全文获取类型
收费全文 | 263篇 |
免费 | 20篇 |
国内免费 | 8篇 |
专业分类
林业 | 18篇 |
农学 | 12篇 |
基础科学 | 7篇 |
52篇 | |
综合类 | 52篇 |
农作物 | 19篇 |
水产渔业 | 23篇 |
畜牧兽医 | 82篇 |
园艺 | 7篇 |
植物保护 | 19篇 |
出版年
2023年 | 2篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 11篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 5篇 |
2014年 | 9篇 |
2013年 | 11篇 |
2012年 | 12篇 |
2011年 | 18篇 |
2010年 | 15篇 |
2009年 | 7篇 |
2008年 | 13篇 |
2007年 | 12篇 |
2006年 | 16篇 |
2005年 | 13篇 |
2004年 | 11篇 |
2003年 | 8篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1965年 | 1篇 |
1964年 | 4篇 |
1963年 | 4篇 |
排序方式: 共有291条查询结果,搜索用时 31 毫秒
91.
Summary Electronmicroscope microanalyser (EMMA-4) analysis of Poria monticola colonising pine wood treated with a copper-chrome-arsenate preservative has shown that the fungus removes copper chromium and arsenic from the wood and stores these elements within the hyphae to the extent of 3–4% on a mycelial dry weight basis. The total uptake of each element varies from spot to spot examined (each 0.2 m dia.) but is on an average correlated with the concentration of the element in the impregnated wood. It appears that the rate of copper uptake is higher than of arsenic uptake. 相似文献
92.
FM Rodríguez M Colombero AN Amweg E Huber NC Gareis NR Salvetti HH Ortega F Rey 《Reproduction in domestic animals》2015,50(4):659-668
Cystic ovarian disease (COD) is one of the main causes of infertility in dairy cattle. It has been shown that intra‐ovarian factors, such as members of the insulin‐like growth factor (IGF) system, may contribute to follicular persistence. The bioavailability of IGF to initiate its response by binding to specific receptors (IGFRs) depends on interactions with related compounds, such as pregnancy‐associated plasma protein A (PAPP‐A). The aim of this study was to determine IGFR1 and PAPP‐A expression both in follicles at different stages of development and in cysts, to evaluate the roles in the etiopathogenesis of COD in cattle. The mRNA expression of PAPP‐A was higher in granulosa cells of large tertiary follicles than in cysts, whereas the protein PAPP‐A present in the follicular fluid from these follicles showed no differences. Although no PAPP‐A mRNA expression was detected in smaller tertiary follicles, in their follicular fluid, this protease was detected in lesser concentration than in cysts. The mRNA expression of IGFR1 was lower in granulosa cells from cystic follicles than in those from tertiary ones. However, the protein expression of this receptor presented the highest levels in cystic structures, probably to increase the possibility of IGF response. The data obtained would indicate that animals with COD have an altered regulation of the IGF system in the ovary, which could be involved in the pathogenesis of this disease in cattle. 相似文献
93.
William Kem Ferenc Soti Kristin Wildeboer Susan LeFrancois Kelly MacDougall Dong-Qing Wei Kuo-Chen Chou Hugo R. Arias 《Marine drugs》2006,4(3):255-273
Nemertines are a phylum of carnivorous marine worms that possess a variety of alkaloidal, peptidic or proteinaceous toxins that serve as chemical defenses against potential predators. The hoplonemertines additionally envenomate their prey with a mixture of proboscis alkaloids delivered with the help of a calcareous stylet that punctures the skin of the victim. Anabaseine, the first of these alkaloids to be identified, stimulates a wide variety of animal nicotinic acetylcholine receptors (AChRs), especially the neuromuscular [e.g., α12β1γδ (embryogenic) or α12β1γɛ (adult)] and α7 AChRs that are inhibited by the snake peptide α-bungarotoxin. A synthetic derivative, 3-(2,4-Dimethoxybenzylidene)-Anabaseine (DMXBA; also called GTS-21), improves memory in experimental animals and humans and is currently in clinical trials to determine whether it can ameliorate cognitive problems associated with schizophrenia. Here we summarize present knowledge concerning the chemistry and mechanisms of action of these two substances (anabaseine and DMXBA) on AChRs, especially those found in the mammalian brain. 相似文献
94.
