全文获取类型
收费全文 | 6077篇 |
免费 | 1054篇 |
国内免费 | 602篇 |
专业分类
化学 | 3975篇 |
晶体学 | 55篇 |
力学 | 276篇 |
综合类 | 33篇 |
数学 | 767篇 |
物理学 | 2627篇 |
出版年
2024年 | 25篇 |
2023年 | 154篇 |
2022年 | 226篇 |
2021年 | 250篇 |
2020年 | 255篇 |
2019年 | 233篇 |
2018年 | 199篇 |
2017年 | 197篇 |
2016年 | 316篇 |
2015年 | 275篇 |
2014年 | 339篇 |
2013年 | 409篇 |
2012年 | 519篇 |
2011年 | 577篇 |
2010年 | 352篇 |
2009年 | 345篇 |
2008年 | 372篇 |
2007年 | 329篇 |
2006年 | 316篇 |
2005年 | 263篇 |
2004年 | 195篇 |
2003年 | 169篇 |
2002年 | 193篇 |
2001年 | 153篇 |
2000年 | 124篇 |
1999年 | 155篇 |
1998年 | 128篇 |
1997年 | 108篇 |
1996年 | 105篇 |
1995年 | 71篇 |
1994年 | 55篇 |
1993年 | 52篇 |
1992年 | 47篇 |
1991年 | 59篇 |
1990年 | 32篇 |
1989年 | 27篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1986年 | 22篇 |
1985年 | 17篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有7733条查询结果,搜索用时 0 毫秒
161.
Promoting electron mobility is the key to designing high performance electron transport materials(ETMs). Formation of intermolecular interaction can be helpful to enhance their electron mobilities as a result of more ordered molecular stacking.Here, to reveal the inherent influence of intermolecular π-π stacking on the electron mobilities, we designed two ETMs, namely,2,4-diphenyl-6-[3-(2-triphenylenyl)phenyl]-1,3,5-triazine(TPTRZ) and 2,4-diphenyl-6-[4′-(2-triphenylenyl)[1,1′-biphenyl]-3-yl]-1,3,5-triazine(TPPTRZ). Thermal, photophysical and electrochemical measurement results indicate they are good ETM candidates. Additionally, TPTRZ and TPPTRZ exhibit high electron mobilities of 3.60×10~(-5) and 3.58×10~(-5) cm~2V-1 s~(-1), respectively, at an electric field of 7×10~5 V cm~(-1). By taking X-ray single crystal structure, theoretical calculation and time of flight(TOF) results into consideration, it is revealed that strong intermolecular π-π stacking induced by planar triphenylene and triphenyltriazine units renders TPTRZ and TPPTRZ small energetic and positional disorder parameters, and results in their high electron mobilities thereby. By further enhancing intermolecular π-π stacking, ETMs with even higher electron mobilities can thus be anticipated. 相似文献
162.
以水-乙二醇为溶剂,以聚乙烯吡咯烷酮(PVP)为表面活性剂,采用溶剂热法合成了NiO纳米片,NiO纳米薄片通过自组装形成花状结构。 改变反应温度和溶剂,制备了NiO纳米立方体颗粒和NiO纳米球形颗粒。 用合成的NiO纳米材料制备工作电极,在6 mol/L的KOH溶液中利用三电极体系进行了电化学性能测试。 在电化学性能测试中进行了循环伏安测试、恒电流充放电测试和电化学阻抗谱(EIS)测试。 结果表明,NiO纳米片的比电容最高(在电流密度为0.5 A/g时比电容值为402 F/g),倍率性能最佳(0.5 A/g增加至4 A/g时有80.1%的电容保持率)。 在电流密度为4 A/g时对NiO纳米片进行1000次恒流充放电循环测试,比电容损失了9.7%。 相似文献
163.
