全文获取类型
收费全文 | 572篇 |
免费 | 43篇 |
专业分类
林业 | 10篇 |
农学 | 10篇 |
基础科学 | 3篇 |
35篇 | |
综合类 | 154篇 |
农作物 | 26篇 |
水产渔业 | 28篇 |
畜牧兽医 | 293篇 |
园艺 | 6篇 |
植物保护 | 50篇 |
出版年
2023年 | 4篇 |
2021年 | 11篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 15篇 |
2017年 | 12篇 |
2016年 | 15篇 |
2015年 | 9篇 |
2014年 | 7篇 |
2013年 | 44篇 |
2012年 | 10篇 |
2011年 | 19篇 |
2010年 | 16篇 |
2009年 | 10篇 |
2008年 | 22篇 |
2007年 | 23篇 |
2006年 | 12篇 |
2005年 | 14篇 |
2004年 | 18篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 8篇 |
2000年 | 13篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1995年 | 4篇 |
1992年 | 10篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 18篇 |
1988年 | 26篇 |
1987年 | 27篇 |
1986年 | 24篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1979年 | 4篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1973年 | 4篇 |
1972年 | 6篇 |
1971年 | 5篇 |
1970年 | 4篇 |
1968年 | 4篇 |
1967年 | 5篇 |
1959年 | 5篇 |
1949年 | 5篇 |
1948年 | 6篇 |
1946年 | 5篇 |
1896年 | 3篇 |
排序方式: 共有615条查询结果,搜索用时 15 毫秒
101.
Barnes PJ 《Science (New York, N.Y.)》2010,330(6000):40-41
102.
SL Walker RF Smith DN Jones JE Routly MJ Morris H Dobson 《Reproduction in domestic animals》2010,45(1):109-117
The objectives of the present study were to quantify the effects of a biological chronic stressor (lameness) on the duration and frequency of different oestrous behaviours in parallel with milk hormone profiles. Dairy cows 51.8 ± 1.4 days postpartum (n = 59), including 18 non‐lame control cows, were scored for lameness and closely observed for signs of oestrus having had their follicular phases synchronized by administration of gonadotrophin‐releasing‐hormone (GnRH) followed by prostaglandin F2α (PG) 7 days later. Lameness shortened the period when herd‐mates attempted to mount the lame cows (1.83 ± 0.69 h vs 5.20 ± 1.53 h; p = 0.042) but did not affect the overall duration of total behaviours (lame 12.3 ± 1.3 h vs non‐lame 15.2 ± 1.3 h). Lameness also lowered the intensity of oestrus [1417 ± 206 points (n = 18) vs 2260 ± 307 points (n = 15); p = 0.029]. Throughout the synchronized oestrous period, lame cows mounted the rear of herd‐mates less frequently (p = 0.020) and tended to chin rest less (p = 0.075). Around the period of maximum oestrous intensity, lameness also diminished the proportion of cows mounting the rear of another cow and chin resting (p = 0.048, p = 0.037, respectively). Furthermore, lame cows had lower progesterone values during the 6 days before oestrous (p ≤ 0.05). Fewer lame cows were observed in oestrus following PG (non‐lame 83%, lame 53%; p = 0.030); however, if prior progesterone concentrations were elevated, lame cows were just as likely to be observed in oestrus. In conclusion, following endogenous progesterone exposure, lameness shortens the period when herd‐mates attempt to mount lame cows but does not affect the incidence of oestrous. However, lame cows are mounted less frequently and express oestrus of lower intensity. This is associated with lower progesterone prior to oestrus but not with abnormal oestradiol or cortisol profiles in daily milk samples. 相似文献
103.
