全文获取类型
收费全文 | 373篇 |
免费 | 28篇 |
专业分类
林业 | 31篇 |
基础科学 | 3篇 |
33篇 | |
综合类 | 77篇 |
农作物 | 14篇 |
水产渔业 | 58篇 |
畜牧兽医 | 132篇 |
园艺 | 25篇 |
植物保护 | 28篇 |
出版年
2024年 | 3篇 |
2023年 | 4篇 |
2022年 | 5篇 |
2021年 | 13篇 |
2020年 | 18篇 |
2019年 | 24篇 |
2018年 | 13篇 |
2017年 | 12篇 |
2016年 | 8篇 |
2015年 | 16篇 |
2014年 | 14篇 |
2013年 | 12篇 |
2012年 | 26篇 |
2011年 | 34篇 |
2010年 | 14篇 |
2009年 | 8篇 |
2008年 | 24篇 |
2007年 | 27篇 |
2006年 | 21篇 |
2005年 | 19篇 |
2004年 | 20篇 |
2003年 | 15篇 |
2002年 | 18篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1966年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有401条查询结果,搜索用时 15 毫秒
1.
The effects of azadirachtin (AZA) and nucleopolyhedrovirus (NPV) on midgut enzyme activity in Spodoptera litura Fabricius (Lepidoptera: Noctuidae) (Tobacco cutworm) were evaluated. Gut enzyme activities were decreased by AZA and NPV individually and in combination. When S. litura larvae were fed a diet of castor leaves treated with AZA and NPV in bioassays, gut enzyme—acid phosphatases, alkaline phosphatases, adenosine triphosphatases, and lactate dehydrogenase—activities were decreased. There were statistically significant differences (P ? 0.05) in enzyme activities between combined and individual treatment. A synergistic effect of botanical insecticides and virus was found when combined in low doses. These effects are most pronounced in early instars. Maximum weight loss (59-72%) occurred, when AZA and NPV were combined. 相似文献
2.
Hamish M Aiken Nathan J Bott Ivona Mladineo Francisco E Montero Barbara F Nowak & Craig J Hayward 《Fish and Fisheries》2007,8(3):167-180
Global distribution of platyhelminth parasites and their host specificities are not well known. Our hypothesis was that platyhelminth parasites of large pelagic fishes are common around the world. We analysed molecular variation in three different taxa of platyhelminth parasites infecting four species of tunas: yellowfin tuna (Thunnus albacares, Scombridae) from Western Australia, southern bluefin tuna (Thunnus maccoyii, Scombridae) from South Australia, Pacific bluefin tuna (Thunnus orientalis, Scombridae) from Pacific Mexico and northern bluefin tuna (T. thynnus, Scombridae) from two localities in the Mediterranean (Spain and Croatia). Comparisons of ITS2 and partial 28S rDNA demonstrated two congeneric species of blood flukes (Digenea: Sanguinicolidae) from multiple hosts and localities: Cardicola forsteri from southern bluefin and northern bluefin tunas, and Cardicola sp. from Pacific bluefin and northern bluefin tunas; and a gill fluke, Hexostoma thynni (Polyopisthocotylea: Hexostomatidae), from yellowfin, southern bluefin and northern bluefin tunas. Partial 28S rDNA indicates that a second type of fluke on the gills, Capsala sp. (Monopisthocotylea: Capsalidae), occurs on both southern bluefin and Pacific bluefin tunas. This appears to be the first report of conspecific platyhelminth parasites of teleosts with a wide‐ranging geographical distribution that has been confirmed through molecular approaches. Given the brevity of the free‐living larval stage of both taxa of flukes on the gills (H. thynni and Capsala sp.), we conclude that the only feasible hypothesis for the cosmopolitan distribution of these flatworms is migrations of host tunas. Host migration also seems likely to be responsible for the widespread occurrence of the two species of blood flukes (Cardicola spp.), although it is also possible that these were translocated recently by the spread of infected intermediate hosts. 相似文献
3.
Nathan L. Cherzan Boel A. Fransson 《The Canadian veterinary journal. La revue veterinaire canadienne》2021,62(6):577
A 2-year-old intact female Alaskan husky sled dog was presented with a history of chronic exercise-induced regurgitation refractory to medical management. Previous diagnostics were unremarkable except for an endoscopic examination and histopathologic evaluation of the upper gastrointestinal tract that revealed the presence of Helicobacter spp. and mild non-specific inflammation of the proximal duodenum. A laparoscopic hiatal herniorrhaphy, esophagopexy, fundopexy, and ovariectomy were performed without complications in anesthesia or surgery and clinical improvement was observed with continued follow-up for 8 months after surgery.Key clinical message:Surgical treatment for hiatal hernia may be considered in racing Alaskan sled dogs with regurgitation refractory to gastric protectant therapy. 相似文献
4.
