全文获取类型
收费全文 | 22797篇 |
免费 | 1818篇 |
国内免费 | 904篇 |
专业分类
电工技术 | 1277篇 |
技术理论 | 2篇 |
综合类 | 1485篇 |
化学工业 | 3706篇 |
金属工艺 | 1188篇 |
机械仪表 | 1460篇 |
建筑科学 | 1918篇 |
矿业工程 | 667篇 |
能源动力 | 627篇 |
轻工业 | 1479篇 |
水利工程 | 404篇 |
石油天然气 | 1358篇 |
武器工业 | 190篇 |
无线电 | 2521篇 |
一般工业技术 | 2754篇 |
冶金工业 | 1072篇 |
原子能技术 | 209篇 |
自动化技术 | 3202篇 |
出版年
2024年 | 78篇 |
2023年 | 353篇 |
2022年 | 591篇 |
2021年 | 839篇 |
2020年 | 648篇 |
2019年 | 482篇 |
2018年 | 617篇 |
2017年 | 668篇 |
2016年 | 589篇 |
2015年 | 830篇 |
2014年 | 1011篇 |
2013年 | 1287篇 |
2012年 | 1346篇 |
2011年 | 1496篇 |
2010年 | 1295篇 |
2009年 | 1203篇 |
2008年 | 1265篇 |
2007年 | 1120篇 |
2006年 | 1276篇 |
2005年 | 1209篇 |
2004年 | 770篇 |
2003年 | 730篇 |
2002年 | 722篇 |
2001年 | 628篇 |
2000年 | 599篇 |
1999年 | 741篇 |
1998年 | 557篇 |
1997年 | 526篇 |
1996年 | 431篇 |
1995年 | 352篇 |
1994年 | 314篇 |
1993年 | 206篇 |
1992年 | 189篇 |
1991年 | 136篇 |
1990年 | 114篇 |
1989年 | 91篇 |
1988年 | 76篇 |
1987年 | 37篇 |
1986年 | 27篇 |
1985年 | 23篇 |
1984年 | 16篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
991.
空预器作为我国大型火力发电厂重要组成部分,其高效、稳定的运行对于火电机组而言具有十分重大的意义.当前,我国大部分火电机组均存在空预器堵塞现象,严重影响到锅炉安全、经济运行,为此,本文基于宝庆发电公司660MW机组三分仓容克氏空预器吹灰改造展开研究,对变工况下空预器吹灰改造前后差压变化做出对比分析,以及对定工况下空预器烟... 相似文献
992.
993.
采用ZSM-5和超稳Y(USY)分子筛催化剂,利用两段法固定床研究废旧轮胎的催化热解.通过对轮胎的催化热解后的轻质油品(<160 ℃)分析,发现热解后油品中单环芳香烃含量增加.如在热解温度500 ℃、催化温度400 ℃和催化剂与轮胎比例0.5的情况下,对没有催化剂以及含ZSM-5催化剂及USY催化剂的轮胎热解,得到的轻质馏分中苯的含量分别是0.15%、0.99%和1.89%,甲苯的含量分别是3.04%、5.68%和17.70%.这对从废旧轮胎热解油中提取化学化工物质的工艺研究有着重要的指导意义. 相似文献
994.
995.
996.
电离辐射诱导在金属硫蛋白在小鼠免疫器官中的表达 总被引:1,自引:0,他引:1
观察了电离辐射对金属硫蛋白(MT)在免疫器官中表达的影响。采用放射性^109Cd血红蛋白亲和分析法检测组织中MT含量。观察0.5、2、4、6GyX射线全身照射后16h,及4Gy全身照射后0.5、2、4、8、16、24、48、72h,昆明小鼠胸腺及脾脏中MT含量的变化。结果发现,在0.5~6Gy剂量范围内胸腺中MT含量剂量依赖性增高,其中4Gy和6Gy组有统计学意义(p〈0.05)。4GyX射线照射后8~48h胸腺中MT含量显著增高(p〈0.05~p〈0.001)。然而,量效及时研究均未见脾脏中MT含量的变化。以上结果表明,X射线能诱导MT在免疫器官中表达,但表现出明显的组织特异性。 相似文献
997.
