全文获取类型
收费全文 | 126395篇 |
免费 | 25816篇 |
国内免费 | 11761篇 |
专业分类
化学 | 102446篇 |
晶体学 | 1307篇 |
力学 | 6550篇 |
综合类 | 659篇 |
数学 | 12922篇 |
物理学 | 40088篇 |
出版年
2024年 | 238篇 |
2023年 | 2091篇 |
2022年 | 2916篇 |
2021年 | 3485篇 |
2020年 | 5051篇 |
2019年 | 5818篇 |
2018年 | 4184篇 |
2017年 | 3556篇 |
2016年 | 7681篇 |
2015年 | 7549篇 |
2014年 | 8554篇 |
2013年 | 10646篇 |
2012年 | 11244篇 |
2011年 | 10912篇 |
2010年 | 8619篇 |
2009年 | 8393篇 |
2008年 | 8365篇 |
2007年 | 7086篇 |
2006年 | 6476篇 |
2005年 | 5605篇 |
2004年 | 4563篇 |
2003年 | 3796篇 |
2002年 | 4399篇 |
2001年 | 3408篇 |
2000年 | 3094篇 |
1999年 | 2435篇 |
1998年 | 1789篇 |
1997年 | 1708篇 |
1996年 | 1710篇 |
1995年 | 1448篇 |
1994年 | 1218篇 |
1993年 | 1066篇 |
1992年 | 911篇 |
1991年 | 837篇 |
1990年 | 693篇 |
1989年 | 532篇 |
1988年 | 400篇 |
1987年 | 337篇 |
1986年 | 343篇 |
1985年 | 275篇 |
1984年 | 157篇 |
1983年 | 123篇 |
1982年 | 103篇 |
1981年 | 60篇 |
1980年 | 45篇 |
1979年 | 11篇 |
1957年 | 32篇 |
1936年 | 2篇 |
1922年 | 1篇 |
1916年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
991.
Tumor cells transduced with herpes simplex virus thymidine kinase gene have been intensively applied to the field of positron emission tomography via imaging of its substrate. As a pilot synthesis approach, a facile preparation of 5‐[125I] iodoarabinosyl uridine starting from commercially available uridine is reported herein. 相似文献
992.
Ivica ?ilovi Dubravka Matkovi‐alogovi Ivan Kos Mladen Biru Milena Jadrijevi‐Mladar Taka
《Acta Crystallographica. Section C, Structural Chemistry》2007,63(1):o45-o47
In the crystal structures of two cyclic trihydroxamic acid derivatives containing the same substructure unit, viz. 1,3,5‐trihydroxy‐1,3,5‐triazinane‐2,4,6‐trione dihydrate, C3H3N3O6·2H2O, (I), and 1,3,5‐benzyloxy‐1,3,5‐triazinane‐2,4,6‐trione, C24H21N3O6, (II), there is no significant difference in the geometric parameters. In (I), there are 11 hydrogen bonds of the O—H⋯O type interconnecting the molecules in a three‐dimensional network, while in (II) there are only two weak C—H⋯O hydrogen bonds. The results of IR spectroscopic analysis are in good agreement with the crystallographic study. 相似文献
993.
A room temperature method for the encapsulation of pyrene in SiO2 nanoparticles is described. The relation between alkoxysilane surfactant chain length, reactant molar ratios and the uptake of dye, sample morphology, photophysical properties, and the ability of the silicate matrix to protect the encapsulated dye was examined. The synthesis can easily be adapted for the encapsulation of other hydrophobic and thermolabile substances, and used in the development of nanostructured optically active coatings, films and monoliths. 相似文献
994.
995.
Linda Kaufmann Hans‐Wolfram Lerner Michael Bolte 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(10):o588-o590
A new polymorph of tetraphenyldiboroxane [or oxybis(diphenylborane)], C24H20B2O, (Ia), has been found. It is monoclinic, like the already known form, (Ib), and can be refined in the same space group, namely P21/c, or in the equivalent setting P21/n. The molecular conformations of the two polymorphs differ in the rotations of two of the phenyl rings about the B—C bonds, leading to markedly different packing patterns and cell dimensions. 相似文献
996.
997.
Boris‐Marko Kukovec Zora Popovi Gordana Pavlovi 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(9):m389-m391
In the title compound, [Cd(C7H6NO2)2]n, the CdII ion has a distorted octahedral geometry. The 6‐methylpyridine‐2‐carboxylate anions are perpendicular to one another and act as bidentate and bridging ligands. Two carboxylate O atoms bridge the CdII ions, forming centrosymmetric dinuclear units. These units are further connected via carboxylate O atoms into a one‐dimensional polymeric chain which extends in the [100] direction. 相似文献
998.
999.
1000.
Yanlin Huang Kiwan Jang Wanxue Zhao Eunjin Cho Ho Sueb Lee Xigang Wang Dake Qin Ying Zhang Chanfang Jiang Hyo Jin Seo 《Journal of solid state chemistry》2007,180(12):3325-3332
Usually, Sm2+ ions could be reduced by heating the materials in reducing atmospheres. Exposure to ionizing radiations is also known to cause Sm3+→Sm2+ conversion. In this work, BaBPO5 doped with the samarium ion was prepared by high temperature solid-state reaction. Sm2+ ions were obtained by two different reduction methods, i.e., heating in H2 reduced atmosphere and X-ray irradiation. The measurements of X-ray diffraction (XRD), and scanning electron microscope (SEM) were investigated. It is found that the conversion of Sm3+→Sm2+ is very efficient in BaBPO5 hosts after X-ray irradiation. Sm2+ ions under these two reduction methods exhibit different characteristics that were studied by measurements of luminescence and decay. The results showed that the luminescence properties of Sm2+ ions in BaBPO5 were highly dependent on the sample preparation conditions. 相似文献