全文获取类型
收费全文 | 9264篇 |
免费 | 621篇 |
国内免费 | 634篇 |
专业分类
10519篇 |
出版年
2024年 | 23篇 |
2023年 | 100篇 |
2022年 | 242篇 |
2021年 | 437篇 |
2020年 | 302篇 |
2019年 | 374篇 |
2018年 | 361篇 |
2017年 | 272篇 |
2016年 | 346篇 |
2015年 | 561篇 |
2014年 | 675篇 |
2013年 | 724篇 |
2012年 | 810篇 |
2011年 | 772篇 |
2010年 | 449篇 |
2009年 | 424篇 |
2008年 | 478篇 |
2007年 | 401篇 |
2006年 | 365篇 |
2005年 | 304篇 |
2004年 | 264篇 |
2003年 | 233篇 |
2002年 | 187篇 |
2001年 | 176篇 |
2000年 | 154篇 |
1999年 | 141篇 |
1998年 | 104篇 |
1997年 | 95篇 |
1996年 | 84篇 |
1995年 | 74篇 |
1994年 | 83篇 |
1993年 | 66篇 |
1992年 | 72篇 |
1991年 | 66篇 |
1990年 | 66篇 |
1989年 | 54篇 |
1988年 | 32篇 |
1987年 | 36篇 |
1986年 | 25篇 |
1985年 | 28篇 |
1984年 | 10篇 |
1983年 | 17篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Lan Zhang Hui Ding Dan-Hui Wang Yan-Li Zhang Andrius Baskys Piu Chan Yu Zhong Yan-Ning Cai 《PloS one》2013,8(8)
Recent studies point to an association between the late-onset sporadic Parkinson’s disease (PD) and single nucleotide polymorphisms (SNPs) rs1559085 and rs27852 in Ca2+-dependent protease calpain inhibitor calpastatin (CAST) gene. This finding is of interest since loss of CAST activity could result in over activated calpain, potentially leading to Ca2+ dysregulation and loss of substantia nigra neurons in PD. We explored the association between CAST SNPs and late-onset sporadic PD in the Han Chinese population. The study included 615 evaluable patients (363 male, 252 female) with PD and 636 neurologically healthy controls (380 male, 256 female) matched for age, gender, ethnicity, and area of residence. PD cases were identified from the PD cohort of the Chinese National Consortium on Neurodegenerative Diseases (www.chinapd.cn). A total of 24 tag-SNPs were genotyped capturing 95% of the genetic variation across the CAST gene. There was no association found between any of the polymorphisms and PD in all models tested (co-dominant, dominant-effect and recessive-effect). Similarly, none of the common haplotypes was associated with a risk for PD. Our data do not support a significant association between the CAST gene polymorphisms and late onset sporadic PD in the Han Chinese population. 相似文献
102.
103.
104.
Dong Ding Guichen Chen Bochan Wang Qilan Wang Demei Liu Min Peng Ping Shi 《Annals of microbiology》2013,63(1):259-266
In this study, 53 actinomycetes strains were isolated from desert ecosystems located in northeast of Qinghai-Tibet Plateau and grouped into four RFLP patterns. Twenty-six actinomycetes with obvious morphology differences were chosen for phylogenetic diversity study and antimicrobial testing. As a result, the 16S rRNA gene sequencing showed that these strains belonged to Streptomyces, Micromonospora, Saccharothrix, Streptosporangium and Cellulomonas, and that most of the strains had antimicrobial bioactivity. The PKS and NRPS genes detection indicated diversified potential bioactive products of actinomycetes in this ecosystem. Among these strains, Sd-31 was chosen to study the bioactive products using HPLC-MS because of its optimum antimicrobial bioactivity. The result showed that it might produce Granatomycin A, Granatomycin C, and an unknown compound. 相似文献
105.
Jie Ma Wenbo Li Yongzhuang Lv Cheng Chang Songfeng Wu Lei Song Chen Ding Handong Wei Fuchu He Ying Jiang Yunping Zhu 《Proteomics》2013,13(15):2238-2242
In this study, we examined the use of multiple proteases (trypsin, LysC, tandem LysC/trypsin) on both protein identification and quantification in the Lys‐labeled SILAC mouse liver. Our results show that trypsin and tandem LysC/trypsin digestion are superior to LysC in peptides and protein identification while LysC shows advantages in quantification of Lys‐labeled proteins. Combination of experimental results from different proteases (LysC and trypsin) enabled a significant increase in the number of identified protein and protein can be quantified. Thus, taking advantage of the complementation of different protease should be a good strategy to improve both qualitative and quantitative proteomics research. 相似文献
106.
107.
