全文获取类型
收费全文 | 1918篇 |
免费 | 58篇 |
国内免费 | 12篇 |
专业分类
化学 | 1284篇 |
晶体学 | 13篇 |
力学 | 41篇 |
数学 | 174篇 |
物理学 | 476篇 |
出版年
2023年 | 14篇 |
2022年 | 11篇 |
2021年 | 22篇 |
2020年 | 42篇 |
2019年 | 39篇 |
2018年 | 33篇 |
2017年 | 29篇 |
2016年 | 58篇 |
2015年 | 33篇 |
2014年 | 34篇 |
2013年 | 79篇 |
2012年 | 125篇 |
2011年 | 131篇 |
2010年 | 76篇 |
2009年 | 55篇 |
2008年 | 81篇 |
2007年 | 100篇 |
2006年 | 84篇 |
2005年 | 83篇 |
2004年 | 58篇 |
2003年 | 75篇 |
2002年 | 44篇 |
2001年 | 28篇 |
2000年 | 35篇 |
1999年 | 16篇 |
1997年 | 22篇 |
1996年 | 43篇 |
1995年 | 36篇 |
1994年 | 22篇 |
1993年 | 37篇 |
1992年 | 36篇 |
1991年 | 15篇 |
1990年 | 11篇 |
1989年 | 21篇 |
1988年 | 12篇 |
1987年 | 23篇 |
1986年 | 17篇 |
1985年 | 24篇 |
1984年 | 19篇 |
1983年 | 18篇 |
1982年 | 28篇 |
1981年 | 21篇 |
1979年 | 16篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 16篇 |
1974年 | 12篇 |
1973年 | 9篇 |
1972年 | 10篇 |
排序方式: 共有1988条查询结果,搜索用时 31 毫秒
51.
52.
53.
Abe F Albrow M Amidei D Anway-Wiese C Apollinari G Atac M Auchincloss P Azzi P Baden AR Bacchetta N Badgett W Bailey MW Bamberger A de Barbaro P Barbaro-Galtieri A Barnes VE Barnett BA Bauer G Baumann T Bedeschi F Behrends S Belforte S Bellettini G Bellinger J Benjamin D Benlloch J Bensinger J Beretvas A Berge JP Bertolucci S Biery K Bhadra S Binkley M Bisello D Blair R Blocker C Bodek A Bolognesi V Booth AW Boswell C Brandenburg G Brown D Buckley-Geer E Budd HS Busetto G Byon-Wagner A 《Physical review D: Particles and fields》1993,48(3):998-1008
54.
55.
Coleman KS Bailey SR Fogden S Green ML 《Journal of the American Chemical Society》2003,125(29):8722-8723
Single-walled carbon nanotubes have been cyclopropanated under Bingel reaction conditions, and the functionalized nanotubes have been characterized by atomic force microscopy using "chemical tagging" techniques. 相似文献
56.
Alloyed semiconductor quantum dots: tuning the optical properties without changing the particle size 总被引:7,自引:0,他引:7
Alloyed semiconductor quantum dots (cadmium selenium telluride) with both homogeneous and gradient internal structures have been prepared to achieve continuous tuning of the optical properties without changing the particle size. Our results demonstrate that composition and internal structure are two important parameters that can be used to tune the optical and electronic properties of multicomponent, alloyed quantum dots. A surprising finding is a nonlinear relationship between the composition and the absorption/emission energies, leading to new properties not obtainable from the parent binary systems. With red-shifted light emission up to 850 nm and quantum yields up to 60%, this new class of alloyed quantum dots opens new possibilities in band gap engineering and in developing near-infrared fluorescent probes for in vivo molecular imaging and biomarker detection. 相似文献
57.
Gianfranco Denti Mauro Ghedini Jon A. McCleverty Harry Adams Neil A. Bailey 《Transition Metal Chemistry》1982,7(4):222-224
Summary Treatment of [Mo{HB(3,5-Me2C3HN2)3}(NO)I2] with one or two moles of AgPF6 in acetonitrile afforded the paramagnetic (one unpaired electron) complex [Mo{HB(3,5-Me2C3NH2)3}(NO)(NCMe)2][PF6]. The structure of this complex was determined crystallographically, and the six-coordinate geometry of the complex cation confirmed. 相似文献
58.
