全文获取类型
收费全文 | 1742篇 |
免费 | 490篇 |
国内免费 | 751篇 |
专业分类
化学 | 1354篇 |
晶体学 | 64篇 |
力学 | 169篇 |
综合类 | 134篇 |
数学 | 235篇 |
物理学 | 1027篇 |
出版年
2023年 | 17篇 |
2022年 | 53篇 |
2021年 | 59篇 |
2020年 | 57篇 |
2019年 | 50篇 |
2018年 | 60篇 |
2017年 | 91篇 |
2016年 | 62篇 |
2015年 | 98篇 |
2014年 | 122篇 |
2013年 | 141篇 |
2012年 | 132篇 |
2011年 | 165篇 |
2010年 | 139篇 |
2009年 | 167篇 |
2008年 | 206篇 |
2007年 | 191篇 |
2006年 | 168篇 |
2005年 | 152篇 |
2004年 | 124篇 |
2003年 | 89篇 |
2002年 | 86篇 |
2001年 | 82篇 |
2000年 | 119篇 |
1999年 | 62篇 |
1998年 | 41篇 |
1997年 | 36篇 |
1996年 | 21篇 |
1995年 | 29篇 |
1994年 | 18篇 |
1993年 | 19篇 |
1992年 | 23篇 |
1991年 | 18篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1971年 | 1篇 |
1968年 | 2篇 |
1964年 | 1篇 |
1961年 | 3篇 |
1959年 | 1篇 |
排序方式: 共有2983条查询结果,搜索用时 0 毫秒
991.
Photoassociation of ultracold RbCs molecules into the (2)0- state (v = 189,190) below the 5S1/2 + 6P1/2 dissociation limit 下载免费PDF全文
Ultracold polar RbCs molecules are produced via photoassociation in a laser-cooled mixture of 85Rb and 133Cs atoms. The a 3Σ+ state molecules which decay from electronically excited (2)0- state RbCs molecules are detected by resonance-enhanced two-photon ionization. The new rovibrational levels (v = 189, 190) in the (2)0- state are also observed, which exist in theory and have not been observed in experiments yet. The corresponding rotational constants are measured by photoassociation spectroscopy, which are consistent with theoretical calculations using a nonrigid rotor model. 相似文献
992.
993.
994.
995.
NVP在全息聚合物分散液晶光栅中的反应动力学研究 总被引:1,自引:0,他引:1
为了提高全息聚合物分散液晶(简称HPDIC)光栅的衍射效率并得到良好的光栅表面形貌,在制备光栅的反应体系中添加了具有吡咯烷酮结构的单官能度小分子NVP,并进一步阐述了NVP对HPDLC光栅在反应动力学方面的影响.分析表明,NVP的添加显著增加了预聚单体的聚合速率,并且能使原本被困在聚合物网络当中的双键继续发生反应,从而大大提高了反应体系的双键转化率;另外,NVP的添加使得光栅的相分离更加彻底,在获得良好的表面形貌的同时也增大了光栅的折射率调制度,从而提高了HPDLC光栅的衍射效率.总之,在添加了NVP之后,体系的聚合速率和预聚单体的反应度都大大提高,从而使得光栅的表面形貌和衍射效率也得到较大的改善和提高,衍射效率提高到96.36%. 相似文献
996.
选用3种阴离子交换树脂A600、A600DL和D296R,研究了其对70%乙二醇-盐水混合体系中氯离子的静态吸附性能。结果表明,在20~40min内3种树脂对氯离子的吸附均可以达到吸附平衡,A600树脂吸附乙二醇-盐水混合体系中氯离子效果最佳,而且吸附过程中树脂用量少,吸附后样液中氯离子浓度即可达到相应标准。3种树脂吸附等温线按D-R吸附方程拟合最优。3种树脂吸附氯离子速率方程液膜扩散拟合曲线的线性关系较好,表明液膜扩散为树脂对乙二醇-盐水体系中氯离子吸附速率的主要控制步骤。再生性结果表明,在298K下,A600和A600DL树脂容易再生,而D296R树脂不易再生。通过红外光谱和拉曼光谱初步探讨了3种树脂的吸附机理,与静态吸附和再生研究结果相吻合。该研究将为天然气集输系统中的乙二醇盐水体系氯离子脱除提供理论基础。 相似文献
997.
