全文获取类型
收费全文 | 3623篇 |
免费 | 86篇 |
国内免费 | 9篇 |
专业分类
化学 | 2798篇 |
晶体学 | 42篇 |
力学 | 54篇 |
数学 | 215篇 |
物理学 | 609篇 |
出版年
2022年 | 20篇 |
2021年 | 26篇 |
2020年 | 36篇 |
2019年 | 45篇 |
2018年 | 43篇 |
2017年 | 20篇 |
2016年 | 56篇 |
2015年 | 54篇 |
2014年 | 53篇 |
2013年 | 152篇 |
2012年 | 135篇 |
2011年 | 171篇 |
2010年 | 100篇 |
2009年 | 119篇 |
2008年 | 190篇 |
2007年 | 157篇 |
2006年 | 193篇 |
2005年 | 187篇 |
2004年 | 163篇 |
2003年 | 159篇 |
2002年 | 136篇 |
2001年 | 84篇 |
2000年 | 80篇 |
1999年 | 52篇 |
1998年 | 38篇 |
1997年 | 51篇 |
1996年 | 51篇 |
1995年 | 36篇 |
1994年 | 57篇 |
1993年 | 37篇 |
1992年 | 62篇 |
1991年 | 44篇 |
1990年 | 43篇 |
1989年 | 44篇 |
1988年 | 39篇 |
1987年 | 55篇 |
1986年 | 47篇 |
1985年 | 55篇 |
1984年 | 64篇 |
1983年 | 36篇 |
1982年 | 54篇 |
1981年 | 52篇 |
1980年 | 61篇 |
1979年 | 64篇 |
1978年 | 44篇 |
1977年 | 43篇 |
1976年 | 40篇 |
1975年 | 37篇 |
1974年 | 25篇 |
1973年 | 19篇 |
排序方式: 共有3718条查询结果,搜索用时 15 毫秒
11.
Infrared and nuclear magnetic resonance (NMR) spectroscopies have been applied for quantitative comparison on unsaturated bonds in tetrafluoroethylene (TFE)-propylene (P)-vinylidene fluoride (VdF) terpolymers. These spectroscopies have led to consistent results while they are based on completely different principles. It is shown that the absolute concentration can be evaluated from NMR measurements. The behavior of unsaturation has been discussed in terms of after-treatment such as wet and dry treatments. The result obtained here can give the important information to improve the performance of fluoroelastomer based on TFE-P-VdF terpolymers. 相似文献
12.
In this paper, we investigate the exact distribution of the waiting time for ther-th ℓ-overlapping occurrence of success-runs of a specified length in a sequence of two state Markov dependent trials. The
probability generating functions are derived explicitly, and as asymptotic results, relationships of a negative binomial distribution
of orderk and an extended Poisson distribution of orderk are discussed. We provide further insights into the run-related problems from the viewpoint of the ℓ-overlapping enumeration
scheme. We also study the exact distribution of the number of ℓ-overlapping occurrences of success-runs in a fixed number
of trials and derive the probability generating functions. The present work extends several properties of distributions of
orderk and leads us a new type of geneses of the discrete distributions. 相似文献
13.
14.
X.P. Zhu Tomiyuki Yukawa Hisayuki Suematsu Kiyoshi Yatsui Y. Inoue 《Applied Surface Science》2006,252(16):5776-5782
X-ray photoelectron spectroscopy (XPS) is used to probe oxidation states of Si species in particles deposited using a pulsed ion-beam evaporation method. The effects of He ambient gas, ion beam intensity and post-treatments on the oxides composition and oxygen content have been studied. It is found that presence of He ambient gas led to a profound oxidation of Si species as compared to that prepared in vacuum at the same ion-beam ablation energy, i.e. both increase of SiO2 component and oxygen concentration in the oxides coverage. The deposition in He also resulted in an increase of oxygen concentration even under lower ablation intensity, but a higher Si suboxides concentration. It is revealed that the reaction between Si and O was controlled by the ion beam intensity (temperature of Si plasma) and the gas ambient (collision probability of Si and O species). The difference in structure of oxide layers for samples obtained under various conditions is discussed based on the results of XPS analyses. 相似文献
15.
16.
17.
Y Watanabe M Suda Y Matsumoto K Takayama M Matsumoto W Zhao 《Chemical & pharmaceutical bulletin》1991,39(9):2391-2394
The dissolution behavior of the aspirin enteric granule prepared using acylglycerols, glyceryl monostearate (GMS) and glyceryl trilaurate (GTL), was investigated in vitro and in human subjects in a fasting or non-fasting state. Aspirin was slowly released from the granule in vitro at pH 1.2. No acceleration of the aspirin dissolution rate in the medium without lipase and cholic acid was observed when the pH level of the medium increased to a neutral region (pH 6.4). However, the dissolution of aspirin was significantly increased by increasing the concentrations of lipase and cholic acid in the medium. Lipase appears to play an essential role in the dissolution process of aspirin granules. In human subjects, the average levels of the cumulative amount of total salicylate excreted in a urine-time curve, and the mean residence time (MRT) obtained after oral administration of a granule in the fasting state were markedly delayed in comparison with the results observed using an aqueous solution and a crystalline form of aspirin. In comparing the fasting condition with the non-fasting condition (after food ingestion), no significant difference was recognized in the total amount of salicylate excreted in urine to an infinite time (Ae(infinity)), whether the MRT was obtained by granule, crystalline form or aqueous solution. It can be concluded that aspirin granule prepared by GMS and GTL has a property of pancreatic lipase-sensitive dissolution, and its bioavailability is unaffected by food intake. 相似文献
18.
19.
20.
Kiyoshi Kurosawa 《Optical Review》1997,4(1):A38-A44
This paper describes development of the optical current transducers using flint glass fiber as the Faraday effect sensing
element. Excellent polarization properties of the fiber with low birefringence are described, and the design and test data
of a current transducer using the fiber manufactured for use in electric power facilities are reviewed. Experimental results
on flexible characteristics of a scheme with round trip light transmission in the fiber is also reported. 相似文献