全文获取类型
收费全文 | 8339篇 |
免费 | 247篇 |
国内免费 | 42篇 |
专业分类
化学 | 5833篇 |
晶体学 | 40篇 |
力学 | 209篇 |
数学 | 1107篇 |
物理学 | 1439篇 |
出版年
2023年 | 46篇 |
2022年 | 56篇 |
2021年 | 66篇 |
2020年 | 93篇 |
2019年 | 99篇 |
2018年 | 72篇 |
2017年 | 61篇 |
2016年 | 184篇 |
2015年 | 152篇 |
2014年 | 174篇 |
2013年 | 370篇 |
2012年 | 460篇 |
2011年 | 532篇 |
2010年 | 284篇 |
2009年 | 233篇 |
2008年 | 516篇 |
2007年 | 546篇 |
2006年 | 548篇 |
2005年 | 474篇 |
2004年 | 427篇 |
2003年 | 367篇 |
2002年 | 346篇 |
2001年 | 149篇 |
2000年 | 106篇 |
1999年 | 66篇 |
1998年 | 82篇 |
1997年 | 100篇 |
1996年 | 133篇 |
1995年 | 126篇 |
1994年 | 105篇 |
1993年 | 145篇 |
1992年 | 96篇 |
1991年 | 78篇 |
1990年 | 96篇 |
1989年 | 74篇 |
1988年 | 64篇 |
1987年 | 65篇 |
1986年 | 52篇 |
1985年 | 90篇 |
1984年 | 81篇 |
1983年 | 57篇 |
1982年 | 87篇 |
1981年 | 90篇 |
1980年 | 69篇 |
1979年 | 70篇 |
1978年 | 68篇 |
1977年 | 50篇 |
1976年 | 69篇 |
1975年 | 47篇 |
1973年 | 36篇 |
排序方式: 共有8628条查询结果,搜索用时 0 毫秒
891.
Fortman GC Jacobsen H Cavallo L Nolan SP 《Chemical communications (Cambridge, England)》2011,47(34):9723-9725
The catalytic activity of a series of coordinatively unsaturated NHC-M(III) (M = Rh, Ir; NHC = N-heterocyclic carbene) complexes was tested in the deuteration of secondary and tertiary silanes. Among these, [IrCl(I(t)Bu')(2)] provides the highest conversions to the deuterated species. Mechanistic studies highlight the reversible nature of the ortho-metalation reaction. 相似文献
892.
Lambert TN Davis DJ Limmer SJ Hibbs MR Lavin JM 《Chemical communications (Cambridge, England)》2011,47(34):9597-9599
Nanoscale vanadium phosphides can serve as new high capacity anodes in alkaline aqueous electrolytes. Competing corrosion reaction(s) are mitigated with the novel use of an anion exchange membrane providing for capacities as high as 2800 mAh g(-1) @ 100 mA g(-1) discharge rate. 相似文献
893.
Fu W Kiggans J Overbury SH Schwartz V Liang C 《Chemical communications (Cambridge, England)》2011,47(18):5265-5267
Microwave induced rapid decomposition of nitromethane at low temperature exfoliates the graphene sheets from the FeCl(3) and CH(3)NO(2) co-intercalated graphite compound without creating many defects and functional groups. This approach provides a scalable method for high-quality graphene materials via low-temperature exfoliation of graphite under mild chemical conditions. 相似文献
894.
DNA sequences attached to Au nanoparticles via thiol linkers stand up from the surface, giving preferential enhancement of the adenine ring breathing SERS band. Non-specific binding via the nucleobases reorients the DNA, reducing this effect. This change in intensity on reorientation was utilised for label-free detection of hybridization of a molecular beacon. 相似文献
895.
Mulholland AR Woodward CP Langford SJ 《Chemical communications (Cambridge, England)》2011,47(5):1494-1496
An olefination approach to the construction of covalently linked cyclic metalloporphyrin trimers is presented using fullerenes such as C(60) or C(70) as a template. Yields of the trimer approach 60%. In the absence of a template, the major product is the cyclic dimer (50% yield) with only a small amount of trimer (<10%) formed, indicating this is a template-directed approach. 相似文献
896.
897.
898.
899.
900.
Pas SJ Dargusch MS MacFarlane DR 《Physical chemistry chemical physics : PCCP》2011,13(25):12033-12040
The properties of ionic liquids give rise to applications in diverse technology areas including mechanical engineering, mining, aerospace and defence. The arbitrary physical property that defines an ionic liquid is a melting point below 100 °C, and as such, an understanding of crystallisation phenomena is extremely important. This is the first report dealing with the mechanism of crystallisation in ionic liquids. Assuming crystallisation of the ionic liquids is a thermal or mass diffusion-controlled process, the values of the isothermal Avrami exponent obtained from three different ionic liquids with three different anions and cations all indicate that growth occurs with a decreasing nucleation rate (n=1.8-2.2). For one of the ionic liquids it was possible to avoid crystallisation by fast cooling and then observe a devitrification upon heating through the glass transition. The isothermal Avrami exponent of devitrification suggested growth with an increasing nucleating rate (n=4.1), compared to a decreasing nucleation rate when crystallisation occurs on cooling from the melt (n=2.0). Two non-isothermal methods were employed to determine the Avrami exponent of devitrification. Both non-isothermal Avrami exponents were in agreement with the isothermal case (n=4.0-4.15). The applicability of JMAK theory suggests that the nucleation event in the ionic liquids selected is a random stochastic process in the volume of the material. Agreement between the isothermal and non-isothermal techniques for determining the Avrami exponent of devitrification suggests that the pre-exponential factor and the activation energy are independent of thermal history. The heating rate dependence of the glass transition enabled the calculation of the fragility index, which suggests that the ionic liquid is a "strong" glass former. This suggests that the temperature dependence of the rate constant could be close to Arrhenius, as assumed by JMAK theory. More generally, therefore, it can be concluded that there is nothing unusual about the crystallisation mechanism of the ionic liquids studied here. 相似文献