全文获取类型
收费全文 | 3870篇 |
免费 | 77篇 |
国内免费 | 13篇 |
专业分类
化学 | 2690篇 |
晶体学 | 46篇 |
力学 | 64篇 |
数学 | 201篇 |
物理学 | 959篇 |
出版年
2021年 | 24篇 |
2020年 | 48篇 |
2019年 | 52篇 |
2018年 | 42篇 |
2017年 | 25篇 |
2016年 | 51篇 |
2015年 | 61篇 |
2014年 | 74篇 |
2013年 | 169篇 |
2012年 | 152篇 |
2011年 | 196篇 |
2010年 | 127篇 |
2009年 | 120篇 |
2008年 | 208篇 |
2007年 | 221篇 |
2006年 | 214篇 |
2005年 | 151篇 |
2004年 | 142篇 |
2003年 | 151篇 |
2002年 | 151篇 |
2001年 | 111篇 |
2000年 | 130篇 |
1999年 | 79篇 |
1998年 | 54篇 |
1997年 | 57篇 |
1996年 | 48篇 |
1995年 | 44篇 |
1994年 | 45篇 |
1993年 | 60篇 |
1992年 | 49篇 |
1991年 | 49篇 |
1990年 | 39篇 |
1989年 | 50篇 |
1988年 | 50篇 |
1987年 | 44篇 |
1986年 | 36篇 |
1985年 | 54篇 |
1984年 | 55篇 |
1983年 | 50篇 |
1982年 | 46篇 |
1981年 | 33篇 |
1980年 | 36篇 |
1979年 | 49篇 |
1978年 | 45篇 |
1977年 | 50篇 |
1976年 | 19篇 |
1975年 | 27篇 |
1974年 | 30篇 |
1972年 | 15篇 |
1967年 | 16篇 |
排序方式: 共有3960条查询结果,搜索用时 397 毫秒
891.
T. Shinohara M. Fujioka H. Onodera K. Hisatake H. Yamamoto H. Watanabe 《Hyperfine Interactions》1975,1(1):345-360
From internal conversion experiments and the Mössbauer effect measurements, the 4s electron density and isomer shift for Fe impurity atoms in Cr, Ni, Cu, Pt and Au metals were studied. The M and N shell conversion electron spectra of the 14.4 keV transition of57Fe were measured using a high resolution β-ray spectrometer and analyzed using a deconvolution methods. The Mössbauer effect measurements were performed by a standard spectrometer with a moving absorber. Most of the samples showed isomer shift values consistent with the published ones. It is concluded that the 4s electron density, \(\rho _{4_S} (0)\) , at the nucleus of57Fe embedded is nearly equal in these host metals. The relation between \(\rho _{4_S} (0)\) and the isomer shift indicates that \(\rho _{3_S} (0)\) plays an important role in the variation of the isomer shift. 相似文献
892.
Hiroshi Watanabe 《Journal of statistical physics》1989,54(1-2):171-190
A block spin approach to the Euclidean
4 field theory in three dimensions is proposed by using the three-dimensional version of Gawedzki and Kupiainen's block spin transformation method. The lattice
3
4
model recovers the rotation invariance in the continuum limit, when the coupling constant is small. 相似文献
893.
894.
Suzuki M Watanabe K Fujiwara S Kurasawa T Wakabayashi T Tsuzuki M Iguchi K Yamori T 《Chemical & pharmaceutical bulletin》2003,51(6):724-727
Two norcarotenoids, 1 and 2, related to peridinin (3) were isolated from the cultured dinoflagellate of the genus Symbiodinium, a symbiont of the Okinawan soft coral Clavularia viridis, which contains in abundance antitumor marine prostanoids such as clavulones. The structures of 1 and 2 were elucidated on the basis of spectroscopic analysis. These compounds showed significant growth-inhibitory activity in vitro toward cancer cells. Analysis of fatty acids of the dinoflagellate was also carried out, suggesting that the marine prostanoids are produced by the host soft coral itself. 相似文献
895.
Kunishima M Yamamoto K Watanabe Y Hioki K Tani S 《Chemical communications (Cambridge, England)》2005,(21):2698-2700
A novel immobilized dehydrocondensing reagent comprised of a triazine-type dehydrocondensing reagent itself in a polymerized form was synthesized by copolymerization between tetra(ethylene glycol) bis(dichlorotriazinyl) ether and tris(2-aminoethyl)amine. 相似文献
896.