Liyi Mai Anna Yao Jing Li Qiong Wei Ming Yuchi Xiaoling He Mingyue Ding Qibing Zhou 《PloS one》2013,8(4)
Nanobubbles and microbubbles are non-invasive ultrasound imaging contrast agents that may potentially enhance diagnosis of tumors. However, to date, both nanobubbles and microbubbles display poor in vivo tumor-selectivity over non-targeted organs such as liver. We report here cyanine 5.5 conjugated nanobubbles (cy5.5-nanobubbles) of a biocompatible chitosan–vitamin C lipid system as a dual ultrasound-fluorescence contrast agent that achieved tumor-selective imaging in a mouse tumor model. Cy5.5-nanobubble suspension contained single bubble spheres and clusters of bubble spheres with the size ranging between 400–800 nm. In the in vivo mouse study, enhancement of ultrasound signals at tumor site was found to persist over 2 h while tumor-selective fluorescence emission was persistently observed over 24 h with intravenous injection of cy5.5-nanobubbles. In vitro cell study indicated that cy5.5-flurescence dye was able to accumulate in cancer cells due to the unique conjugated nanobubble structure. Further in vivo fluorescence study suggested that cy5.5-nanobubbles were mainly located at tumor site and in the bladder of mice. Subsequent analysis confirmed that accumulation of high fluorescence was present at the intact subcutaneous tumor site and in isolated tumor tissue but not in liver tissue post intravenous injection of cy5.5-nanobubbles. All these results led to the conclusion that cy5.5-nanobubbles with unique crosslinked chitosan–vitamin C lipid system have achieved tumor-selective imaging in vivo. 相似文献
108.
Fusheng Jiang Weiping Li Yanfen Huang Yitao Chen Bo Jin Nipi Chen Zhishan Ding Xinghong Ding 《PloS one》2013,8(2)
This study was carried out to evaluate the utilization probability of the fibrous root part (FRP) of Bletilla striata, which was usually discarded and harvesting pseudobulb part (PSP). The chemical composition, total phenolic content, DPPH radical scavenging activity, Ferric-reducing antioxidant power and tyrosinase inhibition activity were compared between FRP and PSP. Antioxidant and pro-oxidant effect as well as antitumor effect of the extract of FRP and PSP were analyzed by in vitro cell system as well. Thin layer chromatography and high performance liquid chromatography analysis indicated that the chemical compositions in the two parts were similar, but the content in FRP was much higher than PSP. Meanwhile, the FRP extracts showed higher phenolic content, stronger DPPH scavenging activity, Ferric-reducing antioxidant capacity and tyrosinase inhibition activity. Sub-fraction analysis revealed that the distribution characteristic of phenolic components and other active constituents in FRP and PSP were consistent, and mainly deposited in chloroform and acetoacetate fractions. Especially, the chloroform sub-fraction (sch) of FRP showed extraordinary DPPH scavenging activity and tyrosinase inhibition activity, with IC50 0.848 mg/L and 4.3 mg/L, respectively. Besides, tyrosinase inhibition activity was even stronger than the positive compound arbutin (31.8 mg/L). Moreover, In vitro cell system analysis confirmed that FRP extract exerts comparable activity with PSP, especially, the sub-fraction sch of FRP showed better antioxidant activity at low dosage and stronger per-oxidant activity at high dosage, and both sch of FRP and PSP can dose-dependent induce HepG2 cells apoptosis, which implied tumor therapeutic effect. Considering that an additional 0.3 kg FRP would be obtained when producing 1.0 kg PSP, our work demonstrated that FRP is very potential to be used together with PSP. 相似文献
109.
110.
Xu Feng Peng Feng Huilin Yu Xingyu Yu Qi Sun Siyu Liu Thuy Nguyen Minh Jun Chen Di Wang Qing Zhang Lei Cao Changmei Zhou Qiang Li Jialei Xiao Shihua Zhong Aoxue Wang Lijuan Wang Hongyu Pan Xiaodong Ding 《Plant, cell & environment》2020,43(5):1192-1211
Although the function and regulation of SnRK1 have been studied in various plants, its molecular mechanisms in response to abiotic stresses are still elusive. In this work, we identified an AP2/ERF domain-containing protein (designated GsERF7) interacting with GsSnRK1 from a wild soybean cDNA library. GsERF7 gene expressed dominantly in wild soybean roots and was responsive to ethylene, salt, and alkaline. GsERF7 bound GCC cis-acting element and could be phosphorylated on S36 by GsSnRK1. GsERF7 phosphorylation facilitated its translocation from cytoplasm to nucleus and enhanced its transactivation activity. When coexpressed in the hairy roots of soybean seedlings, GsSnRK1(wt) and GsERF7(wt) promoted plants to generate higher tolerance to salt and alkaline stresses than their mutated species, suggesting that GsSnRK1 may function as a biochemical and genetic upstream kinase of GsERF7 to regulate plant adaptation to environmental stresses. Furthermore, the altered expression patterns of representative abiotic stress-responsive and hormone-synthetic genes were determined in transgenic soybean hairy roots after stress treatments. These results will aid our understanding of molecular mechanism of how SnRK1 kinase plays a cardinal role in regulating plant stress resistances through activating the biological functions of downstream factors. 相似文献