全文获取类型
收费全文 | 142786篇 |
免费 | 12265篇 |
国内免费 | 6217篇 |
专业分类
电工技术 | 8696篇 |
技术理论 | 8篇 |
综合类 | 9451篇 |
化学工业 | 24412篇 |
金属工艺 | 7790篇 |
机械仪表 | 9010篇 |
建筑科学 | 11560篇 |
矿业工程 | 4239篇 |
能源动力 | 4220篇 |
轻工业 | 9896篇 |
水利工程 | 2606篇 |
石油天然气 | 8797篇 |
武器工业 | 1071篇 |
无线电 | 15883篇 |
一般工业技术 | 16812篇 |
冶金工业 | 6546篇 |
原子能技术 | 1585篇 |
自动化技术 | 18686篇 |
出版年
2024年 | 543篇 |
2023年 | 2323篇 |
2022年 | 4046篇 |
2021年 | 5837篇 |
2020年 | 4415篇 |
2019年 | 3703篇 |
2018年 | 4057篇 |
2017年 | 4664篇 |
2016年 | 3987篇 |
2015年 | 5644篇 |
2014年 | 7037篇 |
2013年 | 8398篇 |
2012年 | 9174篇 |
2011年 | 9989篇 |
2010年 | 8692篇 |
2009年 | 8306篇 |
2008年 | 8107篇 |
2007年 | 7605篇 |
2006年 | 7826篇 |
2005年 | 6830篇 |
2004年 | 4635篇 |
2003年 | 4012篇 |
2002年 | 3765篇 |
2001年 | 3404篇 |
2000年 | 3541篇 |
1999年 | 3689篇 |
1998年 | 3089篇 |
1997年 | 2653篇 |
1996年 | 2414篇 |
1995年 | 2084篇 |
1994年 | 1696篇 |
1993年 | 1201篇 |
1992年 | 985篇 |
1991年 | 740篇 |
1990年 | 548篇 |
1989年 | 459篇 |
1988年 | 385篇 |
1987年 | 256篇 |
1986年 | 160篇 |
1985年 | 93篇 |
1984年 | 63篇 |
1983年 | 43篇 |
1982年 | 66篇 |
1981年 | 43篇 |
1980年 | 35篇 |
1979年 | 12篇 |
1978年 | 3篇 |
1965年 | 3篇 |
1959年 | 6篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
61.
62.
三元复合驱油体系中驱油剂的协同效应,会使油水间的界面张力大幅度下降,原油采收率大幅度提高;但三元复合驱油体系的色谱分离现象也会破坏其协同效应和完整性,揭示色谱分离现象及其影响因素对于改善三元复合驱油效果具有十分重要意义。以油藏工程和分析化学理论为指导,以化学分析和物理模拟为技术途径,并以大庆喇嘛甸油田典型区块地质特征和流体性质为研究对象,开展强碱三元复合驱色谱分离现象及其影响因素研究。结果表明,采用前置高浓度聚合物段塞后,可以有效扩大波及体积,但表面活性剂与碱和聚合物之间无因次等浓距增加,色谱分离现象加剧。大庆油区喇嘛甸油田不同区块油水性质差异对色谱分离现象存在影响,原因在于部分重烷基苯石油磺酸进入油相,影响水相中浓度检测值。强碱三元复合驱油体系中表面活性剂与碱和聚合物之间色谱分离程度比较严重,碱与聚合物之间较弱。 相似文献
63.
64.
65.
Strength of Materials - A metallographic method, dilatometry, and X-ray diffraction were applied to investigate the effects of undercooling and holding time on bainitic transformation,... 相似文献
67.
Yuhuan Sun Hongshuang Qin Zhengqing Yan Chuanqi Zhao Jinsong Ren Xiaogang Qu 《Advanced functional materials》2019,29(14)
Recently, quorum sensing (QS) inhibitors (QSIs) have been combined with antibiotics to enhance antibiofilm efficacy in vitro and in vivo. However, targeting QS signals alone is not enough to prevent bacterial infections. Drug resistance and recurrence of biofilms makes it difficult to eradicate. Herein, photodynamic therapy (PDT) is selected to unite QSIs and antibiotics. A synergistically antibiofilm system, which combines QSIs, antibiotics, and PDT based on hollow carbon nitride spheres (HCNSs) is envisaged. First, HCNS provides the multidrug delivering ability, enabling QSIs and antibiotics to be released in sequence. Subsequently, multistage releases sensitize bacteria effectively, potentiating the chemotherapeutic effects of the antibiotics. Finally, the integration of QSIs and PDT not only minimizes the possibility of drug resistance, but also overcomes the problem of limited mass and extension of PDT. Even after 48 h of incubation, the bacterial biofilm is obviously inhibited. And its biofilm disperse efficiency exceeds 48% (compared with QSI‐potentiated chemotherapy group) and 40% (compared with PDT group). Besides, the inhibition of the QS system influences phenotypes related to virulence factor production and surface hydrophobicity, which weaken biofilm invasion and formation. Eventually, this system is applied to disperse bacterial biofilm in vivo. Overall, PDT and QS modulation are devoted to eradicate drug resistance and recurrence of the biofilm. 相似文献
68.
69.
Xianjin Li Tianyu Li Pengcheng Xu Congxin Xie Yunhe Zhang Xianfeng Li 《Advanced functional materials》2021,31(22):2100133
Bromine-based flow batteries (Br-FBs) are considered one of the most promising energy storage systems due to their features of high energy density and low cost. However, they generally suffer from uncontrolled diffusion of corrosive bromine particularly at high temperatures. That is because the interaction between polybromide anions and the commonly used complexing agent (N–methyl–N–ethyl–pyrrolidinium bromide [MEP]) decreases with increasing temperatures, which causes serious self-discharge and capacity fade. Herein, a novel bromine complexing agent, 1–ethyl–2–methyl–pyridinium bromide (BCA), is introduced in Br-FBs to solve the above problems. It is proven that BCA can combine with polybromide anions very well even at a high temperature of 60 °C. Moreover, the BCA contributes to decreasing the electrochemical polarization of Br−/Br2 couple, which in turn improves their power density. As a result, a zinc–bromine flow battery with BCA as the complexing agent can achieve a high energy efficiency of 84% at 40 mA cm−2, even at high temperature of 60 °C and it can stably run for more than 400 cycles without obvious performance decay. This paper provides an effective complexing agent to enable a wide temperature range Br-FB. 相似文献
70.
Donghai Xu Peng Feng Yang Wang Wanpeng Yang Yu Wang Shaoyan Sun 《American Institute of Chemical Engineers》2022,68(2):e17472
Corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems by a protective water film. In this work, methanol was selected as organic matter, and the influences of vital structural parameters on water film properties and organic matter removal were studied via numerical simulation. The results indicate that higher than 99% of methanol conversion could be obtained and hardly affected by transpiration water layer, transpiring wall porosity and inner diameter. Increasing layer and porosity reduced reactor center temperature, but inner diameter's influence was lower relatively. Water film temperature reduced but coverage rate raised as layer, porosity, and inner diameter increased. Notably, the whole reactor was in supercritical state and coverage rate was only approximately 85% in the case of one layer. Increasing reactor length affected slightly the volume of the upper supercritical zone but enlarged the subcritical zone. 相似文献