全文获取类型
收费全文 | 394篇 |
免费 | 20篇 |
专业分类
林业 | 8篇 |
基础科学 | 5篇 |
36篇 | |
综合类 | 175篇 |
农作物 | 14篇 |
水产渔业 | 21篇 |
畜牧兽医 | 150篇 |
园艺 | 1篇 |
植物保护 | 4篇 |
出版年
2018年 | 8篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 4篇 |
2013年 | 8篇 |
2012年 | 9篇 |
2011年 | 18篇 |
2010年 | 5篇 |
2009年 | 9篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 10篇 |
2005年 | 8篇 |
2004年 | 10篇 |
2003年 | 8篇 |
2002年 | 13篇 |
2001年 | 5篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1994年 | 3篇 |
1992年 | 4篇 |
1991年 | 12篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1974年 | 4篇 |
1972年 | 3篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1963年 | 3篇 |
1923年 | 6篇 |
1922年 | 16篇 |
1921年 | 25篇 |
1920年 | 22篇 |
1919年 | 15篇 |
1916年 | 5篇 |
1915年 | 7篇 |
1914年 | 4篇 |
1913年 | 4篇 |
1912年 | 3篇 |
1911年 | 3篇 |
1910年 | 3篇 |
1909年 | 6篇 |
排序方式: 共有414条查询结果,搜索用时 0 毫秒
411.
Hogg AE Parsons K Taylor G Worth A Beverley P Howard CJ Villarreal-Ramos B 《Veterinary immunology and immunopathology》2011,140(1-2):47-54
Evaluation of the changes induced by immunological interventions requires a baseline against which to compare those changes. The age-related changes in the CD8(+) T-cell population of cattle were studied. The results indicate that CD8(+) T-cells could be divided into γ/δ TCR1(+) and γ/δ TCR1(-) according to their expression of the γ/δ T-cell receptor. As a proportion, the CD8(+) γ/δ TCR1(+) population appears to increase with age. Within the CD8(+)γ/δ TCR1(-) a population of cells expressing a profile of surface molecules previously associated with effector memory T cells (CD45RO(+), CD62L(-), CD27(-), CD45RA(-) and CD28(-)) increases with age. Furthermore, a parallel increase with age in the proportion of CD8(+)CD45RO(+) T cells that express the cytotoxic granule protein perforin was observed. In peripheral tissues, namely lungs, it was found that the majority of CD8(+) T cells present expressed a phenotype indicative of previously primed T cells (high expression of CD45RO and perforin). In contrast, only a small population of memory CD8(+) T cells was present in lymphoid tissue where most of the CD8(+) T cells expressed a na?ve phenotype. In conclusion, in cattle, like in human, CD8(+) T cells that express a phenotype associated with antigen experience accumulate with age that may play a role in immunocompetence as the individual ages. 相似文献
412.
Parsons DW Li M Zhang X Jones S Leary RJ Lin JC Boca SM Carter H Samayoa J Bettegowda C Gallia GL Jallo GI Binder ZA Nikolsky Y Hartigan J Smith DR Gerhard DS Fults DW VandenBerg S Berger MS Marie SK Shinjo SM Clara C Phillips PC Minturn JE Biegel JA Judkins AR Resnick AC Storm PB Curran T He Y Rasheed BA Friedman HS Keir ST McLendon R Northcott PA Taylor MD Burger PC Riggins GJ Karchin R Parmigiani G Bigner DD Yan H Papadopoulos N Vogelstein B Kinzler KW Velculescu VE 《Science (New York, N.Y.)》2011,331(6016):435-439
Medulloblastoma (MB) is the most common malignant brain tumor of children. To identify the genetic alterations in this tumor type, we searched for copy number alterations using high-density microarrays and sequenced all known protein-coding genes and microRNA genes using Sanger sequencing in a set of 22 MBs. We found that, on average, each tumor had 11 gene alterations, fewer by a factor of 5 to 10 than in the adult solid tumors that have been sequenced to date. In addition to alterations in the Hedgehog and Wnt pathways, our analysis led to the discovery of genes not previously known to be altered in MBs. Most notably, inactivating mutations of the histone-lysine N-methyltransferase genes MLL2 or MLL3 were identified in 16% of MB patients. These results demonstrate key differences between the genetic landscapes of adult and childhood cancers, highlight dysregulation of developmental pathways as an important mechanism underlying MBs, and identify a role for a specific type of histone methylation in human tumorigenesis. 相似文献
413.
Kwong LS Parsons R Patterson R Coffey TJ Thonur L Chang JS Russell G Haig D Werling D Hope JC 《Veterinary immunology and immunopathology》2011,139(2-4):313-318
Host recognition of conserved pathogen-associated molecular patterns (PAMPs) and their interactions with pattern-recognition receptors, including the Toll-like receptors (TLR) is essential for innate immune response induction. The TLR1 family (TLR1, 2, 6 and 10) is involved in the recognition of gram-positive and gram-negative bacteria and heterodimers of TLR1 or TLR6 with TLR2 are crucial for the identification of several PAMPs. Studies on cell surface expression of TLR in ruminants are hampered by the lack of specific antibodies and no convincingly cross-reactive anti-human antibodies have been described so far. We describe herein four antibodies which recognise bovine TLR2. Differences in TLR2 expression were evident on bovine antigen presenting cells with high level expression on peripheral blood monocytes and monocyte-derived macrophages. Lower levels of expression were evident on dendritic cell populations derived in vitro and ex vivo, and on alveolar macrophages. One of the antibodies recognised TLR2 expression on ovine peripheral blood monocytes. The identification of antibodies specific for bovine and ovine TLR2 will facilitate studies of the role of this important PRR in the initiation of immune responses to important pathogens. 相似文献
414.
Paleosolic features are important to land use and management of soils on fan terraces in southwestern Oregon. Soil-geomorphology studies identified relict duripans and established the distribution of associated Durochrepts, Duraquolls and Argixerolls. These soils represent two late Pleistocene geomorphic surfaces, each with distinct kinds of periglacial patterned ground. Soil behavior is discussed in terms of soil characteristics and qualities and compared for cropland, grazing, construction, and waste disposal. 相似文献