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991.
992.
甘氨酸与水分子间相互作用的理论研究 总被引:1,自引:1,他引:0
在密度泛函(DFT)B3LYP/6_311++G(3d,3p)水平,对中性甘氨酸的最小点结构Ip和H2O分子间可能存在的氢键复合物进行全自由度能量梯度优化,发现了三个氢键极小结构A、C和E,其中结构A为最稳定结构,它是H2O与甘氨酸的羧基(-COOH)形成两个氢键的结构,具有C1对称性.分别采用密度泛函理论(DFT)和MP2方法,在6-311++G(3d,3p)水平,对结构A的结构和结合能进行了比较计算,得到结合能ΔEDFT为-41.88 kJ/mol,ΔEMP2为-40.34 kJ/mol. 相似文献
993.
Stuart R. Batten 《Journal of solid state chemistry》2005,178(8):2475-2479
This article discusses the challenges that face the crystal engineer in the deliberate design of new network structures. These include control over ligand and metal coordination geometry, selection of network topology from a number of possibilities which all have the same connectivity, and control of methods of increasing packing efficiency, including interpenetration (both number of nets (including only one) and topology of interpenetration). These variables can lead to polymorphism and related phenomena, the bane of crystal engineers. Templation by counterions, guest molecules and/or solvents can also lead to unpredictable results. 相似文献
994.
Cellular instabilities of expanding hydrogen/propane spherical flames at elevated pressures: theory and experiment 总被引:1,自引:0,他引:1
An experimental and theoretical investigation of the onset of cellular instabilities on spherically expanding flames in mixtures of hydrogen and propane in air at elevated pressures was conducted. Critical conditions for the onset of instability were measured and mapped out over a range of pressures and mixture compositions. An asymptotic theory of hydrodynamic and diffusional-thermal cell development on flames in mixtures comprised of two scarce fuels burning in air was also formulated. Predicted values of Peclet number, defined as the flame radius at the onset of instability normalized by the flame thickness, were shown to compare favorably with the experimentally measured values. 相似文献
995.
Hongsheng Guo Gregory J. Smallwood Fengshan Liu Yiguang Ju
mer L. Gülder 《Proceedings of the Combustion Institute》2005,30(1):303-311
The effect of hydrogen addition to ultra lean counterflow CH4/air premixed flames on the extinction limits and the characteristics of NOx emission was investigated by numerical simulation. Detailed chemistry and complex thermal and transport properties were employed. The results show that the addition of hydrogen can significantly enlarge the flammable region and extend the flammability limit to lower equivalence ratios. If the equivalence ratio is kept constant, the addition of hydrogen increases the emission of NO in a flame due to the enhancement in the rate of the NNH or N2O intermediate NO formation routes. The addition of hydrogen causes a monotonic decrease in the formation of NO2 and N2O, except flames near the extinction limits, where the emission of NO2 and N2O first increases, and then decreases with the increase in the fraction of hydrogen. Overall, hydrogen enrichment technology allows stable combustion under ultra lean conditions, resulting in significant CO2 and NO emission reduction. 相似文献
996.
Casey L. Elkins Taigyoo Park Matthew G. McKee Timothy E. Long 《Journal of polymer science. Part A, Polymer chemistry》2005,43(19):4618-4631
The synthesis and characterization of copolymers containing 2‐ethylhexyl methacrylate and a quadruple‐hydrogen‐bonding site, 2‐ureido‐4[1H]‐pyrimidone methacrylate (UPyMA), are described. An analogous dimeric hydrogen‐bond‐containing copolymer based on 2‐ethylhexyl methacrylate and methacrylic acid (PEHMA‐co‐MAA) was also synthesized for comparative purposes. The glass‐transition temperatures of the poly(2‐ethylhexyl methacrylate‐co‐2‐ureido‐4[1H]‐pyrimidone methacrylate) (PEHMA‐co‐UPyMA) series increased linearly with increasing UPyMA content. Creep compliance measurements as a function of temperature indicated a decrease in the creep compliance with increasing UPyMA content over the range of 1–10 mol % UPyMA. Melt rheological analysis also showed an increase and lengthening of the plateau modulus as a function of frequency with increasing UPyMA content, as well as increasing complex viscosity as a function of temperature. The analogous PEHMA‐co‐MAA copolymer, which contained 11 mol % methacrylic acid, showed, in the melt rheological analysis, behavior similar to that of the PEHMA‐co‐UPyMA copolymer containing only 1 mol % UPyMA units. The multiple‐hydrogen‐bond‐containing copolymers were successfully analyzed with time–temperature superposition for the construction of master curves. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4618–4631, 2005 相似文献
997.
HAI QING LIU LI NA ZHANG AKIRA TAKARAGI TAKEAKI MIYAMOTO 《Cellulose (London, England)》1997,4(4):321-327
The effect of substituent distribution on the water solubility of O-methylcellulose (MC) was re-examined to elucidate the
lower limit of the degree of substitution (DS) in water-soluble MC. To this end, a series of 2,3-MCs which are regioselectively
substituted at the C-2 and C-3 hydroxyl groups were prepared by homogeneous methylation. It was found that the lower limit
for the DS value of water-soluble 2,3-MC was almost the same as that for MCs having even distributions of substituents along
the cellulose chain as well as in the anhydroglucose units.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
998.
999.
通过对直接键合InP-GaAs结构的红外吸收光谱分析以及断面扫描电子显微镜观察发现,样品制备过程中不均匀的外加压强导致InP-GaAs交界面局部出现了不连续过渡的空间层,实验上将熔融石蜡渗透并被填充到该空间层,利用其对3.509μm波长光的强烈吸收特性可表征 这种局部的键合不连续区域,二维扫描测试样品不同区域的吸收谱得到3.509μm波长吸收强 度等值线图,从而描绘出外加压强的不均匀分布.实验上通过改进键合装置的施压均匀性, 得到了连续过渡界面且均匀键合的InP-GaAs结构,利用这种均匀键合技术有望制备大尺寸器 件例如光学微腔等.
关键词:
晶片直接键合
界面
红外吸收光谱 相似文献
1000.
计算氢同位素水分子汽化焓的比较法 总被引:2,自引:0,他引:2
本文首次提出计算氢同位素水分子汽化焓的比较法,得到0~374℃时H2O,D2O,DTO和T2O的汽化焓,并提出用D2从含氚重水中分离出DT气的适宜温度. 相似文献