宁南半干旱退化山区抗旱造林技术研究 总被引:3,自引:0,他引:3
通过在年降水量仅为300~500mm地区的抗旱造林中,集成现有的新材料、新方法、新技术,提高造林成活率,为半干旱退化山区人工营造水土保持林、薪炭林、饲料林、用材林、水源涵养林等的植被恢复、改善生态环境、发挥林业可持续发展提供科技支撑。 相似文献
95.
Wei-Ta Fang Bai-You Cheng Shang-Shu Shih Jui-Yu Chou Marinus L. Otte 《Paddy and Water Environment》2016,14(1):185-197
Farm ponds provide a home for birds and numerous species of aquatic animals in Taoyuan, Taiwan. Urbanization and development of infrastructure resulted in the gradual disappearance of these ponds. Currently, only 3800 ponds originally approximately 15.4 % remain, and 84.6 % of the surface area of the ponds has vanished. Aiming to protect avian diversity, this study used logistic regression analysis and the geostatistical approach to analyze the relationship between avian diversity and landscape structure, in an effort to elucidate the spatial driving force of avian diversity. We detected that regression-kriging (RK) was even more accurate than logistic regression (LR). In addition, the value of diversity (H′) measures may decrease instead of increase when evenness (J′) is increased. The results of this study also indicated that an exceedingly strong relationship existed among avian diversity and landscape scale, agricultural landscape indices, and pond landscape indices. The models predict that preservation of large areas of waterscapes and paddy landscapes result in greater diversity of avian species. Spatial estimation of the research area indicated that human activity substantially affected avian ecology, leading to reductions in avian diversity. Thus, the reduction of the area of ecological corridors due to urban development is expected to further reduce avian diversity in the Taoyuan region. Our approach can be used to effectively analyze the correlations between characteristics of ecosystems and the environmental landscape, to ensure that pondscapes can be appropriately maintained and ecological reserves designated to prevent further decline in avian diversity. 相似文献
96.
97.
Lucy Chou Matt J. Griffin Trellor Fraites Cynthia Ware Hugh Ferguson Natalie Keirstead 《Journal of aquatic animal health》2013,25(4):263-271
AbstractStreptococcus iniae, the etiological agent of streptococcosis in fish, is an important pathogen of cultured and wild fish worldwide. During the last decade outbreaks of streptococcosis have occurred in a wide range of cultured and wild fish in the Americas and Caribbean islands. To gain a better understanding of the epizootiology of S. iniae in the western hemisphere, over 30 S. iniae isolates recovered from different fish species and geographic locations were characterized phenotypically and genetically. Species identities were determined biochemically and confirmed by amplification and sequencing of the 16S rRNA gene. Repetitive-element palindromic PCR fingerprinting as well as biochemical and antimicrobial susceptibility profiles suggest that a single strain of S. iniae was responsible for two different disease outbreaks among reef fishes in the Caribbean, one in 1999 and another in 2008. Interestingly, a majority of the isolates recovered from cultured fish in the Americas were genetically distinct from the Caribbean isolates and exhibited a trend toward higher minimal inhibitory concentration with respect to several antibiotics as well as greater genetic variability. The biological significance of this genetic variability is unclear, but it could have implications for future vaccine development and treatment.Received April 20, 2014; accepted July 7, 2014 相似文献
98.
Joshua Chou Jia Hao Shinji Kuroda David Bishop Besim Ben-Nissan Bruce Milthorpe Makoto Otsuka 《Marine drugs》2013,11(12):5148-5158
Foraminifera carbonate exoskeleton was hydrothermally converted to biocompatible and biodegradable zinc-tricalcium phosphate (Zn-TCP) as an alternative biomimetic material for bone fracture repair. Zn-TCP samples implanted in a rat tibial defect model for eight weeks were compared with unfilled defect and beta-tricalcium phosphate showing accelerated bone regeneration compared with the control groups, with statistically significant bone mineral density and bone mineral content growth. CT images of the defect showed restoration of cancellous bone in Zn-TCP and only minimal growth in control group. Histological slices reveal bone in-growth within the pores and porous chamber of the material detailing good bone-material integration with the presence of blood vessels. These results exhibit the future potential of biomimetic Zn-TCP as bone grafts for bone fracture repair. 相似文献
99.
