全文获取类型
收费全文 | 58311篇 |
免费 | 12000篇 |
国内免费 | 15483篇 |
专业分类
化学 | 38819篇 |
晶体学 | 2418篇 |
力学 | 4896篇 |
综合类 | 2191篇 |
数学 | 8536篇 |
物理学 | 28934篇 |
出版年
2025年 | 244篇 |
2024年 | 1115篇 |
2023年 | 1342篇 |
2022年 | 2281篇 |
2021年 | 2270篇 |
2020年 | 2256篇 |
2019年 | 2211篇 |
2018年 | 1943篇 |
2017年 | 2677篇 |
2016年 | 2085篇 |
2015年 | 2859篇 |
2014年 | 3462篇 |
2013年 | 4536篇 |
2012年 | 4304篇 |
2011年 | 4490篇 |
2010年 | 4544篇 |
2009年 | 4742篇 |
2008年 | 5296篇 |
2007年 | 4700篇 |
2006年 | 4630篇 |
2005年 | 4036篇 |
2004年 | 3095篇 |
2003年 | 2247篇 |
2002年 | 2215篇 |
2001年 | 2248篇 |
2000年 | 2318篇 |
1999年 | 1326篇 |
1998年 | 734篇 |
1997年 | 582篇 |
1996年 | 561篇 |
1995年 | 468篇 |
1994年 | 541篇 |
1993年 | 491篇 |
1992年 | 437篇 |
1991年 | 310篇 |
1990年 | 310篇 |
1989年 | 350篇 |
1988年 | 270篇 |
1987年 | 214篇 |
1986年 | 173篇 |
1985年 | 129篇 |
1984年 | 126篇 |
1983年 | 135篇 |
1982年 | 115篇 |
1981年 | 93篇 |
1980年 | 71篇 |
1979年 | 64篇 |
1978年 | 25篇 |
1977年 | 18篇 |
1971年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
XU Guo-Yu ZHANG Gang-Shen YANG Gui-Chun CHEN Zu-Xing 《有机化学》2003,23(Z1):115-115
Libraries of peptide-like compounds are attractive sources of binding agents for proteomics applications. The synthesis of oligomeric combinatorial libraries of peptidomimetics is usually more straightforward than the creation of large libraries of more "drug-like" molecules. Herein we report synthesis of peptoids on soluble high loading Noncross-linked polystyrene. The synthesis route consists of: (a) preparation "soluble wang resin" from non-crosslinked polystyrene and 4-hydroxybenzyl alcohol via ether linkage, (b) an esterification step performed by the addition of bromoacetyl bromide to "soluble wang resin" and (c) a nucleophilic displacement of bromide with a primary amine. 相似文献
3.
CHEN Shuixia LIU Jinrong ZHANG Xiaoping ZENG Hanmin Materials Science Institute Zhongshan University Guangzhou Department of Environmental Science Engineering South China University of Technology Guangzhou P. R. China 《Chinese Journal of Reactive Polymers》2002,(2)
1. INTRODUCTION Microbial pollution will bring about various problems in industry and other vital fields, such as causing decomposing of materials, harming people抯 health. In order to reduce these problems, new antibacterial materials have been demanded. Recently, much attention has been paid to inorganic materials including zinc oxide [1~4]. These inorganic antibacterial materials are now substituting for organic materials to avoid releasing noxious organic molecules harmful to humans;… 相似文献
4.
A new chemiluminescence amplification reaction has been developed, which is on the coupling of the oxidation of Eosin by hydrogen peroxide under the catalysis of HRP at pH 3. 5 to the chemiluminescent reaction of luminol and hydrogen peroxide catalyzed by HRP at pH 10 to measure the activity of HRP and labelled-HRP. The detection limit of HRP is 10-10 g/mL. The lowest dilution ratio of HBsAb-HRP is 1 : 1. 8×102 and 1 : 106 for the direct method and coupled method respectively. 相似文献
5.
L. J. Ning Y. P. Wu L. Z. Wang S. B. Fang R. Holze 《Journal of Solid State Electrochemistry》2005,9(7):520-523
Three kinds of silicon-containing disordered carbons have been prepared by pyrolysis of polysiloxanes with different amounts of phenyl side groups. X-ray powder diffraction, X-ray photoelectron spectroscopy and electrochemical capacity measurements were performed to study their behaviors. Graphite crystallites, micropores, and silicon species affect their electrochemical performances. All of them present high reversible capacities, >372 mAh/g. Since the graphite crystallites are very small, they contribute very little to reversible capacity. The number of micropores produced by gas emission during the heat-treatment process decides whether they exhibit reversible capacity. Si mainly exists in the form C–Si–O and influences the irreversible capacity. There is no evident capacity fading in the first ten cycles, indicating promising properties for these disordered carbons. 相似文献
6.
