全文获取类型
收费全文 | 76645篇 |
免费 | 5582篇 |
国内免费 | 5062篇 |
专业分类
87289篇 |
出版年
2024年 | 155篇 |
2023年 | 1039篇 |
2022年 | 2403篇 |
2021年 | 4090篇 |
2020年 | 2630篇 |
2019年 | 3249篇 |
2018年 | 3183篇 |
2017年 | 2315篇 |
2016年 | 3285篇 |
2015年 | 4834篇 |
2014年 | 5590篇 |
2013年 | 6031篇 |
2012年 | 7105篇 |
2011年 | 6216篇 |
2010年 | 3768篇 |
2009年 | 3382篇 |
2008年 | 3774篇 |
2007年 | 3392篇 |
2006年 | 2947篇 |
2005年 | 2403篇 |
2004年 | 1977篇 |
2003年 | 1665篇 |
2002年 | 1413篇 |
2001年 | 1239篇 |
2000年 | 1225篇 |
1999年 | 1126篇 |
1998年 | 664篇 |
1997年 | 655篇 |
1996年 | 667篇 |
1995年 | 620篇 |
1994年 | 543篇 |
1993年 | 377篇 |
1992年 | 568篇 |
1991年 | 435篇 |
1990年 | 406篇 |
1989年 | 284篇 |
1988年 | 244篇 |
1987年 | 234篇 |
1986年 | 166篇 |
1985年 | 193篇 |
1984年 | 109篇 |
1983年 | 117篇 |
1982年 | 71篇 |
1981年 | 58篇 |
1980年 | 37篇 |
1979年 | 61篇 |
1977年 | 30篇 |
1974年 | 38篇 |
1973年 | 34篇 |
1972年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.
RuiJie Zhang Xia Li YongShuai Jiang GuiYou Liu ChuanXing Li Fan Zhang Yun Xiao BinSheng Gong 《中国科学:生命科学英文版》2009,52(2):163-172
High-throughout single nucleotide polymorphism detection technology and the existing knowledge provide strong support for
mining the disease-related haplotypes and genes. In this study, first, we apply four kinds of haplotype identification methods
(Confidence Intervals, Four Gamete Tests, Solid Spine of LD and fusing method of haplotype block) into high-throughout SNP
genotype data to identify blocks, then use cluster analysis to verify the effectiveness of the four methods, and select the
alcoholism-related SNP haplotypes through risk analysis. Second, we establish a mapping from haplotypes to alcoholism-related
genes. Third, we inquire NCBI SNP and gene databases to locate the blocks and identify the candidate genes. In the end, we
make gene function annotation by KEGG, Biocarta, and GO database. We find 159 haplotype blocks, which relate to the alcoholism
most possibly on chromosome 1∼22, including 227 haplotypes, of which 102 SNP haplotypes may increase the risk of alcoholism.
We get 121 alcoholism-related genes and verify their reliability by the functional annotation of biology. In a word, we not
only can handle the SNP data easily, but also can locate the disease-related genes precisely by combining our novel strategies
of mining alcoholism-related haplotypes and genes with existing knowledge framework.
Supported by the National Natural Science Foundation of China (Grant Nos. 30570424, 60601010 and 30600367), the National High-Tech
Research and Development Program of China, (Grant No.2007AA02Z329), the Key Science and Technology Program of Heilongjiang
Province(Grant No.GB03C602-4), Natural Science Foundation of Heilongjiang Province (Grant No. F2008-02), Youth Science Foundation
of Harbin Medical University (Grant No. 060045) and Science Foundation of Heilongjiang Province Education Department (Grant
Nos. 11531113 and 1152hq28). 相似文献
892.
