全文获取类型
收费全文 | 12735篇 |
免费 | 2387篇 |
国内免费 | 2654篇 |
专业分类
化学 | 9381篇 |
晶体学 | 337篇 |
力学 | 647篇 |
综合类 | 337篇 |
数学 | 1668篇 |
物理学 | 5406篇 |
出版年
2024年 | 14篇 |
2023年 | 186篇 |
2022年 | 327篇 |
2021年 | 435篇 |
2020年 | 478篇 |
2019年 | 533篇 |
2018年 | 408篇 |
2017年 | 469篇 |
2016年 | 523篇 |
2015年 | 685篇 |
2014年 | 811篇 |
2013年 | 1010篇 |
2012年 | 1179篇 |
2011年 | 1191篇 |
2010年 | 1027篇 |
2009年 | 1043篇 |
2008年 | 1143篇 |
2007年 | 1007篇 |
2006年 | 913篇 |
2005年 | 769篇 |
2004年 | 588篇 |
2003年 | 452篇 |
2002年 | 393篇 |
2001年 | 380篇 |
2000年 | 298篇 |
1999年 | 242篇 |
1998年 | 151篇 |
1997年 | 140篇 |
1996年 | 138篇 |
1995年 | 139篇 |
1994年 | 120篇 |
1993年 | 103篇 |
1992年 | 89篇 |
1991年 | 83篇 |
1990年 | 58篇 |
1989年 | 50篇 |
1988年 | 43篇 |
1987年 | 29篇 |
1986年 | 34篇 |
1985年 | 28篇 |
1984年 | 15篇 |
1983年 | 12篇 |
1982年 | 5篇 |
1981年 | 16篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
71.
72.
In this report, CuO/MoS2 composites were successfully prepared by the hydrothermal method where nano‐sized CuO was uniformly distributed on the surface of hierarchical MoS2 substrates (CuO/MoS2 composites). Their physicochemical properties and catalytic performance in ammonium perchlorate (AP) decomposition were investigated and characterized by XRD, SEM, TEM, BET, XPS, TG/DSC and combustion measurement. The results showed that it could decrease AP decomposition temperature at high decomposition stage from 416.5 °C to 323.5 °C and increase the heat release from 378 J/g (pure AP) to 1340 J/g (AP with catalysts), which was better than pure CuO nanoparticles (345.5 °C and 1046 J/g). Meanwhile, it showed excellent performance in combustion reaction either in N2 or air atmosphere. The results obtained by photocurrent spectra, photoluminescence spectra and time‐resolved fluorescence emission spectra indicated that loading CuO mediated the generation rate and combination rate of electrons and holes, thus tuning the catalytic performance on AP decomposition. This study proved that employing the supports that can synergistically interact with CuO is an efficient strategy to enhance the catalytic performance of CuO. 相似文献
73.
Hairan Zhang Qiuyue Zhang Ling Zhang Tingting Pei Erni Li Huiting Wang Prof. Qian Zhang Prof. Lixin Xia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(6):1535-1542
Poly(N-isopropylacrylamide)-modified graphene oxide (PNIPAm-GO), which is a type of thermally responsive GO, was designed and synthesized through a covalent “grafting-from” strategy. The as-prepared modified nanosheets integrated the individual advantages of two components, such as the thermal sensitivity of the PNIPAm terminal as well as the conductivity and the open 2D structure of the GO substrate. PNIPAm-GO was able to perform the reversible regulation of hydrophilicity/hydrophobicity in aqueous solution upon variations in the temperature. Such a unique property might also lead to the utilization of PNIPAm-GO as an intelligent electrode material to achieve a switchable electrochemical response toward a [Fe(CN)6]3−/4− probe. The PNIPAm-GO modified glassy carbon electrode (PNIPAm-GO/GC electrode) was able to exhibit better electrochemical performance in an ON/OFF switching effect than the PNIPAm-modified glassy carbon electrode (PNIPAm/GC electrode) without GO owing to the intrinsic properties and large surface area of the introduced GO. Moreover, it was found that the PNIPAm-GO/GC electrode also displayed excellent thermally responsive electrocatalysis toward the detection of 1,4-dihydro-β-nicotinamide adenine dinucleotide (NADH) and dopamine (DA), which resulted in two different catalytic statuses on the same electrode. This kind of switchable catalytic performance of the PNIPAm-GO/GC electrode might greatly enhance the flexibility of its application, and thus it is expected to have wide potential for applications in the fields of biosensors and biocatalysis. 相似文献
74.
Yong Xia Armido Studer 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(29):9941-9945
The diversity‐oriented desulfonylative functionalization of alkyl allyl sulfones with various sulfone‐type reagents by radical chemistry has been developed. The readily installed allylsulfonyl moiety acts as a C‐radical precursor, which is substituted by various functionalities using sulfur‐based radical trapping reagents. The generality of this approach is documented by the successful desulfonylative alkynylation, azidation, trifluoromethylthiolation, sulfenylation, trifluoromethylselenylation, halogenation, and deuteration. The method is compatible with a wide range of functional groups. Considering the deuteration, products are obtained in good yields with a high level of deuterium incorporation. 相似文献
75.
出行者的选择行为分析是交通系统中的一项重要内容,随着城市的发展,交通出行方式大体分为三大类:公共交通出行、辅助公共交通出行和私人交通出行。本文在以往的研究基础上,采用演化博弈的方法研究公共交通、共享汽车以及私家车三者之间的博弈关系,模拟出行者的选择行为,分析博弈均衡点稳定性及参数条件。通过模型仿真实验,演化结果中各项比例大小取决于各项收益、补贴、损失以及额外收益,要增加公共交通的配套设施,增收拥堵费以及增加对共享汽车的补贴及配套服务。 相似文献
76.
