全文获取类型
收费全文 | 16653篇 |
免费 | 2923篇 |
国内免费 | 2416篇 |
专业分类
化学 | 12808篇 |
晶体学 | 182篇 |
力学 | 966篇 |
综合类 | 179篇 |
数学 | 1910篇 |
物理学 | 5947篇 |
出版年
2024年 | 43篇 |
2023年 | 325篇 |
2022年 | 460篇 |
2021年 | 558篇 |
2020年 | 687篇 |
2019年 | 635篇 |
2018年 | 626篇 |
2017年 | 510篇 |
2016年 | 852篇 |
2015年 | 787篇 |
2014年 | 1030篇 |
2013年 | 1275篇 |
2012年 | 1515篇 |
2011年 | 1530篇 |
2010年 | 1149篇 |
2009年 | 1112篇 |
2008年 | 1162篇 |
2007年 | 987篇 |
2006年 | 930篇 |
2005年 | 798篇 |
2004年 | 702篇 |
2003年 | 543篇 |
2002年 | 580篇 |
2001年 | 481篇 |
2000年 | 451篇 |
1999年 | 397篇 |
1998年 | 277篇 |
1997年 | 227篇 |
1996年 | 254篇 |
1995年 | 210篇 |
1994年 | 155篇 |
1993年 | 130篇 |
1992年 | 130篇 |
1991年 | 85篇 |
1990年 | 99篇 |
1989年 | 66篇 |
1988年 | 41篇 |
1987年 | 40篇 |
1986年 | 44篇 |
1985年 | 42篇 |
1984年 | 15篇 |
1983年 | 18篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1957年 | 2篇 |
1936年 | 1篇 |
1916年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 45 毫秒
981.
Yu-Cai He Lei Gong Feng Liu Ting Lu Qing Qing Li-Qun Wang Yue Zhang Feng-Ting Gao Xi Wang 《Applied biochemistry and biotechnology》2014,173(4):894-903
In the conversion of cassava starch dregs to biogas by anaerobic fermentation, the biogas residue (BR) containing lignocellulosic materials still remained in the environment. In order to effectively utilize BR, the complexed 1-methyl-3-methylimidazolium dimethyl phosphate ([Mmim]DMP) media were used for pretreating cellulosic materials. After the optimization of pretreatment, the IL [Mmim]DMP-HCl-water (78.5:1.5:20, w/w/w) pretreament media were used for pretreating BR at 130 °C for 30 min. Furthermore, BR pretreated could be effectively saccharified by cellulase of Galactomyces sp. CCZU11-1. Moreover, BR could be used as a cheap carbon source for the production of Galactomyces sp. CCZU11-1 cellulase. After the culture optimization, the optimal culture conditions were obtained as follows: BR 5 g/L, (NH4)2SO4 5 g/L, K2HPO4 2 g/L, MgSO4 0.2 g/L, NaCl 1 g/L, PEG6000 4 g/L, pH 5.5, and culture temperature 30 °C. After the fermentation for 6 days, the FPA and CMCase were 26.2 and 52.8 U/mL, respectively. In conclusion, waste BR could be chosen as a promising feedstock for biofuels. 相似文献
982.
983.
探讨酚酞啉对HRP(辣根过氧化酶)–Luminol–H2O2化学发光体系的增强作用。将酚酞啉加入辣根过氧化酶(HRP)–Luminol–H2O2化学发光体系,发光强度显著增强,发光持续时间达30 min以上。HRP–Luminol–H2O2化学发光体系的HRP质量浓度在5~800 pg/m L范围内与相对发光强度呈良好的线性关系,线性回归方程为lg I=1.07lgc+0.98,线性相关系数r=0.96,检出限为1.25 pg/m L。测定结果的相对标准偏差为2.8%~5.1%(n=10),加标回收率为93.5%~96.2%。酚酞啉可用于HRP及其相关标记物的定量分析。 相似文献
984.
