Author Keywords: Vegetation; natural covering; green covering; field survey; urban area 相似文献
全文获取类型
收费全文 | 4164篇 |
免费 | 414篇 |
国内免费 | 579篇 |
出版年
2023年 | 61篇 |
2022年 | 70篇 |
2021年 | 107篇 |
2020年 | 142篇 |
2019年 | 177篇 |
2018年 | 162篇 |
2017年 | 155篇 |
2016年 | 158篇 |
2015年 | 162篇 |
2014年 | 223篇 |
2013年 | 362篇 |
2012年 | 168篇 |
2011年 | 212篇 |
2010年 | 166篇 |
2009年 | 207篇 |
2008年 | 238篇 |
2007年 | 245篇 |
2006年 | 210篇 |
2005年 | 190篇 |
2004年 | 175篇 |
2003年 | 173篇 |
2002年 | 163篇 |
2001年 | 125篇 |
2000年 | 110篇 |
1999年 | 95篇 |
1998年 | 70篇 |
1997年 | 73篇 |
1996年 | 76篇 |
1995年 | 93篇 |
1994年 | 72篇 |
1993年 | 62篇 |
1992年 | 64篇 |
1991年 | 57篇 |
1990年 | 23篇 |
1989年 | 38篇 |
1988年 | 30篇 |
1987年 | 25篇 |
1986年 | 29篇 |
1985年 | 21篇 |
1984年 | 27篇 |
1983年 | 31篇 |
1982年 | 21篇 |
1981年 | 18篇 |
1980年 | 20篇 |
1979年 | 12篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1973年 | 3篇 |
1972年 | 10篇 |
1971年 | 4篇 |
排序方式: 共有5157条查询结果,搜索用时 15 毫秒
41.
42.
Tadahisa Katayama Akio Ishii Tetsuo Hayashi Jun-ichiro Tsutsumi 《Journal of thermal biology》1993,18(5-6):571-576
1. 1. Three kinds of field survey on different scales were carried out in Fukuoka City in summer to examine the relationship between the quantity of vegetation and air temperature.
2. 2. The field of the largerst scale measurement is across the city.
3. 3. Several parks and shrines of various sizes in the city were selected as other measurement areas.
4. 4. The most detailed measurements are carried out in a park with an area of 1.25 ha located in a down town area of the city.
5. 5. Though the amount of vegetation is expressed in a unique way in each survey, it is clearly found that the greener it is, the lower is the air temperature.
43.
Climate reconstructions for the Common Era are compromised by the paucity of annually-resolved and absolutely-dated proxy records prior to medieval times. Where reconstructions are based on combinations of different climate archive types (of varying spatiotemporal resolution, dating uncertainty, record length and predictive skill), it is challenging to estimate past amplitude ranges, disentangle the relative roles of natural and anthropogenic forcing, or probe deeper interrelationships between climate variability and human history. Here, we compile and analyse updated versions of all the existing summer temperature sensitive tree-ring width chronologies from the Northern Hemisphere that span the entire Common Era. We apply a novel ensemble approach to reconstruct extra-tropical summer temperatures from 1 to 2010 CE, and calculate uncertainties at continental to hemispheric scales. Peak warming in the 280s, 990s and 1020s, when volcanic forcing was low, was comparable to modern conditions until 2010 CE. The lowest June–August temperature anomaly in 536 not only marks the beginning of the coldest decade, but also defines the onset of the Late Antique Little Ice Age (LALIA). While prolonged warmth during Roman and medieval times roughly coincides with the tendency towards societal prosperity across much of the North Atlantic/European sector and East Asia, major episodes of volcanically-forced summer cooling often presaged widespread famines, plague outbreaks and political upheavals. Our study reveals a larger amplitude of spatially synchronized summer temperature variation during the first millennium of the Common Era than previously recognised. 相似文献
44.
