首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   16907篇
  免费   24篇
林业   3675篇
农学   1316篇
基础科学   138篇
  2823篇
综合类   783篇
农作物   2124篇
水产渔业   1796篇
畜牧兽医   1274篇
园艺   1112篇
植物保护   1890篇
  2021年   5篇
  2020年   8篇
  2019年   9篇
  2018年   2751篇
  2017年   2705篇
  2016年   1181篇
  2015年   71篇
  2014年   20篇
  2013年   26篇
  2012年   811篇
  2011年   2146篇
  2010年   2109篇
  2009年   1259篇
  2008年   1333篇
  2007年   1605篇
  2006年   48篇
  2005年   115篇
  2004年   119篇
  2003年   168篇
  2002年   68篇
  2001年   23篇
  2000年   48篇
  1999年   11篇
  1997年   7篇
  1995年   8篇
  1994年   5篇
  1993年   20篇
  1992年   20篇
  1991年   11篇
  1990年   8篇
  1989年   15篇
  1988年   18篇
  1987年   8篇
  1986年   15篇
  1985年   4篇
  1984年   7篇
  1983年   12篇
  1979年   5篇
  1978年   5篇
  1977年   6篇
  1976年   8篇
  1974年   8篇
  1973年   9篇
  1972年   4篇
  1971年   8篇
  1970年   10篇
  1969年   9篇
  1968年   13篇
  1966年   6篇
  1913年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
This study determined in vitro anthelmintic efficacy of three plant species: Trema orientalis, Urtica dioica and Zanthozylum capense on nematode larvae of small ruminants. Dried leaf samples (40 g) were extracted in 70% ethanol, in portions of 10 g and concentrated to 100 ml. Half and one quarter of the original crude extract were both made to 100 ml. Rectal faecal material from 10 Merino sheep and 25 Nguni goats was pooled within species and thoroughly hand-mixed. Dung samples, each of 5 g were cultured for 12 days at 27 °C. On day 13, 4 plates were watered and 4 others treated with ethanol to correct for solvent effect on mortality. The design was 2 (animal species)?×?3 (plant species)?×?3 (extract concentrations). In each of three runs, three plates were treated with each crude extract in three incremental concentrations. Surviving L3 larvae were isolated, counted and mortalities became indices of anthelmintic efficacy. Data from nematode larval mortality were analysed to determine the effect of animal species, plant species, concentration and their interactions. Efficacy was affected by concentration (P?=?0.0001), animal species (P?=?0.0046), plant species (P?=?0.0572), the interactions of animal species and concentration (P?=?0.0010), plant species and concentration (P?=?0.0123) and concentration × animal × plant species (P?=?0.0435).  相似文献   
92.
The Salmonella sp. genus is identified in several species, and the zoonosis it causes is one of the most important types worldwide. The specifics of salmonellosis vary according to the function of the serovar involved, the species affected, age and predisposing factors. However, few cases of equine salmonellosis have been reported. This study presents ten confirmed salmonellosis cases in equines in southern Brazil. Six were adult animals with stress factors preceding the disease, while four were foals, three of which presented with hyperacute manifestations. The main clinical signs were diarrhea, anorexia, and hyperthermia. Lesions varied in distribution and severity, although fibrinonecrotic or necrohemorrhagic enteritis was observed in all animals, mainly in the large intestine (large colon and cecum—8/10) and small intestine (3/10). Substantial liquid content, mainly hemorrhagic, was observed in all animals. The most characteristic microscopic lesion was mucosa necrosis, which is often accompanied by fibrin deposition, followed by necrosis of follicular centers and vascular changes. Bacterial isolation revealed seven isolates. Five were serotyped, and the serovars Typhimurium and Anatum were associated with two cases each, while Muenster was associated with a case whose lesion pattern varied. Immunohistochemical staining was positive in all cases. All diagnoses were based on the clinical history, macroscopic and histological lesions, and the bacterial isolation and/or immunostaining associated with histological lesions.  相似文献   
93.
