全文获取类型
收费全文 | 875篇 |
免费 | 41篇 |
国内免费 | 8篇 |
学科分类
工业技术 | 924篇 |
出版年
2024年 | 3篇 |
2023年 | 18篇 |
2022年 | 31篇 |
2021年 | 52篇 |
2020年 | 38篇 |
2019年 | 40篇 |
2018年 | 47篇 |
2017年 | 48篇 |
2016年 | 29篇 |
2015年 | 29篇 |
2014年 | 30篇 |
2013年 | 69篇 |
2012年 | 45篇 |
2011年 | 51篇 |
2010年 | 41篇 |
2009年 | 36篇 |
2008年 | 43篇 |
2007年 | 32篇 |
2006年 | 30篇 |
2005年 | 26篇 |
2004年 | 17篇 |
2003年 | 6篇 |
2002年 | 14篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 13篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 11篇 |
1990年 | 15篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有924条查询结果,搜索用时 15 毫秒
1.
The nature of pairing mechanism as well as transition temperature of yttrium cuprates is discussed using the strong coupling
theory. An interaction potential has been developed for the layered structure with two conducting CuO2(a–b) layers in a unit cell. The interaction potential properly takes care of electron-electron, electron-phonon and electron-plasmon
interactions. Furthermore, the electron-phonon coupling parameter (λ), the modified Coulomb repulsive parameter (μ*) and the 2D acoustic phonon (plasmon) energy as a function of oxygen deficiency is worked out. Finally, the superconducting
transition temperature (T
c) is then evaluated by using these coupling parameters and obtainedT
c = 95(92)K for Y(Yb)Ba2Cu3O7−δ
superconductors withδ = 0·0. The model parameters estimated from the layered structure approach are consistent with the strong coupling theory.
The result deduced on the variation ofT
c withδ are in fair agreement with the earlier reported data on yttrium cuprates. The analysis of the above results are discussed. 相似文献
2.
R. Dinesh T. Fujiwara T. Watanabe K. Byrappa M. Yoshimura 《Journal of Materials Science》2006,41(5):1541-1546
A well-crystallized AMO4 (A=Ba, Ca, Sr; M=W, Mo) films have been prepared at room temperature through a simple solution reaction in respective alkaline
solution at higher pH ranging from 12–14. Adopting the corrosion principle for oxidation of metal substrate, these double
oxide films were carried out in presence of chemical driving force without any special apparatus or devices. Hydrogen peroxide
was used to enhance the dissolution rate of metal substrates. The driving force for the film formation and growth were high
concentration of A2+, MO42− ions with high pH conditions. Average grain sizes of 8–10 μm with bipyramidal shaped particle were grown to the thickness
of about 10–14 μm after 3–6 hours treatment. The crystallization of AMO4 was characterized by three-dimensional nucleation. This work demonstrates the possibility of fabrication of functional ceramic
films directly from the aqueous solution in a single step by solution reactions. 相似文献
3.
Simonetta Pazzaglia Barbara Tanno Francesca Antonelli Paola Giardullo Gabriele Babini Prabal Subedi Omid Azimzadeh Zohaib N. Khan Kateryna Oleksenko Fabian Metzger Christine von Toerne Damien Traynor Dinesh Medipally Aidan D. Meade Munira Kadhim Fiona M. Lyng Soile Tapio Anna Saran Mariateresa Mancuso 《International journal of molecular sciences》2021,22(8)
The brain undergoes ionizing radiation exposure in many clinical situations, particularly during radiotherapy for brain tumors. The critical role of the hippocampus in the pathogenesis of radiation-induced neurocognitive dysfunction is well recognized. The goal of this study is to test the potential contribution of non-targeted effects in the detrimental response of the hippocampus to irradiation and to elucidate the mechanisms involved. C57Bl/6 mice were whole body (WBI) or partial body (PBI) irradiated with 0.1 or 2.0 Gy of X-rays or sham irradiated. PBI consisted of the exposure of the lower third of the mouse body, whilst the upper two thirds were shielded. Hippocampi were collected 15 days or 6 months post-irradiation and a multi-omics approach was adopted to assess the molecular changes in non-coding RNAs, proteins and metabolic levels, as well as histological changes in the rate of hippocampal neurogenesis. Notably, at 2.0 Gy the pattern of early molecular and histopathological changes induced in the hippocampus at 15 days following PBI were similar in quality and quantity to the effects induced by WBI, thus providing a proof of principle of the existence of out-of-target radiation response in the hippocampus of conventional mice. We detected major alterations in DAG/IP3 and TGF-β signaling pathways as well as in the expression of proteins involved in the regulation of long-term neuronal synaptic plasticity and synapse organization, coupled with defects in neural stem cells self-renewal in the hippocampal dentate gyrus. However, compared to the persistence of the WBI effects, most of the PBI effects were only transient and tended to decrease at 6 months post-irradiation, indicating important mechanistic difference. On the contrary, at low dose we identified a progressive accumulation of molecular defects that tended to manifest at later post-irradiation times. These data, indicating that both targeted and non-targeted radiation effects might contribute to the pathogenesis of hippocampal radiation-damage, have general implications for human health. 相似文献
4.
