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   4328篇
  免费   342篇
  国内免费   130篇
电工技术   85篇
综合类   114篇
化学工业   89篇
金属工艺   50篇
机械仪表   249篇
建筑科学   1302篇
矿业工程   82篇
能源动力   198篇
轻工业   102篇
水利工程   106篇
石油天然气   32篇
武器工业   7篇
无线电   427篇
一般工业技术   245篇
冶金工业   31篇
原子能技术   67篇
自动化技术   1614篇
  2024年   5篇
  2023年   72篇
  2022年   98篇
  2021年   124篇
  2020年   135篇
  2019年   82篇
  2018年   77篇
  2017年   104篇
  2016年   174篇
  2015年   186篇
  2014年   261篇
  2013年   236篇
  2012年   264篇
  2011年   311篇
  2010年   243篇
  2009年   283篇
  2008年   262篇
  2007年   281篇
  2006年   276篇
  2005年   232篇
  2004年   198篇
  2003年   182篇
  2002年   146篇
  2001年   89篇
  2000年   89篇
  1999年   81篇
  1998年   69篇
  1997年   41篇
  1996年   28篇
  1995年   28篇
  1994年   34篇
  1993年   15篇
  1992年   14篇
  1991年   14篇
  1990年   8篇
  1989年   14篇
  1988年   6篇
  1987年   4篇
  1986年   11篇
  1985年   6篇
  1984年   3篇
  1983年   7篇
  1980年   1篇
  1979年   2篇
  1978年   2篇
  1977年   1篇
  1973年   1篇
排序方式: 共有4800条查询结果,搜索用时 15 毫秒
1.
In the present era of machines and edge-cutting technologies, still document frauds persist. They are done intuitively by using almost identical inks, that it becomes challenging to detect them—this demands an approach that efficiently investigates the document and leaves it intact. Hyperspectral imaging is one such a type of approach that captures the images from hundreds to thousands of spectral bands and analyzes the images through their spectral and spatial features, which is not possible by conventional imaging. Deep learning is an edge-cutting technology known for solving critical problems in various domains. Utilizing supervised learning imposes constraints on its usage in real scenarios, as the inks used in forgery are not known prior. Therefore, it is beneficial to use unsupervised learning. An unsupervised feature extraction through a Convolutional Autoencoder (CAE) followed by Logistic Regression (LR) for classification is proposed (CAE-LR). Feature extraction is evolved around spectral bands, spatial patches, and spectral-spatial patches. We inspected the impact of spectral, spatial, and spectral-spatial features by mixing inks in equal and unequal proportion using CAE-LR on the UWA writing ink hyperspectral images dataset for blue and black inks. Hyperspectral images are captured at multiple correlated spectral bands, resulting in information redundancy handled by restoring certain principal components. The proposed approach is compared with eight state-of-art approaches used by the researchers. The results depicted that by using the combination of spectral and spatial patches, the classification accuracy enhanced by 4.85% for black inks and 0.13% for blue inks compared to state-of-art results. In the present scenario, the primary area concern is to identify and detect the almost similar inks used in document forgery, are efficiently managed by the proposed approach.  相似文献   
2.
This paper suggests that, for developing countries, the creation of economic regulatory agencies, separate from the ministry in charge of water and sanitation, may not be a necessary or sufficient condition to stimulate large scale private involvement (PPPs) in the sector. The odds of an impact are higher for Latin American countries than other regions and for countries with higher income levels. They are also better when inflation is high. At the margin, the odds are unrelated to the contract type, except for greenfield projects, for which they may be contraindicated.  相似文献   
3.
4.
