全文获取类型
收费全文 | 2794篇 |
免费 | 176篇 |
专业分类
林业 | 237篇 |
农学 | 117篇 |
基础科学 | 37篇 |
664篇 | |
综合类 | 116篇 |
农作物 | 185篇 |
水产渔业 | 353篇 |
畜牧兽医 | 1010篇 |
园艺 | 61篇 |
植物保护 | 190篇 |
出版年
2024年 | 3篇 |
2023年 | 23篇 |
2022年 | 73篇 |
2021年 | 131篇 |
2020年 | 116篇 |
2019年 | 130篇 |
2018年 | 101篇 |
2017年 | 115篇 |
2016年 | 118篇 |
2015年 | 101篇 |
2014年 | 144篇 |
2013年 | 205篇 |
2012年 | 223篇 |
2011年 | 241篇 |
2010年 | 133篇 |
2009年 | 136篇 |
2008年 | 137篇 |
2007年 | 164篇 |
2006年 | 115篇 |
2005年 | 101篇 |
2004年 | 98篇 |
2003年 | 97篇 |
2002年 | 66篇 |
2001年 | 20篇 |
2000年 | 15篇 |
1999年 | 16篇 |
1998年 | 17篇 |
1997年 | 11篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1966年 | 2篇 |
排序方式: 共有2970条查询结果,搜索用时 12 毫秒
1.
2.
Aguirre E Ayllón T Sainz A Amusategui I Villaescusa A Rodríguez-Franco F Tesouro MA 《Veterinary journal (London, England : 1997)》2009,182(2):301-305
An indirect fluorescent antibody (IFA) test is usually performed to detect antibodies in dogs naturally infected by Ehrlichia canis. In this work, results obtained using three different E. canis strains as antigen (a commercial antigen, the E. canis Oklahoma strain and the E. canis Madrid strain) were compared. One hundred and forty-nine serum samples obtained from dogs living in the centre of Spain were analysed. When qualitative results were evaluated, identical results were detected in 87.2% of samples for the three antigens tested. When comparing antibody titre results, differences between the Madrid strain and the commercial antigen, and between the Madrid and Oklahoma strains were statistically significant (P < 0.0001). No differences were found when comparing the Oklahoma strain with the commercial antigen (P = 0.562). Subtle intra-laboratory variations shown in this study suggest a higher sensitivity of the IFA test when an autochthonous strain is used as antigen. 相似文献
3.
Luis V. García Cristina Ramo Cristina Aponte Adela Moreno María T. Domínguez Lorena Gómez-Aparicio Ramón Redondo Teodoro Marañón 《Biological conservation》2011,(2):764-771
Conservation management conflicts frequently arise when an overpopulation of a protected organism has negative effects on other valuable elements in the same ecosystem. We studied the interactions between a colony of protected tree-nesting wading birds and a remnant population of centenarian cork oaks that was part of the formerly dominant forests in the Doñana Biological Reserve (SW Spain). A significant increase in the tree mortality rates has been recorded in areas that are yearly influenced by the bird colony.We analysed a cohort of surviving trees using a gradient of nesting bird influence. Tree-nesting history, bird isotopic signature (δ15N), tree health-related parameters (defoliation, δ13C and leaf surface coverage by faeces) and several soil variables were evaluated. Bird influence was related to increased soil salinity. This increase correlated to increased water-use efficiency for the leaves and to crown defoliation, suggesting that the heavily occupied trees are under higher stress and in poorer health condition than the unoccupied ones. We tested structural equations models (SEM) that were based on hypothesised bird effects on the health of the trees. Soil-mediated effects of the nesting birds best explained the symptoms of the declining health of the trees, whereas the percent of leaves’ surface that was covered by faeces did not improve the fitted SEM model.For the reserve’s managers, a challenging trade-off exists between preserving the relict trees, which have a high genetic diversity and a key ecological role in these savannah-like ecosystems, and maintaining the current nesting area for these protected, but expanding, wading birds. 相似文献
4.
Alexander Valverde Graham J Crawshaw Nicola Cribb Maria Bellei Giacomo Gianotti Luis Arroyo Judith Koenig Maya Kummrow Maria Carolina Costa 《Veterinary anaesthesia and analgesia》2010,37(3):280-285
ObservationsA 26-year-old male white rhinoceros (Ceratotherium simum), weighing approximately 2000 kg was anesthetized for an exploratory celiotomy. Sedation was achieved with intramuscular butorphanol (0.04 mg kg?1) and detomidine (0.025 mg kg?1) and induction of anesthesia with intravenous glyceryl guaiacolate (50 g) and three intravenous boluses of ketamine (200 mg, each); the trachea was then intubated and anesthesia maintained with isoflurane in oxygen using a circle breathing system. Positioning in dorsal recumbency for the surgery and later in sternal recumbency for the recovery represented challenges that added to the prolonged anesthesia time and surgical approach to partially correct an impaction. The rhinoceros recovered uneventfully after 10.4 hours of recumbency.ConclusionsAnesthetic management for an exploratory celiotomy with a midline approach is possible in rhinoceroses, although planning and extensive staff support is necessary to adequately position the patient. 相似文献
5.