Swadling Daniel S. Knott Nathan A. Rees Matthew J. Davis Andrew R. 《Landscape Ecology》2019,34(10):2337-2352
Landscape Ecology - Whilst the composition and arrangement of habitats within landscape mosaics are known to be important determinants of biodiversity patterns, the influence of seascape patterning... 相似文献
5.
Snyder Marcía N. Schumaker Nathan H. Ebersole Joseph L. Dunham Jason B. Comeleo Randy L. Keefer Matthew L. Leinenbach Peter Brookes Allen Cope Ben Wu Jennifer Palmer John Keenan Druscilla 《Landscape Ecology》2019,34(5):1197-1197
Landscape Ecology - In the original publication of the article, the third author name has been misspelt. The correct name is given in this Correction. The original version of this article was revised. 相似文献
6.
Context
Species distributions are driven by a wide variety of abiotic and biotic factors, including nest placement for breeding individuals. As such, the spatial distribution of nests within a landscape can reflect environmental heterogeneity, habitat preferences, or even interactions with predators and other species.Objectives
We determined the extent to which environmental heterogeneity and predation risk accounted for the observed spatial distribution of nests.Methods
We assessed the spatial distribution of 112 nests of a migratory shorebird, the Hudsonian Godwit (Limosa haemastica), at Beluga River, Alaska, from 2009 to 2012, and explicitly tested for the relative influence of habitat characteristics and predation risk on nest locations. We also evaluated the effect of nest location, distance to conspecific nests, and proximity to roads on nest fate using 64 nests that were monitored through completion.Results
Hudsonian Godwit nests were clustered across the landscape despite a lack of significant spatial autocorrelation (i.e., patchiness) in vegetation characteristics at either the micro- or landscape scale. Nest fate also was not predicted by either the distance to the nearest conspecific neighbor or proximity to roads. Thus, neither habitat characteristics nor predation risk explained the clustering of godwit nests.Conclusions
These results suggest that godwits may select nest locations based more on social cues than underlying heterogeneity in vegetation or predation risk. As such, intra- and inter-specific interactions should be considered when developing management plans for species of conservation concern.7.
Ricardo F Rosenbusch Joann M Kinyon Michael Apley Nathan D Funk Sean Smith Lorraine J Hoffman 《Journal of veterinary diagnostic investigation》2005,17(5):436-441
Antimicrobial therapy continues to be important in reducing losses due to pneumonic forms of Mycoplasma bovis disease in beef and dairy calves. Although M. bovis diseases have been documented as frequent and economically important in the United States, there are no published reports on the antimicrobial activity of approved compounds against US strains. In this study, the authors report on the activity of 9 different antimicrobials against 223 recently recovered isolates of M. bovis. These isolates represent accessions from 5 geographic regions of the United States and were grouped by 4 tissues of origin (milk, respiratory, joint, or ear and eye). A broth microdilution test was used to determine minimum inhibitory concentration (MIC) values by reading redox changes detected in broth with alamarBlue (resazurin) indicator. For each antimicrobial, the median, MIC50, MIC90, mode, and range were calculated, and the values used for comparisons. In the absence of accepted breakpoint values, published MIC cutoff values for animal mycoplasmas as well as Clinical Laboratory Standards Institute interpretive criteria were used as a reference to define in vitro activity. The MIC values from active antimicrobials were found to distribute independently of region of origin of the isolates or of tissue of origin. Enrofloxacin, florfenicol, and spectinomycin were found to be active compounds in vitro. Oxytetracycline and chlortetracycline were active against more than half of the isolates. Very few isolates were inhibited by tilmicosin and none by erythromycin, ampicillin, or ceftiofur. The antimicrobial profiles determined for these US strains were remarkably similar to those reported for European isolates. However, unlike in Europe, there appears to be no diversity of profiles when US isolates are grouped by region or tissue of origin. 相似文献
8.
