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   1133篇
  免费   34篇
  国内免费   1篇
电工技术   17篇
化学工业   223篇
金属工艺   9篇
机械仪表   12篇
建筑科学   40篇
矿业工程   3篇
能源动力   14篇
轻工业   136篇
水利工程   7篇
石油天然气   2篇
无线电   66篇
一般工业技术   118篇
冶金工业   418篇
原子能技术   6篇
自动化技术   97篇
  2023年   7篇
  2022年   16篇
  2021年   28篇
  2020年   12篇
  2019年   13篇
  2018年   20篇
  2017年   22篇
  2016年   17篇
  2015年   20篇
  2014年   21篇
  2013年   61篇
  2012年   46篇
  2011年   61篇
  2010年   53篇
  2009年   46篇
  2008年   49篇
  2007年   58篇
  2006年   52篇
  2005年   37篇
  2004年   29篇
  2003年   36篇
  2002年   28篇
  2001年   17篇
  2000年   13篇
  1999年   25篇
  1998年   44篇
  1997年   34篇
  1996年   21篇
  1995年   18篇
  1994年   23篇
  1993年   17篇
  1992年   19篇
  1991年   9篇
  1990年   16篇
  1989年   14篇
  1988年   19篇
  1987年   14篇
  1986年   16篇
  1985年   6篇
  1984年   18篇
  1983年   14篇
  1982年   7篇
  1981年   5篇
  1980年   8篇
  1979年   12篇
  1978年   8篇
  1977年   8篇
  1976年   9篇
  1975年   5篇
  1972年   3篇
排序方式: 共有1168条查询结果,搜索用时 15 毫秒
101.
The mammalian intestinal epithelium contains more immune cells than any other tissue, and this is largely because of its constant exposure to pathogens. Macrophages are crucial for maintaining intestinal homeostasis, but they also play a central role in chronic pathologies of the digestive system. We developed a versatile microwell-based intestinal organoid-macrophage co-culture system that enables us to recapitulate features of intestinal inflammation. This microwell-based platform facilitates the controlled positioning of cells in different configurations, continuous in situ monitoring of cell interactions, and high-throughput downstream applications. Using this novel system, we compared the inflammatory response when intestinal organoids were co-cultured with macrophages versus when intestinal organoids were treated with the pro-inflammatory cytokine TNF-α. Furthermore, we demonstrated that the tissue-specific response differs according to the physical distance between the organoids and the macrophages and that the intestinal organoids show an immunomodulatory competence. Our novel microwell-based intestinal organoid model incorporating acellular and cellular components of the immune system can pave the way to unravel unknown mechanisms related to intestinal homeostasis and disorders.  相似文献   
102.
Methylene blue (MB) is a dye used for histology with clinical importance and intercalates into nucleic acids. After MB staining of formalin fixed paraffin embedded (FFPE) muscle invasive bladder cancer (MIBC) and normal urothelium, specific regions could be microdissected. It is not known if MB influences RNA used for gene expression studies. Therefore, we analyzed MIBC using five different RNA isolation methods comparing patient matched FFPE and fresh frozen (FF) tissues pre-stained with or without MB. We demonstrate a positive impact of MB on RNA integrity with FF tissues using real time PCR with no interference of its chemical properties. FFPE tissues showed no improvement of RNA integrity, which we propose is due to formalin induced nucleotide crosslinks. Using direct multiplex RNA hybridization the best genes for normalization of MIBC and control tissues were identified from 34 reference genes. In addition, 5SrRNA and 5.8SrRNA were distinctive reference genes detecting <200 bp fragments important for mRNA analyses. Using these normalized RNAs from MB stained MIBC and applying multiplex RNA hybridization and mRNA sequencing, a minimal gene expression panel precisely identified luminal and basal MIBC tumor subtypes, important for diagnosis, prognosis and chemotherapy response.  相似文献   
103.
Mast cells (MC) are a key effector cell in multiple types of immune responses, including atopic conditions. Allergic diseases have been steadily rising across the globe, creating a growing public health problem. IgE-mediated activation of MCs leads to the release of potent mediators that can have dire clinical consequences. Current therapeutic options to inhibit MC activation and degranulation are limited; thus, a better understanding of the mechanisms that regulate MC effector functions in allergic inflammation are necessary in order to develop effective treatment options with minimal side effects. Several cytokines have been identified that play multifaceted roles in regulating MC activation, including TGFβ, IL-10, and IL-33, and others that appear to serve primarily anti-inflammatory functions, including IL-35 and IL-37. Here, we review the literature examining cytokines that regulate MC-mediated allergic immune responses.  相似文献   
104.
