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941.
脂肪族饱和一元醇沸点的拓扑研究 总被引:10,自引:0,他引:10
基于邻接矩阵与边价 (fi)定义边价连接性指数 ( mF) ,其中的0 F、醇距离参数L及醇类型参数与 119种脂肪族饱和一元醇的沸点 (Tb)关联、得到良好的数学模型 :ln( 72 4-Tb) =6 0 70 10 -0 0 5 7180 F -0 0 0 3 71L -0 0 75 49δ-1 (n =119) ,R =0 9974.相关性优于文献值 .可以预示 ,该模型能更精确的预测饱和醇的沸点 . 相似文献
942.
应用密度泛函理论,在B3LYP/6-31G水平上优化了线性簇合物SC2nS2-(n=1~12)的基态平衡几何结构,并计算了它们的谐振动频率.在基态平衡构型下,通过TD-B3LYP/cc-pvTZ和TD-B3LYP/cc-pvDZ计算,确定了簇合物SC2nS2-(n=1~10)X1Σ g→11Σ u电子跃迁的垂直激发能和对应的振子强度.基于计算结果,导出了X1Σ g→11Σ u电子跃迁吸收波长与体系大小n的解析关系式,以及SC2nS2-体系第一电离能与体系大小n的解析表达式,并讨论了不同端位原子对碳链体系激发态性质的影响. 相似文献
943.
Transition metal-catalyzed [m+n+o] carbocyclization reactions provide powerful methods for the construction of complex polycyclic systems that are generally not accessible through classical pericyclic reactions. We have developed the first regio- and enantioselective crossed intermolecular rhodium-catalyzed [2+2+2] carbocyclization of carbon- and heteroatom-tethered 1,6-enynes with unsymmetrical 1,2-disubstituted alkynes. This study clearly delineates the ligand requirements for obtaining excellent regio- and enantioselectivity. Furthermore, the ability to utilize various electron-withdrawing groups, and to introduce quaternary carbon stereogenic centers, provides the level of versatility necessary for its application to target-directed synthesis. Additional studies on the development and application of this novel methodology to the total synthesis of natural products are currently underway. 相似文献
944.
Yan Tang Qing Lai Zhao Ke Zeng Pei Kai Miao Ke Zhou Wen Rui Tang Hong Fei Zhou Tao Liu Yi Peng Wang Gang Yang 《中国化学快报》2007,18(8):973-976
A novel benzoxazine monomer 3-(4-allyloxy)phenyl-3,4-dihydro-2H-6-(N-maleimido)-l,3-benzoxazine (AMB) was synthesized and structure was confirmed by FT-IR, 1H NMR. Thermal analysis (DSC) of AMB showed the introduction of allyloxy group melting point and exhibited a narrow and symmetric curing exothermic window. 相似文献
945.
The effect of the pristine sodium montmorillonite (Na+-MMT) on the styrene emulsion polymerizations with different concentrations of SDS ([SDS]) was investigated. At constant [SDS], the polymerization rate is faster for the run with 1 wt.% Na+-MMT compared to the counterpart without Na+-MMT. Micelle nucleation predominates in the polymerizations with [SDS] ≧ 13 mM. On the other hand, the contribution of the polymerization associated with the Na+-MMT platelets increases significantly when [SDS] decreases from 13 to 9 mM. At [SDS] (e.g., 2 mM) < CMC, homogeneous nucleation controls the particle formation process and polymerization kinetics. Moreover, the contribution of the Na+-MMT platelets that act as extra reaction loci to the polymerization kinetics is even comparable to the run in the absence of Na+-MMT. The resultant polymer particle size, polymer molecular weight and zeta potential were characterized and a preliminary model was developed to qualitatively study the differences between the polymerizations in the presence and absence of 1 wt.% Na+-MMT. 相似文献
946.
“消障灵”治疗早期老年性白内障疗效研究 总被引:1,自引:0,他引:1
对102例老年性白内障病人服药前后检测血中微量元素及红细胞酶活性.用高锌微量元素的中药内服,观察6个月~2年,结果视力增进70.5%;血锌提高1.6μg/mL(P值<0.001),血红细胞过氧化酶提高4.87IU/gHb(P值<0.001),血红细胞谷胱甘肽还原酶提高4.37IU/gHb(P值<0.001).说明锌对治疗早期老年性白内障有一定临床意义. 相似文献
947.
