全文获取类型
收费全文 | 16319篇 |
免费 | 1270篇 |
国内免费 | 1439篇 |
专业分类
19028篇 |
出版年
2024年 | 157篇 |
2023年 | 231篇 |
2022年 | 477篇 |
2021年 | 688篇 |
2020年 | 567篇 |
2019年 | 721篇 |
2018年 | 685篇 |
2017年 | 502篇 |
2016年 | 697篇 |
2015年 | 1031篇 |
2014年 | 1239篇 |
2013年 | 1217篇 |
2012年 | 1542篇 |
2011年 | 1439篇 |
2010年 | 900篇 |
2009年 | 794篇 |
2008年 | 1000篇 |
2007年 | 918篇 |
2006年 | 746篇 |
2005年 | 670篇 |
2004年 | 554篇 |
2003年 | 500篇 |
2002年 | 475篇 |
2001年 | 225篇 |
2000年 | 190篇 |
1999年 | 186篇 |
1998年 | 131篇 |
1997年 | 97篇 |
1996年 | 60篇 |
1995年 | 52篇 |
1994年 | 54篇 |
1993年 | 32篇 |
1992年 | 43篇 |
1991年 | 31篇 |
1990年 | 32篇 |
1989年 | 21篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1979年 | 4篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1970年 | 3篇 |
1966年 | 4篇 |
1965年 | 3篇 |
1964年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Min Li Chunmei Yu Yaoyi Wang Wentao Li Ying Wang Yun Yang Huihui Liu Yujuan Li Feng Tan Jian Zhang 《Current Genomics》2014,15(5):341-348
Willows are one of the most important tree species for landscaping, biofuel and raw timber. Screening salt-tolerant willow varieties is an effective approach to balance wood supply and demand. However, more salt-tolerant willow varieties are required and little is known regarding the mechanism of salt tolerance at the gene expression level. In this paper, two willow varieties were studies in terms of their differences in salt-tolerances and mechanism of salt tolerance at the level of VP1 gene expression. The results showed that Salix L0911 (L0911) had higher biomass than Salix matsudana (SM), and salt injuries were less severe in L0911 than in SM. The activities of peroxidase and superoxide dismutase, as well as the contents of soluble protein and proline, were higher in L0911 than in SM, whereas the contents of Na+ and K+, as well as the Na+/K+ ratio, were lower in L0911 than in SM. Two VP1 genes (VP1.1 and VP1.2) cloned in L0911 and SM had similar sequences and structures. VP1.1 and VP1.2 belonged to different subgroups. Total expression levels of the VP1.1 gene in both roots and leaves of L0911 were higher than that in SM under normal conditions. Under salt stress, expression of VP1 in SM roots initially increased and then decreased, whereas the expression of VP1 in leaves of L0911 and SM, as well as in roots of L0911, decreased with increasing salt concentrations. This study increased our understanding of the salt-tolerance mechanism of willow and may facilitate the selection of salt-tolerant willow resources. 相似文献
102.
Channel catfish virus (CCV) is a viral pathogen of fry and fingerling channel catfish and can cause significant commercial loss. Previous studies have shown that the CCV virion contains at least 25 predicted structural proteins, including viral protein 10, which is encoded by the orf10 gene of the CCV. In this paper, the orf10 gene was expressed in Escherichia coli and used to produce a specific antibody. Western blot analysis confirmed that open reading frame 10 is an envelope protein. A viral neutralization assay demonstrated that open reading frame 10 antiserum was able to inhibit CCV infection of channel catfish ovary cells, suggesting that viral protein 10 is likely to play an important role in the CCV infection of channel catfish ovary cells. 相似文献
103.
