全文获取类型
收费全文 | 729篇 |
免费 | 17篇 |
国内免费 | 5篇 |
专业分类
化学 | 638篇 |
晶体学 | 6篇 |
力学 | 8篇 |
数学 | 16篇 |
物理学 | 83篇 |
出版年
2023年 | 4篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 16篇 |
2018年 | 10篇 |
2017年 | 9篇 |
2016年 | 10篇 |
2015年 | 17篇 |
2014年 | 12篇 |
2013年 | 35篇 |
2012年 | 28篇 |
2011年 | 32篇 |
2010年 | 15篇 |
2009年 | 20篇 |
2008年 | 49篇 |
2007年 | 38篇 |
2006年 | 48篇 |
2005年 | 60篇 |
2004年 | 45篇 |
2003年 | 47篇 |
2002年 | 39篇 |
2001年 | 27篇 |
2000年 | 12篇 |
1999年 | 14篇 |
1998年 | 7篇 |
1995年 | 4篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1977年 | 2篇 |
1976年 | 7篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1972年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有751条查询结果,搜索用时 31 毫秒
61.
Sugita M Yamaguchi A Yamagiwa N Handa S Matsunaga S Shibasaki M 《Organic letters》2005,7(23):5339-5342
[reaction, structure: see text] Chiral Y{N(SiMe3)2}3/linked-BINOL catalyst generated Y-enolate in situ from various hydroxyketones (R2 = aryl, heteroaryl). Beta-amino-alpha-hydroxy ketones (R1 = aryl, heteroaryl, alkenyl) were obtained syn-selectively (up to 96/4) in high ee (up to 98%) and good yield (up to 98% yield). 相似文献
62.
Tanaka Y Hoshino W Shimizu S Youfu K Aratani N Maruyama N Fujita S Osuka A 《Journal of the American Chemical Society》2004,126(10):3046-3047
When heated, bis-Cu(II) octaphyrin(1.1.1.1.1.1.1.1) is quantitatively split into two Cu(II) porphyrins both in solution and film states, which is accompanied by large absorption spectral changes. 相似文献
63.
Takada K Uehara T Nakao Y Matsunaga S van Soest RW Fusetani N 《Journal of the American Chemical Society》2004,126(1):187-193
Three new alpha-glucosidase inhibitors, schulzeines A-C (1-3), were isolated from the marine sponge Penares schulzei. Their structures were elucidated by spectral analysis and chemical degradations to be the isoquinoline alkaloids, encompassing two amino acids, and C(28) fatty acid, the last of which was sulfated. Absolute stereochemistry of schulzeines was determined by application of the modified Mosher analysis to fragments obtained by chemical degradation. Schulzeines A-C inhibit alpha-glucosidase with IC(50) values of 48-170 nM. 相似文献
64.
The synthesis, crystal structures, inclusion ability, and structural robustness of novel crystalline inclusion compounds of [Ni(SCN)2(isoH)2].xG (isoH = isonicotinic acid; G = aromatic guest) are described. The inclusion compounds are constructed by stacking identical 2D host layers that consist of SCN-, isoH, and Ni2+ with van der Waals contact separation. In the layer, two types of rectangular cavities (A-type and B-type) are formed, and the guests are included in the former cavity. The inclusion compounds were categorized into four stacking modes according to the difference in the stacking mode of the layers. A systematic investigation of the crystal structures of the 21 inclusion compounds clarified the close relationship between the molecular structure of the guest and the resultant stacking mode of the layers. 相似文献
65.
Matsunaga S Watanabe S Sakaushi S Miyamura S Hori T 《Photochemistry and photobiology》2003,77(3):324-332
We found diaphototactic behavior (i.e. the cells swim perpendicularly with respect to the incident light) in a strain with colorless eyespot of a unicellular disk-shaped green flagellate Mesostigma viride. Lacking pigments completely in the eyespot, the screening effect in this strain was due only to the central part of the chloroplast whose cross section was thin. The diaphototaxis was most obvious when unilateral green stimulus light (520-580 nm) was given, whereas positive phototaxis appeared when given blue light (430-490 nm). The choice between diaphototaxis and (ordinary) phototaxis depended entirely on the transmission (%T) of the cell body against each wavelength of the stimulus: the green light penetrated well (%T > 90%), whereas the blue light was considerably shaded by the chloroplast (50% < %T < 70%). The fraction of positive phototactically behaving cells against each wavelength was in proportion to the front-to-back contrast value obtained at each individual wavelength. The fraction of diaphototaxis was inversely proportional to it. In addition, bilateral stimulus irradiations to wild-type cell with colored eyespot provided useful information about the principle of the diaphototactic steering. 相似文献
66.
Nishimura S Matsunaga S Shibazaki M Suzuki K Furihata K van Soest RW Fusetani N 《Organic letters》2003,5(13):2255-2257
Massadine, a highly oxygenated alkaloid, was isolated from the marine sponge Stylissa aff. massa as an inhibitor of geranylgeranyltransferase type I (GGTase I). The structure of massadine has been deduced from spectral data. Massidine inhibited GGTase I from Candida albicans with an IC(50) value of 3.9 microM. [structure: see text] 相似文献
67.
68.
Hideaki Matsunaga 《Proceedings of the American Mathematical Society》2008,136(12):4305-4312
For a linear delay differential system with two coefficients and one delay, we establish some necessary and sufficient conditions on the asymptotic stability of the zero solution, which are composed of delay-dependent and delay-independent stability criteria. On the former criterion, the range of the delay is explicitly given.
69.
An ultrahigh vacuum scanning Kelvin probe force microscope (UHV SKPM) based on the gradient of electrostatic force was developed using the technique of a UHV non-contact atomic force microscope (NC-AFM) capable of atomic level imaging, and used for simultaneous observation of contact potential difference (CPD) and NC-AFM images. The CPD images with a potential resolution of less than 10 meV were observed in the UHV SKPM, demonstrating an atomic level resolution. The change of potential corresponding to the charges on the insulated surface of polypropylene have been observed in UHV SKPM. We also demonstrated a reliable method to obtain the CPD from the bias voltage dependence curves of the frequency shift in all of the scanning area. The results are consistent with comparing the barrier height images in that the work functions of adatoms are greater than the work function of corner holes. 相似文献