全文获取类型
收费全文 | 6125篇 |
免费 | 299篇 |
国内免费 | 614篇 |
专业分类
林业 | 628篇 |
农学 | 814篇 |
基础科学 | 487篇 |
969篇 | |
综合类 | 1862篇 |
农作物 | 308篇 |
水产渔业 | 251篇 |
畜牧兽医 | 1128篇 |
园艺 | 190篇 |
植物保护 | 401篇 |
出版年
2024年 | 23篇 |
2023年 | 79篇 |
2022年 | 189篇 |
2021年 | 267篇 |
2020年 | 202篇 |
2019年 | 251篇 |
2018年 | 179篇 |
2017年 | 208篇 |
2016年 | 204篇 |
2015年 | 284篇 |
2014年 | 281篇 |
2013年 | 333篇 |
2012年 | 380篇 |
2011年 | 432篇 |
2010年 | 430篇 |
2009年 | 370篇 |
2008年 | 320篇 |
2007年 | 317篇 |
2006年 | 360篇 |
2005年 | 272篇 |
2004年 | 131篇 |
2003年 | 129篇 |
2002年 | 121篇 |
2001年 | 141篇 |
2000年 | 114篇 |
1999年 | 140篇 |
1998年 | 103篇 |
1997年 | 116篇 |
1996年 | 114篇 |
1995年 | 104篇 |
1994年 | 88篇 |
1993年 | 71篇 |
1992年 | 63篇 |
1991年 | 49篇 |
1990年 | 50篇 |
1989年 | 43篇 |
1988年 | 18篇 |
1987年 | 19篇 |
1986年 | 11篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1965年 | 1篇 |
1964年 | 2篇 |
1948年 | 1篇 |
1947年 | 1篇 |
排序方式: 共有7038条查询结果,搜索用时 11 毫秒
991.
992.
Fa-Wen Yin Yan-Fei Liu Qi Zhao Zhong-Yuan Liu Liang Song 《Journal Of Aquatic Food Product Technology》2018,27(3):292-304
Krill oils (KOs) were extracted from Antarctic krill using ethanol, hexane, or their mixture (1:2, v/v) with yields of 21.32%, 8.50%, and 18.75%, respectively. The total nitrogen content of the aforementioned oils was 2.76%, 1.06%, and 1.87%, respectively, indicating the presence of lipoprotein. All KOs contained a high proportion of phospholipid (PL) (30.20–64.82% of total lipids) and polyunsaturated fatty acids (PUFA) (30.00–34.94% of total FAs). Among PL, phosphatidylcholine was dominant (89.81–90.60 mol %). In contrast, KO extracted with the mixed solvent had the highest amount of glycerophosphocholine species containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). 相似文献
993.
Unmodified polyamide 6 commonly dyed with acid dyes, and has no flame-retarded properties. So they are flammable and can be easily stained by foods or drinks that contain acid dyes. However, the acid groups react with amino groups that existed at the end of PA6 chain while using cationic dyes. Thus, the acid dyes can be washed immediately. In this study, the flame retardant and cationic dyeable polyamide 6 (FRCD-PA6) modified with 5-sulfoisophthalic acid sodium (5-SSIPA) and melamine cyanurate (MCA) was successfully prepared by the two-step-melt polymerization method. Firstly, cationic dyeable polyamide 6 (CD-PA6) was prepared with sodium salt from 5-sulfoisphthalic acid. Secondly, melamine cyanurate, as an efficient flame retardant, was blended into the reaction. The chemical and crystalline structures of FRCDPA6 were characterized by the Fourier transform infrared spectroscopy (FT-IR) and wide angle X-ray diffraction (XRD). Their thermal properties were tested by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and morphology was analyzed by SEM, respectively. It had been measured to prove the dispersion of 5-SSIPA and MCA on polyamide 6 matrix. Incorporating with 5-SSIPA created more amorphous regions and rose up the dyeing rate easily, with a highest dyeing rate for about 96.79 %. The effect of varying MCA content on the composites showed more flame retardant and made better heat-resistance. Moreover, with the appropriate addition of MCA content, the limit oxygen index (LOI) reached up to 27, less smoking, no more black smoke, droplet phenomenon was slightly, and flame resistance had greatly improved. Because of the good synergy between 5-SSIPA and MCA, a kind of novel modified polyamide 6 which own both cationic dyeable and efficient flame retardant properties was born. 相似文献
994.
