全文获取类型
收费全文 | 75342篇 |
免费 | 8351篇 |
国内免费 | 5203篇 |
专业分类
电工技术 | 6377篇 |
技术理论 | 1篇 |
综合类 | 7228篇 |
化学工业 | 10843篇 |
金属工艺 | 4840篇 |
机械仪表 | 5139篇 |
建筑科学 | 5654篇 |
矿业工程 | 2994篇 |
能源动力 | 2173篇 |
轻工业 | 6918篇 |
水利工程 | 2411篇 |
石油天然气 | 3027篇 |
武器工业 | 994篇 |
无线电 | 8104篇 |
一般工业技术 | 7383篇 |
冶金工业 | 2960篇 |
原子能技术 | 1234篇 |
自动化技术 | 10616篇 |
出版年
2024年 | 331篇 |
2023年 | 1162篇 |
2022年 | 2721篇 |
2021年 | 3623篇 |
2020年 | 2747篇 |
2019年 | 2042篇 |
2018年 | 2112篇 |
2017年 | 2366篇 |
2016年 | 2139篇 |
2015年 | 3325篇 |
2014年 | 4244篇 |
2013年 | 4948篇 |
2012年 | 5989篇 |
2011年 | 6249篇 |
2010年 | 5710篇 |
2009年 | 5702篇 |
2008年 | 5668篇 |
2007年 | 5387篇 |
2006年 | 4783篇 |
2005年 | 3802篇 |
2004年 | 2812篇 |
2003年 | 2067篇 |
2002年 | 2193篇 |
2001年 | 1963篇 |
2000年 | 1520篇 |
1999年 | 912篇 |
1998年 | 457篇 |
1997年 | 365篇 |
1996年 | 339篇 |
1995年 | 280篇 |
1994年 | 214篇 |
1993年 | 170篇 |
1992年 | 87篇 |
1991年 | 77篇 |
1990年 | 67篇 |
1989年 | 62篇 |
1988年 | 44篇 |
1987年 | 32篇 |
1986年 | 30篇 |
1985年 | 18篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1980年 | 38篇 |
1979年 | 19篇 |
1966年 | 3篇 |
1965年 | 7篇 |
1959年 | 12篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Nitrile rubber (NBR) blends with excellent performance have always been a hot research topic in petroleum field. Due to the excellent performance and compatibility of polyamide 6 (PA6), it provides an opportunity for the preparation of high-performance NBR/PA6 blends. In this article, NBR/PA6 blends were prepared by the three-step molding process. Experimentally, it was found that PA6 has a prominent reinforcement effect in NBR matrix. The variation of this mechanical property was investigated from different aspects of the crystal structure, crystallinities, phase morphology, and so on. It can be cleared that the formation of fibrous structure of PA6 phase is the main factor for reinforcement of the polymer blends. Meanwhile, the formation mechanism of the special phase structure induced by the three-step process is deeply expounded and its structural evolution schematic is established. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47472. 相似文献
12.
介绍了备料车间布袋除尘项目的基本情况。对项目的背景、设计,以及技术创新点进行了较为详细的阐述。通过项目技术参数、效益、市场竞争力的比较分析,评估了项目应用情况。对项目投产前后的运行成本进行了分析,经济效益明显。 相似文献
13.
14.
Baofeng Hou Hong He Ruixiu Jia Meilong Fu Yanbin Cao Shaoqun He Liwen Luo Youqing Huang 《应用聚合物科学杂志》2019,136(10):47161
The synthesis and performance of a novel temperature-tolerant foamed resin for enhanced oil recovery were investigated using various methods, including infrared, NMR, scanning electron microscopy (SEM), and displacement experiments. Polycondensation of furfuryl alcohol prepolymers was confirmed by the infrared and NMR results. The poor temperature tolerance of furfuryl alcohol prepolymers after gelation at high temperatures is mainly due to the fracture of furan rings. The addition of ester additives is an effective method of increasing the temperature tolerance of the prepared foamed resins and can effectively reduce the weight-loss rate of the polycondensation products. The SEM results show that the skeleton structure of the foamed resin remains intact after high-temperature treatment. Thus, the novel plugging agent system has excellent thermal stability and still has a high strength (>0.8 MPa) after high-temperature aging treatment for 40 days, giving the prepared foamed resin a good plugging performance (plugging rate > 91%) at 250 °C. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47161. 相似文献
15.
