全文获取类型
收费全文 | 5274篇 |
免费 | 127篇 |
国内免费 | 267篇 |
专业分类
化学 | 4980篇 |
晶体学 | 27篇 |
力学 | 70篇 |
综合类 | 55篇 |
数学 | 100篇 |
物理学 | 436篇 |
出版年
2024年 | 2篇 |
2023年 | 25篇 |
2022年 | 74篇 |
2021年 | 57篇 |
2020年 | 78篇 |
2019年 | 77篇 |
2018年 | 62篇 |
2017年 | 91篇 |
2016年 | 97篇 |
2015年 | 119篇 |
2014年 | 105篇 |
2013年 | 264篇 |
2012年 | 512篇 |
2011年 | 222篇 |
2010年 | 175篇 |
2009年 | 231篇 |
2008年 | 200篇 |
2007年 | 342篇 |
2006年 | 267篇 |
2005年 | 248篇 |
2004年 | 260篇 |
2003年 | 247篇 |
2002年 | 192篇 |
2001年 | 123篇 |
2000年 | 141篇 |
1999年 | 138篇 |
1998年 | 124篇 |
1997年 | 112篇 |
1996年 | 122篇 |
1995年 | 140篇 |
1994年 | 128篇 |
1993年 | 137篇 |
1992年 | 162篇 |
1991年 | 80篇 |
1990年 | 43篇 |
1989年 | 65篇 |
1988年 | 39篇 |
1987年 | 26篇 |
1986年 | 27篇 |
1985年 | 13篇 |
1984年 | 24篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 15篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
排序方式: 共有5668条查询结果,搜索用时 15 毫秒
1.
M. M. Moustafa 《Journal of Thermal Analysis and Calorimetry》1997,50(3):463-471
The oxime and Schiff's base of N-furoylphenylhydroxylamine form complexes with Co2+, Cu2+, Zn2+ and Fe3+. These complexes were studied by means of the UV — Vis. spectra of nujol mulls, electron spin resonance (ESR) spectra and magnetic susceptibility to determine their stereochemistry. The complexes were characterized via elemental analyses, molar conductivities and thermogravimetric analyses. Organic reagents were used for the gravimetric determination of Co2+, Cu2+ and Fe3+ through the precipitation of their complexes. The compounds were also used for separation of a binary mixture of Cu2+ and Cu2+. Interferences were studied. 相似文献
2.
横向放大率法确定复合光学系统的基点 总被引:2,自引:0,他引:2
介绍了应用测量横向放大率确定两薄透镜组成的复合光学系统基点的方法。由于采用线阵光电耦合器件(CCD)测量物经光学系统成像的横向放大率,提高了测量精度。 相似文献
3.
4.
5.
Keith Jonathan M. Kroese Dirk P. Bryant Darryn 《Methodology and Computing in Applied Probability》2004,6(1):29-53
A recent development of the Markov chain Monte Carlo (MCMC) technique is the emergence of MCMC samplers that allow transitions between different models. Such samplers make possible a range of computational tasks involving models, including model selection, model evaluation, model averaging and hypothesis testing. An example of this type of sampler is the reversible jump MCMC sampler, which is a generalization of the Metropolis–Hastings algorithm. Here, we present a new MCMC sampler of this type. The new sampler is a generalization of the Gibbs sampler, but somewhat surprisingly, it also turns out to encompass as particular cases all of the well-known MCMC samplers, including those of Metropolis, Barker, and Hastings. Moreover, the new sampler generalizes the reversible jump MCMC. It therefore appears to be a very general framework for MCMC sampling. This paper describes the new sampler and illustrates its use in three applications in Computational Biology, specifically determination of consensus sequences, phylogenetic inference and delineation of isochores via multiple change-point analysis. 相似文献
6.
本文研究了在PVA和Tween 80存在下,铋离子与硫氰酸钾和丁基罗丹明B形成缔合型三元配合物,使丁基罗丹明B的荧光熄灭,建立了痕量铋的荧光分析新方法。工作曲线线性范围为0~5.0μg/25mL。方法灵敏度高,ε_(588)为3.5×10~5L·mol~(-1)·cm~(-1),操作简便。用于铸铁中痕量铋的测定,结果满意。 相似文献
7.
Antimonide-based superlattices dedicated to the elaboration of opto-electronic devices have been studied by X-ray scattering techniques. In particular, specular and non-specular X-ray reflectometry experiments have been performed on two MBE-samples elaborated with different shutter sequences at the interfaces. The results have shown a limitation of the incorporation of Sb species in the subsequent InAs layer for one of the samples, as expected.Then, a study on a InGaAs-cap layer/(InGaAs/AlAsSb)N superlattice grown on a InGaAs/InP buffer layer by both specular X-ray reflectometry and High resolution X-ray diffraction is reported. In particular, the results have revealed the presence of a highly disturbed thin-layer on top of the MOVPE-made GaInAs, whose presence has been explained by In-concentration modification during the desoxidation procedure at the surface of the MOVPE-made GaInAs.Beside the results on the Sb-based heterostructures, the use of X-ray scattering metrology as a routinely working non-destructive testing method has been emphasized. 相似文献
8.
A new procedure for the simultaneous spectrophotometric determination of Zn(II) and Ni(II) with 1-(2-pyridylazo)-2-naphthol as chromogenic reagent has been developed. It is based on resolution of the mixed spectrum over the wavelength range 530–590 nm by applying a least-squares fitting program to standard spectra from each component. The spectra are recorded at an apparent pH of 5.0, provided by an acetate buffer in a mixed 6040 v/v 2-ethoxyethanol/water medium. The relative standard deviations for determination of 13.7 g of Ni and 31.0 g of Zn were 1.9 and 1.0%, respectively (8 replications). The method has been applied to the analysis of iron surfaces coated with a Zn-Ni alloy. The results are compared with those obtained by atomic-absorption spectrophotometry. 相似文献
9.
10.
我国法定可使用的合成食用色素主要有5种。即苋菜红、胭脂红、柠檬黄、日落黄和亮蓝。根据调色需要,它们常被混合配置应用.目前一般采用高效液相色谱和层析分离法分析,但尚缺少可靠的同时测定此5组分的化学计量学方法,Loosbroek曾用卡尔曼滤波光度法鉴 相似文献