全文获取类型
收费全文 | 17742篇 |
免费 | 3056篇 |
国内免费 | 3255篇 |
专业分类
化学 | 14456篇 |
晶体学 | 382篇 |
力学 | 832篇 |
综合类 | 305篇 |
数学 | 1911篇 |
物理学 | 6167篇 |
出版年
2024年 | 35篇 |
2023年 | 274篇 |
2022年 | 429篇 |
2021年 | 565篇 |
2020年 | 704篇 |
2019年 | 738篇 |
2018年 | 625篇 |
2017年 | 658篇 |
2016年 | 854篇 |
2015年 | 980篇 |
2014年 | 1115篇 |
2013年 | 1485篇 |
2012年 | 1569篇 |
2011年 | 1641篇 |
2010年 | 1401篇 |
2009年 | 1252篇 |
2008年 | 1460篇 |
2007年 | 1312篇 |
2006年 | 1109篇 |
2005年 | 996篇 |
2004年 | 785篇 |
2003年 | 656篇 |
2002年 | 671篇 |
2001年 | 597篇 |
2000年 | 446篇 |
1999年 | 316篇 |
1998年 | 222篇 |
1997年 | 161篇 |
1996年 | 168篇 |
1995年 | 127篇 |
1994年 | 118篇 |
1993年 | 91篇 |
1992年 | 84篇 |
1991年 | 78篇 |
1990年 | 47篇 |
1989年 | 37篇 |
1988年 | 32篇 |
1987年 | 37篇 |
1986年 | 26篇 |
1985年 | 31篇 |
1984年 | 17篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
In this paper, we show that two Toeplitz operators Tf and Tg on the Hardy space of the polydisk can commute if and only if the Berezin transform of the commutator [Tf, Tg] is n-harmonic. 相似文献
962.
The synthesis of two hydrophobic cavitands bearing four (1) and eight (2) thymidine residues covalently linked with triazole moieties is reported. Spectral evidence indicates the adoption of a hydrogen-bonded T-quartet assembly by 1 in chloroform at low temperature and a π-stacked quadruplex by 2 in DMSO under ambient conditions. 相似文献
963.
The TbIII compound [Tb(tci)(H2O)]n · n(DMF) ( 1 ) [H3tci = tri(2‐carboxythyl)isocyanurate, DMF = N,N′‐dimethylformamide] was synthesized by the reaction of terbium oxide, H3tci, and two drops of concentrated nitric acid in the presence of DMF and H2O. Single crystal X‐ray analysis reveals that it features a three‐dimensional (3D) framework based on infinite –Tb–COO–Tb– chains. The tci ligand in 1 links six different TbIII ions with its two carboxylate groups in μ2‐κ1O;κ2O,O′ mode and the third in μ2‐κ1O;κ1O′ mode. Thermal analysis reveals that it remains high thermal stability until 390 °C. Luminescence investigation shows that it emits characteristic green light of TbIII ions. 相似文献
964.
Yan‐Xue Chen Kang‐Kang Tang Xin Wang Bing‐Yi Chen Guo‐Qiang Qin Jin‐Hui Yang 《无机化学与普通化学杂志》2014,640(11):2292-2295
The zinc(II) coordination polymer [Zn3(BPT)2(μ2‐H2O)2(H2O)2]n · n(DMA) ( 1 ) (H3BPT = biphenyl‐3,4′,5‐tricarboxylic acid, DMA = N,N′‐dimethylactamide) was obtained by the solvothermal reaction of H3BPT with Zn(NO3)2 in DMA/H2O mixed solvent. Single crystal X‐ray analysis reveals that compound 1 has a complicated 3D framework containing linear trinuclear [Zn3(COO)4(μ2‐H2O)2] clusters as building subunits, which can be simplified into a (3,6)‐connected rtl topological network with the Schläfli symbol {4.62}2{42.610.83}. The calculated results of total and partial density of states (DOS) indicate that the luminescence of 1 mainly originates from intraligand charge transfer. 相似文献
965.
966.
Qing‐Hui Guo Zhan‐Da Fu Liang Zhao Mei‐Xiang Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(49):13766-13770
O6‐Corona[3]arene[3]tetraazines, a new class of macrocyclic compounds, were synthesized efficiently in a one‐pot reaction from the nucleophilic aromatic substitution reaction between 1,4‐dihydroxybenzene derivatives and 3,6‐dichlorotetrazine in warm acetonitrile. In the crystalline structure, the resulting macrocycles adopt highly symmetric structures of a regular hexagonal cavity with all bridging oxygen atoms and tetrazine rings located on the same plane with phenylene units orthogonally orientated. The constitutional aromatic rings are able to rotate around the macrocyclic annulus, depending on the steric effect of the substituents and temperature, in solution. The electron‐deficient nature revealed by cyclic voltammetry, differential pulse voltammetry, and characteristic absorbances at a visible region show the O6‐corona[3]arene[3]tetrazines to be suitable macrocyclic receptors for electron‐rich guests. 相似文献
967.
