全文获取类型
收费全文 | 4885篇 |
免费 | 540篇 |
国内免费 | 807篇 |
专业分类
6232篇 |
出版年
2024年 | 29篇 |
2023年 | 139篇 |
2022年 | 206篇 |
2021年 | 327篇 |
2020年 | 247篇 |
2019年 | 315篇 |
2018年 | 247篇 |
2017年 | 184篇 |
2016年 | 295篇 |
2015年 | 365篇 |
2014年 | 428篇 |
2013年 | 453篇 |
2012年 | 471篇 |
2011年 | 465篇 |
2010年 | 279篇 |
2009年 | 222篇 |
2008年 | 269篇 |
2007年 | 194篇 |
2006年 | 164篇 |
2005年 | 122篇 |
2004年 | 120篇 |
2003年 | 118篇 |
2002年 | 110篇 |
2001年 | 78篇 |
2000年 | 54篇 |
1999年 | 58篇 |
1998年 | 36篇 |
1997年 | 40篇 |
1996年 | 26篇 |
1995年 | 20篇 |
1994年 | 22篇 |
1993年 | 24篇 |
1992年 | 22篇 |
1991年 | 17篇 |
1990年 | 20篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1950年 | 1篇 |
排序方式: 共有6232条查询结果,搜索用时 7 毫秒
11.
Xu Jiliang Zhang Xiaohui Zhang Zhengwang Zheng Guangmei Ruan Xiangfeng Zhang Keyin Xi Bo 《Frontiers of Biology in China》2006,1(2):174-181
Home range and habitat use of male Reeves’s pheasant (Syrmaticus reevesii) were studied during winter of 2001∼2002 and 2002∼2003 in the Dongzhai National Nature Reserve, Henan Province. Results from
five individuals of Reeves’s pheasant with over 30 relocations, indicated that the average size of home range was 10.03 ±
1.17 hm2 by Minimum Convex Polygon method, 8.60 ± 0.35 hm2 by 90% Harmonic Mean Transformation method, and 9.50 ± 1.90 hm2 by 95% Fixed Kernel method. It was observed that the winter range is smaller than that in the breeding season. The mean core
area of the home range was found to be 1.88 ± 0.37 hm2. Although the habitat composition of the core area varied greatly for individuals, a large part of the habitats used were
composed of confier and broadleaf mixed forests, masson pine forests, fir forests, and shrubs. Habitat use within the study
area was non-random, while habitats within home ranges were randomly used. Habitat use was dictated by tree diameter at breast
height, shrub height and coverage at 2.0 m. The proximity between forests and shrubs were also found to be important in providing
refuge for the birds during winter. Recommendations for conservation management include protecting the existing habitats in
Dongzhai National Nature Reserve, increasing suitable habitat for Reeves’s Pheasant through artificial plantations (e.g. firs),
and restoring some parts of the large shrub area into forests.
__________
Translated from Biodiversity Science, 2005, 13 (5) [译自: 生物多样性, 2005,13(5)] 相似文献
12.
Li M Liu L Xi N Wang Y Dong Z Tabata O Xiao X Zhang W 《Biochemical and biophysical research communications》2011,(2):689-694
The topography and mechanical properties of single B-lymphoma cells have been investigated by atomic force microscopy (AFM). With the assistance of microfabricated patterned pillars, the surface topography and ultrastructure of single living B-lymphoma cell were visualized by AFM. The apoptosis of B-lymphoma cells induced by rituximab alone was observed by acridine orange/ethidium bromide (AO/EB) double fluorescent staining. The rituximab-induced changes of mechanical properties in B-lymphoma cells were measured dynamically and the results showed that B-lymphoma cells became dramatically softer after incubation with rituximab. These results can improve our understanding of rituximab’effect and will facilitate the further investigation of the underlying mechanisms. 相似文献
13.
Man Yu Yanfang Wan Yanwei Xi 《Biochemical and biophysical research communications》2009,390(3):447-450
Somatic mutations and polymorphisms in the noncoding displacement (D)-loop of mitochondrial DNA (mtDNA) are present in a variety of human cancers. To investigate whether Ewing’s sarcoma (EWS) harbors genetic alterations within the D-loop region and their potential association with EWS carcinogenesis, we analyzed and compared the complete mtDNA D-loop sequences from 17 pairs of tumor tissues and corresponding peripheral blood samples using the direct DNA sequencing method. Our results revealed that 12 of the 17 EWS tumor specimens (70.6%) carried 19 somatic mutations in the D-loop of mtDNA, including 11 single-base substitutions, 3 insertions and 5 deletions. Among the tested 17 patients, we screened a total of 40 germline polymorphisms including one novel sequence variant in the D-loop fragment. Most of these identified mutations and germline variations were clustered within two hypervariable segments (HVS1 and HVS2) as well as the homopolymeric C stretch between nucleotide position 303 and 309. In addition, there was no significant correlation between mtDNA D-loop mutations and various clinicopathological factors of EWS. In conclusion, our study reports for the first time that mtDNA D-loop mutations occur at a high frequency in EWS. These data provide evidence of mtDNA alterations’ possible involvement in the initiation and/or progression of this rare malignancy. 相似文献
14.
15.
The inhibition of lung cancer cell growth by intracellular immunization with LC—1 ScFv 总被引:2,自引:0,他引:2
INTRODUCTIONLung cancer remains the leading cause of can-cer mortaIity in the world, accounting for more thanone sixth of cancer deaths in the world[1]. Antibod-ies have been proved to be a powerful tool fOr thestudy of 1ung cancer. A monoclonal IgM antibody,LC-1, was obtained in our laboratory. It can reactat a high rate with all four pathological types of lungcancers, including lung adenocarcinoma, 1ung squamous carcinoma, large cell lung cancer and smaIlcell lung cancert but not wit… 相似文献
16.
用10科11种双子叶植物的营养器官,在含1mg/L 2,4—D的MS固体培养基上诱导形成愈伤组织。取其生长旺盛的区域进行原生质体游离,并采用未经处理的相应植物的新鲜叶或茎作对照。研究结果表明,蜗牛酶对愈伤组织的原生质体游离具有明显的促进作用,而对照却无此效应。还研究了两种植物愈伤组织的继代天数和不同的酶组合对原生质体游离的影响。 相似文献
17.
达乌尔黄鼠冷暴露、冬眠及激醒时的外周甲状腺激素水平变化 总被引:4,自引:0,他引:4
探讨了达乌尔黄鼠在冷暴露、冬眠及激醒时的外周甲状腺激素水平变化和激素代谢。达乌尔黄鼠在非冬眠季节 ( 7~ 8月 )冷暴露 ( 4℃± 2℃ ) 1天 ,导致血清T3和T4浓度迅速增加 ,T3/T4不变 ;经 4周冷驯化后 ,T3维持在高水平上 ,T4降低 ,T3/T4增加 ,外周组织中的T4脱碘酶活性升高。表明冬眠动物与非冬眠动物的甲状腺机能及其激素代谢的冷适应性调节一致。在冬眠季 ( 12~ 1月 )的冬眠和激醒过程中 ,外周组织的T4脱碘酶活性、血清T3和T4水平比常温达乌尔黄鼠的高 ,显著高于夏季的水平 ,T3/T4不变。表明达乌尔黄鼠甲状腺机能及其激素水平存在季节性变化。 相似文献
18.
20.
以苯乙晴为原料,经水解、氯甲基化、取代、还原四步反应制得盐酸4-(β-氨乙基)苯乙酸。并对文献方法进行了改进。 相似文献