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   577篇
  免费   13篇
  国内免费   4篇
化学   381篇
晶体学   4篇
力学   10篇
数学   111篇
物理学   88篇
  2023年   4篇
  2022年   5篇
  2021年   21篇
  2020年   15篇
  2019年   19篇
  2018年   17篇
  2017年   24篇
  2016年   28篇
  2015年   24篇
  2014年   23篇
  2013年   32篇
  2012年   41篇
  2011年   48篇
  2010年   39篇
  2009年   19篇
  2008年   38篇
  2007年   34篇
  2006年   35篇
  2005年   25篇
  2004年   17篇
  2003年   17篇
  2002年   16篇
  2001年   7篇
  2000年   11篇
  1999年   8篇
  1998年   2篇
  1997年   2篇
  1996年   6篇
  1995年   2篇
  1994年   2篇
  1993年   3篇
  1992年   2篇
  1991年   1篇
  1988年   1篇
  1985年   1篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1975年   2篇
排序方式: 共有594条查询结果,搜索用时 31 毫秒
91.
Abstract This study hypothesized that success rate assessment of vascular targeted photodynamic therapy (VTP) of solid tumors 24 h post-treatment may allow prompt administration of a second treatment in case of failure, increasing the overall success rate. Here, we show that treatment of luciferase transfected CT26-luc mouse colon carcinoma tumors in BALB/c mice by VTP with WST11 (a Pd-bacteriochlorophyll-based photosensitizer) allows fast assessment of treatment success 24 h post-treatment, using bioluminescence imaging (BLI). WST11-VTP was found to abolish luciferin bioluminescence in the treated tumors resulting in two types of responses. One, comprising 75% of the mice, signified successful outcome, presenting neither BLI signal nor tumor regrowth (24 h-90 days post-VTP). The second (the remaining 25% of the mice) signified treatment failure, presenting various levels of BLI signal with subsequent tumor regrowth (24 h-90 days). Consequently, the mice that failed the first treatment were treated again. We show that treatment success rate in both VTP sessions was identical and that the cumulative success rate of the treatment increased from 75% to over 90%. These results therefore, present a fast method of assessing VTP outcome and support the feasibility of successive multiple treatments with these sensitizers in the clinical arena. The presented methodology can also be helpful in future preclinical studies, and expedite the development of VTP drugs.  相似文献   
92.
Perfluoro-2-ethyl-2-phenylbenzocyclobutenone heated with SbF5 at 70 °C and then treated with water, forms perfluoro-3-ethyl-3-phenylphthalide. In contrast to this, heating of perfluoro-2,2-diethylbenzo-cyclobutenone with SbF5 at 70 °C gives, after treatment of the reaction mixture with water, perfluoro-2-(pent-2-en-3-yl)benzoic acid. When the reaction temperature is raised to 125 °C, a solution of a salt of perfluoro-4-ethyl-3-methylisochromenyl cation is obtained. Hydrolysis of the solution of the salt gives perfluoro-4-ethyl-3-methylisochromen-1-one.  相似文献   
93.
1,3-Dipolar cycloaddition of C-aryl,N-aryl (or N-methyl) nitrones with a number of 1,2-diphenylcyclopropenes substituted at the C(3) position occurs with the formation of expected "normal" cycloadducts (with N-methylnitrones) and products of their subsequent transformations. Among them are corresponding alpha-acetophenyl aziridines and tetra (or penta) -arylpyrroles. Aziridines and the normal cycloadducts can be also thermally converted to such arylpyrroles with moderate to good yields. Substitution at the C(3( position of cyclopropenes by an electron acceptor group decreases the reactivity of cyclopropenes.  相似文献   
94.
The main theorem of this note is the following refinement of the well-known Lelong-Bremermann Lemma:

Let be a continuous plurisubharmonic function on a Stein manifold of dimension Then there exists an integer , natural numbers , and analytic mappings such that the sequence of functions

converges to uniformly on each compact subset of .

