全文获取类型
收费全文 | 45987篇 |
免费 | 2574篇 |
国内免费 | 1270篇 |
专业分类
电工技术 | 1442篇 |
技术理论 | 4篇 |
综合类 | 2771篇 |
化学工业 | 11283篇 |
金属工艺 | 6502篇 |
机械仪表 | 1191篇 |
建筑科学 | 6332篇 |
矿业工程 | 1596篇 |
能源动力 | 995篇 |
轻工业 | 4169篇 |
水利工程 | 1792篇 |
石油天然气 | 1670篇 |
武器工业 | 145篇 |
无线电 | 831篇 |
一般工业技术 | 3429篇 |
冶金工业 | 4788篇 |
原子能技术 | 249篇 |
自动化技术 | 642篇 |
出版年
2024年 | 164篇 |
2023年 | 427篇 |
2022年 | 1081篇 |
2021年 | 1286篇 |
2020年 | 1203篇 |
2019年 | 851篇 |
2018年 | 860篇 |
2017年 | 1110篇 |
2016年 | 1133篇 |
2015年 | 1269篇 |
2014年 | 2422篇 |
2013年 | 2320篇 |
2012年 | 3096篇 |
2011年 | 3327篇 |
2010年 | 2831篇 |
2009年 | 2957篇 |
2008年 | 2246篇 |
2007年 | 3116篇 |
2006年 | 3084篇 |
2005年 | 2605篇 |
2004年 | 2234篇 |
2003年 | 2065篇 |
2002年 | 1691篇 |
2001年 | 1323篇 |
2000年 | 1048篇 |
1999年 | 803篇 |
1998年 | 624篇 |
1997年 | 500篇 |
1996年 | 385篇 |
1995年 | 367篇 |
1994年 | 257篇 |
1993年 | 193篇 |
1992年 | 183篇 |
1991年 | 146篇 |
1990年 | 89篇 |
1989年 | 119篇 |
1988年 | 68篇 |
1987年 | 64篇 |
1986年 | 46篇 |
1985年 | 44篇 |
1984年 | 43篇 |
1983年 | 35篇 |
1982年 | 18篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1966年 | 9篇 |
1965年 | 7篇 |
1964年 | 9篇 |
1959年 | 7篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
992.
ZnO nanorod arrays were synthesized by chemical bath deposition. After heat treatment in hydrogen or air, Ag nanoparticles were deposited on ZnO nanorod arrays by photo-reduction method. The size of Ag nanoparticles as well as the surface morphology, structure, composition, and optical property of ZnO nanorod arrays before and after the deposition of Ag nanoparticles were characterized by SEM, XRD, EDS, and UV/VIS/NIR spectrophotometer. As compared to the samples with heat treatment in air or without heat treatment, the ZnO nanorod arrays after heat treatment in hydrogen allowed Ag nanoparticles to be deposited more uniformly, densely, and numerously. Also, they exhibited higher efficiency for the visible light-driven photocatalytic degradation of Rhodamine 6G (R6G) dye. The effects of the amount of Ag nanoparticles, initial dye concentration, and temperature on the photocatalytic degradation efficiency were investigated. Furthermore, they also exhibited better surface-enhanced Raman scattering property for the detection of R6G dyes. 相似文献
993.
Mohannad Qurie Jehad Abbadi Laura Scrano Gennaro Mecca Sabino A. Bufo Mustafa Khamis Rafik Karaman 《International journal of molecular sciences》2013,14(7):13808-13825
The reverse osmosis (RO) brine generated from the Al-Quds University wastewater treatment plant was treated using an epuvalisation system. The advanced integrated wastewater treatment plant included an activated sludge unit, two consecutive ultrafiltration (UF) membrane filters (20 kD and 100 kD cutoffs) followed by an activated carbon filter and a reverse osmosis membrane. The epuvalisation system consisted of salt tolerant plants grown in hydroponic channels under continuous water flowing in a closed loop system, and placed in a greenhouse at Al-Quds University. Sweet basil (Ocimum basilicum) plants were selected, and underwent two consecutive hydroponic flowing stages using different brine-concentrations: an adaptation stage, in which a 1:1 mixture of brine and fresh water was used; followed by a functioning stage, with 100% brine. A control treatment using fresh water was included as well. The experiment started in April and ended in June (2012). At the end of the experiment, analysis of the effluent brine showed a remarkable decrease of electroconductivity (EC), PO43−, chemical oxygen demand (COD) and K+ with a reduction of 60%, 74%, 70%, and 60%, respectively, as compared to the influent. The effluent of the control treatment showed 50%, 63%, 46%, and 90% reduction for the same parameters as compared to the influent. Plant growth parameters (plant height, fresh and dry weight) showed no significant difference between fresh water and brine treatments. Obtained results suggest that the epuvalisation system is a promising technique for inland brine treatment with added benefits. The increasing of channel number or closed loop time is estimated for enhancing the treatment process and increasing the nutrient uptake. Nevertheless, the epuvalisation technique is considered to be simple, efficient and low cost for inland RO brine treatment. 相似文献
994.
