全文获取类型
收费全文 | 649篇 |
免费 | 23篇 |
国内免费 | 1篇 |
专业分类
化学 | 531篇 |
晶体学 | 10篇 |
力学 | 5篇 |
数学 | 28篇 |
物理学 | 99篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2018年 | 8篇 |
2017年 | 2篇 |
2016年 | 12篇 |
2015年 | 15篇 |
2014年 | 12篇 |
2013年 | 31篇 |
2012年 | 30篇 |
2011年 | 40篇 |
2010年 | 19篇 |
2009年 | 22篇 |
2008年 | 36篇 |
2007年 | 36篇 |
2006年 | 41篇 |
2005年 | 44篇 |
2004年 | 41篇 |
2003年 | 29篇 |
2002年 | 16篇 |
2001年 | 25篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 12篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 3篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 12篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 9篇 |
1974年 | 6篇 |
1971年 | 4篇 |
排序方式: 共有673条查询结果,搜索用时 984 毫秒
161.
162.
Matsuda H Fujimoto Y Ito S Nagasawa Y Miyasaka H Asahi T Masuhara H 《The journal of physical chemistry. B》2006,110(3):1091-1094
Femtosecond near-infrared laser microscope was developed with a home-built cavity-dumped chromium:forsterite laser as a light source centered at 1.26 microm. Optimization of the pulse duration achieved 35 fs fwhm at the sample position of the microscope after passing through a 100x objective. This system was applied to the detection of multiphoton fluorescence of some organic microcrystals. Excitation intensity dependence and the interferometric autocorrelation detection of the fluorescence clearly demonstrated that simultaneous three- and four-photon absorption processes are responsible for the production of the excited state for perylene and anthracene microcrystals, respectively. The spatial resolution along the optical axis and its dependence on the order of the multiphoton process were also discussed. 相似文献
163.
Nagatani H Suzuki S Fermín DJ Girault HH Nakatani K 《Analytical and bioanalytical chemistry》2006,386(3):633-638
The transfer mechanism of an amphoteric rhodamine, sulforhodamine 101 (SR101), across the polarized water/1,2-dichloroethane
(DCE) interface was investigated using cyclic voltammetry, differential voltfluorometry and potential-modulated fluorescence
(PMF) spectroscopy. The voltammetric response for the ion transfer of SR101 monoanion from water to DCE was observed as the
diffusion-controlled transfer process. An unusual voltammetric response was found at 0.15 V more negative than the formal
transfer potential of SR101−
in the cyclic voltammogram and voltfluorogram. The frequency dependence of the PMF responses confirmed the presence of the
adsorption processes at negative potentials. In addition, a further transient adsorption step was uncovered at The interfacial mechanism of SR101 is discussed by comparing the results obtained from each technique. 相似文献
164.
We have achieved a total synthesis of telomestatin, and its absolute configuration was determined to be (R). Coupling of cysteine-containing trisoxazole amine and serine-containing trisoxazole carboxylic acid, followed by macrocyclization, provided a 24-membered diamide. The seventh oxazole ring was formed by a Shin's procedure via dehydroamide. Cyclodehydration of a modified (R)-cysteine-(S-(t)Bu) moiety using Kelly's method (PPh3(O)-Tf2O) with anisole furnished (R)-telomestatin, whose CD spectrum was in good agreement with that of the natural product. 相似文献
165.
The adsorption behavior of PHB depolymerase from R. pickettii T1 on a silicon wafer and on P(3HB) single crystals has been studied by real-time and AFM in air and a buffer solution. First, the morphology of PHB depolymerase adsorbed on a silicon wafer was characterized to show that one molecule of PHB depolymerase has dimensions of 2.2 +/- 0.7 nm height and 16 +/- 5 nm width. The observation of PHB depolymerase adsorbed on a P(3HB) single crystal indicated that the dimensions of enzyme on the crystalline surface in air were 1.2 +/- 0.5 nm high and 28 +/- 7 nm wide, while enzyme molecules with dimensions of 2.1 +/- 0.6 nm height and 16 +/- 7 nm width were detected in a buffer solution. Comparison of the dimensions of PHB depolymerase in air with those in a buffer solution showed that the enzyme was squashed in air, but not in a buffer solution. In addition, the influence of enzymatic adsorption on the molecular state of the P(3HB) crystalline surface was investigated. The AFM images of P(3HB) single crystals after enzymatic adsorption and washing with ethanol indicated that the adhesion of PHB depolymerase changed the molecular state and generated holes on the crystalline surface. 相似文献
166.
