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   19002篇
  免费   309篇
  国内免费   299篇
化学   10334篇
晶体学   137篇
力学   1439篇
综合类   17篇
数学   2699篇
物理学   4984篇
  2020年   255篇
  2019年   310篇
  2018年   375篇
  2017年   360篇
  2016年   490篇
  2015年   244篇
  2014年   414篇
  2013年   582篇
  2012年   563篇
  2011年   578篇
  2010年   575篇
  2009年   566篇
  2008年   564篇
  2007年   586篇
  2006年   461篇
  2005年   404篇
  2004年   391篇
  2003年   432篇
  2002年   492篇
  2001年   453篇
  2000年   332篇
  1999年   261篇
  1998年   237篇
  1997年   230篇
  1993年   236篇
  1992年   239篇
  1991年   245篇
  1990年   265篇
  1989年   259篇
  1987年   235篇
  1986年   228篇
  1985年   272篇
  1984年   283篇
  1983年   258篇
  1982年   273篇
  1981年   242篇
  1980年   256篇
  1979年   300篇
  1978年   329篇
  1977年   320篇
  1976年   404篇
  1975年   359篇
  1974年   388篇
  1973年   396篇
  1972年   369篇
  1971年   331篇
  1970年   314篇
  1969年   298篇
  1968年   253篇
  1967年   250篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Russian Journal of Electrochemistry - Metal/N-doped carbon (M/C–N) composites were prepared using the melamine-formaldehyde polymer (MFP) as a source of C–N carbon and a metal salt...  相似文献   
982.
Russian Journal of Applied Chemistry - The process of Pd(II) sorption from hydrochloric acid solutions was studied in the pH range of 0.5–5.0 in the presence of Pt(IV) and a number of...  相似文献   
983.
Membrane technology is of particular significance for the sustainable development of society owing to its potential capacity to tackle the energy shortage and environmental pollution. Membrane materials are the core part of membrane technology. Researchers have always been pursuing predictable structures of advanced membrane materials, which provides a possibility to fully unlock the potential of membranes. Covalent organic frameworks(COFs), with the advantage of controllable pore microenvironment, are considered to be promising candidates to achieve this design concept. The customizable function of COF membranes through pore engineering does well in the enhancement of selective permeability performance, which offers COF membranes with great application potentials in separation and transportation fields. In this context, COF-based membranes have been developed rapidly in recent years. Herein, we present a brief overview on the strategies developed for pore engineering of COF membranes in recent years, including skeleton engineering, pore surface engineering, host-guest chemistry and membrane fabrication. Moreover, the features of transmission or separation of molecules/ions based on COF membranes and corresponding applications are also introduced. In the last part, the challenges and prospects of the development of COF membranes are discussed.  相似文献   
984.
Russian Journal of Organic Chemistry - 2-(4-Oxo-3-arylthiazolidin-2-ylidene)acetamide derivatives were prepared by the reaction of 2-cyano-N-furan-2-ylmethyl-3-sulfanyl-3-arylaminoacrylamides with...  相似文献   
985.
Russian Chemical Bulletin - Peculiar features of the modification of Fe3O4 magnetic nanoparticles (MNPs) obtained by co-precipitation from solutions of FeII and FeIII salts (10-nm MNPs) and by the...  相似文献   
986.
Lee  V. Ya.  Miyazaki  S.  Gapurenko  O. A.  Minyaev  R. M.  Minkin  V. I.  Sekiguchi  A. 《Russian Chemical Bulletin》2021,70(11):2233-2235

(Thiatrisila)bicyclo[1.1.0]butane 1 quantitatively transformed under either photochemical or thermal conditions into the isomeric (thiatrisila)cyclobutene 2, which was isolated and fully characterized.

  相似文献   
987.
We report on experimental results on multiple action of hydrogen, deuterium, and helium plasmas produced by a plasma gun and the Globus-M tokamak on tungsten. The surface temperature in the course of irradiation is measured with a bichromatic pyrometer with a time resolution of ?1 μs. The morphology of the surface layer is investigated and X-ray structure analysis of tungsten exposed to multiple radiations by the plasma under various conditions is carried out. A slight decrease in the lattice parameter in the sample subjected to the maximal number of irradiation cycles is detected. It is shown that the morphology of the tungsten surface irradiated by the hydrogen plasma from the gun and by the deuterium plasma from the Globus-M tokamak changes (the structure becomes smoother). The characteristic depth of the layer in which impurities have been accumulated exceeds 0.5 μm. This depth was the largest for the sample exposed to 1000 shots from the gun and 2370 shots from the tokamak. It is shown that the helium jet from the plasma gun makes it possible to simulate the action of helium ions on the International Thermonuclear Experimental Reactor (ITER) diverter, producing a layer of submicrometer particles (bubbles).  相似文献   
988.
An important role of the morphology of a superconducting layer in the superconducting spin-valve effect has been established. The triplet pairing induced by the superconductor/ferromagnet proximity effect has been experimentally investigated for samples CoOx/Py1/Cu/Py2/Cu/Pb (where Py = Ni0.81Fe0.19) with a smooth superconducting layer. The optimization of the parameters of this structure has demonstrated a complete switching between the normal and superconducting states with a change in the relative orientation of magnetizations of the ferromagnetic layers from the antiparallel to orthogonal orientation. A pure triplet contribution has been observed for the sample with a permalloy layer thickness at which the superconducting spin-valve effect vanishes. A direct comparison of the experimental data with the theoretical calculation of the temperature of the transition to the superconducting state has been performed for the first time.  相似文献   
989.
The dynamics of growth and interaction of vapor bubbles in droplets of pure water and LiBr water solution on a horizontal wall were investigated in a wide superheating range. The growth rates of bubbles were determined both in a distillate droplet and in a salt solution droplet. The bubble growth rate in a pure water droplet at the final stage is somewhat lower than in pool boiling. The bubble growth rate in a salt solution is substantially lower than for pure water. Due to the bubble density maldistribution, the vapor flow density is appreciably higher at the droplet edges than on the droplet axis. Collective behavior of the bubbles possesses both stochastic character and elements of self-organization. The thermal measurements were carried out by means of high-speed video and blowup thermal imager.  相似文献   
990.
The yield and composition of conversion products are investigated in a layout that provides countersupply of reagents (brown coal, supercritical water (SCW), and O2) into a vertical tubular reactor and drain of reactants into replaceable collectors under isobaric conditions (30 MPa). The coal (gross formula CH0.96N0.01S0.002O0.31) incorporated into coal-water slurry (CWS) stabilized by starch addition (1 wt.%), was supplied through the top end of the reactor, while SCW and SCW/O2 fluids were supplied through the bottom end. Based on the results of elemental analysis of liquid products and solid residue of conversion, and mass spectrometric analysis of volatile products, we obtained gross reactions of brown coal conversion in SCW and SCW/O2 fluids. It was found that addition of O2 to SCW leads to autothermal conversion conditions and an increase in the contribution from heterogeneous reactions between carbon and water, which provides additional yield of H2 and CH4.  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