全文获取类型
收费全文 | 7112篇 |
免费 | 653篇 |
国内免费 | 322篇 |
专业分类
电工技术 | 1457篇 |
综合类 | 401篇 |
化学工业 | 2140篇 |
金属工艺 | 135篇 |
机械仪表 | 178篇 |
建筑科学 | 216篇 |
矿业工程 | 102篇 |
能源动力 | 643篇 |
轻工业 | 1105篇 |
水利工程 | 191篇 |
石油天然气 | 372篇 |
武器工业 | 39篇 |
无线电 | 104篇 |
一般工业技术 | 510篇 |
冶金工业 | 88篇 |
原子能技术 | 157篇 |
自动化技术 | 249篇 |
出版年
2024年 | 23篇 |
2023年 | 60篇 |
2022年 | 127篇 |
2021年 | 165篇 |
2020年 | 180篇 |
2019年 | 160篇 |
2018年 | 151篇 |
2017年 | 169篇 |
2016年 | 223篇 |
2015年 | 246篇 |
2014年 | 403篇 |
2013年 | 385篇 |
2012年 | 621篇 |
2011年 | 615篇 |
2010年 | 472篇 |
2009年 | 471篇 |
2008年 | 373篇 |
2007年 | 557篇 |
2006年 | 497篇 |
2005年 | 422篇 |
2004年 | 344篇 |
2003年 | 289篇 |
2002年 | 206篇 |
2001年 | 188篇 |
2000年 | 142篇 |
1999年 | 110篇 |
1998年 | 86篇 |
1997年 | 73篇 |
1996年 | 71篇 |
1995年 | 64篇 |
1994年 | 34篇 |
1993年 | 34篇 |
1992年 | 27篇 |
1991年 | 15篇 |
1990年 | 20篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1973年 | 1篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1959年 | 4篇 |
1954年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有8087条查询结果,搜索用时 10 毫秒
1.
2.
Yan He Kangren Kong Zhengxi Guo Weifeng Fang Zaiqiang Ma Haihua Pan Ruikang Tang Zhaoming Liu 《Advanced functional materials》2021,31(26):2101291
Sensitivity and multi-directional motivation are major two factors for developing optimized humidity-response materials, which are promising for sensing, energy production, etc. Organic functional groups are commonly used as the water sensitive units through hydrogen bond interactions with water molecules in actuators. The multi-coordination ability of inorganic ions implies that the inorganic ionic compounds are potentially superior water sensitive units. However, the particle forms of inorganic ionic compounds produced by classical nucleation limit the number of exposed ions to interact with water. Recent progress on the inorganic ionic oligomers has broken through the limitation of classical nucleation, and realized the molecular-scaled incorporation of inorganic ionic compounds into an organic matrix. Here, the incorporation of hydrophilic calcium carbonate ionic oligomers into hydrophobic poly(vinylidene fluoride) (PVDF) is demonstrated. The ultra-small calcium carbonate oligomers within a PVDF film endow it with an ultra-sensitive, reversible, and bidirectional response. The motivation ability is superior to other bidirectional humidity-actuators at present, which realizes self-motivation on an ice surface, converting the chemical potential energy of the humidity gradient from ice to kinetic energy. 相似文献
3.
High dimensionality in real-world multi-reservoir systems greatly hinders the application and popularity of evolutionary algorithms, especially for systems with heterogeneous units. An efficient hierarchical optimization framework is presented for search space reduction, determining the best water distributions, not only between cascade reservoirs, but also among different types of hydropower units. The framework is applied to the Three Gorges Project (TGP) system and the results demonstrate that the difficulties of multi-reservoir optimization caused by high dimensionality can be effectively solved by the proposed hierarchical method. For the day studied, power output could be increased by 6.79 GWh using an optimal decision with the same amount of water actually used; while the same amount of power could be generated with 2.59 × 107 m3 less water compared to the historical policy. The methodology proposed is general in that it can be used for other reservoir systems and other types of heterogeneous unit generators. 相似文献
4.
5.