We have previously shown that the cultured L6 myoblasts are susceptible to menadione-induced oxidative stress. Damaged cells were detached from the culture dishes. In the present study, we focused on focal adhesion kinase (FAK), which plays pivotal roles in maintaining focal adhesion function and cell survival. FAK, normally localized at the focal adhesion regions of the myoblasts, was not observed at the regions under oxidative stress induced by menadione and H(2) O(2) . Two cleavage products, 80-kDa N-terminal FAK and 35-kDa C-terminal FAK fragments, as well as full-length FAK (125?kDa) were detected in myoblasts cultured under normal conditions by western blotting with anti-N-terminal FAK or anti-C-terminal FAK sera. Of interest was the finding that the cleavage products of FAK (but not full-length FAK) disappeared under oxidative stress. The cleavage of full-length FAK to N-terminal FAK and C-terminal FAK was inhibited by calpeptin, a specific calpain inhibitor. In addition, pre-incubation of cells with calpeptin resulted in a sharp decrease in survival signals, such as Akt phosphorylation and the ratio of Bcl-2/Bax, under stress conditions. By contrast, not only relative viability, but also Akt phosphorylation and the ratio of Bcl-2/Bax was significantly improved when cells were transfected with a DNA construct of N-terminal FAK-Myc. These results suggest that the N-terminal FAK positively regulates survival signalling in early phases of oxidative stress in the cultured myoblasts. 相似文献
104.
目的:探讨2型糖尿病患者氧化型低密度脂蛋白抗体(oxldl),preptin水平的变化及其与糖尿病并发症的关系。方法:选择第四军医大学西京医院内分泌代谢科2011年5月至2011年10月住院2型糖尿病患者80例,其中男性53例,女性27例,对患者的慢性并发症检查结果进行评分(方法见下文),总分以5分为界,分为重度并发症40例,轻度并发症40例。正常对照组30例,其中男性17例,女性13例,均检测其血清preptin、anti-oxldl、hsCRP、血脂(lipid)、糖化血红蛋白(HbA1C)、尿微量白蛋白(MAU)、空腹血糖(FBS)、空腹胰岛素(Fins)等水平,并进行各指标之间的相关分析。结果:2型糖尿病患者血清anti-oxldl水平增高,preptin水平降低。二者无相关性。结论:高水平的anti-oxldl和低水平的preptin对糖尿病慢性并发症的发生发展可能有促进作用。 相似文献
105.
Revealing interaction between sulfobutylether‐β‐cyclodextrin and reserpine by chemiluminescence and site‐directed molecular docking 下载免费PDF全文
The host–guest interaction between sulfobutylether‐β‐cyclodextrin (SBE‐β‐CD) and reserpine (RSP) is described using flow injection‐chemiluminescence (FI‐CL) and site‐directed molecular docking methods. It was found that RSP could inhibit the CL intensity produced by a luminol/SBE‐β‐CD system. The decrease in CL intensity was logarithmic over an RSP concentration range of 0.03 to 700.0 nM, giving a regression equation of ?I = 107.1lgCRES + 186.1 with a detection limit of 10 pM (3σ). The CL assay was successfully applied in the determination of RSP in injection, saliva and urine samples with recoveries in the range 93.5–106.1%. Using the proposed CL model, the binding constant (KCD‐R) and the stoichiometric ratio of SBE‐β‐CD/RSP were calculated to be 7.4 × 106 M‐1 and 1 : 1, respectively. Using molecular docking, it was confirmed that luminol binds to the small cavity of SBE‐β‐CD with a nonpolar interaction, while RSP targeted the larger cavity of SBE‐β‐CD and formed a 1 : 1 complex with hydrogen bonds. The proposed new CL method has the potential to become a powerful tool for revealing the host–guest interaction between CDs and drugs, as well as monitoring drugs with high sensitivity. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
106.
