全文获取类型
收费全文 | 40632篇 |
免费 | 4302篇 |
国内免费 | 2256篇 |
专业分类
电工技术 | 1841篇 |
技术理论 | 1篇 |
综合类 | 3148篇 |
化学工业 | 12219篇 |
金属工艺 | 1766篇 |
机械仪表 | 2024篇 |
建筑科学 | 2833篇 |
矿业工程 | 1304篇 |
能源动力 | 829篇 |
轻工业 | 3441篇 |
水利工程 | 736篇 |
石油天然气 | 3489篇 |
武器工业 | 393篇 |
无线电 | 3153篇 |
一般工业技术 | 4260篇 |
冶金工业 | 1235篇 |
原子能技术 | 463篇 |
自动化技术 | 4055篇 |
出版年
2024年 | 206篇 |
2023年 | 737篇 |
2022年 | 1054篇 |
2021年 | 1359篇 |
2020年 | 1322篇 |
2019年 | 1084篇 |
2018年 | 1095篇 |
2017年 | 1328篇 |
2016年 | 1397篇 |
2015年 | 1513篇 |
2014年 | 2070篇 |
2013年 | 2326篇 |
2012年 | 2763篇 |
2011年 | 2868篇 |
2010年 | 2024篇 |
2009年 | 2167篇 |
2008年 | 1942篇 |
2007年 | 2628篇 |
2006年 | 2499篇 |
2005年 | 2344篇 |
2004年 | 2029篇 |
2003年 | 1770篇 |
2002年 | 1567篇 |
2001年 | 1368篇 |
2000年 | 1086篇 |
1999年 | 939篇 |
1998年 | 761篇 |
1997年 | 564篇 |
1996年 | 471篇 |
1995年 | 443篇 |
1994年 | 357篇 |
1993年 | 253篇 |
1992年 | 212篇 |
1991年 | 138篇 |
1990年 | 132篇 |
1989年 | 106篇 |
1988年 | 62篇 |
1987年 | 45篇 |
1986年 | 26篇 |
1985年 | 20篇 |
1984年 | 26篇 |
1983年 | 18篇 |
1982年 | 16篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1959年 | 5篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
《International Journal of Hydrogen Energy》2022,47(79):33765-33780
This work investigates selective Ni locations over Ni/CeZrOx–Al2O3 catalysts at different Ni loading contents and their influences on reaction pathways in ethanol steam reforming (ESR). Depending on the Ni loading contents, the added Ni selectively interacts with CeZrOx–Al2O3, resulting in the stepwise locations of Ni over CeZrOx–Al2O3. This behavior induces a remarkable difference in hydrogen production and coke formation in ESR. The selective interaction between Ni and CeZrOx for 10-wt.% Ni generates more oxygen vacancies in the CeZrOx lattice. The Ni sites near the oxygen vacancies enhance reforming via steam activation, resulting in the highest hydrogen production rate of 1863.0 μmol/gcat·min. In contrast, for 15 and 20-wt.% Ni, excessive Ni is additionally deposited on Al2O3 after the saturation of Ni–CeZrOx interactions. These Ni sites on Al2O3 accelerate coking from the ethylene produced on the acidic sites, resulting in a high coke amount of 19.1 mgc/gcat·h (20Ni/CZ-Al). 相似文献
3.
药物相互作用改变了剂量效应关系,可能会降低疗效或增加毒性,是临床应用中合并用药治疗时重要的考虑因素。预测具有临床意义的药物相互作用是药物研发过程中获益风险评估的重要环节。本文概述了药物研发过程中药物相互作用研究的目的和意义,体内和体外研究的主要内容;梳理分析了2020年国家药品监督管理局(National Medical Products Administration, NMPA)和美国食品药品监督管理局(Food and Drug Administration, FDA)批准上市的新药药物相互作用研究情况,旨在为我国药物研发过程中药物相互作用研究及其监管审评提供参考。 相似文献
4.