Heng Du You-Jin Yuan Zhong-Shan Li Zhi-Jun Wang Peng Jin Xiao-Ni Li Guo-Zhu Cai Wen-Wen Ge Guo-Feng Qu Yuan He Jia-Wen Xia Jian-Cheng Yang Xue-Jun Yin 《核技术(英文版)》2018,(3)
A 53.667 MHz CW(continuous-wave) heavy ion IH-DTL has been designed for the SSC-LINAC injector of HIRFL-CSR(Heavy Ions Research Facility at Lanzhou-Cooling Storage Ring). It accelerates ions with maximum mass-to-charge ratio of 7.0 from 143 to 295 ke V/u. Low-power RF measurement of the IH-DTL1 has been taken to investigate the RF performance and the quality of the electric field distribution on the beam axis.The measured Q_0 value and the shunt impedance are 10,400 and 198 MX/m, respectively. The electric field distributions on and around the beam axis were evaluated and compared with the design value. By a new approach,the dipole field component is also estimated. The beam dynamics simulation using measured field distribution was presented in this paper. Based on the dynamics analysis in both transverse and longitudinal phase space, the field distribution can meet the design requirement. Finally, the RF conditioning and very first beam commissioning on the IH-DTL1 were finished. The beam test results agree well with the simulation results; what's more, the property of the variable output beam energy about the separated functions DTL was verified. 相似文献
998.
Qing-Chao Li Bo Wang Yan-Hua Zeng Zhong-Hua Cai Jin Zhou 《International journal of molecular sciences》2022,23(7)
Marine biofouling is a worldwide problem in coastal areas and affects the maritime industry primarily by attachment of fouling organisms to solid immersed surfaces. Biofilm formation by microbes is the main cause of biofouling. Currently, application of antibacterial materials is an important strategy for preventing bacterial colonization and biofilm formation. A natural three-dimensional carbon skeleton material, TRP (treated rape pollen), attracted our attention owing to its visible-light-driven photocatalytic disinfection property. Based on this, we hypothesized that TRP, which is eco-friendly, would show antifouling performance and could be used for marine antifouling. We then assessed its physiochemical characteristics, oxidant potential, and antifouling ability. The results showed that TRP had excellent photosensitivity and oxidant ability, as well as strong anti-bacterial colonization capability under light-driven conditions. Confocal laser scanning microscopy showed that TRP could disperse pre-established biofilms on stainless steel surfaces in natural seawater. The biodiversity and taxonomic composition of biofilms were significantly altered by TRP (p < 0.05). Moreover, metagenomics analysis showed that functional classes involved in the antioxidant system, environmental stress, glucose–lipid metabolism, and membrane-associated functions were changed after TRP exposure. Co-occurrence model analysis further revealed that TRP markedly increased the complexity of the biofilm microbial network under light irradiation. Taken together, these results demonstrate that TRP with light irradiation can inhibit bacterial colonization and prevent initial biofilm formation. Thus, TRP is a potential nature-based green material for marine antifouling. 相似文献
999.
Fear memory helps animals and humans avoid harm from certain stimuli and coordinate adaptive behavior. However, excessive consolidation of fear memory, caused by the dysfunction of cellular mechanisms and neural circuits in the brain, is responsible for post-traumatic stress disorder and anxiety-related disorders. Dysregulation of specific brain regions and neural circuits, particularly the hippocampus, amygdala, and medial prefrontal cortex, have been demonstrated in patients with these disorders. These regions are involved in learning, memory, consolidation, and extinction. These are also the brain regions where new neurons are generated and are crucial for memory formation and integration. Therefore, these three brain regions and neural circuits have contributed greatly to studies on neural plasticity and structural remodeling in patients with psychiatric disorders. In this review, we provide an understanding of fear memory and its underlying cellular mechanisms and describe how neural circuits are involved in fear memory. Additionally, we discuss therapeutic interventions for these disorders based on their proneurogenic efficacy and the neural circuits involved in fear memory. 相似文献
1000.