全文获取类型
收费全文 | 19246篇 |
免费 | 1432篇 |
国内免费 | 1555篇 |
专业分类
22233篇 |
出版年
2024年 | 59篇 |
2023年 | 307篇 |
2022年 | 717篇 |
2021年 | 1219篇 |
2020年 | 744篇 |
2019年 | 875篇 |
2018年 | 837篇 |
2017年 | 618篇 |
2016年 | 849篇 |
2015年 | 1263篇 |
2014年 | 1453篇 |
2013年 | 1454篇 |
2012年 | 1831篇 |
2011年 | 1522篇 |
2010年 | 939篇 |
2009年 | 834篇 |
2008年 | 914篇 |
2007年 | 836篇 |
2006年 | 695篇 |
2005年 | 622篇 |
2004年 | 494篇 |
2003年 | 435篇 |
2002年 | 333篇 |
2001年 | 312篇 |
2000年 | 259篇 |
1999年 | 267篇 |
1998年 | 178篇 |
1997年 | 192篇 |
1996年 | 164篇 |
1995年 | 156篇 |
1994年 | 177篇 |
1993年 | 99篇 |
1992年 | 101篇 |
1991年 | 117篇 |
1990年 | 78篇 |
1989年 | 74篇 |
1988年 | 41篇 |
1987年 | 31篇 |
1986年 | 24篇 |
1985年 | 43篇 |
1984年 | 20篇 |
1983年 | 24篇 |
1982年 | 10篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1950年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Background
Due to shared transmission routes, hepatitis C virus (HCV) infection is highly prevalent among people infected with human immunodeficiency virus (HIV). Highly active antiretroviral therapy (HAART) is associated with hepatotoxicity, leading to the negative effects on patients with HIV/HCV co-infection. In order to provide valuable information for HCV management in this particular population, we investigated the HCV genotypes in HIV-infected individuals from Henan and Guangxi, the two provinces with the most HIV-infected cases in China.Methods
Individuals, who acquired HIV infection through various risk routes, were recruited from Henan and Guangxi. Test of antibodies against HCV (anti-HCV) was conducted, and detection of HCV RNA was performed by PCR amplification. HCV subtypes were determined by direct sequencing of amplicons, followed by phylogenetic analysis.Results
We recruited a total of 1,112 HIV-infected people in this present study. Anti-HCV was detected from 218 (50.1%) patients from Henan and 81 (12.0%) patients from Guangxi, respectively. The highest prevalence of HIV/HCV co-infection was observed from FBDs (former blood donors) (87.2%) in Henan and IDUs (intravenous drug users) (81.8%) in Guangxi, respectively. The seroprevalence rate of HCV among people with sexual contact was significantly higher in Henan than in Guangxi (18.7% vs. 3.5%, P<0.05). The positive rate of HCV RNA in Henan and Guangxi was 30.6% (133/435) and 11.2% (76/677), respectively. Moreover, we found that 20 anti-HCV negative samples were HCV positive by PCR amplification. HCV subtype 1b (52.7%) was predominant in Henan, followed by subtype 2a (41.9%). The most frequently detected subtypes in Guangxi were 6a (35.6%) and 3b (32.9%).Conclusion
The HCV genotype distributions were different in HIV-infected people from Henan and Guangxi. HIV/HCV co-infection was not only linked to the transmission routes, but also associated with the geographic position. 相似文献72.
73.
Identification and characterization of adipose triglyceride lipase (ATGL) gene in birds 总被引:1,自引:0,他引:1
Qinghua Nie Yongsheng Hu Liang Xie Chengguang Zhang Xu Shen Xiquan Zhang 《Molecular biology reports》2010,37(7):3487-3493
Adipose triglyceride lipase (ATGL) is a triglyceride hydrolysis lipase and is generally related to lipid metabolism in animals.
