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61.
Valentine KG Pometun MS Kielec JM Baigelman RE Staub JK Owens KL Wand AJ 《Journal of the American Chemical Society》2006,128(50):15930-15931
Proteins encapsulated within the aqueous core of reverse micelles are found to partially align in a magnetic field. The degree of alignment is sufficient to result in sizable residual 15N-1H dipolar couplings that can be easily measured. It is found that the magnetic susceptibility of the reverse micelle particle is not dominated by the encapsulated protein. The residual dipolar couplings are found to be structurally meaningful. 相似文献
62.
63.
Mark B. Hazuka Jeannie J. Kinzie Kathleen A. Davis David A. DeBoise 《Magnetic resonance imaging》1989,7(6):669-676
Thirteen patients with abnormal brain MR scans attributable to treatment-induced injury were retrospectively reviewed. All patients were treated with radiation therapy and 62% received chemotherapy. Five patients were graded as having severe white matter (WM) changes, four had moderate WM changes, and four had mild WM changes. CT was generally equivalent to MR in evaluation of severe and moderate WM abnormalities, whereas MR was superior to CT in detection of mild WM abnormalities. In general, the severity of changes depicted by MR/CT correlated with the extent of neurologic dysfunction. The most severe changes were seen in those patients treated with combination irradiation and chemotherapy. 相似文献
64.
This study evaluates the potential use of stable zinc isotopes in toxicity studies measuring zinc uptake by the gills of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss). The use of stable isotopes in such studies has several advantages over the use of radioisotopes, including cost, ease of handling, elimination of permit requirements, and waste disposal. A pilot study using brown trout was performed to evaluate sample preparation methods and the ability of a quadrupole inductively coupled plasma mass spectrometer (ICP-MS) system to successfully measure changes in the 67Zn/66Zn ratios for planned exposure levels and duration. After completion of the pilot study, a full-scale zinc exposure study using rainbow trout was performed. The results of these studies indicate that there are several factors that affect the precision of the measured 67Zn/66Zn ratios in the sample digests, including variations in sample size, endogenous zinc levels, and zinc uptake rates by individual fish. However, since these factors were incorporated in the calculation of the total zinc accumulated by the gills during the exposures, the data obtained were adequate for their intended use in calculating zinc binding and evaluating the influences of differences in water quality parameters. 相似文献
65.
Kathleen Linn Jeffrey T. Kuethe Zhihui Peng Nobuyoshi Yasuda 《Tetrahedron letters》2008,49(23):3762-3765
An efficient and practical method for the preparation of benzyloxyacetic acids is described. The procedure involves the reaction of readily available chloroacetic acid with benzyl alcohol in the presence of powdered KOH providing a safer alternative to the known literature procedures, which completely eliminates the use of pyrophoric bases such as sodium hydride and sodium metal. 相似文献
66.
Krause KM Vick DW Malac M Brett MJ 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):17558-17567
The high surface area, large aspect ratio, and porous nature of nanorod arrays make them excellent foundation materials for many devices. Of the many synthesis techniques for forming nanorods, glancing angle deposition (GLAD) offers one of the more straightforward and flexible methods for ensuring control of alignment, porosity, and architecture of the nanorods. Here we demonstrate the first use of a dual-beam (focused ion beam (FIB) combined with scanning electron microscopy (SEM)) instrument to section and image the internal morphology of a nanorod array fabricated using the GLAD technique. We have used the FIB-SEM to reconstruct the 3D composition of TiO(2) nanorods, allowing us to visualize for the first time the core structures of many potential devices. We have also been able to probe the relationship between critical parameters such as diameter (w(act)), internanorod spacing (ν(act)), center-to-center spacing (c(act)), and nanorod population density (d(act)) and the depth of the nanocolumn (t) for a single homogeneous structure. A continuous data set was obtained from a single 5-μm-thick GLAD film, avoiding the artifacts arising from the analysis of the top surfaces of multiple samples of varying thicknesses. An analysis of the acquired sectioned data has allowed us to determine that the critical nanocolumn parameters follow a power-law scaling trend with w(act) = 9.4t(0.35) nm, ν(act) = 15.2t(0.25) nm, c(act) = 24.8t(0.31) nm, and d(act) = 3402t(-0.65) columns μm(-2). Using the FIB/SEM images acquired for the TiO(2) nanorods, we have also investigated the evolution of individual nanocolumns and have observed that bifurcation and branching play a significant role in the extinction or survival of these nanorods. These findings will allow for the optimization of nanorod properties for device applications. Also, the FIB sectioning and reconstruction process developed here will permit for the investigation of nanorod arrays formed from a range of synthesis techniques and materials. 相似文献
67.
Michael E. Kurczy Paul D. Piehowsky David Willingham Kathleen A. Molyneaux Michael L. Heien Nicholas Winograd Andrew G. Ewing 《Journal of the American Society for Mass Spectrometry》2010,21(5):833-836
A C60+ cluster ion projectile is employed for sputter cleaning biological surfaces to reveal spatio-chemical information obscured
by contamination overlayers. This protocol is used as a supplemental sample preparation method for time of flight secondary
ion mass spectrometry (ToF-SIMS) imaging of frozen and freeze-dried biological materials. Following the removal of nanometers
of material from the surface using sputter cleaning, a frozen-patterned cholesterol film and a freeze-dried tissue sample
were analyzed using ToF-SIMS imaging. In both experiments, the chemical information was maintained after the sputter dose,
due to the minimal chemical damage caused by C60+ bombardment. The damage to the surface produced by freeze-drying the tissue sample was found to have a greater effect on
the loss of cholesterol signal than the sputter-induced damage. In addition to maintaining the chemical information, sputtering
is not found to alter the spatial distribution of molecules on the surface. This approach removes artifacts that might obscure
the surface chemistry of the sample and are common to many biological sample preparation schemes for ToF-SIMS imaging. 相似文献
68.
69.
Structural Chemistry - In the current study, the energetics of fractionally (and indeed arbitrary non-integer) charged species is explicitly discussed for the enhanced understanding of aromaticity... 相似文献
70.
Simon G. Bott Alan P. Marchand L. Kathleen Talafuse D. Rajagopal 《Journal of chemical crystallography》1995,25(9):543-547
The structure consists of two acetyl-substituted PCU cages linked by a diyne fragment. The conformation about the linker is midway between staggered and eclipsed, and the acetyl groups are somewhat distorted due to the proximity to the bulky cage units. 相似文献