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   547篇
  免费   27篇
  574篇
  2023年   5篇
  2022年   15篇
  2021年   17篇
  2020年   13篇
  2019年   13篇
  2018年   16篇
  2017年   14篇
  2016年   22篇
  2015年   31篇
  2014年   37篇
  2013年   44篇
  2012年   68篇
  2011年   60篇
  2010年   23篇
  2009年   30篇
  2008年   34篇
  2007年   23篇
  2006年   24篇
  2005年   23篇
  2004年   22篇
  2003年   12篇
  2002年   14篇
  2000年   2篇
  1998年   1篇
  1997年   3篇
  1996年   1篇
  1994年   1篇
  1987年   3篇
  1984年   1篇
  1972年   1篇
  1971年   1篇
排序方式: 共有574条查询结果,搜索用时 0 毫秒
71.
72.
Sleep and Biological Rhythms - Since sleep is under circadian and homeostatic regulation, the status of regulatory mechanisms can be known from daily activity patterns, including both sleep and...  相似文献   
73.
UDP‐glucose: anthocyanidin 3‐O‐glucosyltransferase (UGT78K6) from Clitoria ternatea catalyzes the transfer of glucose from UDP‐glucose to anthocyanidins such as delphinidin. After the acylation of the 3‐O‐glucosyl residue, the 3′‐ and 5′‐hydroxyl groups of the product are further glucosylated by a glucosyltransferase in the biosynthesis of ternatins, which are anthocyanin pigments. To understand the acceptor‐recognition scheme of UGT78K6, the crystal structure of UGT78K6 and its complex forms with anthocyanidin delphinidin and petunidin, and flavonol kaempferol were determined to resolutions of 1.85 Å, 2.55 Å, 2.70 Å, and 1.75 Å, respectively. The enzyme recognition of unstable anthocyanidin aglycones was initially observed in this structural determination. The anthocyanidin‐ and flavonol‐acceptor binding details are almost identical in each complex structure, although the glucosylation activities against each acceptor were significantly different. The 3‐hydroxyl groups of the acceptor substrates were located at hydrogen‐bonding distances to the Nε2 atom of the His17 catalytic residue, supporting a role for glucosyl transfer to the 3‐hydroxyl groups of anthocyanidins and flavonols. However, the molecular orientations of these three acceptors are different from those of the known flavonoid glycosyltransferases, VvGT1 and UGT78G1. The acceptor substrates in UGT78K6 are reversely bound to its binding site by a 180° rotation about the O1–O3 axis of the flavonoid backbones observed in VvGT1 and UGT78G1; consequently, the 5‐ and 7‐hydroxyl groups are protected from glucosylation. These substrate recognition schemes are useful to understand the unique reaction mechanism of UGT78K6 for the ternatin biosynthesis, and suggest the potential for controlled synthesis of natural pigments.  相似文献   
74.
Psychological stress is an environmental factor considered to be a precipitating factor of inflammatory bowel disease. Interleukin (IL)-18 plays a role in stress-induced aggravation in some diseases. The aim of this study was to establish a model of murine colitis exacerbated by psychological stress and to clarify the role of IL-18 in this model. Male C57Bl/6 mice and IL-18(-/-) mice were used for this study. The mice received dextran sulfate sodium (DSS) for induction of colitis. Some mice were exposed to psychological stress using a communication box. Body weight, colonic length, and histological inflammation were measured for assessment of colitis. Tumor necrosis factor (TNF)-α and IL-18 expression in the colon and IL-18 expression in the adrenal gland were analyzed using real-time PCR. The effect of anti-IL-18 antibody was also investigated. Effects of TNF-α and IL-18 on cytokine expressions were studied using the colonic epithelial cell line LS174T. Induction of psychological stress in DSS-treated wild-type mice significantly exacerbated colitis with enhanced expression of proinflammatory cytokines and IL-18. However, induction of psychological stress in DSS-treated IL-18(-/-) mice did not aggravate colitis compared with that in the IL-18(-/-) group given only DSS treatment. Stress-induced aggravation of colitis was ameliorated significantly by anti-IL-18 antibody treatment. IL-18 did not enhance TNF-α-induced expression of intercellular adhesion molecule-1 or IL-8 in LS174T. We established a model of colitis exacerbated by psychological stress. Psychological stress enhanced IL-18 expression and plays a proinflammatory role in stress-induced aggravation of colitis.  相似文献   
75.
The single nucleotide polymorphism (SNP) rs13438494 in intron 24 of PCLO was significantly associated with bipolar disorder in a meta-analysis of genome-wide association studies. In this study, we performed functional minigene analysis and bioinformatics prediction of splicing regulatory sequences to characterize the deep intronic SNP rs13438494. We constructed minigenes with A and C alleles containing exon 24, intron 24, and exon 25 of PCLO to assess the genetic effect of rs13438494 on splicing. We found that the C allele of rs13438494 reduces the splicing efficiency of the PCLO minigene. In addition, prediction analysis of enhancer/silencer motifs using the Human Splice Finder web tool indicated that rs13438494 induces the abrogation or creation of such binding sites. Our results indicate that rs13438494 alters splicing efficiency by creating or disrupting a splicing motif, which functions by binding of splicing regulatory proteins, and may ultimately result in bipolar disorder in affected people.  相似文献   
76.