Sheng‐Li Hou Jie Dong Xiao‐Lei Jiang Zhuo‐Hao Jiao Bin Zhao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(2):587-591
Cyclization of propargylic alcohols with CO2 is an important reaction in industry, and noble‐metal catalysts are often employed to ensure the high product yields under environmentally friendly conditions. Herein a porous noble‐metal‐free framework 1 with large 1D channels of 1.66 nm diameter was synthesized for this reaction. Compound 1 exhibits excellent acid/base stability, and is even stable in corrosive triethylamine for one month. Catalytic studies indicate that 1 is an effective catalyst for the cyclization of propargylic alcohols and CO2 without any solvents under mild conditions, and the turnover number (TON) can reach to a record value of 14 400. Furthermore, this MOF catalyst also has rarely seen catalytic activity when the biological macromolecule ethisterone was used as a substrate. Mechanistic studies reveal that the synergistic catalytic effect between CuI and InIII plays a key role in the conversion of CO2. 相似文献
164.
Dongdong Zhu Qiancheng Zhao Guilan Fan Shuo Zhao Liubin Wang Fujun Li Jun Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(36):12590-12594
Utilization of solar energy is of great interest for a sustainable society, and its conversion into electricity in a compact battery is challenging. Herein, a zinc–air battery with the polymer semiconductor polytrithiophene (pTTh) as the cathode is reported for direct conversion of photoenergy into electric energy. Upon irradiation, photoelectrons are generated in the conduction band (CB) of pTTh and then injected into the π2p* orbitals of O2 for its reduction to HO2?, which is disproportionated to OH? and drives the oxidation of Zn to ZnO at the anode. The discharge voltage was significantly increased to 1.78 V without decay during discharge–charge cycles over 64 h, which corresponds to an energy density increase of 29.0 % as compared to 1.38 V for a zinc–air battery with state‐of‐the‐art Pt/C. The zinc–air battery with an intrinsically different reaction scheme for simultaneous conversion of chemical and photoenergy into electric energy opens a new pathway for utilization of solar energy. 相似文献
165.
Carr G Poulsen M Klassen JL Hou Y Wyche TP Bugni TS Currie CR Clardy J 《Organic letters》2012,14(11):2822-2825
Microtermolides A (1) and B (2) were isolated from a Streptomyces sp. strain associated with fungus-growing termites. The structures of 1 and 2 were determined by 1D- and 2D-NMR spectroscopy and high-resolution mass spectrometry. Structural elucidation of 1 led to the re-examination of the structure originally proposed for vinylamycin (3). Based on a comparison of predicted and experimental (1)H and (13)C NMR chemical shifts, we propose that vinylamycin's structure be revised from 3 to 4. 相似文献
166.
M Collot C Loukou AV Yakovlev CD Wilms D Li A Evrard A Zamaleeva L Bourdieu JF Léger N Ropert J Eilers M Oheim A Feltz JM Mallet 《Journal of the American Chemical Society》2012,134(36):14923-14931
We designed Calcium Rubies, a family of functionalizable BAPTA-based red-fluorescent calcium (Ca(2+)) indicators as new tools for biological Ca(2+) imaging. The specificity of this Ca(2+)-indicator family is its side arm, attached on the ethylene glycol bridge that allows coupling the indicator to various groups while leaving open the possibility of aromatic substitutions on the BAPTA core for tuning the Ca(2+)-binding affinity. Using this possibility we now synthesize and characterize three different CaRubies with affinities between 3 and 22 μM. Their long excitation and emission wavelengths (peaks at 586/604 nm) allow their use in otherwise challenging multicolor experiments, e.g., when combining Ca(2+) uncaging or optogenetic stimulation with Ca(2+) imaging in cells expressing fluorescent proteins. We illustrate this capacity by the detection of Ca(2+) transients evoked by blue light in cultured astrocytes expressing CatCh, a light-sensitive Ca(2+)-translocating channelrhodopsin linked to yellow fluorescent protein. Using time-correlated single-photon counting, we measured fluorescence lifetimes for all CaRubies and demonstrate a 10-fold increase in the average lifetime upon Ca(2+) chelation. Since only the fluorescence quantum yield but not the absorbance of the CaRubies is Ca(2+)-dependent, calibrated two-photon fluorescence excitation measurements of absolute Ca(2+) concentrations are feasible. 相似文献
167.
