全文获取类型
收费全文 | 7110篇 |
免费 | 1134篇 |
国内免费 | 728篇 |
专业分类
化学 | 4720篇 |
晶体学 | 72篇 |
力学 | 420篇 |
综合类 | 48篇 |
数学 | 658篇 |
物理学 | 3054篇 |
出版年
2024年 | 27篇 |
2023年 | 151篇 |
2022年 | 206篇 |
2021年 | 204篇 |
2020年 | 266篇 |
2019年 | 223篇 |
2018年 | 209篇 |
2017年 | 192篇 |
2016年 | 304篇 |
2015年 | 305篇 |
2014年 | 372篇 |
2013年 | 515篇 |
2012年 | 550篇 |
2011年 | 592篇 |
2010年 | 399篇 |
2009年 | 410篇 |
2008年 | 430篇 |
2007年 | 365篇 |
2006年 | 355篇 |
2005年 | 330篇 |
2004年 | 274篇 |
2003年 | 202篇 |
2002年 | 222篇 |
2001年 | 173篇 |
2000年 | 168篇 |
1999年 | 177篇 |
1998年 | 133篇 |
1997年 | 131篇 |
1996年 | 152篇 |
1995年 | 110篇 |
1994年 | 115篇 |
1993年 | 108篇 |
1992年 | 100篇 |
1991年 | 83篇 |
1990年 | 63篇 |
1989年 | 75篇 |
1988年 | 55篇 |
1987年 | 46篇 |
1986年 | 38篇 |
1985年 | 34篇 |
1984年 | 19篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1970年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有8972条查询结果,搜索用时 15 毫秒
931.
We have investigated the problem of teleporting a three-particle entangled W state and we propose a scheme based on entanglement spapping to complete the teleportation.We also put forward a scheme for the teleportation of a general W state by using nonmaximally entangled quantum channels.The probability of success of the latter scheme is obtained. 相似文献
932.
Chen GJ Gao CY Tian JL Tang J Gu W Liu X Yan SP Liao DZ Cheng P 《Dalton transactions (Cambridge, England : 2003)》2011,40(20):5579-5583
By changing the ratio of reactants, two mononuclear Dy complexes, [Dy(phen)(acac)(3)] (1) and [Dy(phen)(2)(NO(3))(2)(acac)]·H(2)O (2) have been synthesized and structurally characterized. In 1, a Dy atom bearing square-antiprism coordination geometry exhibits SMM behaviour, while compound 2 with a bicapped-square-antiprism geometry does not show such SMM properties. The different magnetic behaviours seen in 1 and 2 are probably due to a different coordination environment and ligand field around the Dy(III) ions. The results proved the important influence of the structural environment of a SMM on its magnetic behaviour. 相似文献
933.
含氨基,羟基吸附剂对胆红素的吸附 总被引:16,自引:0,他引:16
本文分别合成了含氨基和羟基的高分子吸附剂,并对它们对胆红素的吸附性能进行了研究。实验表明,经3小时的吸附后,含氨基和含羟基的吸附剂对胆红素的吸附率可达80%以上,对其吸附胆红素的性能和机理进行了探讨。 相似文献
934.
CdS nanoparticles were coated on the side wall of multiwalled carbon nanotubes (MWCNTs) by a wet chemical synthesis approach via noncovalent functionalization of MWCNTs with poly(diallyldimethylammonium chloride) (PDDA). The as-prepared material was characterized by X-ray diffraction (XRD), UV–vis absorption, fluorescence and transmission electron microscopy (TEM). The results indicated that CdS nanoparticles were uniformly coated on the surface of MWCNTs. Third-order optical nonlinearity of the as-prepared material was studied with the Z-scan technique with picosecond laser pulses at 532 nm. The Z-scan curve revealed that CdS nanoparticle-modified MWCNTs exhibited negative nonlinear refraction index and positive absorption coefficient. The real part and imaginary part of the third-order nonlinear susceptibility χ(3) were calculated to be −4.9 × 10−12 and 6.8 × 10−13 esu, respectively. 相似文献
935.
