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   563298篇
  免费   6269篇
  国内免费   1654篇
化学   299699篇
晶体学   8553篇
力学   24451篇
综合类   16篇
数学   67784篇
物理学   170718篇
  2021年   4634篇
  2020年   5255篇
  2019年   5636篇
  2018年   7216篇
  2017年   7208篇
  2016年   11164篇
  2015年   7109篇
  2014年   10833篇
  2013年   25999篇
  2012年   19896篇
  2011年   24303篇
  2010年   17157篇
  2009年   16905篇
  2008年   22455篇
  2007年   22179篇
  2006年   20719篇
  2005年   18530篇
  2004年   17089篇
  2003年   15165篇
  2002年   14870篇
  2001年   16843篇
  2000年   12738篇
  1999年   9980篇
  1998年   8307篇
  1997年   8051篇
  1996年   7815篇
  1995年   7071篇
  1994年   6962篇
  1993年   6710篇
  1992年   7544篇
  1991年   7480篇
  1990年   7252篇
  1989年   6997篇
  1988年   7007篇
  1987年   6910篇
  1986年   6506篇
  1985年   8507篇
  1984年   8710篇
  1983年   7194篇
  1982年   7297篇
  1981年   7152篇
  1980年   6716篇
  1979年   7262篇
  1978年   7412篇
  1977年   7238篇
  1976年   7178篇
  1975年   6757篇
  1974年   6694篇
  1973年   6851篇
  1972年   4742篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
We report on the effect of commercially important polysaccharides (maltodextrins with variable dextrose equivalent (Paselli SA-2, MD-6 and MD-10) on the surface activity at the air–water interface of small-molecule surfactants (sms), possessing different hydrophobic–lipophilic balance ((SSL (Na+), the main component is a sodium salt of stearol–lactoyl lactic acid, and PGE (080), polyglycerol ester of C18 fatty acid), and widely used in food products. A marked change of the surface activity of sms was found in the presence of maltodextrins by tensiometry. The combined data of laser multiangle light scattering and mixing calorimetry have suggested that this result is governed by specific complex formation between maltodextrins and sms in aqueous medium. Measurements have been made of the molar mass, the second virial coefficient and the enthalpy of intermolecular interactions in aqueous solutions. The implication of a degree of polymerization of maltodextrins in this phenomenon was shown. The interrelation between the molecular parameters of the formed complexes and their surface activity at the air–water interface has been revealed and discussed.  相似文献   
992.
993.
Based on the dinuclear system concept, the role of bending vibrations in creation of the angular momentum of primary fission fragments is investigated. For 252Cf spontaneous fission, the angular momenta of the fragments are calculated as a function of the neutron multiplicity and compared with available experimental data. Different cluster compositions of the 252Cf fission modes at the scission point are considered.  相似文献   
994.
In this work actin is used to illustrate connection of protein fluorescence characteristics with its structure. On one hand, it has been demonstrated what kind of information about the contribution of each tryptophan residues to the bulk fluorescence spectrum can be obtained from the special analysis of protein three-dimensional structure. On the other hand, potentials of intrinsic fluorescence for elucidation of proteins structure, dynamics and processes of folding-unfolding are shown. In particular, using this method a new essentially unfolded kinetic intermediate state of actin was detected and characterized, and the place of inactivated actin and its kinetic predecessor in the process of folding-unfolding was determined. It has been revealed that inactivated actin is not intermediate state between the native and completely unfolded states, as it has been accepted before, but a result of protein misfolding. On the basis of the obtained data a new model of actin folding-unfolding pathway has been proposed.  相似文献   
995.
Results of investigations into the physical properties of a number of new nonlinear crystals are presented. The parameters of frequency converters manufactured on their basis are compared, and second-harmonic generation of CO2 lasers first excited by frequency conversion in LiInSe2, AgGa1– x InxSe2, AgxGaxGexS2(1 + x), and Hg1–x CdxGa2S4 crystals is investigated. The superiority of HgGa2S4, Hg1–x CdxGa2S4, and AgGa1–x InxSe2 over the well-known crystals has been demonstrated for frequency conversion both within the middle-IR range and from the visible range to the middle-IR range. Advantages of LiInSe2 and AgGa1–x InxSe2 crystals are demonstrated for the direct frequency conversion of femtosecond laser radiation to the middle-IR range compared to the cascade frequency conversion and direct frequency conversion in LiInS2 crystals.  相似文献   
996.
B. Ananthanarayan 《Pramana》2003,61(5):911-920
A review of chiral perturbation theory and recent developments on the comparison of its predictions with experiment is presented. Some interesting topics with scope for further elaboration are touched upon.  相似文献   
997.
We prove new theorems on the justification of the averaging method for multifrequency oscillation systems with pulse influence at fixed times.  相似文献   
998.
We consider the inverse problem of finding the unknown time-dependent leading coefficient and the free term in a parabolic equation. Boundary conditions and overdetermination conditions are local. We find conditions for the uniqueness and local existence.  相似文献   
999.
We investigated the laser-induced fluorescence spectra (LIF) of porcine cardiac tissues with different degrees of viability. The data obtained are compared with the results of routine histological investigations and also with the experiments performed with the use of fluorescent probes. It has been found with a high degree of reliability that the loss of the viability of the myocardium tissue leads to the alteration of its LIF spectra. This can be used for low-invasive rapid control of transplant viability in the process of its preparation and during surgery.  相似文献   
1000.
The relaxor properties of Fe-doped TlInS2 crystals are investigated. It is shown that Fe-doped TlInS2 compounds exhibit all features inherent in relaxor ferroelectric materials. The temperature range of existence of the microdomain (relaxor) state and the temperature of the transition from this state to a macro-domain state are determined.  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