全文获取类型
收费全文 | 4589篇 |
免费 | 146篇 |
国内免费 | 16篇 |
专业分类
化学 | 3509篇 |
晶体学 | 34篇 |
力学 | 71篇 |
数学 | 188篇 |
物理学 | 949篇 |
出版年
2023年 | 29篇 |
2022年 | 45篇 |
2021年 | 58篇 |
2020年 | 57篇 |
2019年 | 67篇 |
2018年 | 50篇 |
2017年 | 44篇 |
2016年 | 94篇 |
2015年 | 92篇 |
2014年 | 88篇 |
2013年 | 224篇 |
2012年 | 208篇 |
2011年 | 247篇 |
2010年 | 117篇 |
2009年 | 118篇 |
2008年 | 213篇 |
2007年 | 204篇 |
2006年 | 245篇 |
2005年 | 255篇 |
2004年 | 233篇 |
2003年 | 193篇 |
2002年 | 229篇 |
2001年 | 138篇 |
2000年 | 114篇 |
1999年 | 74篇 |
1998年 | 51篇 |
1997年 | 45篇 |
1996年 | 63篇 |
1995年 | 55篇 |
1994年 | 64篇 |
1993年 | 56篇 |
1992年 | 78篇 |
1991年 | 63篇 |
1990年 | 54篇 |
1989年 | 49篇 |
1988年 | 45篇 |
1987年 | 37篇 |
1986年 | 48篇 |
1985年 | 71篇 |
1984年 | 61篇 |
1982年 | 49篇 |
1981年 | 30篇 |
1980年 | 30篇 |
1979年 | 46篇 |
1978年 | 38篇 |
1977年 | 43篇 |
1976年 | 30篇 |
1975年 | 29篇 |
1974年 | 30篇 |
1973年 | 34篇 |
排序方式: 共有4751条查询结果,搜索用时 31 毫秒
151.
152.
Vitamin E glycosides were synthesized and enzymatic hydrolysis was examined for use as potential pro-drugs, however, the glycoside bond was found to be stable. On the other hand, among the glycosides synthesized, dl-alpha-tocopherylglucoside (6b) and dl-alpha-tocopherylmannoside (6c) showed strong inhibitory action on histamine release from mast cells. In addition, 6c also showed a suppressive action on IgE antibody formation. Thus, tocopheryl glycoside showed new properties compared to tocopherol (vitamin E). In particular, 6c was shown to be a novel lead compound with excellent manifold anti-allergic activity and anti-inflammatory activity. 相似文献
153.
In this letter, we report synthesis of branched polysaccharide 2 by glycosylation of glucal-type monomer 1 with two free hydroxy groups at position 3 and 4. Monomer 1 polymerized with N-halosuccinimide promoter in acetonitrile solvent at room temperature--50 degrees C. The product was isolated as a petroleum ether insoluble fraction. The structure was determined by 1H and 13C NMR spectra as well as elemental analysis to be a polysaccharide consisting of 2-halo-2-deoxy-alpha-D-mannoside units, indicating that the polymerization proceeded via stereoregular glycosylation manner. The molecular weights determined by GPC with DMF were 3,300-4,000. The degree of branching was estimated by the NMR data of the product from the reaction of 2 with 3,5-dinitrobenzoyl chloride. 相似文献
154.
Phenotyping of erythrocyte acid phosphatase (EAP) and esterase D (ESD) by cellulose acetate membrane isoelectric focusing (CAM-IEF) under a nonequilibrium condition is described. In an attempt to improve the method of CAM-IEF, we shortened the electrode distance to provide a higher field strength at a given (low) voltage. Various carrier ampholytes for EAP typing and various chemical separators for ESD typing were also tested. Good separations were obtained after 30 min IEF for EAP typing and 25 min for ESD typing. When applied to blood stains and stored for various periods at room temperature, the stains up to 8 months old could still be phenotyped for EAP and those up to 4 weeks old for ESD. CAM-IEF is suitable for routine forensic work of EAP and ESD phenotyping. 相似文献
155.
Yamamoto Y Yamamoto A Furuta SY Horie M Kodama M Sato W Akiba KY Tsuzuki S Uchimaru T Hashizume D Iwasaki F 《Journal of the American Chemical Society》2005,127(42):14540-14541
The oxidized octaethyltetraphenylporphyrin (1, OETPP) and the corresponding newly prepared octaisobutyltetraphenylporphyrin (3, OisoBuTPP) could be isolated from the reaction of OETPPLi2 (or OisoBuTPPLi2) with SOCl2. The X-ray analysis and the characteristic UV-vis spectra of 1 and 3 revealed that these are the first examples of 16 pi nonaromatic porphyrins. 相似文献
156.
A. Sakaguchi M. Yamamoto M. Hoshi K. N. Apsalikov B. I. Gusev 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(3):543-555
Recent controversies concerning the radiation doses for populations living in the village of Dolon due to the nuclear explosions
carried out at the Semipalatinsk Nuclear Test Site (SNTS) have encouraged us to evaluate in more detail the levels and distributions
of residual long-lived radionuclides137Cs and Pu isotopes (238Pu,239,240Pu) in soils within the village. Soil core samples up to a depth of about 30 cm and/or 100 cm were collected at 25 sites and
subjected to analysis of 137Cs and Pu isotopes. The inventories of 137Cs and 239,240Pu were found to be in the wide range of 790-10,310 and 530-14,320 Bq/m2, respectively. Sequential leaching of Pu from the soil showed that more than ca. 80% of the 239,240Pu was not leached by hot digestion with conc. HNO3 + H2O2, indicating the presence of Pu associated with fused silicates. Further, the presence of hot-particles from the Pu contaminants
by a-track radiography technique using CR-39 polycarbonate was confirmed in the soil, even at present, after about 50 years
from the first nuclear weapon testing.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
157.
A direct preparative route to benzoyltrimethylsilane has been found by the reaction of benzoyl chloride with hexamethyldisilane in the presence of a specified palladium(II) complex as catalyst. 相似文献
158.
159.
160.
The synthetic procedures for spilanthol and trail-following pheromone for a southern subterranean termite were described. The syntheses heavily depend on the new diene synthesis using titanium reagent. 相似文献