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   223214篇
  免费   20660篇
  国内免费   10455篇
电工技术   14595篇
技术理论   30篇
综合类   23166篇
化学工业   27254篇
金属工艺   9647篇
机械仪表   11708篇
建筑科学   31426篇
矿业工程   12741篇
能源动力   8341篇
轻工业   16015篇
水利工程   11231篇
石油天然气   12101篇
武器工业   3251篇
无线电   14591篇
一般工业技术   16614篇
冶金工业   11359篇
原子能技术   1739篇
自动化技术   28520篇
  2024年   777篇
  2023年   2804篇
  2022年   5387篇
  2021年   7406篇
  2020年   7032篇
  2019年   5364篇
  2018年   5055篇
  2017年   6312篇
  2016年   7846篇
  2015年   8580篇
  2014年   15419篇
  2013年   13593篇
  2012年   16295篇
  2011年   18032篇
  2010年   13215篇
  2009年   13487篇
  2008年   12405篇
  2007年   14989篇
  2006年   13574篇
  2005年   11862篇
  2004年   9869篇
  2003年   8568篇
  2002年   6947篇
  2001年   5747篇
  2000年   4914篇
  1999年   3846篇
  1998年   2740篇
  1997年   2396篇
  1996年   1964篇
  1995年   1647篇
  1994年   1387篇
  1993年   987篇
  1992年   809篇
  1991年   572篇
  1990年   494篇
  1989年   457篇
  1988年   255篇
  1987年   195篇
  1986年   169篇
  1985年   189篇
  1984年   139篇
  1983年   119篇
  1982年   62篇
  1981年   77篇
  1980年   83篇
  1979年   40篇
  1978年   22篇
  1977年   23篇
  1975年   18篇
  1959年   28篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
ABSTRACT

Social licence to operate (SLO) is a term that is finding increasing acceptance in a number of industries. Like all new terms, its precise meaning and implications are still being investigated. Using data from previous studies, this paper offers an analysis of the SLO of two case studies with each study being viewed separately through the grid of a distinct theoretical framework. Case study 1 looks at the development of differential social licence negotiated in the Hamlet of Cambridge Bay, Nunavut, as a result of an impact and benefit agreement negotiated between Tahera Diamond Corp. and the Kitikmeot Inuit Organisation in 2004. The study demonstrates that general acceptance of resource development can be uneven and reflect an unequal distribution of decision-making power. In case study 2, stakeholders of a failed mineral development project were queried across time about the specifics of the proposed mine development and were queried about resource development across different levels of consciousness. Perhaps, SLO is variable across different levels of consciousness. The paper concludes with observations about the variable nature of SLO acceptance across populations and across levels of consciousness within individuals. Perhaps, the concept of SLO is, in fact, complex, difficult to define and measure and, at this point, of limited utility as a measure of resource development acceptance.  相似文献   
122.
Cone-beam X-ray luminescence computed tomography (CB-XLCT) is an attractive hybrid imaging modality, and it has the potential of monitoring the metabolic processes of nanophosphors-based drugs in vivo. However, the XLCT imaging suffers from a severe ill-posed problem. In this work, a sparse nonconvex Lp (0?p?L1 regularization. Further, an iteratively reweighted split augmented lagrangian shrinkage algorithm (IRW_SALSA-Lp) was proposed to efficiently solve the non-convex Lp (0?p?p-values (1/16, 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 7/8) in both 3D digital mouse experiments and in vivo experiments. The results demonstrate that the proposed non-convex methods outperform L2 and L1 regularization in accurately recovering sparse targets in CB-XLCT. And among all the non-convex p-values, our Lp(1/4?p?相似文献   
123.
Evidence suggests that transient visual information, such as animations, may be more challenging to learn than static visualizations. However, when a procedural-manipulative task is involved, our evolved embodied cognition seems to reverse this transitory challenge. Hence, for object manipulative tasks, instructional animations may be more suitable than statics. We investigated this argument further by comparing animations with statics using a Lego task shown to university students, by examining three potential moderators of effectiveness: (a) the environment of manipulation (virtual or physical), (b) the quality of visual information (focused or unfocused), and (c) the presence of hands (no hands or with hands). In Experiment 1 we found an advantage of animation over statics, and no differences among the environments. In Experiment 2, we again observed an animation advantage, a small advantage of focused static information compared to unfocused static information, and a positive effect of not showing the hands.  相似文献   
124.
We used perceptual and oculomotor measures to understand the negative impacts of low (phantom array) and high (motion blur) duty cycles with a high‐speed, AR‐likehead‐mounted display prototype. We observed large intersubject variability for the detection of phantom array artifacts but a highly consistent and systematic effect on saccadic eye movement targeting during low duty cycle presentations. This adverse effect on saccade endpoints was also related to an increased error rate in a perceptual discrimination task, showing a direct effect of display duty cycle on the perceptual quality. For high duty cycles, the probability of detecting motion blur increased during head movements, and this effect was elevated at lower refresh rates. We did not find an impact of the temporal display characteristics on compensatory eye movements during head motion (e.g., VOR). Together, our results allow us to quantify the tradeoff of different negative spatiotemporal impacts of user movements and make subsequent recommendations for optimized temporal HMD parameters.  相似文献   
125.
