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   3798篇
  免费   64篇
  国内免费   4篇
电工技术   73篇
综合类   8篇
化学工业   579篇
金属工艺   76篇
机械仪表   40篇
建筑科学   141篇
矿业工程   13篇
能源动力   34篇
轻工业   323篇
水利工程   12篇
石油天然气   9篇
无线电   198篇
一般工业技术   361篇
冶金工业   1725篇
原子能技术   17篇
自动化技术   257篇
  2019年   27篇
  2018年   29篇
  2017年   26篇
  2016年   48篇
  2015年   38篇
  2014年   37篇
  2013年   145篇
  2012年   61篇
  2011年   94篇
  2010年   68篇
  2009年   79篇
  2008年   77篇
  2007年   83篇
  2006年   85篇
  2005年   83篇
  2004年   76篇
  2003年   73篇
  2002年   68篇
  2001年   42篇
  2000年   42篇
  1999年   94篇
  1998年   369篇
  1997年   259篇
  1996年   167篇
  1995年   99篇
  1994年   106篇
  1993年   106篇
  1992年   55篇
  1991年   49篇
  1990年   49篇
  1989年   69篇
  1988年   65篇
  1987年   49篇
  1986年   49篇
  1985年   55篇
  1984年   54篇
  1983年   53篇
  1982年   42篇
  1981年   44篇
  1980年   43篇
  1979年   35篇
  1978年   44篇
  1977年   49篇
  1976年   74篇
  1975年   38篇
  1974年   30篇
  1973年   26篇
  1972年   36篇
  1971年   29篇
  1966年   29篇
排序方式: 共有3866条查询结果,搜索用时 819 毫秒
111.
The non-destructive assessment of cracks in concrete is a common task for which non-destructive evaluation solutions have been published. Primarily, these tests have been carried out on artificial cracks that have been created by using notches instead of natural cracks. This study evaluates a procedure designed to create reproducible and controlled cracks in concrete. The procedure is based on using expanding mortar in a series of blind holes. This is done in combination with carefully aligned reinforcement to guide the direction of the crack development. The depth of the crack is also controlled by reinforcement. Crack depth varies statistically in the range of the maximum aggregate size (16 mm) used for concrete.  相似文献   
112.
113.
This study develops a research method of assessing people's satisfaction with housing. Instead of the old approaches which consider in fragmented ways the characteristics of the dwelling, or the neighborhood, or the social environment, the author proposes a systems approach in which various interdependent factors are studied in relation to one another. Using the techniques developed, the relative satisfaction of tenants in public housing projects in certain areas of Canada is identified, analyzed, and discussed.  相似文献   
114.
The UK's Private Finance Initiative market is predicted to rise to over £8 billion a year and there are indications of growing opportunities. PFI creates a long‐term income stream and provides valuable opportunities for portfolio diversification. PFI has evolved at a fast pace and the momentum is set to continue. However, there are major challenges facing construction organisations. These include the lack of PFI experts, longer negotiation periods and tight time schedules to deliver large‐scale schemes, high levels of investment and risks involved and limited knowledge transfer between PFI projects. Concerns over the level of knowledge sharing have prompted the development and evaluation of a Knowledge Transfer Framework that encourages construction organisations to transfer PFI knowledge between projects. It achieves this by building on a questionnaire survey of PFI clients and construction companies, case studies of companies involved in PFI, and research workshops to validate the framework developed.  相似文献   
115.
When We Build Again. A Bournville Village Trust Research Publication. George Allen &; Unwin, Ltd., London, 1941. Pp. xii (16), 138.

Report Relative to Postwar Reconstruction in the City, Prepared by Improvements and Town Planning Committee, published by The Corporation of London, 1944, pp. 66 plus maps and photographs.

The Economic Status of the New York Metropolitan Region in 1944, by The Regional Plan Association, Inc., New York, 1944, xx, 91 pp.  相似文献   
116.
117.
