全文获取类型
收费全文 | 27304篇 |
免费 | 2369篇 |
国内免费 | 3384篇 |
出版年
2024年 | 42篇 |
2023年 | 275篇 |
2022年 | 627篇 |
2021年 | 1367篇 |
2020年 | 979篇 |
2019年 | 1227篇 |
2018年 | 1145篇 |
2017年 | 826篇 |
2016年 | 1146篇 |
2015年 | 1737篇 |
2014年 | 2038篇 |
2013年 | 2097篇 |
2012年 | 2637篇 |
2011年 | 2349篇 |
2010年 | 1482篇 |
2009年 | 1355篇 |
2008年 | 1575篇 |
2007年 | 1432篇 |
2006年 | 1319篇 |
2005年 | 1198篇 |
2004年 | 961篇 |
2003年 | 946篇 |
2002年 | 727篇 |
2001年 | 502篇 |
2000年 | 454篇 |
1999年 | 466篇 |
1998年 | 280篇 |
1997年 | 259篇 |
1996年 | 265篇 |
1995年 | 193篇 |
1994年 | 215篇 |
1993年 | 134篇 |
1992年 | 150篇 |
1991年 | 140篇 |
1990年 | 98篇 |
1989年 | 90篇 |
1988年 | 58篇 |
1987年 | 63篇 |
1986年 | 47篇 |
1985年 | 43篇 |
1984年 | 44篇 |
1983年 | 25篇 |
1982年 | 18篇 |
1981年 | 10篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1971年 | 2篇 |
1966年 | 1篇 |
1953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
971.
Background
Immune evasion is one of the recognized hallmarks of cancer. Inflammatory responses to cancer can also contribute directly to oncogenesis. Since the immune system is hardwired to protect the host, there is a possibility that cancers, regardless of their histological origins, endow themselves with a common and shared inflammatory cancer-associated molecular pattern (iCAMP) to promote oncoinflammation. However, the definition of iCAMP has not been conceptually and experimentally investigated.Methods and Findings
Genome-wide cDNA expression data was analyzed for 221 normal and 324 cancer specimens from 7 cancer types: breast, prostate, lung, colon, gastric, oral and pancreatic. A total of 96 inflammatory genes with consistent dysregulation were identified, including 44 up-regulated and 52 down-regulated genes. Protein expression was confirmed by immunohistochemistry for some of these genes. The iCAMP contains proteins whose roles in cancer have been implicated and others which are yet to be appreciated. The clinical significance of many iCAMP genes was confirmed in multiple independent cohorts of colon and ovarian cancer patients. In both cases, better prognosis correlated strongly with high CXCL13 and low level of GREM1, LOX, TNFAIP6, CD36, and EDNRA. An “Inflammatory Gene Integrated Score” was further developed from the combination of 18 iCAMP genes in ovarian cancer, which predicted overall survival. Noticeably, as a selective nuclear import protein whose immuno-regulatory function just begins to emerge, karyopherin alpha 2 (KPNA2) is uniformly up-regulated across cancer types. For the first time, the cancer-specific up-regulation of KPNA2 and its clinical significance were verified by tissue microarray analysis in colon and head-neck cancers.Conclusion
This work defines an inflammatory signature shared by seven epithelial cancer types and KPNA2 as a consistently up-regulated protein in cancer. Identification of iCAMP may not only serve as a novel biomarker for prognostication and individualized treatment of cancer, but also have significant biological implications. 相似文献972.