针对赤泥等固体废弃物对环境危害性大且利用率低等问题,以碱激发赤泥-矿渣基地聚物注浆材料为
研究对象,研究了不同掺量的聚羧酸(PA)减水剂、醛酮缩合物(AKC)减水剂和萘系(N)减水剂对材料凝结时间、流动
性及强度等的影响,并通过 XRD、傅里叶红外光谱及 SEM 等设备对减水剂的作用机理进行研究。 结果表明:减水剂增
强了材料的流动性但降低了材料的剪切应力;N 和 PA 减水剂能缩短材料的凝结时间,但 AKC 减水剂会延长材料的凝
结时间;N 和 AKC 减水剂能提高材料的强度,但 PA 减水剂会降低材料的强度;N 减水剂对材料的综合性能提升效果
更加明显,其最优掺量为 0. 7%;减水剂对赤泥-矿渣基地聚物性能提升的作用机理主要是促进地聚合物凝胶的形成。
研究成果为拓展赤泥在工程上的使用途径和效率提供了理论指导。 相似文献
5.
Dr. Qian Wang Xinli Fan Nannan Jing Han Zhao Dr. Lijia Yu Prof. Xinjing Tang 《Chembiochem : a European journal of chemical biology》2021,22(11):1901-1907
Small interfering RNA (siRNA) can effectively silence target genes through Argonate 2 (Ago2)-induced RNA interference (RNAi). It is very important to control siRNA activity in both spatial and temporal modes. Among different masking strategies, photocaging can be used to regulate gene expression through light irradiation with spatiotemporal and dose-dependent resolution. Many different caging strategies and caging groups have been reported for light-activated siRNA gene silencing. Herein, we describe a novel caging strategy that increases the blocking effect of RISC complex formation/process through host/guest (including ligand/receptor) interactions, thereby enhancing the inhibition of caged siRNA activity until light activation. This strategy can be used as a general approach to design caged siRNAs for the photomodulation of gene silencing of exogenous and endogenous genes. 相似文献
6.
Cuiping Yu Shuang Sun Sihui Li Huijia Yan Henan Zou 《International Journal of Food Science & Technology》2022,57(2):1173-1185
In this study, the effect of high-intensity ultrasound (HIUS) (200 and 400 W for 0, 5, 10 and 15 min respectively) on conformational changes, physicochemical, rheological and emulsifying properties of scallop (Patinopecten yessoensis) myofibrillar protein (SMP) was investigated. HIUS-treated SMP had lower α-helix content and higher β-sheet content compared with the native SMP. HIUS treatment induced the unfolding of SMP and increased the surface hydrophobicity. The particle size of SMP decreased and the absolute zeta-potential increased after ultrasonication, which in turn increased the solubility of SMP. The conformational changes and the improvement of physicochemical properties of SMP increased the ability for SMP to lower the interfacial tension at the oil–water interface and increased the percentage of adsorbed protein. As a result, the emulsifying properties, rheological properties of SMP and storage stability of emulsions were also improved. In conclusion, HIUS treatment has future potential for improving the emulsifying properties of SMP. 相似文献
7.
8.
Somnath Karmakar 《Polycyclic Aromatic Compounds》2019,39(2):159-171
Eigensolutions of {X( = C,B,N),Y( = C,B,N)}-cyclacene graphs with next nearest neighbor (nnn) interactions have been obtained in analytical forms by adapting n-fold rotational symmetry followed by two-fold rotational symmetry (or a plane of symmetry). Expressions of eigensolution indicate the subspectral relationship among such cyclacenes with an even number of hexagonal rings e.g., eigenvalues of {X,Y}-di-cyclacene are found in the eigenspectra of all such even cyclacenes. Total π-electron energies and highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO–LUMO) gaps are calculated using the analytical expressions obtained and are found to vary negligibly with the variation of nnn interactions in such cyclacenes. Total π-electron energy is found to increase due to increase in restriction intensity of nnn interactions, whereas the HOMO–LUMO gap of polyacenecs having the even number of hexagonal rings and with one electron at each site (atom) decreases with increase in the restriction intensity since such systems contain degenerate half-filled HOMO (bonding or nonbonding) that are much more vulnerable for perturbations imposed through nnn interactions. 相似文献
9.