全文获取类型
收费全文 | 93篇 |
免费 | 8篇 |
国内免费 | 2篇 |
专业分类
林业 | 4篇 |
农学 | 2篇 |
4篇 | |
综合类 | 31篇 |
农作物 | 3篇 |
水产渔业 | 2篇 |
畜牧兽医 | 54篇 |
植物保护 | 3篇 |
出版年
2023年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 2篇 |
2011年 | 8篇 |
2010年 | 6篇 |
2009年 | 6篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1964年 | 2篇 |
1963年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有103条查询结果,搜索用时 984 毫秒
1.
2.
Monicah Mucheru-Muna Daniel Mugendi James Kung’u Jayne Mugwe Andre Bationo 《Agroforestry Systems》2007,69(3):189-197
Soil nutrient depletion as a result of continuous cultivation of soils without adequate addition of external inputs is a major
challenge in the highlands of Kenya. An experiment was set up in Meru South District, Kenya in 2000 to investigate the effects
of different soil-incorporated organic (manure, Tithonia diversifolia, Calliandra calothyrsus, Leucaena leucocephala) and mineral fertilizer inputs on maize yield, and soil chemical properties over seven seasons. On average, tithonia treatments
(with or without half recommended rate of mineral fertilizer) gave the highest grain yield (5.5 and 5.4 Mg ha−1 respectively) while the control treatment gave the lowest yield (1.5 Mg ha−1). After 2 years of trial implementation, total soil carbon and nitrogen contents were improved with the application of organic
residues, and manure in particular improved soil calcium content. Results of the economic analysis indicated that on average
across the seven seasons, tithonia with half recommended rate of mineral fertilizer treatment recorded the highest net benefit
(USD 787 ha−1) while the control recorded the lowest (USD 272 ha−1). However, returns to labor or benefit-cost ratios were in most cases not significantly improved when organic materials were
used. 相似文献
3.
JI Yun HJ Park MH Park MS Kim JH Choi E Lee SP Gong JM Lim ST Lee 《Reproduction in domestic animals》2014,49(5):705-710
Recently, isolation and in vitro culture of putative spermatogonial stem cells (SSCs) in the domestic cat have been conducted. However, the cellular niche conditions that facilitate the establishment and long‐term maintenance of feline SSCs (FSSCs) have not been described. Therefore, we investigated the type of feeder cells used to stimulate colony formation and growth of FSSCs among the various factors in the FSSC niche. Spermatogonial stem cells isolated from feline testes were cultured on mitotically inactivated testicular stromal cells (TSCs) derived from cats, dogs and mice, and mouse embryonic fibroblasts (MEFs). The formation and growth of colonies derived from SSCs cultured on each type of feeder cell were identified at passage 0, and the morphology, alkaline phosphatase (AP) activity and expression of SSC‐specific genes in surviving colonies were investigated at passage 4. Among these diverse feeder cells, TSCs from cat showed the greatest colony formation, growth and maintenance of FSSCs, and SSC colonies cultured by passage 4 showed a typical dome‐shaped morphology, AP activity and expression of SSC‐specific genes (NANOG, OCT4, SOX2 and CD9). Accordingly, these results demonstrate that feline TSCs could be used as feeder cells to support the establishment and maintenance of SSCs from domestic cats. 相似文献
4.
Analysis of the subunit polypeptide composition of Fraction 1 proteins gives information on the expression of both nuclear and chloroplast genomes; the large subunits of the protein are coded by chloroplast DNA, whereas the small subunits are coded by nuclear DNA. Fraction 1 protein isolated from the leaves of parasexual hybrid plants derived from the fusion of protoplasts of Nicotiana glauca and N. langsdorffii contains the small subunit polypeptides of both parent species and the large subunit polypeptides of only N. glauca. Fraction 1 protein isolated from the leaves of a hybrid plant obtained after the uptake of chloroplasts of N. suaveolens by protoplasts of white tissue of a variegating mutant of N. tabacum contains the large subunit polypeptides of both N. suaveolens and N. tabacum, as well as the small subunit polypeptides of both these species. 相似文献
5.
Steed PM Tansey MG Zalevsky J Zhukovsky EA Desjarlais JR Szymkowski DE Abbott C Carmichael D Chan C Cherry L Cheung P Chirino AJ Chung HH Doberstein SK Eivazi A Filikov AV Gao SX Hubert RS Hwang M Hyun L Kashi S Kim A Kim E Kung J Martinez SP Muchhal US Nguyen DH O'Brien C O'Keefe D Singer K Vafa O Vielmetter J Yoder SC Dahiyat BI 《Science (New York, N.Y.)》2003,301(5641):1895-1898
Tumor necrosis factor (TNF) is a key regulator of inflammatory responses and has been implicated in many pathological conditions. We used structure-based design to engineer variant TNF proteins that rapidly form heterotrimers with native TNF to give complexes that neither bind to nor stimulate signaling through TNF receptors. Thus, TNF is inactivated by sequestration. Dominant-negative TNFs represent a possible approach to anti-inflammatory biotherapeutics, and experiments in animal models show that the strategy can attenuate TNF-mediated pathology. Similar rational design could be used to engineer inhibitors of additional TNF superfamily cytokines as well as other multimeric ligands. 相似文献
6.
