全文获取类型
收费全文 | 217篇 |
免费 | 28篇 |
国内免费 | 134篇 |
专业分类
379篇 |
出版年
2024年 | 3篇 |
2023年 | 13篇 |
2022年 | 10篇 |
2021年 | 17篇 |
2020年 | 22篇 |
2019年 | 20篇 |
2018年 | 12篇 |
2017年 | 10篇 |
2016年 | 10篇 |
2015年 | 18篇 |
2014年 | 22篇 |
2013年 | 21篇 |
2012年 | 31篇 |
2011年 | 26篇 |
2010年 | 15篇 |
2009年 | 23篇 |
2008年 | 25篇 |
2007年 | 14篇 |
2006年 | 13篇 |
2005年 | 9篇 |
2004年 | 4篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1960年 | 1篇 |
1950年 | 2篇 |
排序方式: 共有379条查询结果,搜索用时 15 毫秒
61.
辽西不同针叶被害率的油松冠层光谱特征 总被引:1,自引:0,他引:1
通过对辽宁西部大面积油松冠层反射光谱的测定,分析了不同针叶被害率的油松冠层光谱反射率的差异.结果表明:在可见光波段,健康植被和不同针叶被害率的油松冠层光谱均符合绿色植物的光谱特征,但针叶被害率大于60%的油松冠层的红谷不十分明显;在近红外波段,随着针叶被害率的减少,780~1350 nm波段范围的光谱反射率增大,1450~1800和1950 ~2350 nm波段范围的光谱反射率下降.随着针叶被害率的增加,红边拐点波长位置向短波方向移动,即出现“蓝移”现象.不同针叶被害率与红边特征参数和多种植被指数均具有显著或极显著的相关关系,其中,以DVI(1470,860)为参数所建模型能更好地监测油松冠层针叶被害率. 相似文献
62.
ABSTRACTAntioxidant enzymes are essential proteins that maintain cell proliferation potential by protecting against oxidative stress. They are present in many organisms including harmful algal bloom (HAB) species. We previously identified the antioxidant enzyme 2-Cys peroxiredoxin (PRX) in the raphidophyte Chattonella marina. This enzyme specifically decomposes a hydrogen peroxide (H2O2). PRX is the only antioxidant enzyme so far identified in C. marina. This study used mRNA-seq, using Trinity assemble and blastx for annotation, to identify a further five antioxidant enzymes from C. marina: Cu Zn superoxide dismutase (Cu/Zn-SOD), glutathione peroxidase (GPX), catalase (CAT), ascorbate peroxidase (APX) and thioredoxin (TRX). In the gene expression analysis of six enzymes (Cu/Zn-SOD, GPX, CAT, APX, TRX and PRX) using light-acclimated (100 μmol photons m?2 s?1) C. marina cells, only PRX gene expression levels were significantly increased by strong light irradiation (1000 μmol photons m?2 s?1). H2O2 concentration and scavenging activity were also increased and significantly positively correlated with PRX gene expression levels. In dark-acclimated cells, expression levels of all antioxidant enzymes except APX were significantly increased by light irradiation (100 μmol photons m?2 s?1). Expression decreased the following day, with the exception of PRX expression. With the exception of CAT, gene expression of antioxidant enzymes was not significantly induced by artificial H2O2 treatment, although average gene expression levels were slightly increased in some enzymes. Thus, we suggest that light is the main trigger of gene expression, but the resultant oxidative stress is also a possible factor affecting the gene expression of antioxidant enzymes in C. marina. 相似文献
63.
A new species of the genus Leptolalax is described from Doi Saket, Chiang Mai Province, northern Thailand. The new species is distinguished from its congeners by the following combination of characters: 1) adult size large(male SVL 45.8-52.5 mm); 2) tympanum distinct; 3) skin of dorsal surface mostly smooth, with distinct tubercles on dorsal and lateral parts of the body; 4) ventrolateral glandular ridge distinct and complete; 5) lateral body and groin covered with dark brown or black spots; 6) throat, chest, and belly nearly immaculate white; and 7) bi-colored iris, upper onethird golden, and lower two-thirds gray. Molecular phylogenetic analysis of mitochondrial 16S rRNA further distinguishes it from its congeners for which sequences are available. 相似文献
64.
