全文获取类型
收费全文 | 1644篇 |
免费 | 86篇 |
国内免费 | 5篇 |
专业分类
化学 | 1428篇 |
晶体学 | 9篇 |
力学 | 33篇 |
数学 | 125篇 |
物理学 | 140篇 |
出版年
2023年 | 24篇 |
2022年 | 28篇 |
2021年 | 58篇 |
2020年 | 62篇 |
2019年 | 58篇 |
2018年 | 39篇 |
2017年 | 47篇 |
2016年 | 79篇 |
2015年 | 78篇 |
2014年 | 80篇 |
2013年 | 119篇 |
2012年 | 151篇 |
2011年 | 150篇 |
2010年 | 100篇 |
2009年 | 90篇 |
2008年 | 110篇 |
2007年 | 109篇 |
2006年 | 79篇 |
2005年 | 70篇 |
2004年 | 44篇 |
2003年 | 37篇 |
2002年 | 32篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有1735条查询结果,搜索用时 31 毫秒
111.
Immunomagnetic separation and detection of Salmonella cells using newly designed carriers 总被引:1,自引:0,他引:1
Spanová A Rittich B Horák D Lenfeld J Prodelalová J Suciková J Strumcová S 《Journal of chromatography. A》2003,1005(1-2):215-221
A new method for simultaneous determination of alkoxyethanols (2-methoxyethanol, 2-ethoxyethanol, 2-isopropoxyethanol, and 2-butoxyethanol) by high-performance liquid chromatography (HPLC) with fluorescence detection has been developed. The alkoxyethanols and an internal standard (2-phenoxyethanol) were derivatized by treatment with 1-anthroylnitrile to give the anthroyl esters. The esterification was completed in 30 min in the presence of quinuclidine as base catalyst at room temperature. After stopping the reaction, an aliquot of the final solution was injected into the HPLC. The resulting anthroyl esters of the alkoxyethanols and the internal standard were separated on a C18 reversed-phase column with acetonitrile-water-acetic acid (65:35:0.1, v/v) as the mobile phase and detected fluorimetrically at excitation and emission wavelengths of 360 nm and 460 nm, respectively. The detection limits of the derivatives as alkoxyethanols at a signal-to-noise ratio of 3 were in the range of 1-3 pg per injection. The minimal amounts of alkoxyethanols derivatized in the reaction mixture for derivatization to determine the limits of detection were approximately 0.5 ng. This HPLC method was applied to the determination of some of alkoxyethanols in the air of the workplace where the thinner containing alkoxyethanols was used for painting. 相似文献
112.
Consider a special stable partition problem in which the player's preferences over sets to which she could belong are identical
with her preferences over the most attractive member of a set and in case of indifference the set of smaller cardinality is
preferred. If the preferences of all players over other (individual) players are strict, a strongly stable and a stable partition
always exists. However, if ties are present, we show that both the existence problems are NP-complete. These results are very
similar to what is known for the stable roommates problem.
Received: July 2000/Revised: October 2002
RID="*"
ID="*" This work was supported by the Slovak Agency for Science, contract #1/7465/20 “Combinatorial Structures and Complexity
of Algorithms”. 相似文献
113.
Krishna Dan Priya Rajdev Jolly Deb Siddhartha S. Jana Suhrit Ghosh 《Journal of polymer science. Part A, Polymer chemistry》2013,51(22):4932-4943
Synthesis of a library of amphiphilic random copolymers from a single reactive pre‐polymer and their self‐assembly is reported. Post‐polymerization modifications of the parent polymer containing pendant N‐hydroxy succinimide (NHS) ester groups with various oligooxyethylene (OE) amines produce amphiphilic random copolymers with same degree of polymerization and equal extent of randomness. 1H‐NMR and FT‐IR data indicate quantitative substitution in all cases. The critical aggregation concentration (CAC) for all the polymers is estimated to be in the range of 10?5 M. Stability of these nano‐aggregates is studied by photoluminescence using time dependent F—rster Resonance Energy Transfer (FRET) between co‐encapsulated lipophilic dyes namely DiO and DiI in the hydrophobic pocket of the aggregates. These studies suggest remarkably high stability for all systems. However those with shorter hydrophilic pendant chains are found to be even more robust. Morphology is examined by high resolution transmission electron microscopy (HRTEM) which reveals multi‐micellar clusters and vesicles for polymers containing short and longer OE segments, respectively. Encapsulation efficacy is tested with both hydrophobic and hydrophilic guest molecules. All of them can encapsulate hydrophobic guest pyrene while a hydrophilic dye Calcein can be sequestered only in vesicle forming polymers. Lower critical solution temperature (LCST) is exhibited by only one polymer that contains the shortest OE chains. All polymers exhibit excellent cell viability as determined by MTT assay. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4932–4943 相似文献
114.
