全文获取类型
收费全文 | 5010543篇 |
免费 | 337373篇 |
国内免费 | 189812篇 |
专业分类
电工技术 | 273548篇 |
技术理论 | 176篇 |
综合类 | 287058篇 |
化学工业 | 706548篇 |
金属工艺 | 239099篇 |
机械仪表 | 271900篇 |
建筑科学 | 301875篇 |
矿业工程 | 122277篇 |
能源动力 | 138589篇 |
轻工业 | 404427篇 |
水利工程 | 105267篇 |
石油天然气 | 158888篇 |
武器工业 | 37953篇 |
无线电 | 540555篇 |
一般工业技术 | 599152篇 |
冶金工业 | 576851篇 |
原子能技术 | 66419篇 |
自动化技术 | 707146篇 |
出版年
2023年 | 42947篇 |
2022年 | 93958篇 |
2021年 | 143476篇 |
2020年 | 107381篇 |
2019年 | 88177篇 |
2018年 | 106053篇 |
2017年 | 117479篇 |
2016年 | 109034篇 |
2015年 | 133077篇 |
2014年 | 182336篇 |
2013年 | 282277篇 |
2012年 | 290972篇 |
2011年 | 330338篇 |
2010年 | 296888篇 |
2009年 | 295596篇 |
2008年 | 301636篇 |
2007年 | 293377篇 |
2006年 | 269641篇 |
2005年 | 227937篇 |
2004年 | 166535篇 |
2003年 | 131939篇 |
2002年 | 122450篇 |
2001年 | 110422篇 |
2000年 | 104386篇 |
1999年 | 91687篇 |
1998年 | 151689篇 |
1997年 | 109725篇 |
1996年 | 90105篇 |
1995年 | 72455篇 |
1994年 | 62692篇 |
1993年 | 55824篇 |
1992年 | 38056篇 |
1991年 | 33722篇 |
1990年 | 32656篇 |
1989年 | 31197篇 |
1988年 | 28621篇 |
1987年 | 25142篇 |
1986年 | 24115篇 |
1985年 | 25609篇 |
1984年 | 22122篇 |
1983年 | 20211篇 |
1982年 | 19105篇 |
1981年 | 19446篇 |
1980年 | 18622篇 |
1979年 | 16657篇 |
1978年 | 16132篇 |
1977年 | 22739篇 |
1976年 | 33616篇 |
1975年 | 14000篇 |
1974年 | 12885篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
In this study, sea bream, sea bass, anchovy and trout were captured and recorded using a digital camera during refrigerated storage for 7 days. In addition, their total viable counts (TVC) were determined on a daily basis. Based on the TVC, each fish was classified as ‘fresh’ when it was <5 log cfu per g, and as ‘not fresh’ when it was >7 log cfu per g. They were uploaded on a web-based machine learning software called Teachable Machine (TM), which was trained about the pupils and heads of the fish. In addition, images of each species from different angles were uploaded to the software in order to ensure the recognition of fish species by TM. The data of the study indicated that the TM was able to distinguish fish species with high accuracy rates and achieved over 86% success in estimating the freshness of the fish species tested. 相似文献
992.
993.
In the present work, the heating performance of a new system combined with a new modified baseboard radiator and fan coil is investigated. Using longitudinal fins with special geometry and also forced airflow at the end of the system causes that at the lower inlet water temperature compared with the conventional models, higher heat output rate be obtained. The heat output rate of the new modified system is obtained by experimental metrology based on the European Standard No. EN-442. Temperature and velocity distribution in the room space is done by simulation of the modified system in the Flovent software. Computational fluid dynamics (CFD) results are validated against experimental results and there is a good agreement between them. Also, the energy consumption of the system during the winter season is calculated in TRANSYS software. Experimental results show that the heat output rate of a new modified heating system with inlet water temperature in the range of 45–55°C is on average 4.17 times higher compared with the conventional model. CFD simulation also showed that the combined system provides good thermal comfort conditions. Energy consumption of the new system reduced about 13% compared with conventional models. 相似文献
994.
In this paper, the stabilization for Schrödinger equation subject to internal damping and boundary disturbance at the control end is investigated. Due to its immeasurability, the nonlinear observer system is designed to obtain the state information, and the existence of weak solution and its convergence for the nonlinear observer system are proved. The feedback control is realized by the backstepping transformation. In addition, the adaptive disturbance rejection control is applied to estimate the disturbance. According to the observer and disturbance estimation, the feedback control is finally designed to stabilize the system asymptotically.
相似文献995.
