全文获取类型
收费全文 | 2363篇 |
免费 | 166篇 |
国内免费 | 378篇 |
专业分类
化学 | 1555篇 |
晶体学 | 36篇 |
力学 | 80篇 |
综合类 | 4篇 |
数学 | 581篇 |
物理学 | 651篇 |
出版年
2023年 | 52篇 |
2022年 | 40篇 |
2021年 | 34篇 |
2020年 | 69篇 |
2019年 | 39篇 |
2018年 | 18篇 |
2017年 | 27篇 |
2016年 | 36篇 |
2015年 | 78篇 |
2014年 | 95篇 |
2013年 | 122篇 |
2012年 | 115篇 |
2011年 | 108篇 |
2010年 | 138篇 |
2009年 | 117篇 |
2008年 | 131篇 |
2007年 | 172篇 |
2006年 | 202篇 |
2005年 | 127篇 |
2004年 | 97篇 |
2003年 | 142篇 |
2002年 | 139篇 |
2001年 | 109篇 |
2000年 | 96篇 |
1999年 | 105篇 |
1998年 | 57篇 |
1997年 | 46篇 |
1996年 | 33篇 |
1995年 | 49篇 |
1994年 | 32篇 |
1993年 | 56篇 |
1992年 | 35篇 |
1991年 | 34篇 |
1990年 | 31篇 |
1989年 | 24篇 |
1988年 | 21篇 |
1987年 | 15篇 |
1986年 | 19篇 |
1985年 | 23篇 |
1984年 | 13篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有2907条查询结果,搜索用时 0 毫秒
1.
Science China Chemistry - Human health is always under global spotlight, but now it suffers from severe environmental issue and various diseases. Developing highly selective and effective... 相似文献
2.
3.
Yong-Li Li Qiang Zhang Jian-Jun Wu Li-Jun Xue Li-Ming Chen Jun-Mian Tian Zhuo-Ni Xu Ying Chen Xian-Wen Yang Xiao-Jiang Hao Jie Li 《Tetrahedron letters》2019,60(10):751-753
From Abies nukiangensis, two novel 13,14-seco-abietane diterpenes, nukiangendines A (1) and B (2) were isolated. Their relative structures were determined by extensive NMR and HRMS spectroscopic analysis. The absolute configuration of 1 was established by ECD calculations. Compound 1 showed significant anti-hepatitis C virus (HCV) effects. 相似文献
4.
《Journal of voice》2022,36(6):879.e1-879.e4
5.
《Journal of Functional Analysis》2019,276(12):3832-3857
We give an estimate for sums appearing in the Nyman–Beurling criterion for the Riemann Hypothesis. These sums contain the Möbius function and are related to the imaginary part of the Estermann zeta function. The estimate is remarkably sharp in comparison to other sums containing the Möbius function. The bound is smaller than the trivial bound – essentially the number of terms – by a fixed power of that number. The exponent is made explicit. The methods intensively use tools from the theory of continued fractions and from the theory of Fourier series. 相似文献
6.
Dr. Li Xu Xiang Chen Jingheng Wu Jinquan Wang Prof. Liangnian Ji Prof. Dr. Hui Chao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(10):4008-4020
A series of dinuclear ruthenium(II) complexes were synthesised, and the complexes were determined to be new highly selective compounds for binding to telomeric G‐quadruplex DNA. The interactions of these complexes with telomeric G‐quadruplex DNA were studied by using circular dichroism (CD) spectroscopy, fluorescence resonance energy transfer (FRET) melting assays, isothermal titration calorimetry (ITC) and molecular modelling. The results showed that the complexes 1 , 2 and 4 induced and stabilised the formation of antiparallel G‐quadruplexes of telomeric DNA in the absence of salt or in the presence of 100 mM K+‐containing buffer. Furthermore, complexes 1 and 2 strongly bind to and effectively stabilise the telomeric G‐quadruplex structure and have significant selectivity for G‐quadruplex over duplex DNA. In comparison, complex 3 had a much lesser effect on the G‐quadruplex, suggesting that possession of a suitably sized plane for good π–π stacking with the G‐quadruplets is essential for the interaction of the dinuclear ruthenium(II) complexes with the G‐quadruplex. Moreover, telomerase inhibition by the four complexes and their cellular effects were studied, and complex 1 was determined to be the most promising inhibitor of both telomerase and HeLa cell proliferation. 相似文献
7.
