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   5508篇
  免费   262篇
  国内免费   4篇
林业   423篇
农学   183篇
基础科学   35篇
  1103篇
综合类   877篇
农作物   232篇
水产渔业   344篇
畜牧兽医   2002篇
园艺   176篇
植物保护   399篇
  2023年   33篇
  2022年   54篇
  2021年   84篇
  2020年   135篇
  2019年   126篇
  2018年   135篇
  2017年   121篇
  2016年   130篇
  2015年   110篇
  2014年   131篇
  2013年   259篇
  2012年   303篇
  2011年   382篇
  2010年   220篇
  2009年   168篇
  2008年   310篇
  2007年   317篇
  2006年   291篇
  2005年   289篇
  2004年   264篇
  2003年   271篇
  2002年   256篇
  2001年   64篇
  2000年   71篇
  1999年   82篇
  1998年   56篇
  1997年   53篇
  1996年   54篇
  1995年   39篇
  1994年   47篇
  1993年   49篇
  1992年   39篇
  1991年   46篇
  1990年   46篇
  1989年   42篇
  1988年   38篇
  1987年   40篇
  1986年   54篇
  1985年   34篇
  1984年   43篇
  1983年   35篇
  1982年   36篇
  1981年   27篇
  1980年   20篇
  1979年   23篇
  1978年   27篇
  1977年   26篇
  1975年   20篇
  1973年   24篇
  1972年   20篇
排序方式: 共有5774条查询结果,搜索用时 31 毫秒
31.
32.
33.
34.
35.
36.
BackgroundFor the treatment of diabetes mellitus (DM) in dogs, novel insulins with decreased injection frequency while maintaining safety and efficacy are desirable. Insulin fused with immunoglobulin‐fragment‐crystallizable (Fc) has an ultra‐long plasma half‐life because it recycles through cells, protected from proteolysis.HypothesisGlycemic control can be achieved in diabetic dogs with a recombinant fusion protein of a synthetic insulin and canine Fc (AKS‐218d) administered subcutaneously once‐weekly.AnimalsFive client‐owned dogs with naturally occurring DM.MethodsProspective clinical trial in dogs with DM that were recruited from the UC Davis Veterinary Teaching Hospital and local veterinary clinics. Dogs previously controlled using intermediate‐acting insulin q12h were transitioned to once‐weekly injections of a preliminary construct identified as AKS‐218d. The dose of AKS‐218d was titrated weekly for 8 weeks based on clinical response and continuous interstitial glucose monitoring. Clinical signs, body weight, serum fructosamine concentrations, and mean interstitial glucose concentrations (IG) over the preceding week were compared between baseline (before AKS‐218d) and during the last week of treatment. Data were compared using nonparametric paired tests.ResultsOnce‐weekly AKS‐218d, compared to baseline twice‐daily insulin therapy, resulted in no significant changes in clinical signs, median (range) body weight (+0.4 kg [−0.5‐1.1]; P = .6), fructosamine concentration (−75 mmol/L [−215 to +126]; P = .4), or mean IG (+81 mg/dL [−282 to +144]; P = .8). No adverse reactions were reported.ConclusionControl of clinical signs, body weight, and maintenance of glycemia was achieved with this once‐weekly novel insulin construct in 4 of 5 dogs.  相似文献   
37.
We report the observation of local structural dipoles that emerge from an undistorted ground state on warming, in contrast to conventional structural phase transitions in which distortions emerge on cooling. Using experimental and theoretical probes of the local structure, we demonstrate this behavior in binary lead chalcogenides, which were believed to adopt the ideal, undistorted rock-salt structure at all temperatures. The behavior is consistent with a simple thermodynamic model in which the emerging dipoles are stabilized in the disordered state at high temperature due to the extra configurational entropy despite the fact that the undistorted structure has lower internal energy. Our findings shed light on the anomalous electronic and thermoelectric properties of the lead chalcogenides. Similar searches may show that the phenomenon is more widespread.  相似文献   
38.
We evaluated the role of flatfishes in the organization and structure of the eastern Bering Sea ecosystem using the Ecopath/Ecosim approach. As basic input data for the Ecopath/Ecosim model, we used estimates of biomass from bottom trawl surveys and age-structured population models, production/biomass (P/B) ratio, consumption/biomass (Q/B) ratio, diet composition (DC), and fisheries harvests for each component of species or species groups. We estimated the trophic level of each component, niche overlaps among flatfishes, and the impacts of competition and predation on flatfish species in the eastern Bering Sea ecosystem. Based on those estimates, we developed the tropho-dynamic structure of the ecosystem, and the model was used to simulate ecological effects of fishery exploitation patterns. No single flatfish species appeared to have a profound and uniquely important role in the organization and structure of the ecosystem. Instead, the most important component among the guild of flatfish species appeared to be yellowfin sole Pleuronectes asper, which had greater biomass than other flatfish and a relatively diverse diet among the small flatfish species. Pacific halibut Hippoglossus stenolepis, Greenland turbot Reinhardtius hippoglossoides, and arrowtooth flounder Atheresthes stomias were important keystone predators in the eastern Bering Sea ecosystem together with some groups of marine mammals and sea birds. Intra flatfish complex cannibalism was not observed, however, substantial diet overlaps were common in the flatfish guild system.  相似文献   
39.
Rice with panicle-blast resistance is needed for stable rice production. Although we have previously demonstrated that OsGF14b underlies a quantitative trait lo...  相似文献   
40.
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