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   5058篇
  免费   359篇
  国内免费   1篇
林业   400篇
农学   234篇
基础科学   44篇
  1169篇
综合类   167篇
农作物   217篇
水产渔业   624篇
畜牧兽医   1991篇
园艺   109篇
植物保护   463篇
  2023年   48篇
  2022年   65篇
  2021年   161篇
  2020年   154篇
  2019年   174篇
  2018年   286篇
  2017年   232篇
  2016年   229篇
  2015年   175篇
  2014年   222篇
  2013年   321篇
  2012年   339篇
  2011年   354篇
  2010年   211篇
  2009年   226篇
  2008年   292篇
  2007年   270篇
  2006年   233篇
  2005年   224篇
  2004年   198篇
  2003年   160篇
  2002年   156篇
  2001年   102篇
  2000年   97篇
  1999年   70篇
  1998年   33篇
  1997年   24篇
  1996年   18篇
  1995年   28篇
  1994年   10篇
  1993年   11篇
  1992年   21篇
  1991年   22篇
  1990年   28篇
  1989年   20篇
  1988年   11篇
  1987年   17篇
  1986年   11篇
  1985年   8篇
  1984年   8篇
  1983年   14篇
  1982年   9篇
  1981年   8篇
  1980年   14篇
  1978年   8篇
  1977年   11篇
  1976年   8篇
  1973年   7篇
  1969年   12篇
  1967年   8篇
排序方式: 共有5418条查询结果,搜索用时 328 毫秒
61.
Findings of hepatic and gallbladder ultrasonography were analyzed in 12 dogs with gallbladder and/or extrahepatic biliary tract obstruction and compared with the results of exploratory laparotomy. Hepatic ultrasonography demonstrated normal liver in 2 dogs and hepatic abnormalities in 10 animals. The following ultrasonographic diagnoses were established compared to surgical findings: gallbladder obstruction caused by bile sludge (correct/incorrect: 1/2, surgical diagnosis: choleliths in one case), gallbladder obstruction caused by neoplasm (0/1, surgical diagnosis: mucocele), gallbladder and extrahepatic biliary tract obstruction due to choleliths (3/3), extrahepatic biliary tract obstruction caused by pancreatic mass (1/1) and small intestinal volvulus (1/1). Bile peritonitis caused by gallbladder rupture (4/4) was correctly diagnosed by ultrasound, aided with ultrasonographically-guided abdominocentesis and peritoneal fluid analysis. Rupture of the gallbladder should be suspected in the presence of a small, echogenic gallbladder or in the absence of the organ together with free abdominal fluid during ultrasonography. Laparotomy was correctly indicated by ultrasonography in all cases. However, the direct cause of obstruction could not be determined in 2 of the 12 dogs by ultrasonography alone.  相似文献   
62.
Pharmacokinetic and clinical effectiveness of liposome-encapsulated N-methylglucamine antimoniate (LMA) was performed in dogs suffering from experimental leishmaniosis. LMA was compared with N-methylglucamine antimoniate (MGA), the same drug in its free form. Sb plasma concentrations for LMA were always higher than those for MGA. Mean residence time (MRT), half-life time (t(1/2)) and clearance (Cl) showed that Sb was eliminated slower after liposome administration. The high volume of distribution (Vd) obtained with LMA suggests that Sb could achieve therapeutic concentrations in parasite-infected tissues. Average plasma concentration at steady state (Css(ave)) shows that Sb body concentrations after LMA treatment (9.8 mg/kg Sb, each 24h) would be effective in Leishmania infantum canine infection. Comparing LMA with MGA in a 1-year follow-up we observed no relapses for LMA and total protein and gammaglobulin concentrations were within normal range, while for MGA both began to rise 3 months after treatment. Use of antimonial liposomal formulations may restore effectiveness to an existing drug and reduce toxicity.  相似文献   
63.
A nested polymerase chain reaction (PCR) assay was developed using primers selected from the genomic DNA of Leishmania infantum and applied to the diagnosis of leishmaniosis in peripheral blood in dogs. Blood of 39 dogs of different breeds, all sampled in Catalonia (Spain), were tested for leishmaniosis by enzyme linked immunosorbent assay (ELISA), western blotting (WB) and peripheral blood mononuclear cell (PBMC) culture and nested PCR. Twenty negative controls (healthy dogs less than 1-year-old that had not been exposed to a sandfly season) were also studied. Nineteen of the 39 dogs studied were positive by ELISA and/or WB, and 18 of these had a positive PBMC nested PCR. PBMC nested PCR was negative in all the remaining animals that were negative by serological examination, including the 20 negative controls. Parasitological examination and nested PCR of bone marrow and lymph node aspirate from the 19 dogs positive by serological examination, were also positive. These results indicate that PBMC nested PCR is a sensitive and specific tool to diagnose leishmaniosis in dogs. The use of PBMC has the advantage over bone marrow and lymph node aspirates in that it is a less invasive sample.  相似文献   
64.