Gerard E. Lenain Herbert A. McKinstry Dinesh K. Agrawal 《Journal of the American Ceramic Society》1985,68(9):224-C
The X-ray diffraction pattern for potassium-zirconium phosphate is significantly improved when the material is prepared by the sol-gel route rather than the powder method. Peaks at high, low, and intermediate angles are presented and compared for the two methods. It is assumed that the more nearly homogeneous mixing of the elements in the sol-gel process is responsible for the significant improvement in crystallinity. 相似文献
5.
ICCD: Interactive Continuous Collision Detection between Deformable Models Using Connectivity-Based Culling 总被引:1,自引:0,他引:1
Tang Min Curtis Sean Yoon Sung-Eui Manocha Dinesh 《IEEE transactions on visualization and computer graphics》2009,15(4):544-557
We present an interactive algorithm for continuous collision detection between deformable models. We introduce multiple techniques to improve the culling efficiency and the overall performance of continuous collision detection. First, we present a novel formulation for continuous normal cones and use these normal cones to efficiently cull large regions of the mesh as part of self-collision tests. Second, we introduce the concept of “procedural representative triangles” to remove all redundant elementary tests between nonadjacent triangles. Finally, we exploit the mesh connectivity and introduce the concept of “orphan sets” to eliminate redundant elementary tests between adjacent triangle primitives. In practice, we can reduce the number of elementary tests by two orders of magnitude. These culling techniques have been combined with bounding volume hierarchies and can result in one order of magnitude performance improvement as compared to prior collision detection algorithms for deformable models. We highlight the performance of our algorithm on several benchmarks, including cloth simulations, N-body simulations, and breaking objects. 相似文献
6.
7.
基于SIMD指令的柔性物体并行碰撞检测 总被引:2,自引:0,他引:2
复杂场景中柔性物体间的碰撞检测依然难以满足交互设计的要求.为了提高处理速度,文中给出了一种充分利用现代CPU的并行处理能力的碰撞检测算法.算法基于两方面的并行处理:即基于SIMD指令的指令级并行处理和基于多线程的任务级并行处理.算法给出了一种针对SIMD指令特别优化的k-DOP模型--SIMD-DOP,从理论上分析了该包围盒的高效性,并与常规的16-DOP和24-DOP进行了运行效率对比.通过使用SIMD-DOP同时在多核间进行负载均衡,算法获得了优化的并行加速.文中算法已经在一台16核工作站上针对一组复杂测试场景进行了验证. 相似文献
8.
Real-time path planning in dynamic virtual environments using multiagent navigation graphs 总被引:1,自引:0,他引:1
Sud A Andersen E Curtis S Lin MC Manocha D 《IEEE transactions on visualization and computer graphics》2008,14(3):526-538
We present a novel approach for efficient path planning and navigation of multiple virtual agents in complex dynamic scenes. We introduce a new data structure, Multi-agent Navigation Graph (MaNG), which is constructed using first- and second-order Voronoi diagrams. The MaNG is used to perform route planning and proximity computations for each agent in real time. Moreover, we use the path information and proximity relationships for local dynamics computation of each agent by extending a social force model [Helbing05]. We compute the MaNG using graphics hardware and present culling techniques to accelerate the computation. We also address undersampling issues and present techniques to improve the accuracy of our algorithm. Our algorithm is used for real-time multi-agent planning in pursuit-evasion, terrain exploration and crowd simulation scenarios consisting of hundreds of moving agents, each with a distinct goal. 相似文献
9.
The current study shows that the recent diesel price hike had an insignificant impact on irrigation costs incurred by diesel well owners in eastern India. Further, analysis of the farming enterprises of diesel well owners and water buyers from both diesel and electric wells confronted with a differential cost of irrigation water showed that farmers would be able to cope with a very high rise in irrigation costs through irrigation efficiency improvements and allocating more area to crops that give higher returns per unit of land and water. By doing this, they are able to maintain the farm returns. 相似文献
10.
We approach the issue of water productivity in agriculture by identifying five sets of drivers of change. We find that irrigation efficiencies at the field level can result in real water savings under certain conditions, but that small farmers in most of South Asia and Africa have little incentive to adopt the appropriate measures. Although water productivity improvement and water savings at the regional level are possible through a shift to economically efficient crops, such changes may be constrained by concerns with respect to domestic and regional food security, rural employment, and farming system resilience. 相似文献