Chemical investigation of the 70% ethanol extract of the unripe fruits of Forsythia suspensa resulted in the isolation of a novel caffeoyl phenylethanoid glycoside, lianqiaoxinoside B, together with the known compound forsythoside H. The new compound was elucidated to be 1',2'-[β-(3,4,-dihydroxylphenyl)-α,β-dioxoethanol]-3'-O-caffeoyl-O-α-rhamnopyranosyl-(1→6)-O-β-glucopyranoside by extensive spectroscopic and chemical studies. Lianqiaoxinoside B and forsythoside H showed strong antioxidant and antimicrobial activities in vitro by the 2,2'-azinobis-3-ethylbenzothiazoline-6-sulphonate (ABTS) radical-scavenging assay and plate method. This study can be further extended to exploit for the possible application of caffeoyl phenylethanoid glycosides as the alternative antioxidants and antimicrobial agents of natural origin. 相似文献
998.
Lin JQ Zheng YG Zhang HW Chen Z 《Langmuir : the ACS journal of surfaces and colloids》2011,27(13):8323-8332
Understanding the interactions of gold nanoparticles (AuNPs) with cellular compartments, especially cell membranes, is of fundamental importance in obtaining their control in biomedical applications. An effort is made in this paper to investigate the interactions of 2.2 nm core AuNPs with negative model bilayer membranes by coarse-grained (CG) molecular dynamics (MD) simulation. The CG model of lipid bilayer was taken from Marrink et al. ( J. Phys. Chem. B 2004, 108, 750-760 ), whereas the CG AuNPs model was developed on the basis of both atomistic MD simulations and experimental data. It was found that AuNPs functionalized with cationic ligands penetrated into the negative bilayer membranes and generated significant disruptions on bilayers. The lipids surrounding the nanoparticle were highly disordered and the bulk surface of the bilayer exhibits some defective areas. Most importantly, it is observed that a nanoscale hole can be formed and expanded spontaneously on the peripheral regions of the 20 × 20 nm bilayer. The expansion of the hole is on the time scale of hundreds of nanosceonds. The fully expanded hole had a radius of ~5.5 nm and could transport water molecules at a rate of up to ~1100 molecule/ns. However holes could not be formed on a larger bilayer (28 × 28 nm). The factors that can eliminate hole formation on the bilayer also include the decrease of cationic lignads on the AuNP, the reduction of negative lipids in the bilayer, the release of bilayer surface tension, the lowering of temperature, and the addition of a high concentration of salt. The results suggest that a hole can only be formed on living cell membranes under extreme conditions. 相似文献
999.
SHUN ZHOU WAN CUN XIN WANG YUN YU SHI 《Molecular physics》2013,111(6):901-912
An efficient procedure is introduced for a generalized Langevin dynamics simulation when the exponential model is taken for the friction kernel. The leap frog algorithm is used for numerical integration of the generalized Langevin equation. Simulation with this model has been performed on a cyclic undecapeptide, cyclosporin A (CPA). By comparison with the results obtained from previous simulations, the method proves to be reliable and efficient in the simulation of CPA. 相似文献
1000.
Yong-Feng Li Yan-Zhen Liu Wen-Zhong Shen Yong-Gang Yang Mao-Zhang Wang Yue-Fang Wen 《Applied Physics A: Materials Science & Processing》2012,106(4):779-784
Free-standing optoelectronic graphene–CdS–graphene oxide (G–CdS–GO) composite papers were prepared by vacuum-assisted self-assembly.
G–CdS hybrids were first prepared by a hydrothermal method and GO acts as a dispersant which makes it easier to disperse them
to form relatively stable aqueous suspensions for fabricating paper. Transmission electron microscopy shows that CdS quantum
dots (QDs) with an average size of approximately 1–2 nm were distributed uniformly on the graphene sheets. Photoluminescence
measurements for the as-prepared G–CdS–GO composite paper showed that the surface defect related emissions of attached CdS
QDs decrease and blue shift obviously due to the change in particle size and the interaction of the surface of the CdS QDs
with both the GO and the graphene sheets. The resulting paper holds great potential for applications in thin film solar cells,
sensors, diodes, and so on. 相似文献