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991.
用共振拉曼光谱研究电子激发态铜卟啉与DNA的相互作用 总被引:1,自引:0,他引:1
用共振拉曼光谱研究电子激发态铜卟啉与DNA的相互作用赵晓杰,江山,陆冬生,陆琳,毛慈波,安承武,范永昌,李再光(华中理工大学激光技术国家重点实验室武汉,430074)周翔,黄素秋(武汉大学化学系)关键词水溶性卟啉,受激复合物,DNA,共振拉曼光谱在卟... 相似文献
992.
The conformation of an unusual slipped loop DNA structure exhibited by the sequence d(GAATTCCCGAATTC)2 is determined using a combination of geometrical and molecular mechanics methods. This sequence is known to form a B-DNA-like
duplex with the central non-complementary cytosines extruded into single stranded loop regions. The unusual feature is that
the interior guanine does not pair with the cytosine across, instead, it pairs with the cytosine upstream by skipping two
cytosines, leading to a slipped loop DNA structure with the loops staggered by two base pairs. The two loops, despite being
very small, can fold across minor or major groove symmetrically or asymmetrically disposed, with one of the loop bases partially
blocking the major or minor groove. Most interestingly, for certain conformations, the loop bases approach one another at
close proximity so as to engage even in base pairing as well as base stacking interactions across the major groove. While
such pairing and stacking are common in the tertiary folds of RNA, this is the first time that such an interaction is visualized
in a DNA. This observation demonstrates that a W-C pair can readily be accomplished in a typical slipped loop structure postulated
for DNA. Such tertiary loop interaction may prevent access to regulatory proteins across the major groove of the duplex DNA,
thus providing a structure-function relation for the occurrence of slipped loop structure in DNA.
Contribution no. 839 from this department 相似文献
993.
用普通差速离心分离了甘蓝型油菜(Brassica napus)九二13系的叶绿体,并以苯酚、氯仿及RNase处理,纯化了叶绿体DNA.经BamHⅠ,EcoRⅠ,HindⅢ,SalⅠ与SmaⅠ五种限制酶酶解,电泳分析,估算出该环状叶绿体DNA分子周长约为140.5千碱基对(kbp),即分子量约92.7×10~6道尔顿(daltion).以质粒pBR325为载体,将叶绿体DNA的BamHⅠ酶解片段,引入大肠杆菌中克隆,得到了三个重组体. 相似文献
994.
A density functional theory (DFT) study aimed at understanding structure–reactivity relationships in the oxidized metabolites of cyclopenta‐fused polycyclic aromatic hydrocarbons (CP‐PAHs) is reported. Epoxidation at various positions was examined in order to identify the most stable epoxide in each class of CP‐PAHs. Relative energies of the carbocations resulting from O‐protonation and epoxide ring opening were analyzed and compared, taking into account the available biological activity data on these compounds. Geometrical, electronic, and conformational issues were considered. Charge delocalization modes in the resulting carbocations were deduced via the natural population analysis (NPA)‐derived changes in charges. Computational results pointed to the importance of the unsaturated cyclopenta ring on the reactivity of these compounds. The reported bioactivity of this highly mutagenic/carcinogenic family of PAHs was observed to parallel their relative carbocation stabilities. A different behavior was observed in crowded non‐planar structures possessing a distorted aromatic system. A covalent adduct formed between a CP‐PAH epoxide and a purine base was computed inside a DNA fragment employing the ONIOM method. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
995.
R. Stan Brown Zhong‐Lin Lu C. Tony Liu Wing Yin Tsang David R. Edwards Alexei A. Neverov 《Journal of Physical Organic Chemistry》2010,23(1):1-15
Phosphodiesters are notoriously hydrolytically inert compounds that are demonstrated to have large accelerations of P‐OR cleavage promoted by transition and lanthanide metal ions in methanol and ethanol media. This review commentary describes recent findings of how a simple mononuclear and a dinuclear Zn(II) complex promote the cleavage of a series of RNA models and DNA models in alcohol media. The discussion centers on the analysis of the mechanisms of cleavage, energetics of the catalytic process, on recent findings of electrophilic assistance of leaving group departure, and the observation of a rapid hydrolytic reaction of a DNA model promoted by the dinuclear Zn(II) complex in ethanol containing less than 2% water. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
996.
997.
