全文获取类型
收费全文 | 5916篇 |
免费 | 1029篇 |
国内免费 | 841篇 |
专业分类
化学 | 4694篇 |
晶体学 | 102篇 |
力学 | 306篇 |
综合类 | 34篇 |
数学 | 696篇 |
物理学 | 1954篇 |
出版年
2024年 | 21篇 |
2023年 | 109篇 |
2022年 | 181篇 |
2021年 | 213篇 |
2020年 | 275篇 |
2019年 | 285篇 |
2018年 | 229篇 |
2017年 | 204篇 |
2016年 | 327篇 |
2015年 | 330篇 |
2014年 | 375篇 |
2013年 | 491篇 |
2012年 | 523篇 |
2011年 | 561篇 |
2010年 | 396篇 |
2009年 | 361篇 |
2008年 | 373篇 |
2007年 | 309篇 |
2006年 | 317篇 |
2005年 | 239篇 |
2004年 | 240篇 |
2003年 | 178篇 |
2002年 | 227篇 |
2001年 | 169篇 |
2000年 | 114篇 |
1999年 | 106篇 |
1998年 | 66篇 |
1997年 | 66篇 |
1996年 | 48篇 |
1995年 | 36篇 |
1994年 | 51篇 |
1993年 | 30篇 |
1992年 | 26篇 |
1991年 | 36篇 |
1990年 | 30篇 |
1989年 | 26篇 |
1988年 | 32篇 |
1987年 | 14篇 |
1986年 | 15篇 |
1985年 | 20篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 6篇 |
排序方式: 共有7786条查询结果,搜索用时 15 毫秒
241.
242.
生长因子受体结合蛋白2(Grb2)在致癌基因Ras活化的信号传导通路中起着关键作用,目前被广泛认为是抗肿瘤药物设计的优秀靶标.对Grb2-SH2抑制剂的研究进展进行了综述,主要针对关键残基磷酸酪氨酸的高电荷性和多肽结构的低生物相容性两个缺陷,基于天然配体与Grb2-SH2相互作用的结构特征,围绕提高活性和简化结构开展的系统构效关系和合理结构优化研究,为进一步开发磷酸酪氨酸介导的Grb2-SH2抑制剂成为新型抗肿瘤药物提供结构和理论基础. 相似文献
243.
Qingwu Long Xiaoyan Deng Yujiao Gao Huayong Xie Hao Peng Hongwu He 《Phosphorus, sulfur, and silicon and the related elements》2013,188(7):819-825
Abstract A series of sodium hydrogen 1-(substituted phenoxyacetoxy) alkylphosphonates was designed and synthesized. The test for herbicidal activity indicated that most of the phosphonates (8) possessed excellent postemergence herbicidal activities against broadleaf weeds. Especially, 8f and 8g showed the best herbicidal activity against rape and amaranth with more than 95% inhibitory rate. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
244.
Martin Pomerantz Jiping Wang Seeyearl Seong Kyle P. Starkey Long Nguyen Dennis S. Marynick 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):507-508
Abstract Poly(benzo[1,2-b:4,5-b′]dithiophene-4,8-diyl vinylene) (1) has been prepared by the pyrolysis of the precursor polymer 2 and studied. Quantum mechanical calculations on the aromatic and quinoid monomers, oligomers and polymers indicate that 1 is a planar aromatic polymer. 相似文献
245.
Xiaoyan Deng Guihong Liao Qingwu Long Yujiao Gao Hao Peng Hongwu He 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6):663-671
Abstract A series of [(substituted phenoxyacetoxy)(substituted phenyl)methyl](methyl)phos- phinates containing fluorine were designed and synthesized. All the synthesized compounds were identified by elemental analysis, IR, 1H NMR, mass spectrometry. O-methyl [(2-fluorophenoxyacetoxy)(2,4-dichlorophenyl)methyl](methyl)phosphinate was further analyzed by X-ray single-crystal diffraction. Their herbicidal activity against a set of weed species was examined. Some of the compounds showed potential herbicidal activity, which provided some indications for further studies on structure modification. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
246.