The St. Clair-Detroit River System contains a world-class Great Lakes muskellunge (Esox masquinongy) fishery that has avoided the declines observed in many Great Lakes muskellunge populations. Muskellunge are an upper trophic level predator, and therefore a naturally low-density species. Limited fishery-independent data exist on which to base management decisions. To remedy this, we initiated an acoustic telemetry study in May of 2016, in collaboration with the Great Lakes Acoustic Telemetry Observation System. Our objective was to describe patterns of movement of muskellunge in this large and open system to better understand their spatial ecology. We acoustically tagged 133 muskellunge in the Detroit River and Lake St. Clair, and movements of 58 fish that passed our data quality control screens were analyzed. We utilized mixed modelling to assess the effects of sex, length, release location, and season on daily movement rates. We found that movement rates only differed among seasons, with highest movement rates occurring in the fall and lowest movement rates in the winter. Muskellunge tagged at different locations exhibited distinct residency patterns, and fish frequently crossed jurisdictional and waterbody boundaries. Ultimately our study highlights the scope and patterns of muskellunge movement in a large, unimpounded system and demonstrates that management of these fish would benefit from consideration of their full distribution covering multiple management jurisdictions.  相似文献   
5.
Transportation infrastructure and innovation play an important role in promoting regional economic growth. However, previous studies have mainly focused on the economic agglomeration by increased accessibility, but ignored the important on inter-city economic linkages and the network externalities it generated. Based on the externality perspective, this paper uses the propensity score matching model (PSM-DID) and spatial econometric model to analyze the heterogeneous impact of HSR opening on urban innovation performance and compare the differential effects of agglomeration externalities and network externalities on knowledge spillovers. The empirical results suggest the following: (1) The opening of HSR significantly improves urban innovation performance, but there is significant spatial heterogeneity. (2) The opening of HSR not only promotes the agglomeration of production factors to cities, but also strengthens inter-city economic connections, thus improving urban innovation performance through agglomeration externalities and network externalities. However, compared to agglomeration externalities, network externalities have a superior strength of impact on urban innovation performance. (3) From the dynamic effect perspective, the opening of HSR has a hysteresis effect on urban innovation of 2–3 years, and differences exist between cities.  相似文献   
6.
裴逸飞  冷嘉伟  龚恺 《建筑师》2019,(1):106-111
本文以江西省婺源县沱川乡理坑、浙源乡虹关以及思口镇西冲的3次村落测绘作为研究的起点,逐步拓展至对12份徽州传统村落宗族图谱中的村落宅图进行分类及量化研究。通过对村落宅图的研究来还原徽州传统村落群的空间形态,探究其背后的地缘影响、血缘纽带和社会维系,归纳总结出9种村落群的基本构成要素及其所占比率,揭示村落群的空间构成和形态要素。希望在此基础上推演村落群形态的历史演变过程,还原与诠释村落群背后隐藏的内在秩序。  相似文献   
7.
Mobile devices with social media applications are the prevalent user equipment to generate and consume digital hate content. The objective of this paper is to propose a mobile edge computing architecture for regulating and reducing hate content at the user's level. In this regard, the profiling of hate content is obtained from the results of multiple studies by quantitative and qualitative analyses. Profiling resulted in different categories of hate content caused by gender, religion, race, and disability. Based on this information, an architectural framework is developed to regulate and reduce hate content at the user's level in the mobile computing environment. The proposed architecture will be a novel idea to reduce hate content generation and its impact.  相似文献   
8.
9.
徐应锦  王冬 《室内设计》2019,(2):95-100
长春洞是巍宝山保存最完整的宫 观,虽占地不到两亩①,却在有限的空间中 创造出九楼十院的空间格局。本文以长春洞 空间布局序列为研究对象,从知觉体验的 连续性入手,提出了空间变化对参观者情感 的影响,论述了在建筑空间布局序列中参观 者知觉体验逐层递进的控制机制,探讨了以 “起、承、转、合”为结构,以“知觉体验”为 章法的动态空间布局设计手法,希望为道教 建筑空间与其他超越日常的精神空间的研 究提供启示。  相似文献   
10.
能源行业法律法规设置了“没收违法所得”行政处罚方式,但违法所得这一概念还存在很多模糊认识,具体认定方式也需要进一步明确。在不同行政机关对违法所得的法律概念存在较大分歧时,能源监管领域应遵循违法所得固有含义和立法原意,结合能源行业的基本特点,采取利润说观点定义违法所得概念,并以全部收人扣减合理支出方式进行计算。  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