Mass spectrometry (MS) is extensively used for the identification and sequencing of nucleic acids but has so far seen limited
use for characterization of their higher order structures. Here, we have applied a range of different tandem mass spectrometry
techniques, including electron detachment dissociation (EDD), infrared multiphoton dissociation (IRMPD), activated ion (AI)
EDD, and EDD/IRMPD MS3, in a Fourier transform ion cyclotron resonance mass spectrometer to the characterization of three isomeric 15mer DNAs with
different sequences and predicted solution-phase structures. Our goal was to explore whether their structural differences
could be directly probed with these techniques. We found that all three 15mers had higher order structures in the gas phase,
although preferred structures were predicted for only two of them in solution. Nevertheless, EDD, AI EDD, and EDD/IRMPD MS3 experiments yielded different cleavage patterns with less backbone fragmentation for the more stable solution-phase structure
than for the other two 15mers. By contrast, no major differences were observed in IRMPD, although the extent of backbone cleavage
was higher with that technique for all three 15mers. Thus, experiments utilizing the radical ion chemistry of EDD can provide
complementary structural information compared to traditional slow heating methods, such as IRMPD, for structured nucleic acids. 相似文献
998.
A comparative study of the effects of alkali metal ions Li(+), Na(+), K(+), Rb(+), and Cs(+) on the liquid crystalline organization of high-molecular-weight calf thymus DNA using polarized light microscopy was performed. Major differences in the behavior of Li(+) as compared to the other ions were found. Critical DNA concentration expected to exhibit anisotropic behavior was found to be the same for all the monovalent ions, except for Li(+). DNA initially showed cholesteric textures, which later changed to higher ordered columnar phase for all ions, with the cholesteric-columnar transition facilitated upon increasing the size of the counterion. For Li(+) ion, a nematic schlieren-like texture was formed initially, which after a few days changed to a highly stable (for more than 2 months) biphasic cholesteric-columnar arrangement. The observed differences between Li(+) and other alkali metal ions could be rationalized on the basis of the higher number of hydration water molecules of Li(+) and its complexation behavior. Highly stable DNA mesophases may find applications in the field of nanoelectronics, in designing biosensing units, and in DNA chips. 相似文献
999.
A novel protocol for the synthesis of dye-encapsulating liposomes tagged with DNA oligonucleotides at their outer surface
was developed. These liposomes were optimized for use as signal enhancement agents in lateral-flow sandwich-hybridization
assays for the detection of single-stranded RNA and DNA sequences. Liposomes were synthesized using the reverse-phase evaporation
method and tagged with oligonucleotides by adding cholesteryl-modified DNA probes to the initial lipid mixture. This resulted
in a greatly simplified protocol that provided excellent control of the probe coverage on the liposomes and cut the preparation
time from 16 hours to just 6 hours. Liposomes were prepared using probe concentrations ranging from 0.00077 to 0.152 mol%
of the total lipid, several hydrophobic and polyethylene glycol-based spacers between the cholesteryl anchor and the probe,
and liposome diameters ranging from 208 nm to 365 nm. The liposomes were characterized by dynamic light scattering, visible
spectroscopy, and fluorescence spectroscopy. Their signal enhancement functionality was compared by using them in lateral-flow
optical biosensors for the detection of single-stranded DNA sequences. In these assays, an optimal reporter probe concentration
of 0.013 mol%, liposome diameter of 315 nm, and liposome optical density of 0.4–0.6 at 532 nm were found. The spacer length
between the cholesteryl anchor and the probe showed no significant effect on the signals in the lateral-flow assays. The results
presented here provide important data for the general use of liposomes as labels in analytical assays, with specific emphasis
on nucleic acid detection via lateral flow assays. 相似文献
1000.
Dye-encapsulating unilamellar DNA oligonucleotide-tagged liposomes were prepared and characterized for use as signal-enhancing
reagents in a microtiter plate sandwich-hybridization analyses of single-stranded RNA or DNA sequences. The liposomes were
synthesized using the reversed-phase evaporation method and tagged with DNA oligonucleotides by adding cholesteryl-modified
DNA reporter probes to the initial lipid mixture. Liposomes were prepared using probe coverages of 0.0013–0.103 mol% of the
total lipid input, several hydrophobic and poly(ethylene glycol)-based spacers between the cholesteryl anchor and the probe,
and liposome diameters ranging from 200 nm to 335 nm. Their signal enhancement functionality was compared by using them in
microtiter plate sandwich-hybridization assays for the detection of single-stranded DNA sequences. In these assays, an optimal
reporter probe concentration of 0.103 mol%, a liposome diameter of 274 nm, and a phospholipid concentration of 0.3 mM were
found. The length between the cholesteryl anchor and the probe was optimal when a spacer composed of TEG+(CH2O)3 was used. Under optimal conditions, a detection limit of 0.5 nM for a truncated synthetic DNA sequence was found with a coefficient
of variation of 4.4%. A 500-fold lower limit of detection using fluorescence was found using lysed dye-encapsulating liposomes
versus a single fluorescein-labeled probe. Finally, when this method was applied to the detection of atxA RNA extracted from E.coli SG12036-pIu121 and amplified using NASBA, a minimum extracted concentration of RNA of 1.1×10−7 μg/μL was found. 相似文献