全文获取类型
收费全文 | 19414篇 |
免费 | 1435篇 |
国内免费 | 1344篇 |
专业分类
22193篇 |
出版年
2024年 | 52篇 |
2023年 | 289篇 |
2022年 | 630篇 |
2021年 | 1063篇 |
2020年 | 710篇 |
2019年 | 890篇 |
2018年 | 801篇 |
2017年 | 616篇 |
2016年 | 882篇 |
2015年 | 1254篇 |
2014年 | 1473篇 |
2013年 | 1510篇 |
2012年 | 1756篇 |
2011年 | 1532篇 |
2010年 | 952篇 |
2009年 | 815篇 |
2008年 | 945篇 |
2007年 | 765篇 |
2006年 | 727篇 |
2005年 | 573篇 |
2004年 | 526篇 |
2003年 | 470篇 |
2002年 | 407篇 |
2001年 | 372篇 |
2000年 | 341篇 |
1999年 | 312篇 |
1998年 | 204篇 |
1997年 | 188篇 |
1996年 | 174篇 |
1995年 | 152篇 |
1994年 | 115篇 |
1993年 | 105篇 |
1992年 | 132篇 |
1991年 | 110篇 |
1990年 | 96篇 |
1989年 | 58篇 |
1988年 | 46篇 |
1987年 | 49篇 |
1986年 | 25篇 |
1985年 | 26篇 |
1984年 | 16篇 |
1983年 | 20篇 |
1982年 | 4篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Yihao Yang Ziyan Shen Youguang Li Chenda Xu Han Xia Hao Zhuang Shengyuan Sun Min Guo Changjie Yan 《植物学报(英文版)》2022,64(10):1860-1865
Rice eating and cooking quality(ECQ) is a major concern of breeders and consumers, determining market competitiveness worldwide. Rice grain protein content(GPC) is negatively related to ECQ,making it possible to improve ECQ by manipulating GPC. However, GPC is genetically complex and sensitive to environmental conditions; therefore, little progress has been made in traditional breeding for ECQ. Here, we report that CRISPR/Cas9-mediated knockout of genes encoding the grain storage protein gluteli... 相似文献
62.
Jiantong Liu Xinyu Wang Lin Liu Xuefeng Wu Zhichao Xia Qingxue Guo 《Ecology and evolution》2022,12(7)
Deciduous and evergreen trees differ in their responses to drought and nitrogen (N) demand. Whether or not these functional types affect the role of the bacterial community in the N cycle during drought remains uncertain. Two deciduous tree species (Alnus cremastogyne, an N2‐fixing species, and Liquidambar formosana) and two evergreen trees (Cunninghamia lanceolata and Pinus massoniana) were used to assess factors in controlling rhizosphere soil bacterial community and N cycling functions. Photosynthetic rates and biomass production of plants, 16S rRNA sequencing and N‐cycling‐related genes of rhizosphere soil were measured. The relative abundance of the phyla Actinobacteria and Firmicutes was higher, and that of Proteobacteria, Acidobacteria, and Gemmatimondaetes was lower in rhizosphere soil of deciduous trees than that of evergreen. Beta‐diversity of bacterial community also significantly differed between the two types of trees. Deciduous trees showed significantly higher net photosynthetic rates and biomass production than evergreen species both at well water condition and short‐term drought. Root biomass was the most important factor in driving soil bacterial community and N‐cycling functions than total biomass and aboveground biomass. Furthermore, 44 bacteria genera with a decreasing response and 46 taxa showed an increased response along the root biomass gradient. Regarding N‐cycle‐related functional genes, copy numbers of ammonia‐oxidizing bacteria (AOB) and autotrophic ammonia‐oxidizing archaea (AOA), N2 fixation gene (nifH), and denitrification genes (nirK, nirS) were significantly higher in the soil of deciduous trees than in that of the evergreen. Structural equation models explained 50.2%, 47.6%, 48.6%, 49.4%, and 37.3% of the variability in copy numbers of nifH, AOB, AOA, nirK, and nirS, respectively, and revealed that root biomass had significant positive effects on copy numbers of all N‐cycle functional genes. In conclusion, root biomass played key roles in affecting bacterial community structure and soil N cycling. Our findings have important implications for our understanding of plants control over bacterial community and N‐cycling function in artificial forest ecosystems. 相似文献
63.
