全文获取类型
收费全文 | 19194篇 |
免费 | 184篇 |
国内免费 | 4篇 |
专业分类
林业 | 3794篇 |
农学 | 1359篇 |
基础科学 | 157篇 |
3195篇 | |
综合类 | 1400篇 |
农作物 | 2150篇 |
水产渔业 | 2013篇 |
畜牧兽医 | 2070篇 |
园艺 | 1173篇 |
植物保护 | 2071篇 |
出版年
2024年 | 8篇 |
2023年 | 20篇 |
2022年 | 30篇 |
2021年 | 71篇 |
2020年 | 77篇 |
2019年 | 91篇 |
2018年 | 2800篇 |
2017年 | 2759篇 |
2016年 | 1255篇 |
2015年 | 132篇 |
2014年 | 93篇 |
2013年 | 113篇 |
2012年 | 971篇 |
2011年 | 2337篇 |
2010年 | 2230篇 |
2009年 | 1342篇 |
2008年 | 1525篇 |
2007年 | 1784篇 |
2006年 | 225篇 |
2005年 | 286篇 |
2004年 | 294篇 |
2003年 | 333篇 |
2002年 | 235篇 |
2001年 | 36篇 |
2000年 | 63篇 |
1999年 | 28篇 |
1998年 | 16篇 |
1997年 | 7篇 |
1996年 | 18篇 |
1995年 | 15篇 |
1994年 | 12篇 |
1993年 | 21篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 15篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1974年 | 8篇 |
1973年 | 3篇 |
1968年 | 5篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Andrew J Brown Cynthia M Otto 《Veterinary Clinics of North America: Small Animal Practice》2008,38(3):653-75, xiii
Fluid therapy in the patient with vomiting and diarrhea is essential to correct hypovolemia, dehydration, acid-base imbalance, and serum electrolyte abnormalities. Prediction of acid-base or electrolyte disturbances is difficult; therefore, point of care testing is beneficial to optimize therapy. This article focuses on the pathophysiology and treatment of hypovolemia, dehydration, electrolyte disturbances, and acid-base derangements resulting from and associated with vomiting and diarrhea. 相似文献
32.
The digenean Bolbophorus damnificus infects commercial channel catfish Ictalurus punctatus, causing mortality, lower feed consumption, and reduced growth in surviving fish. The purpose of this study was to determine the length of time for which B. damnificus prodiplostomulum metacercariae (juvenile trematode stage that infects fish) would remain viable (parasite appearing to be intact or exhibiting movement) in channel catfish. Fish (n = 210) were infected with molecularly confirmed B. damnificus cercariae harvested from naturally infected marsh rams-horn snails Planorbella trivolvis. During the first sampling (at 20 d postinfection), 8.3 +/- 3.6 metacercariae/fish (mean +/- SD) were found in the host muscle and visceral organs. The channel catfish were then acclimated to a water temperature of either 18 degrees C or 28 degrees C. After 11 months, 6.8 +/- 3.5 and 5.9 +/- 3.0 metacercariae/fish were found in groups held at 18 degrees C and 28 degrees C, respectively. The mean number of parasites per fish did not significantly differ between fish held at the two temperatures and did not significantly decline over time at either temperature. Fish examined from 13 to 30 months postinfection all contained viable metacercariae that were morphologically and molecularly identified as B. damnificus. At 18 months, 12 metacercariae (of which 11 were intact and 10 displayed movement) were found in the one fish sampled; at 30 months, the last fish sampled contained three intact metacercariae (one displayed slight movement). Our results indicate that B. damnificus metacercariae can remain viable in channel catfish for at least an 18-30-month production cycle during which they have the potential to affect fish growth; in addition, infected fish may serve as intermediate hosts for these metacercariae for at least 2.5 years postinfection. 相似文献
33.
