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941.
Temperature modulation has long been used in various aspects of thermal methods. Historically, the principle areas of application
have been the determination of kinetic parameters using variants of the temperature jump method and the measurement of heat
capacity by AC calorimetry. More recently the introduction of temperature modulation in a variety of techniques has been used
in combination with deconvolution algorithms to separate sample responses that are dependent on rate of change of temperature
from those principally dependent on temperature. Finally, temperature modulation is important in the new field of micro-thermal
analysis.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
942.
Hiroshi Noguchi Tsuyoshi Michinobu Nozomu Fujii Masahiro Funahashi Masatoshi Tokita Junji Watanabe Kiyotaka Shigehara 《Journal of polymer science. Part A, Polymer chemistry》2008,46(15):5101-5114
Cyanotolane or fluorotolane mesogens were for the first time introduced into the fumarate monomer under basic conditions. All fumarate monomers undergo radical polymerization in benzene in the presence of dimethyl 2,2′‐azobis(isobutyrate) as an initiator at 60 °C, affording the corresponding poly(fumarate)s with a molecular weight (Mn) of ~ 104 and an exceptionally narrow polydispersity. The phase behaviors of the fumarate monomers and the correspoding poly(fumarate)s were comprehensively investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X‐ray diffraction (XRD) analysis. For the fumarate monomers, fluorotolane derivatives were prone to form higher‐order liquid crystal phases such as a smectic phase, while cyanotolane derivatives tended to show a wide mesophase temperature range, depending on the alkyl chain spacer length. Very surprisingly, these features dramatically weakened when they were polymerized. The mesophase temperature ranges became narrow and completely disappeared for the poly(fumarate)s with a shorter alkyl chain spacer. A nematic phase representing lower‐order arrangements became a predominant liquid crystal phase for the poly(fumarate) carrying cyanotolane mesogens. Only the poly(fumarate) carrying fluorotolane mesogens with a longer alkyl chain spacer displayed the characteristic XRD patterns of the smectic B phase. The transient photocurrent measurements of the fumarate monomer with cyanotolane mesogens displayed a hole mobility of the order of 10?4–10?5 cm2 V?1 s?1 at room temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5101–5114, 2008 相似文献
943.
Abdul G. Al Lafi James N. Hay David J. Parker 《Journal of Polymer Science.Polymer Physics》2008,46(11):1094-1103
Amorphous poly(ether‐ether‐ketone) (PEEK) progressively crosslinks on irradiation with 11.0 MeV protons, and this has a marked effect on the extent of crystallinity that subsequently develops and on the kinetics of the high temperature isothermal crystallization. The extent of crystallinity with time was analyzed using the Avrami equation, and the temperature dependence of the rate constants was analyzed in terms of nucleation theory. While irradiation inhibits the overall rates of crystallization by the reduction in the mobility of the chain segments as observed by the progressive increase in the glass transition temperature, it also alters the fold surface free energy. The observed melting points were consistent with depression of the equilibrium melting point by the crosslinks produced by irradiation. These two effects alone are sufficient to account for the inhibition of crystallization on irradiation of PEEK by protons. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1094–1103, 2008 相似文献
944.
Li Cui Jen‐Taut Yeh Ke Wang Qiang Fu 《Journal of Polymer Science.Polymer Physics》2008,46(13):1360-1368
An investigation of miscibility and isothermal crystallization behavior of Polyamide 6 (PA6)/Poly(vinyl alcohol) (PVA) blends was conducted. Fourier transform infrared spectra (FTIR) analysis indicated that the interactions between the carbonyl groups of PA6 and hydroxyl groups of PVA increase as the weight ratios of PA6 to PVA of PA6/PVA specimens increase. This interaction between PA6 and PVA leads to their miscibility in the amorphous region and even some extent effects on their crystal phase, respectively. Further isothermal crystallization behavior of PA6/PVA indicate that the miscibility of PVA in PA6 leading difficulty in crystallization of PA6. Several kinetics equations are employed to describe the effects of PVA on the crystallization properties of PA6 in PA6/PVA blends in detail. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1360–1368, 2008 相似文献
945.
E. Rudnik I. Resiak C. Wojciechowski Z. Dobkowski 《Journal of Thermal Analysis and Calorimetry》2001,64(2):495-500
Laboratory-made asymmetric polyurethane membranes designed for immunoisolation were investigated. Two types of EK and ES membranes
were prepared in different spinning conditions.
The membrane structure was characterised by the skin pore radius measurements using differential scanning calorimetry (DSC).
Diffusive transport properties of membranes were determined by in vitro method for albumin and creatinine. The scanning electron
microscopy (SEM) was applied to study the morphology of membranes.
It has been found that the DSC technique is a useful tool for the evaluation of pore radii in the skin layer for PU membranes.