Fernando Díaz Ana Denisse Re Zarina Medina Gerardo Re Gustavo Valdez & Francisco Valenzuela 《Aquaculture Research》2006,37(9):877-884
The thermoregulatory behaviour of green abalone Haliotis fulgens and pink abalone H. corrugata was investigated. Haliotis fulgens juveniles ranging in wet weight from 3.0 to 3.3 g and from 28.7 to 30.5 mm shell length and of H. corrugata 2.0 g and 25.7 mm in shell length were exposed to 19°C for 30 days in a flow‐through water system. Temperature preference was determined in a horizontal thermal gradient and was found to be 25.4°C for green abalone and 25.0°C for pink abalone. Displacement velocity was 4.3 cm h−1 for H. fulgens and 12.8 cm h−1 for H. corrugata. The optimum temperature for growth calculated for both abalone species was 24.6 and 24.5°C respectively. The critical thermal maxima (CTMax) of H. fulgens and H. corrugata were determined as a measure of thermal tolerance. Abalones were subjected to increasing water temperatures at a rate of 1°C on 30 min until they detached from the substrate. The CTMax at 50% were 33.6 and 32.0°C for green and pink abalone respectively. The results are discussed in relation to site selection and commercial rearing. 相似文献
6.
Ramos Silva JC Marvulo MF Dias RA Ferreira F Amaku M Adania CH Ferreira Neto JS 《Preventive veterinary medicine》2007,78(3-4):286-295
From September 1995 to February 2001, blood samples were collected from 865 neotropical felids belonging to 8 different species. These animals were housed in 86 institutions located in 78 cities of 20 Brazilian states. Our goal was to identify the risk factors associated with sero-positivity to Toxoplasma gondii in captive neotropical felids from Brazil. All serum samples were tested by the modified agglutination test (MAT), using formalin-fixed whole tachyzoites and mercaptoethanol. For each animal an individual questionnaire was filled with questions about tattoo number, felid species, age, sex, origin, number of animals in the group, introduction of new animals in the group, time in the institution, eating meat previously frozen for a period <7 days in the last 6 months, eating meat of run-over or euthanized animals in the last 6 months, predation of rodents or birds in the last 6 months and presence of domestic cats near the enclosures in the last 6 months. The total sero-prevalence was 55% (95% CI: 52%, 57%). We estimated a prevalence of 46% (95% CI: 40%, 54%) for jaguarundi (Puma yagouaroundi); 58% (95% CI: 53%, 63%) for ocelot (Leopardus pardalis); 50% (95% CI: 45%, 56%) for oncilla (L. tigrinus); 54% (95% CI: 46%, 62%) for margay (L. wiedii); 12% (95% CI: 4%, 31%) for Pampas-cat (L. colocolo); 83% (95% CI: 65%, 93%) for Geoffroy's-cat (L. geoffroyi); 64% (95% CI: 50%, 68%) for jaguar (Panthera onca) and 48% (95% CI: 42%, 54%) for puma (Puma concolor). Multiple logistic regression was used to evaluate the association between the variables in the questionnaire and sero-positivity to T. gondii. We concluded that the independent risk factors for toxoplasmosis were: age >3 years (OR = 4.75 [2.75; 8.2]), eating meat previously frozen for a period <7 days (OR = 2.23 [1.24; 4.01]), and consumption of animals that were run-over or euthanized (OR = 1.64; [1.14; 2.37]). 相似文献
7.
Aguiar DM Cavalcante GT Rodrigues AA Labruna MB Camargo LM Camargo EP Gennari SM 《Veterinary parasitology》2006,142(1-2):71-77
For evaluation of the prevalence of anti-Neospora caninum antibodies and its associated risk factors, serum samples from 2109 cattle (11 beef, 50 dairy and 25 mixed farms) and 174 dogs were examined in the State of Rond?nia, Western Amazon, Brazil. An inquiry was applied in each farm. Sera were examined by the Indirect Fluorescence Antibody Test (IFAT) using cut off dilution of 1:25 for cattle and 1:50 for dogs. Statistical association between the serologic status and several variables were analyzed by linear and logistic regression. The overall herd prevalence of anti-N. caninum antibodies for 86 farms was 72% (61.3-81.2%). Prevalence values were 100, 70 and 64% in beef, dairy and mixed herds, respectively. Herd prevalence in beef herds was significantly different (P<0.05) from dairy and mixed herds. The overall animal prevalence of N. caninum in cattle was 8.8%. Prevalence values by animal were similar in different production types (P>0.05), with values of 9.5, 11.2 and 9.7% for beef, dairy or mixed cattle, respectively. Antibodies were found in 12.6% of the 174 examined dogs. Sixteen (22.8%) out of 70 farms with dogs had at least one dog with anti-N. caninum antibodies. The occurrence of antibodies in cattle was statistically associated with farms having more than 25 cows (OR 9.7, 95% IC 2.9-32.2; P=0.0002). There was no significant association between the presence of the dogs, jungle contact or reproductive variables with the occurrence of antibodies in cattle. 相似文献
8.