968.
Genotyping of exons 1 to 20 in Duchenne muscular dystrophy by universal multiplex PCR and short‐end capillary electrophoresis 下载免费PDF全文
One rapid CE method was established to diagnose Duchenne muscular dystrophy (DMD). DMD is a severe recessive inherited disorder frequently caused by gene deletions. Among them, exons 1–20 account for nearly 30% of occurrences. In this study, the universal multiplex PCR was used to enhance the fluorescently labeling efficiency, which was performed only by one universal fluorescent primer. After PCR, a short‐end injection CE (short‐end CE) speeded up the genotyping of the DMD gene. This method involved no extra purification, and was completed within 9 min. The CE conditions contained a polymer solution of 1.5% hydroxylethylcellulose in 1× TBE buffer at 6 kV for separation. This method was applied to test six DMD patients and one healthy male person. The results showed good agreement with those of multiplex ligation‐dependent probe amplification. This method can be applied for clinical diagnosis of DMD disease. Accurate diagnosis of the DMD gene is the best way to prevent the disease. 相似文献
969.
Genetic profile characterization and population study of 21 autosomal STR in Chinese Kazak ethnic minority group 下载免费PDF全文
Xiao‐Ye Wang Chun‐Mei Shen Wen‐Juan Liu Jiang‐Wei Yan Hong‐Dan Wang Hong‐Wei Pu Yan‐Li Wang Guang Yang Yu‐Dang Zhang Hao‐Tian Meng Hang Jing Bo‐Feng Zhu 《Electrophoresis》2014,35(4):503-510
Short tandem repeat loci have been recognized as useful tools in the routine forensic application and in recent decades, more and more new short tandem repeat (STR) loci have been constantly discovered, studied, and applied in forensic caseworks. In this study, we investigated the genetic polymorphisms of 21 STR loci in the Kazak ethnic minority as well as the genetic relationships between the Kazak ethnic minority and other populations. Allelic frequencies of 21 STR loci were obtained from 114 unrelated healthy Kazak individuals in the Ili Kazak Autonomous Prefecture, Xinjiang Uigur Autonomous Region of China. We observed a total of 159 alleles in the group with the allelic diversity values ranging from 0.0044 to 0.5088. The highest polymorphism was found at D19S433 locus and the lowest was found at D1S1627. Statistical analysis of the generated data indicated no deviation from Hardy–Weinberg equilibriums at all 21 STR loci. In order to estimate the population differentiation, allelic frequencies of all STR loci of the Kazak were compared with those of other neighboring populations using analysis of molecular variance method. Statistically significant differences were found between the studied population and other populations at 2–7 STR loci. A neighbor‐joining tree was constructed based on allelic frequencies of the 21 STR loci and phylogenetic analysis indicates that the Kazak has a close genetic relationship with the Uigur ethnic group. The present results may provide useful information for forensic sciences and population genetics studies, and can also increase our understanding of the genetic background of this group. The present findings showed that all the 21 STR loci are highly genetically polymorphic in the Kazak group, which provided valuable population genetic data for the genetic information study, forensic human individual identification, and paternity tests. 相似文献
970.
Thirteen new glucosides (1–13) of magnolol and honokiol were obtained from specific O-glycosylation by two filamentous fungi, Cunninghamella echinulata AS 3.3400 and Rhizopus japonicus ZW-4. The glucosides' structures were determined on the basis of extensive spectroscopic (HRESIMS, 1D and 2D NMR, and CD) analyses and a chemical method. C. echinulata appeared to transfer a glucosyl moiety to 2-OH of magnolol and honokiol, whereas R. japonicus preferred to regio-specifically transfer a glucosyl moiety to 4′-OH when honokiol was as the substrate. In addition, hydroxylation by C. echinulata and specific 6″-O-acylation of the introduced glucosyl moiety by R. japonicus were observed as minor reactions. Bioassay results indicated that glucosides 1–12 together with magnolol and honokiol at 10 μM attenuated the glutamate-induced toxicity in SK-N-SH cells to levels comparable to the results for MK-801, a positive control. However, the water-solubility of major glucosylated products (1, 8, and 11) increased greatly. 相似文献