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281.
Wang X Zhang J Song A Lebrilla CB Lam KS 《Journal of the American Chemical Society》2004,126(18):5740-5749
In the "one-bead one-compound" (OBOC) combinatorial library method, each compound bead displays only one compound entity. Hundreds of thousands to millions of compound beads can be synthesized rapidly and screened simultaneously. Positive compound beads are then isolated for structural analysis. To fully exploit the power of OBOC combinatorial small molecule libraries, a robust and high throughput encoding method is needed to decode the positive compound beads. In this paper, we report on the development of a novel encoding strategy that combines the concepts of ladder-synthesis and chemical encoding on bilayer beads. In these encoded libraries, small molecule compounds are displayed on the bead surface, and cleavable coding tags consisting of a series of truncated molecules reside in the bead interior. Such a library can be easily constructed using the biphasic approach (J. Am. Chem. Soc.2002, 124, 7678) to topologically segregate the functionalities of the beads during library synthesis. The ladder members and coding tags are then released for MALDI-TOF-MS analysis. To simplify the interpretation of the mass spectra, we purposely add bromine into the cleavable linker so that the cleavage products generate a characteristic isotope fingerprint. The chemical structure of library compounds can be determined by analyzing the mass differences between adjacent peaks on the mass spectra. This encoding strategy also provides valuable information on the quality of the testing compound on the surface of the bead. To validate this methodology, a model OBOC small molecule library with 12,288 members was synthesized on TentaGel beads and screened against streptavidin. The chemical structures of the compound on each positive bead were unambiguously identified. 相似文献
282.
A novel PBI/P84 co-polyimide dual-layer hollow fiber membrane has been specifically fabricated through the dry-jet wet phase inversion process, for the first time, for the dehydration pervaporation of tetrafluoropropanol (TFP). Polybenzimidazole (PBI) was chosen as the outer selective layer because of its superior hydrophilic nature and excellent solvent-resistance together with robust thermal stability, while P84 co-polyimide was employed as the inner supporting layer because of its good solvent-resistance and thermal stability. The PBI/P84 membrane exhibits superior water selectivity and relatively high permeation flux. At 60 °C, the PBI/P84 dual-layer hollow fiber membrane shows a permeation flux of 332 g/(m2 h) and a separation factor of 1990 for a feed solution containing of 85 wt% TFP. The preferential water sorption and the significant diffusivity difference between TFP and water are the main causes of high separation factor. However, an increase in feed temperature will greatly increase the permeation flux but seriously decrease the water selectivity. The activation energy data verify that water can preferentially permeate the PBI membrane due to the strong water affinity of PBI and a much smaller molecular size of water. 相似文献
283.
Xiangke Wang Yixue Chen Yican Wu 《Journal of Radioanalytical and Nuclear Chemistry》2004,261(3):497-500
The effect of pH and fulvic acid on the sorption of Sr on bentonite was investigated by using batch experiments. The sorption
and desorption isotherms of Sr on bentonite were determined at room temperature, at pH 6.0±0.2 and in presence of 0.1M NaCl.
It was found that the sorption of Sr is independent at pH<8, and then increases slightly with increasing pH. Fulvic acid increases
the sorption of Sr significantly on bentonite at low pH, but decreases the sorption of Sr at pH>8. The sorption of Sr on bentonite
can be described by a reversible sorption process and the sorption mechanism consists mainly of ion exchange.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
284.
The photochemical reaction of Re2(CO)10 with thiophene in hexane solution was investigated under vacuum. Three rhenium clusters: H2Re3(CO)12, HRe3(CO)14 and Re3(CO)14(OH)4, were isolated. The structure of Fellmann-Kaesz cluster Complex HRe3(CO)14 was determined by use of the X-ray diffraction method. The three rhenium atoms form a plane of symmetry and L: Re1Re2Re3 is 107°. The ten carbonyl groups bonded to the two terminal rhenium atoms Re1 and Re3, are staggered with respect to the central rhenium atoms. The bond lengths are 3.10 Å for Re2-Re3 and 3.34 Å for Re1-Re2. The bridging hydride is between Re1 and Re2. 相似文献
285.
286.
Wang Yuntong 《数学年刊B辑(英文版)》1991,12(4):480-494
It is proved that the upper subderivative of a lower semicontinuous function on a Banach space is upper semicontinuous for the first variable as x′→f x, i. e., x′-x, f(x′)-f(x). By taking account of the work of Treiman. it is further shown that the upper subderivative of a 1. s. c. function is the upper limit of the contingent directtional derivatives around the concorned point. This new characterization of the upper suoberivative allows simple derivations and natural extension of many results" in nonsmooth analysis. 相似文献
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