Simpson BS Landsberg GM Reisner IR Ciribassi JJ Horwitz D Houpt KA Kroll TL Luescher A Moffat KS Douglass G Robertson-Plouch C Veenhuizen MF Zimmerman A Clark TP 《Veterinary therapeutics : research in applied veterinary medicine》2007,8(1):18-31
Canine separation anxiety is a common behavioral problem presented to veterinarians. Associated behaviors are distressing to both dog and owner, have the potential to disrupt the human-companion animal bond, and may lead to euthanasia. The results of this study demonstrate the clinical efficacy and safety of Reconcile (fluoxetine, 1 to 2 mg/kg/day [0.45 to 0.91 mg/lb/day]), in conjunction with behavior management, for the treatment of canine separation anxiety. The beef flavored chewable formulation was palatable to treated dogs and easy to administer. This study provides to veterinarians and owners valuable information about an effective separation anxiety treatment plan that combines use of Reconcile with behavior modification. 相似文献
34.
Cooper RG 《Tropical animal health and production》2007,39(6):439-442
Data from post-mortem and field studies were obtained that discussed poisoning in ostriches following ingestion of toxic plants.
From the notes, all plants studied caused death in ostriches and there was systemic organ damage. Poisoning from Sarcostemma viminale (Melktou) resulted in beak patting, muscular tremors and head flopping, followed by collapse and violent kicking before death.
Ingestion of Combretum oatesii (Red wings) seeds from plants in free grazing pastures resulted in vomiting, restlessness, eyelid flicking, collapse and
kicking movements. Dichapetalum cymosum (Gifblaar) killed an ostrich after episodes of shaking legs, rapid respiration and bradycardia and hyperaemia of the lungs,
liver and kidneys. Poisoning from Senecio sceleratus (Ragwort) caused skin haemorrhages and bleeding in tracheal mucous membranes, the pericardium, diaphragm and interperitoneal
membrane. Consumption of drupes from Melia azedarach (Syringa berry) caused muscle tremors, kicking movements and respiratory distress. Lantana camara (Cherry pie) poisoning resulted in extremely inflamed eyes with copious yellow exudates extending down their beaks and onto
their necks. Bentonite was administered by gavage at a dose of 5 g/kg. Poisoning in these cases is usually associated with
the farmer allowing his/her birds to roam free-range in paddocks in which toxic plants are growing. Toxic plants should be
removed from grass cut for hay.
The author is willing to send photographs of all poisonous plants if requested by a reader. 相似文献
35.
Rosine Manishimwe Kizito Nishimwe Lonzy Ojok 《Tropical animal health and production》2017,49(6):1101-1106
The irrational use of antibiotics in humans and animals is highly related to the emergence and increase of antibiotic-resistant bacteria worldwide. A cross-sectional survey aimed at evaluating the current level of practices regarding antibiotic use in farm animals in Rwanda was carried out countrywide. Interviews were conducted on 229 farmers rearing different types of animals. The study has revealed that almost all respondent farmers could name at least one antibiotic used in farm animals and peni-streptomycin was named by most of them (95.6%). The use of antibiotics in farm animals was observed in the majority of respondents (97.4%). It was found that 44.4 and 26.5% of respondents reported that they used antibiotics for disease prevention and growth promotion, respectively. The use of non-prescribed antibiotics in animals was also reported by more than the half of respondent farmers (55.6%). The majority of farmers had a moderate level of practices regarding antibiotic use in farm animals (73.5%), very few had a high level (26%) and only one respondent had a low level. The high level of practices in regard to antibiotic use in animals was associated with the location of the farm, the type of reared animals, and the rearing system. The results of this study give an insight into antibiotics usage practices in farm animals in Rwanda. The generated information can guide sensitizations and promotions of the prudent use of antibiotics among farmers in order to limit the increase of antibiotic resistance in the country. 相似文献
36.
Andrew J Niehaus 《Veterinary Clinics of North America: Food Animal Practice》2008,24(2):349-58, viii
Abomasal diseases are common in cattle. Many of these diseases can be managed surgically. This article briefly discusses the various classifications of abomasal diseases. It focuses on the surgical treatment of these diseases. Surgical principles of conventional surgery and minimally invasive techniques are discussed. 相似文献
37.
