全文获取类型
收费全文 | 969篇 |
免费 | 38篇 |
国内免费 | 3篇 |
专业分类
化学 | 778篇 |
晶体学 | 11篇 |
力学 | 9篇 |
数学 | 60篇 |
物理学 | 152篇 |
出版年
2023年 | 9篇 |
2022年 | 13篇 |
2021年 | 14篇 |
2020年 | 22篇 |
2019年 | 25篇 |
2018年 | 20篇 |
2017年 | 9篇 |
2016年 | 15篇 |
2015年 | 30篇 |
2014年 | 25篇 |
2013年 | 48篇 |
2012年 | 71篇 |
2011年 | 79篇 |
2010年 | 46篇 |
2009年 | 41篇 |
2008年 | 83篇 |
2007年 | 72篇 |
2006年 | 73篇 |
2005年 | 47篇 |
2004年 | 49篇 |
2003年 | 43篇 |
2002年 | 40篇 |
2001年 | 7篇 |
2000年 | 15篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1974年 | 7篇 |
1972年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有1010条查询结果,搜索用时 0 毫秒
971.
972.
The irregular demand and communication network disruption that are characteristics of situations demanding humanitarian logistics, particularly after large-scale earthquakes, present a unique challenge for relief inventory modelling. However, there are few quantitative inventory models in humanitarian logistics, and assumptions inherent in commercial logistics naturally have little applicability to humanitarian logistics. This paper develops a humanitarian disaster relief inventory model that assumes a uniformly distributed function in both lead-time and demand parameters, which is appropriate considering the limited historical data on relief operation. Furthermore, this paper presents different combinations of lead-time and demand scenarios to demonstrate the variability of the model. This is followed by the discussion of a case study wherein the decision variables are evaluated and sensitivity analysis is performed. The results reveal the presence of a unique reorder level in the inventory wherever the order quantity is insensitive to some lead-time demand values, providing valuable direction for humanitarian relief planning efforts and future research. 相似文献
973.
Koji TANABE Kazutoshi TAKAHASHI Shinya YAMANAKA 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2014,90(3):83-96
The “reversion of cell fate from differentiated states back into totipotent or pluripotent states” has been an interest of many scientists for a long time. With the help of knowledge accumulated by those scientists, we succeeded in converting somatic cells to a pluripotent cell lineage by the forced expression of defined factors. These established induced pluripotent stem (iPS) cells have similar features to embryonic stem (ES) cells, including pluripotency and immortality. The iPS cell technology provides unprecedented opportunities for regenerative medicine and drug discovery. 相似文献
974.
Kimata M Terashima T Kurita N Satsukawa H Harada A Kodama K Takehana K Imanaka Y Takamasu T Kihou K Lee CH Kito H Eisaki H Iyo A Fukazawa H Kohori Y Harima H Uji S 《Physical review letters》2011,107(16):166402
Cyclotron resonance (CR) measurements for the Fe-based superconductor KFe(2)As(2) are performed. One signal for CR is observed, and is attributed to the two-dimensional α Fermi surface at the Γ point. We found a large discrepancy in the effective masses of CR [(3.4±0.05)m(e) (m(e) is the free-electron mass)] and de Haas-van Alphen results, a direct evidence of mass enhancement due to electronic correlation. A comparison of the CR and de Haas-van Alphen results shows that both intra- and interband electronic correlations contribute to the mass enhancement in KFe(2)As(2). 相似文献
975.
Ampere A. Tseng Chung-Feng Jeffrey KuoShyankay Jou Shinya NishimuraJun-ichi Shirakashi 《Applied Surface Science》2011,257(22):9243-9250
The nanoscaled tip in an AFM (atomic force microscope) has become an effective scratching tool for material removing in nanofabrication. In this article, the characteristics of using a diamond-coated pyramidal tip to scratch Ni-Fe thin film surfaces was experimentally investigated with the focus on the evaluation of the influence of the scratch or scan direction on the final shape of the scratched geometry as well as the applied scratch force. Results indicated that both the scratched profile and the scratch force were greatly affected by the scratch direction. It has been found that, to minimize the formation of protuberances along the groove sides and to have a better control of the scratched geometry, the tip face should be perpendicular to the scratching direction, which is also known as orthogonal cutting condition. To demonstrate the present findings, three groove patterns have been scratched with the tip face perpendicular to the scratching direction and very little amount of protuberances was observed. The threshold scratch force was also predicted based on the Hertz contact theory. Without considering the surface friction and adhesive forces between the tip and substrate, the threshold force predicted was twice smaller than the measurement value. Finally, recommendations for technical improvement and research focuses are provided. 相似文献
976.
