全文获取类型
收费全文 | 1946篇 |
免费 | 54篇 |
国内免费 | 4篇 |
专业分类
化学 | 1158篇 |
晶体学 | 9篇 |
力学 | 111篇 |
数学 | 342篇 |
物理学 | 384篇 |
出版年
2023年 | 16篇 |
2022年 | 31篇 |
2021年 | 64篇 |
2020年 | 38篇 |
2019年 | 40篇 |
2018年 | 35篇 |
2017年 | 32篇 |
2016年 | 69篇 |
2015年 | 62篇 |
2014年 | 54篇 |
2013年 | 97篇 |
2012年 | 104篇 |
2011年 | 156篇 |
2010年 | 62篇 |
2009年 | 64篇 |
2008年 | 118篇 |
2007年 | 112篇 |
2006年 | 110篇 |
2005年 | 85篇 |
2004年 | 74篇 |
2003年 | 61篇 |
2002年 | 72篇 |
2001年 | 24篇 |
2000年 | 16篇 |
1999年 | 22篇 |
1998年 | 16篇 |
1997年 | 23篇 |
1996年 | 37篇 |
1995年 | 22篇 |
1994年 | 16篇 |
1993年 | 23篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 9篇 |
1987年 | 22篇 |
1986年 | 9篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 14篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1975年 | 6篇 |
1972年 | 4篇 |
排序方式: 共有2004条查询结果,搜索用时 15 毫秒
21.
Liposomes have been widely used as cellular and bioparticle mimics due to their lipid bilayer structure and relative ease of production and manipulation. Such biocolloids are frequently characterized by capillary electrophoresis (CE), which promises a wealth of information about such properties as surface charge, composition, and rigidity. The applicability of this information is somewhat limited, however, since it is interpreted with colloidal theories that do not account for the unique properties of biocolloids. In this work, the effects of deformability, mobile surface charges, intrinsic polarizability, and uneven surface charge distributions are incorporated into colloidal theories in order to better model the electrophoretic behaviors of liposomes. 相似文献
22.
Fabbrizzi L Foti F Licchelli M Maccarini PM Sacchi D Zema M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(21):4965-4972
A cyclam-like macrocycle has been synthesized with a pendant arm containing a dansylamide group. In the corresponding nickel(II) complex, binding of the pendant arm to the metal is pH controlled. In particular, at pH 4.3, the sulfonamide group deprotonates and coordinates the NiII center, giving rise to a complex of trigonal bipyramidal stereochemistry, as shown by X-ray diffraction studies performed on the crystalline complex salt. At pH 7.5, an OH- ion binds the metal and a six-coordinate species forms. The binding-detachment of the pendant arm to/from the NiII center is signaled by changes in the emission properties of the dansyl subunit in the side chain; the fluorescence of this side chain is high when the pendant arm is not coordinated and low when the sulfonamide group is bound to the metal. The system investigated represents the prototype of a light-emitting molecular machine, driven by a pH change. 相似文献
23.
Cosper MM Jameson GN Davydov R Eidsness MK Hoffman BM Huynh BH Johnson MK 《Journal of the American Chemical Society》2002,124(47):14006-14007
The combination of resonance Raman, electron paramagnetic resonance and M?ssbauer spectroscopies has been used to investigate the effect of S-adenosyl-l-methionine (SAM) on the spectroscopic properties of the [4Fe-4S]2+ cluster in biotin synthase. The results indicate that SAM interacts directly at a unique iron site of the [4Fe-4S]2+ cluster in BioB and support the hypothesis of a common inner-sphere mechanism for the reductive cleavage of SAM in the radical SAM family of Fe-S enzymes. 相似文献
24.
Paolesse R Nardis S Venanzi M Mastroianni M Russo M Fronczek FR Vicente MG 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(5):1192-1197
5,10,15-Triphenylcorrole (1) reacts with the Vilsmeier reagent (POCl(3)/DMF) to give the corresponding 3-formyl derivative 3 as the major product. The regioselectivity of the reaction was proven by X-ray crystallography and only traces of the 2-formyl isomer were observed. A more polar product is also observed and this compound becomes the major product when an excess of DMF is used for the preparation of the Vilsmeier reagent, while the formation of the 3-formyl isomer is almost completely suppressed. X-ray crystallography allowed us to identify this compound as the fully substituted N-ethane bridged derivative 4, formed from the attack of the Vilsmeier reagent at the inner core of the macrocycle. This compound is unique among porphyrinoid macrocycles, and further confirms the peculiarity of corrole chemistry. 相似文献
25.
Domenico Spinelli Anlonino Corrao Vincenzo Frenna Nicol
Vivona Michele Ruccia Giuseppe Cusmano 《Journal of heterocyclic chemistry》1976,13(2):357-360
The rates of the mononuclear heterocyclic rearrangement of the phenylhydrazone of 3-benzoyl-5-phenyl-1,2,4-oxadiazole (1) into 2,5-diphenyl-4-benzoylamino-1,2,3-triazole (II) have heen measured in dioxane/water (50:50, v:v) in the range of pS+ 3.8–12.2 at various temperatures and the activation parameters determined. On the basis of the results obtained, we present evidence for the occurrence of two different types of reaction: the first, base-catalyzed; the second, pS+ -independent. In the base-catalyzed range the catalysis is of the general type. 相似文献
26.
BIT Numerical Mathematics - In this paper we propose a method to compute the solution to the fractional diffusion equation on directed networks, which can be expressed in terms of the graph... 相似文献
27.
28.
29.
30.
Kizek R Masarik M Kramer KJ Potesil D Bailey M Howard JA Klejdus B Mikelova R Adam V Trnkova L Jelen F 《Analytical and bioanalytical chemistry》2005,381(6):1167-1178
The electroanalytical determination of avidin in solution, in a carbon paste, and in a transgenic maize extract was performed in acidic medium at a carbon paste electrode (CPE). The oxidative voltammetric signal resulting from the presence of tyrosine and tryptophan in avidin was observed using square-wave voltammetry. The process could be used to determine avidin concentrations up to 3 fM (100 amol in 3 l drop) in solution, 700 fM (174 fmol in 250 l solution) in an avidin-modified electrode, and 174 nM in a maize seed extract. In the case of the avidin-modified CPE, several parameters were studied in order to optimize the measurements, such as electrode accumulation time, composition of the avidin-modified CPE, and the elution time of avidin. In addition, the avidin-modified electrode was used to detect biotin in solution (the detection limit was 7.6 pmol in a 6 l drop) and to detect biotin in a pharmaceutical drug after various solvent extraction procedures. Comparable studies for the detection of biotin were developed using HPLC with diode array detection (HPLC-DAD) and flow injection analysis with electrochemical detection, which allowed biotin to be detected at levels as low as 614 pM and 6.6 nM, respectively. The effects of applied potential, acetonitrile content, and flow rate of the mobile phase on the FIA-ED signal were also studied. 相似文献