《Electromagnetic biology and medicine》2013,32(1):14-20
Objective: Electromagnetic fields can affect intracellular Ca2+ levels. The aim of this study was to determine the changes intracellular Ca2+ concentration in cardiac ventricle cells of rats exposed to 0.25 mT (2.5 Gauss) magnetic field.Methods: Forty-five male rats were introduced to this study. The rats were divided into three groups: control, sham, and experiment. The experimental group was exposed to 0.25 mT extremely low frequency (ELF) magnetic field for 14 days, 3 h/day. The sham group was treated like the experimental group, except for elf-magnetic field exposure. The control group was not subjected to anything and differed from the experimental group and sham group. In the end of experiment, rats were sacrificed, cardiac tissue was removed, and these were fixed in 10% neutral formalin. Then, ventricular cells were stained by Alizarin red staining method.Results: In the light microscopic examinations of control groups, in myofibril structures between groups, changes were not observed. In myofibril regions of the experimental group compared to other groups, increased heterogen Ca2+ accumulations were found.Conclusion: ELF magnetic fields are used in daily life. The results of this study show that intracellular Ca2+ accumulation in cardiac ventricles can increase in rats exposed to ELF magnetic field. 相似文献
45.
《Bioscience, biotechnology, and biochemistry》2013,77(11):2552-2554
The effects of an extremely low frequency magnetic field (ELFMF) on the germination of plant seeds were examined. The decrease in the germination activity of the seeds of Arabidopsis thaliana WS kept in saturated humidity and high temperature (37°C) was suppressed by the exposure to a 400 mT ELFMF. 相似文献
46.
47.
48.
《Electromagnetic biology and medicine》2013,32(2):81-96
Exposure of T lymphocytes to an external 50 Hz and 0.5 mT magnetic field was investigated in vitro using leukocyte adherence inhibition (LAI) assay which is a measure of cell-mediated immunity. Adherence of T lymphocytes taken from healthy humans and from cancer patients before and after medical treatment is enhanced after 1 h exposure to the magnetic field. The experimental findings for the magnetic field 0.5 mT are compared with published data for 1 and 10 mT. The results are consistent with suggestions of magnetic field effects on immune function in humans. 相似文献
49.
《Bioscience, biotechnology, and biochemistry》2013,77(9):1714-1715
We found that interferon-α produced by human leukocytes contained four subtypes that were glycosylated by N-linkages according to the results of lectin blot analysis. These glycosylated subtypes were type H or type ω and thei sugar moieties had no relation to their biological activities. 相似文献
50.
《Electromagnetic biology and medicine》2013,32(1):19-29
In this study, we investigated how rat reproductive cells, testosterone, and the fatty acid composition of the phospholipid fraction of rats' testis cells are affected by extremely low frequency magnetic field (ELFMF). The change in fatty acid composition of the membrane phospholipid fraction can be the mechanism for this effect. We used a total of 26 male Wistar Albino rats, 14 experimental, and 12 controls. The experimental group rats were exposed to a magnetic field (0.8 mT) for 5 weeks, 3 hr per day. The control group rats were kept between inactive coils. After 5 weeks, the testis tissues and sperm cells of all rats were histopathologically investigated and sperm counts determined. Epididymal sperm count did not change compared to the control group (p>.05). Besides this, amorphous head, banana-like head, hammer head, coiled tail, abnormal mid-piece and tail, multiple, and cytoplasmic-droplet type cell numbers did not change in either group (p>.05). However, a statistical difference was found between the control and experimental groups with respect to head with lack of hook and isolated head type sperm (p<.05). In addition, testosterone levels were also found to be altered (p<.05). In the histopathologic investigation of testis tissue, decreased spermatogenesis in some seminiferous tubules, congestion in blood vessels of the interstitium, and increases in interstitial edema and Sertoli cells were observed. Leydig cells were found to be normal in appearance. The fatty acid of the testis cell membrane phospholipids was decreased in the experimental group with respect to the control group. 相似文献