Donghai Xu Peng Feng Yang Wang Wanpeng Yang Yu Wang Shaoyan Sun 《American Institute of Chemical Engineers》2022,68(2):e17472
Corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems by a protective water film. In this work, methanol was selected as organic matter, and the influences of vital structural parameters on water film properties and organic matter removal were studied via numerical simulation. The results indicate that higher than 99% of methanol conversion could be obtained and hardly affected by transpiration water layer, transpiring wall porosity and inner diameter. Increasing layer and porosity reduced reactor center temperature, but inner diameter's influence was lower relatively. Water film temperature reduced but coverage rate raised as layer, porosity, and inner diameter increased. Notably, the whole reactor was in supercritical state and coverage rate was only approximately 85% in the case of one layer. Increasing reactor length affected slightly the volume of the upper supercritical zone but enlarged the subcritical zone. 相似文献
6.
Crashworthiness simulation system is one of the key computer-aided engineering (CAE) tools for the automobile industry and implies two potential conflicting requirements: accuracy and efficiency. A parallel crashworthiness simulation system based on graphics processing unit (GPU) architecture and the explicit finite element (FE) method is developed in this work. Implementation details with compute unified device architecture (CUDA) are considered. The entire parallel simulation system involves a parallel hierarchy-territory contact-searching algorithm (HITA) and a parallel penalty contact force calculation algorithm. Three basic GPU-based parallel strategies are suggested to meet the natural parallelism of the explicit FE algorithm. Two free GPU-based numerical calculation libraries, cuBLAS and Thrust, are introduced to decrease the difficulty of programming. Furthermore, a mixed array and a thread map to element strategy are proposed to improve the performance of the test pairs searching. The outer loop of the nested loop through the mixed array is unrolled to realize parallel searching. An efficient storage strategy based on data sorting is presented to realize data transfer between different hierarchies with coalesced access during the contact pairs searching. A thread map to element pattern is implemented to calculate the penetrations and the penetration forces; a double float atomic operation is used to scatter contact forces. The simulation results of the three different models based on the Intel Core i7-930 and the NVIDIA GeForce GTX 580 demonstrate the precision and efficiency of this developed parallel crashworthiness simulation system. 相似文献
7.
Mamata Mukhopadhyay Sameer V Dalvi 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(4):445-454
A supercritical antisolvent (SAS) process is employed for production of solid nanoparticles from atomized droplets of dilute solution in a flowing supercritical carbon dioxide (SC CO2) stream by attaining extremely high, very rapid, and uniform supersaturation. This is facilitated by a two‐way mass transfer of CO2 and solvent, to and from the droplet respectively, rendering rapid reduction in equilibrium solubility of the solid solute in the ternary solution. The present work analyses the degree of supersaturation and nucleation kinetics in a single droplet of cholesterol solution in acetone during its flight in a flowing SC CO2 stream. Both temperature and composition are assumed to be uniform within the droplet, and their variations with time are calculated by balancing the heat and mass transfer fluxes to and from the droplet. The equilibrium solubility of cholesterol with CO2 dissolution has been predicted as being directly proportional to the Partial Molar Volume Fraction (PMVF) of acetone in the binary (CO2–acetone) system. The degree of supersaturation has been simulated up to the time required to attain almost zero cholesterol solubility in the droplet for evaluating the rate of nucleation and the size of the stable critical nuclei formed. The effects of process parameters have been analysed in the pressure range of 7.1–35.0 MPa, temperature range of 313–333 K, SC CO2 flow rate of 0.1136–1.136 mol s?1, the ratio of the volumetric flow rates of CO2‐to‐solution in the range of 100–1000, and the initial mole fraction of cholesterol in acetone solution in the range of 0.0025–0.010. The results confirm an extremely high and rapid increase in degree of supersaturation, very high nucleation rates and stable critical nucleus diameter of the order of a nanometre. Copyright © 2005 Society of Chemical Industry 相似文献
8.
9.
Laurus nobilis L., commonly known as daphne tree, is an evergreen that belongs to the Lauraceae family. Daphne trees produce grape-sized
shiny purplish berries having three parts: flesh, skin, and an inner kernel (single seed). This study examines supercritical
CO2 (SC-CO2) extraction of oil from daphne seeds. The oil yield of ground seeds varied from 14 to 28% depending on the method and particle
size used for oil recovery. Yields were similar for both petroleum ether and SC-CO2 extraction. The extraction yield decreased significantly with increasing particle size. The amount of extract collected increased
exponentially with increasing SC-CO2 pressure. The highest extraction yield was obtained at the highest temperature studied, 75°C. More than 45% of the oil was
lauric acid. SC-CO2 is a viable technique to obtain high-purity L. nobilis L. seed oil, which is a potential ingredient for the cosmetic industry. 相似文献