全文获取类型
收费全文 | 10438篇 |
免费 | 985篇 |
国内免费 | 734篇 |
出版年
2024年 | 13篇 |
2023年 | 86篇 |
2022年 | 224篇 |
2021年 | 345篇 |
2020年 | 296篇 |
2019年 | 385篇 |
2018年 | 368篇 |
2017年 | 314篇 |
2016年 | 458篇 |
2015年 | 615篇 |
2014年 | 769篇 |
2013年 | 788篇 |
2012年 | 932篇 |
2011年 | 850篇 |
2010年 | 603篇 |
2009年 | 546篇 |
2008年 | 669篇 |
2007年 | 592篇 |
2006年 | 521篇 |
2005年 | 446篇 |
2004年 | 439篇 |
2003年 | 380篇 |
2002年 | 381篇 |
2001年 | 130篇 |
2000年 | 133篇 |
1999年 | 134篇 |
1998年 | 100篇 |
1997年 | 98篇 |
1996年 | 66篇 |
1995年 | 49篇 |
1994年 | 41篇 |
1993年 | 32篇 |
1992年 | 54篇 |
1991年 | 48篇 |
1990年 | 25篇 |
1989年 | 23篇 |
1988年 | 15篇 |
1987年 | 26篇 |
1986年 | 8篇 |
1985年 | 17篇 |
1984年 | 16篇 |
1983年 | 7篇 |
1979年 | 10篇 |
1977年 | 6篇 |
1974年 | 7篇 |
1970年 | 7篇 |
1968年 | 11篇 |
1967年 | 7篇 |
1966年 | 7篇 |
1964年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
142.
该研究以宽阔水国家级自然保护区野生草本植物为研究对象,依据不同生境类型共选取10个样地进行调查,分析草本植物物种组成、区系特点及物种多样性的变化规律,为保护区草本植物物种多样性研究提供基础资料。结果表明:(1)样地内共有草本植物58科183属277种(含种下分类单位),以菊科(Asteraceae)、唇形科(Lamiaceae)、禾本科(Poaceae)和荨麻科(Urticaceae)为优势科;以凤仙花属(Impatiens)、堇菜属(Viola)、蓼属(Persicaria)和冷水花属(Pilea)为优势属。(2)在分布区类型中,科的热带分布成分最多,这与保护区所处的中亚热带植被环境的特点相吻合,属的温带地理分布比重最大(61.69%),但温带分布属内含种数较少,均以单种属为主,相反热带分布属的种数较多,并且属级在区系性质的分析中和科级相比更为敏感和可靠;由科和属的性质递变来看,热带性与温带性成分相互渗透,有较明显的过渡特征,属级的地理分布反映出保护区草本植物区系属于亚热带向暖温带过渡分布的性质。(3)各样地中草本植物群落组成有较大的差异,不同样地草本植物群落的α多样性指数与丰富度指数的变化格局不完全一致,但总体变化趋势是一致的,均在样地7的草本植物群落中达到峰值;相异性系数和Cody指数变化格局较为一致,总体呈现上升的趋势;样地8中草本植物多样性指数偏低,受人为干扰因素影响较大。 相似文献
143.
Liang Jiangbin Mei Song Qiao Xiangyu Pan Wei Zhao Yan Shi Shaohui Zhai Yaling Wen Haizhao Wu Guoping Jiang Chengyu 《中国科学:生命科学英文版》2021,64(10):1691-1701
Deep vein thrombosis(DVT) is a common complication following traumatic fracture with a 0.5%–1% annual incidence. Low molecular weight heparin(LMWH) is the most commonly used anticoagulation drug for DVT prevention, but treatment with LMWH is invasive. Our aim is to compare the antithrombotic effect of dragon's blood, an oral botanical anticoagulant medicine approved by the Chinese FDA, with LMWH in patients undergoing hip fracture surgery and to explore the molecular mechanisms of anticoagulation treatment. Our study recruited patients and divided them into LMWH and dragon's blood treatment group. Coagulation index tests, Doppler ultrasound and m RNA sequencing were performed before and after anticoagulation therapy. There was no significant difference in postoperative DVT incidence between the two groups(23.1% versus 15.4%,P=0.694). D-dimer(D-D) and fibrinogen degradation product(FDP) showed significant reductions in both groups after anticoagulation treatments. We identified SLC4 A1, PROS1, PRKAR2 B and seven other genes as being differentially expressed during anticoagulation therapy in both groups. Genes correlated with coagulation indexes were also identified. Dragon's blood and LMWH showed similar effects on DVT and produced similar gene expression changes in patients undergoing hip fracture surgery, indicating that dragon's blood is a more convenient antithrombosis medicine(oral) than LMWH(hypodermic injection). 相似文献
144.
