全文获取类型
收费全文 | 2345篇 |
免费 | 103篇 |
国内免费 | 10篇 |
专业分类
化学 | 1706篇 |
晶体学 | 22篇 |
力学 | 73篇 |
数学 | 189篇 |
物理学 | 468篇 |
出版年
2023年 | 22篇 |
2022年 | 55篇 |
2021年 | 54篇 |
2020年 | 62篇 |
2019年 | 66篇 |
2018年 | 80篇 |
2017年 | 79篇 |
2016年 | 96篇 |
2015年 | 76篇 |
2014年 | 83篇 |
2013年 | 209篇 |
2012年 | 152篇 |
2011年 | 186篇 |
2010年 | 90篇 |
2009年 | 95篇 |
2008年 | 132篇 |
2007年 | 125篇 |
2006年 | 119篇 |
2005年 | 103篇 |
2004年 | 73篇 |
2003年 | 50篇 |
2002年 | 47篇 |
2001年 | 11篇 |
2000年 | 22篇 |
1999年 | 11篇 |
1998年 | 15篇 |
1997年 | 10篇 |
1996年 | 13篇 |
1995年 | 18篇 |
1994年 | 18篇 |
1993年 | 14篇 |
1992年 | 16篇 |
1991年 | 23篇 |
1990年 | 13篇 |
1989年 | 13篇 |
1988年 | 13篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 17篇 |
1984年 | 13篇 |
1983年 | 15篇 |
1982年 | 7篇 |
1981年 | 17篇 |
1980年 | 13篇 |
1979年 | 18篇 |
1978年 | 15篇 |
1977年 | 13篇 |
1976年 | 9篇 |
1974年 | 9篇 |
1973年 | 4篇 |
排序方式: 共有2458条查询结果,搜索用时 78 毫秒
101.
102.
103.
T. V. Subramanya Prasad C. R. Shahini Shivaputra A. Patil Xiaojun Huang 《Journal of Coordination Chemistry》2017,70(4):600-614
Various nitro/nitrile-functionalized benzimidazol-2-ylidene carbene complexes of silver(I) (7a–d and 11a–d) were synthesized by combination of 1-allyl/1-isopropyl/1-sec-butyl/1-isopentyl-3-(nitro/cyano-benzyl)-3H-benzimidazol-1-ium hexafluorophosphate (6a–d and 10a–d) with silver(I) oxide in acetonitrile. The compounds were characterized by 1H, 13C NMR, FT-IR, mass spectrometry, and elemental analysis. Additionally, the in vitro antibacterial activity of the N-heterocyclic carbene (NHC) precursors (6a–d and 10a–d) and their corresponding NHC-silver(I) complexes (7a–d and 11a–d) were investigated against Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli using the qualitative Kirby-Bauer disk diffusion method. All the NHC-silver(I) complexes exhibited medium-to-high antibacterial activity with areas of clearance ranging from 12 mm to 21 mm, while the NHC precursors were inactive against both strains of bacteria. 相似文献
104.
Metal quinolates, Liq Alq3 Znq2 Mgq2 exhibit efficient luminescence in blue green region and find applications as emission layer in OLEDs. In most of these quinolates the excitation spectra are broad in the range 350 to 410 nm, just short of emission spectra of efficient GaN based blue LEDs. In this paper we report metal quinolates synthesized by slightly modified method in which the excitation gets extended beyond 450 nm so that there is better overlap between emission spectra of blue LED and the excitation spectra. Therefore these phosphors may be used for PC-LED applications. 相似文献
105.
Ravindra Mahadev Patil Anil A. Ghanwat Satyanarayana Ganugapati 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(2):114-123
Well-defined four-arm star poly(?-caprolactone)-block-poly(cyclic carbonate methacrylate) (PCL-b-PCCMA) copolymers were synthesized by combining ring-opening polymerization (ROP) with atom transfer radical polymerization (ATRP). First, a four-arm poly(?-caprolactone) (PCL) macroinitiator [(PCL-Br)4] was prepared by the ROP of ?-CL catalyzed by stannous octoate at 110°C in the presence of pentaerythritol as the tetrafunctional initiator followed by esterification with 2-bromoisobutyryl bromide. The sequential ATRP of CCMA monomer was carried out by using the (PCL-Br)4 tetrafunctional macroinitiator (MI) and in the presence of CuBr/2, 2′-bipyridyl system in DMF at 80°C with [(MI)]:[CuBr]:[bipyridyl] = 1:1:3 to yield block polymers with controlled molecular weights (Mn (NMR) = 10700 to 27300 g/mol) by varying block lengths and with moderately narrow polydispersities (Mw/Mn = 1.2–1.4). Block copolymers with different PCL: PCCMA copolymer composition such as 50:50, 70:30 and 74:26 were prepared with good yields (48-74%). All these block copolymers were well characterized by NMR, FTIR and GPC and tested their thermal properties by DSC and TGA. 相似文献
106.
S. Vijay Kumar T. E. Musturappa S. Prasannakumar K. M. Mahadevan 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):1161-1169
Free radical copolymerization of N‐vinyl‐2‐pyrrolidone with 2‐ethoxyethyl methacrylates was carried out with 2,2′‐azobisisobutyronotrile as an initiator in 1,4‐dioxane. The resulting copolymer was characterized by FTIR, H1‐NMR and C13‐NMR spectroscopic techniques thermal properties of copolymer were determined by DSC and TGA. The reactivity ratios of the monomers were computed by the Fineman‐Rose (F‐R), Kelen‐Tudos (K‐T) and extended Kelen‐Tudos (EK‐T) method at lower conversion, using the data obtained from both FTIR and elemental analysis studies; the results are in good agreement with each other. The average reactivity ratio, Alfrey‐Price Q and e values were found to be r 1=0.769, r 2=0.266 and Q 1=0.0859, e 1=0.4508, respectively for NVP/EOEMA copolymer. The distribution of monomer sequence along the copolymer chain was calculated using a statistical method based on obtained reactivity ratio. The number average molecular weight and polydispersity were determined by GPC. 相似文献
107.
108.
109.
Rupali L. Magar Prashant B. Thorat Pratima B. Thorat Vinod V. Thorat Bhagawan R. Patil Rajendra P. Pawar 《中国化学快报》2013,24(12):1070-1074
The Biginelli-type compounds 4,5,8a-triarylhexahydropyrimido[4,5-d]pyrimidine-2,7(1H,3H)-diones were synthesized by a one-pot three-component reaction using sulfated tin oxide as a reusable catalyst. This method has the advantages of high yields, short reaction time, simple starting materials and reusability of catalyst for several times. 相似文献
110.
3′O-silylated derivatives of 5′-O-DMT-2′deoxynucleoside (2) were synthesized in high yield by reaction of 5′-O-DMT-2′-deoxynucleosides (1) with tert-butyl dimethylsilylchloride using sodium hydride, benzyltriethylammonlum chloride [TEBA] and a catalytic amount of dibenzo-[18]-crown-6 [DB-18-C-6] or 15-crown-5 [15-C-51 under mild reaction conditions. 相似文献