Peregrine AS McEwen B Bienzle D Koch TG Weese JS 《The Canadian veterinary journal. La revue veterinaire canadienne》2006,47(1):80-82
From 1991 to 2003, 24 cases of larval cyathostominosis were diagnosed at postmortem in equids, 15 (63%) from 2001 to 2003. Cases occurred from September to May, the majority from October to December. Median age was 12 mo. Diarrhea, colic, and weight loss were common clinical signs. Hypoalbuminemia and microcytosis were consistent findings. 相似文献
38.
39.
Mersha Chanie Tamiru Negash Asegedech Sirak 《Tropical animal health and production》2010,42(6):1103-1109
Ectoparasites are the major causes of skin lesions in animals. Clinical, skin scraping examination, and histopathological
studies were conducted to identify and characterize skin lesions in small ruminants caused by ectoparasites. Mange mites,
lice, sheep keds, and ticks were collected from the skin of affected animals for species identification. Skin biopsies were
collected from affected part of the skin and fixed in 10% neutral buffered formalin for histopathology. Of 1,000 sheep and
600 goats examined, 815 (81.50%) sheep and 327 (54.5%) goats were infested with one or more types of ectoparasites. Sarcoptes scabiei var ovis, Demodex ovis, Psoroptes ovis, Bovicola ovis, Melophagus ovinus, and Amblyomma variegatum and other tick species were identified from sheep. S. scabiei var caprae, Demodex caprae, Linognathus stenopsis, and A. variegatum and other tick species were identified from goats. Gross skin lesions or defects observed on the skin include stained and
ragged wool, loss of wool/hair, nodules, crusts, lichenification, and fissuring. Microscopic evaluation of H and E stained
skin sections revealed lesions in the epidermal layer such as hyperkeratosis, acanthosis, and melanin inconsistency on the
basal cells of the epidermis. Follicular keratosis, perifolliculitis, frunculosis, perivasculitis, and aggregates of inflammatory
cells (of acute and chronic type) with fibrosis were experiential in the dermal layer of the skin. Most of the skin lesions
caused by ectoparasites are overlapping. Thus, ectoparasites control program should be executed to reduce skin lesions as
skins are the major export commodity of the country. 相似文献
40.
Denis M Lacy-Hulbert SJ Buddle BM Williamson JH Wedlock DN 《Veterinary research communications》2011,35(3):145-156
The presence, phenotype and function of Streptococcus uberis-specific T cells in the mammary gland secretion (MGS) and blood of cows exposed to S. uberis were assessed. MGS T cells in the udder were purified and incubated with autologous blood monocytes as antigen-presenting
cells (APC). Most cows, irrespective of prior S. uberis infection status and lactation status, were shown to have S. uberis-specific T cells both in MGS and in the blood. When cells from a subgroup of cows were studied, it was found that the S. uberis-specific T cells produced high levels of interferon-gamma (IFN-γ), but low levels of interleukin-10 (IL-10). A high percentage
of responding T cells were of the CD8
+
memory (CD45RO) subset. T cells from the MGS specific for S. uberis were propagated from animals during the drying off period and expanded in vitro using interleukin-2 (IL-2) and S. uberis antigens. This led to the accumulation of T cells of the CD8
+
subset bearing memory cell markers (CD45A
−
, CD45RO
+
), which released high levels of IFN-γ. Four of the five T cell lines derived from the MGS of three animals had substantial
direct killing activity towards S. uberis in vitro. It is concluded that there is an emergence of S. uberis-specific bactericidal T cells in the MGS of cows after infection or environmental exposure to S. uberis. Vaccines aimed at activating and expanding this T cell population in the mammary glands of cattle may offer an avenue for
the prevention of mastitis caused by S. uberis. 相似文献