全文获取类型
收费全文 | 10396篇 |
免费 | 945篇 |
国内免费 | 1578篇 |
专业分类
12919篇 |
出版年
2024年 | 49篇 |
2023年 | 173篇 |
2022年 | 346篇 |
2021年 | 577篇 |
2020年 | 409篇 |
2019年 | 524篇 |
2018年 | 506篇 |
2017年 | 360篇 |
2016年 | 450篇 |
2015年 | 764篇 |
2014年 | 833篇 |
2013年 | 822篇 |
2012年 | 1048篇 |
2011年 | 947篇 |
2010年 | 591篇 |
2009年 | 547篇 |
2008年 | 615篇 |
2007年 | 557篇 |
2006年 | 468篇 |
2005年 | 412篇 |
2004年 | 368篇 |
2003年 | 323篇 |
2002年 | 244篇 |
2001年 | 126篇 |
2000年 | 135篇 |
1999年 | 117篇 |
1998年 | 83篇 |
1997年 | 98篇 |
1996年 | 70篇 |
1995年 | 62篇 |
1994年 | 48篇 |
1993年 | 32篇 |
1992年 | 35篇 |
1991年 | 16篇 |
1990年 | 20篇 |
1989年 | 11篇 |
1988年 | 20篇 |
1987年 | 16篇 |
1985年 | 14篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 16篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1976年 | 4篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1972年 | 5篇 |
1950年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Cheng-Jun He Cheng Peng Xiao-Fang Xie Li Guo Qin-Mei Zhou Xiao-Hong Li Ou Dai Zhao Geng Yi-Ping Guo 《Phytochemistry letters》2013,6(2):299-301
Two new dianthramide glucosides, N-(2′-β-d-glucopyranosyl-5′-hydroxysalicyl)-4-hydroxy-3-methoxyanthranilic acid methyl ester (1) and N-(2′-β-d-glucopyranosyl-5′-hydroxysalicyl)-4-hydroxyanthranilic acid methyl ester (2), together with five known glycosides, were isolated from the lateral roots of Aconitum carmichaelii. Their structures were elucidated by spectroscopic analyses. In the in vitro assays, compounds 1 and 2 showed activity against pentobarbital sodium-induced cardiomyocytes damage by recovering beating rhythm and increasing the cell viability. 相似文献
92.
Cindy Q. Tang Mei-Hua Zhao Xiao-Shuang Li Masahiko Ohsawa Xiao-Kun Ou 《Ecological Research》2010,25(1):149-161
Since 1985, originally forested mountainous areas of China have been allowed to return to their natural state after years
of exploitation including agriculture, development, and logging. The reforms began earlier in less accessible locations, so
that today the successional process is more advanced there. The vegetation in Luquan, Qiongzhusi, and Xishan near Kunming,
central Yunnan, exhibits, in a limited area, a range of stages of plant succession that are widely encountered throughout
the broader region, and thus affords a special opportunity for a comprehensive study. We analyzed the successional sequence
of these various plant communities. They ranged from pioneer coniferous and/or pioneer deciduous broad-leaved stands to pre-mature
semi-humid evergreen broad-leaved stands, through mixed coniferous and broad-leaved or mixed deciduous and evergreen broad-leaved
stands. The succession proceeded from pioneer coniferous Pinus and Keteleeria, and deciduous Platycarya and Alnus, to late-successional evergreen broad-leaved Cyclobalanopsis and Castanopsis. Two regeneration types of woody species in either the early successional (15–50 years), the mid-successional (40–80 years),
or the late-successional (80–180 years) stage were classified. Relatively high species diversity was found in the seral phase
at the three study sites. The late-successional stage was commonest where human disturbance was least evident. Poor soil chemical
properties under pioneer Pinus were seen as a limitation to plant growth, while the abundance of Alnus at the early stage led to an improved level of organic matter and nitrogen. 相似文献
93.
Ultrathin Co3O4 Layers with Large Contact Area on Carbon Fibers as High‐Performance Electrode for Flexible Zinc–Air Battery Integrated with Flexible Display 下载免费PDF全文
Xu Chen Bin Liu Cheng Zhong Zhi Liu Jie Liu Lu Ma Yida Deng Xiaopeng Han Tianpin Wu Wenbin Hu Jun Lu 《Liver Transplantation》2017,7(18)
A facile and binder‐free method is developed for the in situ and horizontal growth of ultrathin mesoporous Co3O4 layers on the surface of carbon fibers in the carbon cloth (ultrathin Co3O4/CC) as high‐performance air electrode for the flexible Zn–air battery. In particular, the ultrathin Co3O4 layers have a maximum contact area on the conductive support, facilitating the rapid electron transport and preventing the aggregation of ultrathin layers. The ultrathin feature of Co3O4 layers is characterized by the transmission electron microscopy, Raman spectra, and X‐ray absorption fine structure spectroscopy. Benefiting from the high utilization degree of active materials and rapid charge transport, the mass activity for oxygen reduction and evolution reactions of the ultrathin Co3O4/CC electrode is more than 10 times higher than that of the carbon cloth loaded with commercial Co3O4 nanoparticles. Compared to the commercial Co3O4/CC electrode, the flexible Zn–air battery using ultrathin Co3O4/CC electrode exhibits excellent rechargeable performance and high mechanical stability. Furthermore, the flexible Zn–air battery is integrated with a flexible display unit. The whole integrated device can operate without obvious performance degradation under serious deformation and even during the cutting process, which makes it highly promising for wearable and roll‐up optoelectronics. 相似文献
94.
