全文获取类型
收费全文 | 35904篇 |
免费 | 2211篇 |
国内免费 | 3268篇 |
专业分类
林业 | 2160篇 |
农学 | 4404篇 |
基础科学 | 1697篇 |
2827篇 | |
综合类 | 12553篇 |
农作物 | 3783篇 |
水产渔业 | 842篇 |
畜牧兽医 | 6157篇 |
园艺 | 1978篇 |
植物保护 | 4982篇 |
出版年
2024年 | 366篇 |
2023年 | 887篇 |
2022年 | 1493篇 |
2021年 | 1487篇 |
2020年 | 1448篇 |
2019年 | 1695篇 |
2018年 | 1234篇 |
2017年 | 1450篇 |
2016年 | 1815篇 |
2015年 | 1993篇 |
2014年 | 2260篇 |
2013年 | 2157篇 |
2012年 | 2480篇 |
2011年 | 2280篇 |
2010年 | 1877篇 |
2009年 | 1797篇 |
2008年 | 1657篇 |
2007年 | 1782篇 |
2006年 | 1695篇 |
2005年 | 1387篇 |
2004年 | 1062篇 |
2003年 | 884篇 |
2002年 | 709篇 |
2001年 | 710篇 |
2000年 | 657篇 |
1999年 | 513篇 |
1998年 | 436篇 |
1997年 | 396篇 |
1996年 | 368篇 |
1995年 | 346篇 |
1994年 | 316篇 |
1993年 | 287篇 |
1992年 | 294篇 |
1991年 | 199篇 |
1990年 | 190篇 |
1989年 | 162篇 |
1988年 | 109篇 |
1987年 | 95篇 |
1986年 | 45篇 |
1985年 | 60篇 |
1984年 | 44篇 |
1983年 | 12篇 |
1982年 | 41篇 |
1981年 | 38篇 |
1980年 | 38篇 |
1979年 | 25篇 |
1978年 | 24篇 |
1977年 | 24篇 |
1976年 | 16篇 |
1955年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Alessandra Bertoli Anthea LoBue Luca Quattrini Stefania Sartini Beatrice Polini Sara Carpi Francesco Paolo Frontini Graziano Di Giuseppe Graziano Guella Paola Nieri Concettina La Motta 《Marine drugs》2022,20(11)
Euplotin C is a sesquiterpene of marine origin endowed with significant anti-microbial and anti-tumor properties. Despite the promising functional profile, its progress as a novel drug candidate has failed so far, due to its scarce solubility and poor stability in aqueous media, such as biological fluids. Therefore, overcoming these limits is an intriguing challenge for the scientific community. In this work, we synthesized β-cyclodextrin-based nanosponges and investigated their use as colloidal carriers for stably complex euplotin C. Results obtained proved the ability of the carrier to include the natural compound, showing remarkable values of both loading efficiency and capacity. Moreover, it also allowed us to preserve the chemical structure of the loaded compound, which was recovered unaltered once extracted from the complex. Therefore, the use of β-cyclodextrin-based nanosponges represents a viable option to vehiculate euplotin C, thus opening up its possible use as pharmacologically active compound. 相似文献
102.
Lena Stiefvatter Konstantin Frick Katja Lehnert Walter Vetter Alexander Montoya-Arroyo Jan Frank Ulrike Schmid-Staiger Stephan C. Bischoff 《Marine drugs》2022,20(11)
Dietary supplements that promote healthy aging are mostly warranted in an aging society. Because of age-related risks, anti-inflammatory and anti-oxidative agents such as microalgae are potential candidates for intervention. In a randomized controlled trial, we tested Phaeodactylum tricornutum (PT), a microalgae rich in eicosapentaenoic acid (EPA), carotenoids, vitamins, and β-glucans, cultured in bioreactors. In this pilot trial, 19 healthy elderly received supplements for two weeks based on either the whole PT (A), the β-1,3-glucan-rich PT supernatant (SupB), the combination thereof (A+SupB), or a Comparator product (Comp). The primary outcome variable plasma interleukin-6 was reduced after treatment with A+SupB compared to the Comp group (p = 0.04). The mobility parameters 5 s sit-to-stand test (p = 0.04 in the A group) and by trend gait speed (p = 0.08 in the A+SupB diet) were improved compared to Comp. No treatment effects were observed for fatty acids, compared to Comp but omega-6 to -3 fatty acid ratio (p = 0.006) and arachidonic acid/EPA ratio (p = 0.006) were reduced within group A+SupB. Further, the SupB study product reduced faecal zonulin (p = 0.03) compared to the Comp. The data revealed an anti-inflammatory and potentially anti-oxidative effect of particular PT preparations, suggesting that they might be suitable for effects in healthy elderly. 相似文献
103.
