全文获取类型
收费全文 | 1005篇 |
免费 | 83篇 |
国内免费 | 40篇 |
专业分类
化学 | 780篇 |
晶体学 | 9篇 |
力学 | 30篇 |
综合类 | 1篇 |
数学 | 104篇 |
物理学 | 204篇 |
出版年
2023年 | 10篇 |
2022年 | 8篇 |
2021年 | 15篇 |
2020年 | 19篇 |
2019年 | 26篇 |
2018年 | 20篇 |
2017年 | 11篇 |
2016年 | 38篇 |
2015年 | 45篇 |
2014年 | 40篇 |
2013年 | 70篇 |
2012年 | 71篇 |
2011年 | 77篇 |
2010年 | 62篇 |
2009年 | 44篇 |
2008年 | 84篇 |
2007年 | 57篇 |
2006年 | 53篇 |
2005年 | 50篇 |
2004年 | 32篇 |
2003年 | 25篇 |
2002年 | 34篇 |
2001年 | 15篇 |
2000年 | 23篇 |
1999年 | 13篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 12篇 |
1993年 | 5篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 8篇 |
1985年 | 4篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1967年 | 4篇 |
1964年 | 2篇 |
1934年 | 2篇 |
排序方式: 共有1128条查询结果,搜索用时 468 毫秒
21.
Sun Y Irie M Kishikawa N Wada M Kuroda N Nakashima K 《Biomedical chromatography : BMC》2004,18(8):501-507
A highly sensitive HPLC method was developed for the determination of xenoestrogenic compound, bisphenol A (BPA) in human breast milk samples. After a two-step liquid-liquid extraction, BPA was derivatized with fluorescent labeling reagent, 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl). The excess fluorescent reagent could be removed effectively using a column-switching system. The separation of DIB-BPA from endogenous materials in milk was carried out on two C(18) columns and fluorescence intensity was monitored at 475 nm with the excitation of 350 nm. A good linearity (r = 0.994) was observed of BPA in the concentration range of 0.2-5.0 ng mL(-1) in breast milk, and the detection limit was 0.11 ng mL(-1) at a signal-to-noise ratio of 3. Intra- and inter-day precision (RSD, %) were less than 8.7 and 10.4, respectively. Twenty-three breast milk samples of healthy lactating women were analyzed for the BPA concentration; the mean value was 0.61 +/- 0.20 ng mL(-1), with no correlation to the lipid content of milk samples. 相似文献
22.
23.
24.
25.
Görgen JJ Comfort JR Tinsley JR Averett T DeKorse J Franklin B Ritchie BG Kyle G Klein A Berman B Burleson G Cranston K Faucett JA Jarmer JJ Knudson JN Penttilä S Tanaka N Brinkmöller B Dehnhard D Yen YF Hoibråten S Breuer H Flanders BS Khandaker MA Naples DL Zhang D Barlett ML Hoffmann GW Purcell M 《Physical review letters》1991,66(17):2193-2196
26.
Synthesis,characterization and antifungal activity of glycylglycine Schiff base complexes of 3d transition metal ions 总被引:1,自引:0,他引:1
Summary Two new Schiff bases, N-4-hydroxysalicylidene-glycylglycine (K·GGRS·H2O), N-O-vanillal-glycylglycine (K· GGVS·3H2O) and their manganese(II), cobalt(II), nickel(II) and copper(II) complexes have been synthesized and characterized by elemental analysis, t.g.a., molar conductance, i.r. and u.v. spectral studies. The 13Cn.m.r. spectrum of one of the Schiff base ligands has been recorded. The results show that the ligand is coordinated to the central metal ion via amide nitrogen, imino nitrogen, phenolic oxygen and carboxyl oxygen to form a quadridentate complexes. Some of the complexes exhibit strong inhibitory action towards Candida albicans and Cryptococcus neoformans. 相似文献
27.
Wang BB Zhang X Jia XR Li ZC Ji Y Yang L Wei Y 《Journal of the American Chemical Society》2004,126(46):15180-15194
PAMAM dendrimers of the zeroth to fifth generation (G0-5) have been peripherally modified with phenyl, naphthyl, pyrenyl, and dansyl chromophores. Their fluorescence behaviors are strongly affected by the dendritic architectures at different generations. These dendrimers modified with hydrophobic chromphores can self-organize into vesicular aggregates at the low generations G0-3 in water. The size and aggregation number of these vesicles decrease with increasing generation from G0 to G3. Critical aggregation concentration determined by fluorescence spectroscopy reveals that these aggregates can be favorably formed in the order of G3 > G2 > G1. In contrast to the vesicles made from traditional amphiphilic compounds, these dendrimer-based vesicles are very adhesive due to the H-bonding interaction and entanglement of dendritic branches located in the outer layer. A large number of multivesicle assemblies, i.e., "twins" and "quins" consisting of two and five vesicles, were clearly identifiable with transmission electron (TEM) and atomic force microscopy. For the dendrimers with peripheral pyrenyl chromophores, triangle-like vesicles were observed in water. The hydrophobic interphase thickness of the vesicular bilayer is ca. 2.0-3.2 nm determined by fluorescence resonance energy transfer methods, which agrees well with the thickness directly observed with TEM. 相似文献
28.
B. Bareika R. Danielius G. Dikchius R. Gadonas A. Piskarskas V. Sirutkaitis R. L. Fork C. V. Shank R. Yen C. Hirlimann W. J. Tomlinson P. Hříbek V. Kubeček M. Vrbová I. S. Ruddock R. Illingworth L. Reekie D. P. Weitekamp K. Duppen D. A. Wiersma 《Applied physics. B, Lasers and optics》1982,29(3):176-179
29.
30.
Chou HC Hsu CH Cheng YM Cheng CC Liu HW Pu SC Chou PT 《Journal of the American Chemical Society》2004,126(6):1650-1651
A molecular recognition concept exploiting multiple-hydrogen-bond fine-tuned excited-state proton-transfer (ESPT) was conveyed using 3,4,5,6-tetrahydrobis(pyrido[3,2-g]indolo)[2,3-a:3',2'-j]acridine (1a). The catalytic type 1a/carboxylic acids hydrogen-bonding (HB) complexes undergo ultrafast ESPT, resulting in an anomalously large Stokes shifted tautomer emission (lambdamax approximately 600 nm). Albeit forming a quadruple HB complex, ESPT is prohibited in the noncatalytic-type 1a/urea complexes (lambdamax approximately 430 nm). The HB configuration tuning ESPT properties lead to a feasible design for sensing multiple-HB-site analytes of biological interest. 相似文献