全文获取类型
收费全文 | 12853篇 |
免费 | 2094篇 |
国内免费 | 1343篇 |
专业分类
化学 | 7069篇 |
晶体学 | 85篇 |
力学 | 587篇 |
综合类 | 53篇 |
数学 | 1092篇 |
物理学 | 4068篇 |
无线电 | 3336篇 |
出版年
2024年 | 68篇 |
2023年 | 377篇 |
2022年 | 438篇 |
2021年 | 576篇 |
2020年 | 528篇 |
2019年 | 483篇 |
2018年 | 476篇 |
2017年 | 381篇 |
2016年 | 624篇 |
2015年 | 582篇 |
2014年 | 726篇 |
2013年 | 973篇 |
2012年 | 1130篇 |
2011年 | 1058篇 |
2010年 | 775篇 |
2009年 | 798篇 |
2008年 | 808篇 |
2007年 | 694篇 |
2006年 | 693篇 |
2005年 | 530篇 |
2004年 | 380篇 |
2003年 | 324篇 |
2002年 | 283篇 |
2001年 | 240篇 |
2000年 | 260篇 |
1999年 | 311篇 |
1998年 | 237篇 |
1997年 | 228篇 |
1996年 | 257篇 |
1995年 | 198篇 |
1994年 | 166篇 |
1993年 | 131篇 |
1992年 | 126篇 |
1991年 | 78篇 |
1990年 | 88篇 |
1989年 | 59篇 |
1988年 | 37篇 |
1987年 | 31篇 |
1986年 | 41篇 |
1985年 | 39篇 |
1984年 | 13篇 |
1983年 | 19篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
211.
Jianing Zhang Baolong Wang Liying Wang Junmin Sun Yongfeng Zhang Zhenzhu Cao Zhenqiang Wu 《应用有机金属化学》2018,32(2)
Low‐cost, highly active and versatile amino‐bis(phenolate) cobalt complexes are developed. The cobalt complexes can control living polymerization of different categories of monomers including lactide (LA) by immortal ring‐opening polymerization in argon and even in air and acrylate via living radical polymerization (LRP). The cobalt‐based catalysts were used for copolymerization of LA and acrylate. The immortal polymerization of LA using the cobalt complexes as initiators proceeds in argon and even in air and without the requirement for extensive drying techniques or inert atmosphere whilst retaining end‐group fidelity. The cobalt complexes are used to mediate LRP of t‐butyl acrylate (tBA) in methanol. The block copolymerization of LA and tBA catalyzed by single‐site cobalt organometallic catalyst is also reported for the first time. This cobalt system offers a versatile and green way to produce homopolymers and block copolymers. 相似文献
212.
Huimin Zhang Tingjun Zhong Mei Chen Lanying Zhang Xing Liu Hui Cao 《Liquid crystals》2018,45(8):1118-1128
Effects of the content of fluorinated alkene-terminated liquid crystal (LC) molecules on the physical properties of the fluorinated alkene-terminated LC/E8 mixture were studied. The morphology and electro-optical properties as they doped in polymer-dispersed liquid crystal (PDLC) films were investigated. The detailed discussion of the obtained results is given. As a result, comparing with the physical properties of the series of LC mixtures with the same content of the analogous fully saturated compounds doped with E8, we find that the birefringence is significantly larger for the LC mixture with the alkene-terminated materials. Both fluorinated alkene-terminated LC molecules and the analogous fully saturated compounds doped with E8 reduce the driving voltage of PDLC films. Moreover, PDLC films with the fluorinated alkene-terminated LC molecules possessed higher contrast ratio and faster response time than that of the PDLC films prepared by adding the same mass fraction of the analogous fully saturated compounds. Thus, the ability to manipulate physical properties of LC mixture and electro-optical properties of PDLC films by changing the LC molecular structures may have future relevance for new LC structures design and applications of PDLC films. 相似文献
213.
Bifunctional Fluorescent Probe for Sequential Sensing of Thiols and Primary Aliphatic Amines in Distinct Fluorescence Channels 下载免费PDF全文
Meiyu Huang Prof. Dr. Lingliang Long Ning Wang Xiangqi Yuan Siyu Cao Aihua Gong Prof. Dr. Kun Wang 《化学:亚洲杂志》2018,13(5):560-567
Thiols and primary aliphatic amines (PAA) are ubiquitous and extremely important species in biological systems. They perform significant interplaying roles in complex biological events. A single fluorescent probe differentiating both thiols and PAA can contribute to understanding the intrinsic inter‐relationship of thiols and PAA in biological processes. Herein, we rationally constructed the first fluorescent probe that can respond to thiols and PAA in different fluorescence channels. The probe exhibited a high selectivity and sensitivity to thiols and PAA. In addition, it displayed sequential sensing ability when the thiols and PAA coexisted. The application experiments indicated that the probe can be used for sensing thiols and PAA in human blood serum. Moreover, the fluorescence imaging of endogenous thiols and PAA as well as antihypertensive drugs captopril and amlodipine in living cells were successfully conducted. 相似文献
214.
