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   1583篇
  免费   116篇
林业   141篇
农学   108篇
基础科学   11篇
  359篇
综合类   61篇
农作物   101篇
水产渔业   205篇
畜牧兽医   571篇
园艺   33篇
植物保护   109篇
  2024年   2篇
  2023年   24篇
  2022年   40篇
  2021年   77篇
  2020年   89篇
  2019年   72篇
  2018年   66篇
  2017年   86篇
  2016年   81篇
  2015年   60篇
  2014年   74篇
  2013年   116篇
  2012年   128篇
  2011年   131篇
  2010年   86篇
  2009年   61篇
  2008年   78篇
  2007年   87篇
  2006年   52篇
  2005年   49篇
  2004年   51篇
  2003年   45篇
  2002年   35篇
  2001年   18篇
  2000年   8篇
  1999年   6篇
  1998年   8篇
  1997年   7篇
  1996年   5篇
  1995年   4篇
  1994年   2篇
  1993年   5篇
  1992年   6篇
  1991年   3篇
  1990年   4篇
  1989年   2篇
  1987年   5篇
  1986年   2篇
  1985年   2篇
  1982年   1篇
  1978年   1篇
  1977年   1篇
  1975年   3篇
  1973年   2篇
  1972年   3篇
  1971年   2篇
  1970年   2篇
  1966年   2篇
  1965年   1篇
  1963年   1篇
排序方式: 共有1699条查询结果,搜索用时 15 毫秒
991.
The present study evaluated Nelore cattle with different degrees of resistance to natural infections by gastrointestinal nematodes. One hundred weaned male cattle, 11-12 months of age, were kept on the same pasture and evaluated from October 2003 to February 2004. Faecal and blood samples were collected for parasitological, haematological and immunological tests. In February 2004, the 10 most resistant and the 10 most susceptible animals were selected based on individual means of nematode faecal egg counts (FEC). Such animals were slaughtered for worm burden determination and nematode species identification. The repeatability estimates for FEC (+/-S.D.), log-transformed FEC and packed-cell volume (PCV) in all animals were 0.3 (+/-0.05), 0.26 (+/-0.04) and 0.42 (+/-0.05), respectively. The resistant group showed lower FEC and worm burdens than the susceptible group (P<0.05). There were no significant differences between groups regarding mean body weight, weight gain, PCV and total serum protein values (P>0.05). The resistant group showed higher total serum IgE levels (P<0.05) and higher mean eosinophil blood counts. However, the latter was statistically significant only 42 days after the beginning of the study. Nematodes Cooperia punctata and Haemonchus placei were predominant and the correlation between Cooperia and Haemonchus burdens was 0.64 (P<0.05), which indicated that animals presenting increased numbers of one of those genera probably had increased numbers of the other. The current study provides further evidence of IgE active role in nematode immunity and suggests that total serum IgE level might serve as an additional marker to select Nelore cattle that are responsive to H. placei and C. punctata infections.  相似文献   
992.
Giardia cyst contamination of mussels (Mytilus galloprovincialis), raw and treated waste waters and water from rivers that flow into four Galician estuaries (NW Spain), where bivalve molluscs are cultured for human consumption, was studied. The high prevalence of contamination in mussels (41.8%, n=184), raw waste water (90.9%, n=11), treated waste water (87.5%, n=16) and in samples of river water (85.7%, n=7), with cyst counts of 9.8-1800.0, 7.0-2541.0 and 1.0-29.3 cysts l(-1), respectively, illustrate the wide distribution of this enteropathogen in the environment and the potential risk to public health associated with the consumption of raw or undercooking bivalves and use of these estuaries for recreational purposes.  相似文献   
993.
Antibodies against Ehrlichia canis, the cause of canine monocytic ehrlichiosis, have been reported previously in clinically ill and stray dogs from Portugal. In this study, the 16S rRNA gene of E. canis was detected by the polymerase chain reaction (PCR) in 12/55 (22%) of dogs with suspected tick-borne disease in the Algarve region in Portugal.  相似文献   
994.
The surface-associated proteins play a key role in bacterial physiology and pathogenesis, and are the major targets in the development of new vaccines. These proteins contribute to the adaptation of bacteria to different hosts and environments. To study differences at the genomic level, we first sequenced the whole genome of Streptococcus iniae from fish (IUSA-1 strain) and compared it to Streptococcus iniae from human (9117 strain), revealing a high similitude between both strains. To gain further insights into host- and environment-specific differences, we then studied proteins in silico and by High Performance Liquid Chromatography. This approach successfully identified 54 secreted and surface proteins, including several proteins involved in cell wall synthesis and transport of solutes, as well as proteins with yet unknown function. These proteins highlight as interesting targets for further investigation in the interaction between Streptococcus iniae and its environment. Results reported in this study have shown a first analysis about the predicted and experimental associated proteins of Streptococcus iniae isolated from two different hosts: human and fish.  相似文献   
995.
996.
