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   1717篇
  免费   259篇
  国内免费   23篇
电工技术   2篇
综合类   12篇
化学工业   464篇
金属工艺   18篇
机械仪表   15篇
建筑科学   15篇
轻工业   1380篇
水利工程   1篇
石油天然气   2篇
无线电   20篇
一般工业技术   52篇
冶金工业   3篇
原子能技术   4篇
自动化技术   11篇
  2024年   79篇
  2023年   158篇
  2022年   373篇
  2021年   309篇
  2020年   174篇
  2019年   188篇
  2018年   115篇
  2017年   97篇
  2016年   60篇
  2015年   63篇
  2014年   68篇
  2013年   65篇
  2012年   46篇
  2011年   34篇
  2010年   30篇
  2009年   21篇
  2008年   21篇
  2007年   21篇
  2006年   11篇
  2005年   16篇
  2004年   6篇
  2003年   5篇
  2002年   7篇
  2001年   8篇
  2000年   2篇
  1999年   4篇
  1997年   3篇
  1996年   1篇
  1994年   1篇
  1993年   1篇
  1992年   2篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
排序方式: 共有1999条查询结果,搜索用时 15 毫秒
91.
Xylo-oligosaccharides (XOS) is a functional oligosaccharide with prebiotic properties, and could be fermented by gut microbiota. In this study, the modulatory effects of XOS on emotions and behaviours at different dose were investigated based on the mouse model of chronic unpredictable mild stress-induced depression. The result showed that 0.23 and 0.50 g kg−1 doses of XOS significantly increased sucrose preference index and decreased the immobility time in tail suspension and forced swimming tests. Meanwhile, the dose of 0.23 g kg−1 day−1 XOS significantly increased the concentration of neurotransmitters, such as 5-hydroxytryptamine and γ- aminobutyric acid. Furthermore, the analysis of the faecal microbiota with XOS intervention showed a higher relative abundance of Akkermansia, Bifidobacterium and Lactobacillus, fewer Desulfovibrio and the SCFA concentrations increased with XOS prevention treatment. These results suggested that the dietary supplementation XOS could improve chronic stress-induced depressive-like behaviour by modulating neurotransmitters and reverting gut microbiota changes in mice. These findings present XOS as a potential prebiotic targeting to the gut microbiota for mood disorders.  相似文献   
92.
93.
The first objective of this study was to evaluate the dynamics and their potential association with animal performance of the microbiota in both the rumen and colon of dairy cows as they move from a nonlactation to a lactation ration. The second objective was to assess the potential effects on the microbiota of live yeast supplementation. Twenty-one Holstein cows were split in 2 treatments consisting of 1 × 1010 cfu/d of live yeast (LY; n = 10) or no supplementation (control; n = 11) starting 21 d before until 21 d after calving. At 14 d before and 7 and 21 d after calving, samples of rumen and colon digesta were obtained from each cow using an endoscope. Total DNA was extracted and submitted to high-throughput sequencing. Shannon diversity index, in both the rumen and colon, was unaffected by LY; however, in the rumen it was lowest 7 d after calving and returned to precalving values at 21 d in milk, whereas in the colon it was greatest 14 d before calving but decreased after calving. In the rumen, LY supplementation increased the relative abundance (RA) of Bacteroidales (group UCG-001), Lachnospiracea (groups UCG-002 and UCG-006), and Flexilinea 14 d before calving, and increased RA of Streptococcus 21 d after calving compared with control cows. However, changes in the ruminal microbiota were more drastic across days relative to calving than as influenced by the dietary treatment, and the effect of LY in the colon was milder than in the rumen. The ruminal RA of several genera was associated with postcalving DMI, and that of Gastranaerophilales was the only order positively associated with milk yield. Several genera were positively correlated with feed efficiency, with Clostridiales (unclassified) being the only genus negatively associated with feed efficiency. In the colon, Prevotellaceae (group Ga6A1) was the only genus positively associated with feed efficiency. The ruminal RA of Prevotella 7 and Ruminobacter 14 d precalving was negatively correlated with dry matter intake and milk yield postcalving. The RA of Parabacteroides in the colon 14 d before calving was negatively correlated with milk yield, whereas the RA of Eggerthellaceae (unclassified) and Erysipelotrichaceae (groups c and unclassified) were positively correlated with feed efficiency. Interestingly, LY supplementation doubled the RA of Eggerthellaceae (unclassified) in the colon. It is concluded that microbial diversity in the rumen experiences a transient reduction after calving, whereas in the colon, the reduction is maintained at least until 21 d in milk. Most of the effects of LY on rumen microbiota were observed before calving, whereas in the colon, LY effects were more moderate but consistent and independent of the stage of production. The microbial community of the rumen after calving is more associated with feed intake, milk yield, and feed efficiency than that of the colon. However, the colon microbiota before calving is more associated with feed efficiency after calving than that of the rumen.  相似文献   
94.
