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81.
Jing Xu Yibao Li Lejia Wang Xiaoyang Zhu Xunwen Xiao Yanfang Geng Ke Deng Qingdao Zeng 《中国化学快报》2019,30(3):767-770
Because of the effect of pyridine on the substituent position on the TTF group, TTF derivatives exhibit different assembly structures at the interface, which will be of great significance to the construction of functional nanostructures from the molecular design point of view. 相似文献
82.
Evans PA Sawyer JR Lai KW Huffman JC 《Chemical communications (Cambridge, England)》2005,(31):3971-3973
The crossed intermolecular rhodium-catalyzed [2+2+2] carbocyclization of carbon and heteroatom tethered 1,6-enynes can be accomplished with symmetrical and unsymmetrical alkynes, to afford the corresponding bicyclohexadienes in an efficient and highly selective manner. 相似文献
83.
The benzamide-derived P,O-ligands efficiently promoted the Pd-catalyzed Suzuki cross-coupling reactions of aryl bromides with phenylboronic acid at 0.01 mol % of Pd loading at 60-80 °C to form biaryls in excellent yields. A sterically hindered arylboronic acid gave a quantitative yield of the coupling product at 110 °C with 1 mol % Pd. 相似文献
84.
Yunhui Zhai Xijun Chang Yuemei Cui Ning Lian Shoujun Lai Hong Zhen Qun He 《Mikrochimica acta》2006,154(3-4):253-259
A rapid, selective method that utilize 4-(2-Pyridylazo)-resorcinol (PAR)-modified nanometer SiO2 (nanometer SiO2–PAR) as a new solid-phase extractant for preconcentration of trace mercury (II) has been developed. The adsorption property
of nanometer SiO2–PAR for metal ions was studied by selectively extracting different metal ions from aqueous solutions. The results revealed
an excellent affinity of the nanometer SiO2–PAR for mercury (II) in presence of interfering metal ions at pH 4. The main parameters of solid-phase extraction such as
shaking time, elution and sample dilution effect were studied. The extractant shows rapid kinetic sorption, and the adsorption
equilibrium of mercury (II) on nanometer SiO2–PAR was achieved in less than 2 min. The adsorbed mercury (II) was easily eluted by 4 mL of 6 mol L−1 HCl. The maximum preconcentration factor was 50. The maximum static adsorption capacity was 276 μmol g−1 at pH 4. The detection limit (3σ) was 0.43 μg L−1 for cold vapor atomic absorption spectrometry (CVAAS), and the relative standard deviation of the eight replicate determinations
was 2.4% for the determination of 2.0 μg of Hg(II) in 100 mL water sample. The method was applied to the determination of
trace mercury (II) in sample solutions with satisfactory results. 相似文献
85.
比值光谱导数法同时测定铝合金中铁,铜,锌 总被引:6,自引:0,他引:6
用比值光谱-导数分光光度法,在pH5.5缓冲溶液中,利用金属-2-(5-溴-2-吡啶偶氮)-5-二乙氨基酚(5-Br-PADAP)-OP三元络合物显色体系,对混合物中铁,铜,锌三组分进行了同时测定。合成试样5次测定回收率在97.3%-104.4%之间。应用于铝合金中铁,铜,锌的测定,各6次测定的RSD分别为3.66%,1.38%,2.03%。 相似文献
86.
液相色谱中一个新的表征参数Z:Ⅱ.反相液相色谱中小分子极性溶质体系 总被引:3,自引:2,他引:3
反相高效液相色谱(RPLC)中小分子极性溶质的极性是可以用液相色谱中溶质计量置换保留模型中的Z值(1mol溶质被固定相吸附时,在固定相与溶质子间释放出置换剂的mol数)来表征的,其大小可用带有该极性端基的同系物的Z值对碳原子数线性作图的截距求得。这些检性基的Z测量定值与疏水性片段指数1gf间有极好的线性关系。依此关系还可测出一些用其他实验方法无法测得的某些基团的1gf值。 相似文献
87.
