全文获取类型
收费全文 | 4371篇 |
免费 | 563篇 |
国内免费 | 500篇 |
专业分类
化学 | 3356篇 |
晶体学 | 32篇 |
力学 | 208篇 |
综合类 | 39篇 |
数学 | 399篇 |
物理学 | 1400篇 |
出版年
2024年 | 8篇 |
2023年 | 97篇 |
2022年 | 128篇 |
2021年 | 126篇 |
2020年 | 171篇 |
2019年 | 171篇 |
2018年 | 128篇 |
2017年 | 133篇 |
2016年 | 180篇 |
2015年 | 191篇 |
2014年 | 255篇 |
2013年 | 321篇 |
2012年 | 415篇 |
2011年 | 447篇 |
2010年 | 291篇 |
2009年 | 255篇 |
2008年 | 300篇 |
2007年 | 255篇 |
2006年 | 242篇 |
2005年 | 187篇 |
2004年 | 130篇 |
2003年 | 101篇 |
2002年 | 94篇 |
2001年 | 95篇 |
2000年 | 63篇 |
1999年 | 83篇 |
1998年 | 67篇 |
1997年 | 62篇 |
1996年 | 77篇 |
1995年 | 86篇 |
1994年 | 47篇 |
1993年 | 31篇 |
1992年 | 37篇 |
1991年 | 35篇 |
1990年 | 21篇 |
1989年 | 16篇 |
1988年 | 16篇 |
1987年 | 8篇 |
1986年 | 17篇 |
1985年 | 13篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1974年 | 1篇 |
1940年 | 1篇 |
1902年 | 1篇 |
1898年 | 1篇 |
排序方式: 共有5434条查询结果,搜索用时 109 毫秒
61.
Annals of Global Analysis and Geometry - In this paper, we study a problem of finding compact hypersurfaces of prescribed mean curvature with free boundary in a ball. We transform the problem to an... 相似文献
62.
63.
钾原子中多种受激辐射参与的混频过程 总被引:2,自引:1,他引:1
当双原子共振激发钾原子于6S能级时,由光泵受激辐射和电离复合受激辐射参与的六波或四波混频,产生了位于紫外和紫区的诸多相干辐射、文中对多种混频机制进行了分析和讨论,并对所测得的相干辐射线进行了标识. 相似文献
64.
钼钨铌磷杂多化合物的研究(Ⅰ):杂多酸的合成和表征 总被引:4,自引:0,他引:4
提出了分步酸化一分步加料合成[PNb_2Mo_xW_(10-x)O_(40)]~(5-)(x=0,2,4,6)系列杂多酸的方法,给出了最佳配料比和生成反应的pH值,并进行了红外、紫外、极谱、电位滴定及热稳定性研究。 相似文献
65.
Taking a typical local and industry-orientated applied chemistry major as an example with focusing on the major changes in the form and content of the petrochemical industry, the way to reform the core curriculum system and teaching contents is presented. Based on the changing tendency of refinement of the petrochemical industry, a complete curriculum system with distinctive industry characteristics is set up according to the principles of the emerging engineering education (3E) with several reasonable suggestions. A new model for the construction of a 3E major in chemistry-related majors is suggested. It is a good reference for the construction of curriculum systems for other local and industry-orientated colleges who want to make 3E reform. 相似文献
66.
67.
A novel concocting method to convert Triptolide (T) into Tripchlorolide (T(4)) in the traditional Chinese herb Tripterygium wilfordii Hook F. and a micellar electrokinetic capillary chromatographic (MEKC) approach by which the conversion of Triptolide (T) and Tripchlorolide (T(4)) was identified and determined had been established. Investigations of the influence of different pH values of boric acid and borax buffer and of sodium dodecyl sulfate (SDS) and organic additive concentrations had been carried out, and the optimum separation for T and T(4) was achieved using boric acid and borax of pH 7.0 with 30 mM SDS and 20% (volume ratio) methanol as the running buffer. It was found that MEKC exhibited good accuracy, precision and repeatability and the content of T(4) was greatly increased in the herb that was treated by the new concocting method. 相似文献
68.
In this work, the surface properties of novel sugar-containing polymers, α-allyl glucoside (AG)/acrylonitrile (AN)copolymers, were studied by contact angle, protein adsorption and cell adhesion measurements. It was found that the contactangle of the copolymer films decreased from 68° to 30° with the increase of AG content in the copolymer. The adsorptionamount of bovine serum albumin (BSA) and the adhesive macrophage onto the film surface also decreased significantly withincreasing α-allyl glucoside content from 0 to 42 wt% in the copolymer. These preliminary results reveal that both thehydrophilicity and the biocompatibility of polyacrylonitrile-based membranes could be improved by copolymerizing acrylonitrile with vinyl carbohydrates. 相似文献
69.
70.
The reaction of Cu(CH(3)CN)(4)ClO(4) with 2-pyridylacrylic acid (2-HPYA) affords an unusual mixed-valence Cu(I)-Cu(II) 3-D framework ([Cu(II)(2-PYA)(2)](3).[Cu(I)(2-PYA)](2).(H2O)(2))n (1) with a novel topology which features Cu(II) dimeric units (or paddle-wheel unit). The almost perpendicular coordinating direction between the N atom of pyridyl and the O atom of carboxylate groups may be responsible for the formation of such a novel network. 相似文献