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91.
利用密度泛函的B3LYP方法, 在6-311G*基组水平对吡啶酮系偶氮类化合物进行构型优化, 并进行了自然键轨道(NBO)分析, 然后用TDDFT方法和ZINDO/S方法分别计算了它们的可见吸收光谱, 结果均与实验值十分吻合. 通过对比发现, 对于最高吸收波长的计算, ZINDO/S能以较快的速度得到较好的结果. 在用ZINDO/S计算的过程中, 回归分析发现π-π重叠加权因子(OWFπ-π)与染料分子吡啶环上两个羰基氧原子平均电荷ZO有较好的线性关系: OWFπ-π=0.11425-1.04178ZO, 这一关系不仅可从量子化学的角度进行解释, 而且可用于同类染料可见吸收光谱的预测. 分子轨道的研究表明, 这些化合物的最高可见吸收波长主要对应着共轭体系中给电子体到受电子体的电子跃迁. 相似文献
92.
AbstractAn investigation on seeds of Brucea javanica led to the acquisition of a new quassinoid, 20-hydroxyyadanzigan (1), along with five known quassinoids (2–6). The structure of the new compound was elucidated on the basis of extensive spectral analysis. All of the compounds were assayed for their anticomplement activities through classical and alternative pathways. Compounds 1–6 exhibited potent anticomplement activity with CH50 and AP50 values of 0.032–0.075?mg/mL and 0.061–0.118?mg/mL, respectively. Moreover, the structure-activity relationships of these compounds are discussed. 相似文献
93.
The molar heat capacity of the azeotropic mixture composed of ethanol and toluene was measured by a high precision adiabatic calorimeter from 80 to 320 K. The glass transition and phase transitions of the azeotropic mixture were determined based on the heat capacity measurements. A glass transition at 103.350 K was found. A solid-solid phase transition at 127.282 K, two solid-liquid phase transitions at 153.612 and 160.584 K were observed, which correspond to the transition of metastable crystal to stable crystal of ethanol and the melting of ethanol and toluene, respectively. The thermodynamic functions and the excess ones of the mixture relative to the standard temperature 298.15 K were derived based on the relationships of the thermodynamic functions and the function of the measured heat capacity with respect to temperature. 相似文献
94.
A previous method for the determination of penicillins by direct titration with potassium iodate under strongly acidic conditions has been extended to the assay of some selected cephalosporins. Results are presented, including error and precision analyses, for the determination of cephaloridine, cephalothin and cephalexin. The appropriate stoichiometries are 1 mol cephalosporin to 3 mol iodate for cephalothin and cephaloridine; 1 mol to 2 mol iodate for cephalexin. An irreversible aqueous end-point technique has been compared with the chloroform layer method; the latter gives more precise results for the determination of cephaloridine and cephalothin (0.8% and 1.3% r.s.d. respectively). Comparable precision was obtained by either technique for the determination of cephalexin (1.39% r.s.d.). 相似文献
95.
96.
在260~380 K范围内, 用DSC法研究液晶HpBAB的相变。实验查明HpBAB在室温还以玻璃性晶体状态存在。它的玻璃转变、熔化和清亮过程的热力学参数准确地被测到。提出对-正烷氧基亚苄基-对-氨基苯腈同系列中熔化熵和烷基碳原子数的线性关系; 改进Aranow统计模型并估算直线斜率为Rln(3/g)(1相似文献
97.
Two new C18-norditerpenoid alkaloids from Aconitum delavayi 总被引:2,自引:0,他引:2
Shan Hao Jiang Hai Qing Wang Yi Ming Li Shuang Jun Lin Jun Jie Tan Da Yuan Zhu 《中国化学快报》2007,18(4):409-411
Further phytochemical investigation of the unique C18-norditerpenoid alkaloids from the roots of Aconitum delavayi Franch ledto the isolation of two new norditerpenoid alkaloids,delavaconitine F 1 and delavaconitine G 2.Their structures were determinedfrom spectroscopic evidence. 相似文献
98.
Tongbu Lu Xin Wang Minyu Tan Yu Liu Yoshihisa Inoue Tadao Hakushi 《Helvetica chimica acta》1993,76(1):241-247
The lanthanide nitrate complexes with 13-crown-4(13-C-4) have been prepared in AcOEt. These new complexes with the general formula Ln(NO3)3.(13-c-4) (Ln = La–Nd, Sm–Lu) have been characterized by means of elemental analysis, IR and 1H-NMR spectra, conductivity measurements, and TG-DTA techniques. The crystal and molecular structure of Nd(No3)3. (13-c-4) has been determined by single crystal X-ray diffraction. It crystallizes in the monoclinic space group P21/a with Z = 8. Lattice parameters are a = 15.393(1), b = 12.578(1), c = 19.279(2) Å, β = 113.05(1)°, V = 3435 Å3, Dc = 2.01 g cm?3, μ = 31.0 cm?1 (Mok2), F(000) = 2056. The structure was solved by Patterson and Fourier techniques and refined by least-squares to a final conventional R value of 0.032 for 5218 independent reflections with I ? 3σ(I). There are two independent Nd(No3)3 · (13-C-4) monomers in one asymmetrical unit. The coordination numbers are ten in these two independent monomers. 相似文献
99.
100.