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   348篇
  免费   2篇
  国内免费   2篇
化学   141篇
晶体学   5篇
力学   9篇
数学   34篇
物理学   163篇
  2023年   3篇
  2021年   5篇
  2020年   6篇
  2019年   5篇
  2016年   2篇
  2014年   3篇
  2013年   14篇
  2012年   11篇
  2011年   17篇
  2010年   8篇
  2009年   3篇
  2008年   16篇
  2007年   11篇
  2006年   16篇
  2005年   14篇
  2004年   9篇
  2003年   9篇
  2002年   9篇
  2001年   12篇
  2000年   11篇
  1999年   4篇
  1998年   2篇
  1996年   10篇
  1995年   4篇
  1994年   7篇
  1993年   6篇
  1992年   4篇
  1991年   5篇
  1990年   13篇
  1989年   9篇
  1988年   16篇
  1987年   12篇
  1986年   6篇
  1985年   4篇
  1984年   6篇
  1983年   6篇
  1982年   2篇
  1981年   2篇
  1980年   2篇
  1977年   3篇
  1975年   4篇
  1974年   3篇
  1973年   4篇
  1972年   4篇
  1969年   4篇
  1968年   2篇
  1943年   2篇
  1932年   2篇
  1925年   2篇
  1915年   2篇
排序方式: 共有352条查询结果,搜索用时 15 毫秒
1.
Information is presented on structure, composition, and response to enzymes of corn stover related to barriers for bioconversion to ethanol. Aromatic compounds occurred in most tissue cell walls. Ferulic acid esterase treatment before cellulase treatment significantly improved dry weight loss and release of phenolic acids and sugars in most fractions over cellulase alone. Leaf fractions were considerably higher in dry weight loss and released sugars with esterase treatment, but stem pith cells gave up the most phenolic acids. Results help identify plant fractions more appropriate for coproducts and bioconversion and those more suitable as residues for soil erosion control.  相似文献   
2.
3.
4.
Backward proton and pion production is studied in ν and \(\bar v\) charged current interactions in neon. The results are compared with other experiments and theory. The complete backward proton data is compatible with protons produced by reinteractions in the nucleus. However in events with only one proton, muon variables appear correlated to those for the backward proton, as expected by the two-nucleon correlation model.  相似文献   
5.
6.
The cross section for coherent production of a single π? meson in charged current antineutrino interactions on neon nuclei has been measured in BEBC to be (175±25) 10?40 cm2/neon nucleus, averaged over the energy spectrum of the antineutrino wide band beam at the CERN SPS; this corresponds to (0.9±0.1) % of the total charged current \(\bar v_\mu \) cross section. The distributions of kinematical variables are in agreement with theoretical predictions based on the PCAC hypothesis and the meson dominance model; in particular, theQ 2 dependence is well described by a propagator containing a massm=(1.35±0.18) GeV. The absolute value of the cross section is also in agreement with the model. This analysis thus provides a test of the PCAC hypothesis in the antineutrino energy range 5–150 GeV.  相似文献   
7.
Controlled drug delivery remains a research focus for public health to enhance patient compliance, drug efficiency and reduce the side effects of drugs. Pectin, an edible plant polysaccharide, has been shown to be useful for the construction of drug delivery systems for specific drug delivery. Several pectin derived formulations have been developed in our laboratory and tested in vitro, ex vivo, and in vivo for the ability to deliver bioactive substances for therapeutic purposes in the context of interactions with living tissues. Pectin derivatives carrying primary amine groups were more mucoadhesive and have shown potential in nasal drug delivery and other mucosal drug delivery. Pectin derivatives with highly esterified galacturonic acid residues are more hydrophobic and able to sustain the release of incorporated fragrances for a prolonged duration. Less esterified pectin derivatives are able to penetrate deeper into the skin and may be useful in aromatherapy formulations. Pectin, in combination with zein, a corn protein, forms hydrogel beads. The bound zein restricts bead swelling and retains the porosity of the beads; the pectin networks shield the zein from protease attack. The complex beads are ideal vehicles for colon-specific drug delivery. Studies presented in this paper indicate the flexibility and possibility to tailor pectin macromolecules into a variety of drug delivery systems to meet different clinical requirements. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture.  相似文献   
8.
Hicks JD  Flamme EM  Roush WR 《Organic letters》2005,7(24):5509-5512
[reaction: see text] A synthesis of the C(43)-C(67) fragment of amphidinol 3 (AM3) has been accomplished by a route that features the use of a double allylboration reaction for synthesis of 1,5-diol 4b, which serves as a precursor to dihydropyran 11.  相似文献   
9.
The MNDO scheme has been reparametrized for hydrocarbons using both molecular binding energies and heats of formation at 0 K as experimental reference data. Compared with MNDO, there are only minor changes in the optimized parameters, and the results are essentially of the same accuracy. These tests justify the use of heats of formation at 298 K as reference data in the original MNDO parametrization.  相似文献   
10.
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