全文获取类型
收费全文 | 10460篇 |
免费 | 1035篇 |
国内免费 | 2463篇 |
专业分类
13958篇 |
出版年
2024年 | 71篇 |
2023年 | 228篇 |
2022年 | 399篇 |
2021年 | 611篇 |
2020年 | 474篇 |
2019年 | 566篇 |
2018年 | 554篇 |
2017年 | 417篇 |
2016年 | 475篇 |
2015年 | 778篇 |
2014年 | 860篇 |
2013年 | 828篇 |
2012年 | 1072篇 |
2011年 | 979篇 |
2010年 | 684篇 |
2009年 | 630篇 |
2008年 | 705篇 |
2007年 | 620篇 |
2006年 | 540篇 |
2005年 | 475篇 |
2004年 | 398篇 |
2003年 | 335篇 |
2002年 | 252篇 |
2001年 | 150篇 |
2000年 | 180篇 |
1999年 | 137篇 |
1998年 | 98篇 |
1997年 | 102篇 |
1996年 | 68篇 |
1995年 | 52篇 |
1994年 | 41篇 |
1993年 | 30篇 |
1992年 | 18篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 5篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 4篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 14篇 |
1981年 | 4篇 |
1976年 | 3篇 |
1973年 | 3篇 |
1965年 | 4篇 |
1962年 | 3篇 |
1961年 | 2篇 |
1950年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Plant Ecology - Seed germination and seedling recruitment are among the most critical stages for plant population persistence and development, which may be influenced by habitat fragmentation and... 相似文献
22.
The association of the FTO gene with obesity has been implicated in various human populations. The FTO gene is also most likely involved in the regulation of energy balance and feed intake. Here, the FTO gene was studied as a candidate gene for fatness and growth rate traits in pigs. The amino acid sequence of the FTO gene showed high conservation among human, pig, and other important domestic animals. Twelve variants including ten SNPs and two indels were detected, and then five SNPs within different genomic regions were genotyped in the ISU Berkshire × Yorkshire pig resource family. The linkage disequilibrium analyses revealed that most of these FTO variants were not in strong LD with each other. The SNPs c.46–139A > T within intron 1 and a synonymous mutation c.594C > G (Ala198Ala) within exon 3 had significant (P < 0.01) associations with average daily gain on test and total lipid percentage in muscle, respectively. Five major haplotypes were identified and the subsequent association analyses suggested that haplotype 2 (-CTTGG-) was the most favorable for increased growth rate, while haplotype 1 (-CTACG-) was unfavorably associated with intramuscular fatness traits. 相似文献
23.
24.
25.
We sought to study the corrosion behavior and surface properties of a commercial cobalt–chromium (Co–Cr) alloy which was fabricated with selective laser melting (SLM) technique. For this purpose, specimens were fabricated using different techniques, such as SLM system and casting methods. Surface hardness testing, microstructure observation, surface analysis using X-ray photoelectron spectroscopy (XPS) and electrochemical corrosion test were carried out to evaluate the corrosion properties and surface properties of the specimens. We found that microstructure of SLM specimens was more homogeneous than that of cast specimens. The mean surface hardness values of SLM and cast specimens were 458.3 and 384.8, respectively; SLM specimens showed higher values than cast ones in hardness. Both specimens exhibited no differences in their electrochemical corrosion properties in the artificial saliva through potentiodynamic curves and EIS, and no significant difference via XPS. Therefore, we concluded that within the scope of this study, SLM-fabricated restorations revealed good surface properties, such as proper hardness, homogeneous microstructure, and also showed sufficient corrosion resistance which could meet the needs of dental clinics. 相似文献
26.
27.
28.
Bin Sun Xiaofeng Zhang Xianshuo Cheng Yu Zhang Lei Chen Lehua Shi Zhenyu Liu Haihua Qian Mengchao Wu Zhengfeng Yin 《PloS one》2013,8(11)
Hepatic stellate cells (HSCs), a specialized stromal cytotype in the liver, have been demonstrated to actively contribute to hepatocellular carcinoma (HCC) development. However, the previous studies were performed using HSC cell lines, and the prognostic value of intratumoral HSCs (tHSCs) was unclear. Here we isolated tHSCs from fresh human HCC tissues, and analyzed the abilities of tHSCs to promote HCC progression by using in vitro assays for cell viability, migration and invasion as well as epithelial-mesenchymal transition (EMT) phenotype. 252 HCC patients who underwent hepatectomy were enrolled for analysis of tHSCs and E-cadherin expression in tumor tissues, and 55 HCC patients for analysis of tHSCs in tumor tissues and circulating tumor cells (CTCs) in blood. Prognostic factors were then identified. The results showed that coculture of tHSCs with HCC cells had a stronger effect on HCC cell viability, migration and invasion, accompanied with the acquisition of epithelial-mesenchymal transition (EMT) phenotype. In vivo cotransplantation of HCC cells with tHSCs into nude mice more efficiently promoted tumor formation and growth. Icaritin, a known apoptosis inducer of HSCs, was demonstrated to effectively inhibit tHSC proliferation in vitro and tHSC-induced HCC-promoting effects in vivo. Clinical evidence indicated that tHSCs were rich in 45% of the HCC specimens, tHSC-rich subtypes were negatively correlated either with E-cadherin expression in tumor tissues (r = -0.256, p < 0.001) or with preoperative CTCs in blood (r = -0.287, p = 0.033), and were significantly correlated with tumor size (p = 0.027), TNM staging (p = 0.018), and vascular invasion (p = 0.008). Overall and recurrence-free survival rates of tHSC-rich patients were significantly worse than those for tHSC-poor patients. Multivariate analysis revealed tHSC-rich as an independent factor for overall and recurrence-free survival. In conclusion, tHSCs provide a promising prognostic biomarker and a new treatment target for HCC. 相似文献
29.
30.
Zhangwei Wang Bin Li Shishan Yu Xuewen Lai Bo Liu Jie Chen Toshimitsu Hayashi 《Phytochemistry letters》2013,6(3):461-466
Chemical investigation of the aqueous extract of the aerial portion of Sibiraea angustata led to the isolation of eight new monoterpene acylglucosides named sibiraglucoside A–H (1–8) and two known monoterpenes, sibiraic acid (9) and sibiskoside (10). Their structures were elucidated through extensive spectroscopic data analysis (including 1D and 2D NMR and HRESIMS experiments) and compared to literature data. In the in vitro bioassay, all of the compounds showed moderate hypolipidemic effects. 相似文献