全文获取类型
收费全文 | 163篇 |
免费 | 5篇 |
专业分类
化学 | 107篇 |
力学 | 4篇 |
数学 | 6篇 |
物理学 | 51篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 11篇 |
2011年 | 11篇 |
2010年 | 6篇 |
2009年 | 1篇 |
2008年 | 12篇 |
2007年 | 10篇 |
2006年 | 10篇 |
2005年 | 10篇 |
2004年 | 13篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 1篇 |
排序方式: 共有168条查询结果,搜索用时 15 毫秒
41.
Grotjahn DB Sheridan PM Al Jihad I Ziurys LM 《Journal of the American Chemical Society》2001,123(23):5489-5494
Alkali metal amides typically aggregate in solution and the solid phase, and even in the gas phase. In addition, even in the few known monomeric structures, the coordination number of the alkali metal is raised by binding of Lewis-basic solvent molecules, with concomitant changes in structure. In contrast, the simplest lithium amide LiNH(2) has never been made in a monomeric form, even though its structure has been theoretically predicted several times. Here, the first experimental structural data for a monomeric, unsolvated lithium amide are determined using a combination of gas-phase synthesis and millimeter/submillimeter-wave spectroscopy. All data point to a planar structure for LiNH(2). The r(o) structure of LiNH(2) has a Li-N distance of 1.736(3) A, an N-H distance of 1.022(3) A, and a H-N-H angle of 106.9(1) degrees. These results are compared with theoretical predictions for LiNH(2), and experimental data for oligomeric, solid-phase samples, which could not resolve the question of whether LiNH(2) is planar or not. In addition, comparisons are made with revised gas-phase and solid-phase data and calculated structures of NaNH(2). 相似文献
42.
Sheridan RP 《Journal of chemical information and computer sciences》2003,43(3):1037-1050
We have developed a method, given a database of molecules and associated activities, to identify molecular substructures that are associated with many different biological activities. These may be therapeutic areas (e.g. antihypertensive) and/or mechanism-based activities (e.g. renin inhibitor). This information helps us avoid chemical classes that are likely to have unanticipated side effects and also can suggest combinatorial libraries that might have activity on a variety of receptor targets. The method was applied to the USPDI and MDDR databases. There are clearly substructures in each database that occur in many compounds and span a variety of therapeutic categories. Some of these are expected, but some are not. 相似文献
43.
Ten fishmeal samples (hidden duplicates of 4 meals plus 2 high-protein meals as a Youden pair), tryptophan, and nicotinic acid were analyzed by 18 laboratories using the Dumas method. Thirteen of the laboratories also analyzed the same 12 samples using their current Kjeldahl method. Recoveries (+/-SR) of tryptophan and nicotinic acid were 99.3+/-1.04 and 98.8+/-2.11% by Dumas and 97.1+/-3.03 and 74.6+/-26.76% by Kjeldahl. The Dumas method gave significantly greater values (P < 0.001) than the Kjeldahl method. For fishmeals, Kjeldahl N = 0.989 of Dumas N (P < 0.001). A similar proportionate difference (0.984 of Dumas N) was observed with tryptophan. Most laboratories failed to determine nicotinic acid correctly by Kjeldahl. For fishmeals, the relative standard deviations for repeatability and reproducibility were for Dumas 1.48 and 2.01% and Kjeldahl 1.62 and 2.37%, respectively. A single analysis conducted in 2 laboratories should not differ by more than 5.63% of the mean value when measured by Dumas or by more than 6.64% by Kjeldahl. It is concluded that with fishmeal, Dumas gives a more reliable measure of organic nitrogen than Kjeldahl, and, therefore, Dumas should be the method of choice. 相似文献
44.
Yulu Yang Yang Tang Haomin Jiang Yongmei Chen Pingyu Wan Maohong Fan Rongrong Zhang Sana Ullah Lun Pan Ji-Jun Zou Mengmeng Lao Wenping Sun Chao Yang Gengfeng Zheng Qiling Peng Ting Wang Yonglan Luo Xuping Sun Alexander S. Konev Oleg V. Levin Panagiotis Lianos Zhuofeng Hu Zhurui Shen Qinglan Zhao Ying Wang Nadia Todorova Christos Trapalis Matthew V. Sheridan Haipeng Wang Ling Zhang Songmei Sun Wenzhong Wang Jianmin Ma 《中国化学快报》1990,30(12):2089-2109
In this roadmap, we address the development and perspectives of hydrogen evolution reaction, oxygen reduction reaction, oxygen evolution reaction, carbon dioxide reduction reaction and nitrogen reduction. 相似文献
45.
Mosley RT Culberson JC Kraker B Feuston BP Sheridan RP Conway JF Forbes JK Chakravorty SJ Kearsley SK 《Journal of chemical information and modeling》2005,45(5):1439-1446
Reagent Selector is an intranet-based tool that aids in the selection of reagents for use in combinatorial library construction. The user selects an appropriate reagent group as a query, for example, primary amines, and further refines it on the basis of various physicochemical properties, resulting in a list of potential reagents. The results of this selection process are, in turn, converted into synthons: the fragments or R-groups that are to be incorporated into the combinatorial library. The Synthon Analysis interface graphically depicts the chemical properties for each synthon as a function of the topological bond distance from the scaffold attachment point. Displayed in this fashion, the user is able to visualize the property space for the universe of synthons as well as that of the synthons selected. Ultimately, the reagent list that embodies the selected synthons is made available to the user for reagent procurement. Application of the approach to a sample reagent list for a G-protein coupled receptor targeted library is described. 相似文献
46.
Douglas L Sheridan Catherine H Berlot Antoine Robert Fiona M Inglis Klara B Jakobsdottir James R Howe Thomas E Hughes 《BMC neuroscience》2002,3(1):7-11
Background
The jellyfish green fluorescent protein (GFP) can be inserted into the middle of another protein to produce a functional, fluorescent fusion protein. Finding permissive sites for insertion, however, can be difficult. Here we describe a transposon-based approach for rapidly creating libraries of GFP fusion proteins. 相似文献47.
48.
High-resolution laser excitation spectroscopy has been used to record the A (2)E-X (2)A(1) electronic transition of SrCH(3) in a laser ablation/molecular jet source. Transitions arising from the K(')=1<--K(")=0, K(')=0<--K(")=1, and K(')=2<--K(")=1 subbands have been observed and assigned. The data were modeled with (2)E and (2)A(1) symmetric top Hamiltonian matrices in a Hund's case (a) basis, using a least squares fitting program. Rotational and fine structure parameters for the A (2)E state were determined. A comparison of the spin-orbit energy separation in the A (2)E state to other strontium containing free radicals showed that the Jahn-Teller effect is negligible. The spin-rotation constants for the A (2)E state were calculated using the pure precession model and were found to be in good agreement with the experimentally determined parameters. These calculations suggest that the A (2)E state of SrCH(3) is not entirely of p orbital character. The rotational constants were used to estimate the structural parameters of SrCH(3) in the A (2)E state. The strontium-carbon bond length was found to decrease by approximately 0.006 A, and the hydrogen-carbon-hydrogen bond angle opened by approximately 0.8 degrees compared to the X (2)A(1) state, similar to the geometry changes observed for CaCH(3). 相似文献
49.
Moss SJ Carletti I Olano C Sheridan RM Ward M Math V Nur-E-Alam M Braña AF Zhang MQ Leadlay PF Méndez C Salas JA Wilkinson B 《Chemical communications (Cambridge, England)》2006,(22):2341-2343
We report the directed biosynthesis of borrelidin analogues and their selective anti-proliferative activity against human cancer cell lines. 相似文献
50.