全文获取类型
收费全文 | 11512篇 |
免费 | 542篇 |
国内免费 | 130篇 |
专业分类
化学 | 8031篇 |
晶体学 | 125篇 |
力学 | 554篇 |
综合类 | 3篇 |
数学 | 1449篇 |
物理学 | 2022篇 |
出版年
2024年 | 21篇 |
2023年 | 88篇 |
2022年 | 355篇 |
2021年 | 461篇 |
2020年 | 384篇 |
2019年 | 469篇 |
2018年 | 481篇 |
2017年 | 401篇 |
2016年 | 659篇 |
2015年 | 463篇 |
2014年 | 626篇 |
2013年 | 1167篇 |
2012年 | 898篇 |
2011年 | 824篇 |
2010年 | 618篇 |
2009年 | 509篇 |
2008年 | 560篇 |
2007年 | 490篇 |
2006年 | 362篇 |
2005年 | 364篇 |
2004年 | 230篇 |
2003年 | 224篇 |
2002年 | 180篇 |
2001年 | 110篇 |
2000年 | 77篇 |
1999年 | 84篇 |
1998年 | 55篇 |
1997年 | 63篇 |
1996年 | 72篇 |
1995年 | 48篇 |
1994年 | 56篇 |
1993年 | 29篇 |
1992年 | 47篇 |
1991年 | 43篇 |
1990年 | 40篇 |
1989年 | 44篇 |
1988年 | 48篇 |
1987年 | 42篇 |
1986年 | 38篇 |
1985年 | 45篇 |
1984年 | 43篇 |
1983年 | 29篇 |
1982年 | 33篇 |
1981年 | 24篇 |
1980年 | 28篇 |
1979年 | 25篇 |
1978年 | 27篇 |
1977年 | 22篇 |
1976年 | 22篇 |
1974年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 609 毫秒
31.
The stability of Ochratoxin A during its extraction using different extraction techniques has been evaluated. Microwave-assisted extraction and pressurised liquid extraction, in addition to two other reference methods of extraction, i.e. ultrasound-assisted and magnetic stirring-assisted extraction, were evaluated. The effect of extraction temperature using the cited techniques was checked.The results show that Ochratoxin A can be extracted using microwave-assisted extraction at temperatures up to 150 °C without degradation. Pressurised liquid extraction can be used at temperatures up to 100 °C, for extraction times of less than 30 min. Further, both ultrasound-assisted extraction and magnetic stirring extraction can be applied at temperatures up to 65 °C.High-performance liquid chromatography combined with fluorescence detection using a Chromolith RP-18e column at a flow rate of 5 mL min−1 was used to quantify the Ochratoxin A. The retention time for the Ochratoxin A was 1.3 min. The limits of detection (LOD) and of quantification (LOQ) were 0.03 and 0.10 μg L−1, respectively. 相似文献
32.
33.
Bahattin Gümgüm Nermin Biricik Feyyaz Durap Ismail Özdemir Nevin Gürbüz Wee Han Ang Paul J. Dyson 《应用有机金属化学》2007,21(8):711-715
Palladium(II) complexes with N,N‐bis(diphenylphosphino)aniline ligands catalyse the Heck reaction between styrene and aryl bromides, affording stilbenes in good yield. The structures of two of the complexes used as pre‐catalysts have been determined by single‐crystal X‐ray diffraction. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
34.
L.G. Casado I. García T. Csendes V.G. Ruíz 《Journal of Optimization Theory and Applications》2003,118(1):27-43
Based on the investigation carried out in Ref. 1, this paper incorporates new studies about the properties of inclusion functions on subintervals while a branch-and-bound algorithm is solving global optimization problems. It is found that the relative place of the global minimum value within the inclusion function value of the objective function at the current interval indicates mostly whether the given interval is close to a minimizer point. This information is used in a heuristic interval rejection rule that can save a considerable amount of computation. Illustrative examples are discussed and an extended numerical study shows the advantages of the new approach. 相似文献
35.
Vibsanin O, isolated from the leaves and twigs of Viburnum awabuki, is an unprecedented bicyclic diterpenoid. The structures of vibsanin O was established by extensive analysis of spectroscopic data. 相似文献
36.
Montgomery and Vaughan improved a theorem of Erd?s and Fuchs for an arbitrary sequence. Sárközy extended this theorem of Erd?s and Fuchs for two arbitrary sequences which are "near" in a certain sense. Using the idea of Jurkat (differentiation of the generating function), we will extend similarly the result of Montgomery and Vaughan for "sufficiently near" sequences. 相似文献
37.
Raed Ali Al-Khasawneh Fudziah Ismail Mohamed Suleiman 《Applied mathematics and computation》2007,190(2):1803-1814
In this paper, third-order 3-stage diagonally implicit Runge–Kutta–Nystrom method embedded in fourth-order 4-stage for solving special second-order initial value problems is constructed. The method has the property of minimized local truncation error as well as the last row of the coefficient matrix is equal to the vector output. The stability of the method is investigated and a standard set of test problems are tested upon and comparisons on the numerical results are made when the same set of test problems are reduced to first-order system and solved using existing Runge–Kutta method. The results clearly shown the advantage and the efficiency of the new method. 相似文献
38.
Marta Gimnez-Pedrs Ali Aghmiz Carmen Claver Anna M. Masdeu-Bult Denis Sinou 《Journal of molecular catalysis. A, Chemical》2003,200(1-2):157-163
High linear alkenes (1-octene and 1-decene) have been hydroformylated using water-soluble rhodium complexes associated with sulfonated diphosphines in the presence of ionic surfactants or methanol. In all cases, the hydroformylation activities were higher than in experiments without additives. The selectivity in aldehydes was higher when we used cetyltrimethylammonium hydrogensulfate (CTAHSO4) as the surfactant or methanol as the co-solvent. 相似文献
39.
Ali. Elamin. M. Saeed 《Annals of Differential Equations》2006,22(2):127-133
The purpose of this paper is to study a general Lienard type cubic system with one antisaddle and two saddles. We give some results of the existence and uniqueness of limit cycles as well as the evolution of limit cycles around the antisaddle for system (2) in the following when parameter a1 changes. 相似文献
40.
We find the existence of a quantum thermal effect, “Hawking absorption.” near the inner horizon of the Kerr–Newman black hole. Redefining the entropy, temperature, angular velocity, and electric potential of the black hole, we give a new formulation of the Bekenstein–Smarr formula. The redefined entropy vanishes for absolute zero temperature of the black hole and hence it is interpreted as the Planck absolute entropy of the KN black hole. 相似文献