Dromedary camels complaining from conception failure or abortion were investigated and their herders interviewed in Al Ahsa province, Kingdom of Saudi Arabia (KSA) during 2013 and 2015. The most important reproductive disorder according to the responders is uterine infection (60.2%) followed by obesity (22.3%) then physiological conditions (hormonal disturbances; 7.8%), adhesions (3.9%) and repeat breeders (2.9%). Of the camel herders, 78.6% reported previous occurrence of abortion in their herds and 46% reported abortion cases in the last season (2015/2016), while 21.4% reported no history of abortion. Most of the responders (97.1%) do not call a veterinarian for cases of abortion in their herds and 53.4% do not discard aborted materials. The majority of the herders (76.7%) deny that handling aborted materials or touching vaginal fluids can result in human infection, or replied they do not know. Uterine swab samples were collected and tested by PCR for seven potential pathogens and sera tested for antibodies against bovine viral diarrhea virus (BVDV) and Brucella. Five pathogens were identified in infected uterine samples, namely Coxiella burnetii (36%), Campylobacter spp. (27%), Brucella spp. (17%), Salmonella spp. (13%), and Chlamydia spp. (7%). Sero-prevalence of Brucella and BVDV was 8.2 and 29.1% in overall sera, respectively, and varies with regard to the region. The findings of the present study demonstrate that reproductive disorders dominated by uterine infections and abortions are widespread in dromedary camels in KSA.  相似文献   
94.
A nitrogen (N) balance digestion trial was conducted to determine the protein requirement of collared peccaries (Pecari tajacu). In a 4 × 4 Latin square design, four captive adult male peccaries were fed four isoenergy diets containing four different levels of N (11.7, 16.3, 22.8, and 26.7 g N/kg of dry matter—DM). After 15 days of adaptation, a total collection of feces and urine was carried out for five consecutive days. Regression analyses between N intake and N in feces and urine allowed to calculate the metabolic fecal nitrogen (MFN = 2.3 g N/kg of dry matter intake—DMI) and daily endogenous urinary N (EUN = 185 mg N/kg0.75). Likewise, by regression analyses between consumption of nitrogen and the nitrogen balance (NB = N ingested ? N excreted, mg N/kg0.75), a daily requirement of 514 mg N/kg0.75 was calculated. Therefore, if food intake is unrestricted, collared peccaries require a minimum in their diet of about 5.4% crude protein on DM basis. These values are almost as low as those found for browsing and frugivorous wild ruminants, which reinforce the proposition that peccaries’ digestive physiology is nearer to that of domestic and wild ruminants than domestic pigs. This relatively low protein requirement of collared peccary and its great ability to digest protein reveal the relevance of the forestomach for the species on nitrogen/protein metabolism and allow the use of diets with lower crude protein levels than the commercial ones used for the domestic pig, which reduces feed costs.  相似文献   
95.
Brucellosis is a zoonotic disease worldwide distributed and having the economic as well as public health importance. The prevalence of brucellosis among sheep flock having history of abortions was studied. A total of 229 samples comprising of 157 blood and 72 clinical samples (vaginal swabs) were collected from 157 animals. Clinical samples were processed for the isolation of Brucella melitensis. Serum samples (n = 157) were tested by Rose Bengal plate test (RBPT) and i-ELISA. A total of 68 (43.31%) and 104 (66.24%) samples were positive by RBPT and ELISA, respectively. Brucella isolates (n = 2) were recovered from clinical samples. Both isolates demonstrated amplification for bcsp 31 and IS711 genes. On AMOS PCR, both the isolates amplified at 731 bp, i.e., belongs to B. melitensis species. The incidence of B. melitensis in a migratory flock warns the thorough testing and culling of Brucella-infected sheep from the flock on a continuous basis; otherwise, such incidence will be routine and poor farmers will be at a loss.  相似文献   
96.
