全文获取类型
收费全文 | 2182篇 |
免费 | 54篇 |
国内免费 | 5篇 |
专业分类
化学 | 1555篇 |
晶体学 | 24篇 |
力学 | 39篇 |
数学 | 69篇 |
物理学 | 554篇 |
出版年
2023年 | 12篇 |
2022年 | 10篇 |
2021年 | 23篇 |
2020年 | 26篇 |
2019年 | 21篇 |
2018年 | 18篇 |
2017年 | 26篇 |
2016年 | 32篇 |
2015年 | 37篇 |
2014年 | 37篇 |
2013年 | 79篇 |
2012年 | 99篇 |
2011年 | 120篇 |
2010年 | 70篇 |
2009年 | 79篇 |
2008年 | 126篇 |
2007年 | 117篇 |
2006年 | 98篇 |
2005年 | 101篇 |
2004年 | 115篇 |
2003年 | 96篇 |
2002年 | 81篇 |
2001年 | 53篇 |
2000年 | 59篇 |
1999年 | 21篇 |
1998年 | 33篇 |
1997年 | 20篇 |
1996年 | 24篇 |
1995年 | 28篇 |
1994年 | 40篇 |
1993年 | 27篇 |
1992年 | 37篇 |
1991年 | 27篇 |
1990年 | 19篇 |
1989年 | 23篇 |
1988年 | 27篇 |
1987年 | 17篇 |
1986年 | 24篇 |
1985年 | 32篇 |
1984年 | 32篇 |
1983年 | 21篇 |
1982年 | 25篇 |
1981年 | 29篇 |
1980年 | 19篇 |
1979年 | 20篇 |
1978年 | 20篇 |
1977年 | 22篇 |
1976年 | 22篇 |
1975年 | 21篇 |
1974年 | 13篇 |
排序方式: 共有2241条查询结果,搜索用时 15 毫秒
51.
Yoshitaka Uenoyama Takahide Fukuyama Keisuke Morimoto Osamu Nobuta Hidefumi Nagai Ilhyong Ryu 《Helvetica chimica acta》2006,89(10):2483-2494
The carbonylation of alkanes 1 under radical‐reaction conditions was examined by using ethynyl triflone A as the unimolecular chain‐transfer (UMCT) reagent. Good to moderate yields of ethynyl ketones 2 were prepared by means of this three‐component coupling reaction. Higher CO pressures as well as lower concentrations of triflone A improved the efficiency of the reaction over the direct addition, the latter leading to alkylated ethynes 3 . In contrast to the reaction with A , the reaction of cyclohexane ( 1a ) with allyl triflone B (= ethyl 2‐methylene‐3‐[(trifluoromethyl)sulfonyl]propanoate) in the presence of CO gave a mixture of carbonylation products, including 8a formed from two molecules each of cyclohexane, CO, and allyl triflone B . 相似文献
52.
[structure: see text]. A fast, inexpensive, and highly efficient synthesis of aromatic polyamide dendrimers without the need for protection and deprotection steps has been developed. Dendrons and third-generation polyamide dendrimers were easily prepared by a convergent approach involving activation of a focal point with thionyl chloride, followed by condensation with unprotected AB2 building blocks. 相似文献
53.
Hitoshi?MatsukiEmail author Michio?Yamanaka Hiroshi?Kamaya Shoji?Kaneshina Issaku?Ueda 《Colloid and polymer science》2005,283(5):512-520
The dissociation equilibrium between uncharged local anesthetic lidocaine (LC) and charged local anesthetic LC (LCH+) in a surface-adsorbed film was investigated by measuring the surface tension and pH of aqueous solutions of a mixture of hydrochloric acid and LC. The surface tension values decreased slightly with increasing total molality mt at 0X20.5, where X2 is the mole fraction of LC in the mixture, while they decreased rapidly with increasing mt at 0.5<X21. It was shown from the pH measurements that almost all LC molecules were changed into LCH+ ions by protonation at 0X20.5 and both forms coexisted only at 0.5<X21. The quantities of the respective LC and LCH+ transferred from the aqueous solution to the adsorbed film, i.e., their surface densities, were calculated by applying the thermodynamic equations derived to the surface tension and pH data. A greater quantity of LC than LCH+ existed in the adsorbed film at the coexisting composition. The partitioning behavior of LC and LCH+ in the adsorbed film was characterized by three composition regions: (1) slight partitioning of low surface-active LCH+ in the region at 0X20.5, (2) preferential partitioning of LC at 0.5<X2<around 0.7, and (3) negative partitioning of LCH+ at around 0.7X21. The present results clearly indicate that uncharged local anesthetics transfer into hydrophobic environments such as cell membranes more than charged ones. 相似文献
54.
55.
Miyabe H Nishimura A Ueda M Naito T 《Chemical communications (Cambridge, England)》2002,(14):1454-1455
The indium-mediated allylation and alkylation reactions of the Oppolzer camphorsultam derivative of glyoxylic oxime ether proceeded with excellent diastereoselectivity in aqueous media, providing a variety of enantiomerically pure alpha-amino acids. 相似文献
56.
Suyama Kyozo Fukazawa Yoshitaka Umetsu Yoshiyaki 《Applied biochemistry and biotechnology》1994,(1):871-879
The egg shell membrane (ESM) is an intricate lattice network of stable and water-insoluble fibers with high surface area.
ESM accumulates and eliminates various heavy metal ions from dilute aqueous solution with high affinity and in short contact
time, depending on pH and characteristics of the individual ion. Under certain conditions, the level of precious ions, Au,
Pt, and Pd accumulation approaches 55, 25, and 22% of dry wt of ESM, respectively. Also uranium uptake 30% of that of ESM.
Experiments suggested that ESM is promising to use for the purpose of removal/recovery of metals and water pollution control. 相似文献
57.
Yoshitaka Koyama 《Communications in Mathematical Physics》1994,164(2):277-291
In this paper we give an explicit formula for level 1 vertex operators related to
as operators on the Fock spaces. We derive also their commutation relations. As an application we calculate with the vector representation of
, thereby extending the recent work on the staggered polarization of the XXZ-model. 相似文献
58.
59.
60.