全文获取类型
收费全文 | 2530篇 |
免费 | 175篇 |
国内免费 | 10篇 |
专业分类
化学 | 2058篇 |
晶体学 | 32篇 |
力学 | 23篇 |
数学 | 142篇 |
物理学 | 460篇 |
出版年
2023年 | 30篇 |
2022年 | 31篇 |
2021年 | 42篇 |
2020年 | 67篇 |
2019年 | 77篇 |
2018年 | 47篇 |
2017年 | 30篇 |
2016年 | 108篇 |
2015年 | 92篇 |
2014年 | 98篇 |
2013年 | 134篇 |
2012年 | 204篇 |
2011年 | 244篇 |
2010年 | 94篇 |
2009年 | 90篇 |
2008年 | 158篇 |
2007年 | 148篇 |
2006年 | 159篇 |
2005年 | 139篇 |
2004年 | 100篇 |
2003年 | 75篇 |
2002年 | 65篇 |
2001年 | 34篇 |
2000年 | 29篇 |
1999年 | 21篇 |
1998年 | 16篇 |
1997年 | 13篇 |
1996年 | 17篇 |
1995年 | 22篇 |
1994年 | 15篇 |
1993年 | 12篇 |
1992年 | 27篇 |
1991年 | 10篇 |
1990年 | 22篇 |
1989年 | 14篇 |
1988年 | 19篇 |
1987年 | 16篇 |
1986年 | 16篇 |
1985年 | 14篇 |
1984年 | 20篇 |
1982年 | 16篇 |
1981年 | 7篇 |
1979年 | 15篇 |
1978年 | 21篇 |
1977年 | 18篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 6篇 |
1967年 | 5篇 |
排序方式: 共有2715条查询结果,搜索用时 9 毫秒
1.
Watanabe Sou Senzaki Tatsuya Shibata Atsuhiro Nomura Kazunori Takeuchi Masayuki Nakatani Kiyoharu Matsuura Haruaki Horiuchi Yusuke Arai Tsuyoshi 《Journal of Radioanalytical and Nuclear Chemistry》2019,322(3):1273-1277
Journal of Radioanalytical and Nuclear Chemistry - Extraction chromatography flow-sheet employing octyl(phenyl)-N,N-diisobutylcarbonoylmethylphosphine oxide and bis(2-ethylhexyl) hydrogen phosphate... 相似文献
2.
Direct Addition of Amides to Glycals Enabled by Solvation‐Insusceptible 2‐Haloazolium Salt Catalysis
Yuya Nakatsuji Yusuke Kobayashi Yoshiji Takemoto 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14253-14257
The direct 2‐deoxyglycosylation of nucleophiles with glycals leads to biologically and pharmacologically important 2‐deoxysugar compounds. Although the direct addition of hydroxyl and sulfonamide groups have been well developed, the direct 2‐deoxyglycosylation of amide groups has not been reported to date. Herein, we show the first direct 2‐deoxyglycosylation of amide groups using a newly designed Brønsted acid catalyst under mild conditions. Through mechanistic investigations, we discovered that the amide group can inhibit acid catalysts, and the inhibition has made the 2‐deoxyglycosylation reaction difficult. Diffusion‐ordered two‐dimensional NMR spectroscopy analysis implied that the 2‐chloroazolium salt catalyst was less likely to form aggregates with amides in comparison to other acid catalysts. The chlorine atom and the extended π‐scaffold of the catalyst played a crucial role for this phenomenon. This relative insusceptibility to inhibition by amides is more responsible for the catalytic activity than the strength of the acidity. 相似文献
3.
4.
Modular and quasimodular solutions of a specific second order differential equation in the upper-half plane, which originates from a study of supersingular j-invariants in the first author's work with Don Zagier, are given explicitly. Positivity of Fourier coefficients of some of the solutions as well as a characterization of the differential equation are also discussed. 相似文献
5.
6.
It is shown that if in a simple graph G of order n the sum of degrees of any three pairwise non-adjacent vertices is at least n, then there are two cycles (or one cycle and an edge or a vertex) of GF that contain all the vertices. © 1995 John Wiley & Sons, Inc. 相似文献
7.
A side-chain liquid crystalline polysiloxane derivative possessing mesogens was synthesized. The mesogens included a large dielectrically-anisotropic moiety. Phase transition behaviour was investigated and the electrorheological (ER) effect of the polymer considered. No ER effect was observed in non-sheared polysiloxane derivative because of its high inherent viscosity. However, a large ER effect was observed after pre-shearing. Pre-shearing, i.e. shearing with a high shear rate before the measurements, arranges the terminal mesogens in the shearing direction. Furthermore, a dilution of the sample led to a larger ER effect exceeding 10 000 Pa. We thus were able to demonstrate a new approach for the appearance of the ER effect. 相似文献
8.
D. Kaneko T. Narita J. P. Gong Y. Osada J. Ando K. Yamamoto S. Ohnishi V. V. Yaminsky 《Journal of Polymer Science.Polymer Physics》2003,41(22):2808-2815
The effect of the shear flow on the thickness change of a polyelectrolyte membrane grafted onto a glass substrate was directly investigated with a flow cell combined with a confocal laser scanning microscope. The membrane thickness decreased proportionally to an increase in the shear stress of the flow when the shear rate exceeded a critical value of 1 s?1. The higher the ionic strength was of the fluid, the greater the thinning effect was. The correlation between the critical shear rate and the relaxation of the polymer in the gel membrane was examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2808–2815, 2003 相似文献
9.
Maki Onoda Takefumi Uchiyama Ken-Ichi Mawatari Kiyoko Kaneko Kazuya Nakagomi 《Analytical sciences》2006,22(6):815-817
A simple batch method for the fluorometric determination of hydrogen peroxide using phosphine-based fluorescent reagents has been developed. A rapid, mild and selective derivatization reaction was achieved by adding sodium tungstate dihydrate to the reaction mixture of hydrogen peroxide and a phosphine-based fluorescent reagent. When 4-diphenylphosphino-7-methylthio-2,1,3-benzoxadiazole was used as a reagent, the derivatization reaction was completed after 2 min at room temperature. The calibration curve was linear between 12.5 and 500 ng hydrogen peroxide in a 10 microL sample solution. This method is accurate and has potential for on-line applications. 相似文献
10.
(Triisopropylsilyl)acetaldehyde dimethyl acetal (TIPS-ADMA) was synthesized from chlorotriisopropylsilane in three steps. Cyclic and acyclic 1,2-diols can be transformed to (triisopropylsilyl)ethylidene acetals (TIPS-AA). Removal of the acetal by LiBF4 regenerates the starting diol in excellent yield even in the presence of an acetonide of 1,2-diol. The TIPS-AA group can survive under the deprotection conditions of the acetonide in acetic acid at 80 °C. Selective protection of 2,3- and 4,6-diols for O-methyl d-mannoside with TIPS-ADMA and selective deprotection of the acetals have been achieved. 相似文献