全文获取类型
收费全文 | 4301篇 |
免费 | 128篇 |
国内免费 | 26篇 |
专业分类
化学 | 3365篇 |
晶体学 | 48篇 |
力学 | 45篇 |
数学 | 230篇 |
物理学 | 767篇 |
出版年
2023年 | 23篇 |
2022年 | 26篇 |
2021年 | 36篇 |
2020年 | 51篇 |
2019年 | 58篇 |
2018年 | 34篇 |
2017年 | 31篇 |
2016年 | 79篇 |
2015年 | 72篇 |
2014年 | 118篇 |
2013年 | 235篇 |
2012年 | 197篇 |
2011年 | 244篇 |
2010年 | 152篇 |
2009年 | 145篇 |
2008年 | 254篇 |
2007年 | 241篇 |
2006年 | 264篇 |
2005年 | 250篇 |
2004年 | 248篇 |
2003年 | 212篇 |
2002年 | 196篇 |
2001年 | 97篇 |
2000年 | 90篇 |
1999年 | 48篇 |
1998年 | 47篇 |
1997年 | 41篇 |
1996年 | 40篇 |
1995年 | 33篇 |
1994年 | 50篇 |
1993年 | 38篇 |
1992年 | 54篇 |
1991年 | 35篇 |
1990年 | 28篇 |
1989年 | 29篇 |
1988年 | 37篇 |
1987年 | 28篇 |
1986年 | 29篇 |
1985年 | 62篇 |
1984年 | 64篇 |
1983年 | 37篇 |
1982年 | 44篇 |
1981年 | 50篇 |
1980年 | 42篇 |
1979年 | 43篇 |
1978年 | 35篇 |
1977年 | 34篇 |
1976年 | 28篇 |
1974年 | 29篇 |
1973年 | 29篇 |
排序方式: 共有4455条查询结果,搜索用时 31 毫秒
11.
12.
We propose an extrapolation algorithm for initial value problems in ordinary differential equations. In the algorithm, an appropriately chosen stepsizeH is divided into smaller stepsizes by a sequence and a new stopping rule is proposed. The sequences applied to the algorithm are Romberg {2,4,8,16,32,...}, Bulirsch {2,4,6,8,16...} and Harmonic {2,4,6,8,10,12,...} types. The proposed algorithm is compared numerically with the algorithm introduced by Stoer. In view of the accuracy of numerical solutions, the relatively small number of calculations, the stability and reliability of the algorithm, we found that the algorithm with the Romberg sequence is the best. 相似文献
13.
Dong Hwan Choi Yoshio Katakura Rieko Matsuda Yuzuru Hayashi Masato Hirobe Yasuhiro Goda Kazuaki Ninomiya Suteaki Shioya 《Analytical sciences》2007,23(2):215-218
The mathematical model for predicting the precision, limit of detection (LOD) and range of quantitation (ROQ) in a competitive enzyme-linked immunosorbent assay (ELISA) proposed by Hayashi et al. (Anal. Chem., 2004, 76, 1295) was validated. The model describes the relative standard deviation (RSD) of concentration estimates by the RSDs of pipetting volumes of analyte, enzyme-conjugated antigen, antibody and substrate solutions, and the standard deviation (SD) of inherent absorbances between the wells in an ELISA plate. For 6 kinds of direct competitive ELISA kits, the LOD and ROQ predicted by the model agreed well with those obtained by experiments with real samples. It was also confirmed that the model is applicable to the prediction of uncertainty that depends on the pipetting error of the viscous antiserum solution. The model was demonstrated to be useful for estimating the LOD and ROQ of competitive ELISA. 相似文献
14.
15.
16.
17.
Upper bounds for survival probability of the contact process 总被引:3,自引:0,他引:3
18.
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
19.
Noriko SUTO Makoto HARADA Jun IZUTSU Toshiyasu NAGAO 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2006,82(5):175-180
In order to accurately estimate the geomagnetic transfer functions in the area of the volcano Mt. Iwate (IWT), we applied the interstation transfer function (ISTF) method to the three-component geomagnetic field data observed at Mt. Iwate station (IWT), using the Kakioka Magnetic Observatory, JMA (KAK) as remote reference station. Instead of the conventional Fourier transform, in which temporary transient noises badly degrade the accuracy of long term properties, continuous wavelet transform has been used. The accuracy of the results was as high as that of robust estimations of transfer functions obtained by the Fourier transform method. This would provide us with possibilities for routinely monitoring the transfer functions, without sophisticated statistical procedures, to detect changes in the underground electrical conductivity structure. 相似文献
20.
B. F. Araujo H. T. Matsuda T. A. Kuada J. A. Araujo 《Journal of Radioanalytical and Nuclear Chemistry》1992,166(1):75-83
In the actinide separation process using TBP as extractant, hydrolytic and radiolytic reactions cause a gradual decomposition of the extractant, resulting in the formation of degradation products which can affect process performance adversely. The TBP diluent has to be cleaned from these degradation products before it is reused. This paper deals with a procedure for solvent cleanup, using a fourstage continuous contactor for increasing the scrubbing efficiency. 相似文献