Dr. Guangwu Li Prof. Taisuke Matsuno Yi Han Dr. Hoa Phan Shaofei Wu Dr. Qing Jiang Ya Zou Prof. Hiroyuki Isobe Prof. Jishan Wu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(24):9814-9822
Synthesis of fully conjugated cyclophanes containing large-size polycyclic aromatics is challenging. Now, three benzidine-linked, hexa-peri-hexabenzocoronene (superbenzene)-based ortho-, para-, and meta-cyclophanes are synthesized through intermolecular Yamamoto coupling reaction of structurally pre-organized precursors. Subsequent oxidative dehydrogenation gave the corresponding quinoidal benzidine-linked cyclophanes. Their geometries were confirmed by X-ray crystallographic analysis and their electronic properties were investigated by electronic absorption, cyclic voltammetry, and DFT calculations. The quinoidal benzidine-linked cyclophanes show thermally populated paramagnetic activity with a relatively large singlet-triplet energy gap. Two enantiomers for the ortho-cyclophanes ( 1-NH and 1-N ) were isolated and their chiral figure-of-eight macrocyclic structures were identified. The cage-like cyclophanes 2-NH and 3-NH with concave surface can selectively encapsulate fullerene C70. 相似文献
985.
Lisi Xie Dr. Jia Tian Yingjie Ouyang Xinai Guo Prof. Dr. Weian Zhang Prof. Dr. Ulf-Peter Apfel Prof. Dr. Wei Zhang Prof. Dr. Rui Cao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):15978-15982
Molecular design to improve catalyst performance is significant but challenging. In enzymes, residue groups that are close to reaction centers play critical roles in regulating activities. Using this bioinspired strategy, three water-soluble polymers were designed with appending Co porphyrins and different side-chain groups to mimic enzyme reaction centers and activity-controlling residue groups, respectively. With these polymers, high hydrogen evolution efficiency was achieved in neutral aqueous media for electro- (turnover frequency >2.3×104 s−1) and photocatalysis (turnover number >2.7×104). Porphyrin units are surrounded and protected by polymer chains, and more importantly, the activity can be tuned with different side-chain groups. Therefore, instead of revising molecular structures that is difficult from both design and synthesis points of view, polymers can be used to improve molecular solubility and stability and simultaneously regulate activity by using side-chain groups. 相似文献
986.
Light-Driven Crawling of Molecular Crystals by Phase-Dependent Transient Elastic Lattice Deformation
Yanjun Gong Yongxian Guo Fayuan Ge Wei Xiong Jie Su Yang Sun Chuang Zhang An-Min Cao Yifan Zhang Jincai Zhao Yanke Che 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(26):10423-10428
The light-driven crawling of a molecular crystal that can form three phases, (α, β, and γ) is presented. Laser irradiation of the molecular crystal can generate phase-dependent transient elastic lattice deformation. The resulting elastic lattice deformation that follows scanning irradiation of a laser can actuate the different phases of molecular crystal to move with different velocity and direction. Because the γ phase has a large Young's modulus (ca. 26 GPa), a force of 0.1 μN can be generated under one laser spot. The generated force is sufficient to actuate the γ-formed molecular crystals in a wide dimensional range to move longitudinally at a velocity of about 60 μm min−1, which is two orders of magnitude faster than the α and β phases. 相似文献
987.
Yuan Xu Jing Xue Qing Zhou Yongjun Zheng Xinghua Chen Prof. Songqin Liu Prof. Yanfei Shen Prof. Yuanjian Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(34):14606-14611
Emerging as a cost-effective and robust enzyme mimic, nanozymes have drawn increasing attention with broad applications ranging from cancer therapy to biosensing. Developing nanozymes with both accelerated and inhibited biocatalytic properties in a biological context is intriguing to peruse more advanced functions of natural enzymes, but remains challenging, because most nanozymes are lack of enzyme-like molecular structures. By re-visiting and engineering the well-known Fe-N-C electrocatalyst that has a heme-like Fe-Nx active sites, herein, it is reported that Fe-N-C could not only catalyze drug metabolization but also had inhibition behaviors similar to cytochrome P450 (CYP), endowing it a potential replacement of CYP for preliminary evaluation of massive potential chemicals, drug dosing guide, and outcome prediction. In addition, in contrast to electrocatalysts, the highly graphitic framework of Fe-N-C may not be obligatory for a competitive CYP-like activity. 相似文献
988.