A parallel solution combustion synthesis technique was developed for combinatorial materials studies. The vigorous combustion reactions were successfully limited in the microreactors by using a substrate-net-mask microreactor system and the lowest adoptable furnace temperature. Using this technique, a luminescent materials library of Y3Al5O12/Tb(chi) was synthesized with the aid of an ink-jet delivery system. Structure and luminescence characterizations were implemented using X-ray diffraction and UV/X-ray spectroscopies, respectively. The results show that this technique is reliable and applicable to combinatorial study of powder materials with high synthesis temperature. 相似文献
88.
An automated spray-and-trap (ST) chromatographic system was constructed for fast and efficient extraction of volatile organic compounds (VOCs) in aqueous samples with the capability to be deployed in the field for unattended continuous monitoring of surface or ground water. This system was built upon a commercial gas chromatograph with full automation capability using self-developed hardware and software. For sample analysis, fine droplets of the aqueous solution were generated in the extraction chamber by pressure expansion of a clean air stream through a spray nozzle. A portion of the VOCs distributed into the gas phase was retained by a multi-sorbent micro-trap kept at ambient temperature. Flash heating of the sorbent trap desorbed the enriched VOCs onto the gas chromatography (GC) with flame ionization detection (FID) for hydrocarbons or electron-capture detection (ECD) for halocarbons. In order to validate the performance of the ST method. it was compared with a more conventional method, i.e., a purge-and-trap (PT), by analyzing a serious of standard solutions containing benzene, toluene, ethylene. and o-, m-xylenes. Using a purge-and-trap method as a reference for complete extraction, the ST method showed less sensitivity. Extraction recoveries are in consistent with Henry's law constants. To test response time the ST-GC-ECD was periodically switched between tap and underground waters. Negligible carry-over of halogenated species and reproducibility better than 2% relative standard deviation (R.S.D.) can be achieved regardless of large concentration difference between the two sources, thus demonstrating applicability of the ST system for on-site monitoring. 相似文献
89.
The Brownian-type molecular dynamics simulation is revisited and applied to study the thermal and geometric properties of four mono- and two polyvalent metallic clusters. For the thermal property, we report the specific heat at constant volume CV and study the solid-liquid-like transition by scrutinizing its characteristic. For the geometric property, we calculate the root mean square relative bond-length fluctuation delta as a function of increasing temperature. The thermal change in delta reflects the movement of atoms and hence is a relevant parameter in understanding the phase transition in clusters. The simulated results for the CV of alkali and aluminum clusters whose ground state structures exhibit icosahedral symmetry generally show one phase transition. In contrast, the tetravalent lead is quite often seen to exhibit two phase transitions, a premelting process followed by a progressive melting. In connection with the premelting scenario, it is found here that those (magic number) clusters identified to be of lesser stability (among other stable ones) according to the second energy difference are clusters showing a greater possibility of undergoing premelting process. This energy criterion applies to aluminum clusters nAl=28 and 38. To delve further into the thermal behavior of clusters, we have analyzed also the thermal variation of deltaT and attempted to correlate it with CV(T). It turns out that the premelting (if exist) and melting temperatures of the smaller size clusters (n less, similar 50) extracted from CV do not always agree quantitatively with that deduced from delta. 相似文献
90.
Dudkin VY Orlova M Geng X Mandal M Olson WC Danishefsky SJ 《Journal of the American Chemical Society》2004,126(31):9560-9562
Synthetic gp120331-335 glycopeptide fragments carrying hybrid and high-mannose type N-linked glycans were evaluated for binding to broadly neutralizing antibody 2G12 using surface plasmon resonance technology. None of the hybrid-type constructs demonstrated binding to 2G12. In the high-mannose series, the "Cys dimer" construct, presenting two undecasaccharide glycans, showed significantly higher binding than the Cys-protected monomer. The binding of the dimeric structure was further investigated in competition with recombinant gp120. The data suggest that gp120 and its designed synthetic epitope construct bind to the same site on 2G12. 相似文献