全文获取类型
收费全文 | 776篇 |
免费 | 55篇 |
国内免费 | 14篇 |
专业分类
林业 | 28篇 |
农学 | 24篇 |
基础科学 | 2篇 |
151篇 | |
综合类 | 187篇 |
农作物 | 22篇 |
水产渔业 | 33篇 |
畜牧兽医 | 357篇 |
园艺 | 16篇 |
植物保护 | 25篇 |
出版年
2023年 | 13篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 8篇 |
2019年 | 13篇 |
2018年 | 11篇 |
2017年 | 20篇 |
2016年 | 26篇 |
2015年 | 22篇 |
2014年 | 28篇 |
2013年 | 48篇 |
2012年 | 37篇 |
2011年 | 45篇 |
2010年 | 33篇 |
2009年 | 21篇 |
2008年 | 34篇 |
2007年 | 30篇 |
2006年 | 25篇 |
2005年 | 25篇 |
2004年 | 30篇 |
2003年 | 40篇 |
2002年 | 20篇 |
2001年 | 28篇 |
2000年 | 14篇 |
1999年 | 21篇 |
1998年 | 17篇 |
1997年 | 9篇 |
1996年 | 16篇 |
1995年 | 5篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 14篇 |
1991年 | 10篇 |
1990年 | 11篇 |
1989年 | 13篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1983年 | 5篇 |
1981年 | 4篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1967年 | 5篇 |
1954年 | 3篇 |
排序方式: 共有845条查询结果,搜索用时 15 毫秒
41.
Thomas H. Christensen 《Water, air, and soil pollution》1985,25(3):265-274
Field and laboratory studies were conducted to assess the survival of B.t. var. kurstaki in waters. B.t. var. kurstaki was recovered from rivers and public water distribution systems following aerial application of a commercial B.t. formulation (Thuricide 16B). Laboratory studies indicate that B.t. var. kurstaki can survive for relatively long periods of time in fresh water and the marine environment at 20 °C. The amount of residual Cl normally applied to a standard water purification system does not appear to be sufficient to destroy B.t. var. kurstaki. A total Cl residual of at least 1.5 mg L?1 and 60 min contact time was needed to inactivate 99% of the B. t. var. kurstaki population in tap water at pH 7.2 and 20 °C. 相似文献
42.
Møller JK Parolari G Gabba L Christensen J Skibsted LH 《Journal of agricultural and food chemistry》2003,51(5):1224-1230
Parma hams at various processing stages were investigated by surface autofluorescence spectroscopy. Fluorescence "landscapes" of raw meat and salted (3 months), matured (11 and 12 months), and aged (15 and 18 months) Parma hams were obtained, and a three-dimensional data array (sample x emission x excitation) was used to develop a PARAFAC model including five components, which all exhibited characteristics of pure fluorophores regarding both excitation and emission spectra. The relative amount of each component related strongly to the processing stage, and sample age showed good correlation to fluorescence data (R = 0.98), with a relative error of prediction of approximately 1 month. Fluorescence measurements from samples of either semimembranosus or biceps femoris were used to predict chemical or sensory reference data, yielding good correlation for biceps femoris data, thereby enabling moisture content, sensory and instrumental color, and proteolysis value to be fairly well predicted. Overall, surface autofluorescence of Parma hams proved to hold relevant information, relating to major chemical/physical changes during processing. It is concluded that fluorescence spectroscopy has potential as an innovative method of quality control in dry-cured ham. 相似文献
43.
44.
45.
The non-steady-state fluxes of aromatic hydrocarbons from coal tar contaminated soil, placed below a 5 cm deep layer of uncontaminated soil, were measured in the laboratory over a period of 53 days. The contaminated soil originated from a former gasworks site and contained concentrations of 11 selected aromatic hydrocarbons between 50 to 840 µg/cm3. Where the microbial activity was inhibited, the fluxes stabilized on a semi-steady-state level for the monocyclic aromatic hydrocarbons, naphthalene and 1-methylnaphthalene after a period of 10–20 days. Fluxes of acenaphthene and fluorene were only measurable in an experiment that utilized a cover soil with a low organic content. The fluxes were predicted by a numerical model assuming that the compounds acted independently of each other and that local equilibrium between the air, water, and sorbed phases existed. The model overestimated the fluxes for all the detected aromatic hydrocarbons by a factor of 1.3 to 12. When the cover soil was adapted to degrade naphthalene, the fluxes of naphthalene and 1-methylnaphthalene approached the detection limit after 5 to 8 days. Thereafter the fluxes of these two compounds were less than predicted by the model employing half-life values of 0.5 and 1 day for naphthalene and 1-methylnaphthalene respectively. 相似文献
46.
47.
森林生物量测定一直是森林生态系统研究的主要内容,也是地区森林生态系统长期监测所必需的基础性研究。以浙江天童国家森林公园常绿阔叶林为研究对象,于2003年10月份采用收获法(草本层、灌木层)和标准木法(乔木层)相结合的方法,测定了以木荷Schimasuperba,米槠Castanopsis carlesii为优势种的群落地上部分生物量。结果表明:群落地上部分总生物量为(141.0770±17.4298)t.hm-2(平均值±标准差,n=3),其中接近90%集中于乔木层,其他层生物量分配较少。群落及其各层生物量种间分配差异较大,以优势树种木荷和米槠生物量为主,其生物量主要由树干组成,器官分配大小顺序为干>枝>叶。群落萌枝生物量主要集中在灌木层,50%以上由米槠萌枝生物量构成。群落生物量及其分配状况基本体现了以木荷和米槠为优势种的该群落结构特征及常绿阔叶林群落生物量分配特征。表5参15 相似文献
48.
上海乡土树种及其在城市绿化建设中的应用 总被引:34,自引:1,他引:34
随着生态城市被列为上海市的建设发展目标,城市绿化建设被赋予了新的目标和内涵,生态林将逐渐成为城市绿化的主体,作为生态林建设基础的乡土树种也将得到更为广泛的应用.通过实地调查和资料调查,统计分析了上海市的乡土树种,共42科89属128种(含变种),可以分为常绿阔叶乔木、常绿阔叶灌木、半常绿阔叶灌木、落叶阔叶乔木、落叶阔叶小乔木和落叶阔叶灌木等6个类型.分析了乡土树种在上海绿化建设中的意义和应用现状,并对其应用进行了展望.表1参21 相似文献
49.
50.
披针叶黄华生物碱成分研究 总被引:4,自引:0,他引:4
采用 GC- MS联用分析技术从披针叶黄华总生物碱中分离鉴定出 12个喹喏里西啶生物碱 ,即无叶豆碱 ,N-甲基金雀花碱 ,金雀花碱 ,白羽扇豆碱 ,黄华碱 ,臭豆碱 ,N-甲醛基金雀花碱 ,Dodecahydro- 7,14 -methanodipyrido[1,2 - a:1′,2′- E][1.5 ]diazocine,Pyridine1- acetyl- 1,2 ,3,4 - tetrahydro- 5 - (2 - piperdinyl) ,7,14 -Methano- 2 H,6 H- dipyrido[1,2 - a:1′,2′- e][1,5 ]diaz,1,1- Dim ethyl- 3- (2 - nitrophenyl) ,7,14 - Methano- 4 H,6 H-dipyrido[1,2 - a:1′,2′- e][1,5 ]diaz。后 5种化合物为首次从该植物中鉴定 相似文献