全文获取类型
收费全文 | 1795篇 |
免费 | 47篇 |
国内免费 | 7篇 |
专业分类
化学 | 1428篇 |
晶体学 | 11篇 |
力学 | 18篇 |
数学 | 154篇 |
物理学 | 238篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 73篇 |
2021年 | 102篇 |
2020年 | 40篇 |
2019年 | 60篇 |
2018年 | 74篇 |
2017年 | 49篇 |
2016年 | 70篇 |
2015年 | 76篇 |
2014年 | 58篇 |
2013年 | 163篇 |
2012年 | 82篇 |
2011年 | 107篇 |
2010年 | 92篇 |
2009年 | 76篇 |
2008年 | 106篇 |
2007年 | 121篇 |
2006年 | 82篇 |
2005年 | 88篇 |
2004年 | 57篇 |
2003年 | 63篇 |
2002年 | 47篇 |
2001年 | 15篇 |
2000年 | 16篇 |
1999年 | 23篇 |
1998年 | 14篇 |
1997年 | 17篇 |
1996年 | 23篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 12篇 |
1991年 | 5篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
排序方式: 共有1849条查询结果,搜索用时 31 毫秒
131.
Vladimir I. Bregadze Andrey A. Semioshkin Julia N. Las'kova Maria Ya. Berzina Irina A. Lobanova Igor B. Sivaev Mikhail A. Grin Rustam A. Titeev Dmitry I. Brittal Olga V. Ulybina Anastasija V. Chestnova Anastasija A. Ignatova Alexey V. Feofanov Andrey F. Mironov 《应用有机金属化学》2009,23(9):370-374
Conjugates of chlorin e6 with closo‐dodecaborate and cobalt bis(dicarbollide) anions were synthesized for the first time in high yields using the advanced ‘click’ methodology. In vitro study on A549 human lung adenocarcinoma cells revealed that the synthesized boronated conjugates are able to penetrate and accumulate in cancer cells, but their intracellular concentration is not sufficient for effective photodynamic and boron neutron capture therapy of cancer. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
132.
133.
134.
George I. Anthoulis Evagelia Kontou Alexander Fainleib Irina Bei Yurii Gomza 《Journal of Polymer Science.Polymer Physics》2008,46(11):1036-1049
The advantages of cyanate esters (CEs) versus competitor systems such as epoxies and polyimides, as well as the great reinforcing potential of organoclays properly dispersed into a polymeric matrix, have been examined in a series of polycyanurate (PCN)/montmorillonite (MMT) nanocomposites prepared under appropriate polymerization conditions. The curing schedule applied resulted in gradual propagation of polymerization. Through this procedure, the intragallery curing rate becomes comparable to the extragallery one, allowing intercalation before gelation. Systems with clay loadings from 1 to 3% per weight were synthesized, and their morphology and mechanical properties were studied by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), wide angle X‐ray scattering (WAXS), dynamic mechanical analysis (DMA), and tensile tests. Microscopy investigations revealed better dispersion for the 3 wt % system compared to smaller concentrations, in which aggregation and, in some cases, agglomeration were the conspicuous features. Roughness and area analyses revealed more homogeneous dispersion for this nanocomposite. Topology and 3D‐phase images further suggested considerable reduction of the average particle diameters. WAXS analysis showed that the interlayer spacing of nanocomposites was increased compared to pristine MMT, indicating the formation of intercalated structures. On the other hand, tensile strength and elongation at break values displayed abrupt diminution with MMT addition, while Young's modulus exhibited a slight but systematic increment with MMT content. The decreasing glass transition tendency observed for small clay loadings was reversed in the case of 3 wt %, while secondary transitions were practically unaffected by the presence of MMT. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1036–1049, 2008 相似文献
135.
