首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2082篇
  免费   167篇
  国内免费   302篇
  2024年   14篇
  2023年   41篇
  2022年   81篇
  2021年   163篇
  2020年   93篇
  2019年   108篇
  2018年   94篇
  2017年   90篇
  2016年   135篇
  2015年   190篇
  2014年   187篇
  2013年   198篇
  2012年   222篇
  2011年   186篇
  2010年   131篇
  2009年   88篇
  2008年   94篇
  2007年   69篇
  2006年   71篇
  2005年   50篇
  2004年   56篇
  2003年   42篇
  2002年   28篇
  2001年   8篇
  2000年   16篇
  1999年   19篇
  1998年   12篇
  1997年   12篇
  1996年   7篇
  1995年   7篇
  1994年   6篇
  1993年   3篇
  1992年   1篇
  1991年   3篇
  1990年   1篇
  1989年   4篇
  1988年   2篇
  1987年   2篇
  1986年   1篇
  1984年   1篇
  1983年   1篇
  1981年   1篇
  1975年   4篇
  1974年   2篇
  1973年   6篇
  1953年   1篇
排序方式: 共有2551条查询结果,搜索用时 175 毫秒
61.
Parameters of the length-weight relationship (LWR) were estimated for four fish species [Beaufortia szechuanensis (Fang, 1930), Claea dabryi (Sauvage, 1874), Percocypris pingi (Tchang, 1930), and Yunnanilus sichuanensis Ding, 1995] from the Yalong River. Samples were collected seasonally from June 2018 to July 2019, using various fishing gears [set nets (mesh: 1.5 × 2.0 cm), hook, drift gill nets (three mesh sizes: 1.0; 2.0; 3.0 cm) and electro fishing]. Two new maximum standard length were recorded for C. dabryi and P. pingi.  相似文献   
62.
This study aimed to identify differential circular RNA (circRNA) in the plasma exosomes of patients with lung adenocarcinoma (LUAD) using high-throughput sequencing. First, exosomes were isolated using an exosome isolation kit and confirmed by Western blotting, transmission electron microscopy, and NanoSight Assay. Subsequently, plasma circRNA expression profiles were screened by high-throughput sequencing and confirmed by fluorescence quantitative real-time polymerase chain reaction (qRT-PCR) and Sanger sequencing. Finally, the circRNA-miRNA-mRNA network was performed to forecast the potential function of circRNAs. The result of high-throughput sequencing data documented that 182 differentially expressed exosomal circRNAs in all were screened, which included 105 that were upregulated and 78 that were downregulated in LUAD patients plasma compared with controls. The four upregulated circRNAs including circ_0001492, circ_0001346, circ_0000690, and circ_0001439 were identical to the sequencing data by qRT-PCR, and their latent circRNA-miRNA-mRNA interactions were exhibited. Taken together, our study firstly revealed the altered exosomal circRNA expression from plasma samples in patients with LUAD and supports the need for exploring their potential as biomarkers and the pathological effects of lung cancer.  相似文献   
63.
Aberrant expression of the tripartite motif containing 59 (TRIM59) has been reported to participate in the development and progression of various human cancers. However, its expression pattern and cellular roles in pancreatic cancer (PC) remains unclear. In our study, we found that TRIM59 expression was significantly increased in PC tissues and was positively correlated with several malignant behaviors and poor overall survival of PC patients based on bioinformatics analysis and immunohistochemistry staining. Functionally, small interfering RNA–mediated TRIM59 depletion inhibited cell proliferation and migration in vitro, while TRIM59 overexpression promoted cell proliferation and migration in vitro and drove tumor growth and liver metastasis in vivo. Mechanically, TRIM59 was found to enhance glycolysis through activating the PI3K/AKT/mTOR pathway, ultimately contributing to PC progression. Taken together, our results demonstrate that TRIM59 may be a potential predictor for PC and promotes PC progression via the PI3K/AKT/mTOR-glycolysis signaling pathway, which establishes the rationale for targeting the TRIM59-related pathways to treat PC.  相似文献   
64.
ABSTRACT