The ATGL gene was well studied in mammals, however very less was known in birds that differed significantly with mammals for
lipid metabolism. In this study, cloning, mRNA real time and association analysis was performed to characterize the ATGL gene in birds. Results showed that the obtained ATGL gene cDNA of parrot, quail, duck were 1,651 bp (NCBI accession number: GQ221784), 1,557 bp (NCBI accession number: GQ221783)
and 1,440 bp each, encoded 481-, 482- and 279-amino acid (AA) peptide, respectively. The parrot ATGL (pATGL) gene was found to predominantly express in breast muscle and leg muscle, and very higher ATGL mRNA level was also found in heart, abdominal fat and subcutaneous fat. The quail ATGL (qATGL) gene was also predominantly expressed in breast muscle and leg muscle, and then to a much lesser degree in heart. The duck
ATGL (dATGL) gene was found to predominantly express in subcutaneous fat and abdominal fat, quite higher ATGL mRNA was also found in heart, spleen, breast muscle and leg muscle. Blast analyses indicated the high homology of ATGL and
its patatin region, and moreover, and the active serine hydrolase motif (“GASAG” for “GXSXG”) and the glycine rich motif (“GCGFLG”
for “GXGXXG”) were completely conservative among 14 species. Association analyses showed that c.950+24C>A, c.950+45C>G, c.950+73G>A,
c.950+83C>T and c.950+128delA of chicken ATGL gene (cATGL) were all significantly or highly significantly with cingulated fat width (CFW) (P < 0.05 or P < 0.01), and c.777−26C>A, c.950+45C>G, c.950+73G>A and c.950+118C>T were all significantly or highly significantly with pH
value of breast muscle (BMPH) (P < 0.05). 相似文献
74.
Despite the importance of stem cells in plant and animal development, the common mechanisms of stem cell maintenance in both systems have remained elusive. Recently, the importance of hydrogen peroxide (H2O2) signaling in priming stem cell differentiation has been extensively studied in animals. Here, we show that different forms of reactive oxygen species (ROS) have antagonistic roles in plant stem cell regulation, which were established by distinct spatiotemporal patterns of ROS‐metabolizing enzymes. The superoxide anion () is markedly enriched in stem cells to activate WUSCHEL and maintain stemness, whereas H2O2 is more abundant in the differentiating peripheral zone to promote stem cell differentiation. Moreover, H2O2 negatively regulates biosynthesis in stem cells, and increasing H2O2 levels or scavenging leads to the termination of stem cells. Our results provide a mechanistic framework for ROS‐mediated control of plant stem cell fate and demonstrate that the balance between and H2O2 is key to stem cell maintenance and differentiation. 相似文献
75.
Li Wang Yun Xiao Yanyan Ping Jing Li Hongying Zhao Feng Li Jing Hu Hongyi Zhang Yulan Deng Jiawei Tian Xia Li 《PloS one》2014,9(8)
Cross-talk among abnormal pathways widely occurs in human cancer and generally leads to insensitivity to cancer treatment. Moreover, alterations in the abnormal pathways are not limited to single molecular level. Therefore, we proposed a strategy that integrates a large number of biological sources at multiple levels for systematic identification of cross-talk among risk pathways in cancer by random walk on protein interaction network. We applied the method to multi-Omics breast cancer data from The Cancer Genome Atlas (TCGA), including somatic mutation, DNA copy number, DNA methylation and gene expression profiles. We identified close cross-talk among many known cancer-related pathways with complex change patterns. Furthermore, we identified key genes (linkers) bridging these cross-talks and showed that these genes carried out consistent biological functions with the linked cross-talking pathways. Through identification of leader genes in each pathway, the architecture of cross-talking pathways was built. Notably, we observed that linkers cooperated with leaders to form the fundamentation of cross-talk of pathways which play core roles in deterioration of breast cancer. As an example, we observed that KRAS showed a direct connection to numerous cancer-related pathways, such as MAPK signaling pathway, suggesting that it may be a central communication hub. In summary, we offer an effective way to characterize complex cross-talk among disease pathways, which can be applied to other diseases and provide useful information for the treatment of cancer. 相似文献
76.