Lubov' V. Snegur Yury S. Nekrasov Nataliya S. Sergeeva Zhanna V. Zhilina Vera V Gumenyuk Zoya A. Starikova Alexander A. Simenel Nataliya B. Morozova Irina K. Sviridova Valery N. Babin 《应用有机金属化学》2008,22(2):139-147
The toxicity of ferrocenylethyl benzotriazole ( 1 ) and other ferrocene compounds including ferrocenylmethyl benzimidazoles ( 4,5,6,11 ), ferricenium salts ( 3,9,10 ) and ferrocenylmethyl adenine ( 7 ), was studied. All ferrocene complexes under investigation showed low or medium toxicities. On the basis of an earlier model of chemical carcinogenesis, the antitumor activity of ferrocenylalkyl azoles 1, 8 and ferricenium salts 9, 10 was studied in vivo in the so‐called sub‐capsular test on human tumors. This effectiveness was compared with that of cisplatin. A series of ferrocenylalkyl azoles were synthesized by interacting azoles either with α‐hydroxyalkyl ferrocenes FcC(OH)R1R2 in organic solvent in the presence of aqueous HBF4 in quantitative yields or with trimethyl(aminomethyl)ferrocene iodide in an aqueous‐basic medium in good yields. The X‐ray determinations of molecular and crystal structures of α‐(1‐benzotriazolyl)ethylferrocene ( 1 ) and α‐(1‐naphthatriazolyl)ethylferrocene ( 12 ) were performed. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
136.
137.
138.
Joseph P. Corrigan Irina S. Zemel Arthur E. Woodward 《Journal of Polymer Science.Polymer Physics》1989,27(5):1135-1147
Crystallization of trans-1,4-polyisoprene from the mixed solvent pair hexane/2-pentanone was carried out and the effects on the morphology of seeding and the solvent composition were studied. α-TPI lamellae obtained by crystallization from a single solvent, hexane, at 20°C and by mixed-solvent crystallization at 40°C were characterized by DSC, FTIR, and suspension epoxidation/C-13 NMR. Crystalline stem lengths of 14.5 and 18 and a fold length of 10 monomer units were found. Segmented block copolymers were prepared by reaction of TPI lamellae in acetone suspension with HCl at ?7°C. These products were dissolved in 2-pentanone and precipitated at 0°C. A lamellar morphology, the details of which depend on the TPI block length, was observed by SEM; both preparations showed sharp endotherms; and the FTIR was characteristic of a combination of amorphous TPI, amorphous hydrochlorinated TPI, and of either the β crystalline form or both the α and β forms for TPI depending on the sample. 相似文献
139.
Alexei V. Radchenko Sergei V. Kostjuk Irina V. Vasilenko François Ganachaud Fyodor N. Kaputsky Yohann Guillaneuf 《Journal of polymer science. Part A, Polymer chemistry》2008,46(20):6928-6939
A kinetic study of the living cationic polymerization of p‐methoxystyrene using 1‐(4‐methoxyphenyl)ethanol ( 1 )/B(C6F5)3 initiating system in a mixture of CH3CN with CH2Cl2 1:1 (v/v) at room temperature was carried out utilizing a wide variety of conditions. The polymerization proceeded in a living fashion even in the presence of a large amount of water ([H2O]/[B(C6F5)3] ratio up to 20) to afford polymers whose Mn increased in direct proportion to monomer conversion with fairly narrow MWDs (Mw/Mn ≤ 1.3). The investigation revealed that the rate of polymerization was first‐order in B(C6F5)3 concentration, while a negative order in H2O concentration close to ?2 was obtained. It was also found that the rate of polymerization decreased with lowering temperature, which could be attributed to a decreased concentration in free Lewis acid, the true coinitiator of polymerization. A mechanistic scheme to explain the kinetic behavior of living p‐methoxystyrene polymerization is proposed, which has been validated by PREDICI simulation on multiple‐data curves obtained by 1H NMR in situ polymerization experiment. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6928–6939, 2008 相似文献
140.
Artificial intelligence is one of the fastest-developing areas of science that covers a remarkably wide range of problems to be solved. It has found practical application in many areas of human activity, also in medicine. One of the directions of cooperation between computer science and medicine is to assist in diagnosing and proposing treatment methods with the use of IT tools. This study is the result of collaboration with the Children’s Memorial Health Institute in Warsaw, from where a database containing information about patients suffering from Bruton’s disease was made available. This is a rare disorder, difficult to detect in the first months of life. It is estimated that one in 70,000 to 90,000 children will develop Bruton’s disease. But even these few cases need detailed attention from doctors. Based on the data contained in the database, data mining was performed. During this process, knowledge was discovered that was presented in a way that is understandable to the user, in the form of decision trees. The best models obtained were used for the implementation of expert systems. Based on the data introduced by the user, the system conducts expertise and determines the severity of the course of the disease or the severity of the mutation. The CLIPS language was used for developing the expert system. Then, using this language, software was developed producing six expert systems. In the next step, experimental verification was performed, which confirmed the correctness of the developed systems. 相似文献