全文获取类型
收费全文 | 468831篇 |
免费 | 3735篇 |
国内免费 | 977篇 |
专业分类
化学 | 233183篇 |
晶体学 | 6831篇 |
力学 | 23603篇 |
综合类 | 15篇 |
数学 | 64965篇 |
物理学 | 144946篇 |
出版年
2019年 | 3247篇 |
2018年 | 11638篇 |
2017年 | 12328篇 |
2016年 | 9923篇 |
2015年 | 4604篇 |
2014年 | 6343篇 |
2013年 | 16062篇 |
2012年 | 15619篇 |
2011年 | 25094篇 |
2010年 | 16429篇 |
2009年 | 16349篇 |
2008年 | 22544篇 |
2007年 | 25653篇 |
2006年 | 13330篇 |
2005年 | 17372篇 |
2004年 | 13564篇 |
2003年 | 12600篇 |
2002年 | 10870篇 |
2001年 | 10749篇 |
2000年 | 8535篇 |
1999年 | 6424篇 |
1998年 | 5612篇 |
1997年 | 5551篇 |
1996年 | 5315篇 |
1995年 | 4895篇 |
1994年 | 5010篇 |
1993年 | 4596篇 |
1992年 | 5271篇 |
1991年 | 5351篇 |
1990年 | 5133篇 |
1989年 | 5041篇 |
1988年 | 5069篇 |
1987年 | 4895篇 |
1986年 | 4649篇 |
1985年 | 6117篇 |
1984年 | 6485篇 |
1983年 | 5417篇 |
1982年 | 5713篇 |
1981年 | 5546篇 |
1980年 | 5457篇 |
1979年 | 5550篇 |
1978年 | 5984篇 |
1977年 | 5738篇 |
1976年 | 5861篇 |
1975年 | 5465篇 |
1974年 | 5560篇 |
1973年 | 5719篇 |
1972年 | 3957篇 |
1971年 | 3390篇 |
1970年 | 3093篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
P. G. Frayne 《International Journal of Infrared and Millimeter Waves》1992,13(5):713-720
At microwave frequencies, frequent use is made in circuit design of the electrical properties of short lengths of resistively terminated transmission line. It will be shown in the following contribution that circuits based on high frequency distributed lines can usefully be modelled at low audio frequencies using lumped element lines. 相似文献
992.
H. G. Georgiadis 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1992,43(4):742-755
A wave-heat correspondence principle is established by utilizing previous operational relations of van der Pol and Bremmer. By the suggested procedure, heat conduction problems can be solved by using an auxiliary wave-propagation problem in conjunction with the correspondence principle. A check on this procedure was provided by solving a mixed BVP of transient heat flow. The present correspondence principle is particularly useful in dealing with IBVPs involving wedge-shaped domains, and characteristic lengths. 相似文献
993.
M. N. Davies 《The Journal of the Operational Research Society》1994,45(12):1363-1373
For the last ten years or so, developments in simulation software and methodology have been focused in two areas: (1) automating the model-building process; and (2) interfacing with other techniques and systems. That both academic and commercial research continues to be carried out in these areas is evidence of the continued popularity of the simulation technique. The most popular application areas where simulation modelling is used include manufacturing (engineering and process), warehousing and communications; not surprisingly, research and developments have therefore been concentrated in these areas. This paper describes the development of a simulation model generator for a different application area, that of clerical office processing of paper and documents for financial service companies. It outlines the reasons why there is a need for such a model generator and discusses the initial design requirements. The paper goes on to detail the developments and re-defined criteria required as the model generator brief changes as a result of practical applications. 相似文献
994.
John L. Wood Johannes Schwarzenberg Edward F. Zganjar Dubravka Rupnik 《Hyperfine Interactions》1992,75(1-4):51-58
State-of-the-art spectroscopy of nuclei far from stability has achieved an extraordinary level of sophistication and detail
in the last ten years. In principle, if a state can be populated, it can be characterized by its energy, spin, parity, and
major decay paths. Sometimes its lifetime can be measured. In practice, one is confronted with enormous complexity. To convert
raw spectroscopic data into nuclear structure data involves a complex process of disentangling gamma rays and conversion electrons
into decay schemes. Specifically, coincidence techniques, especially coincidence intensities, play a crucial role in this
process. Recent examples and methods from work done at UNISOR are presented. 相似文献
995.
Silver nitrate-acetonitrile and π iodine-benzene complexes in thermotropic liquid crystals have been studied by 1H, 2H, and 13C NMR spectroscopy and by optical microscopy. Evidence for at least two silver complexes in each liquid crystal is presented. 相似文献
996.
A. R. Kuznetsov S. G. Lunter S. I. Nikitina A. G. Plyukhin Yu. K. Fedorov 《Journal of Applied Spectroscopy》1992,56(1):68-72
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 56, No. 1, pp. 90–95, January, 1992. 相似文献
997.
G. V. Plyatsko V. N. Maksimovich L. V. Khomlyak 《Journal of Mathematical Sciences》1992,62(1):2518-2523
We solve the thermoplastic problem for a semi-infinite plate under local nonstationary heating by heat sources. The physical equations are taken to be the relations of the nonisothermic theory of plastic flow associated with the Mises fluidity condition. The solution of the problem is constructed by the method of integral equations and the self-correcting method of sequential loading, where time is taken as the loading parameter. We carry out numerical computations of the stresses in the case of heating a plate with heat output by normal-circular heat sources. We study the problem of optimization of heating regimes in order to introduce favorable residual compressive stresses (from the point of view of hardness) in a given region of a half-plane. Two figures.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 27, 1988, pp. 29–34. 相似文献
998.
M.-K. Chen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(1):13-18
We examine the influence of relativistic and QED effects on the existence of the 1,3P
o
H- resonances between n
= 2 and 3 hydrogen thresholds, the relativistic and QED corrections and the coupling effects between the high singlet and triplet
states are considered as first-order perturbations. We firstly obtain accurate non-relativistic resonant energies and widths
of fifteen 1P
o
resonances, and fifteen 3P
o
resonances. The fifteen 1P
o
resonances are classified to be
3
(2, 0)
-
n
( 4 ?
n
? 12) and
3
(1, 1)
+
n
( 3 ?
n
? 8). The fifteen 3P
o
resonances are classified to be
3
(2, 0)
+
n
( 3 ?
n
? 12) and
3
(1, 1)
-
n
( 4 ?
n
? 8). We found there exist six Feshbach resonances for
3
(2, 0)
-
n
(1P
o
) series, four Feshbach resonances for
3
(1, 1)
+
n
(1P
o
) series, seven Feshbach resonances for
3
(2, 0)
+
n
(3P
o
) series, and three Feshbach resonances for
3
(1, 1)
-
n
(1P
o
) series.
Received 22 February 2002 Published online 24 September 2002 相似文献
999.
1000.