A novel up-converting phosphor,NaxAlyFx+3y/CaF2(0.3 < x < 0.5,0 < y < 0.1) composite,is prepared by a hydrothermal process at 180°C and an annealing treatment at 500℃.X-ray diffraction(XRD) pattern indicates that NaxAlyFx+3y/CaF2 is a composite consisting of NaF,Na3 AlF6,and CaF2.The up-conversion luminescence properties of this phosphor are investigated by fluorescence spectrometer.Results show that NaxAlyFx+3y/CaF2 exhibits visible-to-ultraviolet up-conversion luminescence properties.The emission peaks at 316 and 336 nm are observed when excited by 610 nm,the luminescence lifetime of the emissions is great than 18 ms,and the internal fluorescence quantum yield is 4.2%.Additionally,the luminescent mechanism of this phosphor is also mentioned. 相似文献
168.
Pan PW Zhang Q Hou J Liu Z Bai F Cao MR Sun T Bai G 《Analytical and bioanalytical chemistry》2012,403(6):1661-1670
Bioorthogonal chemistry refers to chemical reactions that can occur within a living system without altering native biochemical processes. Applications of this concept extend to studies on a group of biomolecules that includes glycans, proteins, and lipids. In this study, a strategy for isolating cell surface glycoproteins and based on bioorthogonal chemistry was employed to identify new cancer-related glycoproteins. A novel alkyne reagent containing one disulfide bond was synthesized for the enrichment of glycoproteins metabolized with peracetylated N-azidoacetylmannosamine, which was applied on three different cancer cell lines, and all isolated proteins were analyzed by high-performance liquid chromatography-tandem mass spectrometry. The strategy of purifying cell surface glycoproteins introduced in this article was shown to be reliable, and a total of 56 cell surface glycoproteins were identified. Neuronal cell adhesion molecule was found uniquely expressed in A549 lung adenocarcinoma, and its expression in non-small-cell lung carcinomas was detected by immunohistochemistry. Furthermore, a significant increase of neuronal cell adhesion molecule expression was identified in non-small-cell lung adenocarcinoma compared with adjacent noncancerous tissues, and could be a novel potential target and marker in cancer treatment and detection. 相似文献
169.
Wang D Yang P Cheng Z Wang W Hou Z Dai Y Li C Lin J 《Journal of colloid and interface science》2012,365(1):320-325
Gd(2)(WO(4))(3) doped with Eu(3+) or Tb(3+) thin phosphor films with dot patterns have been prepared by a combinational method of sol-gel process and microcontact printing. This process utilizes a PDMS elastomeric mold as the stamp to create heterogeneous pattern on quartz substrates firstly and then combined with a Pechini-type sol-gel process to selectively deposit the luminescent phosphors on hydrophilic regions, in which a Gd(2)(WO(4))(3):Ln(3+) (Ln=Eu, Tb) precursor solutions were employed as ink. X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectra, as well as low voltage cathodoluminescence (CL) spectra were carried out to characterize the obtained samples. Under ultraviolet excitation and low-voltage electron beams excitation, the Gd(2)(WO(4))(3):Eu(3+) samples exhibit a strong red emission arising from Eu(3+)(5)D(0,1,2)-(7)F(1,2) transitions, while the Gd(2)(WO(4))(3):Tb(3+) samples show the green emission coming from the characteristic emission of Tb(3+) corresponding to (5)D(4)-(7)F(6,5,4,3) transitions. The results show that the patterning of rare earth-doped phosphors through combining microcontact printing with a Pechini-type sol-gel route has potential for field emission displays (FEDs) applications. 相似文献
170.
A per-hydroxylated pillar[6]arene was prepared. Single-crystal X-ray analysis demonstrated that its molecules are arranged in an up-to-down manner to form infinite channels in the solid state. Its host-guest complexation with a series of bispyridinium salts in solution was further investigated. It was found that the per-hydroxylated pillar[6]arene could form a 1:1 complex with paraquat in acetone with an association constant of 2.2 × 10(2) M(-1). This complex is a [2]pseudorotaxane as shown by its crystal structure, which is the first pillar[6]arene-based host-guest complex crystal structure. 相似文献