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   193篇
  免费   1篇
化学   82篇
晶体学   2篇
数学   44篇
物理学   66篇
  2022年   2篇
  2017年   3篇
  2016年   2篇
  2014年   4篇
  2013年   8篇
  2012年   6篇
  2011年   6篇
  2010年   4篇
  2008年   5篇
  2007年   5篇
  2006年   16篇
  2005年   12篇
  2004年   12篇
  2003年   3篇
  2002年   5篇
  2001年   2篇
  2000年   7篇
  1999年   4篇
  1998年   3篇
  1996年   4篇
  1995年   2篇
  1994年   2篇
  1993年   3篇
  1992年   4篇
  1983年   2篇
  1982年   2篇
  1979年   2篇
  1977年   2篇
  1975年   4篇
  1973年   2篇
  1970年   3篇
  1958年   2篇
  1944年   2篇
  1934年   2篇
  1931年   2篇
  1930年   2篇
  1924年   2篇
  1923年   2篇
  1916年   2篇
  1915年   1篇
  1914年   3篇
  1913年   1篇
  1912年   1篇
  1907年   2篇
  1906年   1篇
  1900年   1篇
  1894年   1篇
  1892年   1篇
  1890年   2篇
  1889年   2篇
排序方式: 共有194条查询结果,搜索用时 15 毫秒
31.
We present a construction of bosons from fermions in any space dimension. In three dimensions, photons can be constructed from neutrinos, and posses the correct P, C, T and rotational properties. A new massless particle is required, identical to the photon except that it is even under charge conjugations. In a special sense, a photon is 78 of a neutrino. The inverse construction, neutrinos from these massless bosons, suggests that none of these is truly fundamental.  相似文献   
32.
We show that generalized approximation spaces can be used to prove stability and convergence of projection methods for certain types of operator equations in which unbounded operators occur. Besides the convergence, we also get orders of convergence by this approach, even in case of non-uniformly bounded projections. We give an example in which weighted uniform convergence of the collocation method for an easy Cauchy singular integral equation is studied.  相似文献   
33.
34.
Among the members of a family of diastereoisomeric pentopyranosyl‐(4′→2′)‐oligonucleotide systems derived from D ‐ribose, D ‐xylose, L ‐lyxose, and L ‐arabinose, the α‐arabinopyranosyl system shows by far the strongest Watson? Crick base pairing. The system is, in fact, one of the strongest oligonucleotide‐type base‐pairing systems known. It undergoes efficient cross‐pairing with all the other members of the pentopyranosyl family, but not with RNA and DNA. The paper describes the synthesis and pairing of the properties of α‐L ‐arabinopyranosyl‐(4′→2′)‐oligonucleotides.  相似文献   
35.
A number of carboxylate anions spanning a mass range of 87-253 amu (pyruvate, oxalate, malonate, maleate, succinate, malate, tartarate, glutarate, adipate, phthalate, citrate, gluconate, 1,2,4-benzenetricarboxylate, and 1,2,4,5-benzenetetracarboxylate) were investigated using electrospray ionization ion mobility spectrometry. Measured ion mobilities demonstrated a high correlation between mass and mobility in both N2 and CO2 drift gases. Such a strong mass-mobility correlation among structurally dissimilar ions suggests that the carboxylate functional group that these ions have in common is the source of the correlation. Computational analysis was performed to determine the most stable conformation of the studied carboxylate anions in the gas phase under the current experimental conditions. This analysis indicated that the most stable conformations for multicarboxylate anions included intramolecular hydrogen-bonded ring structures formed between the carboxylate group and the neutral carboxyl group. The carboxylate anions that form ring confirmations generally show higher ion mobility values than those that form extended conformations. This is the first observation of intramolecular hydrogen-bonded ring conformation of carboxylate anions in the gas phase at atmospheric pressure.  相似文献   
36.
The dicationic Os(II) complex [Os(bpy)(PPh(3))(2)(CO)(H(2))](2+) has been prepared as the triflate salt. The presence of a bound dihydrogen ligand is indicated by a short T(1) minimum value consistent with an H-H distance of 1.05 ?. In the partially deuterated derivative J(HD) = 25.5 Hz was observed. By comparison to other structurally characterized complexes, the observed H-D coupling is most consistent with a H-H distance greater than 1 ?, which requires that the bound H(2) ligand be in the slow rotation regime. The dicationic complex is a strong acid, indicating that the bound H(2) is substantially activated toward heterolytic cleavage. The H(2) ligand is tightly bound to the metal center, and does not undergo exchange with D(2) over the course of several weeks at room temperature. A related dicationic Os(II) complex, [Os(bpy)(2)(CO)(H(2))](2+), has also been prepared. A short T(1) minimum value and a J(HD) value of 29.0 Hz in the partially deuterated derivative is most consistent with a H-H distance of 0.99 ?. The bound H(2) ligand of this complex is significantly less activated toward heterolytic cleavage and is stable in solution for less than a day at room temperature.  相似文献   
37.
38.
Literatur     
Harries  C.  Hofmann  Fritz  Ditmar  R.  Backer  H. J.  Stark  J.  Ruggli  P.  Nierenstein  M.  Donath  E.  Indra  A.  Eisenlohr  F.  Pitaval  M. R.  Hoffmann  F.  Danneel  H.  Meyer  J.  Fischer  Franz  Rinne  F.  Block  W.  Riemann  C.  Buchner  G.  Hinneberg  P.  v. Meyer  E.  Engler  C.  Wöhler  L.  Wallach  O.  Luther  R.  Nernst  W.  Blanc  M. Le  Kossel  A.  Kellner  O.  Immendorff  H.  Witt  O. N. 《Analytical and bioanalytical chemistry》1913,52(10-11):664-668
Analytical and Bioanalytical Chemistry -  相似文献   
39.
40.
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