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991.
The negative secondary ion mass spectrometry, in combination with the stereoselective derivatizations with substituted boronic acid RB(OH)2, was used in the analysis of fourteen oligosaccharides. The mass spectra of the derivatives provide information on their linkage positions and isomerism of the individual monosacaccharide units. The results indicated that among the derivatives of the oligosaccharides analyzed, those with 1–4 and 1–6 linkages all presented the ion peaks at m/z 287, sometimes one more peak at m/z 449. Furthermore, a relationship was found between the linkage positions and the intensity orders of the derivative ions. Finally, the derivatives of the disaccharides with a galactose presented an intense ion peak at m/z 347, and those of oligosaccharides with 1–6 linkage to a galactose at terminal presented the ion at m/z 317. In the case of oligosaccharides with a fructose residue, characteristic ion of m/z 155 was produced. The conditions of stereoselective derivatizations and mass spectrometry were studied, in order to obtain a better reproducibility of the mass spectra. 相似文献
992.
Ho-Shen Lin Ashraff A. Rampersaud Karen Zimmerman Mitchell I. Steinberg Donald B. Boyd 《中国化学会会志》1993,40(3):273-282
A series of nonpeptide angiotensin II receptor antagonists was synthesized via palladium-assisted cross coupling of aryl stannane and cycloalkenyl triflates and subsequent alkylation of silyl-protected imidazole. Our compounds, which have a terminal five- to seven-membered cycloalkenyl ring, are compared to DuPont EXP7711, an N-[(2′-carboxybiphenylyl)methyl]imidazole, which has a terminal phenyl moiety. Physicochemical properties of the compounds, such as lipophilicity, steric bulk, conformation, and the relative spatial proximity of the 2-carboxyl and the middle phenyl, are quantitated by computational chemistry. Potency in terms of binding affinity to AT1 receptors in rat adrenal glomerulosa and rabbit aorta is maximized when the terminal ring is aromatic. 相似文献
993.
FFC-1离子交换纤维对酸碱有害气体吸附性能的研究 总被引:8,自引:0,他引:8
系统考察了不同直径及反离子形式的FFC-1聚羧酸离子交换纤维对酸碱有害气体的穿透吸附,各种温、湿度条件下的吸水率,以及作为有害气体吸附滤除材料的重复使用与再生性能。研究表明:FFC-1纤维直径的减小有利于提高对有害气体的动态吸附容量。在体系温度、相对湿度分别为15℃、50%时,以3D腈纶为起始原料的钠型FFC-1离子交换纤维的吸水率≥350mg/g.纤维;对SO2的穿透吸附容量可达200mg/g.纤维。FFC-1离子交换纤维具有良好的重复使用与再生能力,经20次再生循环使用后,纤维交换容量未见明显变化。 相似文献
994.
995.
Hui CY Tang T Lin YY Chaudhury MK 《Langmuir : the ACS journal of surfaces and colloids》2004,20(14):6052-6064
A new cohesive zone model is developed in order to study the mechanisms of adhesive and cohesive failures of soft rubbery materials. The fracture energy is estimated here using a strategy similar to that of Lake and Thomas (LT) by considering the dissipation of stored elastic energy followed by the extension and relaxation of polymer chains. The current model, however, departs from that of LT in that the force needed to break an interfacial bond does not have a fixed value; instead, it depends on the thermal state of the system and the rate at which the force is transmitted to the bond. While the force required to rupture a chain is set by the rules of thermomechanically activated bond dissociation kinetics, extension of a polymer chain is modeled within both the linear and nonlinear models of chain elasticity. Closed form asymptotic solutions are obtained for the dependence of crack propagation speed on the energy release rate, which are valid in two regimes: (I) slow crack velocity or short relaxation time for bond dissociation; (II) fast crack velocity or long relaxation time for bond dissociation. The rate independent and the zero temperature limit of this theory correctly reduces to the fracture model of LT. Detailed comparisons are made with a previous work by Chaudhury et al. which carried out an approximate analysis of the same problem. 相似文献
996.
997.
Yimin Jin J. Bonilla Ye-Gang Lin J. Morgan Linda McCracken J. Carnahan 《Journal of Thermal Analysis and Calorimetry》1996,46(3-4):1047-1059
Two poly(butylene terephthalate)/polycarbonate (PBT/PC) blends with different formulations were analyzed by modulated DSC (MDSC) and conventional DSC to determine differences in crystallization behavior. A significant difference (30°C in cold crystallization temperature) between the two samples was detectable by MDSC while no significant difference was seen by conventional DSC. That indicatesthe total heat flow from MDSC is not always equivalent to the heat flow from conventional DSC as we have assumed or seen before. The reason has not been fully understood, but may be related to unusual nucleation and crystallization induced by modulation. Alternative conventional DSC methods were developed and compared to the MDSC results.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayThe authors like to thank Drs. Bernhard Wunderlich and Robert Gallucci for helpful discussion, David Shaker and Mary Parsonage for some DSC experiments. Technical support from TA Instruments is also greatly appreciated. 相似文献
998.
Limited land and insufficient technicians to operate a wastewater treatment system are main restrictions for many factories.
Therefore, an ideal wastewater treatment method for a small or land-limited factory must possess merits such as high performance
efficiency, high organic loading rate, little odor, simple operation, easy maintenance, and little land required (simultaneously).
An entrapment technique to immobilize mixed microorganisms to treat organic wastewater, which was developed in the present
work, possesses these characteristics. This project was done on a laboratory scale. The microorganisms were activated sludge
(an undefined mixture of microorganisms obtained directly from a domestic wastewater treatment plan) and the mixed microorganisms
were immobilized in cellulose triacetate by means of an entrapment technique to treat organic wastewater from food industry.
After wastewater was treated by this system, the SCOD (soluble COD) removal efficiency of 81% evaluated samples exceeded 80%
in 1.5 ± 0.9 g SCOD/L/d of the volumetric loading rate and 7–10 h for the hydraulic retention time. This wastewater treatment
method can be applied to other organic industrial wastewater. 相似文献
999.
1000.
As bio‐inspired chemical model of the oxygen‐evolving complex (OEC) in photosystem II, a new tyrosine‐modified corrole ligand 3 and its high‐valent copper and manganese complexes 3a and 3b were synthesized and characterized. The copper complexes 1a and 2a of corrole 1 and 2 were also prepared for comparison. The emission property indicates that the emission of ligands 2 and 3 is located at 670 nm, but no emission is observed for their metal complexes due to its suppression by the metal center. The electrochemical study shows that 3a might dimerize at the first two reversible oxidations, a behavior which was not observed in the case of 1a and 2a . The corrolato manganese(IV) complex 3b shows one reversible reduction and one quasireversible oxidation at ?0.17 and 0.77 V vs. Ag/Ag+, respectively. 相似文献