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   1083篇
  免费   83篇
林业   81篇
农学   28篇
  195篇
综合类   113篇
农作物   42篇
水产渔业   74篇
畜牧兽医   540篇
园艺   33篇
植物保护   60篇
  2024年   2篇
  2023年   11篇
  2022年   7篇
  2021年   23篇
  2020年   27篇
  2019年   36篇
  2018年   32篇
  2017年   36篇
  2016年   37篇
  2015年   34篇
  2014年   45篇
  2013年   64篇
  2012年   78篇
  2011年   107篇
  2010年   41篇
  2009年   36篇
  2008年   90篇
  2007年   75篇
  2006年   56篇
  2005年   55篇
  2004年   61篇
  2003年   53篇
  2002年   60篇
  2001年   2篇
  2000年   11篇
  1999年   6篇
  1998年   11篇
  1997年   6篇
  1996年   4篇
  1995年   5篇
  1994年   5篇
  1993年   4篇
  1992年   4篇
  1991年   7篇
  1990年   7篇
  1989年   5篇
  1988年   2篇
  1985年   3篇
  1984年   2篇
  1983年   2篇
  1979年   3篇
  1978年   3篇
  1977年   3篇
  1976年   1篇
  1975年   1篇
  1973年   2篇
  1966年   1篇
排序方式: 共有1166条查询结果,搜索用时 15 毫秒
101.
This report documents congenital stationary night blindness (CSNB) in two non-Appaloosa horse breeds (Thoroughbred and Paso Fino). History of vision impairment since birth, normal ocular structures on ophthalmic examination, and electroretinographic findings were consistent with CSNB. In one horse (Thoroughbred), a 9-year follow-up was carried out. In the Paso Fino, severe vision impairment from birth to approximately 1 year of age in both dim and bright light situations led to humane euthanasia and histopathologic confirmation of the disorder.  相似文献   
102.
OBJECTIVE: To estimate West Nile virus (WNV) infection rates, assess environmental variables that correlated with seropositivity in dogs and cats, and assess whether pets should be considered as possible sentinels for WNV and therefore of potential human exposure. DESIGN: Cross-sectional serosurvey. ANIMALS: 442 dogs and 138 cats. PROCEDURE: Serum samples were screened for seropositivity against WNV by use of the plaque reduction neutralization test. RESULTS: 116 (26%) dogs and 13 (9%) cats yielded positive results. The odds of seropositivity against WNV for outdoor-only family dogs were almost 19 times as great as those for indoor-only family dogs and almost twice as great for stray dogs as for family dogs. Family dogs not receiving heartworm medication were 2.5 times as likely to yield positive results for antibodies against WNV as family dogs receiving heartworm medication. CONCLUSIONS AND CLINICAL RELEVANCE: Seropositivity was greater for outdoor family dogs than for indoor family dogs. Further investigation of the potential use of stray dogs as sentinel indicators for WNV infection and the potential risk of human exposure is warranted.  相似文献   
103.
104.
Two-dimensional electrophoresis was used to investigate sarcoplasmic protein expression in pig Semimembranosus muscles sampled 20 min after slaughter. Two groups (light and dark) of 12 animals were selected from 1000 pigs, based on meat L values measured 36 h postmortem. Twenty-two proteins or fragments (p < 0.05) were differentially expressed. Muscles leading to darker meat had a more oxidative metabolism, indicated by more abundant mitochondrial enzymes of the respiratory chain, hemoglobin, and chaperone or regulator proteins (HSP27, alphaB-crystallin, and glucose-regulated protein 58 kDa). Conversely, enzymes of glycolysis were overexpressed in the lighter group. Such samples were also characterized by higher levels of glutathione S-transferase omega, which can activate the RyR calcium channels, and higher levels of cyclophilin D. This protein pattern is likely to have severe implications on postmortem metabolism, namely, acceleration of ATP depletion and pH fall and subsequent enhanced protein denaturation, well-known to induce discoloration.  相似文献   
105.
106.
Most emerging infectious diseases in humans originate from animal reservoirs; to contain and eradicate these diseases we need to understand how and why some pathogens become capable of crossing host species barriers. Influenza virus illustrates the interaction of factors that limit the transmission and subsequent establishment of an infection in a novel host species. Influenza species barriers can be categorized into virus-host interactions occurring within individuals and host-host interactions, either within or between species, that affect transmission between individuals. Viral evolution can help surmount species barriers, principally by affecting virus-host interactions; however, evolving the capability for sustained transmission in a new host species represents a major adaptive challenge because the number of mutations required is often large.  相似文献   
107.
