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   7722篇
  免费   657篇
  国内免费   280篇
电工技术   71篇
技术理论   4篇
综合类   1422篇
化学工业   294篇
金属工艺   40篇
机械仪表   59篇
建筑科学   1759篇
矿业工程   44篇
能源动力   52篇
轻工业   921篇
水利工程   163篇
石油天然气   30篇
武器工业   16篇
无线电   1083篇
一般工业技术   983篇
冶金工业   672篇
原子能技术   12篇
自动化技术   1034篇
  2024年   73篇
  2023年   268篇
  2022年   314篇
  2021年   340篇
  2020年   355篇
  2019年   271篇
  2018年   242篇
  2017年   238篇
  2016年   239篇
  2015年   253篇
  2014年   508篇
  2013年   442篇
  2012年   564篇
  2011年   603篇
  2010年   540篇
  2009年   531篇
  2008年   467篇
  2007年   502篇
  2006年   402篇
  2005年   318篇
  2004年   279篇
  2003年   212篇
  2002年   201篇
  2001年   131篇
  2000年   64篇
  1999年   44篇
  1998年   30篇
  1997年   34篇
  1996年   20篇
  1995年   28篇
  1994年   10篇
  1993年   8篇
  1992年   10篇
  1991年   8篇
  1990年   16篇
  1989年   5篇
  1988年   10篇
  1987年   6篇
  1986年   5篇
  1985年   8篇
  1984年   6篇
  1983年   4篇
  1980年   5篇
  1971年   3篇
  1966年   3篇
  1964年   3篇
  1963年   3篇
  1961年   3篇
  1957年   5篇
  1955年   7篇
排序方式: 共有8659条查询结果,搜索用时 15 毫秒
951.
景观设计与地域文化元素之间既互相影响又相互作用,在进行设计的时候要将这个地区的文化作为设计的基础,然后在设计的时候两者进行相互融合,这样设计出来的作品才会有更高的文化认同感,而且地域文化也能作为景观设计作者进行创作的源头。  相似文献   
952.
A systematic, diversity-oriented synthesis approach was employed to access a natural product-inspired flavonoid library with diverse chemical features, including chemical properties, scaffold, stereochemistry, and appendages. Using Cell Painting, the effects of these diversity elements were evaluated, and multiple chemical features that predict biological performance diversity were identified. Scaffold identity appears to be the dominant predictor of performance diversity, but stereochemistry and appendages also contribute to a lesser degree. In addition, the diversity of chemical properties contributed to performance diversity, and the driving chemical property was dependent on the scaffold. These results highlight the importance of key chemical features that may inform the creation of small-molecule, performance-diverse libraries to improve the efficiency and success of high-throughput screening campaigns.  相似文献   
953.
954.
茶艺是我国传统文化的重要组成部分,在我国有着悠久的历史。现代社会弘扬传统文化,也为茶艺文化的发展创新带来了新的繁荣,茶艺受到国内外许多人士的喜爱。而茶艺元素也被广泛应用于服装设计中,现代服装设计与传统茶文化的融合,使得传统文化焕发新的生机。文章主要分析了服装设计中如何更好地运用茶艺元素。  相似文献   
955.
956.
The genetic diversity and population structure of Salvia lachnostachys Benth were assessed. Inter Simple Sequence Repeat (ISSR) molecular markers were used to investigate the restricted distribution of S. lachnostachys in Parana State, Brazil. Leaves of 73 individuals representing three populations were collected. DNA was extracted and submitted to PCR-ISSR amplification with nine tested primers. Genetic diversity parameters were evaluated. Our analysis indicated 95.6% polymorphic loci (stress value 0.02) with a 0.79 average Simpson’s index. The Nei-Li distance dendrogram and principal component analysis largely recovered the geographical origin of each sample. Four major clusters were recognized representing each collected population. Nei’s gene diversity and Shannon’s information index were 0.25 and 0.40 respectively. As is typical for outcrossing herbs, the majority of genetic variation occurred at the population level (81.76%). A high gene flow (Nm = 2.48) was observed with a correspondingly low fixation index. These values were generally similar to previous studies on congeneric species. The results of principal coordinate analysis (PCA) and of arithmetic average (UPGMA) were consistent and all three populations appear distinct as in STRUCTURE analysis. In addition, this analysis indicated a majority intrapopulation genetic variation. Despite the human pressure on natural populations our study found high levels of genetic diversity for S. lachnostachys. This was the first molecular assessment for this endemic species with medicinal proprieties and the results can guide for subsequent bioprospection, breeding programs or conservation actions.  相似文献   
957.
