全文获取类型
收费全文 | 669篇 |
免费 | 24篇 |
国内免费 | 3篇 |
专业分类
林业 | 76篇 |
农学 | 11篇 |
基础科学 | 2篇 |
209篇 | |
综合类 | 85篇 |
农作物 | 29篇 |
水产渔业 | 12篇 |
畜牧兽医 | 179篇 |
园艺 | 16篇 |
植物保护 | 77篇 |
出版年
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 13篇 |
2018年 | 12篇 |
2017年 | 10篇 |
2016年 | 20篇 |
2015年 | 15篇 |
2014年 | 20篇 |
2013年 | 33篇 |
2012年 | 27篇 |
2011年 | 43篇 |
2010年 | 25篇 |
2009年 | 12篇 |
2008年 | 28篇 |
2007年 | 40篇 |
2006年 | 43篇 |
2005年 | 23篇 |
2004年 | 22篇 |
2003年 | 30篇 |
2002年 | 28篇 |
2001年 | 20篇 |
2000年 | 11篇 |
1999年 | 16篇 |
1998年 | 8篇 |
1997年 | 11篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1970年 | 5篇 |
1969年 | 3篇 |
1967年 | 3篇 |
1966年 | 7篇 |
1965年 | 3篇 |
排序方式: 共有696条查询结果,搜索用时 15 毫秒
1.
2.
3.
Tracy Van Holt H. Russell Bernard Susan Weller Wendy Townsend Peter Cronkleton 《Human Dimensions of Wildlife》2016,21(2):169-179
We examined hunters’ perceptions of fauna to see if expert hunters and other hunters perceive wildlife abundance similarly. We used cultural consensus analysis (CCA) to assess the knowledge of 25 hunters in the Bolivian Amazon about the abundance of 38 animals. CCA indicated highly shared beliefs among hunters concerning wildlife abundance (average agreement = .62). However, expert hunters (as judged by their reported successful hunts of rare species, having hunted recently, and consuming more game in their diet) perceived more animals as abundant than did non-experts, although they all shared the same model. Since the expert hunters did not always agree on which species was more abundant, they had low cultural knowledge scores in CCA results. These experts may be unwilling to curtail hunting efforts on key species that they perceive to be abundant. 相似文献
4.
5.
Ohlschläger S Spolders M Meyer U Flachowsky G 《Berliner und Münchener tier?rztliche Wochenschrift》2007,120(5-6):226-231
At the Institute of Animal Nutrition of the Federal Agricultural Research Centre (FAL) in Braunschweig a feeding trial with 30 first lactating cows (German Holstein) was realised in 2004 for a complete lactation. All animals received a diet based on maize- and grass-silage ad libitum at the rate of 60:40 (DM-base) and concentrate depending on their milk yield.The animals were fed with energy and protein as recommended (GfE 2001) and were kept in loose housing. After calving they were split randomly into two feeding groups with 15 animals each. Group 1 was fed a concentrate according to the recommendations of the GfE (2001), whereas group 2 was offered the same concentrate with roughly the double amount of calcium, magnesium, phosphorus, copper, zinc, beta-carotene and vitamins A and E. To study the influence of the different concentrates on the serum concentrations of minerals and vitamins, blood, feed and milk samples were regularly taken and analysed in the course of lactation. Significantly higher blood concentrations were detected for phosphorus, zinc and vitamin E in group 2, but therefore a direct influence of the feeding on the blood concentrations was detected only for zinc and vitamin E. Over the whole lactation the average milk yield of group 1 was 2.6 kg/day higher and the average milk fat content was reduced about 0.6 percent points compared to group 2. 相似文献
6.
Pfau T Robilliard JJ Weller R Jespers K Eliashar E Wilson AM 《Equine veterinary journal》2007,39(5):407-413
REASONS FOR PERFORMING STUDY: Hindlimb lameness is common and can be difficult to diagnose or quantify in evaluating response to nerve blocks. An objective measure of lameness can also be used to evaluate the effectiveness of the treatment's contribution to evidence-based medicine. The inertial sensor system can be used to capture 6 degree of freedom movement during over ground locomotion and here was used to quantify tuber coxae movement in nonlame and lame horses. HYPOTHESIS: Tuber coxae movement is useful for discriminating between nonlame and lame horses. OBJECTIVES: To measure left and right tuber coxae movement in lame and nonlame horses during over ground locomotion and to implement a linear discriminant analysis to discriminate between lame and nonlame horses. METHODS: Two inertial sensors were attached to the skin over left and right tuber coxae of 21 horses (9 mildly and 12 not lame). Horses were trotted on a hard surface. A total of 1021 strides were collected. For each stride 34 features were extracted from the dorsoventral and craniocaudal movement and used in 2 different classification scenarios (lame vs. nonlame or left lame, right lame and nonlame) using linear discriminant analysis. RESULTS: Six degree of freedom inertial sensors were successfully used to collect kinematic data continuously from left and right tuber coxae in horses during over ground locomotion. These data were used for an automated classification of lameness. In the first scenario, a sensitivity of 89% was achieved with a specificity of 75%. In the second scenario, all horses could be correctly assigned to the correct class in a simple 3 class reclassification test. POTENTIAL RELEVANCE: A mobile system that reliably detects and quantifies hindlimb lameness in horses during unconstrained locomotion could be a valuable tool to perform an evidence-based assessment of lameness in horses in a clinical setting, e.g. before and after nerve blocks or before and after surgery. 相似文献
7.
James A. Weller 《Irrigation and Drainage Systems》1991,5(1):1-17
An irrigation water management research programme was implemented by Hydraulics Research in collaboration with the National Irrigation Administration of the Philippines on the Porac Area of Porac Gumain Rivers Irrigation System. The objectives of the study are to monitor the response of the main canal network to changes in water availability and assess its capability to deliver crop water requirements to sub-areas jointly managed by National Irrigation Administration staff and existing Irrigator Associations. This paper presents an analysis of the response of the main system to the varying irrigation demands, and assesses the conjunctive use of groundwater with surface water and the potential of computer models to assist management with the preparation of the annual irrigation schedules. 相似文献
8.
过去人们常认为,由于刚出壳雏鸡的免疫系统尚未发育成熟,同时肠道内缺乏有益的微生物,因而处于高度的敏感期,此时接种沙门氏菌苗产生的保护作用很有限。然而,最新的研究表明,在这些敏感期接种疫苗,可诱发产生保护作用。 相似文献
9.
10.
Since the discovery of penicillin in 1928 and throughout the ‘age of antibiotics’ from the 1940s until the 1980s, the detection of novel antibiotics was restricted by lack of knowledge about the distribution and ecology of antibiotic producers in nature. The discovery that a phenazine compound produced by Pseudomonas bacteria could suppress soilborne plant pathogens, and its recovery from rhizosphere soil in 1990, provided the first incontrovertible evidence that natural metabolites could control plant pathogens in the environment and opened a new era in biological control by root‐associated rhizobacteria. More recently, the advent of genomics, the availability of highly sensitive bioanalytical instrumentation, and the discovery of protective endophytes have accelerated progress toward overcoming many of the impediments that until now have limited the exploitation of beneficial plant‐associated microbes to enhance agricultural sustainability. Here, we present key developments that have established the importance of these microbes in the control of pathogens, discuss concepts resulting from the exploration of classical model systems, and highlight advances emerging from ongoing investigations. © 2019 Society of Chemical Industry 相似文献