目的:探讨RhoA在人脑星形细胞瘤中表达与肿瘤病理分级的关系.方法:免疫组化ABC法检测RhoA在80例人脑星形细胞瘤和10例正常脑组织标本中的表达并进行分析.结果:在正常脑组织中未见RhoA表达.RhoA在人脑星形细胞瘤的表达阳性率及免疫反应评分(IRS)分剐为56.25%、1.76±1.71.Ⅰ-Ⅳ级星形细胞瘤RhoA表达阳性率分别为35%(7/20)、45%(9/20)、65%(13/20)、80%(16/20).Ⅰ-Ⅳ级脑星形细胞瘤中RhoA IRS分别为0.78 1.05、1.12 1.04、2.15:1:1.59、3.31±2.14.结论:RhoA在人脑星形细胞瘤中高表达,且随着星形细胞瘤病理级别的增高而表达增强,RhoA在脑星形细胞瘤的发生过程中具有重要作用. 相似文献
65.
Zheng?Fu Rong?Lu Guoli?Li Lan?Zhao Weizhen?Gao Xuchun?Che Xu?Jian Chunlei?Zhou Zhi?YaoEmail author 《中国科学C辑(英文版)》2005,48(5):523-530
This study aimed to observe the effects of tyroserleutide (tyrosyl-seryl-leucine, YSL) on the growth of human hepatocarcinoma
BEL-7402 that was transplanted into nude mice, and explore its anti-tumor mechanism preliminarily. YSL, at doses of 80 μg-kg-1 · d-1, 160 μg·kg-1 ·d-1 and 320 μg · kg-1 · d-1 significantly inhibited the growth of the human hepatocarcinoma BEL-7402 tumor in nude mice, producing inhibition of 21.66%,
41.34%, and 34.78%, respectively. Ultra structure of BEL-7402 tumor in nude mice showed that YSL could induce tumor cells
apoptosis and necrosis, cell organelle mitochondria and endoplasmic reticulum damage, and calcium overload. By confocal laser
scanning microscopy and flow cytometry, we found that 10 μg/mL YSL rapidly induced an increase of the concentration of cytoplasmic
free calcium in BEL-7402 cells in vitro, and maintained high concentrations of cytoplasmic free calcium for 1 h. Then the calcium concentration began to decrease
after 2 h, and was lower than that of the control group at 4 h and 24 h (P< 0.05). YSL also decreased the mitochondrial transmembrane potential of BEL-7402 cells in vitro, but had no effect on the calcium homeostasis or mitochondrial transmembrane potential of Chang liver hepatocytes. So affecting
calcium homeostasis, then inducing apoptosis and necrosis may be a mechanism by which YSL inhibits the tumor growth in animal
model. 相似文献
66.
67.
Tyroserleutide tripeptide affects calcium homeostasis of human hepatocarcinoma BEL-7402 cells 总被引:1,自引:0,他引:1
FU Zheng LU Rong LI Guoli ZHAO Lan GAO Weizhen CHE Xuchun JIAN Xu ZHOU Chunlei & YAO Zhi . Department of Immunology Tianjin Medical University Tianjin China . Shenzhen Kangzhe Pharmaceutical Co. Ltd. Shenzhen China . Department of Pharmacy Tianjin Medical University Tianjin China . Central Laboratory of Tianjin Medical University Hospital Tianjin China 《中国科学:生命科学英文版》2005,48(5):523-530
Copyright by Science in China Press 2005 Primary hepatocarcinoma is one of the most fre-quent digestive-tract cancers, particularly in China. The incidence and death rate of primary hepatocarci-noma in China is the highest in the world, with about 1100 thousands people dying from primary hepatocar-cinoma per year[1]. Although the chemotherapeutic agents are the main therapeutic approach for hepato- carcinoma, they are relatively ineffective and result in many toxic and side effects. Accordin… 相似文献
68.
一种鸡胚胎心率记录的新方法 总被引:1,自引:0,他引:1
鸡胚胎是一种被广泛应用于发育生物学研究的实验材料。在以鸡胚胎为动物模型的各项研究工作中,心率常被看作是一个很重要的反应胚胎生理活动指标。本文详细介绍了一种侵入性的心电记录新方法,在正常的生理条件下通过记录鸡胚胎心电的变化来监测心率。首先在蛋壳上钻孔,将电极插入蛋内,然后通过放大器放大,A/D板转换,将心电信号输入电脑进行分析处理,提取与心率相关的信息。这种记录方式对胚胎损伤较小,不影响胚胎的正常发育;具有灵敏度高,操作简单,容易掌握等特点。 相似文献
69.
70.