全文获取类型
收费全文 | 5527篇 |
免费 | 318篇 |
国内免费 | 52篇 |
专业分类
电工技术 | 78篇 |
综合类 | 13篇 |
化学工业 | 1133篇 |
金属工艺 | 126篇 |
机械仪表 | 164篇 |
建筑科学 | 123篇 |
矿业工程 | 29篇 |
能源动力 | 295篇 |
轻工业 | 460篇 |
水利工程 | 59篇 |
石油天然气 | 42篇 |
无线电 | 637篇 |
一般工业技术 | 1281篇 |
冶金工业 | 546篇 |
原子能技术 | 66篇 |
自动化技术 | 845篇 |
出版年
2024年 | 21篇 |
2023年 | 117篇 |
2022年 | 269篇 |
2021年 | 434篇 |
2020年 | 266篇 |
2019年 | 297篇 |
2018年 | 315篇 |
2017年 | 271篇 |
2016年 | 264篇 |
2015年 | 173篇 |
2014年 | 224篇 |
2013年 | 429篇 |
2012年 | 259篇 |
2011年 | 288篇 |
2010年 | 200篇 |
2009年 | 161篇 |
2008年 | 152篇 |
2007年 | 135篇 |
2006年 | 118篇 |
2005年 | 85篇 |
2004年 | 65篇 |
2003年 | 79篇 |
2002年 | 61篇 |
2001年 | 52篇 |
2000年 | 49篇 |
1999年 | 64篇 |
1998年 | 155篇 |
1997年 | 129篇 |
1996年 | 98篇 |
1995年 | 73篇 |
1994年 | 61篇 |
1993年 | 56篇 |
1992年 | 36篇 |
1991年 | 43篇 |
1990年 | 35篇 |
1989年 | 31篇 |
1988年 | 25篇 |
1987年 | 29篇 |
1986年 | 34篇 |
1985年 | 32篇 |
1984年 | 26篇 |
1983年 | 29篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1978年 | 16篇 |
1977年 | 17篇 |
1976年 | 23篇 |
1973年 | 8篇 |
1972年 | 8篇 |
排序方式: 共有5897条查询结果,搜索用时 15 毫秒
991.
Ranajoy Bhattacharya Naveen Kr Sahu Arani Ali Khan Hasina Khatun A.K. Sinha 《Fusion Engineering and Design》2013,88(4):253-257
The paper presents the electrical and thermo-mechanical design of single stage beam recovery system for 120 GHz, 1 MW gyrotron. The electrical study shows that the cylindrical shape single stage beam recovery system enhances the efficiency by 66.26%. The maximum power deposited to collector in depressed collector operation is 0.48 MW for electronic efficiency, 30% and 1.44 MW for DC electron beam. The thermo-mechanical analysis has been performed to evaluate the water cooling system. The cooling system has capability of accommodating a peak wall loading, 0.9 kW/cm2 at flow rate of 1500 l/min for safe operating time, 60 ms. Further, a high voltage analysis is also carried out to appraise the electric field distribution in the collector. 相似文献
992.
An improved method of DNA preparation for PCR‐based detection of Brucella in raw camel milk samples from Riyadh region and its comparison with immunological methods
下载免费PDF全文
![点击此处可从《Journal of Food Safety》网站下载免费的PDF全文](/ch/ext_images/free.gif)
993.
Combined effects of pulsed electric field and ultrasound on bioactive compounds and microbial quality of grapefruit juice
下载免费PDF全文
![点击此处可从《Journal of Food Processing and Preservation》网站下载免费的PDF全文](/ch/ext_images/free.gif)
994.
995.
Md. Anamul Hoque Md. Masud Alam Mohammad Robel Molla Shahed Rana Malik Abdul Rub Mohammad A. Halim Mohammed Abdullah Khan Farida Akhtar 《中国化学工程学报》2018,26(1):159-167
Interaction between beta-lactum antibiotic drug ciprofloxacin hydrochloride(CFH)and cationic surfactant cetyltrimethylammonium bromide(CTAB)was performed conductometrically in aqueous as well as in the occurrence of different salts(NaCl,KCl as well as NH_4Cl)over the temperature range of 298.15–323.15 K at the regular interval of 5 K.CFH drug has been suggested for the treatment of bacterial infections such as urinary tract infections and acute sinusitis.A clear critical micelle concentration(CMC)was obtained for pure CTAB as well as(CFH+CTAB)mixed systems.The decrease in CMC values of CTAB caused by the addition of CFH reveals the existence of the interaction between the components and therefore it is the indication of micelle formation at lower concentration of CTAB and their CMC values further decrease in attendance of salts.A nonlinear behavior in the CMC versus T plot was observed in all the cases.The ΔG_m~0 values are found to be negative in present study systems demonstrated the stability of the solution.The values of ΔH_m~0 and ΔS_m~0 reveal the existence of hydrophobic and electrostatic interactions between CFH and CTAB.The thermodynamic properties of transfer for the micellization were also evaluated and discussed in detail.Molecular dynamic simulation disclosed that environment of water and salts have impact on the hydrophobic interaction between CFH and CTAB.In water and salts,CTAB adopts spherical micelle in which charged hydrophilic groups are interacted with waters whereas hydrophobic tails form the core of the micelle.This hydrophobic core region is highly conserved and protected.In addition,micelle formation is more favorable in aqueous Na Cl solution than other solutions. 相似文献
996.
