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   14319篇
  免费   648篇
  国内免费   1648篇
林业   1616篇
农学   2424篇
基础科学   1189篇
  2278篇
综合类   4291篇
农作物   897篇
水产渔业   478篇
畜牧兽医   1985篇
园艺   514篇
植物保护   943篇
  2024年   42篇
  2023年   159篇
  2022年   404篇
  2021年   538篇
  2020年   549篇
  2019年   505篇
  2018年   379篇
  2017年   500篇
  2016年   516篇
  2015年   661篇
  2014年   606篇
  2013年   721篇
  2012年   848篇
  2011年   921篇
  2010年   859篇
  2009年   792篇
  2008年   745篇
  2007年   812篇
  2006年   728篇
  2005年   704篇
  2004年   345篇
  2003年   421篇
  2002年   488篇
  2001年   463篇
  2000年   383篇
  1999年   417篇
  1998年   317篇
  1997年   284篇
  1996年   218篇
  1995年   215篇
  1994年   216篇
  1993年   179篇
  1992年   168篇
  1991年   116篇
  1990年   95篇
  1989年   108篇
  1988年   83篇
  1987年   40篇
  1986年   19篇
  1985年   15篇
  1984年   11篇
  1983年   4篇
  1982年   5篇
  1981年   3篇
  1980年   6篇
  1979年   2篇
  1966年   1篇
  1965年   2篇
  1964年   1篇
  1956年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
我站是重庆市农业局直属处级行政执行型全额拨款事业单位。现有技术人员43名,其中高级职称13名,中级5名,硕士11名,本科生17名,专科11名,其他4名。实验室现有面积3250m2,拥有细菌鉴定及药敏测试仪、气-质联用仪、高效液相色谱仪、气相色谱仪、电感耦合等离子体原子发射光谱仪(ICP)等199台(套)精密仪器,价值2000余万元。能承担现有国家标准、行业标准和重庆市地方标准规定的所有动物疫病诊断,饲料、兽药、畜产品质量检测检验项目。检测指标达到微量级,有的指标甚至可以检测痕量级。实验室已经全面通过重庆市质量技术监督局计量认证和农业部…  相似文献   
102.
挤压膨化玉米的糊化度与乳猪料   总被引:5,自引:0,他引:5  
玉米是饲料中最重要的能量源,被称为饲料之王,其籽粒成分中含约70%左右的淀粉。因此。提高玉米淀粉利用率是提高畜禽养殖增重效率和饲料效率的关键。由于淀粉粒内存在相当比例抗酸抗酶的晶体结构而不利于动物的消化吸收,必须让晶体结构解体(即糊化)才能被酶充分水解而提高消化率。不同的加工方式得到的淀粉糊化度不一样,能耗也不一样。随着淀粉糊化度的提高,能耗也相应提高,那么究竟什么样的淀粉糊化度可以适宜乳猪料生产的需要呢?  相似文献   
103.
Five commercially available organic Cu products and reagent-grade CuSO4 x 5H2O (Cu Sulf) were evaluated by polarographic analysis and solubility in 0.1 M K2HPO4-KH2PO4 buffer (pH 5), 0.2 M HCl-KCl buffer (pH 2), or deionized water. Fractions from these solubility tests were evaluated by gel filtration chromatography for structural integrity. The organic sources were Cu lysine complex (Cu Lys), Cu amino acid chelate (Cu AA), Cu proteinate A (Cu ProA), Cu proteinate B (Cu ProB), and Cu proteinate C (Cu ProC). Separation of peaks in the chromatograms for the soluble Cu fraction from deionized water indicated that 77, 31, 69, 94, and 16% of the Cu remained chelated for the above sources, respectively. Two experiments were conducted to estimate the relative bioavailability of Cu from the organic Cu supplements for chicks when added at high dietary concentrations to practical corn-soybean meal diets. Liver Cu concentration increased (P < 0.0001) as dietary Cu increased in both experiments. When Cu Sulf was assigned a value of 100% as the standard, linear regression slope ratios of log10 liver Cu concentration regressed on added dietary Cu concentration gave estimated relative bioavailability values of 124 +/- 5.1, 122 +/- 5.3, and 111 +/- 6.0 for Cu Lys, Cu AA, and Cu ProC, respectively, in Exp. 1. The bioavailability estimates for Cu Lys and Cu AA were greater (P < 0.05) than that for Cu Sulf. Values in Exp. 2 were 111 +/- 7.6, 109 +/- 8.4, and 105 +/- 7.5 for Cu Lys, Cu ProA, and Cu ProB, respectively, and all sources were similar in value for chicks. Solubility of Cu in pH 2 buffer provided the best prediction of bioavailability (r2 = 0.924). Other indicators of chelation integrity and solubility had little value as predictors of bioavailability (r2 < or = 0.445).  相似文献   
104.
