首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   59726篇
  免费   2213篇
  国内免费   115篇
化学   38165篇
晶体学   290篇
力学   1797篇
综合类   2篇
数学   10146篇
物理学   11654篇
  2023年   422篇
  2022年   437篇
  2021年   796篇
  2020年   890篇
  2019年   844篇
  2018年   1534篇
  2017年   1169篇
  2016年   1841篇
  2015年   1622篇
  2014年   1690篇
  2013年   3420篇
  2012年   3912篇
  2011年   4102篇
  2010年   2492篇
  2009年   2176篇
  2008年   3573篇
  2007年   3542篇
  2006年   3163篇
  2005年   3037篇
  2004年   2585篇
  2003年   2153篇
  2002年   1845篇
  2001年   1092篇
  2000年   987篇
  1999年   699篇
  1998年   527篇
  1997年   500篇
  1996年   600篇
  1995年   392篇
  1994年   456篇
  1993年   438篇
  1992年   462篇
  1991年   405篇
  1990年   402篇
  1989年   377篇
  1988年   307篇
  1987年   316篇
  1986年   283篇
  1985年   448篇
  1984年   431篇
  1983年   294篇
  1982年   402篇
  1981年   377篇
  1980年   325篇
  1979年   311篇
  1978年   318篇
  1976年   314篇
  1975年   280篇
  1974年   269篇
  1973年   269篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
231.
On the basis of a plane-wave spectrum representation, the polarization features of a transverse quasimonochromatic non-paraxial field have been studied. A relationship has been established between the polarization characteristics in the near field and the coherence and symmetry properties of the beam in the far field.  相似文献   
232.
We prove, as an application of our positive extension argument, a theorem of Parrott concerning the quotient norm with respect to spaces of Hilbert space operators.  相似文献   
233.
It was studied the tin phase composition of the electrodeposited alloys produced at different temperatures and current densities from an acid chloride/fluoride electrolyte and an acid chloride bath. Mössbauer spectra were consistent with a Ni3Sn4 intermetallic compound, dissolved tin, and a Cu?Sn intermetallic compound formed at the interface of the copper substrate.  相似文献   
234.
235.
This work defines homology groups for proof-structures in multiplicative linear logic (see [Gir1], [Gir2], [Dan]). We will show that these groups characterize proof-nets among arbitrary proof-structures, thus obtaining a new correctness criterion and of course a new polynomial algorithm for testing correctness. This homology also bears information on sequentialization. An unexpected geometrical interpretation of the linear connectives is given in the last section. This paper exclusively focuses onabstract proof-structures, i.e. paired-graphs. The relation with actual proofs is investigated in [Gir1], [Gir2], [Dan], [Ret] and [Tro].  相似文献   
236.
A simple High performance liquid chromatographic (HPLC) method for the specific determination of the molecular weight and concentration of hyaluronic acid (HA) in complex mixtures has been developed. Hyaluronate-binding proteins isolated from bovine cartilage labelled by 125I or fluoresceinisothiocyanate were used as specific markers. The specific binding affinities of the markers were compared and were found to have association constants of 1.6 x 10(7) M-1 and 1.2 x 10(7) M-1 respectively. The HA levels and molecular weight distributions can be easily determined in the range 10-500 ng/mL in complex mixtures by the use of markers, molecular sieving HPLC columns and appropriate detectors. It has been demonstrated clearly that the method is useful for the highly specific determination of the parameters in complex biological samples such as serum and synovial fluids and is recommended for clinical applications.  相似文献   
237.
238.
The Z0-boson contribution to the elastic scattering amplitude of an electron in an arbitrary plane-wave electromagnetic field is obtained. Special cases of the plane-wave field are considered.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 33–39, February, 1991.  相似文献   
239.
The use of a direct liquid introduction type liquid chromatographic-mass spectrometric interface to study highly thermally labile rifamycin antibiotics is described. Using negative ionization, abundant molecular ions were observed, and the spectra, also contained structurally significant fragments. Variation of the high-performance liquid chromatographic parameters did not change the spectra, thus making it easy to change chromatographic conditions. In quantitative studies, a surprising correlation was found, indicating that the mass spectrometric signal was proportional to the square of the sample concentration.  相似文献   
240.
In this Note we first introduce the concept of pullback asymptotic compactness. Next, we establish a result ensuring the existence of a pullback attractor for a non-autonomous dynamical system under the general assumptions of pullback asymptotic compactness and the existence of a pullback absorbing family of sets. Finally, we prove the existence of a pullback attractor for a non-autonomous 2D Navier–Stokes model in an unbounded domain, a case in which the theory of uniform attractors does not work since the non-autonomous term is quite general. To cite this article: T. Caraballo et al., C. R. Acad. Sci. Paris, Ser. I 342 (2006).  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号