小麦叶片β-1,3-葡聚糖酶的诱导、纯化与抗菌活性 总被引:7,自引:0,他引:7
三个小麦品种331、抗倒680和鲁麦23经氯化汞、水杨酸或核黄素处理后,叶片中的β-1,3-葡聚糖酶活性均有不同程度的升高.氯化汞处理24h对品种331该酶活性的诱导作用最强.因此取用氯化汞处理24 h的331小麦叶片研磨得到粗酶液.将粗酶液经硫酸铵分级沉淀、Phenyl-Sepharose Fast Flow疏水层析、DEAE-Sepharose Fast Flow阴离子交换层析和Sephacryl S-100分子筛层析,得到了SDS-PAGE凝胶电泳谱带单一的β-1,3-葡聚糖酶样品.经SDS-PAGE(12%)和凝胶过滤层析,测得其分子量约为52.0~53.6 kD.抗菌试验测定显示,纯化的β-1,3-葡聚糖酶对供试的4种病原真菌的生长、孢子萌发或芽管伸长都有一定程度的抑制作用. 相似文献
95.
肿瘤干细胞及其耐药机制 总被引:3,自引:0,他引:3
肿瘤干细胞是存在于造血系统肿瘤和一些实体瘤中具有干细胞特性的细胞。肿瘤干细胞假说认为,经药物治疗后肿瘤复发和转移与肿瘤干细胞残存有密切关系。其原因可能是肿瘤干细胞高表达ABC转运蛋白和Bcl-2抗凋亡蛋白,同时其本身又具有一些干细胞特性。对肿瘤干细胞耐药机制的研究,将有助于发现新的肿瘤治疗靶点和更好的抗癌策略。 相似文献
96.
97.
98.
MENG Yan ZHAO ChunYan ZHANG XueXin ZHAO HuaShan GUO LiRong Lü Bin ZHAO XueJian& YANG BaoXue Department of Pathophysiology School of Basic Medicine Jilin University Changchun China Department of Physiology Department of Medicine University of California San Francisco CA USA 《中国科学:生命科学英文版》2009,52(5):474-478
99.
氧化固醇结合蛋白结构、功能与应用 总被引:1,自引:0,他引:1
氧化固醇结合蛋白(oxysterol binding protein,OSBP)是存在于真核细胞内的一类参与脂质代谢的非囊泡运输蛋白质,在哺乳动物中被称为氧化固醇结合蛋白相关蛋白质(oxysterol binding protein-related proteins,ORPs),而在酵母中被称为氧化固醇结合蛋白同源物质(oxysterol-binding protein homologues,OSH)。近年来人们对氧化固醇结合蛋白的研究不断深入,特别是对其同源蛋白质(例如,ORP5/8、Osh3/4、ORP4L等)的结构功能差异和其在信号转导中的作用的相关研究,以及在生物医药方面的应用更成为了本领域的热点。本文综述了关于OSBP及其同源蛋白质结构和功能的相关研究,指出了该领域存在的一些关键问题。与此同时,对OSH和ORPs在细胞内的膜接触位点(membrane contact sites,MCS)进行对比,以及对今后OSBP的研究方向做了展望。 相似文献
100.
Expression of mRNA for the t-complex polypeptide-1, a subunit of chaperonin CCT, is upregulated in association with increased cold hardiness in Delia antiqua 下载免费PDF全文
Kayukawa T Chen B Miyazaki S Itoyama K Shinoda T Ishikawa Y 《Cell stress & chaperones》2005,10(3):204-210
Summer-diapause and winter-diapause pupae of the onion maggot, Delia antiqua (Diptera: Anthomyiidae), were significantly more cold hardy than nondiapause, prediapause, and postdiapause pupae. Moreover, cold acclimation of nondiapause pupae conferred strong cold hardiness comparable with that of diapause pupae. Differential display analysis revealed that the expression of a gene encoding TCP-1 (the t-complex polypeptide-1), a subunit of chaperonin CCT, in D antiqua (DaTCP-1) is upregulated in the pupae that express enhanced cold hardiness. Quantitative real-time polymerase chain reaction analyses showed that the levels of DaTCP-1 messenger RNA in pupal tissues, brain, and midgut in particular, are highly correlated with the cold hardiness of the pupae. These findings suggest that the upregulation of DaTCP-1 expression is related to enhanced cold hardiness in D antiqua. The upregulation of CCT in response to low temperature in an organism other than the yeast is newly reported. 相似文献