A strong, global commitment to expanded prevention programs targeted at sexual transmission and transmission among injecting drug users, started now, could avert 28 million new HIV infections between 2005 and 2015. This figure is more than half of the new infections that might otherwise occur during that period in 125 low- and middle-income countries. Although preventing these new infections would require investing about U.S.$122 billion over this period, it would reduce future needs for treatment and care. Our analysis suggests that it will cost about U.S.$3900 to prevent each new infection, but that this will produce a savings of U.S.$4700 in forgone treatment and care costs. Thus, greater spending on prevention now would not only prevent more than half the new infections that would occur from 2005 to 2015 but would actually produce a net financial saving as future costs for treatment and care are averted.  相似文献   
108.
Solutions obtained by heating carrot roots in water (stocks) are widely used in the food industry, but little information is available regarding the metabolites (intermediates and products of metabolism) found in the stock. The effect of treatment temperature and duration on the sugar composition of stocks was investigated directly by quantitative (1)H NMR spectroscopy, to understand the extraction mechanism when processing at 100 degrees C. Stocks prepared at three different temperatures (50, 75, and 100 degrees C) were investigated for up to 36 h. Three sugars (sucrose, glucose, and fructose) were detected and quantified. The concentrations of these three sugars reached a maximum after 9 h when the temperature of treatment was 50 or 75 degrees C. At 100 degrees C, the sucrose concentration reached a maximum after 3 h, whereas the concentration of glucose and fructose was still increasing at that time. Comparison of the kinetic composition of these carrot stocks with that of model sugar solutions leads to the proposal that the changes in stock composition result from sugar diffusion, sucrose hydrolysis, and hydroxymethylfurfural (HMF) formation.  相似文献   
109.
OBJECTIVE: To compare upper airway mechanics, arterial blood gases, and tracheal contamination in horses with induced left laryngeal hemiplegia (recurrent laryngeal neuropathy [RLN]) treated by laryngoplasty/vocal cordectomy (LPVC) or modified partial arytenoidectomy (MPA). STUDY DESIGN: Repeated measures under the following conditions: Control, RLN, LPVC, and MPA. ANIMALS: Six horses. METHODS: Two trials were conducted under all conditions at 80% and 100% of maximal heart rate (HR(max)). In Trial 1, arterial blood gases, tracheal and pharyngeal pressures, and laryngeal videoendoscopy were recorded. In Trial 2, upper airway pressure and airflow were determined. Tracheobronchial aspirates were performed after exercise to quantify airway contamination. RESULTS: Compared with control, RLN significantly increased inspiratory impedance and worsened exercise-induced hypoxemia. At 80% HR(max), LPVC restored most variables to control values. At 100% HR(max), LPVC improved all variables, but did not restore minute volume, arterial pH, and PaCO(2). At 80% HR(max), MPA restored all variables except bicarbonate to control values. At 100% HR(max), MPA improved all variables, but did not statistically restore minute ventilation or bicarbonate level. Only minor differences were noted between LPVC and MPA. Both resulted in equivalent tracheal contamination. CONCLUSIONS: Airway mechanics and arterial blood gas values were not restored to normal after either LPVC or MPA in horses exercising at HR(max). This does not affect ventilation at sub-maximal exercise, but has clinical implications at HR(max). Both procedures diminish normal laryngeal protective mechanisms. CLINICAL RELEVANCE: At sub-maximal exercise intensities both LPVC and MPA restore airway ventilation to normal. At maximal exercise the superiority of LPVC over MPA is slight.  相似文献   
110.
In this study, canine monocyte-derived dendritic cells (cMo-DC) were produced in presence of canine GM-CSF (cGM-CSF) and canine IL-4 (cIL-4), and they were characterized by their dendritic morphology, MLR functionality and phenotype. We noticed that cMo-DC were labelled with three anti-human CD86 (FUN-1, BU63 and IT2.2 clones), whereas resting and activated lymphocytes or monocytes were not stained. CD86 expression was induced by cIL-4 and was up-regulated during the differentiation of the cMo-DC, with a maximum at day 7. Furthermore, cMo-DC were very potent even in low numbers as stimulator cells in allogeneic MLR, and BU63 mAb was able to completely block the cMo-DC-induced proliferation in MLR. We also observed that cMo-DC highly expressed MHC Class II and CD32, but we failed to determine their maturation state since the lack of commercially available canine markers. Moreover, cMo-DC contained cytoplasmic periodic microstructures, potentially new ultrastructural markers of canine DC recently described. In conclusion, this work demonstrates that the CD86 costimulatory marker is now usable for a better characterization of in vitro canine DC.  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