全文获取类型
收费全文 | 5893篇 |
免费 | 385篇 |
国内免费 | 385篇 |
出版年
2024年 | 15篇 |
2023年 | 86篇 |
2022年 | 177篇 |
2021年 | 315篇 |
2020年 | 176篇 |
2019年 | 222篇 |
2018年 | 250篇 |
2017年 | 187篇 |
2016年 | 233篇 |
2015年 | 368篇 |
2014年 | 397篇 |
2013年 | 505篇 |
2012年 | 565篇 |
2011年 | 444篇 |
2010年 | 285篇 |
2009年 | 248篇 |
2008年 | 257篇 |
2007年 | 258篇 |
2006年 | 237篇 |
2005年 | 225篇 |
2004年 | 142篇 |
2003年 | 119篇 |
2002年 | 120篇 |
2001年 | 118篇 |
2000年 | 91篇 |
1999年 | 119篇 |
1998年 | 51篇 |
1997年 | 63篇 |
1996年 | 53篇 |
1995年 | 29篇 |
1994年 | 36篇 |
1993年 | 31篇 |
1992年 | 41篇 |
1991年 | 35篇 |
1990年 | 29篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 13篇 |
1986年 | 18篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1969年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有6663条查询结果,搜索用时 15 毫秒
91.
Characterization of functional microbial community in a membrane-aerated biofilm reactor operated for completely autotrophic nitrogen removal 总被引:12,自引:0,他引:12
The 16S rDNA-based molecular technique was applied to investigate the functional microbial community of a membrane-aerated biofilm (MAB) that was used for completely autotrophic nitrogen removal over nitrite (CANON). The relationships among two kinds of key bacteria responsible for CANON: aerobic ammonia-oxidizing bacteria (AOB) and Anammox bacteria, and their possible distributions in the MAB were discussed based on the microbial community analysis. FISH analysis showed the existence of two visible active layers in experimental MAB. One is the partial nitrifying layer located in the region of oxygen-rich membrane-biofilm interface, dominated by NSO190-positive AOB. The other is the Anammox active layer located in the region of anoxic liquid-biofilm interface, dominated by PLA46 and AMX820-positive Anammox microorganisms. As a result of this study, the AOB as well as Anammox bacteria were present and active in experimental MABR, and the cooperation between AOB and Anammox bacteria was considered to be responsible for CANON. 相似文献
92.
Preparation of cross-linked carboxymethyl chitosan for repairing sciatic nerve injury in rats 总被引:1,自引:0,他引:1
A successful nerve regeneration process was achieved with nerve repair tubes made up of 1-ethyl-3(3-dimethylaminopropyl) carbodiimide
hydrochloride (EDC) cross-linked carboxymethyl chitosan (CM-chitosan) with improved biodegradability. Chitosan has a very
slow degradation rate, while the EDC cross-linked CM-chitosan tubes degraded to 30% of original weight during 8 weeks of incubation
in lysozyme solution. In vitro cell culture indicated that the CM-chitosan films presented no cytotoxicity to Schwann cells.
From in vivo studies using a 10 mm rat sciatic nerve defect model investigated by histomorphometry analysis, the average diameter
of the fibers and the average thickness of myelin sheath in the CM-chitosan tubes were 3.7 ± 0.33 and 0.33 ± 0.04 μm, respectively,
which demonstrated equivalence to nerve autografts (the current “gold” standard); furthermore, the average fiber density in
the CM-chitosan tubes was 20.5 × 103/mm2, which was similar to that of autografts (21 × 103/mm2) and significantly higher than that of common chitosan tubes (15.3 × 103/mm2). 相似文献
93.
Salvador promotes both cell cycle exit and apoptosis through the modulation of both cyclin E and Drosophila inhibitor of apoptosis protein in Drosophila. However, the cellular function of human Salvador (hSav1) is rarely reported. To screen for novel binding proteins that interact with hSav1, the cDNA of hSav1 was cloned into a bait protein plasmid, and positive clones were screened from a human fetal liver cDNA library by the yeast two-hybrid system. hSav1 mRNA was expressed in yeast and there was no self-activation and toxicity in the yeast strain AH109. Twenty proteins were found to interact with hSav1, including HS1 (haematopoietic cell specific protein1)-associated protein X-1 (HAX-1); neural precursor cell expressed, developmentally down-regulated 9, pyruvate kinase, liver and RBC, cytochrome c oxidase subunit Vb, enoyl coenzyme A hydratase short chain 1, and NADH dehydrogenase (ubiquinone) 1 beta subcomplex, demonstrating that the yeast two-hybrid system is an efficient method for investigating protein interactions. Among the identified proteins, there were many mitochondrial proteins, indicating that hSav1 may play a role in mitochondrial function. We also confirmed the interaction of HAX-1 and hSav1 in mammalian cells. This investigation provides functional clues for further exploration of potential apoptosis-related proteins in disease biotherapy. 相似文献
94.
Yan Lu Shulin/SL Li Shiguo/SG Zhu Yabin/YB Gong Jun/J Shi Ling/ L Xu 《Biological procedures online》2017,19(1):2
DNA/RNA methylation plays an important role in lung cancer initiation and progression. Liquid biopsy makes use of cells, nucleotides and proteins released from tumor cells into body fluids to help with cancer diagnosis and prognosis. Methylation of circulating tumor DNA (ctDNA) has gained increasing attention as biomarkers for lung cancer. Here we briefly introduce the biological basis and detection method of ctDNA methylation, and review various applications of methylated DNA in body fluids in lung cancer screening, diagnosis, prognosis, monitoring and treatment prediction. We also discuss the emerging role of RNA methylation as biomarkers for cancer. 相似文献
95.
