全文获取类型
收费全文 | 10277篇 |
免费 | 1823篇 |
国内免费 | 1541篇 |
专业分类
化学 | 7973篇 |
晶体学 | 141篇 |
力学 | 636篇 |
综合类 | 94篇 |
数学 | 1329篇 |
物理学 | 3468篇 |
出版年
2024年 | 24篇 |
2023年 | 165篇 |
2022年 | 311篇 |
2021年 | 356篇 |
2020年 | 375篇 |
2019年 | 442篇 |
2018年 | 359篇 |
2017年 | 313篇 |
2016年 | 529篇 |
2015年 | 606篇 |
2014年 | 625篇 |
2013年 | 776篇 |
2012年 | 900篇 |
2011年 | 894篇 |
2010年 | 718篇 |
2009年 | 680篇 |
2008年 | 714篇 |
2007年 | 581篇 |
2006年 | 518篇 |
2005年 | 486篇 |
2004年 | 440篇 |
2003年 | 401篇 |
2002年 | 510篇 |
2001年 | 423篇 |
2000年 | 265篇 |
1999年 | 221篇 |
1998年 | 188篇 |
1997年 | 132篇 |
1996年 | 118篇 |
1995年 | 107篇 |
1994年 | 84篇 |
1993年 | 67篇 |
1992年 | 55篇 |
1991年 | 58篇 |
1990年 | 36篇 |
1989年 | 27篇 |
1988年 | 21篇 |
1987年 | 16篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 14篇 |
1983年 | 11篇 |
1982年 | 4篇 |
1981年 | 13篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1974年 | 5篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
51.
Wang Xiangru Xiong Caidong Wen Xia Qiu Qi Luo Juanyan Deng Hao Xie Wen 《Optics Communications》2010,283(1):44-48
With the purpose of uniform gain coefficient along the axial direction in the core of gain guided and index anti-guided fiber, a new kind of side-pump scheme by wrapping particularly treated fibers around the central GGIAG fiber is reported in this paper. According to leakage mode analysis on wrapped fiber and numerical simulation on this pumping structure having ytterbium doped central fiber and conventional wrapped side fiber, we find this kind of pump scheme can improve the uniformity of gain coefficient along the fiber direction, and also, it can support multi channels of pumping sources by adding more side fibers to improve the total effective incident pumping power. 相似文献
52.
本文利用浇铸法,使用M&N胶和OE6450两种聚硅氧烷制备光波导.通过改进制备光波导的多个关键技术, 解决了波导制备过程中的气泡问题、脱模问题、芯层不固化问题、芯层和覆盖层产生化学反应等难题,提出了 比较完备和科学的聚硅氧烷波导制备工艺流程,从而使得波导的制备成品率从原来低于40%提高到高于80%, 波导的最大长度从原来的21 cm增加到22.5 cm,波导的损耗(截断法测量结果)从最初的0.3dB/cm(850 nm)降低到了 0.21dB/cm(850nm).本文在波导制备技术方面具有重要的实际意义和价值. 相似文献
53.
Critical entanglement and geometric phase of a two-qubitmodel with Dzyaloshinski--Moriya anisotropic interaction 下载免费PDF全文
We consider a two-qubit system described by the Heisenberg
XY model with Dzyaloshinski--Moriya (DM) anisotropic interaction
in a perpendicular magnetic field to investigate the relation
between entanglement, geometric phase and quantum phase transition
(QPT). It is shown that the DM interaction has an effect on the
critical boundary. The combination of entanglement and geometric
phase may characterize QPT completely. Their jumps mean that the occurrence
of QPT and inversely the QPT at the critical point at least
corresponds to a jump of one of them. 相似文献
54.
Effect of temperature on the polaron stability in a one-dimensional organic lattice is investigated within the Su-Schrieffer-Heeger model. The temperature effect is simulated by introducing random forces to the equation of the lattice motion. It is found that the localized polaron state becomes delocalized even at low temperatures. The time of polaron keeping localized depends on the magnitude of temperatures. By taking into account the thermal effect, we find that the dissociation field is weaker as compared with earlier works. 相似文献
55.
A flashing ratchet model of a two-headed molecular motor in a two-dimensional potential is proposed to simulate the hand-over-hand motion of kinesins.Extensive Langevin simulations of the model are performed.We discuss the dependences of motion and efficiency on the model parameters,including the external force and the temperature.A good qualitative agreement with the expected behavior is observed. 相似文献
56.
57.
Carbon black (CB) was modified by liquid grafting and used for natural rubber (NR) reinforcement. Payne effects during NR reinforcement by the graft-modified carbon black (GCB) were analyzed in this paper. The results showed a proportional relationship between filler content and the Payne effect. Rubber compounds with GCB presented weaker Payne effects than their non-modified counterparts. Qualitative analysis of the correlation between filler network structure and filler content was conducted according to the relationship between bound rubber of a rubber compound and shear modulus. The impact of the storage period on the Payne effect was further studied, and the results demonstrated that the longer the storage period of the rubber compound, the stronger the Payne effect tended to be. The mechanisms by which the Payne effects were manifested differed according to the content of the filler in the rubber. 相似文献
58.
H. M. Noor ul Huda Khan Asghar Yi Tan Shuang Shi Dachuan Jiang Shiqiang Qin Jiao Liao Shutao Wen Wei Dong Yao Liu 《Applied Physics A: Materials Science & Processing》2014,115(3):753-757
Small amounts of multicrystalline silicon were melted in an electron beam furnace in different experimental conditions in order to investigate the oxygen evaporation behavior during the electron beam melting (EBM) process. The oxygen content level before and after EBM was determined by secondary ion mass spectroscopy. The oxygen content was reduced from 6.177 to 1.629 ppmw when silicon was melted completely at 15 kW with removal efficiency up to 73.6 %. After that, it decreased continually to <0.0517 ppmw when the refining time exceeded 600 s with a removal efficiency of more than 99.08 %. During the melting process, the evaporation rate of silicon is 1.10 × 10?5 kg/s. The loss of silicon could be reduced up to 1.7 % during oxygen removal process to a desirable figure, indicating EBM is an effective method to remove oxygen from silicon and decrease the loss of silicon. 相似文献
59.
Li Huang Qin Guo Xue-xiang Xu Wen Yuan 《International Journal of Theoretical Physics》2014,53(11):3970-3980
A kind of non-Gaussian state—variable arcsine state is studied by using the input-output theories which relate the statistical properties of the output field to those of the input field. The variable arcsine state (VAS) is generated by using a variable beam splitter (BS), which means that the transmissivity (reflectivity) of the BS is adjustable continuously. The nonclassicality is investigated by studying the negativity of Wigner function (WF). It is shown that the variable arcsine state has negative values of WF when transmissivity is not equal to 1 or 0. The decoherence effect of the VAS is then studied by analytically deriving the time evolution formula of WF. 相似文献
60.
Considering the spin degree of freedom of the Dirac field, we study the entanglement behavior of a different class of communication channel and teleportation of three-dimensional single particle state in noninertial frames. Numerical analysis shows that the communication channel in our scheme can offer enough distillable entanglement for the teleportation protocol. Moreover, the teleportation protocol could work well if Rob's acceleration is not very big, but the fidelity of the teleportation is still reduced due to the Unruh effect. 相似文献