N‐Heterocyclic Carbene‐Protected Ag Nanoparticles Immobilized on Polyacrylonitrile Fiber as Efficient Catalysts for a Three‐Component Coupling Reaction 下载免费PDF全文
Metal nanoparticles (NPs) are routinely stabilized by the introduction of capping agents or their distribution on supports. In this context, we report the preparation and characterization of N‐heterocyclic carbene (NHC)‐stabilized silver NPs supported on polyacrylonitrile fiber (PANF). As a result, Ag loadings of up to 8 % and particle sizes of 11.0±3.2 nm were achieved. This novel nanocomposite catalyst demonstrated high activity in addition to excellent stability and reusability in the three‐component reaction between alkynes, haloalkanes, and amines. In this system, the AgNPs were stabilized by both a support effect and a ligand effect. The unique NHC‐protected AgNP structure and the PANF support provide a synergistic effect in the deprotonation of Csp?H bonds, with turnover numbers of up to 3500. This catalyst was successfully recycled over eight runs without any significant loss in activity, and with no significant aggregation of the AgNPs. Moreover, implementation of a flow system with PANF‐NHC@Ag as catalyst leads to an efficient productivity of 57 mmol h?1. 相似文献
215.
SU Anmei WANG Di SHU Xin ZHONG Qingmei CHEN Yongren LIU Jiachen WANG Yilin 《高等学校化学研究》2018,34(2):164-168
Carbon quantum dots(CQDs) with a quantum yield of 11% were synthesized via a simple, low-cost and green hydrothermal treatment using dried lemon peel as carbon source. The obtained CQDs showed a strong emission at the wavelength of 505 nm with an optimum excitation of 425 nm. Carmine with maximum absorption wavelength at 508 nm could selectively quench the fluorescence of CQDs. Based on this principle, a fluorescence probe was developed for carmine determination. The quenching mechanism of CQDs was elucidated. A linear relationship was found in the carmine concentration range of 0.20—30.00 mg/L with the detection limit(3σ/k) of 0.16 mg/L. Satisfactory results were achieved when the method was applied for the determination of carmine in soft drinks. 相似文献
216.
A coumarin based highly selective fluorescent chemosensor for sequential recognition of Cu2+ and PPi
Xianjiao Meng Duanlin Cao Zhiyong Hu Xinghua Han Zhichun Li Dong Liang Wenbing Ma 《Tetrahedron letters》2018,59(49):4299-4304
In this study, we have successfully synthesized a new coumarin based fluorescent chemosensor 1, in which tren and quinolone are introduced as receptors for sequential recognition of Cu2+ and PPi. The structure of chemosensor 1 was characterized by 1H NMR, 13C NMR and ESI-HR-MS. Sensor 1 showed an obvious “on-off” fluorescence quenching response toward Cu2+, and the quenching efficiency reached a maximum of 99.6% with the addition of 20 equiv. of Cu2+. The 1-Cu2+ complex showed an “off-on” fluorescence enhancement response toward PPi over many competitive anions, especially HPO42? and H2PO4?. The detection limit of sensor 1 was 1.9?×?10?6?M to Cu2+ and 5.96?×?10?8?M to PPi. In addition, sensor 1 showed a 1:1 binding stoichiometry to Cu2+ and sensor 1-Cu2+ showed a 2: 1 binding stoichiometry to PPi in CH3CN/HEPES buffer medium (9:1 v/v, pH?=?7.4). The stable pH range of sensor 1 to Cu2+ and 1-Cu2+ to PPi was from 4 to 8. 相似文献
217.
