全文获取类型
收费全文 | 144267篇 |
免费 | 10555篇 |
国内免费 | 6960篇 |
专业分类
化学 | 69369篇 |
晶体学 | 1408篇 |
力学 | 10994篇 |
综合类 | 515篇 |
数学 | 39616篇 |
物理学 | 39880篇 |
出版年
2024年 | 228篇 |
2023年 | 1399篇 |
2022年 | 2281篇 |
2021年 | 2353篇 |
2020年 | 2521篇 |
2019年 | 2423篇 |
2018年 | 12056篇 |
2017年 | 11671篇 |
2016年 | 8701篇 |
2015年 | 3868篇 |
2014年 | 3922篇 |
2013年 | 5133篇 |
2012年 | 9488篇 |
2011年 | 16058篇 |
2010年 | 9439篇 |
2009年 | 9754篇 |
2008年 | 10502篇 |
2007年 | 12239篇 |
2006年 | 3757篇 |
2005年 | 4337篇 |
2004年 | 3942篇 |
2003年 | 3791篇 |
2002年 | 2657篇 |
2001年 | 1752篇 |
2000年 | 1699篇 |
1999年 | 1709篇 |
1998年 | 1518篇 |
1997年 | 1309篇 |
1996年 | 1418篇 |
1995年 | 1183篇 |
1994年 | 1081篇 |
1993年 | 957篇 |
1992年 | 820篇 |
1991年 | 726篇 |
1990年 | 603篇 |
1989年 | 538篇 |
1988年 | 424篇 |
1987年 | 406篇 |
1986年 | 354篇 |
1985年 | 346篇 |
1984年 | 244篇 |
1983年 | 212篇 |
1982年 | 186篇 |
1981年 | 150篇 |
1980年 | 128篇 |
1979年 | 93篇 |
1978年 | 90篇 |
1977年 | 70篇 |
1975年 | 73篇 |
1973年 | 82篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Preparation and characterization of nitrogen-doped TiO2 photocatalyst in different acid environments
Ye Cong Ling Xiao Jinlong Zhang Feng Chen Masakazu Anpo 《Research on Chemical Intermediates》2006,32(8):717-724
Nitrogen-doped TiO2 powders were successfully prepared by a wet method, i.e., a micro-emulsion-hydrothermal method, in different acid environments.
Several characterization techniques, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse
reflectance spectra, were combined to determine the crystal phase, concentration and chemical states of the nitrogen doped
in TiO2. The high photocatalytic activity of the nitrogen-doped TiO2 was evaluated through the decomposition of rhodanmine B under visible light irradiation. It was suggested that the doped
nitrogen formed oxynitride (NO) and produced impurity states at higher above the valence band of TiO2. Therefore, the nitrogen doping could enhance the response of photocatalyst to the visible light and improve the photocatalytic
activity because of the narrowing of band gap of TiO2. 相似文献
993.
Xie M Liu HH Chen P Zhang ZL Wang XH Xie ZX Du YM Pan BQ Pang DW 《Chemical communications (Cambridge, England)》2005,(44):5518-5520
A simple and convenient method for the construction of CdSe/ZnS-labeled polysaccharides as bioprobes were developed, which are highly biocompatible and photostable, and have been proven to be suitable for live cell imaging. 相似文献
994.
995.
996.
997.
The new misfit layer compound (LaSe)1.14(NbSe2)2 has been synthesized from the elements at 1050- and its structure has been determined by a composite approach. The structure has an alternating stacking sequence of [LaSe] and two [NbSe2] layers along the c direction. The misfit of the two different layers is occurring along the a direction: a1(LaSe)=6.0191 Å and a2(NbSe2)=3.4372 Å therefore yielding a ratio of 1.751 which is very close to 7/4. An investigation of electrical resistivity was done. The crystal shows superconducting properties at 5.3 K. 相似文献
998.
999.
1000.
H. Sh. Bai H. X. Jin H. Q. Fan J. Du F. Wang D. M. Chen Zh. Cheng 《Journal of Radioanalytical and Nuclear Chemistry》1998,236(1-2):87-95
The behavior of153Sm-EDTMP in vitro and vivo is analyzed by the size exclusion HPLC. The experimental results show that EDTMP amounts have an
obvious effect on the stability in vitro and uptake of153Sm-EDTMP in the liver. HPLC analysis of urine sample indicates that153Sm-EDTMP es excreted in the original form. The behavior in vivo of153Sm-EDTMP containing 4 μg is similar to that of153Sm-EDTMP containing 50 μg EDTMP at 1 h post-injection. 相似文献