Chong Shen Ryan J. Delahanty Yu-Tang Gao Wei Lu Yong-Bing Xiang Ying Zheng Qiuyin Cai Wei Zheng Xiao-Ou Shu Jirong Long 《PloS one》2013,8(3)
Background
Age at natural menopause (ANM) is a complex trait with high heritability and is associated with several major hormonal-related diseases. Recently, several genome-wide association studies (GWAS), conducted exclusively among women of European ancestry, have discovered dozens of genetic loci influencing ANM. No study has been conducted to evaluate whether these findings can be generalized to Chinese women.Methodology/Principal Findings
We evaluated the index single nucleotide polymorphisms (SNPs) in 19 GWAS-identified genetic susceptibility loci for ANM among 3,533 Chinese women who had natural menopause. We also investigated 3 additional SNPs which were in LD with the index SNP in European-ancestry but not in Asian-ancestry populations. Two genetic risk scores (GRS) were calculated to summarize SNPs across multiple loci one for all SNPs tested (GRSall), and one for SNPs which showed association in our study (GRSsel). All 22 SNPs showed the same association direction as previously reported. Eight SNPs were nominally statistically significant with P≤0.05: rs4246511 (RHBDL2), rs12461110 (NLRP11), rs2307449 (POLG), rs12611091 (BRSK1), rs1172822 (BRSK1), rs365132 (UIMC1), rs2720044 (ASH2L), and rs7246479 (TMEM150B). Especially, SNPs rs4246511, rs365132, rs1172822, and rs7246479 remained significant even after Bonferroni correction. Significant associations were observed for GRS. Women in the highest quartile began menopause 0.7 years (P = 3.24×10−9) and 0.9 years (P = 4.61×10−11) later than those in the lowest quartile for GRSsel and GRSall, respectively.Conclusions
Among the 22 investigated SNPs, eight showed associations with ANM (P<0.05) in our Chinese population. Results from this study extend some recent GWAS findings to the Asian-ancestry population and may guide future efforts to identify genetic determination of menopause. 相似文献973.
Background
Despite the tremendous economic and health costs imposed on China by tobacco use, China lacks a proactive and systematic tobacco control surveillance and evaluation system, hampering research progress on tobacco-focused surveillance and evaluation studies.Methods
This paper uses online search query analyses to investigate changes in online search behavior among Chinese Internet users in response to the adoption of the national indoor public place smoking ban. Baidu Index and Google Trends were used to examine the volume of search queries containing three key search terms “Smoking Ban(s),” “Quit Smoking,” and “Electronic Cigarette(s),” along with the news coverage on the smoking ban, for the period 2009–2011.Findings
Our results show that the announcement and adoption of the indoor public place smoking ban in China generated significant increases in news coverage on smoking bans. There was a strong positive correlation between the media coverage of smoking bans and the volume of “Smoking Ban(s)” and “Quit Smoking” related search queries. The volume of search queries related to “Electronic Cigarette(s)” was also correlated with the smoking ban news coverage.Interpretation
To the extent it altered smoking-related online searches, our analyses suggest that the smoking ban had a significant effect, at least in the short run, on Chinese Internet users’ smoking-related behaviors. This research introduces a novel analytic tool, which could serve as an alternative tobacco control evaluation and behavior surveillance tool in the absence of timely or comprehensive population surveillance system. This research also highlights the importance of a comprehensive approach to tobacco control in China. 相似文献974.
975.
Biliary atresia (BA) is a devastating cholestatic liver disease targeting infants. Current diagnosis depends on surgical exploration of the biliary tree. The aim of the present study was to identify potential biomarkers for the diagnosis of biliary atresia (BA). Two-dimensional electrophoresis was utilized for the identification of proteins that were differentially expressed in liver biopsies of 20 BA patients and 12 infants with non-BA neonatal cholestasis (NC) as controls. Using mass spectrometry, we identified 15 proteins with expressions significantly altered. Out of the 15 proteins identified, heat shock protein (HSP) 90 was the most significantly altered and was down-regulated in BA samples compared to NC samples using immunoblotting analysis. Our findings suggest that HSP90 might be a potential biomarker for the diagnosis of BA and may be used for monitoring further development and therapy for BA. This study demonstrated that a comprehensive strategy of proteomic identification combined with further validation should be adopted in biomarker discovery. 相似文献
976.
