,we hypothesized that rats fed an HFS diet for 14 weeks from weaning(HFS Weanling) would demonstrate an increase in knee joint damage scores,whereas rats exposed to the HFS diet for 4 weeks,starting at 12 weeks of age(HFS Adult) and rats exposed to a standard chow diet(Chow)would not display an increase in knee joint damage scores.Methods:Male Sprague-Dawley rats were fed either an HFS diet for 14 weeks from weaning(HFS Weanling) or an HFS diet for 4 weeks,starting at 12 weeks of age(HFS Adult).At sacrifice,joints were scored using the modified Mankin Criteria,and serum was analyzed for a defined subset of inflammatory markers(Interleukin-6,leptin,monocyte chemoattractant protein-1,and tumor necrosis factorα).Results:When the HFS Weanling and HFS Adult groups were compared,both groups had a similar percent of body fat,although the HFS Weanling group had a significantly greater body mass than the HFS Adult group.The HFS Weanling and HFS Adult animals had a significant increase in body mass and percentage of body fat when compared to the Chow group.Although knee joint damage scores were low in all 3 groups,we found,contrary to our hypothesis,that the HFS Adult group had statistically significant greater knee joint damage scores than the Chow and HFS Weanling groups.Furthermore,we observed that the HFS Weanling group did not have significant differences in knee joint damage scores relative to the Chow group.Conclusion:These findings indicate that the HFS Weanling animals were better able to cope with the dietary challenge of an HFS diet than the HFS Adult group.Interestingly,when assessing various serum proinflammatory markers,no significant differences were detected between the HTS Adult and HFS Weanling groups.Although details regarding the mechanisms underlying an increase in knee joint damage scores in the HFS Adult group remain to be elucidated,these findings indicate that dietary exposure time maybe less important than the age at which an HFS diet is introduced.Moreover,increases in serum proinflammatory mediators do not appear to be directly linked to knee joint damage scores in the HFS Weanling group animals but may be partially responsible for the observed knee joint damage in the adults over the very short time of exposure to the HFS diet. 相似文献
16.
急性低氧暴露对足球运动员甲襞微循环影响的实验研究 总被引:1,自引:0,他引:1
通过实验观察急性低氧暴露对足球运动员甲襞微循环的影响并探讨其作用机理,得出:急性低氧暴露后,(1)运动员安静时形态积分较高,运动后10min、15min的形态积分均比安静时明显降低(P<0.05);(2)运动后即刻的流态积分、总积分均显著高于安静时(P<0.05),运动后5min、10min及15min时,血流速逐渐加快,红细胞聚集程度减轻,积分值降低。 相似文献
17.
对云南省3个主要产烟区不同品种、不同部位烟叶中碳水化合物含量的变化规律以及不同施肥情况、连作和轮作对烟叶样品中碳水化合物含量的影响进行了分析研究.结果表明轮作烟叶样品中总糖和淀粉含量均高于连作烟叶样品;不同施肥情况的烟叶样品中总糖含量的变化规律与淀粉含量的变化规律正好相反;不同部位烟叶样品中总糖、淀粉和总细胞壁物质含量的变化规律也各不相同. 相似文献
18.
19.
Anne Schulz 《Communication monographs》2019,86(1):88-111
This article presents a secondary analysis of two multi-national cross-sectional surveys conducted in 2015 (11 countries, N?=?10,570) and 2017 (4 countries, N?=?2165) to examine the relationship between populist attitudes and media use. The results indicate that populist citizens are more likely to consume news than non-populist citizens. Specifically, populist citizens exhibit a preference for commercial television (TV) news, as well as a tendency to read tabloid newspapers. While they use fewer quality newspapers, public TV news are not systematically avoided. Regarding the online news environment, populist citizens prefer Facebook over Twitter as a source of political information. This selective pattern will be discussed in light of the debates on news audience polarization and political polarization. 相似文献
20.
Using two experiments, this study aims to investigate how politically liberal or conservative message recipients respond to anti-tobacco appeals. The results show that in Study 1, respondents were exposed to a message about price policy. In Study 2, they were exposed to a message about a warning policy. In both studies, liberal participants more favorably evaluated anti-tobacco messages emphasizing feasibility rather than desirability, whereas conservative participants more positively evaluated messages emphasizing desirability rather than feasibility. Implications for policymakers and marketers are discussed. 相似文献