Calculated pore radii were in the range from 1.95 to 2.47 nm for the EK and ES types. A correlation between the skin pore
radii and the transport properties was not found in this case of investigated membranes. However, the transport properties
data can serve for the estimation of selectivity of membranes. Thus, the selectivity of membranes for solutes of various molecular
size was estimated from the D
m/D
w ratio of diffusion coefficients for albumin and creatinine. The SEM micrographs reveal the finger-like internal structure
of capillary membranes, as well as various skin thickness.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
946.
Maria F. Ebel Horst Ebel Guido Barnegg-Golwig Michael Mantler Robert Svagera 《Mikrochimica acta》1990,101(1-6):63-69
The paper gives an outline of the basic principle of our imaging technique for XPS. The advantage of the concept is its excellent applicability to quantitative pixel information. This idea is verified by two examples which are representative for routine problems in XPS. These are quantitative surface analysis and determination of overlayer thicknesses. A lateral resolution of at least 0.2 mm is achieved and thus a pixel size of 0.2 mm × 0.2 mm can be quantified automatically by means of numerical algorithms without need of reference samples.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday 相似文献
947.
948.
Keiji Kataoka 《Optical Review》2008,15(4):196-203
In the slant scanning method of multiple beams a misalignment of the slant angle causes a beam spacing error and pitch irregularities
of scan lines called “banding”. This paper evaluates the pitch irregularities and tries to clarify the allowable beam spacing
error. The following results are obtained: (1) The maximum spacing error of print lines is proportional to m/(dpi), where m is the number of multiple beams and dpi print dot density. (2) The noticeable limit of periodic variations of print density
at low spatial frequency was presumed to be a visibility between 1 and 2% in experiments. (3) The allowable beam spacing error
was calculated introducing the human eye spatial frequency response. (4) The banding simulation experiments by laser recording
on the photographic paper on the XY stage showed good coincidence with the theoretical evaluations. 相似文献
949.
Fan Zhang Li Zhou Yuanqin Xiong Weijian Xu 《Journal of Polymer Science.Polymer Physics》2008,46(20):2201-2211
The crystallization kinetics of the high‐flow nylon 6 containing polyamidoamine (PAMAM) dendrimers units in nylon 6 matrix was investigated by differential scanning calorimetry. The Ozawa and Mo equations were used to describe the crystallization kinetics under nonisothermal condition. The values of Avrami exponent m and the cooling crystallization function F(T) were determined from the Ozawa plots, which showed bad linearity, and were divided into three sections depending on different cooling rates. The plots of the m and log F(T) values versus crystallization temperatures were obtained, which indicated that the actual crystallization mechanisms might change with the crystallization temperatures. The high‐flow nylon 6 has higher values of m and log F(T) than those of pure nylon 6, which implied that the high‐flow nylon 6 had more complicated crystallization mechanisms and slower crystallization rate than those of pure nylon 6. The good linearity of the Mo plots verified the success of this combined approach. The activation energies of the high‐flow nylon 6 ranged from 157 to 174 kJ/mol, which were determined by the Kissinger method. The ΔE values were lower than those of pure nylon 6, and the ΔE values were affected by both the generation and the content of PAMAM units in the nylon 6 matrix. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2201–2211, 2008 相似文献
950.
Moses T. Kabomo Frank D. Blum Suntree Kulkeratiyut Suriyaphongse Kulkeratiyut Piyawan Krisanangkura 《Journal of Polymer Science.Polymer Physics》2008,46(6):649-658
The behavior of relatively monodisperse adsorbed poly(methyl methacrylate) (PMMA) samples, from 19 to 587 kDa on silica, was studied using modulated differential scanning calorimetry and FTIR. On untreated Cab? O? Sil silica, the glass transition temperatures (Tgs) were higher (by around 30 °C), and the transitions were significantly broader (by a factor of 5–6) than those for the corresponding bulk samples. While the Tgs for the bulk polymers showed the expected dependence on molecular mass, the polymers on untreated silica showed little dependence, i.e., at the same adsorbed amounts, the glass transitions were very similar. The FTIR spectra of the adsorbed PMMA (on untreated silica) showed the presence of at least two resonances, one for the bound (hydrogen bonded to surface silanols) and another for free carbonyls. Fitting of the spectra allowed the estimation of the bound fractions of carbonyls that were dependent on the adsorbed amount, but not molecular mass. On Cab? O? Sil treated with hexamethyldisilizane (HMDS), the adsorbed PMMA exhibited glass transition behavior with little molecular‐mass dependence; the Tgs for the different PMMA samples were very similar to those of the high‐molecular mass bulk polymer, but with additional broadening of about a factor of 2. FTIR spectra for the PMMA samples on the treated silica did not show significant amounts of any of the hydrogen‐bonded carbonyl groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 649–658, 2008 相似文献