全文获取类型
收费全文 | 8478篇 |
免费 | 1260篇 |
国内免费 | 1751篇 |
专业分类
化学 | 7064篇 |
晶体学 | 177篇 |
力学 | 427篇 |
综合类 | 157篇 |
数学 | 976篇 |
物理学 | 2688篇 |
出版年
2024年 | 12篇 |
2023年 | 82篇 |
2022年 | 185篇 |
2021年 | 254篇 |
2020年 | 275篇 |
2019年 | 294篇 |
2018年 | 251篇 |
2017年 | 304篇 |
2016年 | 392篇 |
2015年 | 453篇 |
2014年 | 508篇 |
2013年 | 635篇 |
2012年 | 709篇 |
2011年 | 818篇 |
2010年 | 607篇 |
2009年 | 596篇 |
2008年 | 697篇 |
2007年 | 623篇 |
2006年 | 576篇 |
2005年 | 504篇 |
2004年 | 404篇 |
2003年 | 365篇 |
2002年 | 386篇 |
2001年 | 319篇 |
2000年 | 257篇 |
1999年 | 216篇 |
1998年 | 126篇 |
1997年 | 114篇 |
1996年 | 66篇 |
1995年 | 62篇 |
1994年 | 46篇 |
1993年 | 44篇 |
1992年 | 47篇 |
1991年 | 45篇 |
1990年 | 37篇 |
1989年 | 21篇 |
1988年 | 37篇 |
1987年 | 21篇 |
1986年 | 21篇 |
1985年 | 18篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1975年 | 4篇 |
1955年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
We will be mainly concerned with some important fiber spaces over Teichmüller spaces, including the Bers fiber space and Teichmüller
curve, establishing an isomorphism theorem between “punctured” Teichmüller curves and determining the biholomorphic isomorphisms
of these fiber spaces. 相似文献
992.
Using the first-principles methods we compute the electronic structure and the absorption spectra for a wurtzite CdSe (0001) slab covered with zincblende ZnSe and ZnS epilayers. For each structure we compute the DOS and the imaginary part of the dielectric function. We find that the semiconductor passivation shifts the ‘near Fermi-level’ states of the bare CdSe slab down to lower energy levels. The migration suggests the decrease of surface effects and energy loss. We observe the substantial reduction of the abnormal peaks in the absorption spectra of the bare CdSe slab, which seems to be a consequence of the DOS migration. This is consistent with the experimental results that a proper passivation enhance the luminescence efficiency. We also study the case that the epilayer surface is terminated with PH3 and find the PH3 passivation also reduces the surface state to some extent. 相似文献
993.
Shinn‐Horng Chen Yun Chen Chuen‐Shiou Shiau Cheng‐Jang Tsai 《Journal of polymer science. Part A, Polymer chemistry》2007,45(1):136-146
Aromatic triazole chromophores were incorporated into polyfluorene in an attempt to increase electron affinity, to promote emission efficiency, and to diminish excimer formation. Poly(9,9‐dihexylfluorene) ( P1 ) and new copolymers with aromatic triazoles ( P2 – P4 ) were prepared by Suzuki coupling polymerization. In P2 , the aromatic triazole (3.8 mol %) was attached exclusively as terminal groups, whereas P3 and P4 were main‐chain copolymers containing 3.9 and 10.3 mol % aromatic triazole chromophores, respectively. The copolymers were soluble in common organic solvents and showed high decomposition temperatures (437–458 °C). The twisted structure between the triazole and fluorene increased the emission efficiency and effectively prevented excimer formation in P2 – P4 . After the introduction of the triazole units, the absorption spectra showed a blueshift (from 388 to 381 nm in chloroform) due to confined conjugation, but the photoluminescence spectra remained almost the same (417–418 nm); this was attributed to oligofluorene segments. No emission of triazole fluorophores was observed because of efficient energy transfer from the triazole to oligofluorene segments. However, incomplete energy transfer was observed in CH3COOH. The optical stability upon thermal annealing was also improved by the incorporation of aromatic triazole segments. From cyclic voltammetry results, P2 – P4 , containing triazole groups, showed greater electron affinity (lowest unoccupied molecular orbital level = ?2.67 to ?2.71 eV) than P1 (?2.52 eV). Electroluminescence devices of P1 – P4 all exhibited excimer emissions (483–521 nm), which could also be diminished by the introduction of aromatic triazole chromophores. © 2006Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 136–146, 2007 相似文献
994.
