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   78799篇
  免费   4246篇
  国内免费   93篇
林业   3184篇
农学   2043篇
基础科学   461篇
  8558篇
综合类   15393篇
农作物   3124篇
水产渔业   3414篇
畜牧兽医   41679篇
园艺   844篇
植物保护   4438篇
  2019年   718篇
  2018年   1091篇
  2017年   1211篇
  2016年   1046篇
  2015年   902篇
  2014年   1189篇
  2013年   2618篇
  2012年   2111篇
  2011年   2572篇
  2010年   1616篇
  2009年   1728篇
  2008年   2592篇
  2007年   2403篇
  2006年   2284篇
  2005年   2134篇
  2004年   2074篇
  2003年   2134篇
  2002年   1921篇
  2001年   2384篇
  2000年   2438篇
  1999年   1869篇
  1998年   719篇
  1997年   711篇
  1996年   711篇
  1995年   805篇
  1993年   740篇
  1992年   1553篇
  1991年   1750篇
  1990年   1634篇
  1989年   1646篇
  1988年   1473篇
  1987年   1534篇
  1986年   1596篇
  1985年   1547篇
  1984年   1184篇
  1983年   1057篇
  1982年   704篇
  1979年   1155篇
  1978年   895篇
  1977年   755篇
  1975年   774篇
  1974年   1024篇
  1973年   1026篇
  1972年   1043篇
  1971年   993篇
  1970年   987篇
  1969年   903篇
  1968年   810篇
  1967年   799篇
  1966年   732篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
We report a case of diphenhydramine intoxication in a dog. A five month old intact male Labrador Retriever was presented after ingesting approximately 36 diphenhydramine tablets (50 mg/tablet; approximate ingested dose of 1800 mg or 67 mg/kg). Physical examination findings included severe ataxia, profound disorientation, severe continuous spastic muscle tremors, hyperthermia, tachycardia, tachypnea, and hyperesthesia. The dog was unresponsive to intravenous diazepam and phenobarbital, but rapidly responded to an intravenous bolus and subsequent continuous infusion of guaifenesin and supportive fluid therapy. The serum diphenhydramine level on admission was 537 ng/ml. The toxic level is not reported for dogs, but is considered>60 ng/ml in people. The dog was discharged 24 hours after admission with no apparent residual effects.  相似文献   
952.
Rabbit hemorrhagic disease (RHD) is an important cause of disease and mortality in wild and domestic European rabbits (Oryctolagus cuniculus) throughout the world. Testing for 2 distinct RHD virus types (RHDV/RHDVa and RHDV2) was carried out on samples collected from 684 rabbits submitted from veterinary practices and private owners throughout Europe between January 2015 and June 2017. Four (0.6%) were positive for RHDV/RHDVa and 257 (37.4%) were positive for RHDV2. RHDV/RHDVa was detected in individual samples from Germany and the Netherlands, while RHDV2 was found in animals from Germany, Great Britain, Luxembourg, The Netherlands, Spain, Switzerland, Poland, Belgium, Austria, Sweden, and Finland.  相似文献   
953.
The present study was carried out to investigate genetic diversity in Nile-Delta and Southern-Egypt buffalo populations in comparison with the Italian buffalo utilizing two microsatellite multiplexes. A total of 104 animals classified into three groups were used, 28, 38 and 38 representing the Nile-Delta, Southern-Egypt and Italian buffalo, respectively. The 15 studied microsatellites were CSSM38, CSSM70, CYP21, CSSM42, CSSM60, MAF65, BM0922, CSSM19, INRA006, ETH02, BM1706, BMC1013, CSSM47, INRA026 and CA004. All studied microsatellites showed allelic polymorphism. Number of polymorphic alleles ranged between 4 alleles (CSSM38, CSSM70 and CYP21) and 11 alleles (CA004). Pairwise Chi-square test for Nile Delta and Southern Egypt showed significant differences in allelic distribution at five loci, CSSM70, CSSM38, BM0922, ETH02 and BM1706. Italian buffalo showed the lowest percentage of observed heterozygotes (65%), while the Southern Egypt showed the highest (71%). Both the Italian and the Delta populations deviated significantly (P < 0.05) from HW equilibrium. Italian buffalo is relatively the most inbred population while the Southern-Egypt buffalo is the only outbred population. High level of genetic differentiation (FST estimates) between the Italian group and each of the Delta and Southern-Egypt group (0.083 and 0.076, respectively) was observed while Southern-Egypt group showed a lower level of genetic differentiation with the Delta group (0.014). Italian buffalo had the greatest genetic distance values with the two Egyptian groups (0.25 and 0.23) while much lower values between the Southern-Egypt and the Delta groups (0.06) was observed. Genetic variation between the Italian buffalo and the Egyptian buffalo was detected in 14 (out of 15) microsatellite loci. While a lower level (than that between Egyptian and Italian) of genetic variation between Southern-Egypt and Delta buffalo populations was expressed by 5 loci. It was concluded that the Southern-Egypt buffalo could be considered as distinct population from the Delta buffalo. In addition, Southern-Egypt group, being the only group with non-significant global deviation from HW equilibrium, the most heterozygous, and the only outbred population as well, is expected to respond more favorably to selection.  相似文献   
954.
