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141.
低压离子色谱法测定土壤中速效钾 总被引:1,自引:0,他引:1
通常对土壤中速效钾的测定方法所用仪器昂贵。而低压离子色谱分析仪结构简单,操作简便,速度快,灵敏度高,价格低[1]。本文通过试验,确立了低压离子色谱法测定土壤速效钾的最佳条件,对实际样品的测定结果与推荐值呈显著相关性。1 实验部分土壤经风干、研磨,过100目土壤筛,测定其水份系数[2],贮存于密闭玻璃瓶内备用。准确称取2 0000g土样于50ml烧杯内,加20ml提取剂(0 05mol/LHCl+0 0125mol/LH2SO4),摇匀,25℃提取25分钟,离心分离。连接色谱仪、记录仪、蠕动泵(图1)。自制2J 3低压离子色谱仪,量程10×10μs,蠕动泵流速10刻度,记录仪量… 相似文献
142.
应用液/液界面微电极对二苯并18-冠-6(DB18-C-6)辅助推动Ba~(2+)在1,2-二氯乙烷/水(DCE/W)界面转移的电化学过程进行了详细探讨,证明该过程遵循TIC机理,是受扩散控制的可逆过程。通过转移电流和反应物浓度之间的线性关系,测定了Ba~(2+)以及用其它方法难以测定的DB18-C-6。 相似文献
143.
Y. Marcus 《Journal of solution chemistry》1987,16(9):735-744
The translational entropy loss on the association of two ions to form an ion pair or 11 complex is overcompensated by a rotational entropy gain, an electrostatic entropy gain, and an entropy gain due to solvent release from translational immobilization. The first three effects can be calculated, leaving the fourth as a difference from the experimental entropy change on association. The ratio of the solvent release entropy gain to the entropy change on melting of the solvent indicates the number of solvent molecules released on the association. A similar value is obtained from data for the volume change on association.Presented as a poster at the 10th International Conference on Non-Aqueous Solvents (ICNAS) at Leuven, Belgium, August 1986, and at the 24th International Congress on Coordination Chemistry (ICCC) at Athens, Greece, August 1986. 相似文献
144.
Takashi Hayashita Akiyo Yamauchi Ai-Jun Tong Jong Chan Lee Bradley D. Smith Norio Teramae 《Journal of inclusion phenomena and macrocyclic chemistry》2004,50(1-2):87-94
The design and function of novel supramolecular fluoroionophore/cyclodextrin (CyD) complex sensors for ion and molecule recognition in water are reviewed. For the crown ether fluoroionophore/-CyD complex, the dimerization of the fluoroionophore inside the -CyD is found to be selectively promoted by alkali metal ion binding, thereby resulting in metal-ion-selective pyrene dimer emission in water. This supramolecular function is successfully utilized in the design of a podand fluoroionophore/-CyD complex for sensing toxic lead ion in water. The boronic acid fluoroionophore/-CyD complex binds sugars and produces increased fluorescence emission in water. The response mechanism appears to be due to the suppression of the photoinduced electron transfer (PET) from pyrene donor to trigonal phenylboronic acid acceptor. This is a novel emission function provided by the boronic acid fluoroionophore/-CyD complex sensors in water. 相似文献
145.
Manfred Leisch 《Mikrochimica acta》1992,107(3-6):95-104
The atom probe field ion microscope (AP-FIM) is a combination of a field ion microscope and a time-of-flight mass spectrometer with a single ion detection sensivity. With the field ion microscope topology of a surface, surface reactions and surface modifications can be studied in atomic detail. By time-of-flight measurements surface layers and interface layers can be chemically analyzed atom by atom and atomic layer by atomic layer. Compositional variations according to surface or interface segregation, precipitations, or surface changes in corrosion or in electrochemical layer formation etc. can be studied quantitatively on a subnanometer scale. Some of our studies on related problems will be decribed briefly. 相似文献
146.
