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   2826篇
  免费   232篇
  国内免费   4篇
电工技术   25篇
综合类   29篇
化学工业   1046篇
金属工艺   37篇
机械仪表   49篇
建筑科学   122篇
矿业工程   7篇
能源动力   65篇
轻工业   441篇
水利工程   45篇
石油天然气   5篇
无线电   134篇
一般工业技术   441篇
冶金工业   224篇
原子能技术   12篇
自动化技术   380篇
  2024年   16篇
  2023年   31篇
  2022年   180篇
  2021年   187篇
  2020年   107篇
  2019年   103篇
  2018年   102篇
  2017年   111篇
  2016年   125篇
  2015年   103篇
  2014年   138篇
  2013年   201篇
  2012年   157篇
  2011年   237篇
  2010年   140篇
  2009年   145篇
  2008年   151篇
  2007年   121篇
  2006年   83篇
  2005年   58篇
  2004年   60篇
  2003年   59篇
  2002年   50篇
  2001年   31篇
  2000年   36篇
  1999年   39篇
  1998年   59篇
  1997年   33篇
  1996年   22篇
  1995年   29篇
  1994年   21篇
  1993年   19篇
  1992年   12篇
  1991年   10篇
  1990年   12篇
  1989年   6篇
  1988年   4篇
  1987年   5篇
  1986年   6篇
  1985年   5篇
  1984年   4篇
  1983年   5篇
  1982年   4篇
  1981年   6篇
  1979年   6篇
  1978年   4篇
  1977年   4篇
  1975年   4篇
  1974年   2篇
  1965年   4篇
排序方式: 共有3062条查询结果,搜索用时 15 毫秒
11.
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   
12.
Definition of the problem: Ethical reasoning cannot be enforced. Voluntary understanding is a basic condition for the development of ethical competencies and attitudes. The aim of this survey was to investigate whether the presence of those students who attended our seminars compulsorily would have a negative effect upon the quality of the course. Methods and results: The participants of our small-group seminars in medical ethics were asked to complete a questionnaire on teaching aims, seminar atmosphere, moderation and importance of subjects. One hundred and ninety-two voluntary participants (2001/2) and 293 compulsory participants (2002/3) completed the questionnaire and were statistically compared. There was no significant difference between voluntary and compulsory participants in any of the important items. However, there were considerable differences in some items between male and female participants. Conclusion: We were surprised that there was no difference between the two groups. This leads us to hope that our concept of case-based small-group seminars will prove capable of realising our teaching aims for all students. The difference between male and female participants may have important didactic consequences and will be the subject of further studies.  相似文献   
13.
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   
14.

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   
15.
The current era of Information, Communication and Media Technologies (ICMT) has ushered in the era of eBusiness and the Information Society where traditional managerial paradigms are challenged and new business models are sought. One central area of managerial discourse is STRATEGY. Based upon a pilot study with leading European managers, consultants and academics, we offer a structured perspective on what may be the shape of things to come for STRATEGIC PLANNING in the context of eBusiness and the Information Society. Normative implications are explored.  相似文献   
16.
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   
17.
In the last rice harvest season, experimental results have been obtained on the efficiency and drying quality of a solar assisted heat pump drying prototype system. The system has been operated as a solar and heat pump system and drying curves for the different options have been obtained. The advantage of the low temperature and better control in the drier shows that the heat pump assisted solar drying system is an excellent alternative to traditional drying systems.  相似文献   
18.
Suitable parameter sets for the CHARMm force field were derived for the structural units in polychlorophosphazene [P=N, P N, P Cl] using the Dinur Hagler energy second derivative procedure based on quantum mechanical SCI calculations using the 6–31G* basis set. To validate the reliability of the parameter set, structural results obtained with CHARMm for the adopted model compounds (OP2NCl5 and OP3N2Cl5) were compared with those derived fromab initio quantum mechanics using the 6–31G* basis set. Application of molecular dynamics (MD) simulations in combinatioin with the available X-ray diffraction data provided structural and conformational information on the polymer. The calculation made using the periodic boundary conditions (PBC) agree well with the polychlorophosphazene ordered in a monoclinic unit cell (a=5.98,b=12.99,c=4.92 A; β=111.7). This model was stabilized mainly by the image atoms contribution to the electrostatic energy term and had aquasi-planar conformation of the backbone chain (glide symmetry). The MD calculations also provided evidence that the difference between single and double PN bonds is less marked than that measured experimentally. This result is, however, in agreement with more recent and accurate X-ray studies on poly(methylphosphazene). Validation of the polymer model provided a complete picture, otherwise experimentally inaccessible, of the internal fluctuations of the polymeric chains.  相似文献   
19.
A novel technique for both online and offline computation is presented. With this technique, a reconstruction analysis in elementary particle physics, otherwise prohibitively long, has been accomplished. It will be used online in an upcoming Fermilab experiment to reconstruct more than 100000 events per second and to trigger on the basis of that information. The technique delivers 40 gigaoperations per second, has a bandwidth on the order of gigabytes per second, and has a modest cost. An overview of the program, details of the system, and performance measurements are presented  相似文献   
20.
Investigated whether (1) feminist identity development for women therapists was related to their use of feminist therapy behaviors (FTBs) and (2) feminist identity development and use of FTBs for women therapists were related to self-identification as a feminist therapist. 153 women psychologists (aged 30–77 yrs) were administered a women's issues in therapy questionnaire, which included a short version of the Feminist Identity Scale (FIS; K. M. Rickard, 1989, 1990). Ss were categorized into stages of feminine identity development according to their scores on 4 subscales of the FIS: Passive-Acceptance (PA), Revelation (REV), Embeddedness (EMB), and Synthesis (SYN). Ss scoring high on SYN and REV, and low on PA, reported greater use of FTBs; scores on the EMB were not related to the use of FTBs. All 4 subscales were predictive of women therapists who self-identified as feminist therapists. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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