全文获取类型
收费全文 | 342885篇 |
免费 | 4203篇 |
国内免费 | 1685篇 |
专业分类
化学 | 188976篇 |
晶体学 | 5248篇 |
力学 | 14287篇 |
综合类 | 64篇 |
数学 | 36854篇 |
物理学 | 103344篇 |
出版年
2020年 | 2742篇 |
2019年 | 2952篇 |
2018年 | 3851篇 |
2017年 | 3891篇 |
2016年 | 5742篇 |
2015年 | 3763篇 |
2014年 | 5526篇 |
2013年 | 14065篇 |
2012年 | 11605篇 |
2011年 | 14177篇 |
2010年 | 10067篇 |
2009年 | 9960篇 |
2008年 | 13484篇 |
2007年 | 13431篇 |
2006年 | 12799篇 |
2005年 | 11720篇 |
2004年 | 10440篇 |
2003年 | 9423篇 |
2002年 | 9270篇 |
2001年 | 11223篇 |
2000年 | 8378篇 |
1999年 | 6270篇 |
1998年 | 4794篇 |
1997年 | 4851篇 |
1996年 | 4721篇 |
1995年 | 4249篇 |
1994年 | 4290篇 |
1993年 | 4021篇 |
1992年 | 4722篇 |
1991年 | 4844篇 |
1990年 | 4536篇 |
1989年 | 4427篇 |
1988年 | 4341篇 |
1987年 | 4298篇 |
1986年 | 4124篇 |
1985年 | 5345篇 |
1984年 | 5389篇 |
1983年 | 4431篇 |
1982年 | 4660篇 |
1981年 | 4285篇 |
1980年 | 4080篇 |
1979年 | 4498篇 |
1978年 | 4768篇 |
1977年 | 4799篇 |
1976年 | 4752篇 |
1975年 | 4366篇 |
1974年 | 4479篇 |
1973年 | 4529篇 |
1972年 | 3361篇 |
1971年 | 2672篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
101.
K Kawasaki T Tsuji K Hirase M Miyano Y Imoto M Iwamoto 《Chemical & pharmaceutical bulletin》1991,39(3):584-589
N-Terminal tripeptide analogs of fibrin alpha-chain were synthesized and their inhibitory effect on fibrinogen/thrombin clotting was examined. A new water-soluble active ester, 3-pyridinium ester, was used for the synthesis. Among the synthetic peptides, H-Gly-Pro-Arg-hexamethyleneimine exhibited the highest inhibitory effect on fibrinogen-thrombin clotting. 相似文献
102.
The object of this note is to prove the followingTheorem Let{a_n}and{b_n}be sequences of real numbers such that0<∑∑a_n~2<+∞and0<∑b_n~2<+∞.Then we have the inequalitysum from m=1 to∞sum from n=1 to∞a_mb_n/m+n<{sum from n=1 to∞(π-θ/n~(1/2)a_n~2}~1/2{sum from n=1 to∞(π-θ/n~(1/2)b_n~2}~1/2 (1)whereθ=3/2~(1/2)-1=1.121320343. 相似文献
103.
104.
A. L. Apanasenko A. V. Kuznichenko Yu. B. Govyadovskii V. G. Yakunin 《Journal of Applied Spectroscopy》1991,54(3):271-276
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 3, pp. 438–444, March, 1991. 相似文献
105.
Rainer Löwen 《Journal of Geometry》1989,36(1-2):110-116
We prove that a spread S over a locally compact nondlscrete field F defines a topological translation plane if and only if the spread is compact. For F=R, this is implicit in Breuning's thesis [Bre], cf. [B 2]. For the proof, we describe the point set of the projective translation plane as a quotient space of some projective space, with identifications taking place in one hyperplane. This is new even for F=R. 相似文献
106.
The structural properties of polycrystalline silicon films, prepared by plasma enhanced chemical vapor deposition system, with different flow rates of SiH4/SiF4 mixtures at 300 °C were investigated. This study indicates that the low hydrogen coverage on the growing surface, under optimum fluorine radicals, will be leaded to an improvement of crystallized area as compared with case of high hydrogen coverage surface. Moreover, the studies of the role of SiH4 and SiF4 radicals show that the SiH4 radicals are important in the nucleation and growth of grains. However, SiF4 radicals are effective in the structural change of grain boundaries regions and by this way, in the present system, establish the growth of grains under the dominant 〈1 1 0〉 direction. The stress investigation indicates that addition of high flow rate of SiF4 in amorphous film, results in the nearly stress free films. Finally, we found that the changes in g-value reflect the changes in the intrinsic compressive and tensile stress in the both polycrystalline and amorphous silicon films. 相似文献
107.
108.
P Vincent A BrioudeC Journet S RabasteS.T Purcell J Le BrusqJ.C Plenet 《Journal of Non》2002,311(2):130-137
We report here the successful inclusion of carbon nanotubes (CNs) into a TiO2 matrix prepared by a sol-gel method. The presence of CNs in the sol-gel matrix and the structure of the film were analyzed principally by transmission electron microscopy. Complementary information about the behavior of embedded carbon nanotubes versus heat treatment and ion irradiation were obtained by X-ray photoelectron spectroscopy. The elaboration of an inorganic matrix containing embedded carbon nanotubes leads to a new nanocomposite. The possible applications of this nanocomposite are discussed. 相似文献
109.
L. Aggoun 《Mathematical and Computer Modelling》2002,36(11-13)
In this paper, finite-dimensional recursive filters for space-time Markov random fields are derived. These filters can be used with the expectation maximization (EM) algorithm to yield maximum likelihood estimates of the parameters of the model. 相似文献
110.