Alternative poultry production with special reference to free range broilers has increased significantly since the nineties in many regions of the world. Numerous factors influence the productive performance of this type of broilers: genotype (namely the use of naked neck animals), feeding and access to an outdoor area. The aim of this paper is to study the influence of each of these factors on the productive performance of free range broilers under commercial rearing conditions. A total of 3200, day old chicks of both sexes from naked neck and normally feathered genotypes were used in this trial. After a joint initiation phase, animals were divided into four different treatments with the combination of two concentrates (high vs low energy content) and management (access to outside park or not). Experiment lasted a total of 12 weeks. Live weight date was recorded weekly and a samples of animals from the trial were sacrificed at the age of 8, 10 and 12 weeks, when carcass characteristics were determined. Besides sex, the only factor that seems to affect growth characteristics was genotype as naked neck animals had poorer growth rates than normally feathered. No effect was detected on carcass yields and percentages of carcass components for any of the variables. From the data presented in this trial the practises associated with free range production are of relative inconsequence to the technical animal production parameters and can only be justified by a pressing need to differentiate these products from standard poultry products in what concerns both welfare issues and meat characteristics. The results also indicate that genetic material from alternative poultry production in Europe can be a useful option in poultry production development projects in the tropics.  相似文献   
97.
In recent years host antimicrobial peptides and proteins have been recognised as key mediators of the innate immune response in many vertebrate species, providing the first line of defense against potential pathogens. In chickens a number of cationic antimicrobial peptides have been recently identified. However, although these peptides have been studied extensively in the avian gastrointestinal tract, little is known about their function in the chicken reproductive organs and embryos. Chicken Liver Expressed Antimicrobial Peptide-2 (cLEAP-2) has been previously reported to function in protecting birds against microbial attack. The aim of this study was to investigate the expression of cLEAP-2 gene in the chicken reproductive organs, as well as in chicken embryos during embryonic development, and to determine whether cLEAP-2 expression in the chicken reproductive organs was constitutive or induced as a response to Salmonella enteritidis infection. RNA was extracted from ovary, oviduct, testis and epididymis of sexually mature healthy and Salmonella infected birds, as well as from chicken embryos until day ten of embryonic development. Expression analysis data revealed that cLEAP-2 was expressed in the chicken ovary, testis and epididymis as well as in embryos during early embryonic development. Quantitative real-time PCR analysis revealed that cLEAP-2 expression was constitutive in the chicken epididymis, but was significantly up regulated in the chicken gonads, following Salmonella infection. In addition, expression of cLEAP-2 during chicken embryogenesis appeared to be developmentally regulated. These data provide evidence to suggest a key role of cLEAP-2 in the protection of the chicken reproductive organs and the developing embryos from Salmonella colonization.  相似文献   
98.
This project was conducted to investigate the comparative efficiency of competitive ELISA (cELISA), standard Agar Gel Immunodiffusion Test (AGID) and Precipitinogen Inhibition Test (PIT) for the diagnosis of Peste des Petits Ruminants (PPR) in Pakistan. To deal with this, serum samples from 198 sheep and 82 goats were collected from three different government livestock farms and all the samples were run simultaneously with the three serological tests. The samples found positive for PPR antibodies through cELISA, AGID and PIT were 96 (34.2%), 60 (21.4%) and 72 (25.7%), respectively. Kappa statistics were applied to evaluate the concordance between the laboratory-based test (cELISA) and field-based tests (AGID and PIT). Kappa statistics scores for cELISA versus AGID and PIT were 0.6343 (95% Confidence Interval CI 0.5231–0.7456) and 0.7134 (95% Confidence Interval CI 0.5987–0.8281), respectively, which indicate a “substantial” agreement between cELISA and AGID and “significant” agreement between cELISA and PIT. AGID and PIT revealed relative diagnostic sensitivities with cELISA of 59.3% and 69.7% and relative diagnostic specificities of 98.3% and 97.2%, respectively. The data suggested that for mass screening and control of PPR, these serological tests proved practical in the absence of cELISA since they have high relative diagnostic specificities and a satisfactory relative diagnostic sensitivities.  相似文献   
99.
