全文获取类型
收费全文 | 15096篇 |
免费 | 2541篇 |
国内免费 | 1589篇 |
专业分类
化学 | 10396篇 |
晶体学 | 177篇 |
力学 | 960篇 |
综合类 | 127篇 |
数学 | 1763篇 |
物理学 | 5803篇 |
出版年
2024年 | 32篇 |
2023年 | 327篇 |
2022年 | 462篇 |
2021年 | 573篇 |
2020年 | 585篇 |
2019年 | 585篇 |
2018年 | 485篇 |
2017年 | 428篇 |
2016年 | 738篇 |
2015年 | 677篇 |
2014年 | 826篇 |
2013年 | 1053篇 |
2012年 | 1369篇 |
2011年 | 1343篇 |
2010年 | 1021篇 |
2009年 | 914篇 |
2008年 | 968篇 |
2007年 | 824篇 |
2006年 | 838篇 |
2005年 | 740篇 |
2004年 | 516篇 |
2003年 | 457篇 |
2002年 | 436篇 |
2001年 | 333篇 |
2000年 | 285篇 |
1999年 | 275篇 |
1998年 | 224篇 |
1997年 | 260篇 |
1996年 | 240篇 |
1995年 | 209篇 |
1994年 | 182篇 |
1993年 | 134篇 |
1992年 | 115篇 |
1991年 | 98篇 |
1990年 | 102篇 |
1989年 | 85篇 |
1988年 | 68篇 |
1987年 | 43篇 |
1986年 | 58篇 |
1985年 | 52篇 |
1984年 | 40篇 |
1983年 | 28篇 |
1982年 | 28篇 |
1981年 | 16篇 |
1980年 | 23篇 |
1979年 | 16篇 |
1978年 | 10篇 |
1976年 | 9篇 |
1975年 | 12篇 |
1972年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 562 毫秒
31.
Fang‐Chyou Chiu Sun‐Mou Lai Jong‐Wu Chen Pei‐Hsien Chu 《Journal of Polymer Science.Polymer Physics》2004,42(22):4139-4150
The melt mixing technique was used to prepare various polypropylene (PP)‐based (nano)composites. Two commercial organoclays (denoted 20A and 30B) served as the fillers for the PP matrix, and two different maleated (so‐called) compatibilizers (denoted PP‐MA and SMA) were employed as the third component. The results from X‐ray diffraction (XRD) and transmission electron microscope (TEM) experiments revealed that 190 °C was an adequate temperature for preparing the nanocomposites. Nanocomposites were achieved only if specific pairs of organoclay and compatibilizer were simultaneously incorporated in the PP matrix. For example, PP/20A(5 wt %)/PP‐MA(10 wt %) and PP/30B(5 wt %)/SMA(5 wt %) composites exhibited nanoscaled dispersion of 20A or 30B in the PP matrix. Differential scanning calorimetry (DSC) results indicated that the organoclays served as nucleation agents for the PP matrix. Generally, their nucleation effectiveness increased with the addition of compatibilizers. The thermal stability enhancement of PP after adding 20A was confirmed with thermogravimetric analysis (TGA). The enhancement became more evident as a suitable compatibilizer was further added. However, for the 30B‐included composites, thermal stability enhancement was not evident. The dynamic mechanical properties (i.e., storage modulus and loss modulus) of PP increased as the nanocomposites were formed; the properties increment corresponded to the organoclay dispersion status in the matrix. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4139–4150, 2004 相似文献
32.
Based on the complexation between proteins and Cu(II) coupled with the time-resolved chemiluminescence (CL) technique, a highly sensitive and quantitative assay for measuring proteins in solution is described. The complexes of proteins with Cu(II) have a strongly catalytic effect on the luminol-H2O2 CL reaction. Because the CL emission produced by the complexes is much more long-lived than that by Cu(II), the CL signals originating from proteins can be easily identified and measured with a time-resolved technique. On this basis, bovine albumin fraction V (BAF V) can be quantitatively determined in the range of 0.01 - 5.0 microg/ml with a detection limit of 5.8 ng/ml. The results show that the proposed assay exhibits a small variation in the response values for the same amount of different proteins, as compared to the Lowry as well as Bradford assays. The CL assay has also been studied for the detection of immobilized proteins. 相似文献
33.
34.
Jensen and Toft 8 conjectured that every 2‐edge‐connected graph without a K5‐minor has a nowhere zero 4‐flow. Walton and Welsh 19 proved that if a coloopless regular matroid M does not have a minor in {M(K3,3), M*(K5)}, then M admits a nowhere zero 4‐flow. In this note, we prove that if a coloopless regular matroid M does not have a minor in {M(K5), M*(K5)}, then M admits a nowhere zero 4‐flow. Our result implies the Jensen and Toft conjecture. © 2005 Wiley Periodicals, Inc. J Graph Theory 相似文献
35.
本文报道了在Zn0.76Cd0.24Se/ZnSe多量子阱(MQWs)中,用不同的Ar+激光线激发,观察到了共振增强的喇曼散射。首次在室温和77K的条件下,用Ar+的457.9nm谱线激发,观察到分别来自ZnSe垒层和Zn0.76Cd0.24Se阱层的限制纵光学声子模(LO)的喇曼散射,并对上述不同的光学模的起因进行了分析。 相似文献
36.
Lai Chunhui 《东北数学》1997,(1)
SomePropertiesofQuasi┐keep┐rangeOperatorsandTheirApplicationsLaiChunhui(赖春晖)(DepartmentofMathematics,ZhangzhouTeachersColege,... 相似文献
37.
38.
A nanoscale
multivalent platinum drug based on a poly(amidoamine) [PAMAM] dendrimer (generation
4.5, carboxylate surface) has been synthesized and fully characterized using
a variety of spectroscopic, chromatographic and thermal methods. Treatment
of the dendrimer with an aqueous solution containing an excess diaquo(cis-1,2-diaminocyclohexane)platinum(II) produces
a conjugate containing approximately forty (diaminocyclohexane)platinum(II)
moieties at the surface of the dendrimer. This material undergoes smooth two-stage
thermal decomposition to provide residual platinum oxide reflecting the platinum
loading in the drug. 相似文献
39.
On Polynomial Functions over Finite Commutative Rings 总被引:1,自引:0,他引:1
Jian Jun JIANG Guo Hua PENG Qi SUN Qi Fan ZHANG 《数学学报(英文版)》2006,22(4):1047-1050
Let R be an arbitrary finite commutative local ring. In this paper, we obtain a necessary and sufficient condition for a function over R to be a polynomial function. Before this paper, necessary and sufficient conditions for a function to be a polynomial function over some special finite commutative local rings were obtained. 相似文献
40.
A Bayesian approach is used to analyze the seismic events with magnitudes at least 4.7 on Taiwan. Following the idea proposed
by Ogata (1988,Journal of the American Statistical Association,83, 9–27), an epidemic model for the process of occurrence times given the observed magnitude values is considered, incorporated
with gamma prior distributions for the parameters in the model, while the hyper-parameters of the prior are essentially determined
by the seismic data in an earlier period. Bayesian inference is made on the conditional intensity function via Markov chain
Monte Carlo method. The results yield acceptable accuracies in predicting large earthquake events within short time periods. 相似文献