Todhunter RJ Bertram JE Smith S Farese JP Williams AJ Manocchia A Erb HN Dykes NL Burton-Wurster NI Lust G 《Veterinary surgery : VS》2003,32(3):196-205
OBJECTIVE: To determine whether dorsal loading of the pelvis and type of chemical restraint affected the dorsolateral subluxation (DLS) score of dog hips. STYDY DESIGN: In vivo testing of diagnostic method. ANIMALS: Labrador retrievers, Greyhounds, and crosses between both breeds (n = 119 dogs). METHODS: Dorsal load was applied to the hips through a strap that was placed over the hips, and the peak vertical and steady-state vertical, ground-reaction forces exerted on the stifles were measured in the DLS position. The DLS score was measured with their hips under dorsal load and compared with the DLS score without load. For 24 dogs, the DLS score was measured both under chemical restraint (medetomidine) and under general anesthesia. Wilcoxon-signed rank test and paired t test was used to compare effects of dorsal load and restraint method on the left and right DLS hip score, and P <.05 was considered significant. RESULTS: Both stifles together accepted median 15% body weight in the vertical plane in the unloaded steady state. Loading the hips increased the steady-state, vertical ground-reaction force to 34% body weight. At 8 months of age, loading significantly decreased the DLS score from 65% +/- 11% (mean +/- SD) to 60% +/- 12% for left hips and 66% +/- 11% to 63% +/- 13% for right hips. The left hip DLS score was affected by load more consistently than the right hip. In general, loading the hips decreased the DLS score in all breeds by 4% to 6% except for the greyhounds, in which the DLS score was unchanged by dorsal loading. When grouped by their DLS scores, load significantly decreased DLS scores in dogs with unloaded scores greater than 55% (nondysplastic), whereas DLS scores of dogs with unloaded scores between 55% and 45% (dysplastic) and less than 45% did not change significantly with load. Unloaded scores did not change significantly when compared under sedation versus general anesthesia. However, load significantly decreased the DLS score under general anesthesia for the left hip but not for the right hip. CONCLUSIONS: Less than half of the vertical ground-reaction force normally exerted by the hindlegs of a standing dog was sufficient to induce hip subluxation in the DLS position. Although dorsal loading approximately doubled the steady-state, vertical ground-reaction force, the decrease in the DLS score under load was never greater than 6%. Furthermore, the DLS scores of dogs most likely to be dysplastic (based on DLS scores <45%) were not affected by load, whereas load slightly decreased DLS cores of dogs with DLS scores greater than 55%. CLINICAL RELEVANCE: External influences can change the DLS score significantly, but the magnitude of change is unlikely to be of clinical importance, making the method useful as a field screening test for both dysplastic and nondysplastic hips in young dogs. 相似文献
9.
Hayley Weston Murphy Michele Miller Jan Ramer Dominic Travis Robyn Barbiers Nathan D Wolfe William M Switzer 《Journal of zoo and wildlife medicine》2006,37(3):219-233
Nonhuman primates can be naturally infected with a plethora of viruses with zoonotic potential, including retroviruses. These simian viruses present risks to both captive nonhuman primate populations and persons exposed to nonhuman primates. Simian retroviruses, including simian immunodeficiency virus, simian type D retrovirus, simian T-lymphotropic virus, and gibbon ape leukemia virus, have been shown to cause clinical disease in nonhuman primates. In contrast, simian foamy virus, a retrovirus that is highly prevalent in most nonhuman primates, has not been associated with clinical disease in naturally infected primates. Although it has been shown that human retrovirus infections with human T-lymphotropic virus and human immunodeficiency virus originated through multiple independent introductions of simian retroviruses into human populations that then spread globally, little is known about the frequency of such zoonotic events. In this article, exogenous simian retroviruses are reviewed as a concern for zoo and wildlife veterinarians, primate handlers, other persons in direct contact with nonhuman primates, and other nonhuman primates in a collection. The health implications for individual animals as well as managed populations in zoos and research institutions are discussed, the cross-species transmission and zoonotic disease potential of simian retroviruses are described, and suggestions for working safely with nonhuman primates are provided. 相似文献
10.
A Syndrome Resembling Idiopathic Noncirrhotic Portal Hypertension in 4 Young Doberman Pinschers 总被引:1,自引:0,他引:1
JoAnn DeMarco Sharon A. Center Nathan Dykes Amy E. Yeager Bruce Kornreich Ed Gschrey Kelly A. Credille Magali Guffroy Fabio del Piero Beth A. Valentine 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1998,12(3):147-156
We describe 4 young male Doberman Pinschers (3 littermates and 1 unrelated dog) with a syndrome resembling idiopathic or noncirrhotic portal hypertension of humans. Each dog was evaluated for a hepatopathy resulting in portal hypertension, development of portosystemic collateral vessels, and hepatic encephalopathy. These dogs differ from previous reports of young dogs with hepatic insufficiency associated with portal hypertension and acquired portal systemic shunting by their lack of intrahepatic arteriovenous fistulae, portal vein atresia, or intrahepatic fibrosis. Clinicopathologic features included erythrocyte microcytosis, normal to mildly increased liver enzyme activities, increased concentrations of serum bile acids, reduced plasma indocyanine green clearance, and normal total bilirubin concentration. Abdominal ultrasonography disclosed a small liver and portosystemic collateral vessels. Radiographic imaging studies confirmed hepatofugal portal circulation and discounted hepatic arteriovenous fistulae. Histopathologic features in liver tissue from each dog were similar and consistent in all sections examined. Common findings included increased cross-sectional views of hepatic arterioles; hepatic lobular atrophy; scanty increase in connective tissue around some large portal triads; and absence of inflammation, disturbed lobular architecture, bile duct proliferation, or intrahepatic cholestasis. 相似文献