全文获取类型
收费全文 | 20383篇 |
免费 | 2277篇 |
国内免费 | 2416篇 |
专业分类
25076篇 |
出版年
2024年 | 62篇 |
2023年 | 255篇 |
2022年 | 623篇 |
2021年 | 926篇 |
2020年 | 796篇 |
2019年 | 895篇 |
2018年 | 902篇 |
2017年 | 730篇 |
2016年 | 890篇 |
2015年 | 1255篇 |
2014年 | 1488篇 |
2013年 | 1584篇 |
2012年 | 1845篇 |
2011年 | 1660篇 |
2010年 | 1191篇 |
2009年 | 993篇 |
2008年 | 1204篇 |
2007年 | 1089篇 |
2006年 | 931篇 |
2005年 | 805篇 |
2004年 | 784篇 |
2003年 | 788篇 |
2002年 | 777篇 |
2001年 | 465篇 |
2000年 | 338篇 |
1999年 | 340篇 |
1998年 | 219篇 |
1997年 | 183篇 |
1996年 | 162篇 |
1995年 | 141篇 |
1994年 | 126篇 |
1993年 | 86篇 |
1992年 | 80篇 |
1991年 | 76篇 |
1990年 | 68篇 |
1989年 | 64篇 |
1988年 | 40篇 |
1987年 | 34篇 |
1986年 | 38篇 |
1985年 | 17篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 23篇 |
1981年 | 16篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1975年 | 4篇 |
1972年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
941.
采用气相色谱-质谱联用技术对中药复方越鞠丸石油醚提取物中的成分进行鉴定,共鉴定出60种成分,并采用峰面积归一化法确定了各成分的相对含量。 相似文献
942.
943.
Yan Han Man To Ling Huawei Mao Jian Zheng Ming Liu Kwok Tai Lam Yuan Liu Wenwei Tu Yu-Lung Lau 《PloS one》2014,9(1)
Although smokers have increased susceptibility and severity of seasonal influenza virus infection, there is no report about the risk of 2009 pandemic H1N1 (pdmH1N1) or avian H9N2 (H9N2/G1) virus infection in smokers. In our study, we used mouse model to investigate the effect of cigarette smoke on pdmH1N1 or H9N2 virus infection. Mice were exposed to cigarette smoke for 21 days and then infected with pdmH1N1 or H9N2 virus. Control mice were exposed to air in parallel. We found that cigarette smoke exposure alone significantly upregulated the lung inflammation. Such prior cigarette smoke exposure significantly reduced the disease severity of subsequent pdmH1N1 or H9N2 virus infection. For pdmH1N1 infection, cigarette smoke exposed mice had significantly lower mortality than the control mice, possibly due to the significantly decreased production of inflammatory cytokines and chemokines. Similarly, after H9N2 infection, cigarette smoke exposed mice displayed significantly less weight loss, which might be attributed to lower cytokines and chemokines production, less macrophages, neutrophils, CD4+ and CD8+ T cells infiltration and reduced lung damage compared to the control mice. To further investigate the underlying mechanism, we used nicotine to mimic the effect of cigarette smoke both in vitro and in vivo. Pre-treating the primary human macrophages with nicotine for 72 h significantly decreased their expression of cytokines and chemokines after pdmH1N1 or H9N2 infection. The mice subcutaneously and continuously treated with nicotine displayed significantly less weight loss and lower inflammatory response than the control mice upon pdmH1N1 or H9N2 infection. Moreover, α7 nicotinic acetylcholine receptor knockout mice had more body weight loss than wild-type mice after cigarette smoke exposure and H9N2 infection. Our study provided the first evidence that the pathogenicity of both pdmH1N1 and H9N2 viruses was alleviated in cigarette smoke exposed mice, which might partially be attributed to the immunosuppressive effect of nicotine. 相似文献
944.