Dr. Deng Pan Zhengzou Fang Erli Yang Zhenqiang Ning Qing Zhou Kaiyang Chen Yongjun Zheng Prof. Yuanjian Zhang Prof. Yanfei Shen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(38):16890-16897
The exceptional nature of WO3−x dots has inspired widespread interest, but it is still a significant challenge to synthesize high-quality WO3−x dots without using unstable reactants, expensive equipment, and complex synthetic processes. Herein, the synthesis of ligand-free WO3−x dots is reported that are highly dispersible and rich in oxygen vacancies by a simple but straightforward exfoliation of bulk WS2 and a mild follow-up chemical conversion. Surprisingly, the WO3−x dots emerged as co-reactants for the electrochemiluminescence (ECL) of Ru(bpy)32+ with a comparable ECL efficiency to the well-known Ru(bpy)32+/tripropylamine (TPrA) system. Moreover, compared to TPrA, whose toxicity remains a critical issue of concern, the WO3−x dots were ca. 300-fold less toxic. The potency of WO3−x dots was further explored in the detection of circulating tumor cells (CTCs) with the most competitive limit of detection so far. 相似文献
989.
Dr. Jun-Dong Yi Dr. Ruikuan Xie Prof. Zai-Lai Xie Prof. Guo-Liang Chai Prof. Tian-Fu Liu Prof. Rui-Ping Chen Prof. Yuan-Biao Huang Prof. Rong Cao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(52):23849-23856
It is still a great challenge to achieve high selectivity of CH4 in CO2 electroreduction reactions (CO2RR) because of the similar reduction potentials of possible products and the sluggish kinetics for CO2 activation. Stabilizing key reaction intermediates by single type of active sites supported on porous conductive material is crucial to achieve high selectivity for single product such as CH4. Here, Cu2O(111) quantum dots with an average size of 3.5 nm are in situ synthesized on a porous conductive copper-based metal–organic framework (CuHHTP), exhibiting high selectivity of 73 % towards CH4 with partial current density of 10.8 mA cm−2 at −1.4 V vs. RHE (reversible hydrogen electrode) in CO2RR. Operando infrared spectroscopy and DFT calculations reveal that the key intermediates (such as *CH2O and *OCH3) involved in the pathway of CH4 formation are stabilized by the single active Cu2O(111) and hydrogen bonding, thus generating CH4 instead of CO. 相似文献
990.
Wan-Feng Zhang Xiao-Ping Xia Takahashi Eiichi Li Li Qing Yang Yan-Qiang Zhang Ya-Nan Yang Ming-Liang Liu Chunkit Lai 《Surface and interface analysis : SIA》2020,52(5):224-233
Secondary ion mass spectrometry (SIMS) has a wide range of applications in Earth Science research, thanks to its high precision and sensitivity, and its capacity in direct insitu micromeasurement. The technique is operated in ultra-high vacuum (UHV) conditions, especially for the measurement of volatiles such as hydrogen, or the water content in nominally anhydrous minerals (NAMs). To minimize the water background and obtain accurate and precise water contents in NAMs (eg, olivine) critical parameters such as presputtering time, field aperture (FA), dynamic transfer on/off, and primary beam current intensity were investigated for a CAMECA IMS 1280-HR system. When the chamber vacuum reaches approximately 2 × 10−9 mbar, we set the DTOS OFF, raster size to 50 μm and primary beam current to 5 nA, and used 2000 μm FA and 170-second presputtering time. Consequently, an approximately 1.2 ppmw water background and 3.6 ppmw limit of detection (LOD) were yielded, from analyzing the San Carlos olivine. Meanwhile, the water content and homogeneity of a range of olivine minerals were characterized for potential use as reference materials for SIMS water content measurement. Olivine water content calibration curve was also established by comparing the Fourier transform infrared (FTIR) results with the SIMS-measured 16O1H−/16O− ratios. Accuracy and precision of water content measurement were estimated to be better than approximately 10% in this study. 相似文献