全文获取类型
收费全文 | 331篇 |
免费 | 8篇 |
专业分类
化学 | 173篇 |
晶体学 | 7篇 |
力学 | 6篇 |
数学 | 58篇 |
物理学 | 95篇 |
出版年
2023年 | 2篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 9篇 |
2017年 | 14篇 |
2016年 | 13篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 37篇 |
2012年 | 23篇 |
2011年 | 23篇 |
2010年 | 21篇 |
2009年 | 14篇 |
2008年 | 46篇 |
2007年 | 33篇 |
2006年 | 22篇 |
2005年 | 12篇 |
2004年 | 7篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1974年 | 1篇 |
1932年 | 1篇 |
排序方式: 共有339条查询结果,搜索用时 93 毫秒
91.
Ayşe Berkman Alexandre V. Borovik Jeffrey Burdges Gregory Cherlin 《Journal of Algebra》2008,319(1):50-76
This paper provides a method for identifying “sufficiently rich” simple groups of finite Morley rank with simple algebraic groups over algebraically closed fields. Special attention is given to the even type case, and the paper contains a number of structural results about simple groups of finite Morley rank and even type. 相似文献
92.
An elastomeric grating coupler fabricated by the replica molding technique is used to measure the modal indices of a silicon-on-insulator (SOI) planar waveguide structure. Because of the van der Waals interaction between the grating mold and the waveguide, the elastomeric stamp makes conformal contact with the waveguide surface, inducing a periodic index perturbation at the contact region. The phase of the incident light is changed to match the guided modes of the waveguide. The modal and bulk indices are obtained by measuring the coupling angles. This technique serves to measure the high refractive index with a precision better than 10(-3) and allows the elastomeric stamp to be removed without damaging the surface of the waveguide. 相似文献
93.
Copolymers and terpolymers of N-t-butylacrylamide (TBA) with 2-acrylamido-2-methyl propane sulfonic acid (AMPS) and N-hydroxy methyl acrylamide (NHMAAM) were prepared by solution polymerization in a 1:1 (v/v) mixture of methanol and water at 50 °C keeping the TBA content in the feed constant at 60% based on mole ratio. The contents of AMPS or NHMAAM used for the preparation of TBA-AMPS and TBA-NHMAAM copolymers were 40 mole %. Molar percentages of AMPS and NHMAAM monomers in the feed for the preparation of TBA-AMPS-NHMAAM terpolymers were varied as 10:30, 20:20, and 30:10, respectively. The effects of temperature, AMPS and crosslinker contents, and the drying of swollen gels on the swelling behavior of ionic and non-ionic TBA gels were investigated in distilled water between 10–50 °C and in buffer solutions having various pHs (1.9, 3.1, 5.6, 7.1, and 9.8) with constant ionic strength of 0.08 M at 20 °C using both the dry and the swollen forms of gels. The chemical structures and microscopic morphologies of the polymers were investigated by FTIR and SEM, respectively. 相似文献
94.
A similarity analysis was performed to investigate the laminar boundary-layer flow in the presence of a transverse magnetic
field over a down-pointing and spinning cone with mixed thermal boundary conditions. Boundary layer velocity and temperature
profiles were determined numerically for various values of the magnetic and spin parameters and the Prandtl number. The spin
of the cone compresses the velocity profiles towards the surface by inducing an upward flow and decreases the surface temperature.
The magnetic field suppresses the velocity profiles and increases the surface temperature. A transformation relating the similarity
solutions of the boundary-layer velocity and temperature profiles associated with different values of the mixed thermal boundary
condition parameter was obtained. 相似文献
95.
Ayşegül Doğan Mehmet Emir Yalvaç Aysu Yılmaz Albert Rizvanov Fikrettin Şahin 《Applied biochemistry and biotechnology》2013,171(7):1819-1831
The use of stem-cell-based therapies in regenerative medicine and in the treatment of disorders such as Parkinson, Alzheimer's disease, diabetes, spinal cord injuries, and cancer has been shown to be promising. Among all stem cells, mesenchymal stem cells (MSCs) were reported to have anti-apoptotic, immunomodulatory, and angiogenic effects which are attributed to the restorative capacity of these cells. Human tooth germ stem cells (HTGSCs) having mesenchymal stem cell characteristics have been proven to exert high proliferation and differentiation capacity. Unlike bone-marrow-derived MSCs, HTGSCs can be easily isolated, expanded, and cryopreserved, which makes them an alternative stem cell source. Regardless of their sources, the stem cells are exposed to physical and chemical stresses during cryopreservation, hindering their therapeutic capacity. Amelioration of the side effects of cryopreservation on MSCs seems to be a priority in order to maximize the therapeutic efficacy of these cells. In this study, we tested the effect of Pluronic 188 (F68) on HTGSCs during long-term cryopreservation and repeated freezing and defrosting cycles. Our data revealed that F68 has a protective role on survival and differentiation of HTGSCs in long-term cryopreservation. 相似文献
96.