水库移民遗留问题处理对移民生活的影响——基于岩滩水电站移民安置区的模糊分析 总被引:1,自引:1,他引:0
水库移民遗留问题处理,改善了移民的生活条件,移民安置区的社会经济发展取得了明显的成效。本研究运用模糊数学的方法,对遗留问题处理之后的岩滩水电站水库安置区移民生活进行了模糊分析。研究结果表明遗留问题的处理对于移民生活水平改善产生了积极影响,大化、东兰、巴马3个县移民生活水平有了不同程度的提高。对于在遗留问题处理过程中产生的问题,提出了加快项目实施、加强移民管理机构能力建设、移民异地再安置等建议。 相似文献
995.
"Strong column with weak beam","strong beam with weak column" and"column & beam with equal strength"can be existed in one-storey prestressed concrete frames and the top storey of mult-storey prestressed concrete frames.Through the test of four prestressed concrete frames under vertical load,three kinds of prestressed concrete frames performances are studied,such as ultimate load,deflection,displacement ductility,redistribution of internal force.When the relative height of equivalent compression zone is smaller enough,the test proves that three kinds of prestressed concrete frames can realize full redistribution of internal force and have better displacement ductility,the width of cracks and deflections can satisfy the rules of code for design of concrete structures. 相似文献
996.
997.
对流域内植被恢复更新方法及资源利用途径进行了进行了详细阐述,对林业的可持续发展和资源保护具有一定的借鉴和指导意义。 相似文献
998.
Studies on isolated microspore embryoid induction of <Emphasis Type="Italic">C. annuum</Emphasis> L.
Ting Yin Song Tian Shuangxia Luo Xueping Chen Yanhua Wang Shuxing Shen 《Frontiers of Agriculture in China》2010,4(4):438-442
A system to improve isolated microspore embryoid induction rate of pepper (Capsicum annuum L.) was studied in this paper. The results showed that low-temperature pretreatment, growth regulators combinations, activated
carbon concentrations, and preculture temperatures were critical factors affecting embryoid formation of isolated pepper microspores
in vitro. One day after pretreatment of the buds at 4°C, the anthers that differentiated and developed into embryos were cultured
in double-layer medium system for one week at 7°C and then went on culturing at 28°C in darkness. All the seven genotypes
of the tested pepper responded to this protocol. The embryoid induction rate of the best genotype increased from 81.11% to
147.22%. This protocol can be used as a potential tool for producing doubled haploid plants for pepper breeding. 相似文献
999.
2007年3月我园饲养的孟加拉虎、非洲狮、金钱豹发生以采食困难、流涎、口腔溃疡为特征的传染病,历程1个多月,经过以抗继发感染、抗病毒、维持电解质和酸碱平衡及对症治疗为原则的积极抢救治疗,全部痊愈。 相似文献
1000.
两种不同药性中药注射液对内毒素性肾衰的防治作用 总被引:1,自引:0,他引:1
摘要:以家兔为试验动物,研究复方金银花注射液和茵陈五苓注射液对内毒素所致急性肾功能衰竭的防治作用。将32只雄性健康成年家兔随机分为阴性对照组、模型组、复方金银花防治组和茵陈五苓防治组,每组各8只。模型组和各防治组家兔一次性静脉注射大肠杆菌O111B4内毒素生理盐水溶液,剂量为100μg/kg。两防治组家兔注射等剂量内毒素24h后静脉注射剂量为100μg/kg的中药注射液,阴性对照组静脉注射等量生理盐水。注射内毒素(或生理盐水)1h后开始通过膀胱瘘管收集尿液,每1h收集一次,共收集6h。末次收集尿液后心脏采血。结果表明,模型组家兔发生急性肾功能衰竭,其各项肾功能指标均与阴性对照组有显著或极显著差异(P<0.05,P<0.01)。与模型组比较,复方金银花组家兔的尿量以及肌酐、尿素氮和尿钠排出量显著或极显著增加(P<0.05,P<0.01),肾衰指数和钠排泄分数显著降低(P<0.05),内生性肌酐清除率、尿渗透压和尿血渗比及渗透物质清除率显著或极显著升高(P<0.05,P<0.01),游离水清除率极显著降低(P<0.01)。结果表明,复方金银花注射液对内毒素性肾衰具有防治作用。茵陈五苓组家兔的尿量、肌酐和尿素氮随尿排出量、渗透物质清除率和内生性肌酐清除率在试验后期也较模型组显著改善。 相似文献