全文获取类型
收费全文 | 3957篇 |
免费 | 101篇 |
国内免费 | 22篇 |
专业分类
化学 | 3292篇 |
晶体学 | 44篇 |
力学 | 41篇 |
数学 | 169篇 |
物理学 | 534篇 |
出版年
2023年 | 25篇 |
2022年 | 33篇 |
2021年 | 45篇 |
2020年 | 62篇 |
2019年 | 56篇 |
2018年 | 35篇 |
2017年 | 30篇 |
2016年 | 67篇 |
2015年 | 81篇 |
2014年 | 101篇 |
2013年 | 201篇 |
2012年 | 219篇 |
2011年 | 282篇 |
2010年 | 146篇 |
2009年 | 147篇 |
2008年 | 312篇 |
2007年 | 235篇 |
2006年 | 291篇 |
2005年 | 252篇 |
2004年 | 227篇 |
2003年 | 200篇 |
2002年 | 192篇 |
2001年 | 52篇 |
2000年 | 73篇 |
1999年 | 47篇 |
1998年 | 33篇 |
1997年 | 38篇 |
1996年 | 42篇 |
1995年 | 37篇 |
1994年 | 34篇 |
1993年 | 31篇 |
1992年 | 31篇 |
1991年 | 24篇 |
1990年 | 21篇 |
1989年 | 17篇 |
1988年 | 21篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 30篇 |
1984年 | 32篇 |
1983年 | 17篇 |
1982年 | 27篇 |
1981年 | 29篇 |
1980年 | 28篇 |
1979年 | 18篇 |
1978年 | 17篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1975年 | 17篇 |
1974年 | 11篇 |
排序方式: 共有4080条查询结果,搜索用时 15 毫秒
11.
Katsumasa Iwai Yi-Wei Shi Mitsunobu Miyagi Yuji Matsuura 《Optics & Laser Technology》2007,39(8):1528-1531
An improved coating method was proposed in order to form a uniform polymer layer in the fabrication of cyclic olefin polymer-coated silver (COP/Ag) hollow fiber. A COP solution was flowed in a closed loop, in which the silver-coated tube was used as a part of the loop. Owing to the constant flowing speed of the COP solution and the airtight flowing environment, a COP layer was uniformly formed. The hollow fibers attain high performance and deliver multi-wavelength laser light from the infrared to the visible simultaneously. The method was successfully applied to the fabrication of practical hollow fibers with 2 m length for the near and mid-infrared lasers. 相似文献
12.
Hiroyuki Nakazumi Takashi Endo Hikaru Sonoda Teijiro Kitao 《Journal of heterocyclic chemistry》1985,22(3):821-824
3-Substituted 2-phenyl-4H-1-benzothiopyran-4-ones (thioflavones) were prepared to test antimicrobial activity. It was found that 3-(phenyl)thiochromone derivatives (isothioflavones) were prepared by the Meerwein reaction of thiochromone with p-nitrobenzenediazonium ion. 3-(Formyl)thioflavone exhibits weak antimicrobial activity against Trichophytons and Candida. 相似文献
13.
A theory is developed for the potential distribution around a charged spherical colloidal particle carrying ionized groups on the particle surface in a medium containing its counterions (i.e., counterions produced from dissociation of the particle surface groups) and a small amount of added salts on the basis of the theory of Imai and Oosawa. Numerical solutions to the Poisson–Boltzmann equation for the potential distribution are obtained for the case of dilute (but not infinitely dilute) particle suspensions of volume fraction 1 for
a1 (where is the Debye–Hückel parameter and a is the particle radius). Here we have taken into account the effects of (i) counterions from the particle surface groups, and (ii) the finite particle volume fraction. These effects, which are usually neglected in the conventional Poisson–Boltzmann equation, are found to be important. It is found that, as in the case of completely salt-free media, there is a certain critical value of the particle charge (which is the same as that for the completely salt-free case). When the particle charge is lower than the critical value, the potential is given by a Coulomb potential. If the particle charge is higher than the critical value, then counterions are accumulated in the vicinity of the particle surface (counterion condensation) and the potential becomes less dependent on the particle charge. The above behaviors can be observed even for the case where the electrolyte concentration is higher than the concentration of counterions from the particle surface groups, if the conditions
1 and a1are both satisfied. 相似文献
14.
Hiroyuki Ohno 《Tetrahedron letters》2006,47(32):5747-5750
The first total synthesis of dapiramicin B, a nucleoside antibiotic, is described. The characteristic N-glycoside linkage in dapiramicin B was effectively constructed by way of the Pd-catalyzed coupling reaction of a heptopyranosylamine with a bromopyrrolopyrimidine derivative. 相似文献
15.
Tadamasa Shida Yasufumi Takahashi Hiroyuki Hatano Masashi Imamura 《Chemical physics letters》1975,33(3):491-494
Radical-anions of iodine, bromine, and monoiodochloride are produced in γ-irradiated amorphous solids at 77 K, and their electronic and ESR spectra measured. On limited warming of the irradiated solution dimerization by the reaction I2? + I2 → I4? occurs to produce the same species as reported by Fornier de Violet et al. The electronic structure of the dimeric anion is discussed in comparison with the monomeric anion. 相似文献
16.
17.
Proton T1 measurement with the Fourier transform method combined with quenching of dipolar coupling through selective deuterium substitution is shown to be a useful method for elucidating intra- and intermolecular interactions in solution, with 2′,3′-isopropylideneadenosine as an example. Average distances between H-8 and ribose protons are determine in combination with carbon-13 T1 measurement. The method is compared with the nuclear Overhauser effect. 相似文献
18.
Hiroyoshi Kamogawa Hiroyuki Kohno Rikiya Kitagawa 《Journal of polymer science. Part A, Polymer chemistry》1989,27(2):487-495
Polymerizable carbamates were synthesized from 3-vinylphenyl and 2-methacryloyloxyethyl isocyanates and perfume and herbicide alcohols, such as 2-phenethyl alcohol, citronellol, geraniol, 1-menthol, borneol, and 2-(2,4-dichlorophenoxy)- and 2-(2,4,5-trichlorophenoxy)ethyl alcohols. Copolymerization of these carbamate monomers and N-vinyl-2-pyrrolidone with AIBN in dioxane gave respective copolymers. Hydrolyses of both monomers and copolymers, however, required severe acid conditions, although different chemical structures gave different hydrolytic behaviors. 相似文献
19.
In order to investigate the reason why phenylpropanoic acid derivative (KCL), a potent, human peroxisome proliferator-activated receptor (PPAR) alpha-selective agonist, shows this selectivity, we analyzed the binding modes of KCL and a related compound to the ligand-binding domain of human PPARalpha and rat PPARalpha by means of computer-aided molecular modeling. We concluded that the characteristic specificity of KCL is due to a specific hydrophobic contact between the hydrophobic tail part (the 4-trifluoromethyl group) and the key amino acid Ile272 located on the helix three region of the human PPARalpha ligand binding domain. We propose a possible binding mode of KCL with the ligand-binding domain of human PPARalpha. This binding model should offer important insights for further structural design of subtype-selective PPARalpha agonists for the treatment of altered metabolic homeostasis, such as dyslipidemia, obesity, and diabetes. 相似文献
20.
Rotational correlation times (τT) of the 5′-AMP molecule deduced from spin-lattice relaxation times (T1) of different protons in the molecule agree fairly well with each other in the temperature range of 3.5–74°C. The same is true with τT values deduced from 13CT1 values. These results indicate that the internal motions are slow as compared to the overall rotation of the 5′-AMP molecule. 相似文献