以Mn2O3和氢氧化锂为原料,通过焙烧合成出o-LiMnO2。用X射线衍射和扫描电镜对不同温度下合成的粉末样品进行了表征,并研究了材料的电化学性能。通过对不同温度条件下烧结样品的晶胞参数、布拉格(110)晶面峰半高宽及电化学性能研究发现:600 ℃下合成样品的半高宽最大,堆垛层错率高,同时电化学性能也最好,首次放电容量达到156 mAh·g-1,20次循环后仍保持在140 mAh·g-1以上。中高温固相合成的o-LiMnO2材料,在晶粒范围大小相近时,材料电化学性能与材料堆垛层错率相关。 相似文献
147.
《Surface and interface analysis : SIA》2006,38(5):931-940
The initial oxidation of magnesium at oxygen partial pressures between 1.3 × 10?8 and 1.3 × 10?5 Pa and at temperatures ranging from 273 to 550 K has been investigated in situ with X‐ray photoelectron spectroscopy (XPS), ellipsometry and high resolution elastic recoil detection analysis (HERDA). Quantitative analysis of the XPS spectra showed a clear oxygen deficiency with respect to MgO for the initial oxide. HERDA measurements confirmed this relatively low oxygen content in the thin oxide layers formed. Ellipsometry measurements showed that the electronic structure of the initially formed oxide differs significantly from that of bulk MgO. The band gap values at room temperature for the oxide layers investigated are clearly smaller than the value for bulk MgO. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
148.
In the context of the density functional theory of the local electron density the valence and differential density distribution in crystalline sulfates of M2SO4 (M is Li, Rb, and Cs) and double sulfates of MLiSO4 were calculated using the pseudopotential method in the basis set of numerical atomic pseudo-orbitals. It is shown that in lithium sulfate crystallographically inequivalent oxygen atoms are in different charge states and have a different force of chemical bonding with sulfur. Anions are bonded to each other through lithium atoms that form tetrahedral complexes with oxygen. In rubidium sulfates the electron clouds of the anions overlap and chain structures form. Chemical bonding between the anion and the cation has an ionic nature. These features of the electron structure manifest themselves in double sulfates, where LiO4 complexes that link the anionic chains also form, and heavy metals serve as cations. 相似文献
149.
An ion-exchange method was used to determine complexation constants for the Ni-oxalate and Ni-carbonate systems in a NaClO4 background electrolyte. The Ni-oxalate data were interpreted in terms of a single Niox(aq) complex having log K
1 values for Ni2+ + ox2– Niox(aq) of 3.9 ± 0.1 (I.S. = 0.5 mol-L–1 p[H] = 7.1) and 4.4 ± 0.1 (I.S. = 0.1 mol-L–1 p[H] = 8.6) at 22 ± 1C. Specific ion-interaction theory (SIT) was used to obtain log K
1
= 5.17 ± 0.05 (95% confidence level and = –0.23 ± 0.15) at I.S. = 0. The Ni-carbonate studies were carried out at p[H] values of 7.5, 8.5, and 9.6 in 0.5 mol-L–1 NaClO4/NaHCO3 solutions. The NiCO3(aq) species was the dominant complex in the [CO3
2–] concentration ranges studied at all three p[H] values. A log K
1 value for Ni2+ + CO3
2– NiCO3(aq) of 2.9 ± 0.3 was deduced at I.S. = 0.5 mol-L–1. Extrapolating this value to zero ionic strength using the SIT approach yielded log K
1
= 4.2 ± 0.3 (95% confidence level and = –0.26 ± 0.04). The data allowed upper bound values for the complexation constants for NiHCO3
+ and Ni(CO3)2
2– to be estimated, i.e., log K
< 1.4 for Ni2+ + HCO3
– NiHCO3
+, and log K
2
< 2 for NiCO3(aq) + CO3
2– Ni(CO3)2
2–, respectively. 相似文献
150.