全文获取类型
收费全文 | 1009篇 |
免费 | 37篇 |
专业分类
化学 | 639篇 |
晶体学 | 22篇 |
力学 | 41篇 |
数学 | 57篇 |
物理学 | 287篇 |
出版年
2024年 | 4篇 |
2023年 | 15篇 |
2022年 | 29篇 |
2021年 | 21篇 |
2020年 | 32篇 |
2019年 | 24篇 |
2018年 | 29篇 |
2017年 | 36篇 |
2016年 | 37篇 |
2015年 | 20篇 |
2014年 | 55篇 |
2013年 | 99篇 |
2012年 | 78篇 |
2011年 | 70篇 |
2010年 | 57篇 |
2009年 | 55篇 |
2008年 | 51篇 |
2007年 | 54篇 |
2006年 | 32篇 |
2005年 | 25篇 |
2004年 | 33篇 |
2003年 | 9篇 |
2002年 | 17篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 13篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1967年 | 3篇 |
1962年 | 2篇 |
排序方式: 共有1046条查询结果,搜索用时 0 毫秒
81.
Nonlinear Dynamics - We consider the theoretical maximum extractable average power from an energy harvesting device attached to a vibrating table which provides a unidirectional displacement... 相似文献
82.
83.
Shailajan Sunita Hande Harshada Joshi Harshvardhan Tiwari Bhavesh Menon Sasikumar 《平面色谱法杂志一现代薄层色谱法》2014,27(1):23-28
JPC – Journal of Planar Chromatography – Modern TLC - Marmelosin is one of the major phytochemical constituents of Aegle marmelos (L.) Corr. (Rutaceae). Till date, there are no methods... 相似文献
84.
Ashutosh A. Patwardhan Laurence A. Belfiore 《Journal of Polymer Science.Polymer Physics》1986,24(11):2473-2486
The Flory–Huggins lattice-theory expression for solvent activity in a polymer-solution is commonly used to calculate the thermodynamic interaction parameter χ with the aid of experimental data from vapor pressure osmometry. This expression assumes that χ is independent of composition. However, experimental data for a variety of polymer-solvent mixtures indicate that χ exhibits an appreciable concentration dependence. A group contribution method, UNIFAC (UNIQUAC Functional-Group Activity Coefficients) incorporating the free-volume correction of Oishi and Prausnitz is used to predict the dependence of χ on solvent concentration. Agreement with previously reported experimental data is within 15%. Calculated values of χ obtained from the Flory–Huggins expression for solvent activity and from the corresponding Gibbs free energy of mixing (which does not assume that χ is independent of composition) are compared. Calculations based on the Gibbs free energy of mixing predict a somewhat larger value of χ relative to those based on solvent activity. The specific Gibbs free energy of mixing for polystyrene-solvent mixtures is calculated using the UNIFAC model, and is found to represent qualitatively the phase equilibrium behavior. Quantitative discrepancies are observed, however, for the polystyrene-acetone system in light of the actual experimental solubility reported by Suh and Clark (20). Most of the thermodynamic predictions for polymer-solvent systems investigated herein are correlated qualitatively with the relative mismatch between solubility parameters of both components. 相似文献
85.
A. K. Tiwari A. K. Rastogi B. Bhat 《International Journal of Infrared and Millimeter Waves》1986,7(6):833-844
The dispersion characteristics of a shielded suspended dielectric are computed using mode matching technique. From the dispersion characteristics the dielectric and conductor loss, quality factor and wave impedances are derived. The dimensions of shielded suspended dielectric are same as that of a rectangular metallic wave guide at Ka band. 相似文献
86.
The stereoselective synthesis of the C10–C24 fragment of (+)-cannabisativine has been achieved. The key steps involved in this strategy are the Sharpless asymmetric dihydroxylation, the diastereoselective allylation of an imine, and the ring closing metathesis (RCM). 相似文献
87.
The theory of fluid surfaces with elastic resistance to bending is applied to coexistent phase equilibria in biomembranes
composed of lipid bilayers. A simplified version of the model is used to simulate the necking and budding of closed vesicles.
相似文献
88.
Bhim Bali Prasad Khushaboo Tiwari Meenakshi Singh Piyush S. Sharma Amit K. Patel Shrinkhala Srivastava 《Chromatographia》2009,69(9-10):949-957
A combination approach in solid-phase microextraction, based on a molecularly imprinted polymer-brush coating on an optical fiber coupled with a complementary molecularly imprinted polymer sensor, has been adopted for isolation, preconcentration, and analysis of dopamine at ultratrace levels in highly dilute aqueous samples. This combination enabled enhanced (up to 8.5-fold) preconcentration of the analyte, which is appropriate for achieving a stringent detection limit in clinical diagnosis of several neurodegenerative diseases. The detection limit of dopamine in biological samples was 0.018 ng mL?1 with a relative standard deviation less than 2.1% and without any non-specific contributions. 相似文献
89.
Preparation of electrodeless discharge lamps for emission studies of uranium isotopes at trace level
G.K. Bhowmick R. Verma M.K. Verma V.A. Raman A.R. Joshi M.N. Deo L.M. Gantayet A.K. Tiwari K.L. Ramakumar Navin Kumar 《Spectrochimica Acta Part B: Atomic Spectroscopy》2010,65(12):1047-1051
A simplified method for preparation of electrodeless discharge lamp for uranium isotopes with specific concerns for 232U is described. Micro-gram quantities of solid uranium oxides and aqueous solution of uranium nitrate have been used as a starting material for in situ synthesis of uranium tetraiodide. High temperature iodination reaction is carried out in the presence of inert gas neon. By careful design, the preparation time and surface area of quartz reaction tubes have been reduced considerably. The latter decreases the level of contamination which has a direct bearing on the operational lifetime of the lamps. Incorporation of steps to purify the product from an unwanted material improved the stability of the lamps. The procedure provides a safe and convenient way of handling 232U in particular but can be extended in general to any actinides having radioactivity similar to that of freshly separated 232U. Characteristic emission of uranium isotopes have been recorded by Fourier Transform Spectrometer to show the satisfactory operation of the lamps as well as their usage for studying emission spectra of the specific isotope. 相似文献
90.
Mirza Saqib Baig Ashutosh Kumar Mohammad Imran Siddiqi Neena Goyal 《Journal of computer-aided molecular design》2010,24(1):77-87
Leishmania donovani dipeptidylcarboxypeptidsae (LdDCP), an angiotensin converting enzyme (ACE) related metallopeptidase has been identified and
characterized as a putative drug target for antileishmanial chemotherapy. The kinetic parameters for LdDCP with substrate,
Hip-His-Leu were determined as, Km, 4 mM and Vmax, 1.173 μmole/ml/min. Inhibition studies revealed that known ACE inhibitors
(captopril and bradykinin potentiating peptide; BPP1) were weak inhibitors for LdDCP as compared to human testicular ACE (htACE)
with Ki values of 35.8 nM and 3.9 μM, respectively. Three dimensional model of LdDCP was generated based on crystal structure
of Escherichia coli DCP (EcDCP) by means of comparative modeling and assessed using PROSAII, PROCHECK and WHATIF. Captopril docking with htACE,
LdDCP and EcDCP and analysis of molecular electrostatic potentials (MEP) suggested that the active site domain of three enzymes
has several minor but potentially important structural differences. These differences could be exploited for designing selective
inhibitor of LdDCP thereby antileishmanial compounds either by denovo drug design or virtual screening of small molecule databases. 相似文献