Xiao-Ling Zhao Hong-Qi Zhang Bin Zhao Hong-Fei Guo Ji-Lin Cao 《Journal of solution chemistry》2018,47(9):1419-1437
The solubilities in the quaternary system K+, \( {\text{NH}}{_4^{+}} \)//Cl?, \( {\text{SO}}{_4^{2-}} \)–H2O and its two ternary subsystems NH4Cl–KCl–H2O, (NH4)2SO4–K2SO4–H2O at 80.0 °C were measured using the isothermal dissolution equilibrium method under atmospheric pressure, and the corresponding phase diagrams were plotted. In the phase diagram of the NH4Cl–KCl–H2O system, there are three crystalline zones, which correspond to (K1?m,(NH4)m)Cl, ((NH4)n,K1?n)Cl and the co-existence zone of (K1?m,(NH4)m)Cl and ((NH4)n,K1?n)Cl, respectively. In the phase diagram of the (NH4)2SO4–K2SO4–H2O system, there is only one crystalline zone for (K1?t,(NH4)t)2SO4. In the phase diagram of the K+, \( {\text{NH}}{_4^{+}} \)//Cl?, \( {\text{SO}}{_4^{2-}} \)–H2O system, there are three crystal zones, which correspond to (K1?t,(NH4)t)2SO4, (K1?m,(NH4)m)Cl and ((NH4)n,K1?n)Cl, respectively. According to the analysis and the calculations for the phase diagrams of the K+, \( {\text{NH}}{_4^{+}} \)//Cl?, \( {\text{SO}}{_4^{2 -}} \)–H2O system at 80.0 °C and 50.0 °C, this paper proposes a technological process. In the process, the (K1?t,(NH4)t)2SO4 can be prepared at 80.0 °C and the ((NH4)n,K1?n)Cl can crystallize out at 50.0 °C. The mass fraction of K2SO4 in product L1 (K1?t,(NH4)t)2SO4 (t?=?0.1465) is 88.48%. The composition of solid solutions in the K+, \( {\text{NH}}{_4^{+}} \)//Cl?, \( {\text{SO}}{_4^{2 -}} \)–H2O system was experimentally determined and then theoretical calculations about the process can be carried out. 相似文献
218.
Qin?Xue Xuanyu?Cao Cuiling?Zhang Yuezhong?XianEmail authorView authors OrcID profile 《Mikrochimica acta》2018,185(4):231
The authors describe an environmentally friendly and fast (~14 min) method for the synthesis of homogeneously distributed fluorescent polydopamine nanodots (PDA-NDs) using KMnO4 as the oxidant. Alkaline phosphatase (ALP) catalyzes the hydrolysis of ascorbic acid 2-phosphate to release free ascorbic acid which undergoes an in-situ redox reaction with KMnO4. Depending on the activity of ALP, more or less KMnO4 is consumed, and this affects the formation of the PDA-NDs. Based on this finding, a sensitive method was worked out to quantify the activity of ALP via real-time formation of fluorescent PDA-NDs. The fluorometric signal (best measured at excitation/emission peaks of 390/500 nm) is linear in the 1 to 50 mU·mL?1 ALP activity range, and the limit of the detection is as low as 0.94 mU·mL?1 (based on 3 σ/m). The method was successfully applied to the determination of ALP activity in spiked human serum and in MCF-7 cell lysates. It was also applied in a method to screen for inhibitors of ALP. 相似文献
219.
Under visible-light irradiation, a cathodic photoelectrochemical (PEC) sensor is presented for highly sensitive determination of Cr(VI) at a potential of ?0.25 V (vs SCE). PbS quantum dots (QDs) were capped with mercaptoacetic acid and assembled on the surface of an indium tin oxide (ITO) electrode via the linker poly(diallyl dimethyl ammonium chloride) providing a photoactive sensor. Cr(VI) accepts the photoelectrons generated by the PbS QDs. This promotes the separation of electron holes and enhances the cathodic photocurrent generated by a 470-nm LED. The sensor has 10 pM detection limit and a linear working range from 0.02 nM to 2 μM of chromate. The method was successfully applied to the determination of Cr(VI) and total chromium in spiked environmental water samples. 相似文献
220.
Dr. Benjamin A. Chalmers Hui Xing Sevan Houston Dr. Charlotte Clark Dr. Sussan Ghassabian Dr. Andy Kuo Benjamin Cao Andrea Reitsma Cody‐Ellen P. Murray Dr. Jeanette E. Stok Dr. Glen M. Boyle Carly J. Pierce Stuart W. Littler Prof. David A. Winkler Prof. Paul V. Bernhardt Dr. Cielo Pasay Prof. James J. De Voss Prof. James McCarthy Prof. Peter G. Parsons Prof. Gimme H. Walter Prof. Maree T. Smith Prof. Helen M. Cooper Prof. Susan K. Nilsson Dr. John Tsanaktsidis Dr. G. Paul Savage Prof. Craig M. Williams 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(28):8491-8491