Cancer is a disease exhibiting uncontrollable cell growth and spreading to other parts of the organism. It is a heavy, worldwide burden for mankind with high morbidity and mortality. Therefore, groundbreaking research and innovations are necessary. Research in space under microgravity (µg) conditions is a novel approach with the potential to fight cancer and develop future cancer therapies. Space travel is accompanied by adverse effects on our health, and there is a need to counteract these health problems. On the cellular level, studies have shown that real (r-) and simulated (s-) µg impact survival, apoptosis, proliferation, migration, and adhesion as well as the cytoskeleton, the extracellular matrix, focal adhesion, and growth factors in cancer cells. Moreover, the µg-environment induces in vitro 3D tumor models (multicellular spheroids and organoids) with a high potential for preclinical drug targeting, cancer drug development, and studying the processes of cancer progression and metastasis on a molecular level. This review focuses on the effects of r- and s-µg on different types of cells deriving from thyroid, breast, lung, skin, and prostate cancer, as well as tumors of the gastrointestinal tract. In addition, we summarize the current knowledge of the impact of µg on cancerous stem cells. The information demonstrates that µg has become an important new technology for increasing current knowledge of cancer biology.  相似文献   
118.
加工技术与设备的发展通常会使加工时间缩短.但是新型助剂的应用也可减少加工时间,大大降低成本.随着iFlash系统的应用,漂白温度可降至80℃,活性染料染色后皂洗的时间也大大缩短.因此,织物间歇式染色得到优化,在不增加额外投资的情况下运行更经济.  相似文献   
119.
One of the most common complications during pregnancy is gestational diabetes mellitus (GDM), hyperglycemia that occurs for the first time during pregnancy. The condition is multifactorial, caused by an interaction between genetic, epigenetic, and environmental factors. However, the underlying mechanisms responsible for its pathogenesis remain elusive. Moreover, in contrast to several common metabolic disorders, molecular research in GDM is lagging. It is important to recognize that GDM is still commonly diagnosed during the second trimester of pregnancy using the oral glucose tolerance test (OGGT), at a time when both a fetal and maternal pathophysiology is already present, demonstrating the increased blood glucose levels associated with exacerbated insulin resistance. Therefore, early detection of metabolic changes and associated epigenetic and genetic factors that can lead to an improved prediction of adverse pregnancy outcomes and future cardio-metabolic pathologies in GDM women and their children is imperative. Several genomic and epigenetic approaches have been used to identify the genes, genetic variants, metabolic pathways, and epigenetic modifications involved in GDM to determine its etiology. In this article, we explore these factors as well as how their functional effects may contribute to immediate and future pathologies in women with GDM and their offspring from birth to adulthood. We also discuss how these approaches contribute to the changes in different molecular pathways that contribute to the GDM pathogenesis, with a special focus on the development of insulin resistance.  相似文献   
120.
Brain metastases are the most severe tumorous spread during breast cancer disease. They are associated with a limited quality of life and a very poor overall survival. A subtype of extracellular vesicles, exosomes, are sequestered by all kinds of cells, including tumor cells, and play a role in cell-cell communication. Exosomes contain, among others, microRNAs (miRs). Exosomes can be taken up by other cells in the body, and their active molecules can affect the cellular process in target cells. Tumor-secreted exosomes can affect the integrity of the blood-brain barrier (BBB) and have an impact on brain metastases forming. Serum samples from healthy donors, breast cancer patients with primary tumors, or with brain, bone, or visceral metastases were used to isolate exosomes and exosomal miRs. Exosomes expressed exosomal markers CD63 and CD9, and their amount did not vary significantly between groups, as shown by Western blot and ELISA. The selected 48 miRs were detected using real-time PCR. Area under the receiver-operating characteristic curve (AUC) was used to evaluate the diagnostic accuracy. We identified two miRs with the potential to serve as prognostic markers for brain metastases. Hsa-miR-576-3p was significantly upregulated, and hsa-miR-130a-3p was significantly downregulated in exosomes from breast cancer patients with cerebral metastases with AUC: 0.705 and 0.699, respectively. Furthermore, correlation of miR levels with tumor markers revealed that hsa-miR-340-5p levels were significantly correlated with the percentage of Ki67-positive tumor cells, while hsa-miR-342-3p levels were inversely correlated with tumor staging. Analysis of the expression levels of miRs in serum exosomes from breast cancer patients has the potential to identify new, non-invasive, blood-borne prognostic molecular markers to predict the potential for brain metastasis in breast cancer. Additional functional analyzes and careful validation of the identified markers are required before their potential future diagnostic use.  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