全文获取类型
收费全文 | 2940篇 |
免费 | 213篇 |
国内免费 | 164篇 |
专业分类
化学 | 1440篇 |
晶体学 | 27篇 |
力学 | 104篇 |
综合类 | 5篇 |
数学 | 236篇 |
物理学 | 950篇 |
无线电 | 555篇 |
出版年
2023年 | 51篇 |
2022年 | 67篇 |
2021年 | 67篇 |
2020年 | 79篇 |
2019年 | 78篇 |
2018年 | 65篇 |
2017年 | 98篇 |
2016年 | 104篇 |
2015年 | 86篇 |
2014年 | 113篇 |
2013年 | 212篇 |
2012年 | 203篇 |
2011年 | 182篇 |
2010年 | 127篇 |
2009年 | 120篇 |
2008年 | 155篇 |
2007年 | 136篇 |
2006年 | 136篇 |
2005年 | 105篇 |
2004年 | 90篇 |
2003年 | 71篇 |
2002年 | 72篇 |
2001年 | 50篇 |
2000年 | 59篇 |
1999年 | 58篇 |
1998年 | 50篇 |
1997年 | 44篇 |
1996年 | 40篇 |
1995年 | 33篇 |
1994年 | 34篇 |
1993年 | 45篇 |
1992年 | 47篇 |
1991年 | 41篇 |
1990年 | 31篇 |
1989年 | 31篇 |
1988年 | 23篇 |
1987年 | 22篇 |
1986年 | 20篇 |
1985年 | 21篇 |
1984年 | 23篇 |
1983年 | 16篇 |
1982年 | 18篇 |
1981年 | 16篇 |
1980年 | 18篇 |
1979年 | 16篇 |
1978年 | 24篇 |
1976年 | 18篇 |
1975年 | 15篇 |
1974年 | 15篇 |
1973年 | 12篇 |
排序方式: 共有3317条查询结果,搜索用时 0 毫秒
81.
Huihuan Wu Sha Tu Zewei Zhuo Rui Jiang Ruijie Zeng Qi Yang Qizhou Lian Weihong Sha Hao Chen 《Molecules (Basel, Switzerland)》2023,28(1)
Ulcerative colitis is a chronic inflammatory bowel disorder that is hard to cure once diagnosed. Bisdemethoxycurcumin has shown positive effects on inflammatory diseases. However, the underlying bioactive interaction between bisdemethoxycurcumin and ulcerative colitis is unclear. The objective of this study was to determine the core target and potential mechanism of action of bisdemethoxycurcumin as a therapy for ulcerative colitis. The public databases were used to identify potential targets for bisdemethoxycurcumin and ulcerative colitis. To investigate the potential mechanisms, the protein-protein interaction network, gene ontology analysis, and Kyoto encyclopedia of genes and genomes analysis have been carried out. Subsequently, experimental verification was conducted to confirm the findings. A total of 132 intersecting genes of bisdemethoxycurcumin, as well as ulcerative coli-tis-related targets, were obtained. SRC, EGFR, AKT1, and PIK3R1 were the targets of highest potential, and the PI3K/Akt and MAPK pathways may be essential for the treatment of ulcerative colitis by bisdemethoxycurcumin. Molecular docking demonstrated that bisdemethoxycurcumin combined well with SRC, EGFR, PIK3R1, and AKT1. Moreover, the in vitro experiments suggested that bisdemethoxycurcumin might reduce LPS-induced pro-inflammatory cytokines levels in RAW264.7 cells by suppressing PI3K/Akt and MAPK pathways. Our study provided a comprehensive overview of the potential targets and molecular mechanism of bisdemethoxycurcumin against ulcerative colitis. Furthermore, it also provided a theoretical basis for the clinical treatment of ulcerative colitis, as well as compelling evidence for further study on the mechanism of bisdemethoxycurcumin in the treatment of ulcerative colitis. 相似文献
82.
83.
