全文获取类型
收费全文 | 223509篇 |
免费 | 3217篇 |
国内免费 | 622篇 |
专业分类
化学 | 124529篇 |
晶体学 | 3414篇 |
力学 | 8460篇 |
综合类 | 4篇 |
数学 | 23832篇 |
物理学 | 67109篇 |
出版年
2018年 | 1638篇 |
2016年 | 3105篇 |
2015年 | 2400篇 |
2014年 | 3181篇 |
2013年 | 9507篇 |
2012年 | 6570篇 |
2011年 | 8193篇 |
2010年 | 5273篇 |
2009年 | 5058篇 |
2008年 | 7510篇 |
2007年 | 7640篇 |
2006年 | 7217篇 |
2005年 | 6530篇 |
2004年 | 5838篇 |
2003年 | 5152篇 |
2002年 | 4992篇 |
2001年 | 6278篇 |
2000年 | 4865篇 |
1999年 | 3823篇 |
1998年 | 3011篇 |
1997年 | 3066篇 |
1996年 | 3107篇 |
1995年 | 2842篇 |
1994年 | 2766篇 |
1993年 | 2731篇 |
1992年 | 3133篇 |
1991年 | 2904篇 |
1990年 | 2887篇 |
1989年 | 2868篇 |
1988年 | 2806篇 |
1987年 | 2823篇 |
1986年 | 2620篇 |
1985年 | 3611篇 |
1984年 | 3619篇 |
1983年 | 2990篇 |
1982年 | 3203篇 |
1981年 | 3136篇 |
1980年 | 3036篇 |
1979年 | 3136篇 |
1978年 | 3414篇 |
1977年 | 3215篇 |
1976年 | 3104篇 |
1975年 | 2957篇 |
1974年 | 2905篇 |
1973年 | 2920篇 |
1972年 | 1852篇 |
1968年 | 2035篇 |
1967年 | 2225篇 |
1966年 | 2034篇 |
1965年 | 1602篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Stability theorems for projections and central symmetrization 总被引:3,自引:0,他引:3
H. Groemer 《Archiv der Mathematik》1991,56(4):394-399
962.
本文用超声相比较方法测定了高Tc超导体La1.85Sr0.15CuO4,La2CuO4和YBa2Cu3O7的纵波和横波声速,进而导出了它们的纵向模量、切变模量、杨氏模量、泊松比、德拜温度及定体比热。在La1.85Sr0.15CuO4样品上,还进行了压力实验,发现所有弹性模量都是随压强增加而增加。定体比热cV和泊松比σ在高压下则略有下降。德拜温度是随压强增加而增加的。 相似文献
963.
We investigate which types of asymptotic distributions can be generated by the knots of convergent sequences of interpolatory integration rules. It will turn out that the class of all possible distributions can be described exactly, and it will be shown that the zeros of polynomials that are orthogonal with respect to varying weight functions are good candidates for knots of integration rules with a prescribed asymptotic distribution.Research supported by the Deutsche Forschungsgemeinschaft (AZ: Sta 299/4-2). 相似文献
964.
Brecht S.H. Gladd N.T. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1992,20(6):678-690
The structuring of plasma shells expanding into a magnetized plasma at velocities less than the Alfven speed is considered. The structuring phenomenon is studied with hybrid simulations. The hybrid simulations are conducted for two characteristic parameter sets: one set representative of magnetized ion experiments and one set representative of unmagnetized ion experiment. A complementary theoretical study of structuring instabilities using nonlocal, two fluid theory is discussed. Under the conditions representative of the laser-target experiments, the simulation observed structuring with azimuthal wavelengths similar to those observed in the experiment. Fluid theory, on the other hand, predicts that the most rapidly growing azimuthal modes are much shorter than observations, a result consistent with previous theoretical analyses 相似文献
965.
S. Descotes N.H. Fuchs L. Girlanda J. Stern 《The European Physical Journal C - Particles and Fields》2002,24(3):469-483
The recently published E865 data on charged decays and phases are reanalyzed to extract values of the two S-wave scattering lengths, of the subthreshold parameters and , of the low-energy constants and as well as of the main two-flavour order parameters: and in the limit taken at the physical value of the strange quark mass. Our analysis is exclusively based on direct experimental information
on phases below 800 MeV and on the new solutions of the Roy equations by Ananthanarayan et al. The result is compared with the
theoretical prediction relating 2a
0
0-5a
0
2 and the scalar radius of the pion, which was obtained in two-loop Chiral Perturbation Theory. A discrepancy at the 1- level is found and commented upon.
Received: 11 December 2001 / Revised version: 28 March 2002 / Published online: 7 June 2002 相似文献
966.
A. Dyulgerov N. Handjieva H. Saadi S. Popov I. Baranovska 《Journal of mass spectrometry : JMS》1992,27(7):795-798
The direct chemical ionization mass spectra with isobutane of 14 silylated iridoid glucosides of different structural types were studied. The dependence of the intensity of different peaks on the structure and stereochemistry of the investigated compounds is discussed. 相似文献
967.
968.
969.
C.J. Lu H.M. Shen S.B. Ren Y.N. Wang 《Applied Physics A: Materials Science & Processing》1997,65(4-5):395-401
3 thin films is systematically studied by using X-ray diffraction (XRD). The PbTiO3 thin films with different average grain sizes were prepared on various substrates by a sol-gel process. The films on NaCl
and fused glass are randomly grain-oriented, while those on (111)Pt/Ti/SiO2/Si are highly {100} cubic index grain-oriented . It is found from the XRD patterns of the films on NaCl that with decreasing
average grain size from 230 to 80 nm, the intensities of high h index (h>l) peaks (hkl), such as (100), (110), (200), (201),
(210), (211), etc., decrease rapidly and ultimately disappear, whereas another set of peaks (lkh), including (001), (002),
(102), (112), etc., are still intense. This interesting result suggests that at grain size below a certain critical size an
increasing number of grains no longer show 90°-domains, which is confirmed by TEM observations. Meanwhile, X-ray evidence
of such a grain-size-related absence of 90°-domains is also found for PbTiO3 films on Pt(111) and fused-glass substrates. The volume fractions of single-domain grains (without 90°-domains) in the films
are estimated from their XRD patterns. By combining SEM and TEM investigations, the critical grain size for the formation
of 90°-domains is further determined to be near 200 nm.
Received: 19 December 1996/Accepted: 24 March 1997 相似文献
970.
The ability to quantitatively map the distribution of elements on the micrometer scale and smaller with high sensitivity and isotopic discrimination is unique to ion microscopy. The information contained in ion images can be crucial to the study of the solid state, where chemical heterogeneity is often directly related to observed behavior. The tools of digital image processing allow the extraction of quantitative information from the image data. These techniques coupled with improved instrumentation for the detection of ion images drastically increase the problem solving capabilities of the ion microscope. The use of such methods and instrumentation in the ion microscopic analyses of cell cultures and tissues of biological and biomedical relevance will be discussed. 相似文献