全文获取类型
收费全文 | 354篇 |
免费 | 12篇 |
专业分类
化学 | 250篇 |
晶体学 | 4篇 |
力学 | 3篇 |
数学 | 22篇 |
物理学 | 87篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 19篇 |
2012年 | 19篇 |
2011年 | 20篇 |
2010年 | 15篇 |
2009年 | 14篇 |
2008年 | 24篇 |
2007年 | 17篇 |
2006年 | 23篇 |
2005年 | 29篇 |
2004年 | 19篇 |
2003年 | 22篇 |
2002年 | 21篇 |
2001年 | 4篇 |
2000年 | 12篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
排序方式: 共有366条查询结果,搜索用时 31 毫秒
91.
In this paper, we report a novel synthesis of poly(ethylene oxide monooleate-block-DL-lactide) (MOPEO-PLA) in the presence of stannous 2-ethylhexanoate catalyst. By utilizing the surfactant property and the reactive double bond of the amphiphilic MOPEO-PLA, various characteristics of PLA microspheres, such as surface and internal structure, surface morphology, release property, and so on, may potentially be controlled. MOPEO-PLA was found to be hydrophobic enough to prevent loss by dissolution into aqueous solution, which is often a problem for MOPEO. Furthermore, the interfacial tension measurements of a MOPEO-PLA/toluene/water system revealed that MOPEO-PLA had a good surface activity almost equal to that of MOPEO. The MOPEO-PLA/PLA blend films were prepared by solvent casting on a water layer. Contact-angle measurements of MOPEO-PLA/PLA blend films confirmed that the hydrophilic PEO segments were selectivity accumulated at the oil/water interface. Moreover, the surface free energy on the 'water side' of the MOPEO-PLA/PLA blend films was increased because of the increase in polar components as a result of the ether bonds of the PEO segments. Schematic illustration of the adsorption property of a) MOPEO-PLA with a high-molecular-weight PLA segment and b) MOPEO-PLA with a low-molecular-weight PLA segment at an ethyl acetate/water interface. 相似文献
92.
Nakanishi J Kikuchi Y Takarada T Nakayama H Yamaguchi K Maeda M 《Journal of the American Chemical Society》2004,126(50):16314-16315
Cell-culturing substrates where cell adhesion can be switched on by external stimuli during cell cultivation are useful scaffolds for tissue engineering, cell-based drug screening, and fundamental cellular studies. Here, we show a new strategy for photoactivation of a substrate for cell adhesion under standard fluorescence microscopes. A glass substrate chemically modified with an alkylsiloxane having a photocleavable 2-nitrobenzyl group was coated with bovine serum albumin to prevent cell adhesion. Upon irradiation under a fluorescence microscope, the protein was replaced with fibronectin, which made the irradiated region cell-adhesive. Subsequent seeding of HEK293 or COS7 cells produced patterns corresponding to the irradiated patterns. We succeeded for the first time in positioning single cells in proximity to cultivating single cells. The present method provides a general strategy for positioning single cells of same or different types at any locations on the substrate and will be useful for studying cell-cell interactions. 相似文献
93.
94.
Hidekazu Touhara Junichi InaharaTomotaka Mizuno Yu YokoyamaSatoru Okanao Katsuaki YanagiuchIndrajit Mukopadhyay Shinji KawasakiFujio Okino Hirofusa ShiraiW.H. Xu T. KyotaniA. Tomita 《Journal of fluorine chemistry》2002,114(2):181-188
Multiwall carbon nanotubes (MWNTs) based on the template carbonization technique were fluorinated in a temperature range 323-473 K by elemental fluorine. The fluorination of the carbon nanotubes results in functionalization and modification of pristine nanotubes with respect to adsorption and electrochemical properties. Selective fluorination of the inner surface of the carbon nanotubes, brings about a decrease in the surface free energy of the inner surface of the tubes and an increase in colombic efficiency of Li/nanotubes rechargeable cells in an aprotic medium. Electrochemical fluoride-ion doping of fullerene C60 thin films (250-450 nm) was carried out in a fluoride-ion conductive solution, MeCN solution of 1 M Et4NF·4HF. Galvanostatic oxidation yielded C60Fca.1-3 where fluorine exists as a semi-ionic species in the cavity surrounded by C60 molecules without forming covalent CF bonds 相似文献
95.
