全文获取类型
收费全文 | 125822篇 |
免费 | 2003篇 |
国内免费 | 388篇 |
专业分类
化学 | 52970篇 |
晶体学 | 1046篇 |
力学 | 7504篇 |
综合类 | 1篇 |
数学 | 40858篇 |
物理学 | 25834篇 |
出版年
2023年 | 361篇 |
2022年 | 327篇 |
2021年 | 517篇 |
2020年 | 726篇 |
2019年 | 682篇 |
2018年 | 11052篇 |
2017年 | 10831篇 |
2016年 | 7666篇 |
2015年 | 2325篇 |
2014年 | 1827篇 |
2013年 | 3684篇 |
2012年 | 6692篇 |
2011年 | 13018篇 |
2010年 | 7307篇 |
2009年 | 7404篇 |
2008年 | 8830篇 |
2007年 | 10722篇 |
2006年 | 2221篇 |
2005年 | 3230篇 |
2004年 | 3218篇 |
2003年 | 3390篇 |
2002年 | 2273篇 |
2001年 | 1268篇 |
2000年 | 1311篇 |
1999年 | 889篇 |
1998年 | 774篇 |
1997年 | 641篇 |
1996年 | 829篇 |
1995年 | 582篇 |
1994年 | 616篇 |
1993年 | 593篇 |
1992年 | 582篇 |
1991年 | 501篇 |
1990年 | 547篇 |
1989年 | 462篇 |
1988年 | 476篇 |
1987年 | 423篇 |
1986年 | 425篇 |
1985年 | 549篇 |
1984年 | 524篇 |
1983年 | 406篇 |
1982年 | 429篇 |
1981年 | 438篇 |
1980年 | 372篇 |
1979年 | 381篇 |
1978年 | 364篇 |
1976年 | 363篇 |
1975年 | 328篇 |
1974年 | 327篇 |
1973年 | 329篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films
were investigated using a number of techniques. A high saturation magnetic induction up to B
s
= 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed,
which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of
the composition.
The text was submitted by the authors in English. 相似文献
63.
In this Note we give a necessary and sufficient condition for the spectral controllability from one simple node of a general network of strings that undergoes transversal vibrations in a sufficiently large time. This condition asserts that no eigenfunction vanishes identically on the string that contains the controlled node. The proof combines the Beurling–Malliavin's theorem and an asymptotic formula for the eigenvalues of the network. The optimal control time may be characterized as twice the sum of the lengths of all the strings of the network. To cite this article: R. Dáger, E. Zuazua, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 545–550. 相似文献
64.
65.
Separation of 23 dansylated amino acids by micellar electrokinetic chromatography at low temperature
Summary The baseline separation of 23 dansylated amino acids (including 3 didansylated species) is reported. Lowering of the analysis
temperature and fine control of the surfactant concentration were essential in obtaining this result. Calibration graphs with
good linearity were obtained. 相似文献
66.
The capability of gated saturable absorbers for single-pulse selection is studied theoretically using the classical space-time-dependent rate-equation model. The dynamics of operation is followed experimentally by the well-known pump—probe technique. Comparing the theoretical and experimental results, it is found that gated saturable absorbers can efficiently be used for pulse forming and pulse selection of pulses longer than picosecond. 相似文献
67.
A forecasting model is developed for the number of daily applications for loans at a financial services telephone call centre. The purpose of the forecasts and the associated prediction intervals is to provide effective staffing policies within the call centre. The model building process is constrained by the availability of only 2 years and 7 months of data. The distinctive feature of the data is that demand is driven in the main by advertising. The analysis given focuses on applications stimulated by press advertising. Unlike previous analyses of broadly similar data, where ARIMA models were used, a model with a dynamic level, multiplicative calendar effects and a multiplicative advertising response is developed and shown to be effective. 相似文献
68.
Chee Sing Yap 《The Journal of the Operational Research Society》1989,40(7):649-658
This paper describes three case studies which investigated issues relating to the implementation and management of advanced information technology. The benefits derived from information technology were found to vary from one organization to another. These studies provide further evidence to support earlier research findings that senior management has an important role to play in the effective exploitation of information technology, and that the investment approach taken by an organization has a significant effect on the development of computer-based information systems. The effectiveness of a system depends not only on applying the appropriate technology, but also on how successfully technical and behavioural issues are resolved. 相似文献
69.
70.