Fires change the diversity and composition of insects in forest ecosystems. In the present study, we examined the change of butterfly communities after a fire including the increase of butterfly richness, grassland species, and generalist species, and more changed communities. Butterflies were surveyed for 5 years after the big Uljin fire in 2007. During each year, butterflies were counted monthly by the line transect method from April to October at two sites (burned vs. unburned, ~ 1.5 km routes). Specialist grassland species decreased in the year of the fire but generalist species did not increase significantly. Butterfly richness did not change but butterfly diversity decreased due to a sudden increase of a species, Polygonia c-aureum. The butterfly community in the year of the fire was different from those in later years, showing temporary change of community in the year of the fire. Species composition was significantly different between burned and unburned sites, but this phenomenon cannot be interpreted as an influence of fire due to highly variable species composition of local butterfly assemblages and the non-repetitive sampling site of the present study. 相似文献
107.
Seung Kyoon Woo Min Seong Kwon Alexander Ivanov Volodymyr Gerzanich J. Marc Simard 《The Journal of biological chemistry》2013,288(5):3655-3667
The sulfonylurea receptor 1 (Sur1)-NCCa-ATP channel plays a central role in necrotic cell death in central nervous system (CNS) injury, including ischemic stroke, and traumatic brain and spinal cord injury. Here, we show that Sur1-NCCa-ATP channels are formed by co-assembly of Sur1 and transient receptor potential melastatin 4 (Trpm4). Co-expression of Sur1 and Trpm4 yielded Sur1-Trpm4 heteromers, as shown in experiments with Förster resonance energy transfer (FRET) and co-immunoprecipitation. Co-expression of Sur1 and Trpm4 also yielded functional Sur1-Trpm4 channels with biophysical properties of Trpm4 and pharmacological properties of Sur1. Co-assembly with Sur1 doubled the affinity of Trpm4 for calmodulin and doubled its sensitivity to intracellular calcium. Experiments with FRET and co-immunoprecipitation showed de novo appearance of Sur1-Trpm4 heteromers after spinal cord injury in rats. Our findings depart from the long-held view of an exclusive association between Sur1 and KATP channels and reveal an unexpected molecular partnership with far-ranging implications for CNS injury. 相似文献
108.
目的 :探讨K物质 (SK)对心肌细胞收缩的影响及机制。方法 :原代培养幼鼠心肌细胞 ,利用计算机图像分析系统测定SK处理前后心肌细胞收缩频率和收缩幅度的变化 ,同时观察预先加入速激肽受体拮抗剂DSP、β受体阻断剂心得安、α受体阻断剂酚妥拉明对SK作用的影响。结果 :当加入SK (1 .78× 1 0 - 5mol/L)到培养细胞中时 ,心肌细胞收缩幅度增强 ,但收缩频率变化不显著 ;且在 1 0 - 8~ 1 0 - 5mol/L浓度范围内心肌细胞收缩幅度变化呈剂量 效应关系 ;预先加入DSP可抑制SK对心肌细胞的影响 ,而心得安、酚妥拉明对SK的作用无影响。结论 :SK使心肌细胞的收缩幅度增强 ,其作用是由速激肽受体介导的 相似文献
109.
110.
Woo Young Chung Myungjae Song Jinhong Park Wan Namkung Jinu Lee Hyongbum Kim Min Goo Lee Joo Young Kim 《Biotechnology letters》2016,38(12):2023-2034
Objectives: To provide a simple method to make a stable ΔF508-CFTR-expressing T84 cell line that can be used as an efficient screening model system for ΔF508-CFTR rescue. Results: CFTR knockout cell lines were generated by Cas9 with a single-guide RNA (sgRNA) targeting exon 1 of the CFTR genome, which produced indels that abolished CFTR protein expressions. Next, stable ΔF508-CFTR expression was achieved by genome integration of ΔF508-CFTR via the lentivirus infection system. Finally, we showed functional rescue of ΔF508-CFTR not only by growing the cells at a low temperature, but also incubating with VX-809, a ΔF508-CFTR corrector, in the established T84 cells expressing ΔF508-CFTR. Conclusions: This cell system provides an appropriate screening platform for rescue of ΔF508-CFTR, especially related to protein folding, escaped from endoplasmic-reticulum-associated protein degradation, and membrane transport. 相似文献