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31.
Mohamed R. Mahran Wafaa M. Abdou Maha D. Khidre 《Monatshefte für Chemie / Chemical Monthly》1990,121(1):51-58
Summary The reaction of furil (1) with trialkyl phosphites2 yielded caged phosphorane derivatives of types3a-c. Dry hydrogen chloride gas converted3a-c into the respectivea-hydroxyvinyl-phosphates8a-c which are equally produced by reacting furil with the appropriate dialkyl phosphite7. The reaction of furil with ylide-phosphoranes10 proceeded according to the Wittig reaction mechanism to give the respective ethylenes11a-c. The new compounds have been characterized by their spectroscopic data (IR, PMR,31P-NMR, MS) and elementary analyses.Dedicated to Prof. M. Sidky on the occasion of his 60th birthday 相似文献
32.
JieLiang Bi-qianLiu 《高分子科学》2005,(1):83-92
Plasma-induced surface graft copolymerization of acrylic acid on polypropylene non-woven fabric (PP-g-AA) and polypropylene membrane were reported. The extents of grafting were controlled by the plasma and polymerization condition. Hexadecyltrimethyl ammonium bromide was then coupled with the carboxyl group of PP-g-AA to obtain a polyion complex (PIC). At last, CF4 plasma was used to give PICs hydrophobic property. The moisture regain and water-repellency of the processed PICs was investigated. The surfaces were characterized using ATR FT-IR and XPS. The result indicates that the products have very high ability to adsorb moisture, even better than cotton fiber. At the same time, the products show excellent hydrophobic property, which can‘t be wetted by those reagents whose surface tensions were higher than 327mN/m. 相似文献
33.
The concentration dependence of the apparent molar volumes of lithium halides (and electrolytes in general) in alcohols (and
solvents permitting association in general) is, in the first instance, due to changes in the degree of association and to
the inherent difference between the apparent molar volumes of the ions and of the ion pairs. Previous publications on the
molar volumes of electrolytes in organic solvents, disregarding altogether ion pairing, appear to be incorrect. Data from
the literature for lithium chloride and lithium bromide in normal primary alcohols and several branched alcohols from C1 to C8 and data from our laboratory for lithium halides in 1-hexanol and 2-ethyl-1-hexanol served for the determination of φ
V
and φ
E
. Electrical and structural contributions to the values of these functions for the ions and for the ion pairs are discussed. 相似文献
34.
Three types of dual-frequency oscillations in KBrO3-galactose-acetone-MnSO4-H2SO4 have been observed in a batch reactor depending on the initial concentration of H2SO4 or Br-. Similar phenomena were also observed when galactose was replaced by other aldosugars such as glucose, arabi-nose, lactose and maltose. However no dual-frequency oscillation has been found when ketosugar like fructose was used instead of galactose as the substrate. The roles of acidity, bromide ion and acetone in dual-frequency oscillations have been analyzed. The mechanism of dual-frequency oscillations has been discussed. 相似文献
35.
We use agarose gel electrophoresis to characterize how the monovalent catioinic surfactant cetyltrimethylammonium bromide (CTAB) compacts double-stranded DNA, which is detected as a reduction in electrophoretic DNA velocity. The velocity reaches a plateau at a ratio R = 1.8 of CTAB to DNA-phosphate charges, i.e., above the neutralization point, and the complexes retain a net negative charge at least up to R = 200. Condensation experiments on a mixture of two DNA sizes show that the complexes formed contain only one condensed DNA molecule each. These CTAB-DNA globules were further characterized by time-resolved measurements of their velocity inside the gel, which showed that CTAB does not dissociate during the migration but possibly upon entry into the gel. Using the Ogston-model for electrophoresis of spherical particles, the measured in-gel velocity of the globule is quantitatively consistent with CTAB having two opposite effects, reduction of both the electrophoretic charge and DNA coil size. In the case of CTAB the two effects nearly cancel, which can explain why opposite velocity shifts (globule faster than uncomplexed DNA) have been observed with some catioinic condensation agents. Dissociation of the complexes by addition of anionic surfactants was also studied. The DNA release from the globule was complete at a mixing ratio between anionic and cationic surfactants equal to 1, in agreement with equilibrium studies. Circular DNA retained its supercoiling, and this demonstrates a lack of DNA nicking in the compaction-release cycle which is important in DNA transfection and purification applications. 相似文献
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Summary A theoretical treatment is presented which considers differences between the composition of the mobile phase and solvents
that are incorporated into the bonded phase via preferential sorption. Equations are derived and used to analyze retention
data for various homologs chromatographed under reversed-phase conditions using alkyl bonded phases and combinations of water-methanol,
water-acetonitrile and watertetrahydrofuran as mobile phases. In the case of water-methanol the surface phase and bulk mobile
phase compositions are similar. However, significant differences in composition between the two phases are observed when binary
combinations of water-acetonitrile and water-tetrahydrofuran are used as the cluents. 相似文献
40.
Interactions of anionic surfactant sodium dodecyl sulphate (SDS) with vesicles formed by synthetic dialkyldimethylammonium
bromides i.e. didodecyldimethylammonium bromide (DDAB), ditetradecyldimethylammonium bromide (DTAB), dihexadecyldimethylammonium
bromide (DHAB) have been examined by using differential scanning microcalorimetry and electron transmission microscopy. The
temperatures and standard enthalpies characterising gel to liquid-crystal transitions increase significantly with increase
of SDS concentration for all investigated systems. It means that incorporation of SDS monomers in these vesicular bilayers
significantly stabilises their gel states. Moreover, in case of DDAB and DTAB vesicle systems added SDS limits kinetic features
of recorded isobaric heat capacity dependencies on temperature observed earlier for the pure vesicular solutions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献