全文获取类型
收费全文 | 80254篇 |
免费 | 8434篇 |
国内免费 | 4447篇 |
学科分类
工业技术 | 93135篇 |
出版年
2024年 | 329篇 |
2023年 | 1640篇 |
2022年 | 2789篇 |
2021年 | 4043篇 |
2020年 | 2952篇 |
2019年 | 2487篇 |
2018年 | 2751篇 |
2017年 | 2916篇 |
2016年 | 2628篇 |
2015年 | 3554篇 |
2014年 | 4470篇 |
2013年 | 5154篇 |
2012年 | 5791篇 |
2011年 | 5986篇 |
2010年 | 5149篇 |
2009年 | 4965篇 |
2008年 | 4737篇 |
2007年 | 4449篇 |
2006年 | 4169篇 |
2005年 | 3491篇 |
2004年 | 2610篇 |
2003年 | 2431篇 |
2002年 | 2552篇 |
2001年 | 2249篇 |
2000年 | 1700篇 |
1999年 | 1583篇 |
1998年 | 1093篇 |
1997年 | 839篇 |
1996年 | 777篇 |
1995年 | 655篇 |
1994年 | 501篇 |
1993年 | 392篇 |
1992年 | 311篇 |
1991年 | 233篇 |
1990年 | 175篇 |
1989年 | 123篇 |
1988年 | 121篇 |
1987年 | 60篇 |
1986年 | 77篇 |
1985年 | 34篇 |
1984年 | 28篇 |
1983年 | 19篇 |
1982年 | 21篇 |
1981年 | 13篇 |
1980年 | 16篇 |
1979年 | 16篇 |
1977年 | 7篇 |
1975年 | 8篇 |
1970年 | 10篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 409 毫秒
91.
Yuanfang Tao Xin Ji Dr. Jian Zhang Yue Jin Nannan Wang Prof. Yubing Si Prof. Weili Zhao 《Chembiochem : a European journal of chemical biology》2020,21(21):3131-3136
Near-infrared (NIR) fluorescent probes are very significant for detecting cysteine in biological systems. Herein, we report a highly selective and sensitive NIR turn-on fluorescent probe (BDP-NIR) based on BODIPY with large Stokes shift (105 nm) for detecting Cys. We clarified the sensing mechanism based on the different thiol-induced SNAr substitution/rearrangement reaction of the probe with cysteine and homocysteine/glutathione, which leads to the corresponding amino- and thiol-BODIPY dyes with distinct photophysical properties. Moreover, a novel mechanism of fluorescence quenching was demonstrated by density functional theory calculation. The reason for the fluorescence quenching of the probe might be intersystem crossing (from singlet to triplet excited state). Moreover, BDP-NIR had a high linear dynamic range of 0–500 μM, which was promising for detecting cysteine quantificationally. Significantly, BDP-NIR was capable of sensing endogenous cysteine in living cells and in vivo. 相似文献
92.
Chun Dong Hyun Rhim Geun Bae Youn Min Hye Deviana Deviana Lee Ji Eun Park Ji Chan Jeong Heondo 《Topics in Catalysis》2020,63(9-10):793-809
Topics in Catalysis - Fischer–Tropsch synthesis (FTS) is a promising way to produce clean liquid fuels and high value-added chemicals from low-value carbon-containing resources such as coal,... 相似文献
93.
Xiaopeng Yue Yongjian Xu Nina Gou Hongkui Li 《Polymer-Plastics Technology and Engineering》2015,54(6):639-646
A long fatty side chain was introduced into the macromolecule of hydroxyethyl cellulose (HEC) via esterification reaction. The hydrophobicity of hydroxyethyl cellulose lauric acid ester (HECLAE) was enhanced in comparison with HEC. The obtained HECLAE was used as macromolecular coupling agent in poly (butylene succinate)/wood flour composites and exhibited a positive influence on improving the mechanical performance of composites. Besides, HECLAE plays a role as a hydrophobic agent in composites. A significant increase in storage modulus (E’) was observed upon the incorporation of treated wood flour. SEM images showed that the dispersion of treated wood flour in PBS matrix was improved. 相似文献
94.
95.
朱岳 《合成材料老化与应用》2020,49(1):36-39
以膨润土片层结构做模板,将银氨溶液与改性膨润土进行离子交换反应,通过光还原法制备得到了纳米银插层膨润土抗菌剂。通过高分辨透射电镜、能谱分析测试表征纳米银插层膨润土抗菌剂的结构与成分,并测试抗菌性能和白度变化。结果表明:纳米银插层膨润土抗菌剂的膨润土片层中夹插有球形纳米银,纳米银颗粒的主要粒径为2-8 nm,其中小部分粒径为8-17 nm,这种独特的模板结构确保纳米银抗菌剂结构稳定和性能稳定。纳米银插层膨润土抗菌剂中纳米银含银量为1.04wt%,有优异的抗菌性能,对金黄色葡萄球菌和大肠杆菌的最小抑菌浓度(MIC)分别为50μg/mL。纳米银插层膨润土抗菌剂具有颜色稳定性和持久抗菌性。 相似文献
96.
地应力是影响巷道稳定性的重要因素之一。文章结合王庄煤矿+540采区实际工程地质条件,基于矩形巷道应力现场测试数据,对矩形巷道周围的应力变化进行了分析。并基于FLAC 3D和DDA数值模拟软件,分析了矩形巷道尺寸对围岩应力的影响,以及三维地应力水平对矩形巷道的稳定性。结果表明,在一定范围内,地应力侧压比λ与巷道顶板位移成正比,而超出这一范围,顶板位移随着λ值的增大反而减少。 相似文献
98.
Wenjie Wu Yan Liu Dong Liu Wenxing Chen Zhaoyi Song Ximin Wang Yamin Zheng Ning Lu Chunxia Wang Junjie Mao Yadong Li 《Nano Research》2021,14(4):998-1003
The demand for high-performance non-precious-metal electrocatalysts to replace the noble metal-based catalysts for oxygen reduction reaction(ORR)is intensively increasing.Herein,single-atomic copper sites supported on N-doped three-dimensional hierarchically porous carbon catalyst(Cu1/NC)was prepared by coordination pyrolysis strategy.Remarkably,the Cu1/NC-900 catalyst not only exhibits excellent ORR performance with a half-wave potential of 0.894 V(vs.RHE)in alkaline media,outperforming those of commercial Pt/C(0.851 V)and Cu nanoparticles anchored on N-doped porous carbon(CuNPs/NC-900),but also demonstrates high stability and methanol tolerance.Moreover,the Cu1/NC-900 based Zn-air battery exhibits higher power density,rechargeability and cyclic stability than the one based on Pt/C.Both experimental and theoretical investigations demonstrated that the excellent performance of the as-obtained Cu1/NC-900 could be attributed to the synergistic effect between copper coordinated by three N atoms active sites and the neighbouring carbon defect,resulting in elevated Cu d-band centers of Cu atoms and facilitating intermediate desorption for ORR process.This study may lead towards the development of highly efficient non-noble metal catalysts for applications in electrochemical energy conversion. 相似文献
99.
100.