To explore the application of chitosan–gentamicin conjugate (CS-GT) in inhibiting Vibrio parahaemolyticus (V. parahaemolyticus), which is an important pathogen in aquatic animals worldwide, the antimicrobial activity of CS-GT and the effects of a CS-GT dose on the intestine histopathology and intestinal flora of V. parahaemolyticus-infected shrimps were explored. The results showed that CS-GT possessed broad-spectrum antibacterial activity, with minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and half inhibitory concentration (IC50) of 20.00 ± 0.01, 75.00 ± 0.02 and 18.72 ± 3.17 μg/mL for V. parahaemolyticus, respectively. Further scanning electron microscope and cell membrane damage analyses displayed that the electrostatic interaction of CS-GT with cell membrane strengthened after CS grafted GT, resulting in leakage of nucleic acid and electrolytes of V. parahaemolyticus. On the other hand, histopathology investigation indicated that high (100 mg/kg) and medium (50 mg/kg) doses of CS-GT could alleviate the injury of a shrimp’s intestine caused by V. parahaemolyticus. Further 16S rRNA gene sequencing analysis found high and medium dose of CS-GT could effectively inhabit V. parahaemolyticus invasion and reduce intestinal dysfunction. In conclusion, CS-GT possesses good antibacterial activity and could protect shrimps from pathogenic bacteria infection. 相似文献
104.
随着饲料企业逐步向专业化、集约化、规范化方向转变,人力要素已逐渐取代生产物质要素成为企业市场竞争力的核心要素,这就意味着现代化企业管理制度与人才激励机制已成为饲料企业体系中必须建立的环节.本文在探讨激励机制内涵与我国饲料企业管理中激励机制体系建立意义的基础上,审视了目前饲料企业激励机制模式的发展现状,并针对这一现状从企... 相似文献
105.
艾比湖流域绿洲稳定性研究 总被引:2,自引:0,他引:2
毋兆鹏 《干旱区资源与环境》2008,22(6):44-50
20世纪50年代以来,艾比湖流域绿洲荒漠化过程加剧,绿洲萎缩,稳定性严重失衡。由于绿洲是一个典型的灰色系统。因此,文章在探讨了基于水资源、土壤资源和植被资源表征下艾比湖流域绿洲稳定性变化机理的基础上,利用灰色系统理论的方法对绿洲稳定性的驱动机制进行了研究,诊断并分析了各影响因子在不同表征下对绿洲稳定性的贡献作用大小。结果表明:绿洲内外过度的人为活动是稳定性变化的主导驱动因素,为拓展绿洲学研究的新思路提供了有益的探索。 相似文献
106.
107.
高温胁迫影响食用菌的品质和产量,由高温引起的氧化胁迫是导致损伤的主要原因.以肺形侧耳(Pleurotus pulmonarius)热敏感菌株CCMSSC 00494和耐热菌株CCMSSC 00499为试验材料,研究了外源海藻糖对其菌丝体高温胁迫下氧化损伤的缓解效应.结果表明,高温(40℃)胁迫48 h,热敏感菌株中硫代巴比妥酸反应物(TBARS)含量(代表氧化损伤程度)高于耐热菌株.外源海藻糖处理可以显著降低高温胁迫下菌丝体内O2-产生速率、H2O2含量、脂氧合酶(LOX)活性和TBARS含量水平,缓解高温胁迫所引发的氧化损伤.另外,外源海藻糖对超氧化物歧化酶(SOD)活性有保护和提高的作用,对过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性有抑制作用,对过氧化物酶(POD)活性影响不明显.外源海藻糖对热敏感菌株的保护效应高于耐热菌株. 相似文献
108.
109.
对抗性番茄材料‘Hawaii 7996’分别接种强致病力青枯菌(RsH)和中等致病力青枯菌(RsM)后,利用双向电泳技术找到了两个差异表达蛋白质--谷胱甘肽S转移酶L3和Remorin 1蛋白。在利用携带八氢番茄红素脱氢酶基因PDS的TRV重组病毒载体通过叶片浸润法证明VIGS体系可行后,进一步利用该技术沉默上述两个蛋白质的对应基因GST-L3和Rem-1,并用半定量RT-PCR检测沉默效果。结果表明,分别沉默GST-L3和Rem-1的番茄植株抗性减弱,在接种中等致病力青枯菌(RsM)后青枯病发病率和病情指数都明显高于对照植株,说明基因GST-L3和Rem-1与番茄对青枯病的抗性相关。 相似文献
110.