全文获取类型
收费全文 | 1530篇 |
免费 | 20篇 |
国内免费 | 104篇 |
专业分类
化学 | 1002篇 |
晶体学 | 1篇 |
力学 | 1篇 |
综合类 | 4篇 |
数学 | 5篇 |
物理学 | 392篇 |
综合类 | 249篇 |
出版年
2024年 | 8篇 |
2023年 | 84篇 |
2022年 | 29篇 |
2021年 | 25篇 |
2020年 | 23篇 |
2019年 | 18篇 |
2018年 | 15篇 |
2017年 | 29篇 |
2016年 | 24篇 |
2015年 | 41篇 |
2014年 | 46篇 |
2013年 | 128篇 |
2012年 | 140篇 |
2011年 | 113篇 |
2010年 | 52篇 |
2009年 | 68篇 |
2008年 | 58篇 |
2007年 | 94篇 |
2006年 | 82篇 |
2005年 | 66篇 |
2004年 | 66篇 |
2003年 | 45篇 |
2002年 | 47篇 |
2001年 | 41篇 |
2000年 | 34篇 |
1999年 | 27篇 |
1998年 | 21篇 |
1997年 | 24篇 |
1996年 | 23篇 |
1995年 | 38篇 |
1994年 | 28篇 |
1993年 | 13篇 |
1992年 | 23篇 |
1991年 | 16篇 |
1990年 | 14篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有1654条查询结果,搜索用时 734 毫秒
61.
Waganat W. Wardakhan Yehya M. Elkholy 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2661-2673
Several new thiazole derivatives have been synthesized; the reactivity of these compounds toward amines, aldehydes, and hydroxyl amine are reported. New syntheses of pyrimidino[5,4:3,4]pyrazolo[4,3:5,6]pyridazine derivatives also have been achieved. 相似文献
62.
Issa Yavari Abdolali Alizadeh Hamed Mohebbi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1741-1746
The reactive 1:1 intermediate produced in the addition reaction between trimethyl-phosphite and dibenzoylacetylene was trapped by SH- or NH-acids such as 4-nitroimidazole, 4-methyl-5-nitroimidazole, succinimide, or mercaptoacetic acid to produce 2-substituted 1,4-diphenylbutane-1,4-diones. 相似文献
63.
Maciej Makowski Krzysztof Pawełczak Paweł Kafarski Jolanta M. Dzik Barbara Gołos Małgorzata Balinska 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1639-1651
The synthesis of six analogues of the potent thymidylate synthase (TS) inhibitor N -[4-[ N -[(3,4-dihydro-2-methyl-4-oxo-6-quinazolinoyl)-methyl]- N -prop-2-ynylamino]benzoyl]- L -glutamic acid 2 is described in which the glutamic acid residue has been replaced by DL -aminophosphonic acids. New antifolates were tested as inhibitors of TS isolated from mouse L1210 leukemic cells as well as inhibitors of growth mouse leukemic L5178Y cells. In general these modifications result in compounds that are considerably less potent than 2 as TS inhibitors with K i 's 0.17-1.10 w M. Very poor solubility in water limited their proper assay of growth cells inhibition. 相似文献
64.
Antonio Alivert Jorge Bujons Juan-Julio Bonet 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):205-207
Abstract The treatment of 2-acetylthiophene with phosphorus pentachloride led, besides other products reported in previous studies, to 2-(2-thienyl)-2-chloroethenephosphonic acid in 16% yield. This compound was transformed, in the course of purification attempts, into 2-(2-thienyl)-2-oxoethanephosphonic acid. Full spectroscopic data for both compounds are provided. 相似文献
65.
Tatsuro Ouchi 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(3):417-429
Abstract The photopolymerization of triallylidene sorbitol (TAS) was carried out in benzene at 40°C without the usual initiator. The polymerization of TAS was found to be initiated with the ester radical generated via the acetal radical from TAS by means of photoirradiation. The rate of polymerization and the molecular weight of polymer were small due to the degradative chain transfer, It was kinetically investigated from the standpoints of the degradative chain transfer by the allylidene group and the cyclization by three double bonds. The following results were obtained: (1) The relation between the rate of polymerization, Rp, the monomer concentration, [M], could be expressed by [M] /Rp = (A[M] + B)/(3[M] + C), where A, B, and C were constant; (2) the ratio of the rate constant of unimolecular cyclization to the total rate constant of bimolecular propagation and the chain transfer of uncyclized radical was estimated to be 3.0 mol/dm3. A small amount of cyclopolymerization took place. 相似文献
66.
SYNTHESIS AND CHARACTERIZATION OF POLY(ASPARTIC ACID) AND ITS DERIVATIVES AS BIODEGRADABLE MATERIALS
TAKESHI NAKATO KYOKO ODA MASAKO YOSHITAKE MASAYUKI TOMIDA TOYOJI KAKUCHI 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(7-8):949-961
ABSTRACT Three types of modified poly(aspartic acid)s, such as poly(aspartic acid-co-aminocarboxylic acid) (4), alkylamine modified poly(aspartic acid) (5) and crosslinked poly(aspartic acid) (6), were synthesized and calcium-ion chelating ability, hygroscopicity and water absorption were evaluated. The calcium-ion chelating ability of 4 depended on the kind of aminocarboxylic acids and the content of aminocarboxylic acid in the copolymer. The highest value was 3 times higher than that of poly(acrylic acid) with a Mw of 14000. The highly modified PASP, e.g., 50 mol% lauryl amine modified poly(aspartic acid), showed the highest by grogroscopicity among homopoly(aspartic acid)s and modified poly(aspartic acid)s. The maximum swelling of poly(aspartic acid) hydrogel prepared by the γ-irradiation of homopoly(as-partic acid) was 3400 g-deionized water/g-dry hydrogel. 相似文献
67.
ABSTRACT A modified hyaluronic acid (HA) biopolymer was synthesized that can be photocrosslinked to form a stable hydrogel. The chemical and physical properties including the amount of modification of the polymer with methacrylate anhydride, the viscosity of the modified biopolymer, and the solute diffusion characteristics of the polymer have been determined. 相似文献
68.
Highly selective acylation of the alcoholic hydroxy group can be achieved with (hydroxyalkyl)phenols carrying both alcoholic and phenolic hydroxyls by the use of the most common acylating agents, acid chlorides, under microwave irradiation. 相似文献
69.
An expedient three‐step procedure for the synthesis of trichlorophenol derivatives based on the acid‐catalyzed rearrangement of the bicyclic ketone precursors 6a–e in high overall yield is described. The bicyclic ketone precursors 6a–e were obtained from Diels–Alder cycloadducts of β‐substituted vinyl acetates with tetrachloro‐5,5‐dimethoxycyclopentadiene in two steps. 相似文献
70.
A new and efficient method of converting acid hydrazides 1 to the corresponding N,N′‐diacylhydrazines 2 under microwave irradiation and in solvent‐free conditions has been described. 相似文献