为了解当前河南省病死动物无害化处理现状,通过问卷调查和实地调研相结合的方式,初步了解当前河南省病死动物无害化处理现状。分析发现在病死动物无害化处理监管机制中存在政府监管力度不足、追溯体系不健全等问题,提出了加大财政投入、制定配套法规、推行政策性养殖等建议。  相似文献   
105.
中国犬业经济,目前犹如一把葱花   总被引:1,自引:0,他引:1  
中国犬业经济已显山露水 随着中国经济的稳步发展和居民生活水平的提高,全国各地的养犬数量与日俱升。有报载,北京的有证犬至少有13万余头,总养犬数在100余万头,上海、广州、深圳的养犬量也同样惊人。与此相匹配,国内犬展犬赛月月都有,有的犬售价在几万、几十万、甚至上百万,犬饲料、犬用品用具、犬医疗保健和宠物店更犹如雨后春笋。以犬饲料为例,目前已有二十余种国内外产品投放市场上,  相似文献   
106.
107.
The objective was to evaluate the effect of dietary coconut oil on methane (CH(4)) emissions and the microbial community in Tibetan sheep. Twelve animals were assigned to receive either a control diet (oaten hay) or a mixture diet containing concentrate (maize meal), in which coconut oil was supplemented at 12?g/day or not for a period of 4?weeks. CH(4) emissions were measured by using the 'tunnel' technique, and microbial communities were examined using quantitative real-time PCR. Daily CH(4) production for the control and forage-to-concentrate ratio of 6:4 was 17.8 and 15.3?g, respectively. Coconut oil was particularly effective at reducing CH(4) emissions from Tibetan sheep. The inclusion of coconut oil for the control decreased CH(4) production (in grams per day) by 61.2%. In addition, there was a positive correlation between the number of methanogens and the daily CH(4) production (R?=?0.95, P?相似文献   
108.
The endometrium of sheep consists of plenty of raised aglandular areas called caruncular (C), and intensely glandular intercaruncular areas (IC). In order to better understand the endometrium involved mechanisms of implantation, we used LC-MS/MS technique to profile the proteome of ovine endometrial C areas and IC areas separately during the peri-implantation period, and then compared the proteomic profiles between these two areas. We successfully detected 1740 and 1813 proteins in C areas and IC areas respectively. By comparing the proteome of these two areas, we found 170 differentially expressed proteins (DEPs) (P < 0.05), functional bioinformatics analysis showed these DEPs were mainly involved in growth and remodeling of endometrial tissue, cell adhesion and protein transport, and so on. Our study, for the first time, provided a proteomic reference for elucidating the differences between C and IC areas, as an integrated function unit respectively, during the peri-implantation period. The results could help us to better understand the implantation in the ewes. In addition, we established a relatively detailed protein database of ovine endometrium, which provide a unique reference for further studies.  相似文献   
109.
通过对俄罗斯奶业发展的资源环境分析,梳理了俄罗斯奶牛养殖、生鲜乳销售、乳制品加工与贸易的历史发展脉络,研判其未来发展前景。结果认为,俄罗斯奶业在国家政策扶持下,生产结构不断调整优化,未来发展空间广阔,特别是远东地区将会是俄罗斯奶业发展新的着力点。进一步对中俄两国在奶业生产领域的合作情况进行了态势分析(SWOT分析),从总体上看,中俄两国奶业合作的机遇与挑战并存,但基于两国在奶业生产合作上的共同利益,及双方政府政策有力支持的基础上,中俄两国继续深化奶业务实合作,实现互利共赢的前景广阔。  相似文献   
110.
Spermatozoa are highly specialized cells, and energy metabolism plays an important role in modulating sperm viability and function. Rosiglitazone is an antidiabetic drug in the thiazolidinedione class that regulates metabolic flexibility and glucose uptake in various cell types, but its effects on boar sperm metabolism are unknown. In this study, we investigated the potential effect of rosiglitazone against time‐dependent deterioration of boar spermatozoa during liquid preservation at 17°C. Freshly ejaculated semen was diluted with Beltsville Thawing Solution (BTS) containing different concentrations of rosiglitazone, and the motility, membrane and acrosome integrity of sperm were detected. Besides, we measured glucose uptake capacity, l ‐lactate production level, mitochondrial membrane potential, adenosine triphosphate (ATP) content and mitochondrial reactive oxygen species (mROS) production of sperm after boar semen had been incubated with or without rosiglitazone, iodoacetate (glycolysis inhibitor) and rotenone (electron transport chain inhibitor) for 5 days. The addition of rosiglitazone significantly enhanced sperm quality and had a strong protective effect on the sperm membrane and acrosome integrity during storage. BTS containing 50 μM rosiglitazone maintained the total motility of liquid‐preserved sperm above 60% for 7 days. Rosiglitazone improved sperm quality by regulating energy metabolism manner of preserved sperm, protected the sperm mitochondrial membrane potential, enhanced sperm ATP production and in the meanwhile reduced mROS through enhancing glycolysis but not oxidative phosphorylation. The data suggested the practical feasibility of using rosiglitazone for improving boar spermatozoa quality during semen preservation.  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