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   29594篇
  免费   1310篇
  国内免费   112篇
电工技术   391篇
综合类   229篇
化学工业   5431篇
金属工艺   645篇
机械仪表   626篇
建筑科学   1011篇
矿业工程   98篇
能源动力   961篇
轻工业   4128篇
水利工程   268篇
石油天然气   167篇
武器工业   6篇
无线电   2307篇
一般工业技术   4291篇
冶金工业   6344篇
原子能技术   250篇
自动化技术   3863篇
  2024年   52篇
  2023年   164篇
  2022年   533篇
  2021年   835篇
  2020年   580篇
  2019年   652篇
  2018年   727篇
  2017年   802篇
  2016年   767篇
  2015年   581篇
  2014年   911篇
  2013年   1524篇
  2012年   1326篇
  2011年   1668篇
  2010年   1216篇
  2009年   1275篇
  2008年   1166篇
  2007年   1011篇
  2006年   811篇
  2005年   860篇
  2004年   931篇
  2003年   836篇
  2002年   820篇
  2001年   709篇
  2000年   552篇
  1999年   537篇
  1998年   2064篇
  1997年   1354篇
  1996年   946篇
  1995年   619篇
  1994年   482篇
  1993年   540篇
  1992年   225篇
  1991年   285篇
  1990年   231篇
  1989年   194篇
  1988年   206篇
  1987年   162篇
  1986年   171篇
  1985年   184篇
  1984年   128篇
  1983年   90篇
  1982年   118篇
  1981年   121篇
  1980年   118篇
  1979年   95篇
  1978年   77篇
  1977年   143篇
  1976年   227篇
  1975年   83篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Personal and Ubiquitous Computing - This article presents a study concerning the evaluation of a smart home control system for elderly people with a sample of 10 users in a city in the interior of...  相似文献   
33.
34.
An experimental methodology for inferring brine dissolution rate in monoethylene glycol (MEG) solutions at different temperatures using a webcam combined with a mathematical model is presented. The measurement system is designed to track the RGB (red, green, and blue) colour variations during the dissolution process. A dynamic model augmented with the population balance equation is applied to describe the dissolution process. Moreover, the dissolution rate is consistently related to the temperature and MEG concentration through the driving force based on the Gibbs energy and chemical affinity. The applied low-cost measurement apparatus proved to be a useful resource for tracking the dissolution dynamics in a wide range of undersaturation.  相似文献   
35.
36.

This paper presents a PVS development of relevant results of the theory of rings. The PVS theory includes complete proofs of the three classical isomorphism theorems for rings, and characterizations of principal, prime and maximal ideals. Algebraic concepts and properties are specified and formalized as generally as possible allowing in this manner their application to other algebraic structures. The development provides the required elements to formalize important algebraic theorems. In particular, the paper presents the formalization of the general algebraic-theoretical version of the Chinese remainder theorem (CRT) for the theory of rings, as given in abstract algebra textbooks, proved as a consequence of the first isomorphism theorem. Also, the PVS theory includes a formalization of the number-theoretical version of CRT for the structure of integers, which is the version of CRT found in formalizations. CRT for integers is obtained as a consequence of the general version of CRT for the theory of rings.

  相似文献   
37.
The association between obesity, cancer and cardiovascular disease (CVD) has been demonstrated in animal and epidemiological studies. However, the specific role of visceral obesity on cancer and CVD remains unclear. Visceral adipose tissue (VAT) is a complex and metabolically active tissue, that can produce different adipokines and hormones, responsible for endocrine-metabolic comorbidities. This review explores the potential mechanisms related to VAT that may also be involved in cancer and CVD. In addition, we discuss the shared pharmacological treatments which may reduce the risk of both diseases. This review highlights that chronic inflammation, molecular aspects, metabolic syndrome, secretion of hormones and adiponectin associated to VAT may have synergistic effects and should be further studied in relation to cancer and CVD. Reductions in abdominal and visceral adiposity improve insulin sensitivity, lipid profile and cytokines, which consequently reduce the risk of CVD and some cancers. Several medications have shown to reduce visceral and/or subcutaneous fat. Further research is needed to investigate the pathophysiological mechanisms by which visceral obesity may cause both cancer and CVD. The role of visceral fat in cancer and CVD is an important area to advance. Public health policies to increase public awareness about VAT’s role and ways to manage or prevent it are needed.  相似文献   
38.
The central nervous system (CNS) is the most complex structure in the body, consisting of multiple cell types with distinct morphology and function. Development of the neuronal circuit and its function rely on a continuous crosstalk between neurons and non-neural cells. It has been widely accepted that extracellular vesicles (EVs), mainly exosomes, are effective entities responsible for intercellular CNS communication. They contain membrane and cytoplasmic proteins, lipids, non-coding RNAs, microRNAs and mRNAs. Their cargo modulates gene and protein expression in recipient cells. Several lines of evidence indicate that EVs play a role in modifying signal transduction with subsequent physiological changes in neurogenesis, gliogenesis, synaptogenesis and network circuit formation and activity, as well as synaptic pruning and myelination. Several studies demonstrate that neural and non-neural EVs play an important role in physiological and pathological neurodevelopment. The present review discusses the role of EVs in various neurodevelopmental disorders and the prospects of using EVs as disease biomarkers and therapeutics.  相似文献   
39.
Studies on color preferences are dependent on the topic and the relationships with personal characteristics, particularly personality, but these are seldom studied in one population. Therefore a questionnaire was collected from 1095 Dutch people asking for color preferences about different topics and relating them to personal characteristics. Color preferences regarding different topics show different patterns and significant differences were found between gender, age, education and personality such as being technical, being emotional or being a team player. Also, different colors were mentioned when asked for colors that stimulate to be quiet, energetic, and able to focus or creative. Probably, due to unconsciousness of contexts, many people had no color preference, a result that in the literature seldom is mentioned. Blue was the overall favorite color; however, most males chose for blue (25%) while most females had no color preference (18%). Black was the overall favorite color for clothing, mainly chosen by females (40%), while males primarily chose blue (27%). For building interiors subjects preferred white. For moods, subjects preferred white for being quiet or being able to focus, red for being energetic and had no color preference for being creative. It is concluded that color preferences are dependent upon the topic, and personal characteristics. The findings are important for architects, interior designers, fashion designers and product designers to have a basic idea of preferred colors for different objects by different types of people. © 2013 Wiley Periodicals, Inc. Col Res Appl, 40, 62–71, 2015  相似文献   
40.
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