综述了鱼类病毒性神经坏死病的病原种类、危害性、防治方法以及神经坏死病毒的结构和理化特性等方面的研究进展。 相似文献
96.
Li-Long Pan Xin-Hua Liu Yao-Ling Jia Dan Wu Qing-Hui Xiong Qi-Hai Gong Yang Wang Yi-Zhun Zhu 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013
Background
Heme oxygenase-1 (HO-1) has potential anti-apoptotic properties. A novel compound [4-(2-acetoxy-3-((R)-3-(benzylthio)-1-methoxy-1-oxopropan-2- ylamino)-3-oxopropyl)-1,2-phenylene diacetate (DSC)] was synthesized by joining danshensu and cysteine through an appropriate linker. This study investigated if the cytoprotective properties of DSC involved the induction of HO-1.Methods
We evaluated the cytoprotective effects of DSC on H2O2-induced cell damage, apoptosis, intracellular and mitochondrial reactive oxygen species (ROS) production, mitochondrial membrane potential (ΔΨm) loss, and apoptosis-related proteins expression and its underlying mechanisms.Results
DSC concentration-dependently attenuated cell death, lactate dehydrogenase release, intracellular and mitochondrial ROS production, and ΔΨm collapse, modulated apoptosis-related proteins (Bcl-2, Bax, caspase-3, p53, and cleaved PARP) expression, and inhibited phosphorylation of extracellular signal-regulated kinase 1/2 in SH-SY5Y cells induced by H2O2. In addition, DSC concentration-dependently induced HO-1 expression associated with nuclear translocation of nuclear factor-erythroid 2 related factor 2 (Nrf-2), while the effect of DSC was inhibited by a phosphoinositide 3-kinase (PI3K) inhibitor LY294002. Furthermore, the protective effect of DSC on H2O2-induced cell death was abolished by HO-1 inhibitor ZnPP, but was mimicked by carbon monoxide-releasing moiety CORM-3 or HO-1 by-product bilirubin. Finally, DSC inhibited H2O2-induced changes of Bcl-2, Bax, and caspase-3 expression, and all of these effects were reversed by HO-1 silencing.Conclusions
Induction of HO-1 may be, at least in part, responsible for the anti-apoptotic property of DSC, an effect that involved the activation of PI3K/Akt/Nrf-2 axis.General significance
DSC might have the potential for beneficial therapeutic interventions for neurodegenerative diseases. 相似文献97.
华东稻麦轮作生态系统的N2O排放研究 总被引:39,自引:6,他引:39
根据对华东稻麦轮作周期的N2 O排放及其影响因子的连续观测结果 ,分析了N2 O排放时间变化以及施肥、灌溉、温度、土壤湿度和土壤速效N素含量对N2 O排放的影响 ,同时还比较分析了稻田N2 O和CH4排放 .研究结果表明 ,稻麦轮作周期内 ,水稻生长季的N2 O排放量仅占 30 % ,稻田持续淹水可比常规灌溉增加CH4排放量 2 6% ,减少N2 O排放量 1 1~ 2 6% . 相似文献
98.
酶法制备海洋活性肽及其功能活性研究进展 总被引:1,自引:0,他引:1
海洋生物活性肽(Marine biological active peptide)是从海洋生物中提取的具有优化机体代谢环境、有益于机体健康的一类多肽。酶法制备海洋生物活性肽是目前最常用的制备方法,是通过适当的蛋白酶水解海洋生物蛋白来制备生物活性肽的一种方法。海洋生物活性肽在降血压、抗氧化、抗凝血及抗菌等方面效果显著,对治疗和预防疾病具有巨大潜力。介绍海洋生物活性肽在酶解制备及其生物学功能方面国内外研究进展,为进一步开展海洋活性多肽研究提供参考。 相似文献
99.
100.
Gong M Wang JD Zhang J Yang H Lu XF Pei Y Cheng JQ 《Acta biochimica et biophysica Sinica》2006,38(4):233-240
A Bacillus strain,denoted as PY-1,was isolated from the vascular bundle of cotton.Biochemical,physiological and 16S rDNA sequence analysis proved that it should belong to Bacillus subtilis.The PY-1strain showed strong ability against many common plant fungal pathogens in vitro.The antibiotics producedby this strain were stable in neutral and basic conditions,and not sensitive to high temperature.From theculture broth of PY-1 strain,five antifungal compounds were isolated by acidic precipitation,methanolextraction,gel filtration and reverse-phase HPLC.Advanced identification was performed by mass spec-trometry and nuclear magnetic resonance spectroscopy.These five antifungal compounds were proved to bethe isomers of iturin A:A2,A3,A4,A6 and A7.In fast atom bombardment mass spectrometry/mass spec-trometry collision-induced dissociation spectra,fragmentation ions from two prior linear acylium ions wereobserved,and the prior ion,Tyr-Asn-Gln-Pro-Asn-Ser-βAA-Asn-CO~ ,was first reported. 相似文献