全文获取类型
收费全文 | 2563篇 |
免费 | 51篇 |
国内免费 | 6篇 |
专业分类
化学 | 1822篇 |
晶体学 | 38篇 |
力学 | 27篇 |
数学 | 167篇 |
物理学 | 566篇 |
出版年
2021年 | 20篇 |
2020年 | 17篇 |
2019年 | 32篇 |
2018年 | 32篇 |
2017年 | 28篇 |
2016年 | 41篇 |
2015年 | 39篇 |
2014年 | 38篇 |
2013年 | 137篇 |
2012年 | 106篇 |
2011年 | 130篇 |
2010年 | 89篇 |
2009年 | 75篇 |
2008年 | 138篇 |
2007年 | 136篇 |
2006年 | 140篇 |
2005年 | 155篇 |
2004年 | 146篇 |
2003年 | 90篇 |
2002年 | 91篇 |
2001年 | 70篇 |
2000年 | 47篇 |
1999年 | 39篇 |
1998年 | 26篇 |
1997年 | 32篇 |
1996年 | 49篇 |
1995年 | 32篇 |
1994年 | 22篇 |
1993年 | 24篇 |
1992年 | 31篇 |
1991年 | 34篇 |
1990年 | 26篇 |
1989年 | 21篇 |
1988年 | 27篇 |
1987年 | 25篇 |
1986年 | 24篇 |
1985年 | 39篇 |
1984年 | 49篇 |
1983年 | 39篇 |
1982年 | 24篇 |
1981年 | 28篇 |
1980年 | 20篇 |
1979年 | 31篇 |
1978年 | 20篇 |
1977年 | 25篇 |
1976年 | 22篇 |
1975年 | 23篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1967年 | 11篇 |
排序方式: 共有2620条查询结果,搜索用时 62 毫秒
61.
62.
63.
64.
M. Kito S. Kimura N. Otsuka K. Fujihara M. Ishino Y. Matsui 《Optical and Quantum Electronics》1996,28(5):503-511
We have investigated the temperature dependencies of the slope efficiency and the threshold current for strained multiquantum well (MQW) lasers as a parameter of the well number. Smaller well numbers mean larger temperature dependencies of the slope efficiency and the threshold current, while larger well numbers mean larger internal loss and broadening of the photoluminescence linewidth of the MQW structure. Furthermore, the change in the slope efficiency with temperature change is related to the change in internal loss. In this work, the 1.3-m strained MQW laser with a compressive strain of 1.0% and 7 wells shows the highest output power of 6.8 mW for an injection current of 50 mA and the lowest threshold current of 5.5 mA at 85°C, and the lowest variation in output power of 2.0 dB from 25–85°C at injection current of 50 mA. 相似文献
65.
F. Hirayama M. Usami K. Kimura K. Uekama 《Journal of inclusion phenomena and macrocyclic chemistry》1996,25(1-3):165-168
Chloramphenicol palmitate (CPP) was converted to an amorphous complex when spray-dried with 2-hydroxypropyl--cyclodextrin (HP--CyD), and no crystallization of CPP was observed for at least 2 months under the storage condition of 50°C and 50% relative humidity. The dissolution rate of CPP/HP--CyD complex in aqueous HCO-60 solution was much faster than CPP polymorphs (complex > metastable forms (B and subB) > stable form (A)), which was reflected in thein-vivo absorption behavior of CPP following oral administration in dogs. 相似文献
66.
67.
The dissolution behavior of ibuprofen from a kneaded mixture with low-molecular gelatin (LM gelatin) has been studied in comparison to kneaded mixtures prepared with other additives. Their in vivo absorption behaviors were also examined. The LM gelatin markedly enhanced the dissolution rate of ibuprofen compared to that with polyethylene glycol (PEG) 6000, dextran T10 or pullulan. Oral administrations of the kneaded mixture to beagle dogs showed the LM gelatin to be most effective in accelerating the absorption rate of ibuprofen among the additives used. 相似文献
68.
The delta form of crystalline syndiotactic polystyrene is a clathrate molecular compound in which various aromatic molecules are encaged. We have investigated the size, shape, and connectivity of the molecular cavity in the crystal using a molecular dynamics simulation. The effects of the guest species on the cavity structure were investigated in detail. In order to systematically vary the guest structure, various aromatic guests, e.g., benzene, toluene, p-xylene, m-xylene, o and mesitylene were examined. The interstitial spaces between the guests and the polymer chains were analyzed by cluster analysis of the free volumes. The individual cavity volumes into which the guests are clathrated were also evaluated. It was found that the guest molecules can greatly affect not only the cavity size and shape but also the connectivity of the cavities. The transport of small molecules in the crystal is discussed in connection with the cavity structure. 相似文献
69.
Three-dimensional particle crystals made of dicarboxylic thiolate (MSA)-stabilized gold nanoparticles were formed at an air/water interface. FTIR spectra of this supracrystal showed that three well-resolved peaks existed from 3400 to 3550 cm-1 just falling in a region of OH stretching vibrational mode. Precise analysis showed that all these peaks originated from the water cluster included in the interstice of a particle crystal. 相似文献
70.