IntroductionCatal}ticrcactionsaffcctcdb}'diffosionaIlimitationincatal}'stporcshavcbccnextensive1}dcaltx`ithinlit.rat.rcll~5I.Scvcraltcchniqucsonthcspccialcase0fFischcr-Tropschs}'nthcsis(FTS)t\crcapplicdtocxplorcthebchaviorofthiscatal}ticrcactionundercxpcrimcntalandopcrationaIconditionsI3~5l.It`"ouldbeofvaluctoindicatchcrcthatthcseinvcstigationsx"ercmainl}'bascdonthesimplcstkineticsofthcfirstordcrinH2proposedbyAndersonl6]attheearIystages.However-thesetboents,striCtlyspeaking,areinvalidfor… 相似文献
7.
Yuanyou Yang Ning Liu Shunzhong Luo Jiali Liao Jiannan Jin Taiming Zhang Pengji Zhao 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(3):659-663
Biosorption of 241Am by a fungus A. niger, including the spore and hyphae, was investigated. The preliminary results showed that the adsorption of 241Am by the microorganism was efficient. More than 96% of the total 241Am could be removed from 241Am solutions of 5.6-111 MBq/l (C
o) by spore and hyphaeof A. niger, with adsorbed 241Am metal (Q) of 7.2-142.4 MBq/g biomass, and 5.2-106.5 MBq/g, respectively. The biosorption equilibrium was achieved within 1 hour and
the optimum pH range was pH 1-3. No obvious effects on 241Am adsorption by the fungus were observed at 10-45 °C, or in solutions containing Au3+ or Ag+, even 2000 times above the 241Am concentration. The 241Am biosorption by the fungus obeys the Freundlich adsorption equation. There was no significant difference between the adsorption
behavior of A. nigerspore and hyphae.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
9.
Synthesis of lipid A derivatives and their interactions with polymyxin B and polymyxin B nonapeptide 总被引:5,自引:0,他引:5
Yin N Marshall RL Matheson S Savage PB 《Journal of the American Chemical Society》2003,125(9):2426-2435
Lipid A is the causative agent of Gram-negative sepsis, a leading cause of mortality among hospitalized patients. Compounds that bind lipid A can limit its detrimental effects. Polymyxin B, a cationic peptide antibiotic, is one of the simplest molecules capable of selectively binding lipid A and may serve as a model for further development of lipid A binding agents. However, association of polymyxin B with lipid A is not fully understood, primarily due to the low solubility of lipid A in water and inhomogeneity of lipid A preparations. To better understand lipid A-polymyxin B interaction, pure lipid A derivatives were prepared with incrementally varied lipid chain lengths. These compounds proved to be more soluble in water than lipid A, with higher aggregation concentrations. Isothermal titration calorimetric studies of these lipid A derivatives with polymyxin B and polymyxin B nonapeptide indicate that binding stoichiometries (peptide to lipid A derivative) are less than 1 and that affinities of these binding partners correlate with the aggregation states of the lipid A derivatives. These studies also suggest that cooperative ionic interactions dominate association of polymyxin B and polymyxin B nonapeptide with lipid A. 相似文献
10.
Synthesis, Structure and Conductivity of the New Charge-transfer Salt (ET)_2(CH_2=CH-CH_2-SO_3)·H_2O
Zhi LIU Qi FANG* Wen Tao YU Min Hua JIANG De Qing ZHANG Dao Ben ZHU State Key Laboratory of Crystal Materials Shandong University Jinan Institute of Chemistry The Chinese Academy of Sciences Beijing 《中国化学快报》2003,14(4)
ET is one of the most famous electron-donor molecules, which forms charge-transfer complexes (abbr. CT-complexes) with various types of counterions. These complexes have received intense attention because a wide range of physical properties such as conductivity and superconductivity1, ferromagnetism2-4 and nonlinear optical properties5 was found in these materials. Although the majority of the ET-based CT-complexes were prepared by combining with inorganic counterions, CT-complexes with o… 相似文献