Khaled Al-Farhany Mohammed A. Alomari Ahmed Al-Saadi Ali Chamkha Hakan F. Öztop Wael Al-Kouz 《亚洲传热研究》2022,51(2):1691-1710
In the current work, numerical simulations are achieved to study the properties and the characteristics of fluid flow and heat transfer of (Cu–water) nanofluid under the magnetohydrodynamic effects in a horizontal rectangular canal with an open trapezoidal enclosure and an elliptical obstacle. The cavity lower wall is grooved and represents the heat source while the obstacle represents a stationary cold wall. On the other hand, the rest of the walls are considered adiabatic. The governing equations for this investigation are formulated, nondimensionalized, and then solved by Galerkin finite element approach. The numerical findings were examined across a wide range of Richardson number (0.1 ≤ Ri ≤ 10), Reynolds number (1 ≤ Re ≤ 125), Hartmann number (0 ≤ Ha ≤ 100), and volume fraction of nanofluid (0 ≤ φ ≤ 0.05). The current study's findings demonstrate that the flow strength increases inversely as the Reynolds number rises, which pushes the isotherms down to the lower part of the trapezoidal cavity. The Nuavg rises as the Ri rise, the maximum Nuavg = 10.345 at Ri = 10, Re = 50, ϕ = 0.05, and Ha = 0; however, it reduces with increasing Hartmann number. Also, it increase by increasing ϕ, at Ri = 10, the Nuavg increased by 8.44% when the volume fraction of nanofluid increased from (ϕ = 0–0.05). 相似文献
996.
This study aims to improve the performances of a solar still single slope using metal oxide nanofluid (Al2O3–water, Cu2O–water, and TiO2–water). The numerical study was carried out for the climatic conditions of Agadir, Morocco, with different concentrations of nanofluids inside a basin equipped with an absorber plate with two different absorptivities. The numerical study is based on thermal balance equations applied on different solar system components and solved using the Runge Kutta method. The numerical model is validated by comparing our results with the literature available data. A comparison study of the effect of these nanofluids on solar still productivity is done. The results show that the productivity of the solar still using nanoparticles Cu2O, TiO2, and Al2O3 are 7.38, 7.1, and 7.064 kg m−2 day−1, respectively. It is obtained that the maximum efficiency of the solar still is found to be 55.27% by using cuprous oxide nanoparticles. Furthermore, an enhancement in solar still productivity of 6.36%, 19.54%, and 33.25% is obtained by dispersing 1%, 3%, and 5% volume fraction of Cu2O nanoparticles in pure water, respectively compared to the conventional solar. Moreover, the impact of the absorptivity of the absorber plate on the solar still effectiveness is investigated. Two types of coatings are considered to change the absorber plate absorptivity. The results indicate that the efficiencies of the solar system are 58.81% and 51.77% using an absorber plate with 0.95 and 0.85 of absorptivity, respectively. 相似文献
997.
Koratagere Revanna Nagaraju Ulavathi Shettar Mahabaleshwar Muddenahalli Siddalinga Prasad Basma Souayeh 《亚洲传热研究》2022,51(6):5288-5301
This article focuses on analytic solutions for Newtonian fluid flow with slip and mass transpiration on a porous stretching sheet using the differential transform method and Pade approximants of an exceptionally nonlinear differential equation. The impacts of different parameters including mass transpiration (suction/injection), Navier's slip, and Darcy number parameters on the velocity of the liquid and tangential stress are discussed. A comprehensive comparison of our results with the previous one in the literature is made, and the results showed good agreement. An investigation is conducted of a combination of magnetic liquids that are conceivably pertinent for wound medicines, skin repair, and astute coatings for natural gadgets. It is found that there is a decrease in the velocity profiles and the boundary layer thickness for the case of suction. 相似文献
998.
Xian Yu Wang Cuicui Wang Ge Smith Leemiller Cheng Haitao 《Holz als Roh- und Werkstoff》2022,80(2):355-365
European Journal of Wood and Wood Products - To obtain the optimum balance between performance and cost, white mud (lime mud) was incorporated into the shell layer of core–shell structured... 相似文献
999.
1000.
为深入了解云南澜沧江流域不同茶区晒青茶的品质差异,选取比较澜沧、双江2个茶区的24个乡镇晒青茶样,采用感官审评与品质理化成分检测,分析不同茶区晒青茶主要理化成分和感官品质方面存在的差异。结果表明:澜沧、双江2个茶区晒青茶的茶多酚平均值分别为24.43%、23.18%;游离氨基酸平均值分别为2.72%、3.97%;咖啡碱平均值分别为4.90%、4.48%;水浸出物平均值分别为45.67%、44.29%;酚氨比均值分别为9.40、6.07。澜沧、双江2个茶区不同产地的晒青茶茶多酚、游离氨基酸、咖啡碱、水浸出物和酚氨比之间存在一定差异。不同的内含化学成分,使各茶区的晒青茶感官品质明显不同。澜沧茶区的晒青茶滋味整体较醇和、稍涩,部分稍带花香与焦味;双江茶区的晒青茶整体滋味较浓醇、微涩带苦,部分平和。 相似文献