Jui-Hsin Su Yu-Cheng Chen Mohamed El-Shazly Ying-Chi Du Chiang-Wen Su Chia-Wei Tsao Li-Lian Liu Yalan Chou Wen-Been Chang Yin-Di Su Michael Y. Chiang Yao-Tsung Yeh Mei-Chin Lu 《Marine drugs》2013,11(9):3168-3185
A dibromotyrosine derivative, (1′R,5′S,6′S)-2-(3′,5′-dibromo-1′,6′-dihydroxy-4′-oxocyclohex-2′-enyl) acetonitrile (DT), was isolated from the sponge Pseudoceratina sp., and was found to exhibit a significant cytotoxic activity against leukemia K562 cells. Despite the large number of the isolated bromotyrosine derivatives, studies focusing on their biological mechanism of action are scarce. In the current study we designed a set of experiments to reveal the underlying mechanism of DT cytotoxic activity against K562 cells. First, the results of MTT cytotoxic and the annexin V-FITC/PI apoptotic assays, indicated that the DT cytotoxic activity is mediated through induction of apoptosis. This effect was also supported by caspases-3 and -9 activation as well as PARP cleavage. DT induced generation of reactive oxygen species (ROS) and the disruption of mitochondrial membrane potential (MMP) as indicated by flow cytometric assay. The involvement of ROS generation in the apoptotic activity of DT was further corroborated by the pretreatment of K562 cells with N-acetyl-cysteine (NAC), a ROS scavenger, which prevented apoptosis and the disruption of MMP induced by DT. Results of cell-free system assay suggested that DT can act as a topoisomerase II catalytic inhibitor, unlike the clinical anticancer drug, etoposide, which acts as a topoisomerase poison. Additionally, we found that DT treatment can block IKK/NFκB pathway and activate PI3K/Akt pathway. These findings suggest that the cytotoxic effect of DT is associated with mitochondrial dysfunction-dependent apoptosis which is mediated through oxidative stress. Therefore, DT represents an interesting reference point for the development of new cytotoxic agent targeting IKK/NFκB pathway. 相似文献
100.
Teng‐Yu Tsai Shao‐Kuang Chang Po‐Yen Chou Lih‐Seng Yeh 《Veterinary anaesthesia and analgesia》2013,40(6):615-622
ObjectiveTo compare the postoperative analgesic effects of intravenous (IV) lidocaine, meloxicam, and their combination in dogs undergoing ovariohysterectomy.Study designProspective, randomized, double‐blind, controlled clinical trial.AnimalsTwenty‐seven dogs aged (mean ± SD) 16.1 ± 7.5 months and weighing 22.4 ± 17.9 kg scheduled for ovariohysterectomy.MethodsAnaesthesia was induced with propofol and maintained with isoflurane. Dogs (n = 9 in each group) were allocated to receive just prior to and during surgery one of the following regimens: M group, 0.2 mg kg?1 IV meloxicam then a continuous rate infusion (CRI) of lactated Ringer's at 10 mL kg?1 hour?1; L group, a bolus of lidocaine (1 mg kg?1 IV) then a CRI of lidocaine at 0.025 mg kg?1 minute?1; and M + L group, both the above meloxicam and lidocaine treatments. Pain and sedation were scored, and venous samples taken for serum cortisol and glucose measurement before and at intervals for 12 hours after anaesthesia. Pain scores were assessed using a multi‐parameter subjective scoring scale (cumulative scale 0–21) by three observers. The protocol stated that dogs with a total score exceeding 9 or a sub‐score above 3 in any one category would receive rescue analgesia. Sedation was scored on a scale of 0–4.ResultsThere were no significant differences in subjective pain scores, serum cortisol, and glucose concentrations between the three groups. The highest pain score at any time was 5, and no dog required rescue analgesia. None of the three regimens caused any observable side effects during or after anaesthesia. At 1 and 2 hours after extubation dogs in group L were significantly more sedated than in the other two groups.Conclusions and Clinical relevanceThis study suggests that, with the scoring system used, IV lidocaine and meloxicam provide similar and adequate post‐operative analgesia in healthy dogs undergoing ovariohysterectomy. 相似文献