Wen Huang Ping Zhao Xiao Chen Ping Li Gaonian Zhao Mingming Xu Xiuying Chen Peng Xie 《Cell biochemistry and biophysics》2014,68(1):159-162
This study aims to compare the different latent infections of herpes simplex virus type I in a murine model. One hundred and twenty BALB/c mice were randomly assigned into either of three groups: intravenous inoculation group, ocular abrasion group, and intranasal inoculation group. Six weeks later, the trigeminal ganglia (TG) were removed to detect the expression of HSV-I antigen. HSV DNA in TG was also detected by polymerase chain reaction to confirm latent infection. The rate of HSV DNA in TG detected in the intravenous inoculation group was 18/22 and 22/26 in the ocular abrasion group, both of which were higher than the rate detected in the intranasal inoculation group (18/30). The expression of HSV antigen in TG in these three groups was all negative. Mortality rate in the intravenous inoculation group was 8/30, which was much higher than those of the two other groups. Intranasal virus dripping, cornea abrasion, and intravenous injection can detect latent HSV-I infection in a murine model. Compared to two other groups, the cornea abrasion group showed less severe signs, a quicker recovery rate in acute infection, and higher incidence rate of latent infection. Therefore, it is an ideal method in the presence of latent HSV-I infection. 相似文献
945.
In this work, the unfolding of CopC was used to elucidate details of the protein structure through different spectroscopic techniques. The interactions of CopC and its mutants with the anionic surfactant sodium dodecyl sulfate (SDS), guanidinium hydrochloride, and urea were monitored by fluorescence spectroscopy, far-UV circular dichroism spectroscopy, and fluorescence lifetime measurements. The interaction of SDS with CopC resulted in the formation of a partially folded intermediate. In this intermediate, the structure of the C-terminal is unfolded, whereas the N-terminal retains the native structure. Further, we have explored the effects of metals on the intermediate in aqueous surfactant. The results suggested that the Ag+ ion has a large effect on the unfolding induced by SDS. In addition, the binding capacity of the different unfolding degree protein toward Cu2+ indicated the high stability of the N-terminal. The protein–Cu2+ unfolding induced by guanidinium hydrochloride and urea caused the binding of Cu2+ to increase the stability of the N-terminal, which resulted in an intermediate in the unfolding process. The first transition corresponded to unfolding of the C-terminal, and the second transition was attributed to unfolding of the N-terminal. Furthermore, the anisotropy decay indicated that the motion of tryptophan occurred at a higher urea concentration, which suggested the high stability of the N-terminal. Steered molecular dynamics simulations also indicated that the structure of the N-terminal was rigid. 相似文献
946.
Ming‐Jen Hsu Yi‐Hsuan Wang Joen‐Rong Sheu 《Journal of cellular and molecular medicine》2014,18(7):1278-1289
The hydrophilic α‐tocopherol derivative, 2,2,5,7,8‐pentamethyl‐6‐hydroxychromane (PMC), is a promising alternative to vitamin E in clinical applications. Critical vascular inflammation leads to vascular dysfunction and vascular diseases, including atherosclerosis, hypertension and abdominal aortic aneurysms. In this study, we investigated the mechanisms of the inhibitory effects of PMC in vascular smooth muscle cells (VSMCs) exposed to pro‐inflammatory stimuli, lipopolysaccharide (LPS) combined with interferon (IFN)‐γ. Treatment of LPS/IFN‐γ‐stimulated VSMCs with PMC suppressed the expression of inducible nitric oxide synthase (iNOS) and matrix metalloproteinase‐9 in a concentration‐dependent manner. A reduction in LPS/IFN‐γ‐induced nuclear factor (NF)‐κB activation was also observed in PMC‐treated VSMCs. The translocation and phosphorylation of p65, protein phosphatase 2A (PP2A) inactivation and the formation of reactive oxygen species (ROS) were significantly inhibited by PMC in LPS/IFN‐γ‐activated VSMCs. However, neither IκBα degradation nor IκB kinase (IKK) or ribosomal s6 kinase‐1 phosphorylation was affected by PMC under these conditions. Both treatments with okadaic acid, a PP2A‐selective inhibitor, and transfection with PP2A siRNA markedly reversed the PMC‐mediated inhibition of iNOS expression, NF‐κB‐promoter activity and p65 phosphorylation. Immunoprecipitation analysis of the cellular extracts of LPS/IFN‐γ‐stimulated VSMCs revealed that p65 colocalizes with PP2A. In addition, p65 phosphorylation and PP2A inactivation were induced in VSMCs by treatment with H2O2, but neither IκBα degradation nor IKK phosphorylation was observed. These results collectively indicate that the PMC‐mediated inhibition of NF‐κB activity in LPS/IFN‐γ‐stimulated VSMCs occurs through the ROS‐PP2A‐p65 signalling cascade, an IKK‐IκBα‐independent mechanism. Therapeutic interventions using PMC may therefore be beneficial for the treatment of vascular inflammatory diseases. 相似文献
947.
microRNA-101 is a potent inhibitor of autophagy 总被引:2,自引:0,他引:2
Frankel LB Wen J Lees M Høyer-Hansen M Farkas T Krogh A Jäättelä M Lund AH 《The EMBO journal》2011,30(22):4628-4641
948.