Tayfun Hüyük Antonio Di Nitto Grzegorz Jaworski Andrés Gadea José Javier Valiente-Dobón Johan Nyberg Marcin Palacz Pär-Anders Söderström Ramon Jose Aliaga-Varea Giacomo de Angelis Ayşe Ataç Javier Collado Cesar Domingo-Pardo Francisco Javier Egea Nizamettin Erduran Sefa Ertürk Gilles de France Rafael Gadea Vicente González Vicente Herrero-Bosch Ayşe Kaşkaş Victor Modamio Marek Moszynski Enrique Sanchis Andrea Triossi Robert Wadsworth 《The European Physical Journal A - Hadrons and Nuclei》2016,52(3):55
97.
98.
Emrah Özcan Dr. Burcu Dedeoglu Prof. Dr. Yuri Chumakov Prof. Dr. Ayşe Gül Gürek Prof. Dr. Yunus Zorlu Prof. Dr. Bünyemin Çoşut Dr. Mehmet Menaf Ayhan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(5):1603-1608
The ability to tune the optical features of BODIPY materials in the solid state is essential for their photorelated application and requires efficient control of the crystal packing. In this study, such control of BODIPY supramolecular assemblies was achieved by deliberate design and synthesis of a BODIPY containing a strong halogen-bond (XB) acceptor (−NO2) and donor (I, Br) to mediate XB interactions. The di-halogenated structures formed isostructural mono-coordinate motif B3 , B4 (1D tubular structure) and symmetric bifurcated motif B4-II (1D zigzag chains structure) through N−O⋅⋅⋅I, Br XB interactions. These XB interactions promote singlet-to-triplet intersystem crossing and triplet-to-singlet reverse intersystem crossing due to partial delocalization of oxygen electrons onto Br and I, which leads to unexpected fluorescence enhancement of B4-II . Finally, the indirect optical band gaps of B3 , B4 and B4-II were amenable to tuning in the range of 1.85–2.50 eV by XB-driven crystal packings. 相似文献
99.
Two kinds of reduced graphene oxide (rGO) were synthesized with the reducing agents of either dimethylformamide (DMF) or hydrazine hydrate (HYD). The decoration of platinum nanoparticles (Pt NPs) over these materials was provided by microwave irradiation (MWI) method. Detailed physical and electrochemical measurements were carried out. Based on the electrochemical results of both catalysts, it is not surprising the achievement of higher electrochemical active surface area (ECSA), higher oxygen reduction reaction (ORR) activity, higher electron transfer number, lower charge transfer resistance and higher fuel cell performance with the Pt/rGO (DMF) catalyst which surpasses Pt/rGO (HYD) in many ways. 相似文献
100.
Aysel Kantürk Figen Ay?e ?ztürk Sabriye Pi?kin 《Research on Chemical Intermediates》2012,38(9):2343-2354
The presence of caustic soda in the spent sodium borohydride (NaBH4) fuel in high concentrations creates environmental problems associated with the transportation and the disposal of the fuel, orits recycling into NaBH4. It is clear that the high level of caustic soda in the spent fuel requires efficient and proper formulation of its industrial recycling applications. The present study regards the conversion process of the caustic soda present in high concentrations in spent NaBH4 fuels. Properties of the caustic used in NaBH4 fuel is characterized using a comprehensive technique. A specific application is presented here, which includes the treatment of the spent fuel solution with anhydrous borax (Na2B4O7) at 90?°C for 3?h followed by calcination after the crystallization, resulting in the conversion of this highly caustic spent NaBH4 fuel into sodium metaborate (NaBO2), which is an environmentally friendlier and an economically valuable material. 相似文献