Yong Yu Zhi-Qiang Liu Xiao-Yu Liu Li Yang Xiao-Rui Geng Gui Yang Zhi-Gang Liu Peng-Yuan Zheng Ping-Chang Yang 《PloS one》2013,8(6)
Background and aims
Loss of the endotoxin tolerance of intestinal epithelium contributes to a number of intestinal diseases. The etiology is not clear. Psychological stress is proposed to compromise the intestinal barrier function. The present study aims to elucidate the role of the stress-derived corticotropin releasing factor (CRF) in breaching the established intestinal epithelial endotoxin tolerance.Methods
Epithelial cells of HT-29, T84 and MDCK were exposed to lipopolysaccharide to induce the endotoxin tolerance; the cells were then stimulated with CRF. The epithelial barrier function was determined using as indicators of the endotoxin tolerant status. A water-avoid stress mouse model was employed to test the role of CRF in breaching the established endotoxin tolerance in the intestine.Results
The established endotoxin tolerance in the epithelial cell monolayers was broken down by a sequent exposure to CRF and LPS manifesting a marked drop of the transepithelial resistance (TER) and an increase in the permeability to a macromolecular tracer, horseradish peroxidase (HRP). The exposure to CRF also increased the expression of Cldn2 in the epithelial cells, which could be mimicked by over expression of TLR4 in epithelial cells. Over expression of Cldn2 resulted in low TER in epithelial monolayers and high permeability to HRP. After treating mice with the 10-day chronic stress, the intestinal epithelial barrier function was markedly compromised, which could be prevented by blocking either CRF, or TLR4, or Cldn2.Conclusions
Psychological stress-derived CRF can breach the established endotoxin tolerance in the intestinal mucosa. 相似文献977.
Massive Sorghum Collection Genotyped with SSR Markers to Enhance Use of Global Genetic Resources 总被引:2,自引:0,他引:2
Claire Billot Punna Ramu Sophie Bouchet Jacques Chantereau Monique Deu Laetitia Gardes Jean-Louis Noyer Jean-Fran?ois Rami Ronan Rivallan Yu Li Ping Lu Tianyu Wang Rolf T. Folkertsma Elizabeth Arnaud Hari D. Upadhyaya Jean-Christophe Glaszmann C. Thomas Hash 《PloS one》2013,8(4)
Large ex situ collections require approaches for sampling manageable amounts of germplasm for in-depth characterization and use. We present here a large diversity survey in sorghum with 3367 accessions and 41 reference nuclear SSR markers. Of 19 alleles on average per locus, the largest numbers of alleles were concentrated in central and eastern Africa. Cultivated sorghum appeared structured according to geographic regions and race within region. A total of 13 groups of variable size were distinguished. The peripheral groups in western Africa, southern Africa and eastern Asia were the most homogeneous and clearly differentiated. Except for Kafir, there was little correspondence between races and marker-based groups. Bicolor, Caudatum, Durra and Guinea types were each dispersed in three groups or more. Races should therefore better be referred to as morphotypes. Wild and weedy accessions were very diverse and scattered among cultivated samples, reinforcing the idea that large gene-flow exists between the different compartments. Our study provides an entry to global sorghum germplasm collections. Our reference marker kit can serve to aggregate additional studies and enhance international collaboration. We propose a core reference set in order to facilitate integrated phenotyping experiments towards refined functional understanding of sorghum diversity. 相似文献
978.
