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   20883篇
  免费   551篇
  国内免费   24篇
电工技术   217篇
综合类   18篇
化学工业   4426篇
金属工艺   495篇
机械仪表   365篇
建筑科学   923篇
矿业工程   88篇
能源动力   535篇
轻工业   1398篇
水利工程   261篇
石油天然气   205篇
武器工业   1篇
无线电   1425篇
一般工业技术   3362篇
冶金工业   4529篇
原子能技术   167篇
自动化技术   3043篇
  2022年   147篇
  2021年   241篇
  2020年   198篇
  2019年   263篇
  2018年   296篇
  2017年   302篇
  2016年   366篇
  2015年   292篇
  2014年   456篇
  2013年   1236篇
  2012年   750篇
  2011年   944篇
  2010年   755篇
  2009年   761篇
  2008年   884篇
  2007年   953篇
  2006年   782篇
  2005年   740篇
  2004年   648篇
  2003年   609篇
  2002年   582篇
  2001年   364篇
  2000年   365篇
  1999年   359篇
  1998年   441篇
  1997年   386篇
  1996年   373篇
  1995年   362篇
  1994年   308篇
  1993年   358篇
  1992年   313篇
  1991年   227篇
  1990年   275篇
  1989年   280篇
  1988年   265篇
  1987年   252篇
  1986年   283篇
  1985年   299篇
  1984年   297篇
  1983年   291篇
  1982年   231篇
  1981年   258篇
  1980年   253篇
  1979年   251篇
  1978年   227篇
  1977年   229篇
  1976年   205篇
  1975年   195篇
  1974年   174篇
  1973年   179篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Methods for modeling and managing uncertainty in computer vision systems have received increased attention in recent years. Automatic target recognition is one application area of computer vision where the demands are particularly acute. In this article, fuzzy logic is proposed as a means of handling uncertainty in an expert system structure for automatic target recognition. A new technique for logical inference is described which is well-suited for this type of application. A prototype system has been developed and tested on multisensor and temporal images. the results are compared to a similar expert system which used a numeric uncertainty calculus.  相似文献   
12.
13.
14.
Despite its empirical and normative strengths, the underlying conceptual base of the Comprehensive Rorschach System at times lacks clarity and an overarching theory of personality that can help psychodiagnosticians make more clinically relevant inferences. After reviewing the functions provided by an integral theory of personality, the author focuses on the Experience Actual:Experienced Stimulation (EA:es) index as a way of demonstrating how mechanistic jargon and lack of a guiding theory and conceptual clarity can lead to misleading and contradictory inferences. Case examples are provided, and some of the empirical foundations of the EA:es index are reviewed. The author concludes by offering recommendations on ways in which the Comprehensive System can become more sensitive in its appearance to capturing the complexities of personality functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
15.
The authors attempt to provide a better understanding of the differences between the normal memory decline characteristic of age-associated memory impairment (AAMI) and the pathological decline typical of mild Alzheimer's disease (AD). Batteries of traditional memory tests and computer-simulated everyday-memory tests discriminated between the 2 groups, which were matched on age, gender, and education, with reasonable degrees of accuracy (87.5% and 88.4%, respectively). False positives were the most frequent classification errors when using either battery. These results indicate that it is possible to use ecologically valid memory assessment paradigms without sacrificing discriminant validity. The clinical significance of discriminating mild AD from AAMI is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
16.
Analysis of characteristic odors from human male axillae   总被引:7,自引:0,他引:7  
A number of studies concerning the analysis of axillary odors have assumed that the characteristic odor produced in the axillae is due to volatile steroids and isovaleric acid. Organoleptic evaluation of Chromatographic eluants from axillary extracts was employed to isolate the region in the chromatogram where the characteristic odor eluted. The odor of the dissolved eluant was eliminated when it was treated with base, suggesting that acids make up the characteristic axillary odor. Subsequent extraction of the pH-adjusted axillary extract in conjunction with organoleptic evaluation of the Chromatographic eluant, preparative gas chromatography, and analysis by GC-MS as well as GC-FTIR showed the presence of a number of C6 to C11 straight-chain, branched, and unsaturated acids as important contributors to the axillary odor. The major odor component is (E)-3-methyl-2-hexenoic acid. Three homologous series of minor components are also important odor contributors; these consist of the terminally unsaturated acids, the 2-methyl-C6 to -C10 acids and the 4-ethyl-C5 to -C11 acids. These types of acids have not been reported previously as components of the human axillary secretions and have not been proposed previously as part of the principal odor components in this area.  相似文献   
17.
18.
Water and sediment samples from 29 locations in the Detroit and St. Clair rivers were analyzed for the highly toxic tri-n-butyltin (Bu3Sn+) species and for the less toxic di-n-butyltin (Bu2Sn2+) and n-butyltin (BuSn3+) species and inorganic tin. In general, locations sampled in the St. Clair River were less contaminated with butyltin species than those in the Detroit River. Inorganic tin and BuSn3+ were detected in over 90% of all subsurface water samples, while Bu2Sn2+ and Bu3Sn+ were detected in 45 and 28% of the same samples, respectively. The highest concentration ofBu3Sn+ in subsurface water, 5.9 × 10?10 mol Sn/L, was at the mouth of the Ecorse River, a tributary of the Detroit River. The three butyltin species and inorganic tin were also detected in 23–46% of all sediment samples. The highest concentrations of Bu3Sn+ in sediment were found close to the mouths of the River Rouge, another tributary of the Detroit River, and the Ecorse River, and were 6.2 × I0–7 and 1.7 × I0–7 mol Sn/kg dry weight, respectively, for the top 2 cm of sediment.  相似文献   
19.
Practice on addition basic facts and changes in solution strategies were examined in 3rd- and 4th-grade students, practicing over 3 months. Response latencies decreased, indicating positive practice effects. Each of 3 student groups demonstrated different solution–strategy mixtures. Different mixtures led to different practice effects, indexed by shifts to more efficient counting strategies and more direct retrieval. Expectations about effects of practice and instructional strategies for optimizing practice must be sensitive to a child's actual strategy pattern. Most students had decreasing latency practice functions. However, quantitative functions fit to the practice session data indicated a high proportion of cases where the latency pattern over sessions was nonmonotonic. Trends over a small number of practice sessions may be inadequate for decisions about the utility of further practice, because such data may poorly represent long-term, cumulative effects on modifying strategy usage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
20.
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