Hong-Guang Zhang Bin Wang Yong Yang Xuan Liu Junjie Wang Ning Xin Shifeng Li Ying Miao Qiuyu Wu Tingting Guo Yukang Yuan Yibo Zuo Xiangjie Chen Tengfei Ren Chunsheng Dong Jun Wang Hang Ruan Miao Sun Xingshun Xu Hui Zheng 《Cell research》2022,32(10):897
Depression is a serious public-health issue. Recent reports have suggested higher susceptibility to viral infections in depressive patients. However, how depression affects antiviral innate immune signaling remains unknown. Here, we revealed a reduction in expression of Abelson helper integration site 1 (AHI1) in the peripheral blood mononuclear cells (PBMCs) and macrophages from the patients with major depressive disorder (MDD), which leads to attenuated antiviral immune response. We found that depression-related arginine vasopressin (AVP) induces reduction of AHI1 in macrophages. Further studies demonstrated that AHI1 is a critical stabilizer of basal type-I-interferon (IFN-I) signaling. Mechanistically, AHI1 recruits OTUD1 to deubiquitinate and stabilize Tyk2, while AHI1 reduction downregulates Tyk2 and IFN-I signaling activity in macrophages from both MDD patients and depression model mice. Interestingly, we identified a clinical analgesic meptazinol that effectively stimulates AHI1 expression, thus enhancing IFN-I antiviral defense in depression model mice. Our study promotes the understanding of the signaling mechanisms of depression-mediated antiviral immune dysfunction, and reveals meptazinol as an enhancer of antiviral innate immunity in depressive patients.Subject terms: Innate immunity, Ubiquitylation, Cell signalling 相似文献
64.
HIV相关性口腔念珠菌RAPD多态性分析 总被引:2,自引:0,他引:2
运用RAPD技术对60株分离自HIV感染者口腔的念珠菌进行分析, 其中P2随机引物扩增条带数量0~5条, 大小300 bp~2 kb, 白色念珠菌以300 bp、400 bp和600 bp 3个主条带为主, 非白色念珠菌也存在类似条带。采用SPSS13.0聚类分析, 分为5个基因群, 14个基因型, 白色念珠菌主要为B群。其中P385和P403对5-氟孢嘧啶耐药, 聚为C1基因型(欧氏距离平方为0.115), P321和P522对两性霉素B耐药, 聚为D1基因型(欧氏距离平方为0.221)。表明HIV感染者口腔来源的念珠菌存在丰富的基因多态性, RAPD技术对于白色念珠菌的基因型鉴定具有重要意义; 念珠菌不同种间具有相对特征性的条带, 同种不同株间存在相似的条带特征; 某些条带特征可能与念珠菌的耐药性相关。 相似文献
65.
Ruijun Liu Ruili Liu Zhiyi Guo Jianghao Ren Jia Huang Qingquan Luo Qiang Tan 《Cell death & disease》2022,13(8)
In view of the important roles played by Kinetochore proteins in mitosis, we believed that they may contribute to the development and progression of human cancers, which has been reported recently elsewhere. Kinetochore-associated 1 (KNTC1) participates in the segregation of sister chromatids during mitosis, the effects of which on non-small-cell lung cancer (NSCLC) remain unclear. Here, we sought to identify the biological significance of KNTC1 in NSCLC. KNTC1 protein expression in NSCLC tissues was investigated by immunohistochemistry. Lentivirus delivered short hairpin RNA (shRNA) was utilized to establish KNTC1 silence NSCLC cell lines. The effects of KNTC1 depletion on NSCLC cell proliferation, migration, apoptosis, and tumor formation were analyzed by MTT assay, wound-healing assay, transwell assay, flow cytometry assay, and in nude mouse models in vivo. After KNTC1 reduction, NSCLC cell viability, proliferation, migration, and invasion were restrained. A xenograft tumor model was also provided to demonstrate the inhibited tumorigenesis in NSCLC. In addition, the downstream mechanism analysis indicated that KNTC1 depletion was positively associated with PSMB8. The findings of the present study suggested that KNTC1 may have a pivotal role in mediating NSCLC progression and may act as a novel therapeutic target for NSCLC.Subject terms: Non-small-cell lung cancer, Cell migration 相似文献
66.