Kochendoerfer GG Chen SY Mao F Cressman S Traviglia S Shao H Hunter CL Low DW Cagle EN Carnevali M Gueriguian V Keogh PJ Porter H Stratton SM Wiedeke MC Wilken J Tang J Levy JJ Miranda LP Crnogorac MM Kalbag S Botti P Schindler-Horvat J Savatski L Adamson JW Kung A Kent SB Bradburne JA 《Science (New York, N.Y.)》2003,299(5608):884-887
We report the design and total chemical synthesis of "synthetic erythropoiesis protein" (SEP), a 51-kilodalton protein-polymer construct consisting of a 166-amino-acid polypeptide chain and two covalently attached, branched, and monodisperse polymer moieties that are negatively charged. The ability to control the chemistry allowed us to synthesize a macromolecule of precisely defined covalent structure. SEP was homogeneous as shown by high-resolution analytical techniques, with a mass of 50,825 +/-10 daltons by electrospray mass spectrometry, and with a pI of 5.0. In cell and animal assays for erythropoiesis, SEP displayed potent biological activity and had significantly prolonged duration of action in vivo. These chemical methods are a powerful tool in the rational design of protein constructs with potential therapeutic applications. 相似文献
7.
Mullen AC High FA Hutchins AS Lee HW Villarino AV Livingston DM Kung AL Cereb N Yao TP Yang SY Reiner SL 《Science (New York, N.Y.)》2001,292(5523):1907-1910
How cytokines control differentiation of helper T (TH) cells is controversial. We show that T-bet, without apparent assistance from interleukin 12 (IL-12)/STAT4, specifies TH1 effector fate by targeting chromatin remodeling to individual interferon-gamma (IFN-gamma) alleles and by inducing IL-12 receptor beta2 expression. Subsequently, it appears that IL-12/STAT4 serves two essential functions in the development of TH1 cells: as growth signal, inducing survival and cell division; and as trans-activator, prolonging IFN-gamma synthesis through a genetic interaction with the coactivator, CREB-binding protein. These results suggest that a cytokine does not simply induce TH fate choice but instead may act as an essential secondary stimulus that mediates selective survival of a lineage. 相似文献
9.
Walensky LD Kung AL Escher I Malia TJ Barbuto S Wright RD Wagner G Verdine GL Korsmeyer SJ 《Science (New York, N.Y.)》2004,305(5689):1466-1470
BCL-2 family proteins constitute a critical control point for the regulation of apoptosis. Protein interaction between BCL-2 members is a prominent mechanism of control and is mediated through the amphipathic alpha-helical BH3 segment, an essential death domain. We used a chemical strategy, termed hydrocarbon stapling, to generate BH3 peptides with improved pharmacologic properties. The stapled peptides, called "stabilized alpha-helix of BCL-2 domains" (SAHBs), proved to be helical, protease-resistant, and cell-permeable molecules that bound with increased affinity to multidomain BCL-2 member pockets. A SAHB of the BH3 domain from the BID protein specifically activated the apoptotic pathway to kill leukemia cells. In addition, SAHB effectively inhibited the growth of human leukemia xenografts in vivo. Hydrocarbon stapling of native peptides may provide a useful strategy for experimental and therapeutic modulation of protein-protein interactions in many signaling pathways. 相似文献
10.
Distributions of the vector Culicoides brevitarsis Kieffer (Diptera: Ceratopogonidae) (determined from light trap data) and 2 arboviruses (determined from seroconversions in sentinel cattle) were studied in eastern New South Wales in 1993–94. C brevitarsis was recorded progressively from endemic areas on the north coast, to Nowra on the south coast, and westward to Scone, in the Hunter Valley. C brevitarsis also survived through winter at Paterson, in the Hunter Valley. Its apparently focal reappearance in this marginal area had no obvious effect on the broad pattern of its progression or the dispersal of Akabane and bluetongue viruses. These viruses were first recorded from foci near Coffs Harbour, on the mid-north coast. Their first occurrences at different locations were associated with those of C brevitarsis, but not with each other. The viruses were found only within the recorded limits of the vector's distribution. Delays between the initial occurrence of C brevitarsis and first evidence of virus transmissions at locations ranged from 2 to 7 months. The delays decreased away from the points of focus and were negatively associated with the time of initial occurrence of the vector. Seroconversions to the viruses were related to the presence of C brevitarsis. However, the densities of C brevitarsis had no apparent effect on the initial numbers of cattle seroconverting to either virus. The results support the conclusion that the progressions of C brevitarsis and Akabane and bluetongue viruses were the result of gradual movements by the vector. 相似文献