全文获取类型
收费全文 | 1282篇 |
免费 | 43篇 |
国内免费 | 8篇 |
专业分类
化学 | 1047篇 |
晶体学 | 4篇 |
力学 | 6篇 |
数学 | 75篇 |
物理学 | 201篇 |
出版年
2023年 | 11篇 |
2021年 | 10篇 |
2020年 | 26篇 |
2019年 | 18篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 19篇 |
2015年 | 23篇 |
2014年 | 18篇 |
2013年 | 63篇 |
2012年 | 76篇 |
2011年 | 86篇 |
2010年 | 36篇 |
2009年 | 38篇 |
2008年 | 86篇 |
2007年 | 55篇 |
2006年 | 87篇 |
2005年 | 73篇 |
2004年 | 86篇 |
2003年 | 67篇 |
2002年 | 67篇 |
2001年 | 19篇 |
2000年 | 12篇 |
1999年 | 13篇 |
1998年 | 17篇 |
1997年 | 9篇 |
1996年 | 17篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 11篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1987年 | 5篇 |
1986年 | 11篇 |
1985年 | 26篇 |
1984年 | 17篇 |
1983年 | 11篇 |
1982年 | 16篇 |
1981年 | 13篇 |
1980年 | 6篇 |
1979年 | 21篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1975年 | 13篇 |
1974年 | 13篇 |
1973年 | 4篇 |
1972年 | 4篇 |
排序方式: 共有1333条查询结果,搜索用时 46 毫秒
1.
Homohelicity induction of a series of propylene-linked zinc bilinone (ZnBL; linear tetrapyrrople-zinc(II) complex) dimers upon complexation with chiral amine and α-amino esters was investigated. Introduction of substituents such as dimethyl and diisobutyl to the central carbon of the propylene spacer gave rise to stabilization of the homohelical (PP and MM) conformers rather than the heterohelical (PM) conformer. As bulkiness of the substituent increased, stability of the homohelical conformers was raised. The preorganization of the homohelical structures led to significantly amplified homohelicity induction upon complexation with chiral amine and α-amino esters. 相似文献
2.
The first aim in the present paper is to give an integral representation for Beppo Levi functions on R
n. Our integral representation is an extension of Sobolev's integral representation given for infinitely differentiable functions with compact support. As applications, continuity and differentiability properties of Beppo Levi functions are studied.Our second aim in this paper is to study the existence of limits at infinity for Beppo Levi functions. We also consider the existence of fine-type limits at infinity with respect to Bessel capacities, which yields the radial limit result at infinity. 相似文献
3.
4.
Takanori Ide Hiroshi Isozaki Susumu Nakata Samuli Siltanen Gunther Uhlmann 《纯数学与应用数学通讯》2007,60(10):1415-1442
Let a physical body Ω in ?2 or ?3 be given. Assume that the electric conductivity distribution inside Ω consists of conductive inclusions in a known smooth background. Further, assume that a subset Γ ? ?Ω is available for boundary measurements. It is proved using hyperbolic geometry that certain information about the location of the inclusions can be exactly recovered from static electric measurements on Γ. More precisely: given a ball B with center outside the convex hull of Ω and satisfying (B? ∩ ?Ω) ? Γ, boundary measurements on Γ with explicitly given Dirichlet data are enough to determine whether B intersects the inclusion. An approximate detection algorithm is introduced based on the theory. Numerical experiments in dimension two with simulated noisy data suggest that the algorithm finds the inclusion‐free domain near Γ and is robust against measurement noise. © 2007 Wiley Periodicals, Inc. 相似文献
5.
Bioavailability study of commercial sustained-release preparations of diclofenac sodium in gastrointestinal physiology regulated-dogs. 总被引:1,自引:0,他引:1
K Sagara Y Nagamatsu I Yamada M Kawata H Mizuta K Ogawa 《Chemical & pharmaceutical bulletin》1992,40(12):3303-3306
The gastrointestinal (GI) physiology of beagle dogs was regulated with a combined-treatment of intramuscular pentagastrin (10 micrograms/kg x 2) and intravenous atropine sulfate (0.02 mg/kg x 1). Here, the gastric acidity, the gastric emptying time and the small intestinal transit time in the regulated-dogs were respectively around pH 2, 0.7h and 4h, approximating those in healthy humans. The superiority of the regulated-dogs over the intact dogs was confirmed in comparative bioavailability studies by using two classes of commercial preparations. Both the conventional tablet and the sustained-release capsule of diclofenac sodium exhibited simple and similar average plasma concentration-time curves of free diclofenac in the intact dogs, while the latter preparation is reported to reveal a bimodal plasma curve of the drug in healthy humans. The regulated-dogs, however, permitted a bimodal average plasma pattern of the drug for the capsules due to an approximation of the GI physiology between humans and these classes of the dogs. The combined-treatment of beagle dogs with pentagastrin and atropine sulfate seems to supply a useful animal model in predicting the absorption characteristics of the sustained-release preparations and poor water-soluble drugs. 相似文献
6.
Susumu Ariki 《Advances in Mathematics》2004,181(1):134-159
This paper determines the representation type of the Iwahori-Hecke algebras of type B when q≠±1. In particular, we show that a single parameter non-semisimple Iwahori-Hecke algebra of type B has finite representation type if and only if q is a simple root of the Poincaré polynomial, confirming a conjecture of Uno's (J. Algebra 149 (1992) 287). 相似文献
7.
Liquid crystal lens with focus movable in focal plane 总被引:1,自引:0,他引:1
A liquid crystal lens with focus movable in the focal plane is reported. There are three electrodes in the cell. One electrode with a hole in the center is divided into four subelectrodes. The potential of each subelectrode is adjusted to produce a desired asymmetrical phase transformation resulting in off-axis movement of the focus. The potential of another electrode is adjusted to maintain the focus in the focal plane. Movements of the focus in three directions in the focal plane are demonstrated experimentally, and off-axis movement as large as approximately 800 μm is realized. 相似文献
8.
Calcium-induced alginate gel beads (Alg-Ca) containing various polysaccharides, including an alginate hydrolysate, were prepared and the drug release profiles were investigated. Hydrocortisone (HC) was gradually released from Alg-Ca into the mimic gastric fluid, while in intestinal fluid, it was quickly released with the dissolution of Alg-Ca. However, with Alg-Ca containing 5% chitin (CT), dissolution of Alg-Ca was not observed, and release of HC showed apparent zero-order kinetics. Furthermore, addition of the alginate hydrolysate altered the HC-release profile for Alg-Ca. 相似文献
9.
An antiviral nucleoside or virazole was synthesized efficiently and regioselectively starting with benzyl cyanoformate. 相似文献
10.
The first total synthesis of (+)?3-deoxyaphidicolin, a selective inhibitor of eukaryotic DNA polymerase α, has been completed efficiently and stereoselectively starting from 1-abietic acid. 相似文献