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   20130篇
  免费   232篇
  国内免费   247篇
林业   1155篇
农学   424篇
基础科学   338篇
  2215篇
综合类   5406篇
农作物   694篇
水产渔业   410篇
畜牧兽医   8877篇
园艺   500篇
植物保护   590篇
  2023年   109篇
  2022年   143篇
  2021年   134篇
  2020年   110篇
  2019年   182篇
  2018年   176篇
  2017年   112篇
  2016年   137篇
  2015年   137篇
  2014年   364篇
  2013年   257篇
  2012年   1411篇
  2011年   1641篇
  2010年   507篇
  2009年   378篇
  2008年   1319篇
  2007年   1406篇
  2006年   1305篇
  2005年   1212篇
  2004年   1098篇
  2003年   1088篇
  2002年   955篇
  2001年   713篇
  2000年   931篇
  1999年   464篇
  1998年   170篇
  1997年   189篇
  1996年   134篇
  1995年   191篇
  1994年   160篇
  1993年   183篇
  1992年   183篇
  1991年   157篇
  1990年   162篇
  1989年   137篇
  1988年   129篇
  1987年   123篇
  1986年   127篇
  1985年   115篇
  1984年   133篇
  1983年   101篇
  1982年   94篇
  1981年   79篇
  1980年   74篇
  1974年   48篇
  1972年   44篇
  1971年   45篇
  1963年   53篇
  1960年   45篇
  1958年   55篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Poisonings can cause reduced performance and severe economic loss in farm animals. A swift and targeted action is required from veterinarians. We have established a computer-based decision support system for poisonings in ruminants and pigs. The system offers access to the most recent information available in clinical toxicology of farm animals. Towards this goal, relevant reports from the peer-reviewed literature were evaluated and organised according to the requirements of a structured database. The information provided for each toxic substance includes a summary of its chemical and physical properties, sources, commercial uses or natural occurrences, toxicokinetic data, mechanisms of action, threshold doses, clinical symptoms with brief case reports, sampling and analytical results, post-mortem abnormalities, differential diagnoses, therapeutic guidelines and references to the literature. This decision support system has been programmed with two user-friendly search functions: a search tool that allows the choice of clinical and pathological findings, and another function that serves to find a substance using its chemical name, the class of compounds to wich it belongs, a possible source or one of its main applications. CliniTox can be accessed directly via our webserver (http://www.clinitox.ch).  相似文献   
82.
REASONS FOR PERFORMING STUDY: Sacroiliac joint (SIJ) disease is associated with poor hindlimb action, lameness and poor performance in horses. However, little is known about the biomechanics of this low-motion joint. OBJECTIVES: To determine in vitro the capacities of movement of the SIJ in the sagittal plane, and to test the effect of a sacrosciatic and sacrotuberal desmotomy on its stabilisation. METHODS: Six anatomical specimens underwent cycles of flexion-extension of the lumbosacral joint (LSJ) before and after desmotomy. Kinematic triads were linked rigidly to the sacrum, spinous process of vertebra L5 and iliac wing. Angles were measured using a joint coordinate system based on anatomical frames. RESULTS: The LSJ underwent regular movements of flexion and extension (overall mean +/- s.d. range 23.4 +/- 1.6 degrees). The only recorded movement of the SIJ was a nutation during LSJ flexion (overall mean +/- s.d. 0.8 +/- 0.5 degrees). Desmotomy induced an increase of that nutation (overall mean +/- s.d. 1.7 +/- 0.2 degrees). CONCLUSIONS AND POTENTIAL RELEVANCE: Movements of the SIJ were small and coupled only with the flexion of the LSJ. The ligaments surrounding the SIJ have a strong effect on the stabilisation of this joint. Due to the limited amount of movement, its biomechanical study in vivo seems to be difficult. Further in vitro studies would be useful to determine the role of each ligament, to better understand the clinical consequences of the tears frequently observed during necropsy.  相似文献   
83.
The brain of a 6-year-old Holstein cow, which showed progressive neurologic symptoms during several months, was examined by histopathologic methods. Many round or oval-shaped cytoplasmic inclusions were observed, mainly in neurons of the temporal lobe and the hippocampus. Those inclusions were faintly eosinophilic with hematoxylin and eosin and positive with Bielschowsky's silver stain. Immunohistochemically, the inclusions were recognized by antiubiquitin and antiphosphorylated tau antibodies. Ultrastructurally, the inclusions were globular and well demarcated from the rest of the cytoplasm, lacked limiting membranes, and were mainly composed of straight fibrils about 15 nm in width. The structure of the inclusions was similar to that of Pick bodies in Pick's disease of humans. The pathogenesis of this bovine condition is not known.  相似文献   
84.
使用。管:就是根据《银行账户管理办法》规定,将四类账户的开户条件输人同城票据交换主机,对不符合条件开立的账户,同城票据交换机就不予承认,视其为非法账户,使其无法进人同城票据交换网络,其账户的资金就无法运作。发证:对同城票据交换网络予以认可的账户,给予发证。基本存款账户仍由人民银行发证,  相似文献   
85.