A Lamb wave interdigital transducer mounted on a layered substrate composed of two plates, a thin piezoelectric ceramic plate and an acrylic plate, operating at a liquid-solid boundary, is investigated for ultrasonic nondestructive testing of the layer thickness in human teeth. A higher-order mode having a phase velocity higher than the longitudinal wave velocity in the human teeth can be used for nondestructive testing. In the combination of the two layers, the fourth mode of leaky Lamb wave is most favorable for a frequency-controllable radiation angle of an ultrasound beam into a water layer as an acoustic coupler. In the configuration of an acoustic delay line, the layer-thickness measurement in vivo, evaluated from the time interval between two reflected ultrasound echoes, is successfully realized under a thin water layer as the acoustic coupler. 相似文献
167.
Leonardo de Oliveira Martins Hirohisa Kishino 《Annals of the Institute of Statistical Mathematics》2010,62(1):145-159
Inferences about the evolutionary history of biological sequence data are greatly influenced by the presence of recombination,
that tends to disrupt the phylogenetic signal. Current recombination detection procedures focus on the phylogenetic disagreement
of the data along the aligned sequences, but only recently the link between the quantification of this disagreement and the
strength of the recombination was realised. We previously described a hierarchical Bayesian procedure based on the distance
between topologies of neighbouring sites and a Poisson-like prior for these distances. Here, we confirm the improvement provided
by this topology distance and its prior over existing methods that neglect this information by analysing datasets simulated
under a complex evolutionary model. We also show how to obtain a mosaic structure representative of the posterior sample based
on a newly developed centroid method. 相似文献
168.
Kou Hiroya Yusuke Ichihashi Yoshihiro Suwa Tetsuro Ikai Kiyofumi Inamoto Takayuki Doi 《Tetrahedron letters》2010,51(29):3728-3731
The C2-side chain hydroxyl group of 1,3-cycloalkanedione discriminates between two ketones depending on its chirality. It chooses one ketone to form hydrogen bond with the oxygen atom of the TBDPS-oxymethyl group, but chooses the other ketone upon conversion to the isopropyl acetal. Two optically pure diastereomers, whose absolute configuration at the angular position is opposite for each other, were thus synthesized from this single chiral source through simple operations. This method may be applied for the synthesis of a variety of compounds with asymmetric quaternary centers. 相似文献
169.
Nagai K Doi T Sekiguchi T Namatame I Sunazuka T Tomoda H Omura S Takahashi T 《Journal of combinatorial chemistry》2006,8(1):103-109
Synthesis of beauveriolide III (1b), which is an inhibitor of lipid droplet accumulation in macrophages, was achieved by solid-phase assembly of linear depsipeptide using a 2-chlorotrityl linker followed by solution-phase cyclization. On the basis of this strategy, a combinatorial library of beauveriolide analogues was carried out by radio frequency-encoded combinatorial chemistry. After automated purification using preparative reversed-phase HPLC, the library was tested for inhibitory activity of CE synthesis in macrophages to determine structure-activity relationships of beauveriolides. Among them, we found that diphenyl derivative 7{9,1} is 10 times more potent than 1b. 相似文献
170.
A 24-member combinatorial library based on the structure of aeruginosin 298-A (1a) was synthesized utilizing solid-phase, and their inhibitory activity against trypsin was evaluated. Among the library, we found that D-Hpla-D-Leu-L-Choi-Agma (1h) is 300 times more potent than the parent natural product 1a. 相似文献