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   2961篇
  免费   194篇
电工技术   23篇
综合类   29篇
化学工业   1049篇
金属工艺   30篇
机械仪表   49篇
建筑科学   102篇
矿业工程   16篇
能源动力   62篇
轻工业   436篇
水利工程   42篇
石油天然气   6篇
无线电   129篇
一般工业技术   459篇
冶金工业   366篇
原子能技术   11篇
自动化技术   346篇
  2024年   15篇
  2023年   30篇
  2022年   177篇
  2021年   183篇
  2020年   97篇
  2019年   88篇
  2018年   97篇
  2017年   98篇
  2016年   115篇
  2015年   98篇
  2014年   128篇
  2013年   197篇
  2012年   153篇
  2011年   229篇
  2010年   133篇
  2009年   136篇
  2008年   143篇
  2007年   109篇
  2006年   83篇
  2005年   57篇
  2004年   67篇
  2003年   67篇
  2002年   50篇
  2001年   38篇
  2000年   39篇
  1999年   38篇
  1998年   96篇
  1997年   45篇
  1996年   43篇
  1995年   29篇
  1994年   36篇
  1993年   21篇
  1992年   12篇
  1991年   11篇
  1990年   10篇
  1988年   7篇
  1987年   12篇
  1986年   7篇
  1985年   10篇
  1983年   10篇
  1981年   11篇
  1980年   9篇
  1979年   13篇
  1978年   9篇
  1977年   11篇
  1976年   11篇
  1975年   9篇
  1974年   7篇
  1973年   11篇
  1967年   8篇
排序方式: 共有3155条查询结果,搜索用时 15 毫秒
1.
New requirements of growing computer networks and information systems have an influence on extended client/server models with increased functionality. This forms the basis for service management in distributed systems which is realized by a service trading concept. This paper studies the requirements derived from the Open Distributed Processing (ODP) Reference Model in order to consider an open service market. Furthermore, it examines management possibilities for describing the service trading scenario. Because of similar architectures and properties ODP services, service offers, types, exporters and traders are mapped onto management components and modeled as managed objects. Therefore, the Guidelines for the Definition of Managed Objects (GDMO) are used. The final concept allows a precise and unambiguous study of the service trading scenario and provides means for exporting and importing of service offers in a distributed environment.  相似文献   
2.
Chitosan (CS)/poly(vinyl alcohol) (PVA) and Chitosan/poly(2-hydroxyethyl methacrylate) (P2HEM) blends have been studied through molecular dynamic simulations. In a previous work it was found miscibility between these polymers and it was attributed to hydrogen bonding formation. However, the experimental information obtained was not enough to know which of the interacting groups of Chitosan, i.e. -CH2OH or -NH2, are responsible of the interaction. Therefore, we have performed molecular dynamics simulation runs of 1 ns in order to calculate radial distribution functions (RDF) for the groups tentatively involved in the interaction. The results are correlated with our previous experimental data. This way, we have obtained a more precise conclusive information about the interactions involved as function of the blends composition. For low compositions of PVA and P2HEM the interaction is predominantly with the hydroxymethyl groups of CS while as the composition of PVA and P2HEM increases, the interaction with the amine groups increases.  相似文献   
3.

Background  

Excess body fat is a major risk factor for disease primarily due to its endocrine activity. In recent years several criteria have been introduced to evaluate this factor. Nevertheless, treatment need is currently assessed only on the basis of an individual's Body Mass Index (BMI), calculated as body weight (in kg) divided by height in m2. The aim of our study was to determine whether application of the BMI, compared to adiposity-based criteria, results in underestimation of the number of subjects needing lifestyle intervention.  相似文献   
4.
5.
Primer walking of cloned DNA is a standard research tool. It has been used in the past to determine the sequence of individual clones of interest. With the expansion of DNA sequencing capacity the need to be able to walk larger numbers of clones has become necessary. Our laboratory is a mid-sized genomics facility. In conjunction with the Advanced Biomedical Computing Center (ABCC) we have developed methods for automating the primer selection, DNA sequencing, contig assembly and sequence analysis for clones arrayed in microtiter format. This approach has allowed us to walk 475 clones (five microtiter plates) selected from a cDNA library.  相似文献   
6.
7.
8.
This article reviews the evidence and theory pertaining to a form of perspective-taking failure--a difficulty in setting aside the privileged information that one knows to be unavailable to another party. The authors argue that this bias (epistemic egocentrism, or EE) is a general feature of human cognition and has been tapped by 2 independent and largely uncommunicating research traditions: the theory-of-mind tradition in developmental psychology and, with more sensitive probes, the "heuristics and biases" tradition in the psychology of human judgment. This article sets the stage for facilitating communication between these traditions as well as for the recognition of EE's breadth and potential interdisciplinary significance. The authors propose a life-span account and a tentative taxonomy of EE; and they highlight the interdisciplinary significance of EE by discussing its implications for normative ethics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
9.
10.
Physalis angulata L (Solanaceae) is a medicinal plant from North of Brazil, whose different extracts and infusions are commonly used in the popular medicine for the treatment of malaria, asthma, hepatitis, dermatitis and rheumatism. However, the genotoxic effects of P. angulata on human cells is not well known. The main purpose of the present study was to evaluate the in vitro genotoxic effects of aqueous extract of P. angulata using the comet assay and the micronucleus assay in human lymphocytes provided from 6 healthy donors. Treatments with P. angulata extracts were performed in vitro in order to access the extent of DNA damage. The comet assay has shown that treatments with P. angulata at 0.5, 1.0, 2.0, 3.0 and 6.0 microg/mL in culture medium were genotoxic. Lymphocytes treated with P. angulata at the concentrations of 3.0 and 6.0 microg/mL in culture medium showed a statistically significant increase in the frequency of micronucleus (p<0.05), however, the cytokinesis blocked proliferation index (CBPI) was not decreased after P. angulata treatment. In conclusion, the present work demonstrated the genotoxic effects of P. angulata extract on human lymphocytes in vitro.  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