Huang HS Chiu HF Hwang JM Jen YM Tao CW Lee KY Lai YL 《Chemical & pharmaceutical bulletin》2001,49(10):1346-1348
The synthesis and cytotoxic evaluation of 9-acyloxy 1,8-dichloroanthracene derivatives are described. The system selectively reduces the carbonyl group flanked by the peri substituents of the anthracenediones to give the corresponding 1,8-dichloro-9(10H)-anthracenone. Simple acylation of anthracenone occurred with appropriate acyl chlorides in CH2Cl2 with a catalytic amount of pyridine to give the 9-acyloxy-1,8-dichloroanthracene derivatives. Considerable interest has developed in the mechanism of how anthracenones achieve this desirable selectivity. These compounds were evaluated in vitro for their ability to inhibit the growth of human oral epidermoid carcinoma cells (KB cell line), human cervical carcinoma cells of ME 180 (GBM 8401) and Chinese hamster ovary (CHO) cells, respectively, as compared to mitoxantrone. The in vitro cytotoxicity evaluation of 9-acyloxy 1,8-dichloroanthracenes against these above cell lines revealed for most of the compounds a cytotoxic potency lower than that of mitoxantrone. The most active compounds were thus selected for further in vitro biological evaluation and structural modification. 相似文献
948.
ShuFengZHANG QingLiQIAN PingLaiPAN YiCHEN GuoQingYUAN 《中国化学快报》2005,16(1):100-102
ANd promoted-Rh catalysts supported on polymer-derived carbon beads for vapor-phas emethanol carbonylation was developed. Rh-Nd bimetallic catalysts obviously have higher activity than that of supported Rh catalyst under similar reaction condition. The difference between the activity of above two catalyst systems is clearly caused by the intrinsic properties generated by the introduction of Nd. 相似文献
949.
Kun-Chun Hsieh Chun-Liang Lai Hon Man Lee Shie-Ming Peng 《Journal of organometallic chemistry》2004,689(21):3362-3369
A bis(diethylamido)hafnium compound [C4H3N(CH2NMe2)-2]2Hf(NEt2)2 (1) has been prepared in 79% yield by reacting Hf(NEt2)4 with 2 equiv. of [C4H3NH(CH2NMe2)-2] in heptane via deamination. Reacting compound 1 with 2 equiv. of phenyl isocyanate at room temperature in diethyl ether results in the PhNCO being inserted seletively into hafnium-NEt2 bonds to generate [C4H3N(CH2NMe2)-2]2Hf[PhNC(NEt2)O]2 (2) in 56% yield. Similarly, while reacting 1 with 2 equiv. of phenyl isocyanate for a week in toluene produces a mixture of 2 and [C4H3N(CH2NMe2)-2]Hf[PhNC(NEt2)O]3 (3). For comparison, reacting Hf(NEt2)4 with 4 equiv. of PhNCO in a toluene solution at room temperature results in the PhNCO inserted into Hf-N bonds, and forms a tetrakis-ureato hafnium compound Hf[PhNC(NEt2)O]4 (4) in 88% yield. A theoretical calculation found that the unpaired electrons of the ureato fragments of 2 are resonance delocalized between the C-O, C-NPh, and C-NEt2 bonds, which are all partially doubly bonded. 相似文献
950.
Lai‐Cai Li Jing Wang Xin Wang An‐Min Tian Ning‐Bew Wong 《International journal of quantum chemistry》2002,87(5):288-292
Ab initio calculations of the potential energy surface for the F + O3 and Cl + O3 reactions have been performed using the G3 and G3MP2 methods, which optimize the geometry configuration of reactants, products, intermediates, and transition states. The results show that fluorine atoms react with ozone as violently as chlorine atoms. At the same time, we have studied the reaction mechanisms of F atoms and Cl atoms with methane. It is found that fluorine atoms prefer to react with methane and chlorine atoms with ozone when there is competition between ozone and methane. Therefore, we can reasonably explain why chlorine atoms play the main role of reactants depleting ozone, while the more active fluorine atoms deplete less ozone. © 2002 Wiley Periodicals, Inc.; DOI 10.1002/qua.10119 相似文献