Traditional kefir grains were collected from distinct parts of Turkey, and their microbial profile was determined. A wide bacterial biota was observed formed by distinct lactic acid bacteria (LAB) in which Lactococcus lactis strains appeared to be dominant. Yeast species were also identified in kefir grains. Significant levels of antifungal and antibacterial activities were monitored in kefir isolates. All tested LAB produced an exopolysaccharide (EPS) containing glucose and galactose, and some strains formed a fructan‐type EPS. Importantly, low levels of antibiotic resistance were observed among the kefir isolates.  相似文献   
958.
We drew on the unified theory of acceptance and use of technology (UTAUT2) model, and perceived risk construct to propose an integrated model to explain continuance usage of mobile shopping applications. Espoused national cultural values of individualism/collectivism, masculinity/femininity, power distance, uncertainty avoidance, and long-term/short-term orientation act as moderators to examine the influence of within-culture variation on app usage. Findings reveal habit as the strongest predictor of both continuance intention and use behaviour, but interestingly perceived risk did not influence the post-acceptance behaviour of users significantly. Individualism/collectivism, masculinity/femininity, and long-term/short-term orientation espoused cultural values significantly moderated the relationships in the model. Noteworthy theoretical and managerial implications of the research are discussed further.  相似文献   
959.
The Alamouti space‐time block code (STBC) achieves full diversity gain at a rate of 1/2. However, the Alamouti scheme does not provide multiplexing gain. The Silver code offers both diversity and multiplexing gain. It has a minimum normalization determinant of . The Golden code is another STBC that offers both diversity and multiplexing gain. The Golden code is ranked higher than the Silver code because of its lower minimum normalization determinant of , however, the golden code suffers from a high detection complexity in the modulation order of M4. The 3/4‐Sezginer code is another STBC, which compromises between the Alamouti scheme and the Golden code in terms of diversity gain and multiplexing gain. The 3/4‐Sezginer code achieves full diversity and half of multiplexing gain. The uncoded space‐time labeling diversity (USTLD) is a recent scheme that improves the error performance when applied to the STBC in multiple‐input multiple‐output (MIMO) systems and will be applied to the 3/4‐Sezginer STBC to improve the error performance in this paper. The theoretical error probability for both the 3/4‐Sezginer STBC and the improved system is formulated using the union bound in this paper. The theoretical error probabilities of both 16‐QAM and 64‐QAM are validated through Monte Carlo simulation. The simulation and theoretical results show that the proposed system with 4 NR can achieve an SNR gain of 1 dB for 16‐QAM and 1.2 dB 64‐QAM at a bit error rate (BER) of 10?6.  相似文献   
960.
Organizational structures are complex and vary according to sector, field, and type of business or service. In order to be effective, an organization needs to tailor its activities to the environment in which is it located. Based on contingency perspectives, this study is focused on investigating effective ways to design team diversity and maximize team creativity according to task difficulty levels. Considering the organizational team member as an agent, the study employed a multi-agent simulation method to understand the progress of creative manifestation, by observing the exploration and exploitation activity of team members over certain periods of time. The results first reveal that the level of team diversity influences the amount of creativity manifested by team members’ activities, such as exploration and exploitation. Second, managers have to properly facilitate either exploration or exploitation depending on task difficulty by striking a balance between them.  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