全文获取类型
收费全文 | 2087篇 |
免费 | 68篇 |
国内免费 | 5篇 |
专业分类
化学 | 1382篇 |
晶体学 | 70篇 |
力学 | 70篇 |
数学 | 216篇 |
物理学 | 422篇 |
出版年
2023年 | 12篇 |
2022年 | 36篇 |
2021年 | 29篇 |
2020年 | 32篇 |
2019年 | 31篇 |
2018年 | 52篇 |
2017年 | 31篇 |
2016年 | 49篇 |
2015年 | 48篇 |
2014年 | 66篇 |
2013年 | 156篇 |
2012年 | 140篇 |
2011年 | 137篇 |
2010年 | 79篇 |
2009年 | 73篇 |
2008年 | 109篇 |
2007年 | 102篇 |
2006年 | 99篇 |
2005年 | 86篇 |
2004年 | 70篇 |
2003年 | 65篇 |
2002年 | 45篇 |
2001年 | 37篇 |
2000年 | 38篇 |
1999年 | 13篇 |
1998年 | 12篇 |
1997年 | 22篇 |
1996年 | 14篇 |
1995年 | 21篇 |
1994年 | 19篇 |
1993年 | 21篇 |
1992年 | 18篇 |
1989年 | 15篇 |
1988年 | 18篇 |
1987年 | 19篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 29篇 |
1982年 | 33篇 |
1981年 | 13篇 |
1980年 | 12篇 |
1979年 | 14篇 |
1978年 | 15篇 |
1977年 | 21篇 |
1976年 | 16篇 |
1975年 | 20篇 |
1974年 | 14篇 |
1973年 | 15篇 |
1971年 | 11篇 |
1959年 | 11篇 |
排序方式: 共有2160条查询结果,搜索用时 10 毫秒
1.
2.
3.
N. Srinivasan R.C. Johnson N. Kasthurikrishnan P. Wong R.G. Cooks 《Analytica chimica acta》1997,350(3):128-271
An overview of membrane introduction mass spectrometry (MIMS) is presented and comparisons are made with other direct sample introduction techniques. Special attention is given to the unique advantages and the limitations of newer variants on the MIMS technique, including affinity MIMS, reverse-phase and trap MIMS. The salient features of the interfaces used in MIMS are summarized and the various membrane materials commonly used are delineated. The applicability of MIMS is illustrated via discussion of
- 1. (i) bioreactor monitoring (represented by yeast fermentation),
- 2. (ii) environmental monitoring (illustrated by analysis of contaminated ground water samples) and
- 3. (iii) on-line chemical reaction monitoring (exemplified by the photolysis of aryl esters).
4.
5.
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
6.
A short and efficient enantioselective synthesis of sulfobacin A has been achieved using the Sharpless asymmetric dihydroxylation and the regiospecific nucleophilic opening of a cyclic sulfate as the key steps. 相似文献
7.
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
8.
9.
10.
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