Christiane von der Ohe Victoria Gauthier Lily Tamburic-Ilincic Anita Brule-Babel W. G. Dilantha Fernando Randy Clear Todd J. Ward Thomas Miedaner 《European journal of plant pathology / European Foundation for Plant Pathology》2010,127(3):407-417
Twenty four isolates of Fusarium graminearum, half of which were 3-acetyldeoxynivalenol (3-ADON) and half 15-acetyldeoxynivalenol (15-ADON) chemotypes, were tested for
their ability to produce deoxynivalenol and to cause Fusarium head blight (FHB) in spring wheat cultivars. The objectives
of this study were to determine (1) whether 3-ADON isolates differ in aggressiveness, as measured by the FHB index, and DON
production from 15-ADON isolates under field conditions, and (2) whether the performance of resistant host cultivars was stable
across isolates. Field tests of all isolates were conducted with three replicates at each of two locations in Canada and Germany
in 2008 with three host genotypes differing in FHB resistance level. The resistant host genotype showed resistance regardless
of the chemotype or location. The differences between mean FHB indices of 3-ADON and 15-ADON isolates were not significant
for any wheat genotype. In contrast, average DON production by the 3-ADON isolates (10.44 mg kg−1) was significantly (P < 0.05) higher than for the 15-ADON isolates (6.95 mg kg−1) at three of the four locations where moderately resistant lines were tested, and at both locations where susceptible lines
were evaluated. These results indicate that 3-ADON isolates could pose a greater risk to food safety. However, as the mean
aggressiveness and DON production of 3-ADON and 15-ADON chemotypes was similar on highly resistant lines, breeding and use
of highly resistant lines is still the most effective measure of reducing the risks associated with DON in wheat. 相似文献
9.
Evaluating the role of ecosystem services in participatory land use planning: proposing a balanced score card 总被引:1,自引:0,他引:1
The application of the ecosystem services (ES) concept in land use planning has great potential to enhance the awareness of planning actors on their interactions. At the same time it can contribute to improve the linkage between the role of land use patterns and the understanding of land system functioning and its contribution to human well-being. The concept should be developed in a way that can be applicable in socio-ecological systems where nature and society are capable of enhancing their roles mutually. The objective of this paper is to suggest a standardized scheme and generalizable criteria to assess how successful the application of the ES concept contributed to facilitate participatory planning. We consider three potential advantages and three critical aspects for how to improve the applicability and relevance of the ES concept in planning. Hereon based, we present a balanced score card tool for which we broke down to advantages and risks into concrete questions. We illustrate the application of this approach with two case studies, representatives of two major governance schemes in relation to land use planning. We demonstrate that the balanced score card approach helps to reveal potential imbalances regarding the consideration of different ES groups. It supports testing the potential of the ES concept to enhance or not interactions of local and regional actors. We conclude that the framework should be reconsidered after a set of case studies to be developed into a monitoring tool for supporting planning practices. 相似文献
10.
- Marine aquaculture, and its fast-growing development, has the potential for wider environmental, ecosystem, and biodiversity impacts. This study assesses the impact of fish farming on a bottlenose dolphin (Tursiops truncatus) population within the Gulf of Ambracia (western Greece) between 2007 and 2018. Two different study areas were defined in order to investigate differences on occurrence, abundance, behaviour, and seasonal fluctuations between them: a ‘control area’, in the north-western side of the Gulf; and a ‘fish farm area’, in the south west, where the highest density of fish farm cages is found.
- A total of 169 daily surveys were dedicated to the control area and 74 days were dedicated to the fish farm area, yielding 104 and 37 sightings, respectively. Both the probability of detecting dolphins (U = 6,763.000, P = 0.002) and the group sizes (U = 578.000, P < 0.001) were smaller around fish farms.
- Seasonality analyses were restricted to 2007–2008, as this was the period with year-round effort. Results revealed that dolphins were more frequently seen around fish farms in the winter (Kruskal–Wallis test, P = 0.036).
- From the 40 identified individuals that were re-sighted at least 10 times during the study period, 21 used the fish farm area less than expected according to sampling effort, and 10 of them were never observed in that area (binomial test, P < 0.05).
- The results revealed an impact of fish farms on the distribution of bottlenose dolphins in the Gulf of Ambracia. This information should be taken into consideration when defining ecosystem-based management measures within the management plan, which is currently in preparation for this Natura 2000 site.