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   11168篇
  免费   237篇
  国内免费   11篇
化学   6385篇
晶体学   144篇
力学   163篇
数学   1671篇
物理学   3053篇
  2021年   100篇
  2020年   129篇
  2019年   141篇
  2018年   187篇
  2017年   210篇
  2016年   300篇
  2015年   287篇
  2014年   303篇
  2013年   637篇
  2012年   468篇
  2011年   608篇
  2010年   413篇
  2009年   357篇
  2008年   523篇
  2007年   413篇
  2006年   440篇
  2005年   314篇
  2004年   318篇
  2003年   257篇
  2002年   252篇
  2001年   185篇
  2000年   202篇
  1999年   181篇
  1998年   131篇
  1997年   111篇
  1996年   147篇
  1995年   132篇
  1994年   137篇
  1993年   126篇
  1992年   117篇
  1991年   102篇
  1990年   112篇
  1989年   101篇
  1988年   82篇
  1986年   90篇
  1985年   134篇
  1984年   133篇
  1983年   109篇
  1982年   125篇
  1981年   105篇
  1980年   107篇
  1979年   99篇
  1978年   115篇
  1977年   105篇
  1976年   128篇
  1975年   109篇
  1974年   89篇
  1973年   82篇
  1972年   83篇
  1968年   81篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
941.
Graft copolymers with cellulose diacetate (CDA) backbone and both the poly(ε‐caprolactone) and polystyrene, or poly(butyl acrylate) or PMMA grafts were prepared by two‐step process. First, ε‐caprolactone (CL) was polymerized by ring‐opening polymerization (ROP) initiated with CDA, partly funcionalized with 2‐bromo‐isobutyryl groups (degree of functionalization was 0.5). The p(CDA‐g‐CL) copolymers were used in the second step as polyfunctional macroinitiators of ATRP of the vinyl monomer, giving densely grafted copolymers with polyester and PSt, or PBuA, or PMMA grafts. The prepared copolymers were characterized by SEC, some of them also by FTIR spectroscopy and atomic force microscopy (AFM). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 564–573, 2008  相似文献   
942.
JPC – Journal of Planar Chromatography – Modern TLC - The accumulation of hydrogen peroxide (H2O2) is an early and crucial step in paclitaxel-induced cancer cell death before commitment...  相似文献   
943.
The main result of the present note states that it is consistent with the ZFC axioms of set theory (relying on Martin's Maximum MM axiom), that every Asplund space of density character ω1 has a renorming with the Mazur intersection property. Combined with the previous result of Jiménez and Moreno (based upon the work of Kunen under the continuum hypothesis) we obtain that the MIP renormability of Asplund spaces of density ω1 is undecidable in ZFC.  相似文献   
944.
945.
946.
The ray tracing codes for flat, cylindrically bent (Johann horizontal focusing and von Hamos vertical focusing geometry), elliptically and spherically bent crystal spectrometers were developed. The codes, extended by introducing the two-dimensional source and the real shape of single crystal diffraction pattern in dependence on the radius of curvature, contribute to a proper choice of experimental configuration in x-ray plasma diagnostics. A method of ray tracing the von Hamos spectrometer is presented in detail. The use of the ray tracing code to the optimization of the spectroscopic scheme is demonstrated on the analysis of gas-puff z-pinch experiment.  相似文献   
947.
948.
Two versions of an amperometric detector with a copper working electrode have been constructed and tested for high-performance liquid chromatography (HPLC). The performance of the detectors was studied using selected amino acids. The dependence of the detector response on the mobile phase flow-rate was studied in the range common in both macro- and microcolumn HPLC (5 microliter/min to 1.0 ml/min). It has been found that the detection sensitivity generally increases with decreasing flow-rate, i.e., the detector response is governed by the rate of the complexation reaction between the cupric ions and the solutes. This fact makes amperometric detection with a copper electrode especially useful for microcolumn separations. For all 20 amino acids studied, calibration curve parameters and detection limits have been determined; the latter vary from 0.4 to 18 ng in the injected volume. The amino acids can also be sensitively detected in a medium of 0.1-1.0 M ammonia, which is promising for the use of strong anion exchangers in amino acid separations. Choline can also be detected at a copper electrode, with a detection limit of 40 ng. An HPLC method with amperometric detection at a copper electrode has been developed for the determination of lysine, methionine and choline in fodder biofactors.  相似文献   
949.
The rapid‐solidification processing (by a cooling rate of 105–106 K/s) was used for the preparation of deeply undercooled cryolite/alumina (Na3AlF6/Al2O3) melts. We found a mass of nanotubes on the surface of these undercooled melts. The nanotubes were preferentially located on the defect places of the surface with the following approximate dimensions: base≈100×100 nm, length≈1000 nm. The solidified samples with the nanotubes on the surface were analyzed by scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), X‐ray diffraction (XRD), and infrared spectroscopy (IR).  相似文献   
950.
 Carbonyl compounds of the type XPhCOR (R = H, Me, Ph; X = H, Me, Cl, Br) are prepared in high yields by reaction of the corresponding benzylic alcohols XPhCHOHR with KNa4 [Ag(HIO6)2]×12H2O in alkaline solution. This method allows the selective oxidation of benzylic alcohols in compounds containing other types of alcoholic functional groups.  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