An analysis of the informative content of sequence stretches on the foot-and-mouth disease virus (FMDV) VPI gene was applied to two important viral serotypes: A and O. Several sequence regions were identified to allow the reconstruction of phylogenetic trees equivalent to those derived from the whole VPI gene. The optimal informative regions for sequence windows of 150 to 250 nt were predicted between positions 250 and 550 of the gene. The sequences spanning the 250 nt of the 3' end (positions 400 to 650), extensively used for FMDV phylogenetic analyses, showed a lower informative content. In spite of this, the use of sequences from this region allowed the derivation of phylogenetic trees for type A and type O FMDVs which showed topologies similar to those previously reported for the whole VP1 gene. When the sequences determined for viruses isolated in Argentina, between 1990 and 1993, were included in these analyses, the results obtained revealed features of the circulation of type A and type O viruses in the field, in the months that preceded the eradication of the disease in this country. Type A viruses were closely related to an Argentinean vaccine strain, and defined an independent cluster within this serotype. Among the type O viruses analysed, two groups were distinguished; one was closely related to the South American vaccine strains, while the other was grouped with viruses of the O3 subtype. In addition, a detailed phylogeny for type A FMDV is presented.  相似文献   
65.
The effects of temperature and inoculum density of Fusarium oxysporum f. sp. ciceris race 5 on suppression of Fusarium wilt in chickpea (Cicer arietinum) cv. PV 61 by seed and soil treatments with rhizobacteria isolated from the chickpea rhizosphere were studied in a model system. Disease development over a range of temperatures (20, 25, and 30 degrees C) and inoculum densities (25 to 1,000 chlamydospores per gram of soil) was described by the Gompertz model. The Gompertz relative rate of disease progress and final amount of disease increased exponentially and monomolecularly, respectively, with increasing inoculum densities. Disease development was greater at 25 degrees C compared with 20 and 30 degrees C. At 20 and 30 degrees C, disease development was greater at 250 to 1,000 chlamydospores per gram of soil compared with 25 to 100 chlamydospores per gram of soil. At 25 degrees C, increasing inoculum densities of the pathogen did not influence disease. Nineteen Bacillus, Paenibacillus, Pseudomonas, and Stenotrophomonas spp. out of 23 bacterial isolates tested inhibited F. oxysporum f. sp. ciceris in vitro. Pseudomonas fluorescens RGAF 19 and RG 26, which did not inhibit the pathogen, showed the greatest Fusarium wilt suppression. Disease was suppressed only at 20 or 30 degrees C and at inoculum densities below 250 chlamydospores per gram of soil. Bacterial treatments increased the time to initial symptoms, reduced the Gompertz relative rate of disease progress, and reduced the overall amount of disease developed.  相似文献   
66.
67.
Objective: This review discusses the different analgesic drugs and routes of administration used in large animals for acute pain management. General guidelines and doses are given to assist in choosing techniques that provide effective analgesia. Etiology: Noxious stimuli are perceived, recognized, and localized by specialized sensory systems located at spinal and supraspinal levels. Diagnosis: Localizing the source of the noxious stimulus as well as understanding the behavioral aspects and physiological changes that result from such insult is important to adequately diagnose and treat pain. Pain assessment is far from being definite and objective; not only are there species differences, but also individual variation. In addition, the behavioral and physiological manifestations vary with the acute or chronic nature of pain. Therapy: Pain management should include (1) selecting drugs that better control the type of pain elicited by the insult; (2) selecting techniques of analgesic drug administration that act on pathways or anatomical locations where the nociceptive information is being processed or originating from; (3) combining analgesic drugs that act on different pain pathways; and (4) provide the best possible comfort for the animal. Prognosis: Providing pain relief improves the animal's well being and outcome; however, interpreting and diagnosing pain remains difficult. Continuing research in pain management will contribute to the evaluation of the pathophysiology of pain, pain assessment, and newer analgesic drugs and techniques.  相似文献   
68.
The purpose of this study was to isolate and cultivate a subpopulation of pluripotent stem cells (PSCs) from the peripheral blood of rabbits, which are frequently used in veterinary research as an animal model. Pluripotent stem cells, as described in human beings, are fibroblast-like cells that exhibit a CD34 marker, specific from other hematopoietic stem cells. Commonly used human commercial media has been researched for culturing rabbit PSCs. These findings allow us to contemplate the direct application of this simple and standardized methodology in several areas of study, such as of the pharmacological effect of many drugs on hematopoietic cells, veterinary practice, and even the study of new strategies in cellular therapy for some human diseases.  相似文献   
69.
The survival of two species of plant parasitic nematodes: the root-lesion nematode Pratylenchus brachyurus, and the root-knot nematode Meloidogyne javanica, was evaluated in saturated atmospheres of 12 natural chemical compounds. The infectivity of two isolates of arbuscular mycorrhizal fungi: Glomus mosseae and Glomus intraradices, under identical experimental conditions, was also determined. All the compounds tested exerted a highly significant control against M. javanica and among them, benzaldehyde, salicilaldehyde, borneol, p-anisaldehyde and cinnamaldehyde caused a mortality rate above 50% over P. brachyurus. The infectivity of G. intraradices was inhibited by cinnamaldehyde, salicilaldehyde, thymol, carvacrol, p-anisaldehyde, and benzaldehyde, while only cinnamaldehyde and thymol significantly inhibited mycorrhizal colonization by G. mosseae.  相似文献   
70.
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