Wen Fan Lei Xu Liangcai Xie Decai Yang Xuezheng Liu Jiajun Zhang Yirong Li Cunjian Yi 《PloS one》2014,9(8)
Background
The chemiluminescent microparticle immunoassay (CMIA) is widely used for the quantitative determination of B-type natriuretic peptide (BNP) in human ethylenediaminetetraacetic acid plasma. Rheumatoid factor (RF) is usually thought to result in a positive interference in immunoassays, but it is not clear whether its presence in plasma can lead to interferences in the CMIA of BNP.Methods
The estimation of BNP recovery was carried out by diluting high-concentration BNP samples with RF-positive or RF-negative plasma at a ratio of 1∶9. The diluted samples were then tested using the ARCHITECT i2000 System and ARCHITECT BNP Reagent Kits and the recovery was then calculated.Results
When the RF level ranged from 48 to 1420 IU/mL, the average recovery of BNP was 79.29% and 91.61% in the RF-positive and RF-negative plasma samples, respectively, and was thus significantly lower in the group of RF-positive plasma samples than in the group of RF-negative plasma samples. At a dilution of 1∶16, the measured BNP level increased by >36% in six of the seven RF-positive plasma samples. The recovery of BNP increased significantly in the RF-positive plasma samples after pretreatment with IgG-sensitive latex particles. In addition, The BNP recovery was not significantly related to the plasma RF at concentrations ranging from 48 to 2720 IU/mL.Conclusions
Measurement of BNP by CMIA is susceptible to interference from RF leading to predominantly (but not exclusively) lower results. Pretreatment of samples with blocking reagents is advisable prior to the initiation of denying patient''s necessary treatment. 相似文献77.
Rongzhong Huang Hongchang Gao Lihua Ma Xiao Wang Jianmin Jia Mingju Wang Liang Zhang Xia Liu Peng Zheng Liu Yang Lei Yang Li Dan Xie Peng 《Metabolomics : Official journal of the Metabolomic Society》2014,10(1):33-41
Herpes simplex virus type 1 (HSV-1) is a large, neurotropic, double-stranded DNA virus that establishes a lifelong latent infection in neurons and glial cells. Previous studies reveal that several metabolic perturbations are associated with HSV-1 infection. However, the extracellular metabolic alterations associated with HSV-1 infection have not been systematically profiled in human cells. Here, a proton nuclear magnetic resonance-based metabonomic approach was applied to differentiate the extracellular metabonomic profiles of HSV-1 infected human oligodendroglia cells (n = 18) and matched control cells (n = 18) at three time points (12, 24, and 36 h post-infection). Resulting spectra were analyzed by chemometric and statistical methods. Metabonomic profiling revealed perturbations in 21 extracellular metabolites. Partial least squares discriminant analysis demonstrated that the whole metabolic patterns enabled statistical discrimination between HSV-1 infected human oligodendroglia cells and control cells. Eight extracellular metabolites, seven of which were amino acids, were primarily responsible for score plot discrimination between HSV-1 infected human oligodendroglia cells and control cells at 36 h post-infection: alanine, glycine, isoleucine, leucine, glutamate, glutamine, histidine, and lactate. HSV-1 infection alters amino acid metabolism in human oligodendroglia cells cultured in vitro. HSV-1 infection may disturb these host cellular pathways to support viral replication. Through elucidating the extracellular metabolic changes incident to HSV-1 infection, this study also provides future directions for investigation into the pathogenic mechanism of HSV-1. 相似文献
78.
79.
Sanitary landfilling is a proven way for disposal of municipal solid waste (MSW) in developed countries in general and in developing countries in particular, owing to its low immediate costs. On the other hand, landfilling is a matter of concern due to its generation of heavily polluted leachate. Landfill leachate becomes more refractory with time and is very difficult to treat using conventional biological processes. The aged refuse-based bioreactor/biofilter (ARB) has been shown to be a promising technology for the removal of various pollutants from landfill leachate and validates the principle of waste control by waste. Based on different environmental and operational factors, many researchers have reported remarkable pollutant removal efficiencies using ARB. This paper gives an overview of various types of ARBs used; their efficiencies; and certain factors like temperatures, loading rates, and aerobic/anaerobic conditions which affect the performance of ARBs in eliminating pollutants from leachate. Treating leachate by ARBs has been proved to be more cost-efficient, environment friendly, and simple to operate than other traditional biological techniques. Finally, future research and developments are also discussed. 相似文献
80.