16.
在伯克氏菌Bth264野生株产新型抗癌药物Thailandepsin A以及调节基因tdp R正向调控Thailandepsin A生物合成的基础上,利用基因工程菌Bth264/p BMTL3-tdp R发酵生产Thailandepsin A,以提高产量。以0.5%乳糖为诱导剂,确定最佳诱导条件:发酵15 h添加乳糖,诱导时间6 h;通过单因素实验,确定葡萄糖和胰蛋白胨作为碳氮源、装液量65/250 m L以及接种量1%;同时结合优化发酵培养基进行发酵,Thailandepsin A产量达到252.14 mg·L-1,比优化前的产量提高56%;另外在发酵过程中,添加大孔树脂HP-20原位吸附产物,Thailandepsin A产量可达283.75 mg·L-1,比不加树脂提高13.8%;最后,基于RT-PCR和比较Ct值法,基因工程菌和野生菌相比,Thailandepsin A生物合成基因tdp B、tdp C1的转录水平分别提高11.4倍和6.0倍,对应的产量增加4.6倍,从而在很大程度上说明调节基因tdp R的过表达促进生物合成基因转录水平的提高以及产量的增加。 相似文献
18.
19.
How to improve the sensitivity of the temperature-sensing luminescent materials is one of the most important objects currently. In this work, to obtain high sensitivity and learn the corresponding mechanism, the rare earth (RE) ions doped Y4.67Si3O13 (YS) phosphors were developed by solid-state reaction. The phase purity, structure, morphology and luminescence characteristics were evaluated by XRD, TEM, emission spectra, etc. The change of the optical bandgaps between the host and RE-doped phosphors was found, agreeing with the calculation results based on density-functional theory. The temperature-dependence of the upconversion (UC) luminescence revealed that a linear relationship exists between the fluorescence intensity ratio of Ho3+ and temperature. The theoretical resolution was evaluated. High absolute (0.083 K−1) and relative (3.53% K−1 at 293 K) sensitivities have been gained in the YS:1%Ho3+, 10%Yb3+. The effect of the Yb3+ doping concentration and pump power on the sensitivities was discussed. The pump-power–dependence of the UC luminescence indicated the main mechanism for high sensitivities in the YS:1%Ho3+, 10%Yb3+. Moreover, the decay-lifetime based temperature sensing was also evaluated. The above results imply that the present phosphors could be promising candidates for temperature sensors, and the proposed strategies are instructive in exploring other new temperature sensing luminescent materials. 相似文献
20.
Shuyi Fu Wenrui Feng Ying Jia Tielong Deng Wenzhong Wang Guling Zhang Junli Fu 《International Journal of Hydrogen Energy》2021,46(21):11544-11555
ZnO/Cu2S nanotube arrays are fabricated firstly by a facile and capping-agent-free method, and the photo-electrochemical performance has been studied systematically. The results show that ZnO/Cu2S nanotube arrays achieve enhanced photo-electrochemical water splitting performance and the photocurrent densities of ZnO/Cu2S are 7.9 times than that of ZnO at 0 V versus Ag/AgCl. The performance of the ZnO/Cu2S nanotube arrays can be adjusted by changing the amount of Cu2S microcrystals. The results confirm that the enhanced photo-electrochemical performance of ZnO/Cu2S is due to the significantly improved visible light absorption, effective separation of photo-induced carriers due to the well band energy match and the formed p-n junction between ZnO and Cu2S. 相似文献