Asiful H. Seikh Hossam Halfa Muneer Baig Sohail M. A. Khan 《Journal of Materials Engineering and Performance》2017,26(4):1589-1597
In this study, two different grades (M23 and M29) of cobalt-free low nickel maraging steel have been produced through electroslag remelting (ESR) process. The corrosion resistance of these ESR steels was investigated in 1 M H2SO4 solution using linear potentiodynamic polarization (LPP) and electrochemical impedance spectroscopy (EIS) techniques. The experiments were performed for different immersion time and solution temperature. To evaluate the corrosion resistance of the ESR steels, some significant characterization parameters from LPP and EIS curves were analyzed and compared with that of conventional C250 maraging steel. Irrespective of measurement techniques used, the results show that the corrosion resistance of the ESR steels was higher than the C250 steel. The microstructure of ESR steels was composed of uniform and well-distributed martensite accompanied with little amount of retained austenite in comparison with C250 steel. 相似文献
997.
Improved hydrological projections and reservoir management in the Upper Indus Basin under the changing climate
下载免费PDF全文
![点击此处可从《Water and Environment Journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The availability of water resources plays an important role for the economy of a country. The nexus of energy‐food‐water are interlinked and of particular importance in the uncertain environment of developing countries. In Pakistan, agriculture contributes 25% to the gross domestic product. The Indus River contributes 44% of the available water to irrigation of crops and the ecosystem, and currently produces 5,112 MW electricity, with the potential to produce 38,602 MW electricity. This makes it important to investigate the status of water availability in the Upper Indus Basin under existing emission scenarios. In this study, the future availability of water is projected for the Indus River under the A2, B2, RCP4.5 and RCP8.5 emission scenarios. A meta‐analysis has been conducted to present a combined picture by combining the results from the emission scenarios. Our meta‐analysis shows higher confidence in RCPs projections. The results show that suffcient water will be available in the Indus River that will meet the demands of water in future but there will be scarcity of water in some months under each scenario. However, by proper management and optimum utilisation of the available water, this scarcity can be resolved. 相似文献
998.
Older wastewater systems often contain vitrified clay pipes and these pipes are responsible for a significant proportion of blockages. From previous research and site experience, it is known that age, installation period, pipe length, diameter, depth and joint type affect the risk of blockage. Using statistical analysis we extend this list of variables to include soil type, road/rail proximity and road type. The analysis is based on blockage data for 43,976 vitrified clay pipes over a 7 year period. A Cox proportional hazards modelling (PHM) approach using established and new explanatory variables finds that pipe depth, pipe length, pipe gradient, pipe diameter, submergence in water, joint type, pipe installation decade, soil type, road proximity to the pipe, pipe purpose, land use code and road type are associated with risk of blockage. Pipes with the highest risk of failure due to blockage are identified and their locations and risk level are visually represented on a colour coded map. This analysis approach can be used by asset managers working in cost-constrained environments to appropriately target inspection, plan maintenance and replacement programs. 相似文献
999.
Siddiqui Pirzada Jamal Ahmed Khan Adnan Uddin Nizam Khaliq Saima Rasheed Munawwer Nawaz Shazia Dar Ahsana Hanif Muhammad 《Food science and biotechnology》2017,26(4):1055-1062
Food Science and Biotechnology - Recently, considerable attention has been paid to drug exploration from natural sources for treating memory loss, a major manifestation of various neurodegenerative... 相似文献
1000.
Shahid-ul-Islam Luqman Jameel Rather Mohd Shabbir Mohd Nadeem Bukhari Mohd Shahid Mohd Ali Khan 《Journal of Natural Fibers》2017,14(4):586-596
This study was undertaken to propose alternative use for teak leaves, a timber industry byproduct, as potential dyeing source for wool fibers. The coloring potential of anthraquinone colorants from teak leaves were studied on wool with pre-mordanting method using double and triple mix metal salt combinations (ferrous sulphate, stannous chloride and potassium aluminum sulphate) as mordants. Thirty-six sober and elegant shades were developed on wool by varying the type of metal involved in combination as well as concentration of the dye. The hue of color developed ranged from light orange—brown to dark brown. The color strength (K/S) has been found to be very good in dyed woolen yarn samples and particularly was highest for iron + alum combination. Color fastness with respect to light exposure washing, rubbing for the developed shades ranged between good to very good, which confirmed the possibility of using waste leaves of Tectona grandis as a source of effective brown natural dye. 相似文献