全文获取类型
收费全文 | 54242篇 |
免费 | 4184篇 |
国内免费 | 2036篇 |
专业分类
电工技术 | 2822篇 |
技术理论 | 5篇 |
综合类 | 3019篇 |
化学工业 | 9391篇 |
金属工艺 | 3285篇 |
机械仪表 | 3259篇 |
建筑科学 | 3838篇 |
矿业工程 | 1762篇 |
能源动力 | 1695篇 |
轻工业 | 3782篇 |
水利工程 | 876篇 |
石油天然气 | 3801篇 |
武器工业 | 396篇 |
无线电 | 5837篇 |
一般工业技术 | 6486篇 |
冶金工业 | 3055篇 |
原子能技术 | 659篇 |
自动化技术 | 6494篇 |
出版年
2024年 | 244篇 |
2023年 | 895篇 |
2022年 | 1642篇 |
2021年 | 2335篇 |
2020年 | 1698篇 |
2019年 | 1468篇 |
2018年 | 1684篇 |
2017年 | 1804篇 |
2016年 | 1618篇 |
2015年 | 2123篇 |
2014年 | 2718篇 |
2013年 | 3145篇 |
2012年 | 3337篇 |
2011年 | 3639篇 |
2010年 | 3218篇 |
2009年 | 2889篇 |
2008年 | 2830篇 |
2007年 | 2752篇 |
2006年 | 2917篇 |
2005年 | 2486篇 |
2004年 | 1556篇 |
2003年 | 1360篇 |
2002年 | 1283篇 |
2001年 | 1008篇 |
2000年 | 1212篇 |
1999年 | 1496篇 |
1998年 | 1190篇 |
1997年 | 1019篇 |
1996年 | 1020篇 |
1995年 | 898篇 |
1994年 | 709篇 |
1993年 | 471篇 |
1992年 | 376篇 |
1991年 | 301篇 |
1990年 | 242篇 |
1989年 | 198篇 |
1988年 | 177篇 |
1987年 | 111篇 |
1986年 | 95篇 |
1985年 | 64篇 |
1984年 | 58篇 |
1983年 | 40篇 |
1982年 | 32篇 |
1981年 | 30篇 |
1980年 | 17篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 14篇 |
1975年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
本文主要阐述了通过爆炸焊接和热轧的方法,研制成功可焊性良好的且具有较好强度、韧性与综合性能的双相耐应力腐蚀的不锈复合钢板。还将热轧与热处理的两种试验作了较全面的常规、特殊检验试验,结果完全达到使用要求。 相似文献
12.
新型超微晶软磁合金FePCCuMoSi微观结构缺陷的正电子湮没研究 总被引:1,自引:0,他引:1
用正电子湮没方法研究了新型超微晶软磁合金的微观结构缺陷,样品选用的是在不同温度下退火的Fe81P12C3Cu1Mo0.5Si2.5合金,结果表明,合金的微观结构构陷大小,密度随退火温度有规律地变化,这种现象可能与非晶的晶化过程有关。 相似文献
13.
14.
This paper presents an artificial intelligence approach of using evolutionary programming to estimate the transient and subtransient parameters of a generator under normal operation. The estimation using evolutionary programming is compared with that using a corrected extended Kalman filter. The comparisons with both simulation and micromachine test results show that evolutionary programming is robust to search the real values of parameters even when the data are highly contaminated by noise, while with the extended Kalman filter, the estimation tends to diverge with such data 相似文献
15.
回顾了体制、制度的改革和科学技术的发展给十局带来的巨大变化,就十局当前改革任务从理顺产权关系、进一步完善内部治理结构、继续深化三项制度改革、实施科教兴局战略等四个方面提出了看法和意见。 相似文献
16.
