全文获取类型
收费全文 | 3592篇 |
免费 | 134篇 |
国内免费 | 17篇 |
专业分类
化学 | 2793篇 |
晶体学 | 36篇 |
力学 | 67篇 |
数学 | 163篇 |
物理学 | 684篇 |
出版年
2022年 | 26篇 |
2021年 | 36篇 |
2020年 | 43篇 |
2019年 | 71篇 |
2018年 | 50篇 |
2017年 | 17篇 |
2016年 | 59篇 |
2015年 | 75篇 |
2014年 | 64篇 |
2013年 | 191篇 |
2012年 | 197篇 |
2011年 | 201篇 |
2010年 | 95篇 |
2009年 | 126篇 |
2008年 | 212篇 |
2007年 | 207篇 |
2006年 | 231篇 |
2005年 | 181篇 |
2004年 | 172篇 |
2003年 | 133篇 |
2002年 | 133篇 |
2001年 | 70篇 |
2000年 | 74篇 |
1999年 | 44篇 |
1998年 | 23篇 |
1997年 | 28篇 |
1996年 | 48篇 |
1995年 | 37篇 |
1994年 | 34篇 |
1993年 | 37篇 |
1992年 | 51篇 |
1991年 | 39篇 |
1990年 | 51篇 |
1989年 | 54篇 |
1988年 | 43篇 |
1987年 | 36篇 |
1986年 | 31篇 |
1985年 | 72篇 |
1984年 | 61篇 |
1983年 | 23篇 |
1982年 | 41篇 |
1981年 | 31篇 |
1980年 | 36篇 |
1979年 | 40篇 |
1978年 | 35篇 |
1977年 | 31篇 |
1976年 | 33篇 |
1975年 | 25篇 |
1974年 | 17篇 |
1973年 | 22篇 |
排序方式: 共有3743条查询结果,搜索用时 15 毫秒
11.
12.
Hisatoyo Morinaga Bungo Ochiai Hideharu Mori Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2007,45(5):736-744
Natural human hair was successfully modified by the graft polymerization of trimethylene carbonate, β‐propiolactone, ε‐caprolactone, glycidol, ε‐caprolactam, and 5,5‐dimethyl‐1,3‐dioxane‐2‐thione. In contrast, we could not modify natural human hair by the graft polymerization of oxetane under similar conditions. The model reaction suggested that the main initiating species in these polymerizations were the amino, thiol, and hydroxyl groups in hair, which could induce ring‐opening polymerization. Among the tested monomers, β‐propiolactone was most effective for hair modification with its graft polymer, whose concentration was as high as 0.5 g/g of hair though polymerization under mild conditions. The effects of the hair pretreatment and polymerization temperature on the weight ratio of the grafted polymers were also investigated. Hair modified by grafted polymers was characterized with scanning electron microscopy and Fourier transform infrared measurements. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 736–744, 2007 相似文献
13.
Recently commercial equipment using sedimentation field flow fractionation (SFFF) has become available for analysis of particulate materials in the sub-micron range. This paper describes the DuPont instrument and discusses its performance. A particular study is described on the comparison of the SFFF technique with that of quasi-elastic light scattering (QELS). The paper concludes that the instrument is capable of measuring particle size distributions with high resolution and precision, provided that no particles above the upper size limit — about 1 μm — are present. 相似文献
14.
15.
16.
Analysis of Spectral Reflectance Using Normalization Method from Endoscopic Spectroscopy System 总被引:2,自引:0,他引:2
Masao Sambongi Makoto Igarashi Takashi Obi Masahiro Yamaguchi Nagaaki Ohyama Masahiko Kobayashi Yasushi Sano Shigeaki Yoshida Kazuhiro Gono 《Optical Review》2002,9(6):238-243
Objective assessment of gastrointestinal mucosal color is extremely important in the endoscopic diagnosis of digestive tract disease. In this paper, we propose a method to clarify the spectral characteristics of gastric and colon cancer. A large number of spectral reflectance data of mucous membrane are measured by the endoscopic spectroscopy system (ESS) in the National Cancer Center Hospital East, Kashiwa, Japan and the Department of Internal Medicine, Self-Defense Force Center Hospital, Tokyo, Japan. We assume that early cancer appears primarily in the spectral data of short wavelength, because it is usually present in a superficial cell where short wavelength light is scattered more strongly than long wavelength light. To identify the features in the short wavelength components, the spectral reflectance was divided by the reflectance of a long wavelength. We investigated the possibility of distinguishing early cancer from normal spectral data through statistical analysis, employing the projection axis as the mean difference between them. Early cancer and normal spectral data were projected on the projection axis, and the Student’s T-test was applied to evaluate the mean of the distribution between these data. 相似文献
17.
Y. Masuda K. Asahi J. Kura Y. Mori H. Sato H. M. Shimizu 《Hyperfine Interactions》1992,74(1-4):149-157
An experimental scheme of the spin detailed balance in polarized neutron transmission through a polarized nuclear target is
discussed for the T-violation test. The value of the spin detailed balance is estimated by using the data of the scattering
amplitudes. The nuclear polarizations of proton,3He and139La are discussed for the T-violation experiment. 相似文献
18.
Crosslinked poly(N-isopropylacrylamide) gel was tested on the feasibility for a preparative electrophoretic matrix. Horse heart myoglobin and bovine hemoglobin were well separated on the gel matrix electrophoretically by molecular sieving effect of the gel network. Relative mobilities of those proteins in the gel were larger than those in a crosslinked polyacrylamide gel of the same polymer concentration. After the separation, the protein-containing portion of the gel underwent swelling at 4°C and deswelling at 37°C, alternatively. As a result of the deswelling, each protein was recovered in a discharged solution out of the gel at almost 100% yield. 相似文献
19.
20.
Masato Matsugi Masakazu Hasegawa Sachina Okamoto Yoshimi Ikeya Yuji Mori 《Tetrahedron letters》2007,48(23):4147-4150
A modified light-fluorous Mukaiyama reagent bearing a C8F17 tag was prepared and examined in ester and amide forming condensation reactions. Following the reactions, the desired product was effectively separated from the fluorous pyridone by-product using a simple fluorous solid phase extraction. 相似文献