We present efficient syntheses of serofendic acids A and B (SA-A and SA-B), novel neuroprotective substances isolated from fetal calf serum. Biological and pharmacological evaluation showed that SA-A and SA-B have potent protective action against glutamate-induced neurotoxicity, but do not interact directly with glutamate receptors. A pharmacokinetic study showed that they have good oral bioavailability in rats. The results indicate that SA-A and SA-B are potential lead compounds for candidate drugs to treat various neurological disorders.  相似文献   
77.
Watanabe  Atsuyuki  So  Matsuo  Mitaka  Hayato  Ishisaka  Yoshiko  Takagi  Hisato  Inokuchi  Ryota  Iwagami  Masao  Kuno  Toshiki 《Mycopathologia》2022,187(2-3):271-289

The recent increase of COVID-19-associated mucormycosis (CAM) has been commanding global attention. However, basic epidemiologic characteristics have not firmly been established. In this systematic review and meta-analysis, we sought to determine the clinical manifestations, potential risk factors, and outcomes of CAM. Observational studies reporting CAM were searched with PubMed and EMBASE databases in January 2022. We collected data on comorbidities and treatment for COVID-19, and performed a one-group meta-analysis on the frequency of orbital exenteration procedure and mortality of CAM using a random-effect model. Fifty-one observational studies, including a total of 2,312 patients with proven CAM, were identified. Among the 51 studies, 37 were conducted in India, 8 in Egypt, and 6 in other countries. The most common comorbidity was diabetes mellitus (82%). While 57% required oxygenation, 77% received systemic corticosteroids. Among CAM, 97% were rhino-orbital-cerebral (ROCM), and 2.7% were pulmonary mucormycosis. Usual presentations were headache (54%), periorbital swelling/pain (53%), facial swelling/pain (43%), ophthalmoplegia (42%), proptosis (41%), and nasal discharge/congestion (36%). Regarding the outcomes, orbital exenteration was performed in 17% (95% CI: 12–21%, I2?=?83%) of the COVID-19-associated ROCM patients. The mortality of CAM was 29% (95% CI; 22–36%, I2?=?92%). In conclusion, this systematic review and meta-analysis indicated that the most prevalent type of CAM was ROCM, and most CAM patients had diabetes mellitus and received systemic glucocorticoids. Clinicians in the endemic areas should have a high index of suspicion for this invasive fungal complication of COVID-19 when a diabetic patient who received high-dose systemic glucocorticoids developed rhino-orbital symptoms.

  相似文献   
78.
The tripeptide Asn-d-Trp-Phe-NH(2) (NdWFamide) is a D-amino acid-containing cardioexcitatory peptide initially isolated from Aplysia. Previously we detected NdWFamide immunoreactivity in the visceral giant cells, the largest neurons in the brain of the terrestrial slug Limax located at the dorsal surface of the visceral ganglia. In the present study, we further analyzed the morphological features of these neurons by an intracellular injection of Lucifer yellow, and found that these neurons extend neurites out of the brain through at least 5 nerve bundles. We then isolated a gene and a cDNA clone potentially encoding a NdWFamide precursor, and investigated expression at the levels of mRNA and protein in Limax. The NdWFamide gene consists of 5 exons spanning at least 17 kb of the genome, and its open reading frame extends over 3 exons. The spatial expression pattern of NdWFamide mRNA was almost identical to that of the NdWFamide peptide, with some minor discrepancies in between. Although the most remarkable expression was evident in the visceral giant cells, we also found the expression of NdWFamide mRNA and peptide in the cerebral and pedal ganglia. These results suggest the involvement of NdWFamide in the regulation of a broad area of the slug's body.  相似文献   
79.
Several Zn(II) complexes (2a-e) of 1-arylmethyl-2,5-dihydro-4-hydroxy-5-oxo-1H-pyrrole-3-carboxylates (1a-e), known drug candidates for diabetic complications, were synthesized and proved to have in vitro insulin-mimetic activities, suggesting that these complexes are potential chemotherapeutics that are effective against both diabetes and diabetic complications.  相似文献   
80.
The crystal structure of subunit F of vacuole-type ATPase/synthase (prokaryotic V-ATPase) was determined to of 2.2 A resolution. The subunit reveals unexpected structural similarity to the response regulator proteins that include the Escherichia coli chemotaxis response regulator CheY. The structure was successfully placed into the low-resolution EM structure of the prokaryotic holo-V-ATPase at a location indicated by the results of crosslinking experiments. The crystal structure, together with the single-molecule analysis using fluorescence resonance energy transfer, showed that the subunit F exhibits two conformations, a 'retracted' form in the absence and an 'extended' form in the presence of ATP. Our results postulated that the subunit F is a regulatory subunit in the V-ATPase.  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