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81.
[reaction: see text] The tricyclic indeno-tetrahydropyridine core of haouamine A, containing five of the seven rings of the natural product, was constructed by a simple, concise route that features an acid-catalyzed Friedel-Crafts ring closure. 相似文献
82.
Fabrication of polystyrene hollow microspheres as laser fusion targets by optimized density-matched emulsion technique and characterization 总被引:3,自引:0,他引:3
Inertial confinement fusion, frequently referred to as ICF, inertial fusion, or laser fusion, is a means of producing energy
by imploding small hollow microspheres containing thermonuclear fusion fuel. Polymer microspheres, which are used as fuel
containers, can be produced by solution-based micro-encapsulation technique better known as density-matched emulsion technique. The specifications of these microspheres are very rigorous, and various aspects of the emulsion hydrodynamics associated
with their production are important in controlling the final product. This paper describes about the optimization of various
parameters associated with density-matched emulsion method in order to improve the surface smoothness, wall thickness uniformity
and sphericity of hollow polymer microspheres. These polymer microshells have been successfully fabricated in our lab, with
3–30 μm wall thickness and 50–1600 μm diameters. The sphericity and wall thickness uniformity are better than 99%. Elimination
of vacuoles and high yield rate has been achieved by adopting the step-wise heating of W1/O/W2 emulsion for solvent removal. 相似文献
83.
The conventional type of magnetic well is formed by superposition of two types of magnetic field, axial bumpy field and radial
multipole field. It is used to contain plasma that consists of neutrals, ions and electrons. These particles are in constant
motion in the well and energetic electrons create plasma by violent collisions with neutrals and ions. The confined electrons
are constantly heated by ECR technique in the presence of magnetic field. In this paper it has been shown theoretically that
how the electron motion is influenced in terms of heating, containment and azimuthal uniformity of plasma, by the axial rotation
of the multipole magnetic field [1,2]. Afterwards, the feasibility of achieving a rotating magnetic multipole field is discussed
to some extent. And it is seen that it is not beyond the capability of the scientific community in the present scenario of
the advanced technology. Presently, it can be achieved for lesser field and slightly larger size of the multipole electromagnet
and can be used for improvement of the ECR ion source (ECRIS). 相似文献
84.
Arun?K.?Jugran Amit?Bahukhandi Praveen?Dhyani Indra?D.?BhattEmail author Ranbeer?S.?Rawal Shyamal?K.?Nandi 《Applied biochemistry and biotechnology》2016,179(6):911-926
The changes in total phenolics, flavonoids, tannins, valerenic acid, and antioxidant activity were assessed in 25 populations of Valeriana jatamansi sampled from 1200 to 2775 m asl and four habitat types of Uttarakhand, West Himalaya. Significant (p?<?0.05) variations in total phenolics, flavonoids, valerenic acid, and antioxidant activity in aerial and root portions and across the populations were observed. Antioxidant activity measured by three in vitro antioxidant assays, i.e., 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic) (ABTS) radical scavenging, 2,2′-diphenyl-1-picryylhydrazyl (DPPH) free radical scavenging, and ferric-reducing antioxidant power (FRAP) assays, showed significant (p?<?0.05) differences across the populations. However, no clear pattern was found in phytochemicals across the altitudinal range. Among habitat types, (pine, oak, mixed forest, and grassy land), variation in phytochemical content and antioxidant activity were observed. Equal class ranking, neighbor-joining cluster analysis, and principal component analysis (PCA) identified Talwari, Jaberkhet, Manjkhali, and Khirshu populations as promising sources with higher phytochemicals and antioxidant activity. The results recommended that the identified populations with higher value of phytochemicals and antioxidants can be utilized for mass multiplication and breeding program to meet the domestic as well as commercial demand. 相似文献
85.
Unni AK Takenaka N Yamamoto H Rawal VH 《Journal of the American Chemical Society》2005,127(5):1336-1337
Axially chiral 1,1'-biaryl-2,2'-dimethanol (3, BAMOL) family of diols are highly effective catalysts for enantioselective hetero-Diels-Alder reactions between aminosiloxydiene 1 and a wide variety of unactivated aldehydes. The reactions proceed in useful yields and excellent enantioselectivities. The diols function in the same capacity as Lewis acids, by activating the aldehyde carbonyl group through hydrogen bonding. 相似文献
86.
[reaction: see text] Multifunctional palladium catalysis is utilized in the one-pot stereocontrolled synthesis of tetrasubstituted methyl ketones and enynes. The homogeneous palladium dihalide catalyst utilized for the bromo-/chloroallylation of alkynes is reused in situ for subsequent Wacker-Tsuji oxidation or Sonogashira cross-coupling. 相似文献
87.
A simple high yielding procedure is described for the direct conversion of aldehydes to t-butyldimethylsilyl (TBS) protected cyanohydrins using TBSCl, KCN and ZnI2. 相似文献
88.
[chemical reaction: see text]. The concept of hydrogen bonding catalysis was extended to the vinylogous Mukaiyama aldol reaction, which gives rapid access to polyketide derivatives. The reaction of the silyldienol ether shown and a range of aldehydes catalyzed by TADDOL proceeds regiospecifically to produce the addition products in good yields and enantiomeric excesses. 相似文献
89.
In vivo progressive effects of UV irradiation on the lens epithelium were studied using various histomorphological and biochemical parameters. Fifteen day old rat pups were exposed to 600 mW/m2 of radiation, including UV-A and UV-B, 12 h daily for 90, 120, 150 and 180 days. Biochemical parameters such as protein-bound and non-protein-bound sulfhydryl groups in both soluble and insoluble fractions and enzymes, which play an important role in combating the oxidative stress, were studied. Decreased cell density of lens epithelial cells (LEC) was observed in all three zones along with the decrease in the levels of soluble sulfhydryls (S-SH), glutathione reductase (GR), superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT). On the other hand, an increase in insoluble sulfhydryls was observed. Because of the decrease in S-SH and GR activities, the LEC became vulnerable to oxidative stress. Decreased activities of SOD, GPx and CAT suggest elevated oxidative stress. This effect of UV radiation may lead to cell death that may be responsible for the observed decrease in the cell density in all three zones of the lens epithelium. 相似文献
90.
Achiral and chiral 1-(2-oxazolidinon-3-yl)-3-siloxy-1,3-butadienes were prepared from readily available starting materials. Although more stable than the parent 1-amino-3-siloxy dienes, the 1-(2-oxazolidinon-3-yl)-3-siloxy-1,3-butadienes are still very reactive in Diels-Alder reactions, somewhat more than 1,3-dialkoxy-1, 3-butadienes (e.g., Danishefsky's diene). The cycloadditions of the achiral and chiral dienes with several different dienophiles were examined. The reactions proceeded in good yield, with modest to high endo selectivity. The chiral dienes exhibited excellent facial selectivity in cycloadditions with alpha-substituted acroleins, maleic anhydride and N-phenylmaleimide. Upon reduction and hydrolysis of the cycloadducts, substituted cyclohexenones were obtained with ee's ranging from 22% to >98%. 相似文献