首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7010篇
  免费   1328篇
  国内免费   694篇
化学   4995篇
晶体学   41篇
力学   428篇
综合类   44篇
数学   916篇
物理学   2608篇
  2024年   15篇
  2023年   137篇
  2022年   168篇
  2021年   245篇
  2020年   343篇
  2019年   251篇
  2018年   230篇
  2017年   218篇
  2016年   332篇
  2015年   357篇
  2014年   382篇
  2013年   490篇
  2012年   644篇
  2011年   704篇
  2010年   454篇
  2009年   410篇
  2008年   454篇
  2007年   423篇
  2006年   404篇
  2005年   288篇
  2004年   256篇
  2003年   162篇
  2002年   190篇
  2001年   120篇
  2000年   135篇
  1999年   149篇
  1998年   128篇
  1997年   145篇
  1996年   130篇
  1995年   119篇
  1994年   100篇
  1993年   99篇
  1992年   71篇
  1991年   60篇
  1990年   57篇
  1989年   35篇
  1988年   32篇
  1987年   31篇
  1986年   11篇
  1985年   24篇
  1984年   10篇
  1983年   6篇
  1982年   4篇
  1981年   6篇
  1980年   1篇
  1979年   1篇
  1916年   1篇
排序方式: 共有9032条查询结果,搜索用时 781 毫秒
901.
Superparamagnetic Fe(3)O(4) nanoparticles with positive surface ξ-potential were synthesized via a solvothermal route. After Fe(3)O(4) was mixed with HAuCl(4) and NaBH(4), the reduced Au nanoparticles could be directly adsorbed onto the surface of Fe(3)O(4) nanoparticles. The as-synthesized nanocomposites were successfully applied to photothermal destruction of cancer cells.  相似文献   
902.
ZnFe(2)O(4)/C hollow spheres have been synthesized via a facile solvothermal route using low cost raw materials. The resulting composite showed a very high specific capacity of 841 mAh g(-1) after 30 cycles and good rate capability.  相似文献   
903.
Titanate nanosheets and nanotubes have first been introduced into cigarette filter, a great range of harmful compounds including tar, nicotine, ammonia, hydrogen cyanide, selected carbonyls and phenolic compounds can be reduced efficiently.  相似文献   
904.
Multi-wall carbon nanotubes and polyaniline composites were synthesized via a simple hydrothermal reaction, and the as-made composites were successfully applied in the analysis of small molecular-weight metabolites as a novel matrix by matrix assisted laser desorption/ionization mass spectrometry.  相似文献   
905.
The title compound, 1′,3′-dihydrospiro[fluorene-9,2′-perimidine] has been synthesized and characterized by NMR, ESI-MS, IR, elemental analysis, UV–vis and fluorescence spectroscopy. The crystal structures of the title compound and its co-crsytal with 9-fluorenone have also been determined by X-ray single crystal diffraction. Density functional theory (DFT) calculations and vibrational frequencies have been performed at B3LYP/6-31G* level. The comparisons between the experimental vibrational frequencies and the predicted data show that B3LYP/6-31G* method can simulate the IR of the title compound on the whole. The theoretical electronic absorption spectra have been calculated by using TD-DFT method and compared with the experimental result. The solid-fluorescence determination of the title compound reveals two emission bans at 430 and 590 nm while its co-crystal reveals only one emission band at 590 nm.  相似文献   
906.
Twelve novel acenaphthene derivatives have been synthesized. The structures of all compounds were confirmed by 1H-NMR, MS and elemental analysis. Their antitumor activities were evaluated in six human solid tumor cell lines, namely non-small cell lung cancer (H460), human colon adenocarcinoma (SW480), human breast cancer cell (MDA-MB-468 and SKRB-3), human melanoma cell (A375) and human pancreatic cancer (BxPC-3). Among them, compound 3c shows the best antitumor activity against SKRB-3 cell line, as high as the positive control adriamycin.  相似文献   
907.
Immunosuppressive activity of 8-gingerol on immune responses in mice   总被引:2,自引:0,他引:2  
8-gingerol is one of the principal components of ginger, which is widely used in China and elsewhere as a food, spice and herb. It shows immunosuppressive activity on the immune responses to ovalbumin (OVA) in mice. In the present study, we found that 8-gingerol suppressed lipopolysaccharide (LPS) and concanavalin A (ConA)-stimulated splenocyte proliferation in vitro. In vivo, 8-gingerol not only signi?cantly suppressed Con A-, LPS- and OVA-induced splenocyte proliferation (P < 0.05) but also decreased the percentage of CD19+ B cells and CD3+ T cell (P < 0.05) at high doses (50, 100 mg/kg). Moreover, OVA-speci?c IgG, IgG1 and IgG2b levels in OVA-immunized mice were reduced by 8-gingerol at doses of 50, 100 mg/kg. These results suggest that 8-gingerol could suppress humoral and cellular immune responses in mice. The mechanism might be related to direct inhibition of sensitized T and B lymphocytes.  相似文献   
908.
909.
910.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号