95.
The human body hosts enormous diversity of microbiota. Recently, the importance of microbial communities to host physiology has been recognised. Evidence is now emerging that the bidirectional communication between the central nervous system and gastrointestinal tract may affect human nerves, cognition and behaviour through the gut-brain axis (GBA). Although the connection between enteropathy and neurological diseases has been found, it now seems intestinal microorganisms represent the direct mediator of psychopathology. The interactions between host neurological function and intestinal microbiota suggested dietary is a possible way to alleviate psychopathological and neurodegenerative diseases. This review discusses the possible effect of intestinal microbiota on the changes of nerves and emotions in human brain. Maintaining healthy diet strategies should be an important part of preventing neurological diseases and psychopathologies caused by systemic metabolic changes. We hope to provide a novel insight for the design of dietary therapies from the perspective of GBA.  相似文献   
96.
97.
A high-fat, Western-style diet is an important predisposing factor for the onset of type 2 diabetes and obesity. It causes changes in gut microbial profile, reduction of microbial diversity, and the impairment of the intestinal barrier, leading to increased serum lipopolysaccharide (endotoxin) levels. Elevated lipopolysaccharide (LPS) induces acetyltransferase P300 both in the nucleus and cytoplasm of liver hepatocytes through the activation of the IRE1-XBP1 pathway in the endoplasmic reticulum stress. In the nucleus, induced P300 acetylates CRTC2 to increase CRTC2 abundance and drives Foxo1 gene expression, resulting in increased expression of the rate-limiting gluconeogenic gene G6pc and Pck1 and abnormal liver glucose production. Furthermore, abnormal cytoplasm-appearing P300 acetylates IRS1 and IRS2 to disrupt insulin signaling, leading to the prevention of nuclear exclusion and degradation of FOXO1 proteins to further exacerbate the expression of G6pc and Pck1 genes and liver glucose production. Inhibition of P300 acetyltransferase activity by chemical inhibitors improved insulin signaling and alleviated hyperglycemia in obese mice. Thus, P300 acetyltransferase activity appears to be a therapeutic target for the treatment of type 2 diabetes and obesity.  相似文献   
98.
99.
目的 探讨小肠神经内分泌肿瘤(NETs)的临床特点、治疗方法及预后.方法 对24例小肠神经内分泌肿瘤患者的临床资料进行回顾性分析.结果 分期情况:T1期7例、T2期4例、T3期4例、T4期6例,另3例无法确定.分级情况:G1级10例,G2级7例,NEC 5例,MANEC 2例.免疫组织化学:Syn、CgA、NSE阳性表达率分别为95%、79%、75%.临床表现:上腹疼痛17例,溃疡出血2例,胆系扩张、梗阻性黄疸、瘙痒5例,恶心呕吐、贫血等3例,类癌综合征1例,无症状1例.治疗:18例十二指肠NETs患者中内镜下切除6例,全身姑息化疗1例,胰十二指肠切除11例,其中术后辅助化疗6例;6例空回肠NETs患者中手术切除3例,肝转移灶介入后再行小肠病灶手术切除1例,对症治疗2例.随访:6例十二指肠NETs内镜下切除者均无病生存,11例十二指肠NETs患者术后1例死于心脏疾病,1例死于肺部感染,2例MANEC患者和未行手术治疗的1例NEC患者存活期较短,分别为13个月、10个月、5个月;6例空回肠NETs患者有2例仍然存活,其余4例出现腹腔、肝内广泛播散,均在2年后死亡.结论 小肠神经内分泌肿瘤缺乏特征性临床症状,内镜有助于该病的早期诊断.尽早手术切除肿瘤可提高患者生存率,病理分期和分级与患者的生存预后密切相关.  相似文献   
100.
The review highlights various aspects of the influence of chaperones on amyloid proteins associated with the development of neurodegenerative diseases and includes studies conducted in our laboratory. Different sections of the article are devoted to the role of chaperones in the pathological transformation of alpha-synuclein and the prion protein. Information about the interaction of the chaperonins GroE and TRiC as well as polymer-based artificial chaperones with amyloidogenic proteins is summarized. Particular attention is paid to the effect of blocking chaperones by misfolded and amyloidogenic proteins. It was noted that the accumulation of functionally inactive chaperones blocked by misfolded proteins might cause the formation of amyloid aggregates and prevent the disassembly of fibrillar structures. Moreover, the blocking of chaperones by various forms of amyloid proteins might lead to pathological changes in the vital activity of cells due to the impaired folding of newly synthesized proteins and their subsequent processing. The final section of the article discusses both the little data on the role of gut microbiota in the propagation of synucleinopathies and prion diseases and the possible involvement of the bacterial chaperone GroE in these processes.  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