Gu R Depraetere S Kotek J Budka J Wagner-Wysiecka E Biernat JF Dehaen W 《Organic & biomolecular chemistry》2005,3(16):2921-2923
The first example of substitution reaction in the free alpha-position of N-confused calix[4]pyrroles is reported: azo-coupling with various arenediazonium salts. The obtained azocompounds were used for studies of their anion-binding properties by UV-Vis spectroscopy. 相似文献
936.
将聚四氟乙烯毛细管用聚乙烯醇交联涂层后,偶联上活性三嗪染料Cibacron BlueF3GA,制成一种新型的亲合染料Cibacron Blue F3GA修饰的聚四氟乙烯亲合毛细管。以牛血清白蛋白(BSA)作为模型蛋白进行在线富集和检测。方法依据亲合毛细管将低浓度的蛋白质溶液在线预富集后,以KSCN溶液洗脱并形成较高浓度的蛋白质溶液,用偶氮胂K光度法在线定量测定。PVA和Cibacron Blue F3GA的固载量分别为8.6μmol.g-1和0.434 mmol.g-1。毛细管容量为0.58 mg.cm-2BSA。这种分析系统适合微量和痕量蛋白质的在线富集和分析。对常见无机离子及有机物的干扰作了试验,结果表明方法的选择性较好。BSA的线性范围为0~200μg.L-1,检出限为1.5μg.L-1,方法用于水体中蛋白质的测定,回收率在99%~102%之间。 相似文献
937.
程序升温热重法研究扎赉诺尔煤的气化动力学 总被引:9,自引:0,他引:9
用程序升温热重法对扎赉诺尔煤(ZL)的800℃半焦进行CO2气化研究,考察了升温速率对TG/DTG谱图的影响,分析讨论了DTG参数(Tm和Rm)的变化;用单一升温速率法和多个升温速率组合法分别作了动力学计算,并对结果进行了分析讨论。结果表明:Tm和Rm均随升温速率的增高而增大,两种计算方法得到的动力学参数是不同的,单一升温速率法计算出的表观活化能E和指前因子A遵循关系式:logA=0.10E-8. 相似文献
938.
The intermediacy of ketenes in the intramolecular reaction of ketoacids with sodium acetate in acetic anhydride to form benzofurans is demonstrated. The Perkin reaction conditions are superior to the classical ketene generation method of triethylamine dehydrochlorination of the acid chloride. 相似文献
939.
Céline Guéguen Chad W. Cuss Weibin Chen 《International journal of environmental analytical chemistry》2013,93(13):1428-1440
Asymmetrical flow field-flow fractionation (AF4) with sequential on-line UV/visible and fluorescence detectors was used to investigate the composition of dissolved organic matter (DOM) in permeate and retentate fractions isolated by tangential flow ultrafiltration (TFF) at various concentration factors (i.e. ratio of initial volume to the retentate volume; CF). The permeation coefficient model, which defines the log-log relationship between DOM in the permeate fractions and CFs, described the permeation behaviour of DOM with regression coefficients r 2 > 0.99. The dominance of higher-molecular weight retentate chromophoric DOM (CDOM) observed in TFF was consistent with the results of AF4. The weight-averaged molecular weights (M w) of the integral permeate and retentate at CF = 20 were determined to be 1160 and 2320 by AF4, respectively, while their molecular weight distributions (MWD) were centered at 1120 and 1600 Da. M w, MWD, and aromaticity (i.e. ratio of absorbance at 250 and 365 nm; E2/E3) in permeate fractions were altered significantly during the early stages of TFF (CF < 9). These changes, however, were not evident in excitation-emission matrix fluorescence properties as determined using the parallel factor analysis model. The application of AF4 to TFF fractions suggests that the choice of CF may have an important impact on the size distribution and aromaticity of permeate fractions, whereas fluorescence properties appear insensitive to concentration factor. These results suggest that the choice of CF is crucial only in the study of the permeate fraction where similar CF (i.e. > 9) should be used to obtain meaningful comparison among samples. 相似文献
940.