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121.
The paper presents a new tool for the determination of inorganic speciation forms of aluminium: AlFn(3 − n)+, and Al3+ by means of the HPIC-FAAS. The proposed method has been successfully used for speciation analysis (qualitative and quantitative) of inorganic aluminium forms AlFn(3 − n)+ in soil samples. In order to isolate the most environmentally available fraction, 5 g of the sample was collected and extracted in deionised water (water soluble fraction) for 1 h using a magnetic stirrer. The determinations in a hyphenated technique system were performed for a number of prepared water extracts. Concentration determinations of particular aluminium forms were performed based on model studies and real samples. The separation of Al species with nominal charge of + 1, + 2, and + 3 required a run time of less than 4 min during a single analysis. Based on the analysis of water extracts of soil, it was obtained that aluminium forms elute in the following order: 1PA (first signal) — AlF2+ and/or AlF4−; 2PA (second signal) — AlF2+ and/or AlF30; 3PA (third signal) — Al3+. In order to confirm the occurrence of these forms a simulation using the Mineql program was conducted. The details of speciation analysis of aluminium fluoride forms by means of an HPIC-FAAS instrument equipped are presented. Interpretation of the speciation analysis of the water soluble fraction of soil samples is proposed, based on the separation during chromatographic run and calculated data by Mineql. 相似文献
122.
123.
Bin Wang 《Optics Communications》2011,284(14):3504-3508
124.
Pradip B. SarawadeJong-Kil Kim Askwar HilongaDang Viet Quang Hee Taik Kim 《Applied Surface Science》2011,258(2):955-961
The conventional drying (oven drying) method used for the preparation of precipitated mesoporous silica with low surface area (>300 m2/g) and small pore volume is often associated with a high production cost and a time consuming process. Therefore, the main goal of this study was to develop a cost-effective and fast drying process for the production of precipitated mesoporous silica using inexpensive industrial grade sodium silicate and spray drying of the precipitated wet-gel silica slurry. The precipitated wet-gel silica slurry was prepared from an aqueous sodium silicate solution through the drop-wise addition of sulfuric acid. Mesoporous precipitated silica powder was prepared by drying the wet-gel slurry with different drying techniques. The effects of the oven drying (OD), microwave drying (MD), and spray drying (SD) techniques on the physical (oil, water absorption, and tapping density), and textural properties (specific BET surface area, pore volume, pore size, and % porosity) of the precipitated mesoporous silica powder were studied. The dried precipitated mesoporous silica powders were characterized with field-emission scanning electron microscopy; Brunauer, Emmett and Teller and BJH nitrogen gas adsorption/desorption methods; Fourier-transform infrared spectroscopy; thermogravimetric and differential analysis; N2 physisorption isotherm; pore size distribution and particle size analysis. There was a significant effect of drying technique on the textural properties, such as specific surface area, pore size distribution and cumulative pore volume of the mesoporous silica powder. Additionally, the effect of the microwave-drying period on the physicochemical properties of the precipitated mesoporous silica powder was investigated and discussed. 相似文献
125.
The present study has been conducted in order to determine the influence of superalloy substrate roughness on adhesion and oxidation behavior of magnetron-sputtered NiCoCrAlY coatings. Six types of coating samples with different substrate roughness were tested. The surface roughness and real surface area of both the substrates and coatings were studied by atomic force microscopy (AFM) techniques. The scratch tests performed at progressive loads were employed to evaluate the adhesion of the coatings. Cyclic oxidation tests were performed at 1100 °C in air for 50 cycles, each cycle consisting of 1 h heating in the tube furnace followed by 15 min cooling in the open air. The AFM measurements exhibit that the surface roughness of the sputtered NiCoCrAlY coating increases with the increasing of the superalloy substrate roughness. The NiCoCrAlY coatings present slightly lower roughness than the corresponding superalloy substrate. The scratch adhesion tests indicate that the coatings on substrates with a smoother surface possess better adhesion than on those with a rougher surface. Both the real surface area and oxidation weight gain of the coatings decrease with the decreasing of the superalloy substrate roughness. The NiCoCrAlY coating sputtered on the superalloy substrate with lower roughness provides relatively higher antioxidant protection than that provided by the coating with rougher substrate. 相似文献
126.
The loss of pulmonary artery (PA) compliance has significant pathophysiological effect on the right ventricle. Noninvasive and reliable assessment of PA wall stiffness would be an essential determiner of right heart load and a clinically useful factor to assess cardiovascular risk. Two MRI techniques have been proposed for assessing PA stiffness by measuring pulse wave velocity (PWV): transit time (TT) and flow area (QA). However, no data are available that compares the two techniques and evaluates their performance, especially over a wide range of PWV values or at 3.0-T, which is the purpose of the present study. Thirty-three patients with different heart conditions were imaged using optimized high-temporal resolution and high-spatial resolution velocity-encoding MRI sequences. Statistical analysis was conducted to study intermethod, interobserver and intraobserver variabilities. The PWV measurements using TT and QA techniques showed good agreement (P>0.1). The Bland-Altman analysis showed negligible differences between the two methods (mean±S.D.=0.11±0.35 m/s, correlation coefficient r=0.94). The repeated measurements showed low interobserver and intraobserver variabilities, although the S.D. of the differences was larger in the QA technique. The mean±S.D. of the TT/QA measurement differences were −0.05±0.2/0.0±0.36 m/s and 0.02±0.26/0.02±0.39 m/s for the interobserver and intraobserver differences, respectively. In conclusion, each technique has its own advantages and disadvantages. The two techniques result in similar measurements, although the QA method is more subjective due to its dependency on operator intervention. 相似文献
127.
Area integral functions are introduced for sectorial operators on Lp-spaces. We establish the equivalence between the square and area integral functions for sectorial operators on Lp spaces. This follows that the results of Cowling, Doust, McIntosh, Yagi, and Le Merdy on Hinfin functional calculus of sectorial operators on Lp-spaces hold true when the square functions are replaced by the area integral functions. 相似文献
128.
Ruifang HU Bolin MA Xianmin XU 《Frontiers of Mathematics in China》2014,9(5):1051-1072
We introduce the generalized area operators by using nonnegative measures defined on upper half-spaces R+^n+1. The characterization of the boundedness and compactness of the generalized area operator from LP(]Rn) to Lq(IRn) is investigated in terms of s-Carleson measures with 1 〈 p, q 〈 +∞. In the case of p = q = 1, the weak type estimate is also obtained. 相似文献
129.
Let ? ∈ L~2(S~(n-1)) be homogeneous function of degree zero and b be BMO functions. In this paper, we obtain some boundedness of the Littlewood-Paley Operators and their higher-order commutators on Herz spaces with variable exponent. 相似文献
130.
Carbon aerogel (CA) microspheres have been successfully synthesized by an inverse emulsion polymerization and characterized by scanning electron microscopy (SEM), N2 sorption isotherm and X-ray diffraction (XRD). The results show that the size and pore characteristics of carbon microsphere obviously depend on stirring speed and concentration of surfactant in the emulsion polymerization process. The resultant CA microspheres are amorphous carbon structure with the size ranging from about 2 to 50 μm by changing the stirring speed. CA microspheres with SBET of 414-603 m2 g− 1 and Vmeso of 0.028-0.432 cm3 g− 1 are synthesized using different SPAN80 concentrations. The results of cyclic voltammetry indicate that the CA microspheres prepared at a stirring speed of 480 rpm and at Vs/Vh = 0.01 have ideal supercapacitive behavior in 6 M KOH electrolyte, the maximum specific capacitance of the electrode reaches 180 F g− 1. 相似文献