In the case when is a domain in the complex plane, it is shown that one can take in the theorem above (Section 3); on the other hand, for -circular plurisubharmonic functions in the statement of this theorem is true with (Section 4). The last section contains some remarks and open questions.

  相似文献   

95.
Understanding and controlling the kinetics of O2 reduction in the presence of Li+‐containing aprotic solvents, to either Li+‐O2 by one‐electron reduction or Li2O2 by two‐electron reduction, is instrumental to enhance the discharge voltage and capacity of aprotic Li‐O2 batteries. Standard potentials of O2/Li+‐O2 and O2/O2 were experimentally measured and computed using a mixed cluster‐continuum model of ion solvation. Increasing combined solvation of Li+ and O2 was found to lower the coupling of Li+‐O2 and the difference between O2/Li+‐O2 and O2/O2 potentials. The solvation energy of Li+ trended with donor number (DN), and varied greater than that of O2 ions, which correlated with acceptor number (AN), explaining a previously reported correlation between Li+‐O2 solubility and DN. These results highlight the importance of the interplay between ion–solvent and ion–ion interactions for manipulating the energetics of intermediate species produced in aprotic metal–oxygen batteries.  相似文献   
96.
A reversed‐phase ion‐pair high‐performance liquid chromatography procedure was developed for the separation of polyprenyl diphosphate oligomer homologues obtained chemically from plant polyprenols. Tetrabutylammonium phosphate was used as the ion‐pair reagent, and the dependence of the separation quality on pH of ion‐pair reagent was investigated for the first time. The procedure is applicable for the control of commercial available polyprenyl monophosphates (the active components of veterinary drugs Phosprenyl and Gamapren) for the possible presence of polyprenyl diphosphate byproducts.  相似文献   
97.
The fact that molecular crystals exist as different polymorphic modifications and the identification of as many polymorphs as possible are important considerations for the pharmaceutic industry. The molecule of N‐benzyl‐4‐hydroxy‐1‐methyl‐2,2‐dioxo‐1H‐2λ6,1‐benzothiazine‐3‐carboxamide, C17H16N2O4S, does not contain a stereogenic atom, but intramolecular hydrogen‐bonding interactions engender enantiomeric chiral conformations as a labile racemic mixture. The title compound crystallized in a solvent‐dependent single chiral conformation within one of two conformationally polymorphic P212121 orthorhombic chiral crystals (denoted forms A and B). Each of these pseudo‐enantiomorphic crystals contains one of two pseudo‐enantiomeric diastereomers. Form A was obtained from methylene chloride and form B can be crystallized from N,N‐dimethylformamide, ethanol, ethyl acetate or xylene. Pharmacological studies with solid–particulate suspensions have shown that crystalline form A exhibits an almost fourfold higher antinociceptive activity compared to form B.  相似文献   
98.
A novel, nondamaging method for experimental characterization of the formation and propagation of high-resistivity zones in CE, based on the measurement of time-dependent Joule heating on the outer capillary surface is proposed. The method detects propagation of resistive regions in capillaries in real time and allows the estimation of their velocity and resistance. The presented experimental data are in agreement with the results of the computer simulation as well as with previous data on the subject. The proposed method is useful for the development of new polymers as well as for the refinement and optimization of new CE protocols.  相似文献   
99.
Let V be a vector space over a field or skew field F, and let U be its subspace. We study the canonical form problem for bilinear or sesquilinear forms
  相似文献   
100.
Characterizations via convolutions with smooth compactly supported kernels and other distinguished properties of the weighted Besov–Lipschitz and Triebel–Lizorkin spaces on ℝn with weights that are locally in Ap but may grow or decrease exponentially at infinity are investigated. Square–function characterizations of the weighted Lp and Hardy spaces with the above class of weights are also obtained. A certain local variant of the Calderón reproducing formula is constructed and widely used in the proofs.  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