全文获取类型
收费全文 | 5564篇 |
免费 | 859篇 |
国内免费 | 710篇 |
专业分类
化学 | 4516篇 |
晶体学 | 119篇 |
力学 | 277篇 |
综合类 | 32篇 |
数学 | 581篇 |
物理学 | 1608篇 |
出版年
2024年 | 10篇 |
2023年 | 143篇 |
2022年 | 202篇 |
2021年 | 256篇 |
2020年 | 293篇 |
2019年 | 274篇 |
2018年 | 237篇 |
2017年 | 196篇 |
2016年 | 275篇 |
2015年 | 301篇 |
2014年 | 376篇 |
2013年 | 423篇 |
2012年 | 516篇 |
2011年 | 497篇 |
2010年 | 291篇 |
2009年 | 283篇 |
2008年 | 305篇 |
2007年 | 273篇 |
2006年 | 268篇 |
2005年 | 216篇 |
2004年 | 172篇 |
2003年 | 167篇 |
2002年 | 185篇 |
2001年 | 139篇 |
2000年 | 115篇 |
1999年 | 136篇 |
1998年 | 80篇 |
1997年 | 63篇 |
1996年 | 94篇 |
1995年 | 71篇 |
1994年 | 35篇 |
1993年 | 42篇 |
1992年 | 29篇 |
1991年 | 33篇 |
1990年 | 33篇 |
1989年 | 21篇 |
1988年 | 17篇 |
1987年 | 18篇 |
1986年 | 14篇 |
1985年 | 13篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1970年 | 1篇 |
1963年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有7133条查询结果,搜索用时 15 毫秒
31.
32.
33.
The optical nonlinearities of Cu(mpo)2 [formula = C10H8N2CuO2S2] complex have firstly been investigated by using the Z-scan technique with a nanosecond-pulsed Nd:YAG laser at its second harmonic (532 nm) radiation. The nonlinear optical absorption and refraction coefficients of Cu(mpo)2 have been measured with the different on-axial peak irradiances I
0 at the waist ranging from 0.48 to 5.66 GW/cm2. The nonlinear transmittance characteristics exhibit the near resonant two-photon absorption (TPA) at 532 nm and are explained by a population redistribution model. The nonlinear absorption originates from the near resonant TPA while the mechanism of the nonlinear refraction is the near resonant TPA transition enhancement. The linear increasing dependences of the optical nonlinearities on the incident irradiance arise from the population redistribution due to the near resonant TPA. 相似文献
34.
用光谱技术研究了水溶液中氧氟沙星(OFLX)和左氟沙星(LVFX)与人血清白蛋白相互作用的机制.荧光猝灭法测得的结果表明反应的结合常数为KOFLX=0.482×105L@mol-1,KLVFX=0.529×105L@mol-1,结合位点数nOFLX=0.72,nLVFX=0.74.按照Fōorster非辐射能量转移理论得到药物-蛋白之间的结合距离分别为rOFLX=2.94nm,nVFX=2.85 nm.实验结果说明OFLX与LVFX在体内与蛋白结合直到运输到受体部位这一环节基本相同. 相似文献
35.
Ha Yong Lee Se Hun Jung Soo Yong Lee Young Ho You Kyung Hyun Ko 《Applied Surface Science》2005,252(5):1891-1898
Al-Al2O3 composite coatings with different Al2O3 particle shapes were prepared on Si and Al substrate by cold spray. The powder compositions of metal (Al) and ceramic (Al2O3) having different sizes and agglomerations were varied into ratios of 10:1 wt% and 1:1 wt%. Al2O3 particles were successfully incorporated into the soft metal matrix of Al. It was found that crater formation between the coatings and substrate, which is typical characteristic signature of cold spray could be affected by initial starting Al2O3 particles. In addition, when the large hard particles of fused Al2O3 were employed, the deep and big craters were generated at the interface between coatings and hard substrates. In the case of pure soft metal coating such as Al on hard substrate, it is very hard to get proper adhesion due to lack of crater formation. Therefore, the composite coating would have certain advantages. 相似文献
36.
A novel and cost-effective sol-gel process for preparation of MgAl2O4 spinel nanometer powders has been developed in this study. A solution of magnesium and aluminum nitrates in stoichiometric proportion was successfully embraced in the biology polysaccharide gel network, formed by the synergistic interaction between xanthan gum (XG) and locust bean gum (LBG) utilizing their broad-spectrum stability of salt tolerance and character of transformation from sol to gel on the condition of proper temperature and relative proportion of polymeric components. Dry gel could be obtained by vacuum dehydration of aqueous gel at low temperatures. Monolithic MgAl2O4 spinel nanometer powders were produced by calcining the dry gel above 800°C, with average crystallite size of 20 nanometers. 相似文献
37.
QiaoHongYAO FuYouLI LuSHAN ChunHuiHUANG DongDongYIN 《中国化学快报》2003,14(11):1185-1188
A new photoresponsive D-π-A dye, mPS, has been designed and synthesized.Compared to the parent dye PS, IPCE values in the region from 400 nm to 560 nm was greatly improved upon changing the attaching group from the p- position to the o- position of the π-conjugation bridge. A solar cell based on mPS generated a remarkably high overall yield η of 5.4% under irradiation of 80.0 mW cm^-2 white light from a Xe lamp, Compared with PS, the overall yield η increased by 64%. 相似文献
38.
X. Y. You 《Heat and Mass Transfer》2003,40(1-2):75-81
Active feedback control for the onset of Rayleigh-Bénard Convection in temperature-dependent-viscosity liquids is investigated.
In this paper, three major problems are addressed: (1) The results of Tang-Bau control are improved by considering the effects
of temperature-dependent viscosity; (2) A more efficient two-plate control strategy is presented. A phenomenon of coalescence
of the unstable modes is observed as the controller gain is large enough; (3) A simple way to estimate the critical Rayleigh
number under the effects of temperature-dependent viscosity is described. Numerical results show that the effects of temperature-dependent
viscosity on the critical Rayleigh number should be taken into account in some cases and the onset of Rayleigh-Bénard convection
can be effectively delayed or advanced by the active feedback control strategies studied here. 相似文献
39.
脉冲染料激光器的可见光波段辐射通过共线倍频和非共线混频实现紫外波段的连续可调谐输出.本文报道了一种闭环跟踪方法;在调谐起始波长处,将取样光束在垂直相位匹配方向分割成等光强的两部分,然后在波长调谐时比较和平衡这两部分光强.对该方法在理论上作了分析并在实验中得到成功的验证.获得的自动跟踪效率大于90%. 相似文献
40.
Guan Wu WANG* Li Juan JIAO Er Hong HAO Yong Ming LU You Jun YANG Department of Chemistry University of Science Technology of China Hefei 《中国化学快报》2004,15(5)
Water-soluble fullerenes not only have a number of important applications in biological chemistry1, but also form ordered aggregate structures that can be utilized in materials science2. There are reports that some water-soluble fullerene derivatives can form ordered structures in water, such as vesicle, nanorod and nanoparticle2-5. However, relatively few reports on the aggregation process have been reported. Knowledge of factors that affect the cluster formation in solution is of consider… 相似文献