Summary

The intravenous and oral pharmacokinetics of an amoxicillin and clavulanic acid combination (20 mg/kg of sodium amoxicillin and 5 mg/kg of potassium clavulanate) were studied in six goats. After intravenous administration the pharmacokinetics of both drugs could be described by an open two‐compartment model. Amoxicillin had a greater distribution volume (0.19 ± 0.01 l/kg) than clavulanic acid (0.15 ± 0.01 l/kg), whereas the distribution and elimination constants were higher for the latter, which was eliminated more quickly than amoxicillin. After oral administration of both drugs their pharmacokinetic behaviour was best described by an open one‐compartment model with first‐order absorption. Elimination half‐lives were twice as long after oral (2.15 ± 0.20 h and 1.94 ± 0.16 h for amoxicillin and clavulanic acid respectively) than after intravenous administration (1.20 ± 0.16 h and 0.86 ± 0.09, respectively). An apparent ‘flip‐flop’ situation was evident in this study. Bioavailability was 27% for amoxicillin and 50% for clavulanic acid.  相似文献   
955.
The larval development ol the southern African endemic clupeid Gilchristella aestuaria is described and illustrated from specimens collected in the Swartvlei and Sundays estuarine systems of the Cape Province. Free embryos have no visible gut, unpigmented eyes and bodies, and are dependent on the yolk sac contents for nutrition. This stage lasts until about 4 mm body length (BL) when the eyes become pigmented and a gut becomes visible. Between 4 mm and 7 mm BL melanophores on the ventral aspect of the body form, and the dorsal and caudal lin anlagen develop. Between 7 mm and 8 mm BL the swimbladder lorms, flexion occurs and the anal fin anlage develops. By the 10 mm BL stage most of the skeletal elements have begun to differentiate, with the vertebral centra already showing signs of ossification. General ossification commences between 12 mm and 13 mm BL. All unpaired fins have the adult complement of rays by 15 mm BL. Scalation starts between 16 mm and 17 mm BL and is complete by 20 mm BL. Body depth increases gradually, from about 5% of BL in the early larval stages to >14% of BL in the juveniles. The pre-anal length decreases from about 87% of BL in the larvae to approximately 69% of BL in the juveniles. Head length increases from approximately 11% of BL in the larvae to 24-29% of BL in the juveniles. The larval snoui is initially 2% of BL, increasing to 7% of BL in the juvenile stages owing to the development of jaw elements.  相似文献   
956.
Although conjugated linoleic acid (CLA) shows inhibitory effects on histamine release, eicosanoid production and pruritus in laboratory rodents, its use in canine atopic dermatitis (AD) has not been reported. The aims of this study were to assess the efficacy of CLA, black currant seed oil (BSO) or a combination of both, compared to placebo, in dogs with AD and to evaluate any changes in fatty acid metabolism with these treatments. Twenty-four dogs with AD were randomly allocated to four groups, and were treated orally each day for two months with either 1 mL/10 kg CLA (80% purity), 1 mL/10 kg pure BSO, 1 mL/10 kg CLA+1 mL/10 kg BSO, or 1 mL/10 kg sugar syrup (placebo). Serum was obtained on days 0, 30 and 60 for analysis of CLA metabolites, linoleic acid (LA), gamma-linolenic acid (GLA), dihomo-gamma-linolenic acid (DGLA) and arachidonic acid (AA). At the same time point, the owners were asked to assess pruritus and the veterinarians evaluated any skin lesions present. Although the best clinical results occurred with BSO treatment alone, improvement of clinical signs and pruritus was not significant with any of the treatments. Serum levels of GLA and DGLA significantly increased in BSO-treated dogs, but not in the CLA+BSO group. CLA at the dosage used in this study was not efficacious in treating canine AD, whereas BSO may help some dogs with AD, although further studies are necessary before this can be recommended as a treatment.  相似文献   
957.
