全文获取类型
收费全文 | 48722篇 |
免费 | 6866篇 |
国内免费 | 5371篇 |
专业分类
化学 | 34851篇 |
晶体学 | 607篇 |
力学 | 2639篇 |
综合类 | 412篇 |
数学 | 5548篇 |
物理学 | 16902篇 |
出版年
2024年 | 147篇 |
2023年 | 886篇 |
2022年 | 1426篇 |
2021年 | 1561篇 |
2020年 | 1699篇 |
2019年 | 1655篇 |
2018年 | 1416篇 |
2017年 | 1359篇 |
2016年 | 2064篇 |
2015年 | 2086篇 |
2014年 | 2455篇 |
2013年 | 3327篇 |
2012年 | 4052篇 |
2011年 | 4304篇 |
2010年 | 2955篇 |
2009年 | 2803篇 |
2008年 | 3170篇 |
2007年 | 2978篇 |
2006年 | 2656篇 |
2005年 | 2331篇 |
2004年 | 1781篇 |
2003年 | 1490篇 |
2002年 | 1421篇 |
2001年 | 1154篇 |
2000年 | 1021篇 |
1999年 | 1034篇 |
1998年 | 844篇 |
1997年 | 798篇 |
1996年 | 772篇 |
1995年 | 677篇 |
1994年 | 664篇 |
1993年 | 581篇 |
1992年 | 511篇 |
1991年 | 466篇 |
1990年 | 404篇 |
1989年 | 301篇 |
1988年 | 252篇 |
1987年 | 216篇 |
1986年 | 195篇 |
1985年 | 198篇 |
1984年 | 143篇 |
1983年 | 88篇 |
1982年 | 95篇 |
1981年 | 70篇 |
1980年 | 66篇 |
1979年 | 58篇 |
1978年 | 40篇 |
1976年 | 37篇 |
1974年 | 40篇 |
1973年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
3.
Yoshiaki Murata Cheng-Huang Lin Totaro Imasaka 《Fresenius' Journal of Analytical Chemistry》1993,346(6-9):543-544
Summary A supersonic jet spectrum of 9,10-dichloroanthracene is measured by stimulated-emission-pumping fluorescence dip spectrometry and conventional fluorescence spectrometry. The performance obtained is compared for these spectrometric methods, providing same information concerned with the energy level of the ground state. The former is more preferential for measurement of a high-resolution spectrum, since the spectral resolution is determined by the linewidth of the dumping laser. On the other hand, the latter is more preferential for measurement with better sensitivity at the expense of the spectral resolution, since the fluorescence throughput can be improved by increasing the slit width of the monochromator.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday 相似文献
4.
The theory of tree-growing (RECPAM approach) is developed for outcome variables which are distributed as the canonical exponential family. The general RECPAM approach (consisting of three steps: recursive partition, pruning and amalgamation), is reviewed. This is seen as constructing a partition with maximal information content about a parameter to be predicted, followed by simplification by the elimination of ‘negligible’ information. The measure of information is defined for an exponential family outcome as a deviance difference, and appropriate modifications of pruning and amalgamation rules are discussed. It is further shown how the proposed approach makes it possible to develop tree-growing for situations usually treated by generalized linear models (GLIM). In particular, Poisson and logistic regression can be tree-structured. Moreover, censored survival data can be treated, as in GLIM, by observing a formal equivalence of the likelihood under random censoring and an appropriate Poisson model. Three examples are given of application to Poisson, binary and censored survival data. 相似文献
5.
6.
设函数f(w)为凸区域D内的单叶解析函数,对于2≤n≤8和所有w∈D,本文得到估计式|f(n)(w)/f'(w)|的精确上界.这个结果推广了一些已知的结论. 相似文献
7.
8.
The structural evolution in amorphous silicon and germanium thin films has been investigated by high-resolution transmission electron microscopy (HRTEM) in conjunction with autocorrelation function (ACF) analysis. The results established that the structure of as-deposited semiconductor films is of a high density of nanocrystallites embedded in the amorphous matrix. In addition, from ACF analysis, the structure of a-Ge is more ordered than that of a-Si. The density of embedded nanocrystallites in amorphous films was found to diminish with annealing temperature first, then to increase. The conclusions also corroborate well with the results of diminished medium-range order in annealed amorphous films determined previously by a variable coherence microscopy method. 相似文献
9.
10.
The drawbacks of our earlier report of preparing fuel cell catalyst arrays by borohydride reduction of inkjet prepared arrays of metal salts are discussed along with the need for inclusion of state-of-the-art metrics in all array screening. An alternative method for screening of hydrogen/air cathode catalysts, direct methanol fuel cell (DMFC) anode catalysts, and catalyst loading studies is provided. State-of-the-art Johnson Matthey catalysts were used in control experiments to demonstrate the utility of the array fuel cell for high throughput screening of fuel cell catalysts in the 3-4 mg/cm2 range. This report lays out hard learned rules for high throughput screening and demonstrates that the array fuel cell can be used for very precise screening of libraries of membrane electrode assembly (MEA) components without the pitfalls discussed in the introduction. 相似文献