Seung Yun Lee Hee Jin Kim Rajkumar Patel Se Joon Im Jong Hak Kim Byoung Ryul Min 《先进技术聚合物》2007,18(7):562-568
Microbial biofouling is one of the major obstacles for reaching the ultimate goal of realizing a high permeability over a prolonged period of nanofiltration operation. In this study, the hybrid nanocomposite membranes consisting of silver (Ag) nanoparticles with antibiofouling capability on microorganism and polyamide (PA) were prepared by in situ interfacial polymerization and characterized by X‐ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). The hybrid membranes were shown to possess the dramatic antibiofouling effect on Pseudomonas. In addition, Ag nanocomposite membranes had little influence on the performances of the membrane such as on water flux and salt rejection. SEM analysis results showed that all Pseudomonas were dead on the PA/Ag nanocomposite membrane, indicating the effectiveness of silver nanoparticles. This investigation offers a strong potential for possible use as a new type of antibiofouling membrane. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
995.
Guanjun Guo Yun Shao Yveping Nie Jingshan Jiang Heguang Liu 《International Journal of Infrared and Millimeter Waves》2003,24(5):789-797
Detection performance of the laser altimeter with avalanche photodiode has been analyzed and the studies indicate that the detection threshold applied to the discriminator has the decisive influence on the detection performance. Simulation shows that the primary photoelectron count produced by laser pulse returns and the average gain of APD determine the selection scope of the threshold, and also a method to select the threshold has been presented. 相似文献
996.
气相色谱—微波等离子体发射光谱法研究农药1605与人唾液的相互作用 总被引:3,自引:0,他引:3
用GC-AED联用技术研究了农药1605,得到1605所含六种元素的元素色谱图,并用该方法研究了人唾液与1605的相互作用。 相似文献
997.
998.
1-(2,6-二溴-4-硝基苯)-3-(4-硝基苯)-三氮烯与锌的显色反应研究 总被引:7,自引:1,他引:6
研究了 1- (2 ,6-二溴 - 4 -硝基苯 ) - 3- (4 -硝基苯 ) -三氮烯 (DBNPNPT)与锌的显色反应。在表面活性剂Triton X- 10 0的存在下 ,p H=9.0— 11.0的 Na2 B4 O7- Na OH介质中 ,DBNPNPT与锌 ( )可生成橙黄色络合物。建立以 5 35 nm为参比波长 ,4 4 0 nm为测定波长的双峰双波长测定法 ,该络合物的表观摩尔吸光系数为 1.34× 10 5L· mol-1· cm-1。对葡萄糖酸锌中的锌直接测定 ,结果令人满意 相似文献
999.
通过对氢化-1,3,5-均三嗪-2,4-二酮衍生物抗病毒活性QSAR计算,预测标题化合物具有较好抗病毒活性,由氢化-1,3,5-均三嗪-2,4-二酮、丙烯酸甲酯和乙二醇衍生物经三步反应合成这些化合物,新化合物经^1H NMR,IR,MS确认结构。 相似文献
1000.
介绍了与VISAR配合的加窗干涉仪测试技术。实验中分别采用样品表面和窗体表面作为信号光反射面,并用透明粘接剂粘接窗口和样品,得到厚度约为6 μm、对532 nm激光透过率不小于85%的粘接层。对窗体本身提出采用楔形的技术,有助于消除表面反射光和窗体寄生干涉对VISAR信号的干扰,从而提高信号的信噪比和测试可靠度。利用这一技术分别得到了6.5 GPa和3.61 GPa冲击压力下铜-LiF晶体窗口、LiF-LiF晶体窗口之间的界面速度变化过程。 相似文献