Restoring Eelgrass (Zostera marina L.) Habitats Using a Simple and Effective Transplanting Technique
Eelgrass beds in coastal waters of China have declined substantially over the past 30 years. In this study, a simple new transplanting technique was developed for eelgrass (Zostera marina L.) restoration. To assist in anchoring single shoots, several rhizomes of rooted shoots were bound to a small elongate stone (50–150 g) with biodegradable thread (cotton or hemp), and then the bound packet was buried at an angle in the sediments at a depth of 2–4 cm. This stone anchoring method was used to transplant eelgrass in early November 2009 and late May 2010 in Huiquan Bay, Qingdao. The method led to high success. Three month survivorship of the transplanted shoots at the two transplant sites was >95%. From April 20 to November 19, 2012, the following characteristics of the 2009 and 2010 transplanted eelgrass beds were monitored: morphological changes, shoot density, shoot height, leaf biomass, and sediment particle size. Results showed that the sexual reproduction period of the planted eelgrass was from April to August, and vegetative reproduction reached its peak in autumn. Maximum shoot height and biomass were observed in June and July. After becoming established, the transplanted eelgrass beds were statistically equal to natural eelgrass beds nearby in terms of shoot height, biomass, and seasonal variations. This indicates that the transplant technique is effective for eelgrass restoration in coastal waters. 相似文献
893.
Jiwen Wang Jinyu Wei Xiaoling Xu Wenting Pan Yunxia Ge Changchun Zhou Chao Liu Jia Gao Ming Yang Weimin Mao 《PloS one》2014,9(4)
China was one of the countries with highest esophageal squamous cell carcinoma (ESCC) incidence and mortality worldwide. Alcohol drinking has been identified as a major environmental risk-factor related to ESCC. The alcohol dehydrogenase (ADH) family are major enzymes involved in the alcohol-metabolizing pathways, including alcohol dehydrogenase 1B (ADH1B) and ADH1C. Interestingly, ADH1B and ADH1C genes locate tandemly with ADH7 in a genomic segment as a gene cluster, and are all polymorphic. Several ESCC susceptibility single nucleotide polymorphisms (SNPs) of the ADH1B-ADH1C-ADH7 cluster have been identified previously through a genome-wide association study (GWAS). In the study, we examined the association between five ADH1B-ADH1C-ADH7 cluster SNPs (rs1042026, rs17033, rs1614972, rs1789903 and rs17028973) and risk of developing ESCC. Genotypes were determined in two independent case-control sets from two regions of China. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by logistic regression. Our data demonstrated that these ADH1B-ADH1C-ADH7 cluster SNPs confer susceptibility to ESCC in these two case-control sets, which were consistent to results of the previous GWAS. 相似文献
894.
Background
Osteosarcoma is the most common primary bone cancer in growing adolescents and young adults. The prognostic role of C-reactive protein (CRP) in patients with osteosarcoma is not fully investigated. The purpose of this study is to perform a meta-analysis and literature review on the role of CRP in osteosarcoma and to assess the potential role of serum CRP as a prognostic factor for patients with osteosarcoma.Methods
A detailed literature search was made in Medline for related research publications written in English. Methodological quality of the studies was also evaluated. The data were extracted and assessed by two reviewers independently. Analysis of pooled data were performed, risk ratio (RR) and corresponding confidence intervals (CIs) were calculated and summarized respectively.Results
Final analysis of 397 patients from 2 eligible studies was performed. Combined RR of CRP expression suggested that the raised serum CRP level had an adverse prognostic effect on overall survival of patients with osteosarcoma (n = 397 in 2 studies; RR = 0.35; 95% CI: 0.18–0.68; p = 0.002). In the uni- and multivariate survival analysis, response rate and CRP levels were the only independent prognostic variables.Conclusions
The results of this meta-analysis suggest that CRP expression confers a worse prognosis in patients with osteosarcoma. Large prospective studies are necessary to provide solid data to confirm the prognostic significance of CRP. 相似文献895.
