全文获取类型
收费全文 | 760篇 |
免费 | 31篇 |
专业分类
化学 | 447篇 |
晶体学 | 13篇 |
力学 | 24篇 |
数学 | 174篇 |
物理学 | 133篇 |
出版年
2023年 | 5篇 |
2022年 | 11篇 |
2021年 | 11篇 |
2020年 | 25篇 |
2019年 | 25篇 |
2018年 | 31篇 |
2017年 | 28篇 |
2016年 | 49篇 |
2015年 | 31篇 |
2014年 | 73篇 |
2013年 | 149篇 |
2012年 | 43篇 |
2011年 | 37篇 |
2010年 | 43篇 |
2009年 | 24篇 |
2008年 | 39篇 |
2007年 | 26篇 |
2006年 | 16篇 |
2005年 | 6篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 10篇 |
2001年 | 11篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1990年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 5篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1965年 | 2篇 |
1936年 | 1篇 |
排序方式: 共有791条查询结果,搜索用时 15 毫秒
761.
(–)—Crinine, C16H17NO3, is an alkaloid extracted from the bulbs of Pancratium maritimum L. (Amaryllidaceae). The compound crystallizes in the space group P212121 with cell dimensions a = 6.040(1), b = 12.382(1), c = 17.861(2) Å, with Z = 4. The molecule has five rings and an OH group. The N-containing, five-membered ring and the D ring have envelope conformations. The A and B rings have distorted chair and half-chair conformations, respectively. 相似文献
762.
Mihai Şabac 《Journal of Functional Analysis》1983,52(3):303-314
Some results concerning the operatorially irreducible, topologically irreducible, operatorially and topologically irreducible representations of a class of infinite-dimensional Lie algebras by bounded operators in a complex Banach space are obtained. 相似文献
763.
764.
765.
Ultrasound is known to enhance solid/liquid reactions. This paper deals with the investigation of the dissolution of phosphate rock in nitric acid, in the absence and presence of ultrasound. The reaction is first-order with respect to H+ and activation energy equal to 16 kJ/mol in both cases. The effect of ultrasound is on the pre-exponential factor A. An empirical relation is given, which relates rate constant to ultrasound power. 相似文献
766.
Avcıbaşı Uğur Demiroğlu Hasan Sakarya Serhan Ünak Perihan Tekin Volkan Ateş Buket 《Journal of Radioanalytical and Nuclear Chemistry》2018,316(1):275-287
Journal of Radioanalytical and Nuclear Chemistry - The aim of this study was to investigate the 131I and 127I labeled linezolid and moxifloxacin effects of minimum inhibitory concentration, and... 相似文献
767.
768.
Onur Şeref Wanpracha A. Chaovalitwongse J. Paul Brooks 《Annals of Operations Research》2014,216(1):229-255
We introduce a novel modification to standard support vector machine (SVM) formulations based on a limited amount of penalty-free slack to reduce the influence of misclassified samples or outliers. We show that free slack relaxes support vectors and pushes them towards their respective classes, hence we use the name relaxed support vector machines (RSVM) for our method. We present theoretical properties of the RSVM formulation and develop its dual formulation for nonlinear classification via kernels. We show the connection between the dual RSVM and the dual of the standard SVM formulations. We provide error bounds for RSVM and show it to be stable, universally consistent and tighter than error bounds for standard SVM. We also introduce a linear programming version of RSVM, which we call RSVMLP. We apply RSVM and RSVMLP to synthetic data and benchmark binary classification problems, and compare our results with standard SVM classification results. We show that relaxed influential support vectors may lead to better classification results. We develop a two-phase method called RSVM2 for multiple instance classification (MIC) problems, where RSVM formulations are used as classifiers. We extend the two-phase method to the linear programming case and develop RSVMLP2. We demonstrate the classification characteristics of RSVM2 and RSVMLP2, and report our classification results compared to results obtained by other SVM-based MIC methods on public benchmark datasets. We show that both RSVM2 and RSVMLP2 are faster and produce more accurate classification results. 相似文献
769.
In this article, we introduce the concept of lacunary statistical convergence of order α of real number sequences and give some inclusion relations between the sets of lacunary statistical convergence of order α and strong Nθα(p)-summability. Furthermore, some relations between the spaces NθαSθα are examined. 相似文献
770.
Ultrasonic pulse velocity (UPV) test is one of the most popular non-destructive techniques used in the assessment of the mechanical properties of concrete or rock materials. In this study, the effects of binder type/dosage, water to cement ratio (w/c) and fines content (<20 μm) of the tailings on ultrasonic pulse velocity (UPV) of cemented paste backfill (CPB) samples were investigated and correlated with the corresponding unconfined compressive strength (UCS) data. A total of 96 CPB samples prepared at different mixture properties were subjected to the UPV and UCS tests at 7, 14, 28 and 56-days of curing periods. UPV and UCS of CPB samples of ordinary Portland cement (CEM I 42.5 R) and sulphate resistant cement (SRC 32.5) initially increased rapidly, but, slowed down after 14 days. However, UPV and UCS of CPB samples of the blast furnace slag cement (CEM III/A 42.5 N) steadily increased between 7 and 56 days. Increasing binder dosage or reducing w/c ratio and fines content (<20 μm) increased the UCS and UPV of CPB samples. UPV was found to be particularly sensitive to fines content. UCS data were correlated with the corresponding UPV data. A linear relation appeared to exist between the UCS and UPV of CPB samples. These findings have demonstrated that the UPV test can be reliably used for the estimation of the strength of CPB samples. 相似文献