Annelies Gonnissen Sofie Isebaert Karin Haustermans 《International journal of molecular sciences》2013,14(7):13979-14007
Activation of Hedgehog (Hh) signaling is implicated in the development and progression of several tumor types, including prostate cancer, which is still the most common non-skin malignancy and the third leading cause of cancer-related mortality in men in industrialized countries worldwide. Several studies have indicated that the Hh pathway plays a crucial role in the development as well as in the progression of this disease to more aggressive and even therapy-resistant disease states. Moreover, preclinical data have shown that inhibition of Hh signaling has the potential to reduce prostate cancer invasiveness and metastatic potential. Clinical trials investigating the benefit of Hh inhibitors in patients with prostate cancer have recently been initiated. However, acquired drug resistance has already been observed in other tumor types after long-term Hh inhibition. Therefore, combining Hh inhibitors with ionizing radiation, chemotherapy or other molecular targeted agents could represent an alternative therapeutic strategy. In this review, we will highlight the role of Hh signaling in the development and progression of prostate cancer and summarize the different therapeutic applications of Hedgehog inhibition. 相似文献
995.
Nina Pauline Holzapfel Boris Michael Holzapfel Simon Champ Jesper Feldthusen Judith Clements Dietmar Werner Hutmacher 《International journal of molecular sciences》2013,14(7):14620-14646
Lycopene is a phytochemical that belongs to a group of pigments known as carotenoids. It is red, lipophilic and naturally occurring in many fruits and vegetables, with tomatoes and tomato-based products containing the highest concentrations of bioavailable lycopene. Several epidemiological studies have linked increased lycopene consumption with decreased prostate cancer risk. These findings are supported by in vitro and in vivo experiments showing that lycopene not only enhances the antioxidant response of prostate cells, but that it is even able to inhibit proliferation, induce apoptosis and decrease the metastatic capacity of prostate cancer cells. However, there is still no clearly proven clinical evidence supporting the use of lycopene in the prevention or treatment of prostate cancer, due to the only limited number of published randomized clinical trials and the varying quality of existing studies. The scope of this article is to discuss the potential impact of lycopene on prostate cancer by giving an overview about its molecular mechanisms and clinical effects. 相似文献
996.
用水热合成和铵交换法制备系列氢型丝光沸石(H-MOR),通过水热碱蚀与碱溶滤联合处理对H-MOR样品进行选择性脱硅和介孔改性.研究H-MOR骨架Si/Al比对改性沸石的介孔结构、酸性和水热稳定性的影响.N2吸附结果表明,碱处理沸石的介孔率随H-MOR硅铝比减少而增加;典型样品(n(Si) /n(Al) 9.43)具有附加介孔结构,介孔体积可达0.082 cm3/g,最可几孔径为4.6 nm;SEM观察显示,改性沸石的介孔结构源于脱硅产生的结构缺陷,晶内介孔呈无序分布;ICP和EDX分析证实,联合碱处理促进H-MOR晶体选择性脱硅(脱硅率均大于93.1%);水热稳定性和NH3-TPD数据表明,介孔改性丝光沸石较好地保持了前体的结晶性和水热稳定性,其酸性与对应H-MOR沸石相匹配.骨架硅铝比影响改性MOR沸石的介孔率,但与沸石脱硅率无相关性. 相似文献
997.
为了提高聚合硫酸铁的混凝性能,增强对污水的去除能力.利用自制交流变频磁化装置,对聚合硫酸铁溶液进行磁化处理,以铁盐水解形态Feb为指标,交流变频电磁场的频率、电压、电流及磁化时间为实验因素,对电磁场作用下的聚合硫酸铁溶液进行形态分析,并与非磁化的PFS溶液进行对比;以高炉煤气洗涤水为实验水样,通过混凝试验对比聚合硫酸铁溶液磁化前后的出水浊度及COD值.研究结果表明:电磁场作用下的聚合硫酸铁溶液的形态分布发生了变化,与非磁化相比,Feb百分比含量增加了1倍,Fec百分比含量减少了1/3,且当频率为300 Hz、电压为100 V、电流为0.8A、磁化时间为2 min时Feb的百分比含量达到最大;电磁场能明显提高聚合硫酸铁的混凝性能,与非磁化的聚合硫酸铁溶液相比出水浊度与COD值降为原来的一半,投药量节省了1倍. 相似文献
998.
文章对近年来出现的SHARON、SND、ANAMMOX、CANON、OLAND等生物脱氮新工艺的基本原理、特点和研究现状进行了对比,通过SHARON-ANAMMOX工艺在合成氨废水污水处理装置使用的工程实例,研究了含氨废水在生物脱氮工艺中应关注技术要点及操作注意事项。 相似文献
999.
1000.