首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2284篇
  免费   116篇
  2022年   4篇
  2021年   20篇
  2020年   14篇
  2019年   22篇
  2018年   27篇
  2017年   26篇
  2016年   51篇
  2015年   77篇
  2014年   87篇
  2013年   128篇
  2012年   160篇
  2011年   163篇
  2010年   92篇
  2009年   89篇
  2008年   147篇
  2007年   178篇
  2006年   142篇
  2005年   155篇
  2004年   148篇
  2003年   131篇
  2002年   134篇
  2001年   23篇
  2000年   21篇
  1999年   31篇
  1998年   22篇
  1997年   15篇
  1996年   18篇
  1995年   18篇
  1994年   25篇
  1993年   17篇
  1992年   21篇
  1991年   23篇
  1990年   16篇
  1989年   18篇
  1988年   12篇
  1987年   17篇
  1986年   7篇
  1985年   8篇
  1984年   9篇
  1983年   6篇
  1982年   6篇
  1981年   11篇
  1979年   9篇
  1978年   5篇
  1975年   4篇
  1974年   4篇
  1973年   4篇
  1971年   8篇
  1969年   4篇
  1965年   3篇
排序方式: 共有2400条查询结果,搜索用时 46 毫秒
1.
Despite increasing interest in the behavior of zoo animals, studies of nocturnal behavior of zoo animals are limited. In this study, we investigated the relationship between parturition, season, and the sleep‐related behaviors in captive reticulated giraffes to better understand the nocturnal life in giraffes. The subjects were two adult reticulated giraffes living in Kyoto City Zoo, Japan. Observations were made via an infrared camera that was mounted in the indoor enclosure between June 2007 and August 2009. We analyzed video clips that were recorded between 16:30 and 09:00 the next morning, over a total of 199 days. Sleep‐related behaviors were classified into two categories based on the posture of the giraffes; recumbent posture and paradoxical sleep. We also recorded the laterality of recumbent posture, which was coded based on the direction of the legs against the torso (right or left). Seasonal differences in sleep behaviors between summer and winter were observed in both individuals. They tended to start to lie down earlier in the winter than in the summer. Parturition also affected the behaviors as both individuals decreased the behaviors before and after the parturition of the female. Additionally, the female lay on her left side less frequently than her right when resuming a recumbent posture in the pre‐parturition period, while such laterality was not observed in the baseline and post‐parturition period. These results suggested that season and parturition are important factors for determining the sleep‐related behaviors in giraffes. Further studies are needed to understand how these changes in sleep affect other welfare parameters.  相似文献   
2.
3.
The first 12 NH2-terminal amino acids of the Pseudomonas putida putidaredoxin reductase were shown to be Met-Asn-Ala-Asn-Asp-Asn-Val-Val-Ile-Val-Gly-Thr. Comparison of these data with the DNA sequence of the BamHI-HindIII 197-base fragment derived from the PstI 2.2-kb fragment obtained from the P. putida plasmid showed that the putidaredoxin reductase gene was downstream from the cytochrome P-450 gene and the intergenic region had the 24-nucleotide sequence TAAACACATGGGAGTGCGTGCTAA. The Shine-Dalgarno sequence GGAG was detected in this region. The initiating triplet for the reductase gene was GTG, which normally codes for valine, but in the initiating codon position codes for methionine. From the amino acid sequence and X-ray data comparisons with other flavoproteins, what appears to be the AMP binding region of the FAD can be recognized in the NH2-terminal portion of the reductase involving residues 5–35.This article was presented during the proceedings of the International Conference on Macromolecular Structure and Function, held at the National Defence Medical College, Tokorozawa, Japan, December 1985.  相似文献   
4.
5.
Early embryonic mitosis of the silkworm, Bombyx mori, was morphologically studied in the normal eggs and in the eggs treated by low temperature (?10°C). The first embryonic mitosis is observed in the eggs at 120 to 150 minutes after deposition at 26°C. After egg and sperm pronuclei unite, a spindle is formed in each of the pronuclei independently. At metaphase and anaphase paternal and maternal chromosomes are in separate groups on a spindle (gonomeric) and karyogamy takes place at telophase when they reach the poles. The second embryonic mitosis is shown in the eggs at 180 to 210 minutes after deposition. The division of two nuclei is not synchronous in the silkworm, and the mitosis is not gonomeric. In the eggs treated by low temperature, spindle fibers are not observed at all at ?10°C, and chromosomes, which form two deeply stained masses of irregular shape, are seen in the less stained area of spindle shape. When the eggs are returned to 26°C, some eggs go into normal gonomeric division, while some form two small and compact spindles, which seem to be derived from each of the pronuclei. It was observed that these compact spindles are able to continue mitosis.  相似文献   
6.
7.
In recent years, rare earth elements (REEs) have been widely used in various modern technological devices and the global demand for REE has been increasing. The increased demand for REEs has led to environmental exposure or water pollution from rare earth metal mines and various commercial products. Therefore, the development of a safe technology for the separation and adsorption of REEs is very important from the perspective of green chemistry and environmental pollution. In this review, the application and mechanisms of microorganisms for the removal and extraction of REEs from aqueous solutions are described. In addition, the advantages in using microorganisms for REE adsorption and future studies on this topic are discussed.  相似文献   
8.
9.
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号