Lirong Ma Xuanlin Yang Xiuzhong Yao Weiyu Weng 《Photochemistry and photobiology》2020,96(5):1088-1095
Hexyl aminolevulinate (HAL) is a lipophilic derivative of 5-aminolevulinic acid (5-ALA) and can induce more protoporphyrin IX (PpIX) formation and stronger fluorescence intensity (FI) than 5-ALA, which will greatly facilitate photodynamic diagnosis and therapy. The main drawback of HAL is its low solubility in neutral aqueous media. In this study, surfactants were used to increase HAL solubility in the cell culture medium and serum, followed by in vitro fluorescence formation measurement in human pancreatic cancer cells (SW1990) and in vivo fluorescence detection in tumor-bearing mice. The results showed that Tween 80 (TW80) and Kolliphor® HS 15 (HS15) increased the solubility of HAL in the selected media. Although TW80 and HS15 exhibited in vitro cytotoxicity at high concentrations (5 mg mL−1), they facilitated fluorescent signal formation at the early stage of cell incubation. When surfactants were used, the FI should be determined without the routine washing process because surfactant-containing culture medium caused the loss of synthesized PpIX during the washing process. When HAL dissolved in TW80 solution was injected intraperitoneally into pancreatic cancer-bearing mice at a dose of 50 mg kg−1, the tumors exhibited red fluorescence, which indicated that systemic administration of surfactant-solubilized HAL might be applicable for tumor fluorescence detection in vivo. 相似文献
8.
Dr. Xue Liu Dr. Yi Luo Wenting Mao Dr. Jingang Jiang Dr. Hao Xu Prof. Lu Han Prof. Junliang Sun Prof. Peng Wu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(3):1182-1186
A novel crystalline high-silica zeolite with 12×8-membered ring (R) channel system is prepared with the aid of the 3D electron diffraction (3D ED) technique. A crystal with the same topology as one of the predicted daughter structures of CIT-13 germanosilicate, named ECNU-23 (East China Normal University 23) was coincidentally detected by the 3D ED investigation during the structure characterization of the “pure” powder sample of existing one-dimension (1D) 10-R ECNU-21. By controlling the alkaline-assisted hydrolysis under moderate conditions, we purified the phase of ECNU-23 by selectively breaking and removing the chemically weak Ge(Si)-O-Ge and metastable Si-O-Si bonds. Its structure was determined based on the 3D ED data, and confirmed by high-resolution TEM images and powder X-ray diffraction (PXRD) data. The aluminosilicate Al-ECNU-23 shows unique catalytic properties in the isomerization/ disproportionation of m-xylene as solid-acid catalyst. 相似文献
9.
10.
BackgroundIt is estimated that there are 338,000 new renal-cell carcinoma releases every year in the world. Renal cell carcinoma (RCC) is a heterogeneous tumor, of which more than 70% is clear cell renal cell carcinoma (ccRCC). It is estimated that about 30% of new renal-cell carcinoma patients have metastases at the time of diagnosis. However, the pathogenesis of renal clear cell carcinoma has not been elucidated. Therefore, it is necessary to further study the pathogenesis of ccRCC.MethodsTwo expression profiling datasets (GSE68417, GSE71963) were downloaded from the GEO database. Differentially expressed genes (DEGs) between ccRCC and normal tissue samples were identified by GEO2R. Functional enrichment analysis was made by the DAVID tool. Protein-protein interaction (PPI) network was constructed. The hub genes were excavated. The clustering analysis of expression level of hub genes was performed by UCSC (University of California Santa Cruz) Xena database. The hub gene on overall survival rate (OS) in patients with ccRCC was performed by Kaplan-Meier Plotter. Finally, we used the ccRCC renal tissue samples to verify the hub genes.Results1182 common DEGs between the two datasets were identified. The results of GO and KEGG analysis revealed that variations in were predominantly enriched in intracellular signaling cascade, oxidation reduction, intrinsic to membrane, integral to membrane, nucleoside binding, purine nucleoside binding, pathways in cancer, focal adhesion, cell adhesion molecules. 10 hub genes ITGAX, CD86, LY86, TLR2, TYROBP, FCGR2A, FCGR2B, PTPRC, ITGB2, ITGAM were identified. FCGR2B and TYROBP were negatively correlated with the overall survival rate in patients with ccRCC (P < 0.05). RT-qPCR analysis showed that the relative expression levels of CD86, FCGR2A, FCGR2B, TYROBP, LY86, and TLR2 were significantly higher in ccRCC samples, compared with the adjacent renal tissue groups.ConclusionsIn summary, bioinformatics technology could be a useful tool to predict the progression of ccRCC. In addition, there are DEGs between ccRCC tumor tissue and normal renal tissue, and these DEGs might be considered as biomarkers for ccRCC. 相似文献