Verticillium dahliae, a soilborne plant pathogen, causes wilt disease in many important crops. We reported previously that the mating type gene MAT1-2-1 is spread to isolates of this asexual fungus. However, we did not determine whether V. dahliae is homothallic or heterothallic because the opposite mating type gene, MAT1-1-1, had not been identified. In the present study, we identified the MAT1-1-1 gene from an isolate lacking MAT1-2-1 and the mating type idiomorphs of V. dahliae. Each isolate we tested contained either the MAT1-1 or MAT1-2 idiomorph, indicating that the asexual fungus V. dahliae is potentially heterothallic.  相似文献   
100.
This study aims to evaluate the conjunctiva colour-based FAMACHA score (FS) coupled with a body condition score (BCS), haemogram and stressor hormone level estimation, in identifying post-mortem (PM)/coproscopically proven individuals wanting therapy for economically important gastrointestinal (GI) helminths, Haemonchus contortus, in the small ruminants. The incidence of haemonchosis was significantly (p < 0.05) higher (60.81%) in the ruminants with FS = 3. The H. contortus count in the animals with FS 2, 3 and 4 was 23.2 ± 0.37, 62 ± 2.5 and 74 ± 3.2 (p < 0.05) [positive correlation (r = 0.841 in goats; r = 0.828 in sheep, p < 0.05)], respectively, with corresponding 2.8 ± 0.15, 2 ± 0.3 and 2 ± 0.16 BCS (negative correlation, p > 0.05). The infected animals of FS 2, 3 and 4 measured 8.2 ± 0.0, 7.5 ± 0.23 and 6.7 ± 0.34 g/dl Hb (r = ?0.452, p = 0.01) in goats/9.3 ± 0.8, 8.6 ± 0.5 and 7.6 ± 0.3 g/dl Hb (r = ?0.511, p = 0.05) in sheep with 21.2, 19.8 ± 1.8 and 17.8 ± 0.2% PCV (r = ?0.369, p = 0.05) in goats/26.7 ± 1.2, 22.2 ± 0.2 and 20.9 ± 0.6% PCV (r = ?0.251, p = 0.03) in sheep, respectively. The FS 2, 3 and 4 infected goats/sheep measured 6.1 ± 0, 7.9 ± 1.0 and 9.5 ± 0.9 (p < 0.05)/5.8 ± 2.3, 6.9 ± 1.2 and 7.8 ± 0.2% (p < 0.05) mid-granulocyte [(r = 0.928 (goats)/0.834 (sheep), p < 0.05], while the cortisol level was 15.6, 23 ± 4.5 and 42 ± 2.3 (p = 0.23)/12.1 ± 0, 15.9 ± 1.2 and 24 ± 3.4 (p = 0.29) μg/dl, respectively. The infected ruminants recorded low (p < 0.05) level of Hb/PCV while high level of mid-granulocytes/cortisol. Specificity of FAMACHA test was maximized (100%) when FS = 4 was considered anaemic, but sensitivity was low (35.29% in goats; 25% in sheep). The false negatives was 5.9 (goat)/12.5 (sheep)% when FS ≥ 3 was considered anaemic. The small ruminants with FS ≥ 3, BCS ≤ 2.5, Hb ≤ 7.5 g/dl (goats)/8.6 g/dl (sheep), PCV ≤ 19.8% (goats)/22.2% (sheep) and mid-granulocyte ≥7.9% (goats)/6.9 ± 1.2% (sheep) can be subjected to target-selective treatment for haemonchosis in the field simultaneously maximizing the economic benefit to the farmers.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号