Mingyi Liu Shibo Huang Jinhua Wen Chunhua Xia Hong Zhang Yuqing Xiong 《Biomedical chromatography : BMC》2019,33(11)
Bicyclol is a synthetic drug widely used to treat chronic hepatitis B. This study aimed to develop a selective, sensitive and high‐throughput liquid chromatography–tandem mass spectrometric method for the detection of bicyclol in human plasma. Bicyclol was detected using a multiple reaction monitoring mode, with ammonium adduct ions (m/z 408.2) as the precursor ion and the [M‐CH3]+ ion (m/z 373.1) subjected to demethylation as the product ion. Chromatographic separation was achieved using a Zobax Eclipse XDB‐C18 column with a gradient elution and a mobile phase of 2 mm ammonium formate and acetonitrile. Bicyclol was extracted from plasma matrix by precipitation. A linear detection response was obtained for bicyclol ranging from 0.500 to 240 ng/mL, and the lower limit of quantification was 0.500 ng/mL. The intra‐ and inter‐day precisions were all ≤7.4%, and the accuracies were within ±6.0%. The extraction recovery was >95.9%, and the matrix effects were between 96.0% and 108%. Bicyclol was found to be unstable in human plasma at room temperature, but the degradation was minimized by conducting sample collection and preparation in an ice bath. The validated method was successfully applied to investigate the pharmacokinetics of bicyclol tablets in six healthy Chinese volunteers. 相似文献
77.
This report details the preparation of anastrozole (ATZ) reservoir‐type intravaginal ring (IVR) and the detection of the concentration of ATZ in beagle dog plasma by liquid chromatography–tandem mass spectrometry (LC–MS/MS). An ATZ reservoir‐type IVR which included ATZ silicone elastomer core and a nonactive silicone layer was manufactured by reaction injection moulding at 80°C for 20 min. An in vitro release experiment was performed under sink conditions and the samples were determined by high‐performance liquid chromatography. A bioanalytical method was developed and validated for determination of ATZ in beagle dog plasma for IVR development. The analytical method consisted of the extraction of plasma samples and determination of ATZ by LC–MS/MS using buspirone as the internal standard. Separation was achieved on a Kinetex‐C18 110A column (3 × 30 mm, 2.6 μm, Phenomenex) using step‐gradient mobile phase and an isocratic flow rate consisting of formic acid. Protonated ions formed by a turboion spray in the positive mode was used to detect the analyte (ATZ) and internal standard. The MS–MS detection was performed on a triple quadrupole mass spectrometer equipped with electrospray ionization source. The mass spectrometer was operated in the multiple reaction monitoring mode. The mass transition ion‐pair was followed as m/z from 294.10 to 225.08 for anastrozole and m/z from 386.23 to 122.11 for buspirone. The results proved that the correlation between in vitro and in vivo analyses was relatively good. 相似文献
78.
A linear optical unambiguous discrimination of hyperentangled Bell states is proposed for two‐photon systems entangled in both the polarization and momentum degrees of freedom (DOFs) assisted by time bin. This unambiguous discrimination scheme can completely identify 16 orthogonal hyperentangled Bell states using only linear optical elements, where the function of the auxiliary entangled Bell state is replaced by time bin. Moreover, the possibility of extending this scheme for distinguishing hyperentangled Bell states in n DOFs is discussed, and it shows that hyperentangled Bell states in n ( ) DOFs can be distinguished with k ( ) auxiliary entangled states of additional DOFs by introducing a time delay, which decreases the auxiliary entanglement resource required for unambiguous discrimination of hyperentangled Bell state. Therefore, this scheme provides a new way for distinguishing hyperentangled states with current technology, which will extend the application of discrimination of hyperentangled states via linear optics to other quantum information protocols besides hyperdense coding schemes in the future. 相似文献
79.
石墨氮化碳(g-C3 N4)是一种可见光响应的非金属半导体材料.g-C3 N4具有廉价易得,物理化学性质稳定,无毒无污染等优点,在环境净化和能源催化领域具有良好的应用前景.然而,体相g-C3 N4存在比表面积小,可见光吸收能力差,光生电子和空穴复合效率高等缺点,从而严重限制了其在实际中的应用.本文在概述了g-C3 N4的结构、特性及制备方法的基础上,着重归纳了g-C3 N4的改性方法,其中包括元素掺杂、形貌调控、贵金属沉积等改性手段的研究进展.最后,本文探讨了g-C3 N4光催化反应机理,以及对g-C3 N4在水体环境净化领域的研究进行了展望. 相似文献
80.
Haobing Wang Xia Wu Yang Yang Masayoshi Nishiura Zhaomin Hou 《Angewandte Chemie (International ed. in English)》2020,59(18):7173-7177
The precise control of monomer sequence and stereochemistry in copolymerization is of much interest and importance for the synthesis of functional polymers, but studies toward this goal have met with only limited success to date. Now, the co‐syndiospecific alternating copolymerization of methoxyphenyl‐ and N,N‐dimethylaminophenyl‐functionalized propylenes with styrene by half‐sandwich rare‐earth catalysts is reported. This reaction efficiently afforded the corresponding functionalized propylene‐alt‐styrene copolymers with a perfect alternating sequence and excellent co‐syndiotacticity (rrrr >99 %), thus constituting the first example of co‐stereospecific alternating copolymerization of polar and non‐polar olefins. 相似文献