Objective To evaluate the effects of time on cellular localization of Visudyne® after local injection. Animals Twenty athymic nude mice. Procedures A squamous cell carcinoma (SCC) cell line (A‐431) was injected into right and left dorsolumbar subcutaneous tissue of each mouse, representing treatment (T) and control (C) tumors. In experiment 1 (Exp 1; n = 10) and 2 (Exp 2; n = 10), the T tumors received a local injection of Visudyne® (0.1 mg/cm3), and C tumors received an equal dose of 5% dextrose in water (D5W). Mice were randomly subdivided into two groups (A and B; n = 5 per group). Mice in Exp 1A and B were sacrificed 1 and 30 min after local injection, respectively. Experiment 1A and B tumors were evaluated by fluorescence microscopy to determine drug localization. Experiment 2A and B tumors were exposed to LED illumination 1 and 30 min after injection, respectively, and evaluated by transmission electron microscopy (TEM) to determine ultrastructural tumor cell damage. Results Fluorescence was detected within the cytoplasm of T tumors in both Exp 1A and B. Significance was detected in fluorescence intensity between T1 min vs. T30 min (P = 0.03) and between T1 min and C1 min tumors (P = 0.01), respectively. Tumors in Exp 2A and B demonstrated evidence of apoptotic cell death. Conclusions Fluorescence microscopy demonstrated higher Visudyne® concentration within SCC cytoplasm of 1 min compared with 30‐min tumors. Transmission electron microscopy results revealed that tumors treated by photodynamic therapy (PDT) within 30 min of local injection undergo cellular apoptosis. 相似文献
104.
Dothistroma needle blight: an emerging epidemic caused by Dothistroma septosporum in Colombia
下载免费PDF全文
![点击此处可从《Plant pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Plantation forestry in Colombia is based mainly on non‐native species of Pinus and Eucalyptus. Since 2008, a disease with symptoms similar to those of dothistroma needle blight (DNB) has been found affecting large areas planted to Pinus spp. The aim of this study was to identify the causal pathogen as well as to document the levels of disease incidence and severity. Isolates from each of three forestry zones, collected from different host species, were compared based on rDNA sequence of the ITS regions. These were conclusively identified as Dothistroma septosporum, one of two Dothistroma spp. known to cause DNB. Susceptibility was greatest on low elevation Pinus tecunumanii followed by Pinus kesiya and Pinus oocarpa. Pinus maximinoi and high elevation P. tecunumanii showed tolerance to D. septosporum. The disease incidence in the different zones varied significantly with the North zone being the most severely affected. This constitutes the first report of disease distribution and susceptibility of hosts, as well as the first consideration of the relative importance of D. septosporum in Colombia. 相似文献
105.
106.
107.
Precision Agriculture - Soil acidification is a growing problem in semi-arid agroecosystems. In the state of Montana, USA, soil pH levels below 5.5 have been documented in nearly half of the... 相似文献
108.
Brock J. Bergseth Adrian Arias Michele L. Barnes Iain Caldwell Amber Datta Stefan Gelcich Sam H. Ham Jacqueline D. Lau Cristina Ruano-Chamorro Patrick Smallhorn-West Damian Weekers Jessica Zamborain-Mason Joshua E. Cinner 《Fish and Fisheries》2023,24(4):695-704
Advocates, practitioners and policy-makers continue to use and advocate for marine protected areas (MPAs) to meet global ocean protection targets. Yet many of the worlds MPAs, and especially no-take MPAs, are plagued by poaching and ineffective governance. Using a global dataset on coral reefs as an example, we quantify the potential ecological gains of governing MPAs to increase compliance, which we call the ‘compliance gap’. Using ecological simulations based on model posteriors of joint Bayesian hierarchical models, we demonstrate how increased compliance in no-take MPAs could nearly double target fish biomass (91% increases in median fish biomass), and result in a 292% higher likelihood of encountering top predators. Achieving these gains and closing the compliance gap necessitates a substantial shift in approach and practice to go beyond optimizing enforcement, and towards governing for compliance. This will require engaging and integrating a broad suite of actors, principles, and practices across three key domains: (i)) harnessing social influence, (ii) integrating equity principles, and (iii) aligning incentives through market-based instruments. Empowering and shaping communication between actor groups (e.g., between fishers, practitioners, and policy-makers) using theoretically underpinned approaches from the behavioural sciences is one of the most essential, but often underserved aspects of governing MPAs. We therefore close by highlighting how this cross-cutting tool could be further integrated in governance to bolster high levels of compliance in MPAs. 相似文献
109.
110.