Liang Sun Cai-you Hu Xiao-hong Shi Chen-guang Zheng Ze-zhi Huang Ze-ping Lv Jin Huang Gang Wan Ke-yan Qi Si-ying Liang Lin Zhou Ze Yang 《PloS one》2013,8(8)
Background
The I405V polymorphism of the cholesteryl ester transfer protein gene (CETP) has been suggested to be a protective factor conferring longevity in Ashkenazi Jews, although findings in other races are not supportive. This paper describes a case-control study and a meta-analysis conducted to derive a more precise estimation of the association between CETP 405V and longevity.Methods
We enrolled 1,021 ethnic Han Chinese participants (506 in the longevity group and 515 controls), then performed a meta-analysis that integrated the current study and previously published ones. Pooled odds ratios (OR) were calculated for allele contrasts, dominant and recessive inheritance models to assess the association between CETP 405V and longevity according to the ethnic stratification.Results
Our case-control data indicated that CETP 405V is a longevity risk allele in all genetic models (P additive=0.008; P dominant=0.008, ORdominant=0.673; P recessive=0.017, ORrecessive=0.654) after adjustment for the apolipoprotein E (APOE) ε4 allele, body mass index and high-density lipoprotein cholesterol. A synergy was detected between 405V and APOE ε4 (P=0.001, OR=0.530). Eight studies were eligible for meta-analysis, which confirmed 405V is the risky allele against longevity in all genetic models: allele contrasts (OR=0.81, 95%CI=0.74-0.88), dominant model (OR=0.72, 95%CI=0.64-0.82) and recessive model (OR=0.80, 95%CI=0.67-0.96). After ethnic stratification, 405V remained a risk allele in East Asians but no significant association was found in Europeans or white Americans.Conclusion
Our case-control study suggests CETP 405V as a risk allele against longevity in Chinese. The meta-analysis suggests the involvement of CETP 405V is protective in Ashkenazi Jews but is a risk allele against longevity in the East Asian (Chinese) population. 相似文献979.
Liang Xiang Jingtan Su Guilan Zheng Jian Liang Guiyou Zhang Hongzhong Wang Liping Xie Rongqing Zhang 《PloS one》2013,8(6)
The initial growth of the nacreous layer is crucial for comprehending the formation of nacreous aragonite. A flat pearl method in the presence of the inner-shell film was conducted to evaluate the role of matrix proteins in the initial stages of nacre biomineralization in vivo. We examined the crystals deposited on a substrate and the expression patterns of the matrix proteins in the mantle facing the substrate. In this study, the aragonite crystals nucleated on the surface at 5 days in the inner-shell film system. In the film-free system, the calcite crystals nucleated at 5 days, a new organic film covered the calcite, and the aragonite nucleated at 10 days. This meant that the nacre lamellae appeared in the inner-shell film system 5 days earlier than that in the film-free system, timing that was consistent with the maximum level of matrix proteins during the first 20 days. In addition, matrix proteins (Nacrein, MSI60, N19, N16 and Pif80) had similar expression patterns in controlling the sequential morphologies of the nacre growth in the inner-film system, while these proteins in the film-free system also had similar patterns of expression. These results suggest that matrix proteins regulate aragonite nucleation and growth with the inner-shell film in vivo. 相似文献
980.
Background: Prenyl diphosphate synthase subunit 2 (PDSS2) gene has recently been reported as a potential tumor suppressor. The association of PDSS2 and non-small cell lung cancer (NSCLC) has not been known. Methods: To investigate its association with NSCLC, we examined the expression level of PDSS2 in 28 paired clinical samples of non-small cell lung cancer tissues and surrounding normal tissues. Results: PDSS2 was constitutionally expressed in normal lung tissues regardless of sex, race and smoking history. An overall decreased PDSS2 expression was found in the tumor tissues compared to surrounding normal tissues. Decrease in PDSS2 expression was more severe in poorly and poor-to-moderately differentiated lung cancers, while the decrease was not significant in moderately to well-differentiated tumors. Moreover, the expression of PDSS2 decreased more in higher pathological stage, and in patients with lymph node metastasis. The decrease in PDSS2 expression in tumor tissues was not related to sex or histological type of NSCLC, but was related to smoking history. No correlation has been found between PDSS2 and the clinical factors of EGRF, Ki-67 and p53. Conclusion: Taken together, decreased expression of PDSS2 in NSCLC was evident. This is an initial report for the expression of PDSS2 in relation to different factors in lung cancer. Loss of PDSS2 could serve as a potential biomarker in NSCLC development. The role of PDSS2 as a tumor suppressor, and the mechanism of its potential anti-tumor action in NSCLC warrant further investigation. 相似文献