Kiyoshi Shibata Hiroshi Kimura Akira Tsuchida Tsuneo Okubo Shohei Sato Kohji Yoshinaga 《Colloid and polymer science》2006,284(4):372-379
Electro-optic responses of colloidal crystals consist of poly(maleic anhydride-co-styrene)-modified silica spheres (P(MA-ST)/SiO2) in acetonitrile and the crystals immobilized with a gelator, N-benzyloxycarbonyl-L-isoleucilaminooctadecane (Z-L-Ile-C-18), are studied by reflected-light intensity measurements and time-resolved reflection spectroscopy. Application of
an alternating electric field deforms P(MA-ST)/SiO2 crystal lattices reversibly. The response waveforms from the crystals are dependent on the frequency and strength of the
applied electric field; similar dependencies have been qualitatively observed for the colloidal crystals consisting of polystyrene
or silica spheres in aqueous media in our previous studies. Both gelated and ungelated P(MA-ST)/SiO2 crystals change the reflection intensity, however, the amplitude is larger for the latter. The small response for the gelated
P(MA-ST)/SiO2 crystals is attributed to the higher elastic modulus (G). The G value of the gelated P(MA-ST)/SiO2 crystals in acetonitrile is estimated from the change in the inter-sphere distance to be 8.0 Pa, which is about 2.3 and 2.4
times larger than that for ungelated P(MA-ST)/SiO2 crystals in acetonitrile and colloidal silica crystals in aqueous media, respectively. 相似文献
897.
8-Fluorocarbapenem derivatives having various C-3 side chains were synthesized to study for the structure-activity relationship of carbapenems by in vitro biological evaluation. The introduction of fluorine at C-8 of racemic PS-5 led to slight improvements of the antimicrobial activity and the stability to renal dehydropeptidase-I. When D-cysteine was additionally introduced to the C-3 position of (+/-)-8-fluorocarbapenem, the diastereomeric separation of the 8-fluorocarbapenems became feasible. As expected from penicillins and cephalosporins, (+)-8-fluoro-3-D-cysteinylcarbapenem (+)-7a was antimicrobially active, whereas (-)-7b was inactive. It is worth noting, however, that (+)-7a was significantly more sensitive to renal dehydropeptidase-I than (-)-7b. Irrespective of the presence of fluorine at C-8, basic S-side chains at C-3, such as the pyridyl and pyrrolidyl groups, significantly improved in antimicrobial activity and dehydropeptidase-I stability. The combination of 8-fluorination with C-3 basic side chains in 7c--g resulted in a marked improvement of antimicrobial activity and dehydropeptidase-I stability. 相似文献
898.
S. Arai T. Watanabe Y. Ishikawa T. Oyama O. Hayashi T. Ishii 《Chemical physics letters》1984,112(3):224-227
The infrared multiple-photon decomposition of mixtures of C2F6 and Br2 has been examined as functions of various experimental parameters. Carbon-13 was found to be enriched in the main product CF3Br; the maximum enrichment factor was 35. The combination of this process with the IRMPD of CF3Br provides a closed chemical cycle for efficient carbon isotope separation 相似文献
899.
H Hoshi S Nakayama T Kodama S Jinnouchi K Nishikawa Y Wakuta Y Kakitsubata T Kusuhara K Watanabe 《Radioisotopes》1983,32(1):13-17
Serum ferritin levels were studied in 264 patients who were consisted of 153 patients with various malignant neoplasms and 111 patients with various benign diseases. Positive rate of serum ferritin in all patients with malignant neoplasms was 35%. Hepatomas and pulmonary cancer showed relatively high positive rate, respectively 65% and 42%. In patients with benign diseases, hepatic diseases showed the high positive rate (52%) and the other benign diseases was low positive rate (11%). The relationship between serum ferritin and alpha-feto-protein in patients with hepatomas and other liver diseases was low. And the relationship between serum ferritin and CEA (carcinoembryonic antigen) in patients with malignant neoplasms of gastrointestinal tract was also low. It seemed that the measurement of serum ferritin levels will be of low value in the differentiation of the patients with malignant neoplasms. 相似文献
900.
Kohji Tashiro 《高分子科学》2007,(1):73-82
The crystalline phase transition of aliphatic nylon 10/10 has been investigated on the basis of the simultaneous measurement of wide-angle and small-angle X-ray scatterings, the infrared spectral measurement and the molecular dynamics calculation. An interpretation of infrared spectra taken for a series of nylon samples and the corresponding model compounds was successfully made, allowing us to assign the infrared bands of the planar-zigzag methylene segments reasonably. As a result the methylene segmental parts of molecular chains were found to experience an order-to-disorder transition in the Brill transition region, where the intermolecular hydrogen bonds are kept alive although the bond strength becomes weaker at higher temperature. The small-angle X-ray scattering data revealed a slight change in lamellar stacking mode in the transition region. The crystal structure has been found to change more remarkably in the temperature region immediately below the melting point, where the conformationally disordered chains experienced drastic rotational and translational motions without any constraints by hydrogen bonds, and the lamellar thickness increased largely along the chain axis. These experimental results were reasonably reproduced by the molecular dynamics calculation performed at the various temperatures. 相似文献