Tramadol hydrochloride is a centrally acting synthetic analgesic in widespread clinical use. Despite different degrees of opioid-like characteristics in preclinical tests, it is characterized by lack of full naloxone reversibility or naloxone-precipitated withdrawal in humans. To investigate this apparent discrepancy, the present study measured the affinity of tramadol (and its enantiomers) and an active O-desmethyl metabolite (M1) (and its enantiomers) to cloned human opioid receptors of the mu, delta and kappa type stably expressed in HN9.10 neuroblastoma cells. At mu sites, the Ki values for tramadol, its (+) and (-) enantiomers, M1, and its (+) and (-) enantiomers were 17000, 15700, 28800, 3190, 153 and 9680 nM, respectively, compared to 7.1 nM for morphine. These results are consistent with the suggestion of a non-opioid contribution to the clinical profile of tramadol. 相似文献
17.
Voltage stability problems have been one of the major concerns for electric utilities as a result of system heavy loading. This paper reports on an investigation on the application of ANNs in voltage stability assessment. A multilayer feedforward artificial neural network (ANN) with error backpropagation learning is proposed for calculation of voltage stability margins (VSM). Based on the energy method, a direct mapping relation between power system loading conditions and the VSMs is set up via the ANN. A systematic method for selecting the ANN's input variables was developed using sensitivity analysis. The effects of ANN's training pattern sensitivity problems were also studied by dividing system operating conditions into several loading levels based on sensitivity analysis. Extensive testing of the proposed ANN-based approach indicate its viability for power system voltage stability assessment. Simulation results on five test systems are reported in the paper 相似文献
18.
Z Ma S Ramanadham K Kempe Z Hu J Ladenson J Turk 《Canadian Metallurgical Quarterly》1996,1308(2):151-163
We prepared polymers having a phospholipid polar group, poly [omega-methacryloyloxyalkyl phosphorylcholine (MAPC)-co-n-butyl methacrylate(BMA)], as new biomedical materials and evaluated their blood compatibility with attention to protein adsorption and platelet adhesion. The total amount of proteins adsorbed on the polymer surface from human plasma was determined, and the distribution of adsorbed proteins on the plasma-contacting surface was analyzed. The amount of proteins adsorbed on every poly (MAPC-co-BMA) was small compared with that observed on polymers without the phospholipid polar group. However, there was no significant difference in the amount of adsorbed proteins on the poly(MAPC-co-BMA) even when the methylene chain length between the phospholipid polar group and the backbone in the MAPC moiety was altered. Platelet adhesion on the polymer surface from a platelet suspension in a buffered solution was evaluated with and without plasma treatment on the surface. When a rabbit platelet suspension was brought into contact with the poly(BMA) surface after treatment with plasma, many platelets adhered and aggregated. However, a reduced amount of platelet adhered on the poly(BMA) was found in the case of direct contact with the platelet suspension. On the other hand, the poly(MAPC-co-BMA)s could inhibit platelet adhesion under both conditions. Based on these results, it can be concluded that the proteins adsorbed on the surface play an important role in determining the platelet adhesion and suppression of the protein adsorption on the surface, which is one of the most significant ways of inhibiting platelet adhesion. 相似文献
19.
Yong Ma Yong‐zhen Peng Xiao‐lian Wang Shu‐ying Wang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(10):1118-1124
The laboratory scale anaerobic–anoxic–aerobic (A2O) process fed with synthetic brewage wastewater was designed to investigate the effects of changing feed C/P ratio on the performance of biological nutrient removal (BNR) processes. In the experiment, the influent chemical oxygen demand (COD) concentration was kept at approximately 300 mg L?1 while the total phosphorus concentration was varied to obtain the desired C/P ratio. Results showed that when the C/P ratio was lower than 32, phosphorus removal efficiency increased as C/P ratio increased linearly, while when the C/P ratio was higher than 32, the P removal efficiency was maintained at 90–98%, and effluent P concentration was lower than 0.5 mg L?1. However, regardless of the C/P ratio, excellent COD removal (90% or higher) and good total nitrogen removal (75–84%) were maintained throughout the experiments. It was also found that very good linear correlation was obtained between COD uptake per unit P released in the anaerobic zone and C/P ratio. In addition, the P content in the wasted activated sludge increased with the decrease in the C/P ratio. Based on the results, it was recommended that the wastewater C/P ratio and its effects be incorporated into BNR design and operational procedures, appropriate C/P ratios were used to achieve the effluent treatment goals. Copyright © 2005 Society of Chemical Industry 相似文献
20.