全文获取类型
收费全文 | 1523篇 |
免费 | 32篇 |
国内免费 | 2篇 |
专业分类
化学 | 921篇 |
晶体学 | 64篇 |
力学 | 48篇 |
数学 | 203篇 |
物理学 | 321篇 |
出版年
2022年 | 15篇 |
2021年 | 11篇 |
2020年 | 16篇 |
2019年 | 14篇 |
2018年 | 21篇 |
2017年 | 20篇 |
2016年 | 29篇 |
2015年 | 28篇 |
2014年 | 34篇 |
2013年 | 116篇 |
2012年 | 76篇 |
2011年 | 93篇 |
2010年 | 46篇 |
2009年 | 51篇 |
2008年 | 81篇 |
2007年 | 70篇 |
2006年 | 76篇 |
2005年 | 65篇 |
2004年 | 52篇 |
2003年 | 49篇 |
2002年 | 38篇 |
2001年 | 25篇 |
2000年 | 25篇 |
1999年 | 11篇 |
1997年 | 21篇 |
1996年 | 13篇 |
1995年 | 14篇 |
1994年 | 18篇 |
1993年 | 18篇 |
1992年 | 15篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 16篇 |
1987年 | 18篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1984年 | 26篇 |
1983年 | 10篇 |
1982年 | 30篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 14篇 |
1978年 | 13篇 |
1977年 | 20篇 |
1976年 | 17篇 |
1975年 | 20篇 |
1974年 | 13篇 |
1973年 | 16篇 |
1971年 | 11篇 |
1959年 | 11篇 |
排序方式: 共有1557条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Bikshandarkoil R. Srinivasan 《Journal of Chemical Sciences》2004,116(5):251-259
The complexes [MoX4]2− (M = Mo; X = O or S) exist as the monomeric tetrahedral species in aqueous alkaline solutions. Acidification of tetraoxomolybdate
results in the condensation of the tetrahedral units via a series of polyoxomolybdates leading to the ultimate formation of
the trioxide MoO3. Heptamolybdate [Mo7O24]6− is the first major polyanion of the acidification reaction. In contrast, acidification of tetrathiomolybdates leads to the
formation of amorphous molybdenum trisulphide via a dinuclear Mo(V) complex. The formation of the dinuclear Mo(V) complex
precludes the formation of any higher nuclearity Mo(VI)-S complexes in aqueous solution. Thus it is shown that the all-sulphur
analogue of heptamolybdate [M07S24]6− does not exist in alkaline medium and also cannot be isolated from aqueous acidic medium 相似文献
5.
The field of photonic crystals has, over the past few years, received dramatically increased attention. Photonic crystals are artificially engineered structures that exhibit a periodic variation in one, two, or three dimensions of the dielectric constant, with a period of the order of the pertinent light wavelength. Such structures in three dimensions should exhibit properties similar to solid-state electronic crystals, such as bandgaps, in other words wavelength regions where light cannot propagate in any direction. By introducing defects into the periodic arrangement, the photonic crystals exhibit properties analogous to those of solid-state crystals. The basic feature of a photonic bandgap was indeed experimentally demonstrated in the beginning of the 1990s, and sparked a large interest in, and in many ways revitalized, photonics research. There are several reasons for this attention. One is that photonic crystals, in their own right, offer a proliferation of challenging research tasks, involving a multitude of disciplines, such as electromagnetic theory, nanofabrication, semi-conductor technology, materials science, biotechnology, to name a few. Another reason is given by the somewhat more down-to-earth expectations that photonics crystals will create unique opportunities for novel devices and applications, and contribute to solving some of the issues that have plagued photonics such as large physical sizes, comparatively low functionality, and high costs. Herein, we will treat some basics of photonic crystal structures and discuss the state-of-the-art in fabrication as well give some examples of devices with unique properties, due to the use of photonic crystals. We will also point out some of the problems that still remain to be solved, and give a view on where photonic crystals currently stand. 相似文献
6.
7.
V. Mahadevan S. Padma M. Srinivasan 《Journal of polymer science. Part A, Polymer chemistry》1981,19(6):1409-1419
A new class of polyhydrazides having aromatic as well as aliphatic units has been synthesized by low-temperature solution polycondensation from equimolar amounts of diacid chloride and dihydrazides in HMPT as solvent. These polyhydrazides have poor solubilities and their intrisnsic viscosities ranged from 0.2 to 0.6 dl/g. X-ray diffractograms of these polyhydrazides show that the polymers having terephthalic acid dihydrazide unit were more crystalline and all the polymers have densities in the range of 1.2-1.8 g/cm3. Thermogravimetric analysis of these polyhydrazides showed initial weight losses commencing at 220–300°C in both air and nitrogen. 相似文献
8.
9.
Five different polyaniline salts have been prepared by chemical polymerization of aniline in aqueous solution of different acids. The polyaniline base was obtained from the corresponding polyaniline salt by dedoping using aqueous ammonium hydroxide solution. Electron paramagnetic, electronic absorption, infrared spectral and conductivity measurements have been performed on the polyaniline salts and polyaniline bases. This composition and the extent of dopant in polyaniline salt systems have been determined. There is no definite correlation between the conductivity and the stoichiometric ratio between the polyaniline base and the acid, and also the spin concentration. 相似文献
10.
Kui Wu Nathan A. Yee Sangeetha Srinivasan Amir Mahmoodi Michael Zakharian Jose M. Mejia Oneto Maksim Royzen 《Chemical science》2021,12(21):7583
Correction for ‘Click activated protodrugs against cancer increase the therapeutic potential of chemotherapy through local capture and activation’ by Kui Wu et al., Chem. Sci., 2021, 12, 1259–1271, DOI: 10.1039/D0SC06099B.The authors regret that the reference to the bond-breaking bioorthogonal chemistry, termed ‘click-to-release’ was omitted from the original article. In addition, we would like to include a reference describing the synthesis of compound 1, which is an intermediate to the protodrugs described in the original article. These references are listed below as ref. 1 and 2.The Royal Society of Chemistry apologizes for these errors and any consequent inconvenience to authors and readers. 相似文献