115.
Jana Jurečková 《Statistics & probability letters》2010,80(23-24):1940-1946
The finite-sample distributions of the regression quantile and of the extreme regression quantile are derived for a broad class of distributions of the model errors, even for the non-i.i.d case. The distributions are analogous to the corresponding distributions in the location model; this again confirms that the regression quantile is a straightforward extension of the sample quantile. As an application, the tail behavior of the regression quantile is studied. 相似文献
116.
Kalyanmoy Jana Somnath Das Tithi Maity Maidul Hossain Subhas Chandra Debnath 《Journal of Coordination Chemistry》2018,71(10):1497-1509
A new Co(II) complex of general formula [Co(L)2] has been synthesized from a NNO tridentate Schiff base ligand, 2-[(piperidin-2-ylmethylimino)-methyl]-phenol (L). The title complex is characterized by elemental, spectroscopic, antibacterial, and single crystal X-ray structural studies. X-Ray crystallography reveals that the complex shows a distorted octahedral geometry around the Co(II) ion. The complex was tested against several bacteria and shows good antibacterial activities against almost all of the bacteria. The interactions of the title complex with calf thymus deoxyribonucleic acid (CT-DNA) have been investigated by electronic absorption and fluorescence spectroscopy, showing that the complex interacts with CT-DNA via partial intercalation. Thermogravimetric analysis (TGA) of the complex has also been reported and the result shows that the complex is thermally stable up to 134 °C. 相似文献
117.
Direct conversion of alkyl trimethylsilyl ethers to carbonyl compounds is accomplished using PFC in dichloromethane at room temperature. For a similar oxidation of t-butyldimethylsilyl ethers the PCC-n-Bu4NF combination may be employed. 相似文献
118.
We prove that a system of linear inequalities with interval-valued data is weakly solvable (each system obtained by fixing coefficeints in the intervals prescribed has a solution) if and only if it is strongly solvable (all such systems have a solution in common) and desribe an algorithm for checking strong solvability. 相似文献
119.
Nawel Cheikh Didier Villemin Nathalie Bar Jean-François Lohier Nourredine Choukchou-Braham Bachir Mostefa-Kara Jana Sopkova 《Tetrahedron》2013,69(3):1234-1247
In the course of our studies on Cerpegin analogues synthesis, a serendipitous reactivity of enaminolactone nitrile has been observed. Instead of expecting iminocerpegins, we have gained new class of substituted 2-aminopyridines. The methodology has been applied on a wide range of primary amines, as aliphatic, aromatic, heteroaromatic and also, diamines, hydrazines and chiral amines. 相似文献
120.
Heavy tailed durations of regional rainfall 总被引:1,自引:0,他引:1
Durations of rain events and drought events over a given region provide important information about the water resources of
the region. Of particular interest is the shape of upper tails of the probability distributions of such durations. Recent
research suggests that the underlying probability distributions of such durations have heavy tails of hyperbolic type, across
a wide range of spatial scales from 2 km to 120 km. These findings are based on radar measurements of spatially averaged rain
rate (SARR) over a tropical oceanic region. The present work performs a nonparametric inference on the Pareto tail-index of
wet and dry durations at each of those spatial scales, based on the same data, and compares it with conclusions based on the
classical Hill estimator. The results are compared and discussed.
The authors express sincere thanks to the Mathematisches Forschungsinstitut Oberwolfach (MFO) for facilitating their collaboration
under a “Research in Pairs” project hosted at MFO during March 5–25, 2006. The research of the second and third authors was supported by the project
LC06024. 相似文献