67.
68.
Ennian Li Kai Wang Bei Zhang Siqi Guo Senhao Xiao Qi Pan Xiaowan Wang Weiying Chen Yunshan Wu Hesong Xu Xiangqian Kong Cheng Luo Shijie Chen Bo Liu 《Journal of enzyme inhibition and medicinal chemistry》2022,37(1):1537
The DNA methyltransferases (DNMTs) were found in mammals to maintain DNA methylation. Among them, DNMT1 was the first identified, and it is an attractive target for tumour chemotherapy. DC_05 and DC_517 have been reported in our previous work, which is non-nucleoside DNMT1 inhibitor with low micromolar IC50 values and significant selectivity towards other S-adenosyl-L-methionine (SAM)-dependent protein methyltransferases. In this study, through a process of similarity-based analog searching, a series of DNMT1 inhibitors were designed, synthesized, and evaluated as anticancer agents. SAR studies were conducted based on enzymatic assays. And most of the compounds showed strong inhibitory activity on human DNMT1, especially WK-23 displayed a good inhibitory effect on human DNMT1 with an IC50 value of 5.0 µM. Importantly, the pharmacokinetic (PK) profile of WK-23 was obtained with quite satisfying oral bioavailability and elimination half-life. Taken together, WK-23 is worth developing as DNMT1-selective therapy for the treatment of malignant tumour. 相似文献
69.
羊草草原枯枝落叶分解的研究——主要优势植物的分解速率和损失率 总被引:15,自引:2,他引:13
分解速率和损失率从不同侧面反映了枯枝落叶分解动态,羊草草原主要优势植物,羊草(Leymus chinensis),拂子茅(Calamagrostis epigejos),减蓬(Suaeda glauca),碱茅(Puccinellia tenuiflora),五脉山黎豆(Lathyrus quinqueneruivs),碱蒿(Artemisia anethifolia)分解速率的季节变化动态近似倒“V”字型,损失率的季节变化呈S型,反了枯枝落叶的失重情况,枯枝落叶的化学组成成分是造成不同种植物间分解差异的主要原因,特别是C/N比与分解快慢有密切关系,分解初期,枯枝落叶的损失符合指数衰减模型,枯枝落叶损失95%所需时间,羊草群落约为8.8a,杂类草群落约为9.7a,碱茅群落约为7.1a,碱蓬群落约为4.7a。 相似文献
70.
本文旨在探讨线粒体ATP敏感钾(mitochondrial ATP-sensitive K+,MitoKATP)通道对大鼠肺动脉平滑肌细胞低氧诱导因子-1α(hypoxia inducible factor-1α,HIF-1α)表达和细胞增殖的影响。原代培养大鼠肺动脉平滑肌细胞,分为常氧对照组、常氧+diazoxide(MitoKATP通道的选择性开放剂)组、常氧+5-hydroxydecanoate(5-HD,MitoKATP通道的选择性阻断剂)组、低氧对照组、低氧+diazoxide组、低氧+5-HD组,共6组,分别应用罗丹明123荧光技术检测各组大鼠肺动脉平滑肌细胞的线粒体膜电位,免疫组化检测HIF-1α的表达及酶联免疫检测仪检测细胞增殖的变化。结果显示,常氧+ diazoxide组与常氧对照组比较,罗丹明123荧光、HIF-1α表达及细胞增殖明显增强(P〈0.05);低氧+diazoxide组与低氧对照组比较,罗丹明123荧光、HIF-1α表达及细胞增殖明显增强(P〈0.05):常氧+5-HD组与常氧对照组比较,罗丹明123荧光、HIF-1α表达、细胞增殖没有明显变化(P〉0.05);但低氧+5-HD组与低氧对照组比较,罗丹明123荧光明显减弱、HIF-1α表达及细胞增殖有所减弱(P〈0.05)。结果提示:MitoKATP通道的开放能引起大鼠肺动脉平滑肌细胞线粒体膜去极化,并可以促进HIF-1α的表达及细胞增殖。 相似文献