To evaluate the association between shift work and risk of type 2 diabetes mellitus, we searched PubMed, EMBASE and Web of Science from their inception to June 8, 2019. Observational studies examining the relationship between shift work and type 2 diabetes were included. Subgroup analyses were conducted to explore whether specific characteristics would affect the relationship. A dose-response relationship was estimated by using generalized least squares trend regression. Finally, twelve cohort studies and nine cross-sectional studies were included (inter-rater agreement, k = 0.96). The result of meta-analysis indicated that shift work was associated with an increased risk of type 2 diabetes (relative risk = 1.10, 95% confidence interval = 1.05–1.14). Subgroup analyses demonstrated that female shift workers have increased risk of type 2 diabetes while male not observed, health care workers showed the highest risk compared with civil servants and manual workers, and night shift and rotating shift were associated with an increased risk of type 2 diabetes. Dose-response meta-analysis based on three cohorts among female workers indicated that there might be a positive association between duration of shift work and the risk of type 2 diabetes. In conclusion, shift work is positively associated with an increased risk of type 2 diabetes. Among female workers, with the years of exposure to shift work prolonged, the risk of type 2 diabetes might increase accordingly. In the future, more studies are needed to confirm the results of dose-response analysis.  相似文献   
65.
Recurrent event data are widely encountered in clinical and observational studies. Most methods for recurrent events treat the outcome as a point process and, as such, neglect any associated event duration. This generally leads to a less informative and potentially biased analysis. We propose a joint model for the recurrent event rate (of incidence) and duration. The two processes are linked through a bivariate normal frailty. For example, when the event is hospitalization, we can treat the time to admission and length-of-stay as two alternating recurrent events. In our method, the regression parameters are estimated through a penalized partial likelihood, and the variance-covariance matrix of the frailty is estimated through a recursive estimating formula. Moreover, we develop a likelihood ratio test to assess the dependence between the incidence and duration processes. Simulation results demonstrate that our method provides accurate parameter estimation, with a relatively fast computation time. We illustrate the methods through an analysis of hospitalizations among end-stage renal disease patients.  相似文献   
66.
miR-222 participates in many cardiovascular diseases, but its effect on cardiac remodeling induced by diabetes is unclear. This study evaluated the functional role of miR-222 in cardiac fibrosis in diabetic mice. Streptozotocin (STZ) was used to establish a type 1 diabetic mouse model. After 10 weeks of STZ injection, mice were intravenously injected with Ad-miR-222 to induce the overexpression of miR-222. miR-222 overexpression reduced cardiac fibrosis and improved cardiac function in diabetic mice. Mechanistically, miR-222 inhibited the endothelium to mesenchymal transition (EndMT) in diabetic mouse hearts. Mouse heart fibroblasts and endothelial cells were isolated and cultured with high glucose (HG). An miR-222 mimic did not affect HG-induced fibroblast activation and function but did suppress the HG-induced EndMT process. The antagonism of miR-222 by antagomir inhibited HG-induced EndMT. miR-222 regulated the promoter region of β-catenin, thus negatively regulating the Wnt/β-catenin pathway, which was confirmed by β-catenin siRNA. Taken together, our results indicated that miR-222 inhibited cardiac fibrosis in diabetic mice via negatively regulating Wnt/β-catenin-mediated EndMT.  相似文献   
67.
Accumulated evidence has shown that pre-eclampsia (PE) is related to both maternal and utero-placental antiangiogenesis and inflammation. Remarkably, an elevated cell-free fetal DNA (cffDNA) level has been found in maternal circulation; however, it remains unclear whether this DNA can induce activation of cytosolic DNA sensor signaling pathways and lead to the development of PE. In this study, we found that trophoblast cells constitutively expressed the cytosolic DNA sensors, absent in melanoma 2 (AIM2) and interferon-inducible protein 16 (IFI16). The cffDNA and pro-inflammatory and antiangiogenic factors were present at higher concentrations in PE compared with the control group and correlated with the severity of PE. DNA stimulation significantly increased the AIM2 and IFI16 levels, consistent with the elevated AIM2 and IFI16 expression in women with PE, and elicited increased production of AIM2-mediated interleukin IL-8 (IL-8), IL-6 and CC chemokine ligand 2 (CCL2) and IFI16-mediated sEndoglin, sFlt-1 and CXCL10. Furthermore, enhancement of the inflammatory response was found to be induced by DNA exposure, but DNA exposure did not induce PE-like symptoms in pregnant mice. It is possible that elevated cffDNA could reflect the degree of placental damage and trigger cytosolic DNA sensor activation, which disrupts the immunity balance and, consequently, contributes to inflammatory and antiangiogenic responses. In conclusion, the results of this study suggest that circulating cffDNA levels are increased in preeclamptic women and act through AIM2 and IFI16 activation to promote the production of pro-inflammatory and antiangiogenic factors, which correlate with the severity of the disease, and may offer insights into the etiology and pathogenesis of PE.  相似文献   
68.
DNA methylation is one of the most important epigenetic alterations involved in the control of gene expression. Bisulfite sequencing of genomic DNA is currently the only method to study DNA methylation patterns at single-nucleotide resolution. Hence, next-generation sequencing of bisulfite-converted DNA is the method of choice to investigate DNA methylation profiles at the genome-wide scale. Nevertheless, whole genome sequencing for analysis of human methylomes is expensive, and a method for targeted gene analysis would provide a good alternative in many cases where the primary interest is restricted to a set of genes.Here, we report the successful use of a custom Agilent SureSelect Target Enrichment system for the hybrid capture of bisulfite-converted DNA. We prepared bisulfite-converted next-generation sequencing libraries, which are enriched for the coding and regulatory regions of 174 ADME genes (i.e. genes involved in the metabolism and distribution of drugs). Sequencing of these libraries on Illumina’s HiSeq2000 revealed that the method allows a reliable quantification of methylation levels of CpG sites in the selected genes, and validation of the method using pyrosequencing and the Illumina 450K methylation BeadChips revealed good concordance.  相似文献   
69.
70.

