全文获取类型
收费全文 | 26148篇 |
免费 | 4392篇 |
国内免费 | 3377篇 |
专业分类
化学 | 18995篇 |
晶体学 | 299篇 |
力学 | 1698篇 |
综合类 | 267篇 |
数学 | 2988篇 |
物理学 | 9670篇 |
出版年
2024年 | 12篇 |
2023年 | 511篇 |
2022年 | 556篇 |
2021年 | 807篇 |
2020年 | 1064篇 |
2019年 | 949篇 |
2018年 | 814篇 |
2017年 | 767篇 |
2016年 | 1226篇 |
2015年 | 1174篇 |
2014年 | 1505篇 |
2013年 | 1863篇 |
2012年 | 2406篇 |
2011年 | 2474篇 |
2010年 | 1675篇 |
2009年 | 1546篇 |
2008年 | 1760篇 |
2007年 | 1527篇 |
2006年 | 1486篇 |
2005年 | 1233篇 |
2004年 | 1036篇 |
2003年 | 879篇 |
2002年 | 901篇 |
2001年 | 735篇 |
2000年 | 554篇 |
1999年 | 658篇 |
1998年 | 448篇 |
1997年 | 391篇 |
1996年 | 451篇 |
1995年 | 380篇 |
1994年 | 365篇 |
1993年 | 284篇 |
1992年 | 259篇 |
1991年 | 230篇 |
1990年 | 179篇 |
1989年 | 163篇 |
1988年 | 137篇 |
1987年 | 97篇 |
1986年 | 91篇 |
1985年 | 74篇 |
1984年 | 41篇 |
1983年 | 31篇 |
1982年 | 21篇 |
1981年 | 26篇 |
1980年 | 14篇 |
1963年 | 7篇 |
1959年 | 12篇 |
1958年 | 11篇 |
1957年 | 20篇 |
1956年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 302 毫秒
961.
We study the generalized sine-Gordon hierarchy and its associated-dependent modified sine-Gordon hierarchy. Two Bäcklund transformations for these two families are constructed. One of them is a generalization of the Bäcklund transformations of Wadatiet al. and the other one is new. Gauge transformations of a relevant AKNS system are employed to reduce the integration of these equations via the Bäcklund transformations to quadratures. Three generations of explicit solutions of the sine-Gordon equation are presented. 相似文献
962.
963.
964.
稀土离子(Ⅲ)与牛血清白蛋白作用的紫外光谱 总被引:18,自引:1,他引:18
用紫外光谱研究了稀土离子(Ⅲ)与牛血清白蛋白(BSA)的作用.14种稀土离子均使BSA~280um特征吸收峰强增加,诱导BSA构象发生改变.紫外差谱结果表明,只有氧原子参加与稀土配位.BSA与稀土配位基团为亲水外壳的氨基酸波基和肽键上的C=O基团. 相似文献
965.
Chenmou Zheng Xinmin Zhang Shan He Qun Fu Deming Lei 《Journal of solid state chemistry》2003,170(2):221-226
V2O3 nanopowder with spherical particles was prepared by reducing pyrolysis of the precursor, (NH4)5[(VO)6(CO3)4(OH)9]·10H2O, in H2 atmosphere. The thermolysis process of the precursor in a H2 flow was investigated by thermogravimetric analysis and differential thermal analysis. The results indicate that pure V2O3 forms at 620°C and crystallizes at 730°C. The effects of various reductive pyrolysis conditions on compositions of V2O3 products were studied. Scanning electron micrographs show that the particles of the V2O3 powder obtained at 650°C for 1 h are spherical about 30 nm in size with more homogeneous distribution. Experiments show that nanopowder has larger adsorption capacity to gases and is more easily reoxidized by air at room temperature than micropowder. Differential scanning calorimetry experiment indicates that the temperature of phase transition of nano-V2O3 powder is −119.5°C on cooling or −99.2°C on heating. The transition heats are −12.55 J g−1 on cooling and 11.42 J g−1 on heating, respectively. 相似文献
966.
967.
Zheng X Mulcahy ME Horinek D Galeotti F Magnera TF Michl J 《Journal of the American Chemical Society》2004,126(14):4540-4542
We describe the preparation of a compound whose molecules consist of two metal sandwich stands carrying tentacles with affinity to metal surfaces and holding an axle that carries a dipolar or a nonpolar rotator. The dipolar rotor exists as three pairs of enantiomers, rapidly interconverting at room temperature. When mounted on a gold surface, each molecule represents a chiral altitudinal rotor, with the rotator axle parallel to the surface. The surface-mounted rotor molecules are characterized by several spectroscopic and imaging techniques. At any one time, in about one-third of the dipolar rotors the rotator is free to turn and the direction of its dipole can be flipped by the electric field applied by an STM tip, as revealed by differential barrier height imaging. Molecular dynamics calculations suggest that electric field normal to the surface causes members of one pair of enantiomers to rotate unidirectionally. 相似文献
968.
This review of ion-selective electrodes is arranged in the same way as Parts I and II. The continuous growth of the whole subject should be noted. Theory has particularly progressed through mechanistic studies. Among new types of electrodes, ISFET systems have become important. Among new applications of both solid and liquid membrane electrodes, the fluoride electrode still predominates, closely followed by potassium electrodes. In the field of biological and medical applications, the steady growth is significant. More than 800 papers published between mid-1976 and the end of 1978 are mentioned in the review. 相似文献
969.
970.
Yu-Fen Zhao De-Qing Zhang Chu-Biao Xue Jia-Ning Zeng Gai-Jiao Ji 《Journal of mass spectrometry : JMS》1991,26(5):510-513
Positive ion fast atom bombardment mass spectrometry of N-diisopropyloxyphosphoryl dipeptides and tripeptides showed a novel cleavage pattern in that only the N-phosphoryl fragment ions gave intense peaks while the C-terminal series of ions was suppressed. The base peak was the N-phosphoryl imino ion responding to the N-terminal residue. These advantages are superior to those of other types of N-protecting groups. 相似文献