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   25443篇
  免费   1249篇
  国内免费   322篇
电工技术   563篇
综合类   550篇
化学工业   4811篇
金属工艺   590篇
机械仪表   887篇
建筑科学   1049篇
矿业工程   181篇
能源动力   735篇
轻工业   2537篇
水利工程   281篇
石油天然气   199篇
武器工业   27篇
无线电   2776篇
一般工业技术   3646篇
冶金工业   3900篇
原子能技术   194篇
自动化技术   4088篇
  2023年   151篇
  2022年   239篇
  2021年   745篇
  2020年   423篇
  2019年   518篇
  2018年   565篇
  2017年   551篇
  2016年   629篇
  2015年   545篇
  2014年   779篇
  2013年   1442篇
  2012年   1152篇
  2011年   1385篇
  2010年   1054篇
  2009年   1117篇
  2008年   1068篇
  2007年   1054篇
  2006年   898篇
  2005年   748篇
  2004年   791篇
  2003年   983篇
  2002年   1266篇
  2001年   1075篇
  2000年   639篇
  1999年   585篇
  1998年   1395篇
  1997年   912篇
  1996年   677篇
  1995年   451篇
  1994年   347篇
  1993年   376篇
  1992年   205篇
  1991年   163篇
  1990年   157篇
  1989年   142篇
  1988年   136篇
  1987年   120篇
  1986年   114篇
  1985年   157篇
  1984年   93篇
  1983年   104篇
  1982年   89篇
  1981年   106篇
  1980年   104篇
  1979年   70篇
  1978年   54篇
  1977年   108篇
  1976年   192篇
  1975年   52篇
  1973年   53篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
The complex tissue-specific physiology that is orchestrated from the nano- to the macroscale, in conjugation with the dynamic biophysical/biochemical stimuli underlying biological processes, has inspired the design of sophisticated hydrogels and nanoparticle systems exhibiting stimuli-responsive features. Recently, hydrogels and nanoparticles have been combined in advanced nanocomposite hybrid platforms expanding their range of biomedical applications. The ease and flexibility of attaining modular nanocomposite hydrogel constructs by selecting different classes of nanomaterials/hydrogels, or tuning nanoparticle-hydrogel physicochemical interactions widely expands the range of attainable properties to levels beyond those of traditional platforms. This review showcases the intrinsic ability of hybrid constructs to react to external or internal/physiological stimuli in the scope of developing sophisticated and intelligent systems with application-oriented features. Moreover, nanoparticle-hydrogel platforms are overviewed in the context of encoding stimuli-responsive cascades that recapitulate signaling interplays present in native biosystems. Collectively, recent breakthroughs in the design of stimuli-responsive nanocomposite hydrogels improve their potential for operating as advanced systems in different biomedical applications that benefit from tailored single or multi-responsiveness.  相似文献   
33.
This article reports a study exploring motivations of Pokémon Game use, individual differences related to personality traits, and game habits. First, it analyzed Pokémon GO motivations through exploratory factor analysis (EFA) by administering online the Pokémon GO Motivational Scale to a group of Italian gamers (N = 560). Successively, a Confirmatory Factor Analysis (CFA) was conducted testing three factorial models of Pokémon Game motivations on a selected random sample (N = 310). Results showed a three-factor model of Pokémon GO Game motivations (i.e. Personal Needs, Social Needs and Recreation), accounting for 68.9% of total variance plus a general higher order factor that best fits the data. Individual differences in Pokémon GO motivations and personality traits have been explored showing that high involved Pokémon GO players are introverted, low agreeableness, and conscientiousness people, driven by personal social and recreational needs. Reciprocal influences on motivational involvement, personality, and game habits were discussed.  相似文献   
34.
35.
Microsystem Technologies - This paper represents low power and high speed design issues of Hamming code generation and error detection circuit using complementary metal oxide semiconductor (CMOS)...  相似文献   
36.
37.
亚波长光栅用于实现宽光谱消色散1/4波片的研究   总被引:15,自引:2,他引:13  
基于严格耦合波理论 ,分析了共振区域矩形位相光栅的衍射特性 :位相延迟与光栅周期、占空比、槽深的关系 ,并设计出在 40 0~ 80 0nm范围内的消色散 1/4波片光栅 ,可以实现较为平坦的衍射效率和位相延迟曲线 ,其中位相延迟可保持在 90°左右 ,最大偏差小于 9% ,达到甚至优于普通二元复合消色散波片。通过对加工及安装误差的讨论 ,得到了影响消色散波片光栅性能的主要加工误差是槽深误差和占空比误差。  相似文献   
38.
Up until today extreme rainfall properties are frequently applied in sewer design guidelines. Uncertainty in the estimation of such properties will hence directly influence the dimensions of sewers, structures and pumps. In this paper the issue of potential trend and noise in the estimation is investigated for 6 rain series ranging from 19 to 55 years in duration. Different to recent research that predicts a climate induced-increase in heavy precipitation no clear indication for such trend was found in the investigated historical rain series. Another important aspect is the length of the rain series that is required for the estimation of extreme rainfall properties and the associated uncertainty. The analysis indicates that at least a period of 10 years should be used for the estimation. But even so the possible deviation expressed in terms of the 90 percentile is in the order of 5 to 10% of the 'true value', defined as the value derived when the whole given series is used for the estimation.  相似文献   
39.
The objective of this research was to investigate the feasibility of visible transmission spectroscopy for the non‐destructive assessment of the freshness of an individual egg. A total of 600 intact white‐shelled eggs of the same flock (Lohmann, 40 weeks of age) were measured. To obtain a considerable variation in freshness, groups consisting of 60 eggs were stored (18 °C, 55% RH) for 0, 2, 4, 6, 8, 10, 12, 14, 16 and 18 days. The non‐destructive spectral measurements were compared with the two most widely used destructive freshness parameters, namely Haugh units and albumen pH. A partial least squares (PLS1) model was built in order to predict Haugh units and pH of the albumen based on the transmission spectra. The correlation coefficients between the predicted value and the measured value were 0.842 and 0.867 for Haugh unit and pH of the albumen, respectively. These results show that the light transmission spectrum of an egg provides quantitative information about egg freshness. Relevant information concerning egg freshness is restricted to the interval between 570 and 750 nm. Furthermore, the models obtained for both destructive parameters were strikingly similar, indicating that Haugh unit and pH have the same physico‐chemical background. Copyright © 2006 Society of Chemical Industry  相似文献   
40.
Integrated tests (IT) applied to the Units I and II of the CNAAA Nuclear Power Plants (Angra dos Reis, Rio de Janeiro, Brazil) vara part of a comprehensive test program required to have the commercial operational licence issued. The IT cover operation at zero power and the subsequent power levels (the power escalation) until the nominal power operation.

This paper reports and compares the results of systematic neutron and gamma equivalent dose-rate measurements performed inside and outside the reactor containment of each Unit, during the start-up phase of the operation, for different power levels of the reactors. It also compares the collective-doses measured along the operation of the two units of the CNAAA wich similar data of the Grafenrheinfeld nuclear power plant (Germany) — basic-of-project for the CNAAA — Unit II — and analyses the data under the fight of the state-of-art.  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