全文获取类型
收费全文 | 483篇 |
免费 | 24篇 |
国内免费 | 109篇 |
专业分类
616篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 21篇 |
2021年 | 17篇 |
2020年 | 27篇 |
2019年 | 27篇 |
2018年 | 18篇 |
2017年 | 14篇 |
2016年 | 22篇 |
2015年 | 12篇 |
2014年 | 24篇 |
2013年 | 31篇 |
2012年 | 33篇 |
2011年 | 28篇 |
2010年 | 23篇 |
2009年 | 24篇 |
2008年 | 13篇 |
2007年 | 20篇 |
2006年 | 24篇 |
2005年 | 21篇 |
2004年 | 25篇 |
2003年 | 15篇 |
2002年 | 27篇 |
2001年 | 18篇 |
2000年 | 22篇 |
1999年 | 15篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 11篇 |
1995年 | 9篇 |
1994年 | 13篇 |
1993年 | 5篇 |
1992年 | 11篇 |
1991年 | 2篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有616条查询结果,搜索用时 0 毫秒
51.
Cindy Q. Tang Yongchuan Yang Arata Momohara Huan-Chong Wang Hong Truong Luu Shuaifeng Li Kun Song Shenhua Qian Ben LePage Yi-Fei Dong Peng-Bin Han Masahiko Ohsawa Buu Thach Le Huu Dang Tran Minh Tri Dang Ming-Chun Peng Chong-Yun Wang 《Plant Diversity》2019,(4):237-249
The Chinese water pine Glyptostrobus pensilis is the sole surviving species of the genus Glyptostrobus. It is endemic to southern China, central Vietnam, and eastern Laos, and today it is nearly extinct in the wild. Forest community characteristics and population structure of G. pensilis in China have remained un-known up to now. We investigated six swamp forest stands and analyzed their forest community characteristics (i.e. vertical stratification, species composition, and diversity) and population structure, including the frequency distribution of DBH (diameter at breast height) and age-classes as found in Fujian Province, southeastern China. The vertical stratifications of all the forest stands were rather simple. The remaining wild specimens ranged from roughly 15 to some 357 years for an average of ca. 85 years, with only a few individuals less than 20 years old. Compared with the stands and populations of G. pensilis in Vietnam, the taxonomic compositions of the stands in the two regions were different, except for the dominant species-G. pensilis. The Shannon-Wiener index showed the overstory of each stand had much lower diversity (0.26 on average) in Fujian Province than that (1.97 on average) in Vietnam, whereas the diversity indices were about the same (around 2.41) for the understories in the two regions. Furthermore, we discovered 18 G. pensilis seedlings at the study sites in Fujian Province. This discovery demonstrates that G. pensilis regeneration is extremely poor and its populations are declining, although these populations are rela-tively healthier than those in Vietnam. 相似文献
52.
53.
描述了中国福建蜂斗草属(野牡丹科)一新种,即三脉蜂斗草(Sonerila trinervis Q.W.Lin)。本新种与直立蜂斗草(Sonerila erecta Jack)相似,区别在于本种的茎圆柱形,无翅,有卷曲的微柔毛;叶面被极细的微柔毛,仅具基部3出脉;花瓣白色,近圆形,直径约2 mm;雄蕊长约2.5 mm,花药长约1 mm,易于区别。 相似文献
54.
云南景颇族的体质特征 总被引:7,自引:10,他引:7
本文调查了云南景颇族261人(男105人,女156人)。年龄为成年人(男24-60岁,女23-55岁)。主要测量均值与现代中国汉族和云南省各少数民族比较和聚类分析的结果表明,景颇族属黄种人的东亚类型,但也有南亚类型特征表现。体质特征与傣族、哈尼族和彝族接近,与基诺族和布郎族较远。 相似文献
55.
Xuejun Zhang Shengliang Ye Xi Du Jing Yuan Chaoming Zhao Changqing Li 《Biologicals》2013,41(6):364-367
In 2007, the Chinese State Food and Drug Administration (SFDA) implemented a management system for lot release of all plasma-derived products. Since then, there have been only a few systematic studies of the blood supply, which is a concern when considering the small amount of plasma collected per capita (approximately 3 L/1000 people). As a result, there may be a threat to the safety of the available blood supply. In this study, we examined the characteristics of the supply of Chinese plasma-derived products. We investigated the reports of lot-released biological products derived from all 8 national or regional regulatory authorities in China from 2007 to 2011. The market supply characteristics of Chinese plasma-derived products were analyzed by reviewing the changes in supply varieties, the batches of lot-released plasma-derived products and the actual supply. As a result, the national regulatory authorities can more accurately develop a specific understanding of the production and quality management information provided by Chinese plasma product manufacturers. The implementation of the lot release system further ensures the clinical validity of the plasma-derived products in China and improves the safety of using plasma-derived products. This work provides an assessment of the future Chinese market supply of plasma-derived products and can function as a theoretical basis for the establishment of hemovigilance. 相似文献
56.
对台湾海峡西北部平潭岛海域337个站位表层沉积物中底栖有孔虫进行分析鉴定,结果表明底栖有孔虫丰度、分异度变化较大,所出现的属种类型以玻璃质壳体为主,其次为瓷质壳,胶结壳最少。底栖有孔虫分布受水深、盐度、底质类型、底流和沿岸上升流等因素共同影响。应用‘PAST’软件的因子分析结果表明,该海域底栖有孔虫可划分为四个组合:组合Ⅰ(Hanzawaia-Pseudorotalia-Bolivina)主要分布于水深大于20m的深水区,受水深和底流影响明显;组合Ⅱ(Ammonia beccarii-Elphidiumspp.)主要分布于近岸浅水环境;组合Ⅲ(Quinqueloculina-Ammonia annectens-Spiroloculina)主要分布于海湾内高盐度区,推测受到沿岸上升流影响;组合Ⅳ(Elphidium advenum-Ammonia annectens)分布于组合Ⅰ与组合Ⅲ之间的局部区域,可能受浙闽沿岸流影响较强。 相似文献
57.
报道一种福建新记录野生植物--心叶毛蕊茶Camellia cordifolia (Metc.) Nakai。凭证标本存放于福建农林大学林学院树木标本室(FJFC)。 相似文献
58.
Shifting Quaternary migration patterns in the Bahamian archipelago: Evidence from the Zamia pumila complex at the northern limits of the Caribbean island biodiversity hotspot 下载免费PDF全文
59.
Ricardo Villalba 《Biotropica》2011,43(1):41-49
In this study, we use tree‐ring records to determine the climate factors controlling the growth of Centrolobium microchaete, a high‐value timber species from the tropical dry Chiquitano forest in Bolivia. We present the first tree‐ring chronologies from C. microchaete for Concepción and Santa Mónica, Bolivia. Statistical analyses show that the chronologies are of good quality and have a significant common signal between trees. The growth of C. microchaete is strongly influenced by climatic conditions during late spring–early summer. Abundant precipitations concurrent with below‐average temperatures during this period of the year favor tree growth. Climate variations in late spring–early summer explain >40 percent of the total variance in C. microchaete tree growth during the interval 1943–2005. Minor differences in tree responses to climate recorded between the two stands may reflect differences in the extent of the dry season and in soil water capacity between sites. Although the chronologies cover the past 180 yr, adding samples from older individuals would permit the extension of these records further back in time. The strong climate dependency of tree growth suggests that predicted future climate changes in the region could have a significant influence on C. microchaete tree growth during the 21st century. 相似文献
60.