The high-resolution infrared spectrum of N212C18O2 has been observed in the ν3 band (2314 cm?1) region of 12C18O2 with diode laser absorption spectroscopy of pulsed molecular beam. The geometry of N212C18O2 is similar to N212C16O2, a T-shaped structure with the nitrogen molecular axis pointing towards the carbon atom. The geometrical parameters of the T-shaped ground-state structure are determined as RNcmC = 3.7285(5) Å and (90?ΘNcmCO) = 6.85(3)°. The vibrational band origin of N212C18O2 corresponding to the ν3 mode of 12C18O2 shows a shift of 0.52499(10) cm?1 with respect to that of 12C18O2. 相似文献
977.
Takaishi S Wu H Kajiwara T Breedlove BK Miyasaka H Yamashita M 《Dalton transactions (Cambridge, England : 2003)》2011,40(10):2160-2162
In STM images of [Pd(chxn-d(4))(2)Br]Br(2), which is in a quasi-2D-CDW state, we observed domain wall migration due to fast soliton motion at neighboring chains to the domain wall. 相似文献
978.
Hayami S Kato K Komatsu Y Fuyuhiro A Ohba M 《Dalton transactions (Cambridge, England : 2003)》2011,40(10):2167-2169
The cobalt(II) compounds with long alkyl chains, [Co(C12-terpy)(2)](BF(4))(2)·EtOH·0.5H(2)O(1·EtOH·0.5H(2)O) and [Co(C12-terpy)(2)](BF(4))(2) (1) was synthesized and characterized. The compound 1·EtOH·0.5H(2)O exhibits a "re-entrant spin crossover". The compound 1 exhibits the reentrant spin crossover and multi phase transitions with a wide thermal hysteresis loop. 相似文献
979.
Graphene and carbon nanotube composite electrodes for supercapacitors with ultra-high energy density 总被引:2,自引:0,他引:2
Cheng Q Tang J Ma J Zhang H Shinya N Qin LC 《Physical chemistry chemical physics : PCCP》2011,13(39):17615-17624
We describe a graphene and single-walled carbon nanotube (SWCNT) composite film prepared by a blending process for use as electrodes in high energy density supercapacitors. Specific capacitances of 290.6 F g(-1) and 201.0 F g(-1) have been obtained for a single electrode in aqueous and organic electrolytes, respectively, using a more practical two-electrode testing system. In the organic electrolyte the energy density reached 62.8 Wh kg(-1) and the power density reached 58.5 kW kg(-1). The addition of single-walled carbon nanotubes raised the energy density by 23% and power density by 31% more than the graphene electrodes. The graphene/CNT electrodes exhibited an ultra-high energy density of 155.6 Wh kg(-1) in ionic liquid at room temperature. In addition, the specific capacitance increased by 29% after 1000 cycles in ionic liquid, indicating their excellent cyclicity. The SWCNTs acted as a conductive additive, spacer, and binder in the graphene/CNT supercapacitors. This work suggests that our graphene/CNT supercapacitors can be comparable to NiMH batteries in performance and are promising for applications in hybrid vehicles and electric vehicles. 相似文献
980.
A nanostructured skeleton catalyst: Suzuki-coupling with a reusable and sustainable nanoporous metallic glass Pd-catalyst 总被引:1,自引:0,他引:1
Tanaka S Kaneko T Asao N Yamamoto Y Chen M Zhang W Inoue A 《Chemical communications (Cambridge, England)》2011,47(21):5985-5987
Nanoporous metallic glass Pd, which was fabricated by dealloying of a glassy metallic alloy Pd(30)Ni(50)P(20), exhibited a remarkable catalytic activity for the Suzuki-coupling reaction between iodoarenes and arylboronic acids under mild conditions. Moreover, the catalyst can be reused several times without a significant loss of catalytic activity. 相似文献