全文获取类型
收费全文 | 37821篇 |
免费 | 3197篇 |
国内免费 | 2550篇 |
专业分类
化学 | 25884篇 |
晶体学 | 447篇 |
力学 | 1576篇 |
综合类 | 235篇 |
数学 | 4139篇 |
物理学 | 11287篇 |
出版年
2024年 | 49篇 |
2023年 | 325篇 |
2022年 | 773篇 |
2021年 | 967篇 |
2020年 | 871篇 |
2019年 | 950篇 |
2018年 | 855篇 |
2017年 | 820篇 |
2016年 | 1336篇 |
2015年 | 1292篇 |
2014年 | 1733篇 |
2013年 | 2495篇 |
2012年 | 2850篇 |
2011年 | 3201篇 |
2010年 | 2237篇 |
2009年 | 2127篇 |
2008年 | 2753篇 |
2007年 | 2437篇 |
2006年 | 2441篇 |
2005年 | 2089篇 |
2004年 | 1769篇 |
2003年 | 1456篇 |
2002年 | 1534篇 |
2001年 | 1030篇 |
2000年 | 887篇 |
1999年 | 618篇 |
1998年 | 406篇 |
1997年 | 337篇 |
1996年 | 396篇 |
1995年 | 272篇 |
1994年 | 275篇 |
1993年 | 264篇 |
1992年 | 207篇 |
1991年 | 172篇 |
1990年 | 162篇 |
1989年 | 140篇 |
1988年 | 104篇 |
1987年 | 92篇 |
1986年 | 66篇 |
1985年 | 90篇 |
1984年 | 61篇 |
1983年 | 48篇 |
1982年 | 69篇 |
1981年 | 67篇 |
1980年 | 42篇 |
1979年 | 53篇 |
1978年 | 56篇 |
1976年 | 44篇 |
1975年 | 38篇 |
1974年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
61.
Taek‐Joong Kim Baoan Li May‐Britt Hgg 《Journal of Polymer Science.Polymer Physics》2004,42(23):4326-4336
Fixed‐site–carrier membranes were prepared for the facilitated transport of CO2 by casting polyvinylamine (PVAm) on various supports, such as poly(ether sulfone) (PES), polyacrylonitrile (PAN), cellulose acetate (CA), and polysulfone (PSO). The cast PVAm on the support was crosslinked by various methods with glutaraldehyde, hydrochloric acid, sulfuric acid, and ammonium fluoride. Among the membranes tested, the PVAm cast on polysulfone and crosslinked by ammonium fluoride showed the highest selectivity of CO2 over CH4 (>1000). The permeance of CO2 was then measured to be 0.014 m3 (STP)/(m2 bar h) for a 20 μm thick membrane. The effect of the molecular weight of PVAm and feed pressure on the permeance was also investigated. The selectivity increased remarkably with increasing molecular weight and decreased slightly with increased pressure in the range of 1 to 4 bar. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4326–4336, 2004 相似文献
62.
Tae Young Kim Dong Myung Kim Won Jung Kim Tae Hee Lee Kwang S. Suh 《Journal of Polymer Science.Polymer Physics》2004,42(15):2813-2820
The effect of the triblock copolymer poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) on the formation of the space charge of immiscible low‐density polyethylene (LDPE)/polystyrene (PS) blends was investigated. Blends of 70/30 (wt %) LDPE/PS were prepared through melt blending in an internal mixer at a blend temperature of 220 °C. The amount of charge that accumulated in the 70% LDPE/30% PS blends decreased when the SEBS content increased up to 10 wt %. For compatibilized and uncompatibilized blends, no significant change in the degree of crystallinity of LDPE in the blends was observed, and so the effect of crystallization on the space charge distribution could be excluded. Morphological observations showed that the addition of SEBS resulted in a domain size reduction of the dispersed PS phase and better interfacial adhesion between the LDPE and PS phases. The location of SEBS at a domain interface enabled charges to migrate from one phase to the other via the domain interface and, therefore, resulted in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2813–2820, 2004 相似文献
63.
DongXiangLI WanGuoHOU ShuPingLI MingTuHAO GaoYongZHANG 《中国化学快报》2004,15(2):224-227
The relation of the isoelectric point (IEP) and the point of zero net charge (PZNC) of the hydrotalcite-like compounds was discussed. It was found that the IEP does not equal to the PZNC and the IEP is higher than the PZNC. The structural positive charges existing in the HTlc,which cause the difference between the IEP and the PZNC. The effects of the structural positive charges of the HTlc on its IEP and PZNC are the same as the specific adsorption of metal cations. 相似文献
64.
A server needs to compute a broadcast schedule for n pages whose request times are known in advance. Outputting a page satisfies all outstanding requests for the page. The goal is to minimize the average waiting time of a client. In this paper, we show the equivalence of two apparently different relaxations that have been considered for this problem. 相似文献
65.
In this article we prove the existence of the solution to the mixed problem for Euler–Bernoulli beam equation with memory term. The existence is proved by means of the Faedo–Galerkin method and the exponential decay is obtained by making use of the multiplier technique combined with integral inequalities due to Komornik. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
66.
In this paper, we evaluate various analytic Feynman integrals of first variation, conditional first variation, Fourier-Feynman
transform and conditional Fourier-Feynman transform of cylinder type functions defined over Wiener paths in abstract Wiener
space. We also derive the analytic Feynman integral of the conditional Fourier-Feynman transform for the product of the cylinder
type functions which define the functions in a Banach algebra introduced by Yoo, with n linear factors. 相似文献
67.
该文利用算子半群的方法给出了取值于具有左不变度量的完备可分群的齐次Levy过程是复合Poisson过程的弱极限这一结论. 相似文献
68.
69.
Peptides containing azaglycine located terminally or within the backbone have been prepared in the solid phase by means of an automatic synthesizer. 相似文献
70.
Lizeng Wang Chengsong Ma Xiaoli Zhang Yibing Ren Yong Yu 《Fresenius' Journal of Analytical Chemistry》1995,351(7):689-691
The electrochemical behavior of the copper-tyrosine complex has been studied by linear-sweep adsorption voltammetry. In 0.02 mol/L Na2HPO4 buffer solution (pH=9.6), the complex can be adsorped on a hanging mercury drop electrode and reduced at a peak potential of about –0.42 V (vs. SCE). The secondary derivative peak height is linear proportional to the concentration of tyrosine in the range 1.0×10–7–5.0×10–5 mol/L. The detection limit is 5×10–8 mol/L.Project supported by the Provincial Science Foundation of Shandong Province 相似文献