Growth and digestibility experiments were conducted on growing East African type goats offered Chloris gayana hay supplemented with one of three high-protein (119–128 g CP/kg DM) legume hays, Cassia rotundifolia (cassia), Lablab purpureus (lablab) or Macroptilium atropurpureum (siratro), and crushed maize to investigate the feed intake, digestibility, growth and urinary excretion of purine derivatives. Goats in the supplemented groups had higher total dry matter and nitrogen intakes and higher N retention and body mass gains than unsupplemented counterparts. The digestibility of dry matter, organic matter and neutral detergent fibre were increased by protein supplementation. Animals on supplemented diets had higher fractional outflow rates of particulate matter from the rumen. The production of protein by ruminal microbes and the efficiency of microbial N production were increased by supplementation. It was concluded that a mixture of low-quality grass hay (61.9 CP/kg DM) and either cassia, lablab or siratro hay, and maize grain can provide a productive balanced diet for growing goats.  相似文献   
86.
87.
Four sentinel herds comprising cattle, sheep and goats were established at various localities in Saudi Arabia. Maternal bluetongue antibodies were detected in all four sentinel herds but disappeared in 4-6 months, immediately followed by seroconversion in all. Serological results indicated that the animals were recently exposed to BT virus serotypes 10, 12, 15 and 20. The epidemiology of the disease in Saudi Arabia is discussed.  相似文献   
88.
89.
Kumar, V., Madabushi, R., Lucchesi, M. B. B., Derendorf, H. Pharmacokinetics of cefpodoxime in plasma and subcutaneous fluid following oral administration of cefpodoxime proxetil in male beagle dogs. J. vet. Pharmacol. Therap. 34 , 130–135. Pharmacokinetics of cefpodoxime in plasma (total concentration) and subcutaneous fluid (free concentration using microdialysis) was investigated in dogs following single oral administration of prodrug cefpodoxime proxetil (equivalent to 5 and 10 mg/kg of cefpodoxime). In a cross over study design, six dogs per dose were utilized after a 1 week washout period. Plasma, microdialysate, and urine samples were collected upto 24 h and analyzed using high performance liquid chromatography. The average maximum concentration (Cmax) of cefpodoxime in plasma was 13.66 (±6.30) and 27.14 (±4.56) μg/mL with elimination half‐life (t1/2) of 3.01 (±0.49) and 4.72 (±1.46) h following 5 and 10 mg/kg dose, respectively. The respective average area under the curve (AUC0–∞) was 82.94 (±30.17) and 107.71 (±30.79) μg·h/mL. Cefpodoxime was readily distributed to skin and average free Cmax in subcutaneous fluid was 1.70 (±0.55) and 3.06 (±0.93) μg/mL at the two doses. Urinary excretion (unchanged cefpodoxime) was the major elimination route. Comparison of subcutaneous fluid concentrations using pharmacokinetic/pharmacodynamic indices of fT>MIC indicated that at 10 mg/kg dose; cefpodoxime would yield good therapeutic outcome in skin infections for bacteria with MIC50 upto 0.5 μg/mL while higher doses (or more frequent dosing) may be needed for bacteria with higher MICs. High urine concentrations suggested cefpodoxime use for urinary infections in dogs.  相似文献   
90.
Boar taint is characterized by an unpleasant taste or odor in intact male pigs and is primarily attributed to increased concentrations of androstenone and skatole and to a lesser extent by increased indole. The boar taint compounds skatole and indole are produced by gut bacteria, metabolized in the liver, and stored in the fat tissue. Androstenone, on the other hand, is synthesized in the testis along with testosterone and estrogens, which are known to be important factors affecting fertility. The main goal of this study was to investigate the relationship between genetic factors involved in the primary boar taint compounds in an attempt to discover ways to reduce boar taint without decreasing fertility-related compounds. Heritabilities and genetic correlations between traits were estimated for compounds related to boar taint (androstenone, skatole, indole) and reproduction (testosterone, 17β-estradiol, and estrone sulfate). Heritabilities in the range of 0.47 to 0.67 were detected for androstenone concentrations in both fat and plasma, whereas those for skatole and indole were slightly less (0.27 to 0.41). The genetic correlations between androstenone in plasma and fat were extremely high (0.91 to 0.98) in Duroc and Landrace. In addition, genetic correlations between androstenone (both plasma and fat) and the other sex steroids (estrone sulfate, 17β-estradiol, and testosterone) were very high, in the range of 0.80 to 0.95. Furthermore, a genome-wide association study (GWA) and a combined linkage disequilibrium and linkage analysis (LDLA) were conducted on 1,533 purebred Landrace and 1,027 purebred Duroc to find genome regions involved in genetic control of the boar taint compounds androstenone, skatole, and indole, and sex hormones related to fertility traits. Up to 3,297 informative SNP markers were included for both breeds, including SNP from several boar taint candidate genes. From the GWA study, we found that altogether 27 regions were significant at a genome-wide level (P < 0.05) and an additional 7 regions were significant at a chromosomal level. From the LDLA study, 7 regions were significant on a genome-wide level and an additional 7 regions were significant at a chromosomal level. The most convincing associations were obtained in 6 regions affecting skatole and indole in fat on chromosomes 1, 2, 3, 7, 13, and 14, 1 region on chromosome 6 affecting androstenone in plasma only, and 5 regions on chromosomes 3, 4, 13, and 15 affecting androstenone, testosterone, and estrogens.  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