Background

The value of genotyping to predict variant phenotypes in patients with phenylalanine hydroxylase (Pah) deficiency is a matter of debate. However, there exists no comprehensive population relationship study focused on the Han Chinese.

Methods

We analyzed genotype–phenotype correlation for 186 different genotypes in 338 unrelated Chinese patients harboring 109 different Pah mutations. Two systems were used in this process. The first was a phenotype prediction system based on arbitrary values (AV) attributed to each mutation. The second was a pair-wise correlation analysis. The observed phenotype for AV analysis was the corresponding metabolic phenotype stratified according to the pretreatment phenylalanine (Phe) value.

Results

We found that the observed phenotype matched the predicted phenotype in 54.41% of 272 patients for whom AV information was available; the highest degree of concordance (61.83%) was found in patients with null/null genotypes, whereas the lowest “concordance rate” (32.69%) was observed for patients with expected mild-PKU phenotype. There are repeated inconsistencies for such mutations as R241C, R243Q, R261Q, V388M, V399V, R408Q, A434D and EX6-96A>G which are associated with variable phenotypes in patients with identical genotype. Significant correlations were disclosed between pretreatment Phe values and predicted residual activity (r = − 0.45643, P < 0.0001) or AV sum (r = − 0.59523, P < 0.0001).

Conclusion

Our study supports the notion that the Pah mutation genotype is the main determinant of metabolic phenotype in most patients in a particular population, and provided novel insights into the values that underpin the subsequent treatment and the prognosis of PKU in Chinese.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号