杨家强  邓玲  安家丽  赵仕新 《精细化工》2019,36(9):1869-1873
为了寻找抗菌候选化合物,采用基于片段的药物发现方法,以氨基膦酸酯和磺酰氯为原料,设计合成了15个含膦酸酯结构单元的磺胺衍生物,经IR、1HNMR和13CNMR确认结构。采用两倍稀释法测定目标化合物的MIC(最小抑菌浓度)。结果表明:部分目标化合物呈潜在的抗菌活性,对所测试标准菌和耐药菌均有抑制活性。其中,化合物Ⅱf〔N-[(二乙氧基膦酰基)-4-氟苯甲基]-4-甲氧基苯磺酰胺〕对金黄色葡萄球菌(S. aureus)、大肠埃希菌(E. coli)、耐甲氧西林金黄色葡萄球菌(MRSA)及耐氟喹诺酮类大肠杆菌(MREC)的MIC分别为32、64、128和128μg/mL,化合物Ⅱl〔N-[(二乙氧基膦酰基)-4-氟苯甲基]-4-氟苯磺酰胺〕对S. aureus、E. coli、MRSA及MREC的MIC分别为32、32、64和64μg/mL,抗菌活性优于对照药磺胺嘧啶。  相似文献   
126.
The present study focuses on experimental investigation of through the thickness displacement and strain field in thin adhesive layer in single sided (unsymmetrical) patch repaired CFRP (carbon fiber reinforced polymer) panel under tensile load. Digital image correlation (DIC) technique is employed to acquire the displacement and strain (longitudinal, peel and shear) field. Experimental determination of shear transfer length based on shear strain field obtained from DIC is introduced to estimate the optimum overlap length which is an essential parameter in patch design for the repair of CFRP structures. Further, DIC experiment with magnified optics is performed to get an insight into complex and localized strain field over thin adhesive layer especially at critical zones leading to damage initiation. The failure mechanism, load displacement behavior, damage initiation and propagation are closely monitored using DIC. The influence of patch edge tapering on strain distribution in adhesive layer is also investigated. The DIC successfully captures the global and localized strain field at critical zones over thin adhesive layer and further helps in monitoring the damage based on strain anomalies. Strains are found to have maximum magnitude at the patch overlap edge and the shear strain level in adhesive layer is higher than the peel strain. Normal tapering increases the peel strain and has negligible influence on shear strain level in adhesive layer. The recommended overlap length is found to be consistent with the recommendation in the literature. Whole field strain pattern and the overlap length obtained from experiment are further compared with the finite element analysis results and they appear to be in good coherence.  相似文献   
127.
Numerical dissipation acts as artificial viscosity to make smoke viscous. Reducing numerical dissipation is able to recover visual details smeared out by the numerical dissipation. Great efforts have been devoted to suppress the numerical dissipation in smoke simulation in the past few years. In this paper we investigate methods of combating the numerical dissipation. We describe visual consequences of the numerical dissipation and explore sources that introduce the numerical dissipation into course of smoke simulation. Methods are investigated from various aspects including grid variation, high-order advection, sub-grid compensation, invariant conservation, and particle-based improvement, followed by discussion and comparison in terms of visual quality, computational overhead, ease of implementation, adaptivity, and scalability, which leads to their different applicability to various application scenarios.  相似文献   
128.
针对在军棋博弈不完全信息对弈中,面对棋子不同价值、不同位置、不同搭配所产生的不同棋力,传统的单子意图搜索算法,不能满足棋子之间的协同性与沟通性,同时也缺乏对敌方的引诱与欺骗等高级对抗能力。本文提出一种结合UCT搜索策略的高价值棋子博弈方法,实现高价值棋子协同博弈的策略。实战经验表明:高价值多棋子军棋协同博弈策略优于单棋子军棋博弈策略。  相似文献   
129.
130.
The titanium carbides are potential candidates to achieve both high hardness and refractory property. We carried out a structural search for titanium carbides at three pressures of 0 GPa, 30 GPa and 50 GPa. A phase diagram of the Ti-C system at 0 K was obtained by elucidating formation enthalpies as a function of compositions, and their mechanical and metallic properties of titanium carbides were investigated systematically. We also discussed the relation of titanium concentration to the both mechanical and metallic properties of titanium carbides. It has been found that the average valence electron density and tractility improved at higher concentrations of titanium, while the degree of covalent bonding directionality decreased. To this effect, the hardness of titanium carbide decreases as the content of titanium increases. Our results indicated that the titanium content significantly affected the metallic properties of the Ti-C system.  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