Yoshimi Ikeuchi Maiko Nakagawa Masakazu Yoshikawa Hidekazu Yoshida Shinichi Sakurai 《Journal of polymer science. Part A, Polymer chemistry》2009,47(10):2530-2538
Novel polyamide with chiral environment was obtained from aromatic diamine, 4,4′‐diaminodiphenylmethane (DADPM), and N‐α‐protected L ‐glutamic acid, N‐α‐benzoyl‐L ‐glutamic acid (Benzoyl‐L ‐Glu‐OH). The optical rotation ([α]D ) of the polyamide was determined to be 3.6° (c = 1.00 g/dL in DMF), implying that the optically active polyamide was obtained. The present polyamide gave a durable self‐standing membrane. The membrane selectively incorporated the D ‐isomer of Ac‐Trp from racemic mixture of Ac‐Trp. The adsorption selectivity toward Ac‐D ‐Trp was determined to be 1.95. It showed chiral separation ability by adopting potential difference as a driving force for membrane transport. The permselectivity was dependent on the potential difference, and at the applied potential difference of 3.0 V, the membrane selectively transported Ac‐D ‐Trp and the permselectivity toward Ac‐D ‐Trp was determined to be 1.84, which was close to the adsorption selectivity of 1.95. Contrary to this, the membrane showed opposite permselectivity at the applied potential difference of 2.0 V and the permselectivity toward the L ‐isomer reached 2.48. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2530–2538, 2009 相似文献
96.
Malek M Morii M Fukuda S Fukuda Y Ishitsuka M Itow Y Kajita T Kameda J Kaneyuki K Kobayashi K Koshio Y Miura M Moriyama S Nakahata M Nakayama S Namba T Okada A Ooyabu T Saji C Sakurai N Shiozawa M Suzuki Y Takeuchi H Takeuchi Y Totsuka Y Yamada S Desai S Earl M Kearns E Messier MD Stone JL Sulak LR Walter CW Goldhaber M Barszczak T Casper D Gajewski W Kropp WR Mine S Liu DW Smy MB Sobel HW Vagins MR Gago A Ganezer KS Keig WE Ellsworth RW Tasaka S Kibayashi A Learned JG Matsuno S Takemori D 《Physical review letters》2003,90(6):061101
A search for the relic neutrinos from all past core-collapse supernovae was conducted using 1496 days of data from the Super-Kamiokande detector. This analysis looked for electron-type antineutrinos that had produced a positron with an energy greater than 18 MeV. In the absence of a signal, 90% C.L. upper limits on the total flux were set for several theoretical models; these limits ranged from 20 to 130 macro nu(e) cm(-2) s(-1). Additionally, an upper bound of 1.2 macro nu(e) cm(-2) s(-1) was set for the supernova relic neutrino flux in the energy region E(nu)>19.3 MeV. 相似文献
97.
The structure elucidation of FR-900098 () isolated from a microorganism source and the syntheses of FR-900098 and its N-formyl analogue, FR-31564 (), are described. The latter possesses a superior antimicrobial activity. 相似文献
98.
Y. Awaya M. Akiba T. Katou Hidekazu Kumagai Y. Tendow K. Izumo T. Takahashi A. Hashizume M. Okano T. Hamada 《Physics letters. A》1977,61(2):111-113
The K X-rays from the target elements due to N-ion bombardment are measured with a crystal spectrometer. Some aspects owing to high incident energy are discussed. The Kα satellite, Kα hypersatellite and Kβ satellite peak spacings are obtained. 相似文献
99.
100.
Lee HM Olmstead MM Suetsuna T Shimotani H Dragoe N Cross RJ Kitazawa K Balch AL 《Chemical communications (Cambridge, England)》2002,(13):1352-1353
A sample of C60 containing ca. 9% Kr@C60 has been used to form crystalline (0.09Kr@C60/0.91C60).(NiII(OEP)).2C6H6 whose X-ray crystal structure reveals that the Kr atom is centered within the carbon cage and does not produce a detectable change in the size of the fullerene. 相似文献