E Bailey A G Brooks R Purchase M Meakings M Davies D G Walters 《Journal of chromatography. A》1987,421(1):21-31
An improved method has been developed for the determination of the major neutral steroids (cholesterol and 5 beta-cholestan-3 beta-ol) and unconjugated bile acids (deoxycholic acid and lithocholic acid) in human faeces, using capillary gas chromatography with flame ionization detection. The freeze-dried faecal sample was subjected to a two-stage Soxhlet extraction followed by an aqueous alkali-organic solvent partition step to separate neutral steroids from bile acids. The neutral steroids were analysed as their trimethylsilyl ether derivatives on an OV-1 capillary column. The bile acids were further purified on a Sep-Pak C18 cartridge and then fractionated on a Sep-Pak SIL cartridge. Unconjugated bile acids were analysed as their methyl ester-trimethylsilyl ether derivatives also on an OV-1 capillary column. Quantitation of neutral steroids and unconjugated bile acids was achieved by reference to appropriate internal standards, added to the faecal extract immediately after the Soxhlet extraction stage. The method is being used in a study of the effect of diet on the metabolic activity of human gut flora. 相似文献
59.
Kizek R Masarik M Kramer KJ Potesil D Bailey M Howard JA Klejdus B Mikelova R Adam V Trnkova L Jelen F 《Analytical and bioanalytical chemistry》2005,381(6):1167-1178
The electroanalytical determination of avidin in solution, in a carbon paste, and in a transgenic maize extract was performed in acidic medium at a carbon paste electrode (CPE). The oxidative voltammetric signal resulting from the presence of tyrosine and tryptophan in avidin was observed using square-wave voltammetry. The process could be used to determine avidin concentrations up to 3 fM (100 amol in 3 l drop) in solution, 700 fM (174 fmol in 250 l solution) in an avidin-modified electrode, and 174 nM in a maize seed extract. In the case of the avidin-modified CPE, several parameters were studied in order to optimize the measurements, such as electrode accumulation time, composition of the avidin-modified CPE, and the elution time of avidin. In addition, the avidin-modified electrode was used to detect biotin in solution (the detection limit was 7.6 pmol in a 6 l drop) and to detect biotin in a pharmaceutical drug after various solvent extraction procedures. Comparable studies for the detection of biotin were developed using HPLC with diode array detection (HPLC-DAD) and flow injection analysis with electrochemical detection, which allowed biotin to be detected at levels as low as 614 pM and 6.6 nM, respectively. The effects of applied potential, acetonitrile content, and flow rate of the mobile phase on the FIA-ED signal were also studied. 相似文献
60.
Joannie Chin Amanda Forster Lipiin Sung Kirk Rice 《Polymer Degradation and Stability》2007,92(7):1234-1246
In recent years, poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers have become prominent in high strength applications such as body armor, ropes and cables, and recreational equipment. The objectives of this study were to expose woven PBO body armor panels to elevated temperature and moisture, and to analyze the chemical, morphological and mechanical changes in PBO yarns extracted from the panels. A 30% decrease in yarn tensile strength, which was correlated to changes in the infrared peak absorbance of key functional groups in the PBO structure, was observed during the 26 week elevated temperature/elevated moisture aging period. Substantial changes in chemical structure were observed via infrared spectroscopy, as well as changes in polymer morphology using microscopy and neutron scattering. When the panels were removed to an ultra-dry environment for storage for 47 weeks, no further decreases in tensile strength degradation were observed. In a follow-on study, fibers were sealed in argon-filled glass tubes and exposed to elevated temperature; less than a 4% decrease in tensile strength was observed after 30 weeks, demonstrating that moisture is a key factor in the degradation of these fibers. 相似文献