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   9298篇
  免费   27篇
  国内免费   38篇
  2023年   13篇
  2022年   97篇
  2021年   220篇
  2020年   120篇
  2019年   192篇
  2018年   337篇
  2017年   332篇
  2016年   584篇
  2015年   766篇
  2014年   623篇
  2013年   1101篇
  2012年   631篇
  2011年   469篇
  2010年   694篇
  2009年   572篇
  2008年   491篇
  2007年   451篇
  2006年   429篇
  2005年   292篇
  2004年   110篇
  2003年   49篇
  2002年   38篇
  2001年   46篇
  2000年   161篇
  1999年   67篇
  1998年   58篇
  1997年   56篇
  1996年   29篇
  1995年   13篇
  1992年   29篇
  1991年   20篇
  1990年   13篇
  1989年   15篇
  1988年   14篇
  1987年   16篇
  1986年   10篇
  1985年   10篇
  1984年   11篇
  1983年   9篇
  1982年   8篇
  1981年   7篇
  1980年   14篇
  1979年   10篇
  1978年   8篇
  1976年   9篇
  1975年   7篇
  1973年   12篇
  1972年   10篇
  1966年   9篇
  1935年   6篇
排序方式: 共有9363条查询结果,搜索用时 125 毫秒
101.
102.
ABSTRACT

A novel compound, (R)-4-ethoxy-2-hydroxy-4-oxobutanoic acid (1), and six known compounds (27) were isolated from the fruiting bodies of the wild edible mushroom Leucopaxillus giganteus. The planar structure of 1 was determined by the interpretation of spectroscopic data analysis. The absolute configuration of 1 was determined by comparing specific rotation of the synthetic compounds. In the plant regulatory assay, the isolated compounds (17) and the chemically prepared compounds (810) were evaluated their biological activity against the lettuce (Lactuca sativa) growth. Compounds 1 and 310 showed the significant regulatory activity of lettuce growth. 1 showed the strongest inhibition activity among the all the compounds tested. In the lung cancer assay, all the compounds were assessed the mRNA expression of Axl and immune checkpoints (PD-L1, PD-L2) in the human A549 alveolar epithelial cell line by RT-PCR. Compounds 110 showed significant inhibition activity against Axl and/or immune checkpoint.  相似文献   
103.
Si ran Wang  Jia Yan  Bu er Ha  Yu’e Bai 《Phyton》2021,90(2):595-604
Hydrangea bretschneideri Dipp is a highly popular ornamental plant for garden decoration. Genetic engineering technology has been successfully used in many plant species, but it is limited in Hydrangea. Here we established an efficient regeneration system by using stem segments as explants for the first time. In our study, the plant growth regulators (PGRs) were evaluated at the different regeneration processes, including axillary shoots regeneration and root induction. We found that the optimal concentration for axillary buds’ induction was 2.0 mgL−1 6-BA and 0.5 mgL−1 1 IAA, its highest induction rate was 70%. Moreover, the highest axillary shoots proliferation coefficient was 10.7 on the Murashige and Skoog (MS) medium with 2.0 mgL−1 6-benzyladenine (BA), 0.2 mgL−1 indole-3-butyric acid (IBA), and 1.0 mgL−1 gibberellin A3 (GA3). The highest frequency of root induction was 80.0 ± 0.06% by culturing the elongated shoots in 1/2 MS medium containing 0.1 mgL−1 IBA. In summary, our study will provide an effective technology for large-scale propagation and important pathway for promoting the popularization and application of Hydrangea bretschneideri Dipp.  相似文献   
104.
Rhodiola quadrifida is a rare mountain medicinal plant whose root extracts are used in traditional Chinese medicine as a hemostatic, antitussive, and tonic in the treatment of gynecological diseases. The aim of the study was to obtain R. quadrifida cultures at different degrees of differentiation in vitro and compare their growth characteristics and the content of salidroside and rosavin. Hairy roots were obtained by incubating cotyledons and hypocotyls in a suspension of Agrobacterium rhizogenes strain A4. The presence of the rolB and rolC genes was proven by polymerase chain reaction. The obtained roots were cultivated in Murashige-Skoog medium (MS). Calluses were obtained from the hairy roots in MS medium with the addition of hormones: 3 mg/L 2,4 D and 0.5 mg/L BAP. The presence of the main secondary metabolites of R. quadrifida, salidroside and rosavin, in calluses and salidroside in hairy roots by HPLC/MS was confirmed. The content of salidroside in callus culture was significantly higher than in hairy roots, 0.158 and 0.047%, respectively. The content of rosavin in callus culture was 0.07%. The content of rosavin and salidroside in callus culture was close to the level of these substances in the rhizomes of R. quadrifida plants growing in vivo, making this culture promising for its possible biotechnological use.  相似文献   
105.
Journal of Ichthyology - In Lake Amut (the Verkhnyaya Angara drainage basin) the third population of Arctic charr Salvelinus alpinus (L.) in Baikal basin was found, a presumed invader from the Lena...  相似文献   
106.
Plant and Soil - Data about woody debris (WD) decomposition are very scarce for the Mediterranean basin. The specific aim of this work is to explore the relationships between WD traits with the...  相似文献   
107.
Journal of Ichthyology - Based on the morphological features, four rare alien species in the Kapchagai reservoir were identified: Coregonus peled, Parasalmo mykiss, Megalobrama mantschuricus, and...  相似文献   
108.
109.
Movement of Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) and lake sturgeon (A. fulvescens) in the St. Lawrence Estuary (Québec, Canada) are not fully understood. To assess the movement extent of both species, a mark–recapture study was conducted in collaboration with commercial fishermen operating in the St. Lawrence Estuary. Between 1981 and 2015, 3,367 Atlantic sturgeon (fork length 21.8–199.5 cm) and 3,180 lake sturgeon (fork length 17.8–190.8 cm) were tagged and released. Of these, 673 Atlantic sturgeon and 42 lake sturgeon were recaptured. The maximum distances traveled between capture and recapture locations were 1,307 km for Atlantic sturgeon (8 years after initial capture) and 252 km for lake sturgeon (less than 1 year after initial capture). Statistical analyses identified differences in the dispersal distance of both species as revealed by a first component characterized by individuals with short dispersal distances (98% and <35 km for Atlantic sturgeon; 58% and <1 km for lake sturgeon) and a second component characterized by individuals with longer dispersal distances (2% and >600 km for Atlantic sturgeon; 42% and >190 km for lake sturgeon). We suggest that the short dispersal distances detected in the vast majority of Atlantic sturgeon recaptures likely reflect strong site fidelity, highlighting the importance of the St. Lawrence Estuary as a preferred habitat for juveniles and subadults. Although recaptures were low for lake sturgeon because this species is only marginally targeted by commercial fishermen in the St. Lawrence Estuary, our results also showed that this species uses estuarine habitats and that half of the population seems to exhibit strong site fidelity (67% of individuals were recaptured within 2 km).  相似文献   
110.
Environmental Biology of Fishes - Cortisol is recognized as a physiological indicator of stress in fish. However, this hormone is typically measured in plasma samples. In this study, cortisol...  相似文献   
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