Jang Hye Jin Choi Ji Yeon Kim Kangjoon Yong Seung Hyun Kim Yeon Wook Kim Song Yee Kim Eun Young Jung Ji Ye Kang Young Ae Park Moo Suk Kim Young Sam Cho Young-Jae Lee Sang Hoon 《Respiratory research》2021,22(1):1-9
IL-35 subunit EBI3 is up-regulated in pulmonary fibrosis tissues. In this study, we investigated the pathological role of EBI3 in pulmonary fibrosis and dissected the underlying molecular mechanism. Bleomycin-induced pulmonary fibrosis mouse model was established, and samples were performed gene expression analyses through RNAseq, qRT-PCR and Western blot. Wild type and EBI3 knockout mice were exposed to bleomycin to investigate the pathological role of IL-35, via lung function and gene expression analyses. Primary lung epithelial cells were used to dissect the regulatory mechanism of EBI3 on STAT1/STAT4 and STAT3. IL-35 was elevated in both human and mouse with pulmonary fibrosis. EBI3 knockdown aggravated the symptoms of pulmonary fibrosis in mice. EBI3 deficiency enhanced the expressions of fibrotic and extracellular matrix-associated genes. Mechanistically, IL-35 activated STAT1 and STAT4, which in turn suppressed DNA enrichment of STAT3 and inhibited the fibrosis process. IL-35 might be one of the potential therapeutic targets for bleomycin-induced pulmonary fibrosis. 相似文献
145.
Hongtao Cheng Mengyu Hao Bingli Ding Desheng Mei Wenxiang Wang Hui Wang Rijin Zhou Jia Liu Chao Li Qiong Hu 《Plant biotechnology journal》2021,19(1):87-97
CRISPR/Cas‐base editing is an emerging technology that could convert a nucleotide to another type at the target site. In this study, A3A‐PBE system consisting of human A3A cytidine deaminase fused with a Cas9 nickase and uracil glycosylase inhibitor was established and developed in allotetraploid Brassica napus. We designed three sgRNAs to target ALS, RGA and IAA7 genes, respectively. Base‐editing efficiency was demonstrated to be more than 20% for all the three target genes. Target sequencing results revealed that the editing window ranged from C1 to C10 of the PAM sequence. Base‐edited plants of ALS conferred high herbicide resistance, while base‐edited plants of RGA or IAA7 exhibited decreased plant height. All the base editing could be genetically inherited from T0 to T1 generation. Several Indel mutations were confirmed at the target sites for all the three sgRNAs. Furthermore, though no C to T substitution was detected at the most potential off‐target sites, large‐scale SNP variations were determined through whole‐genome sequencing between some base‐edited and wild‐type plants. These results revealed that A3A‐PBE base‐editing system could effectively convert C to T substitution with high‐editing efficiency and broadened editing window in oilseed rape. Mutants for ALS, IAA7 and RGA genes could be potentially applied to confer herbicide resistance for weed control or with better plant architecture suitable for mechanic harvesting. 相似文献
146.
Plant Ecology - Allelopathy of alien invasive plants (AIP) on plant germination performance is essential for their successful invasion. However, the allelopathy of AIP may be reformed or even... 相似文献
147.
148.
Jiao Yan Zhao Dandan Gao Fuhua Hu Xiaoyan Hu Xinxin Li Mei Cui Ying Wei Xiaoqing Xie Ce Zhao Ying Gao Ying 《Journal of physiology and biochemistry》2021,77(1):47-61
Journal of Physiology and Biochemistry - Endothelial injury, which can cause endothelial inflammation and dysfunction, is an important mechanism for the development of atherosclerotic plaque. This... 相似文献
149.
BackgroundWe investigated the relationship between genetic alterations and 18F-FDG PET/CT findings in head and neck squamous cell carcinoma (HNSC).MethodsUsing mRNA-sequences of HNSC samples (480 patients) from the Cancer Genome Atlas (TCGA) portal, gene coexpression networks were constructed via a weighted correlation network analysis (WGCNA) algorithm, and their association with the tumor-to-blood signal ratio on 18F-FDG PET/CT data (21 patients) was explored. An elastic-net regression model was developed to estimate the PET tumor-to-blood ratio from the gene networks and to derive an FDG signature score (FDGSS). The FDGSS was evaluated with regard to clinical variables and general mutational profiles, as well as alterations to oncogenic signaling pathways.FindingsThe FDGSS values differed across clinical stages (p = 0.027), HPV-status (p< 0.001), and molecular subtypes of HNSC (p< 0.001). Multivariate Cox regression demonstrated that FDGSS was an independent predictor for overall (p = 0.019) and progression-free survival (p = 0.024). FDGSS positively correlated with total mutation rate (p = 0.016), aneuploidy (p < 0.001), and somatic copy number alteration scores (p < 0.001). CDKN2A in the cell cycle pathway (q = 0.014) and the TP53 gene in the TP53 pathway (q = 0.005) showed significant differences between high and low FDGSS patients.ConclusionFDGSS based on the gene coexpression network was associated with the mutational landscape of HNSC. 18F-FDG PET/CT is therefore a valuable tool for the in vivo imaging of these cancers, being able to visualize the glucose metabolism of the tumor and allow inferences to be made on the underlying genetic alterations in the tumor. 相似文献
150.