首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   14054篇
  免费   1260篇
  国内免费   1542篇
  2024年   22篇
  2023年   170篇
  2022年   225篇
  2021年   664篇
  2020年   539篇
  2019年   622篇
  2018年   571篇
  2017年   448篇
  2016年   617篇
  2015年   945篇
  2014年   1095篇
  2013年   1145篇
  2012年   1451篇
  2011年   1268篇
  2010年   791篇
  2009年   725篇
  2008年   825篇
  2007年   721篇
  2006年   674篇
  2005年   519篇
  2004年   443篇
  2003年   390篇
  2002年   308篇
  2001年   206篇
  2000年   195篇
  1999年   176篇
  1998年   134篇
  1997年   112篇
  1996年   91篇
  1995年   93篇
  1994年   103篇
  1993年   62篇
  1992年   76篇
  1991年   69篇
  1990年   44篇
  1989年   46篇
  1988年   30篇
  1987年   31篇
  1986年   27篇
  1985年   32篇
  1984年   16篇
  1983年   11篇
  1982年   11篇
  1981年   13篇
  1980年   9篇
  1978年   10篇
  1976年   10篇
  1975年   11篇
  1973年   8篇
  1970年   7篇
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
1.
2.
Diabetic nephropathy (DN) as a global health concern is closely related to inflammation and oxidation. Isoliquiritigenin (ISL), a natural flavonoid compound, has been demonstrated to inhibit inflammation in macrophages. Herein, we investigated the effect of ISL in protecting against the injury in STZ-induced type 1 DN and in high glucose-induced NRK-52E cells. In this study, it was revealed that the administration of ISL not only ameliorated renal fibrosis and apoptosis, but also induced the deterioration of renal function in diabetic mice. Mediated by MAPKs and Nrf-2 signaling pathways, respectively, upstream inflammatory response and oxidative stress were neutralized by ISL in vitro and in vivo. Moreover, as further revealed by the results of molecular docking, sirtuin 1 (SIRT1) binds to ISL directly, and the involvement of SIRT1 in ISL-mediated renoprotective effects was confirmed by studies using in vitro models of SIRT1 overexpression and knockdown. In summary, by reducing inflammation and oxidative stress, ISL has a significant pharmacological effect on the deterioration of DN. The benefits of ISL are associated with the direct binding to SIRT1, the inhibition of MAPK activation, and the induction of Nrf-2 signaling, suggesting the potential of ISL for DN treatment.Subject terms: Pharmacology, Molecular biology  相似文献   
3.
A tip-focused Ca^2+ gradient is tightly coupled to polarized pollen tube growth, and tip-localized influxes of extracellular Ca^2+ are required for this process. However the molecular identity and regulation of the potential Ca^2+ channels remains elusive. The present study has implicated CNGC18 (cyclic nucleotide-gated channel 18) in polarized pollen tube growth, because its overexpression induced wider and shorter pollen tubes. Moreover, CNGC18 overexpression induced depolarization of pollen tube growth was suppressed by lower extracellular calcium ([Ca^2+]ex). CNGC18-yellow fluorescence protein (YFP) was preferentially localized to the apparent post-Golgi vesicles and the plasma membrane (PM) in the apex of pollen tubes. The PM localization was affected by tip-localized ROP1 signaling. Expression of wild type ROP1 or an active form of ROP1 enhanced CNGC18-YFP localization to the apical region of the PM, whereas expression of RopGAP1 (a ROP1 deactivator) blocked the PM localization. These results support a role for PM-Iocalized CNGC18 in the regulation of polarized pollen tube growth through its potential function in the modulation of calcium influxes.  相似文献   
4.
5.
6.
Interplant communication has been widely demonstrated in plants, especially in herbaceous plants. In this study, mechanical damage was shown to affect the levels of pyrochatechol, chlorogenic acid, gallic acid and p-hydroxyl benzoic acid in poplar (Populus simonii × P. pyramidalis ‘Opera 8277’) cuttings, indicating the activation of defense response. In neighboring intact cuttings, the levels of those phenolics also varied when compared to the control, suggesting the interplant communication between poplar cuttings. Three volatiles, methyl jasmonate, methyl salicylate and benzothiazole, were detected in volatiles emitted from mechanically damaged poplar cuttings. All of them can induce changes in the levels of four phenolics. Therefore, they could act as airborne signals between P. simonii × P. pyramidalis ‘Opera 8277’ cuttings. The different change patterns of phenolic contents induced by different volatiles imply that the defense response activated in neighboring plants may be regulated by multiple signaling pathways. The results also suggest that the entire defense response of plants involves a variety of airborne signals in wound-induced volatiles.  相似文献   
7.
Bone and tooth, fundamental parts of the craniofacial skeleton, are anatomically and developmentally interconnected structures. Notably, pathological processes in these tissues underwent together and progressed in multilevels. Extracellular vesicles (EVs) are cell-released small organelles and transfer proteins and genetic information into cells and tissues. Although EVs have been identified in bone and tooth, particularly EVs have been identified in the bone formation and resorption, the concrete roles of EVs in bone and tooth development and diseases remain elusive. As such, we review the recent progress of EVs in bone and tooth to highlight the novel findings of EVs in cellular communication, tissue homeostasis, and interventions. This will enhance our comprehension on the skeletal biology and shed new light on the modulation of skeletal disorders and the potential of genetic treatment.  相似文献   
8.
9.
slyD encodes a 196 amino acid polypeptide that is a member of the FKBP family of cis–trans peptidyl–prolyl isomerases (PPIases). slyD mutations affect plaque formation by the phage φX174 by blocking the action of the phage lysis protein E. Here we describe the selection of a set of spontaneous slyD mutations conferring resistance to the expression of gene E from a plasmid. These mutations occur disproportionately in residues of SlyD that, based on the structure of the prototype mammalian FKBP12, make ligand contacts with immunosuppressing drug molecules or are conserved in other FKBP proteins. A wide variation in the plating efficiency of φX174 on these E  R strains is observed, relative to the parental, indicating that these alleles differ widely in residual SlyD activity. Moreover, it is found that slyD mutations cause significant growth rate defects in Escherichia coli B and C backgrounds. Finally, overexpression of slyD causes filamentation of the host. Thus, among the FKBP genes found in organisms across the evolutionary spectrum, slyD is unique in having three distinct drug-independent phenotypes.  相似文献   
10.
Abstract Morphological features of mature larvae of Petelia rivulosa (Butler), Exangerona prattiaria (Leech) and Culcula panterinaria (Bremer & Grey) of Ennominae are described and illustrated. All specimens examined are deposited in the Insect Collection of Department of Forest Resources Protection, Kangwon National University, Korea.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号