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991.
通过异色满酮-4的克莱森缩合反应得到其α,β-不饱和衍生物,后者分别与3,5-二氨基-4-苯偶氮吡唑,3-氨基-1,2,4-三唑和2-氨基-苯并咪唑缩合,得到相应的四环和五环系列标题物。所合成的新化合物的结构均经元素分析,IR及^1H NMR确证。 相似文献
992.
L. Yu. Ukhin V. A. Kharlanov E. V. Solomovich O. V. Shishkin 《Russian Chemical Bulletin》1999,48(5):949-956
Salicylaldehyde aminals react with cyclohexanone upon heating to form tetrahydroxanthene derivatives. The structure of one
of these derivatives,viz., 5,7-dichloro-4a-morpholino-1,2,3,4-tetrahydro-4aH-xanthene, was established by X-ray diffraction analysis. The scheme of the reaction was suggested, which involves cycloaddition
of intermediateo-methylenequinone (from aminal) and enamine (from cyclohexanone). The reactions of salicylaldehyde aminals with enamines that
formed from cyclohexanone can successively afford derivatives of hexahydroxanthene, tetrahydroxanthene, and dihydroxanthene.
Procedures were developed for the synthesis of these compounds.N-Substituted 4a-amino-7-nitro-1,2,3,4-tetrahydro-4aH-xanthenes were also prepared by the reactions of dialkylammonium 2-formyl-4-nitrophenoxides with the above-mentioned enamines.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 959–965, May, 1999. 相似文献
993.
Summary One classical method for quantitation of amino acids in proteins is hydrolysis of the proteins and determination of the free
amino acids. Although the drastic experimental conditions necessary for complete hydrolysis always cause degradation of some
of the amino acids, if mild hydrolysis conditions are used, a mixture of amino acids and oligopeptides is obtained. If these
conditions are adequately tuned, the oligopeptides are almost exclusively dipeptides. For this reason we have initiated a
study to find a derivatizing agent suitable for the analysis of amino acids and dipeptides by an absolute method of quantitation
already tested for amino acids. FMOC-Cl was found to be a suitable derivatizing agent for this purpose. 相似文献
994.
E. Benichou A.R. Allouche R. Antoine M. Aubert-Frecon M. Bourgoin M. Broyer Ph. Dugourd G. Hadinger D. Rayane 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(2):233-242
A non perturbative approach is used to solve the problem of a rigid linear molecule with both a permanent dipole moment and
a static dipole polarizability, in a static electric field. Eigenenergies are obtained and compared to perturbative low field
and high field approximations. Analytical expressions for the orientation parameters and for the gradient of the energy are
given. This non perturbative approach is applied to the simulation of beam deviation experiments in strong electric field.
Results of simulations are given for inhomogeneous alkali dimers. For LiNa, the simulations are compared to experimental data.
For LiK, deviation profiles have been simulated in order to prepare future experiments on this molecule.
Received 21 July 1999 and Received in final form 22 September 1999 相似文献
995.
996.
Jiafeng Wang Jiale Wu Yinglong Han Jie Zhang Yu Lin Haijun Wang Jing Wang Jicheng Liu Ming Bu 《Molecules (Basel, Switzerland)》2021,26(21)
Two new series of betulin derivatives with semicarbazone (7a–g) or thiosemicarbazone (8a–g) groups at the C-28 position were synthesized. All compounds were evaluated for their in vitro cytotoxicities in human hepatocellular carcinoma cells (HepG2), human breast carcinoma cells (MCF-7), human lung carcinoma cells (A549), human colorectal cells (HCT-116) and normal human gastric epithelial cells (GES-1). Among these compounds, 8f displayed the most potent cytotoxicity with an IC50 value of 5.86 ± 0.61 μM against MCF-7 cells. Furthermore, the preliminary mechanism studies in MCF-7 cells showed that compound 8f could trigger the intracellular mitochondrial-mediated apoptosis pathway by losing MMP level, which was related with the upregulation of Bax, P53 and cytochrome c expression; the downregulation of Bcl-2 expression; activation of the expression levels of caspase-3, caspase-9, cleaved caspase-3 and cleaved caspase-9; and an increase in the amounts of intracellular reactive oxygen species. These results indicated that compound 8f may be used as a valuable skeleton structure for developing novel antitumor agents. 相似文献
997.
一氧化氮(nitric oxide,NO)在肿瘤病理生理过程中产生多方面的生化作用,诸如引起的某些核苷酸碱基的羟基化,参与免疫系统清除肿瘤细胞,促进肿瘤细胞凋亡和调节血管生成等.在此基础上,首次提出将NO供体(NO donor)或一氧化氮合酶(nitric oxide synthase,NOS)抑制剂分别连接到甲氨蝶呤(methotrexate,MTX,MTX本身就是NOS抑制剂)的α或γ位羧基上的设想,设计并合成出:(1)MTX-NO供体(3-羟甲基-4-苯基-1,2,5-噁二唑-2-氧化物,属于Furoxan衍生物,缩写为FU):1a(MTX-α-FU),2a(MTX-γ-FU);(2)MTX-NOS抑制剂(L-N^ω-硝基精氨酸或L-N^ω-硝基精氨酸甲酯):1b(MTX-α-L-N^ω-NO2-Arg),2b(MTX-γ-L-N^ω-NO2-Arg),1c(MTX-α-L-N^ω-NO2-Arg-OMe),2c(MTX-γ-L-N^ω-NO2-Arg-OMe).在生物活性测试中,我们选择耐MTX细胞株K-562(慢性粒细胞性白血病急性病变细胞株),进行抗肿瘤活性测试,得到以下结果:(1)脂溶性差的MTX衍生物1b,2b抗肿瘤活性低于MTX,其它1a,2a;1c,2c均优于MTX;(2)连接有NO供体的MTX明显增强了MTX衍生物的抗肿瘤活性;(3)MTX中谷氨酸γ位组合物抗肿瘤活性均高于相应的α位异构体的活性.以上初步结果,将对进一步研究NO抗肿瘤作用以及新的抗肿瘤药物设计提供新的思路,对肿瘤临床化疗也有一定的参考价值. 相似文献
998.
999.
1000.