Hon-Tsen Yu Gwo-Chin Ma Dong-Jay Lee Shih-Chien ChinHsien-Shao Tsao Sheng-Hai WuShu-Yi Shih Ming Chen 《Theriogenology》2011,75(1):55-64
The systematic status of Pholidota has been a matter of debate, particularly regarding the apparent inconsistency between morphological and molecular studies. The Sry gene, a master regulator of male sex determination in eutherian mammals, has not yet been used for phylogenetic analyses of extant mammals. The objective of the present study was to clone and characterize the complete gene (1300 base pairs; bp) and amino acid sequences (229 residues) of Sry from the Formosan pangolin (Manis pentadactyla pentadactyla), a member of Pholidota. The Sry amino acid identity between pangolin and other reported species ranged from 42.5% (mouse, Mus musculus) to 84.1% (European hare, Lepus europaeus). Sequence conservation was primarily in the high motility group (HMG) box (234 bp), whereas homology outside the HMG box was low. The cloned Sry was mapped to the pangolin Y chromosome by fluorescence in situ hybridization (FISH); this was confirmed to be the first Y-borne molecular marker identified in Pholidota. Based on Bayesian phylogenetic analysis for Sry HMG sequences from 36 representative taxa, including the Formosan pangolin, Pholidota was more closely related to Carnivora than to Xenarthra, consistent with the emerging molecular tree inferred from markers not located on the Y chromosome. In conclusion, this study characterized the gene structure of Sry of the Formosan pangolin and provided insights into the phylogenetic position of Pholidota. 相似文献
949.
Introduction
Autoimmune inflammation is a characteristic feature of rheumatoid arthritis (RA) and other autoimmune diseases. In the natural course of human autoimmune diseases, it is rather difficult to pinpoint the precise timing of the initial event that triggers the cascade of pathogenic events that later culminate into clinically overt disease. Therefore, it is a challenge to examine the early preclinical events in these disorders. Animal models are an invaluable resource in this regard. Furthermore, considering the complex nature of the pathogenic immune events in arthritis, microarray analysis offers a versatile tool to define the dynamic patterns of gene expression during the disease course. 相似文献950.
Wenxiu Wei Shida Li Hongmei Xu Feilong Zhou Yi Wen Zhimei Song Sijia Feng Runliang Feng 《AAPS PharmSciTech》2018,19(5):2041-2047
Macrolide antibiotics are lipophilic drugs with some limitations including low solubility, limited cellular permeation, patients discomfort, etc. With amphiphilic methoxy poly(ethylene glycol)-b-poly(ε-caprolactone) (MPEG-PCL) copolymer and azithromycin (AZT) as drug carrier and model drug, AZT-loaded micelles were prepared via thin-membrane hydration method in order to overcome these limitations. Encapsulation efficiency of AZT-loaded micelles was 94.40% with good storage stability for 28 days, and AZT’s water solubility was enhanced to 944 μg/mL. Fourier transform infrared spectrum and x-ray diffraction analysis indicated that AZT was enveloped into the micelles in amorphous form due to its interaction with the copolymer. AZT’s in vitro release from the AZT-loaded micelles demonstrated a slow and continuous behavior when compared with raw AZT. The release dynamics was accorded with Weibull equation, meaning that release amount of AZT lowered with time and was proportional to remaining amount of drug in the AZT-loaded micelles. Korsmeyer-Peppas fitting result suggested that drug release process was a classical Fickian diffusion-controlled manner. With Staphylococcus aureus as bacterial strain, antibacterial activity of the AZT-loaded micelles displayed was comparable with raw AZT. In conclusion, MPEG-PCL should be a promising carrier for macrolide antibiotic delivery in treatment of bacterial infections. 相似文献