Zi-Yi Jin Ming Wu Ren-Qiang Han Xiao-Feng Zhang Xu-Shan Wang Ai-Ming Liu Jin-Yi Zhou Qing-Yi Lu Claire H. Kim Lina Mu Zuo-Feng Zhang Jin-Kou Zhao 《PloS one》2014,9(7)
Background
Although the International Agency for Research on Cancer (IARC) has classified various indoor air pollutants as carcinogenic to humans, few studies evaluated the role of household ventilation in reducing the impact of indoor air pollutants on lung cancer risk.Objectives
To explore the association between household ventilation and lung cancer.Methods
A population-based case-control study was conducted in a Chinese population from 2003 to 2010. Epidemiologic and household ventilation data were collected using a standardized questionnaire. Unconditional logistic regression was employed to estimate adjusted odds ratios (ORadj) and their 95% confidence intervals (CI).Results
Among 1,424 lung cancer cases and 4,543 healthy controls, inverse associations were observed for good ventilation in the kitchen (ORadj = 0.86, 95% CI: 0.75, 0.98), bedroom (ORadj = 0.90, 95% CI: 0.79, 1.03), and both kitchen and bedroom (ORadj = 0.87, 95% CI: 0.75, 1.00). Stratified analyses showed lung cancer inversely associated with good ventilation among active smokers (ORadj = 0.85, 95% CI: 0.72, 1.00), secondhand smokers at home (ORadj = 0.77, 95% CI: 0.63, 0.94), and those exposed to high-temperature cooking oil fumes (ORadj = 0.82, 95% CI: 0.68, 0.99). Additive interactions were found between household ventilation and secondhand smoke at home as well as number of household pollutant sources.Conclusions
A protective association was observed between good ventilation of households and lung cancer, most likely through the reduction of exposure to indoor air pollutants, indicating ventilation may serve as one of the preventive measures for lung cancer, in addition to tobacco cessation. 相似文献896.
Yanan Wang Zhonglin Tang Yaqi Sun Hongyang Wang Chao Wang Shaobo Yu Jing Liu Yu Zhang Bin Fan Kui Li Bang Liu 《PloS one》2014,9(9)
Copy number variations (CNVs) represent a substantial source of structural variants in mammals and contribute to both normal phenotypic variability and disease susceptibility. Although low-resolution CNV maps are produced in many domestic animals, and several reports have been published about the CNVs of porcine genome, the differences between Chinese and western pigs still remain to be elucidated. In this study, we used Porcine SNP60 BeadChip and PennCNV algorithm to perform a genome-wide CNV detection in 302 individuals from six Chinese indigenous breeds (Tongcheng, Laiwu, Luchuan, Bama, Wuzhishan and Ningxiang pigs), three western breeds (Yorkshire, Landrace and Duroc) and one hybrid (Tongcheng×Duroc). A total of 348 CNV Regions (CNVRs) across genome were identified, covering 150.49 Mb of the pig genome or 6.14% of the autosomal genome sequence. In these CNVRs, 213 CNVRs were found to exist only in the six Chinese indigenous breeds, and 60 CNVRs only in the three western breeds. The characters of CNVs in four Chinese normal size breeds (Luchuan, Tongcheng and Laiwu pigs) and two minipig breeds (Bama and Wuzhishan pigs) were also analyzed in this study. Functional annotation suggested that these CNVRs possess a great variety of molecular function and may play important roles in phenotypic and production traits between Chinese and western breeds. Our results are important complementary to the CNV map in pig genome, which provide new information about the diversity of Chinese and western pig breeds, and facilitate further research on porcine genome CNVs. 相似文献
897.
Albert S. Reger Matthew P. Yang Shizuyo Koide-Yoshida Elaine Guo Shrenik Mehta Keizo Yuasa Alan Liu Darren E. Casteel Choel Kim 《The Journal of biological chemistry》2014,289(37):25393-25403
cGMP-dependent protein kinase (PKG)-interacting proteins (GKIPs) mediate cellular targeting of PKG isoforms by interacting with their leucine zipper (LZ) domains. These interactions prevent aberrant signaling cross-talk between different PKG isotypes. To gain detailed insight into isotype-specific GKIP recognition by PKG, we analyzed the type II PKG leucine zipper domain and found that residues 40–83 dimerized and specifically interacted with Rab11b. Next, we determined a crystal structure of the PKG II LZ-Rab11b complex. The PKG II LZ domain presents a mostly nonpolar surface onto which Rab11b docks, through van der Waals interactions. Contact surfaces in Rab11b are found in switch I and II, interswitch, and the β1/N-terminal regions. This binding surface dramatically differs from that seen in the Rab11 family of interacting protein complex structures. Structural comparison with PKG Iα and Iβ LZs combined with mutagenic analysis reveals that GKIP recognition is mediated through surface charge interactions. 相似文献
898.