Mammalian skeletal muscle expresses splice variants of neuronal nitric oxide synthase (nNOS). Skeletal muscles have a metabolically heterogeneous population of myofibers, and fiber composition in equine skeletal muscle is correlated with athletic ability in endurance events. In this study, we investigated whether nNOS expression in equine skeletal muscle is related to fiber type and endurance training. Biopsy samples obtained from the gluteus medius of sedentary- (SH) and endurance-trained (TH) horses were examined for the electrophoretic mobility of myosin heavy chain (MHC) and NOS activity. Serial tissue cross-sections were stained for myosin ATPase and nicotinamide adenine dinucleotide (NADH) reductase, and also immunostained for nNOS. The gluteus medius of TH had higher levels of nNOS expression and activity when compared to muscle from SH. In SH, nNOS was restricted to the subsarcolemmal area while in TH nNOS was also present at cytoplasmic sites. A splice variant of nNOS was heterogeneously distributed among the different myofibers, its expression being higher in fast-oxidative-glycolytic type IIA fibers than in fast-glycolytic type IIX fibers and absent in slow-twitch type I fibers. Trained horses had a significantly higher relative content of type IIA fibers, a greater oxidative capacity, and a lower percentage of type IIX fibers when compared with SH. The differences in muscle fiber typing between the 2 groups of horses reflected alterations that probably resulted from the endurance-training program. Overall, these results show that nNOS is differentially expressed and localized in the gluteus medius according to the fiber type and the athletic conditioning of the horses.  相似文献   
997.
Evaluating phenotypic diversity makes it possible to identify discrepancies in aptitudes among animals of different genetic bases, which is an indicator of adaptive or selective differences between populations. The objective of this work was to evaluate the morphofunctional diversity of 452 male and female adult equines (Arabian, Quarter Mile, Pantaneiro, and Criollo breeds, and undefined crossbreeds of horses and mules) raised in the Pantanal biome (Brazil). Linear measurements were performed to estimate conformation indexes. Initially, a discriminant analysis was performed, regardless of the animal’s size, followed by factor analysis. The factors were characterized and used as new variables. The diversity among equines and their relationship with the factors were evaluated using multivariate analysis. The factors were classified according to their decreasing importance: balance, rusticity, and robustness for the measurement factors; and load, ability, conformation, and equilibrium for the index factors. The genetic groups of equines have well-defined morphofunctional characteristics. The main differences are based on the rusticity and ability typologies in relation to those based on performance. Equines introduced to the Pantanal biome presented a more robust and compact body with good conformation. As a result, these horses may have superior athletic performance during equestrian activities when compared to the Pantaneiro local breed. However, this biotype may represent less rusticity (less adaptive capacity). Therefore, the regional breed can be equal or better in equestrian activities than breeds introduced to the Pantanal biome. Thus, breeders may cross horses from local breeds as an alternative to those introduced. Undefined crossbred male equines presented a different profile from the Pantaneiro breed, which may indicate little use of crossbreeds in breeding.  相似文献   
998.
Platelet-rich plasma (PRP) is a widely used hemocomponent that holds great promise in equine medicine due to its feasible production and regenerative therapy potential. Its use has been considered as a treatment for chronic laminitis, mainly in terms of its analgesic properties and because it can induce growth in affected hooves. The aim of this study was to evaluate the effect on hoof growth attributable to PRP applied in the coronary band of clinically healthy horses by comparing the responses to PRP, saline, and trimming alone. After randomization, the forelimbs of 9 horses received specific treatment at intervals of 33 days and were trimmed, measured, and radiographed at the same time. Neither hoof growth nor hoof angles were different between the treatment groups at any time point. The application of PRP in the coronary band of horses may be a safe procedure; however, it had no effect on the growth or conformation of hooves in clinically healthy horses.  相似文献   
999.
This study used discriminant analysis to evaluate body measures and sexual dimorphism in Mangalarga Marchador horses. Discriminant analysis is a multivariate method that generates functions to classify animals using a prior criterion. In this study a prior criterion is male or female. The study analyzed 25 linear and 11 angular measures obtained from 25 stallions and 56 mares registered with the Mangalarga Marchador Brazilian Breeders Association. Knee girth, cannon girth, chest width, chest girth, back-loin length, hip width, distance from elbow to knee, hind limb hoof length, head width, shoulder length, and body length were found to be linear measures that provided evidence of sexual dimorphism. Angular measures with evidence of sexual dimorphism were shoulder–humerus, metacarpal–phalanx, coxae–femur, and femur–tibial angles. Stallions were larger than mares for almost all linear measures, except for back-loin length, hip width, and distance from elbow to knee. Shoulder–humerus and coxal–femur angles were larger in mares, while metacarpal–phalanx and femur–tibial angles were larger in stallions. Using linear measures, two mares were classified as stallions and three stallions were classified as mares. For angular measures, two other mares were classified as stallions and three other stallions were classified as mares. The discriminant functions can be useful for the selection of horses and to avoid registration of animals not meeting the phenotypic standards of the breed association.  相似文献   
1000.
Objective: To describe and evaluate full‐thickness skin grafting of equine wounds. Study Design: Case series. Animals: Adult horses (n=6). Methods: A full‐thickness graft was harvested from the pectoral region with the horse anesthetized or standing and sedated after local anesthetic infiltration. Grafts were attached to the cutaneous margin of the wound with staples and/or sutures if the horse was anesthetized or if the recipient site was desensitized. Cyanoacrylate glue was used to attach the grafts to the cutaneous margin of the wound of 3 horses. Medical records were reviewed for history, physical examination findings, grafting technique, postoperative complications, and outcome. Results: Three horses had full‐thickness skin grafting to cover a fresh defect created by excision of a cutaneous neoplasm, and 3 horses had full‐thickness skin grafting to cover a fresh or granulating laceration. Grafts were completely accepted in 5 horses. The superficial layers of all grafts sloughed, but the final cosmetic appearance of accepted grafts was good. Conclusions: Full‐thickness skin grafting can be performed in standing sedated horses with good cosmesis, especially when the meshed graft is expanded minimally. Clinical Relevance: Good acceptance of a full‐thickness graft can be expected, regardless of whether the graft is applied to a fresh or granulating wound.  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