The present study proposed and tested a motivational model of alcohol use in which people are hypothesized to use alcohol to regulate both positive and negative emotions. Two central premises underpin this model: (a) that enhancement and coping motives for alcohol use are proximal determinants of alcohol use and abuse through which the influence of expectancies, emotions, and other individual differences are mediated and (b) that enhancement and coping motives represent phenomenologically distinct behaviors having both unique antecedents and consequences. This model was tested in 2 random samples (1 of adults, 1 of adolescents) using a combination of moderated regression and path analysis corrected for measurement error. Results revealed strong support for the hypothesized model in both samples and indicate the importance of distinguishing psychological motives for alcohol use. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
105.
106.
Parental divorce is associated with problematic offspring adjustment, but the relation may be due to shared genetic or environmental factors. One way to test for these confounds is to study offspring of twins discordant for divorce. The current analyses used this design to separate the mechanisms responsible for the association between parental divorce, experienced either before or after the age of 16, and offspring well-being. The results were consistent with a causal role of divorce in earlier initiation of sexual intercourse and emotional difficulties, in addition to a greater probability of educational problems, depressed mood, and suicidal ideation. In contrast, the increased risk for cohabitation and earlier initiation of drug use was explained by selection factors, including genetic confounds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
107.
This article discusses a unique teaching internship program that has been in place in the Woodruff School of Mechanical Engineering at Georgia Institute of Technology since 1990. The objective of the program is to provide doctoral students who are considering an academic career an opportunity to gain teaching experience under the tutelage of a faculty member. This article summarizes the major findings from student evaluations and from surveys of former student and faculty participants and discusses the apparent need and benefit of such a doctoral teaching intern program. Benefits and drawbacks of participation are discussed from the intern, faculty mentor, and student points of view. Conclusions are drawn about the overall effectiveness of the program and recommendations are made for implementing a successful teaching internship program.  相似文献   
108.
Hydrostatic pressure testing of several large gray iron castings resulted in brittle overload failures. Subsequent failure analysis on two of the failed components revealed casting imperfections associated with the failure origins. In each case, the root cause of failure was related to the casting mold. The first incident involved an imperfection that resulted in a stress concentration that reduced the normally large critical flaw size to the microstructural level. A microstructural gradient adjacent to the fracture of the second casting was the result of an inadequate mold design that allowed for rapid cooling at a thin-walled region of the casting. Material selection was a concern of the manufacturer and was also investigated.  相似文献   
109.
Conducted a multidimensional content analysis of 4 expert counselors' (N. Ackerman, M. Bowen, D. Jackson, and C. Whitaker) approaches to family treatment. Data were from the 1969 Hillcrest Families Series (produced by R. Birdwhistell), films of these experts conducting assessment interviews with the same family. The natural language in these interviews reveal that Ss' behaviors both converged and diverged. Although these Ss did not represent separate theoretical schools, the distinctive features in their sessions were consistent with their theoretical emphases. Across interviews, commonalities included (a) the parents as the most active participants; (b) a focus on the parental subsystem; and (c) similar proportions of certain types of counselor responses (e.g., informative directives). A fair proportion of Ss' messages were indirect (addressed to someone other than the target of the communication). Based on these results and an earlier study by the 1st 2 authors (see record 1985-07308-001) of the same interviews, 2 common change factors in family counseling are proposed: disruption of the existing balance of power among family members and education in the nature and strength of family systems. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
110.
Thin layer chromatography was demonstrated as an effective technique for observing the time course of hydrolysis of a substituted xylan (arabinoxylan) by crude preparations of Cellulomonas. The chromatograms revealed a sequential pattern of appearance of xylooligomers and arabinoxylooligomers, with early appearance of relatively large oligomers and subsequent accumulation of xylobiose and (to a lesser extent) xylose and arabinose. The pattern indicated that the dominant enzymic activity towards arabinoxylan is that of an endoxylanase.  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