Ling Gao Xiaoyan Deng Xiaosong Tan Qingwu Long Hao Peng Hongwu He 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):989-994
Abstract A series of 2-methylpropan-2-aminium methyl 1-(substituted phenoxyacetoxy) alkylphosphonates were selectively synthesized by reacting the corresponding dimethyl 1-(substitutedphenoxyacetoxy)alkylphosphonates with an excess of 2-methylpropan-2-amine. All the title compounds were identified by IR, 1H NMR, and 31P NMR, some of them were further analyzed by 19F NMR and 13C NMR. Their herbicidal activity was investigated and the results showed that most of the demethylated aminium salts exhibited notable herbicidal activities against Brassica napus L. and Echinochloa crusgalli. Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional text, figures and tables. 相似文献
247.
Dejiang Li Deqing Long Heqing Fu 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):519-526
1,3-bis[(3-aryl)-s-triazolo[3,4-b]-[1,3,4]thiadiazole-6-yl]benzenes 2 were synthesized in high yields by the reaction of 3-aryl 4-amino-5-mercapto-1,2,4-triazole 1 with m-phthalic acid. 相似文献
248.
Zhi-Jie Gao Yong-Chun Luo Zhen Lin Rong-Feng Li Jian-Yi Wang Long Kang 《Journal of Solid State Electrochemistry》2013,17(3):727-735
Hydrogen storage alloys La0.63Gd0.2?Mg0.17Ni3.35?x Co x Al0.15 (x?=?0, 0.1, 0.3, 0.5, 1.0, 1.5, 2.0) were prepared by induction melting followed by annealing treatment in argon atmosphere. The electrochemical properties of La0.63Gd0.2?Mg0.17Ni3.35?x Co x Al0.15 (x?=?0, 0.1, 0.3, 0.5, 1.0, 1.5, 2.0) alloy electrodes depended on the alloy structure type. XRD patterns and EPMA showed that the alloys consisted of Ce2Ni7-type (Gd2Co7-type), CaCu5-type, Pr5Co19-type, and PuNi3-type phase structure. Pr5Co19-type and Ce2Ni7-type phase increased with the increase of Co content x. However, CaCu5-type phase firstly decreased then increased as Co content increased. Rietveld analysis showed that the c-axis lattice parameters and cell volumes of the component phases increased with increasing Co content. The electrochemical measurements showed that as the Co content increased, the maximum discharge capacity and the cyclic stability of the annealed alloys both first increased and then decreased. The La0.63Gd0.2?Mg0.17Ni3.05Co0.3Al0.15 alloy electrode exhibited the maximum discharge capacity (392.92 mAh/g), and La0.63Gd0.2?Mg0.17Ni1.85Co1.5Al0.15 alloy electrode showed the best cyclic stability (S100?=?96.1 %). The electrochemical kinetics studies indicate that La0.63Gd0.2?Mg0.17Ni1.85Co1.5Al0.15 exhibited a higher rate dischargeability (HRD900?=?86.3 %). Electrochemical analyses showed that the control process of alloy electrode reaction is charge-transfer rate in surface film of alloy. 相似文献
249.
250.
The title complex l-[CuⅡ4(Hvap)2(vap)2(MeOH)2](CIO4)2 1 has been synthesized and characterized by EA. IR,TGA,solid-state CD spectra and X-ray single-crystal analyses(l-H2vap’.a Schiff base ligand derived from the condensation of o-vanillin and l-2-amino-3-phenyl-l-propanol).Complex 1 crystallizes in monoclinic system,chiral space group P21 with a =10.4257(18).b = 21.695(4),c = 15.721(3)A,β= 94.443(3).V= 3545.1(11) 3,Z=2,Cu4C70H78N4O22Cl2.Mr= 1652.42,Dc= 1.548 g/cm3, F(000)= 1704 andμ(MoKα) = 1.338 mm-1.The final R = 0.0682 and wR = 0.1420 for 6170 observed reflections with I > 2σ(I) and R = 0.1775 and wR = 0.1830 for all data.The structure of complex 1 contains a boat-shaped(Cu4O4} motif.The solid-state CD spectra confirm the chiral nature of complex 1. 相似文献