利用高折射率的金属超材料作为移相器,设计了一种紧凑型高功率微波TEM-TE11模式转换器。通过研究同轴扇形金属栅格超材料的传输特性,得到高折射率的全金属超材料。采用CST Microwave Studio 软件对金属超材料TEM-TE11模式转换器进行了数值模拟,结果显示:该转换器在1.56 GHz附近转换效率大于96%,相对带宽约4%,功率容量不低于2 GW,系统纵向长度仅0.42个波长。将所设计的模式转换器结合L波段磁绝缘线振荡器开展了一体化设计,在器件输出口得到了TE11模高功率微波输出。 相似文献
84.
85.
86.
层层自组装制备基于多壁碳纳米管的胆碱生物传感器 总被引:2,自引:2,他引:0
以经混酸处理的多壁碳纳米管(MWCNTs)修饰铂(Pt)电极,在此基础上固定(PAA/PVS)3复合膜,采用层层自组装技术将高分子聚电解质PDDA与胆碱氧化酶交替组装在已修饰的电极上,构建了电流型胆碱生物传感器。实验结果表明,MWCNTs的引入使电极对H2O2的催化电流明显增大,制成的酶电极可以有效控制酶量的使用,酶膜组装层数为8时最优,对胆碱的线性响应范围为5×10-7~1×10-4mol/L;灵敏度为12.53μA/mmol;响应时间为7.60s;检出限为2×10-7mol/L(S/N=3)。传感器的抗干扰能力强,稳定性好,30d时的响应电流值仍保持最初的89.5%。3次平行实验的RSD为3.64%。 相似文献
87.
Wen-Jie Shi Dan Liu Xin Li Dr. Sha Bai Prof. Yao-Yu Wang Prof. Dr. Ying-Feng Han 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(29):7853-7861
The incorporation of functional groups into the cavity of discrete supramolecular coordination cages (SCCs) will bring unique functions and applications. Here, three dicarboxylate ligands (H2 L1 Cl, H2 L2 Cl and H2 L3 Cl) containing N-heterocyclic carbene (NHC) precursors as linkers were introduced to construct SCCs by combining with two C3-symmertic (CpZr)3(μ3-O)(μ2-OH)3 clusters as three-connect vertices, resulted in a series of rugby-like V2E3 (V=vertex, E=edge) type homoleptic cages ( SCC-1 , SCC-2 and SCC-3 ). However, V4E6-type tetrahedral cages ( SCC-4 and SCC-5 ), incorporating six Au-NHC moieties, were obtained when the corresponding NHC-gold(I) functionalized ligands (H2 L1 Au, H2 L2 Au) were applied. For the first time, we present a trackable CpZr-involved cage to cage conversion to generate a heteroleptic V2E3 cage ( SCC-6 ) from two homoleptic cages ( SCC-2 and SCC-5 ) with different geometries of V2E3 and V4E6. The heteroleptic assembly SCC-6 can also be formed upon a subcomponent displacement strategy. The structural transformation and reassembly processes were detected and monitored by 1H NMR spectroscopy and electrospray-ionization mass spectrometry. The formation of heteroleptic assembly was further supported by single crystal X-ray diffraction analysis. Moreover, homoleptic cage SCC-2 possesses a trigonal bipyramidal cationic cavity allowing the encapsulation of a series of sulfonate anionic guests. 相似文献
88.
89.
90.
Nanostructures of β and γ-Ga2O3 were prepared by the solution combustion route using urea as fuel. The synthesized nano photocatalysts were characterized by use of XRD, FT-IR, BET, TEM, TGA–DTA, DRS, and Raman spectroscopy. XRD and TEM investigations confirmed the nanostructures; particle size was in the range 3–5 nm for γ-Ga2O3 and 40–50 nm for β-Ga2O3. The specific surface area of γ-Ga2O3 was 91 m2 g?1 and that of β-Ga2O3 was 24.3 m2 g?1. The polymorphs of gallium oxide were used as photocatalysts for decomposition of 1,000 mg/l 1,4-dioxane. More than 90 % of the 1,4-dioxane could be degraded in less than 180 min by use of 10 mg/l photocatalyst + 0.5 ml H2O2. The efficiency of photocatalytic degradation of 1,4-dioxane by the synthesized photocatalysts was compared with that of P-25 TiO2 and followed the order γ-Ga2O3 ≥ β-Ga2O3 > P-25 TiO2. The degradation was found to follow pseudo first-order kinetics. 相似文献