Peripheral blood samples were collected randomly from 195 horses in various parts of Hungary, and the presence of microfilariae was evaluated by the Knott technique. On the basis of morphological identification 18 of the horses (9.2 per cent) were infected with Setaria equina, and the infection was confirmed in 10 animals by pcr and sequencing. The level of microfilaraemia was between 1 and 1138 larvae in 2 ml of blood. There was no correlation between the time of sampling or the sex of the animals (stallions versus mares) and the prevalence of infection, but the prevalence decreased with age. There was a significant association between the prevalence of microfilaraemia and the presence of still waters; positive samples were collected either in the region of Lake Balaton, the largest lake in the country, or at places with nearby ponds.  相似文献   
958.
Feline upper respiratory tract disease (URTD), mainly caused by feline calicivirus (FCV) and feline herpesvirus, is a major cause of disease outbreaks in feline accommodation such as animal shelters, catteries and multi-cat households. We conducted a longitudinal, yearlong study in five UK feline animal shelters to identify risk factors for the time to diagnosis of URTD. We were especially interested in risk factors that could be identified at the time the cat entered the shelter. Shelter staff recorded data for 1434 cats during 2002–2003. Most of the cats were domestic shorthair cats and were from private households, or were stray or abandoned. Sixty cats without clinical signs of URTD at entry had URTD diagnosed (typically within the first month at the centre). We used two multivariable models: one was a Cox proportional-hazards model, and the other a regression analyses with complementary log–log model.The hazard varied substantially between shelters and was considerably lower for the shelter that had a purpose-built admissions unit with its own isolation facilities. The hazard was greater for purebred cats (HR 4.3–5.0) and for neutered cats (HR 2.0). The hazard was also typically greater if the centre had a greater proportion of cats present with URTD. The analyses suggested that the centre-level risk factors were more important in determining hazard than cat-level risk factors.  相似文献   
959.
Local anaesthetic techniques and diagnostic imaging tools are currently used in conjunction with thorough physical and lameness examinations to diagnose sacroiliac disease (SID) in the horse. The deep and inaccessible location of the sacroiliac joint (SIJ), however, often renders diagnostic imaging modalities, such as radiography, nuclear scintigraphy and ultrasonography, unreliable in identifying sacroiliac problems. The equine clinician therefore often has to rely on positive results of local anaesthetic techniques to confirm a diagnosis of SID. Regional infiltration techniques have been described but result in a diffuse distribution of large volumes of local anaesthetic solution throughout the entire lumbosacroiliac region, which is nonspecific to the SIJ and has the potential to produce false positive results. Several periarticular injection approaches to the SIJ have recently been described. A combination of periarticular SIJ injections with the use of modest amounts of local anaesthetic solution provides increased SIJ specificity, but may lead to false negative results in cases where the pain originates from surrounding soft tissues. This article clarifies terminology related to sacroiliac injections, reviews current injection techniques, highlights the advantages and disadvantages of each approach, and investigates injectate volume considerations.  相似文献   
960.
This study addresses development and validation of a composite multifactorial pain scale (CPS) in an experimental equine model of acute orthopaedic pain. Eighteen horses were allocated to control (sedation with/without epidural analgesia - mixture of morphine, ropivacaine, detomidine and ketamine) and experimental groups: amphotericin-B injection in the tarsocrural joint induced pain and analgesia was either i.v. phenylbutazone administered post-induction of synovitis, or pre-emptive epidural mixture, or a pre-emptive combination of the 2. Inter- and intra-observer reproducibility was good (0.8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