Infection of human dendritic cells by a sindbis virus replicon vector is determined by a single amino acid substitution in the E2 glycoprotein 总被引:5,自引:0,他引:5 下载免费PDF全文
Gardner JP Frolov I Perri S Ji Y MacKichan ML zur Megede J Chen M Belli BA Driver DA Sherrill S Greer CE Otten GR Barnett SW Liu MA Dubensky TW Polo JM 《Journal of virology》2000,74(24):11849-11857
The ability to target antigen-presenting cells with vectors encoding desired antigens holds the promise of potent prophylactic and therapeutic vaccines for infectious diseases and cancer. Toward this goal, we derived variants of the prototype alphavirus, Sindbis virus (SIN), with differential abilities to infect human dendritic cells. Cloning and sequencing of the SIN variant genomes revealed that the genetic determinant for human dendritic cell (DC) tropism mapped to a single amino acid substitution at residue 160 of the envelope glycoprotein E2. Packaging of SIN replicon vectors with the E2 glycoprotein from a DC-tropic variant conferred a similar ability to efficiently infect immature human DC, whereupon those DC were observed to undergo rapid activation and maturation. The SIN replicon particles infected skin-resident mouse DC in vivo, which subsequently migrated to the draining lymph nodes and upregulated cell surface expression of major histocompatibility complex and costimulatory molecules. Furthermore, SIN replicon particles encoding human immunodeficiency virus type 1 p55(Gag) elicited robust Gag-specific T-cell responses in vitro and in vivo, demonstrating that infected DC maintained their ability to process and present replicon-encoded antigen. Interestingly, human and mouse DC were differentially infected by selected SIN variants, suggesting differences in receptor expression between human and murine DC. Taken together, these data illustrate the tremendous potential of using a directed approach in generating alphavirus vaccine vectors that target and activate antigen-presenting cells, resulting in robust antigen-specific immune responses. 相似文献
899.
The scalloped and vestigial genes are both required for the formation of the Drosophila wing, and recent studies have indicated that they can function as a heterodimeric complex to regulate the expression of downstream target genes. We have analyzed the consequences of complete loss of scalloped function, ectopic expression of scalloped, and ectopic expression of vestigial on the development of the Drosophila wing imaginal disc. Clones of cells mutant for a strong allele of scalloped fail to proliferate within the wing pouch, but grow normally in the wing hinge and notum. Cells overexpressing scalloped fail to proliferate in both notal and wing-blade regions of the disc, and this overexpression induces apoptotic cell death. Clones of cells overexpressing vestigial grow smaller or larger than control clones, depending upon their distance from the dorsal-ventral compartment boundary. These studies highlight the importance of correct scalloped and vestigial expression levels to normal wing development. Our studies of vestigial-overexpressing clones also reveal two further aspects of wing development. First, in the hinge region vestigial exerts both a local inhibition and a long-range induction of wingless expression. These and other observations imply that vestigial-expressing cells in the wing blade organize the development of surrounding wing-hinge cells. Second, clones of cells overexpressing vestigial exhibit altered cell affinities. Our analysis of these clones, together with studies of scalloped mutant clones, implies that scalloped- and vestigial-dependent cell adhesion contributes to separation of the wing blade from the wing hinge and to a gradient of cell affinities along the dorsal-ventral axis of the wing. 相似文献
900.
Water extract of steam-exploded corn stalk (SECS) was detoxified and used as feed for acetone–butanol–ethanol (ABE) fermentation
using Clostridium beijerinckii. Utilization of water extract improved the total ABE yield (g ABE/g dry SECS). Separated fermentation showed higher fermentability
(0.078 g ABE/g dry SECS) over typical fermentation (0.058 g ABE/g dry SECS). Furthermore, the final ABE yields (g ABE/g utilized
sugar) from water extract neutralized by Ca(OH)2, NaOH, and Na2SO3 were 0.16, 0.1 and 0.07, respectively, suggesting that Ca(OH)2 had the best detoxification effect. 相似文献