全文获取类型
收费全文 | 13168篇 |
免费 | 1124篇 |
国内免费 | 700篇 |
专业分类
化学 | 8849篇 |
晶体学 | 116篇 |
力学 | 513篇 |
综合类 | 51篇 |
数学 | 1662篇 |
物理学 | 3801篇 |
出版年
2023年 | 152篇 |
2022年 | 163篇 |
2021年 | 247篇 |
2020年 | 330篇 |
2019年 | 354篇 |
2018年 | 261篇 |
2017年 | 275篇 |
2016年 | 421篇 |
2015年 | 435篇 |
2014年 | 517篇 |
2013年 | 756篇 |
2012年 | 960篇 |
2011年 | 1103篇 |
2010年 | 691篇 |
2009年 | 717篇 |
2008年 | 816篇 |
2007年 | 811篇 |
2006年 | 714篇 |
2005年 | 616篇 |
2004年 | 590篇 |
2003年 | 496篇 |
2002年 | 416篇 |
2001年 | 316篇 |
2000年 | 244篇 |
1999年 | 195篇 |
1998年 | 158篇 |
1997年 | 130篇 |
1996年 | 154篇 |
1995年 | 148篇 |
1994年 | 167篇 |
1993年 | 132篇 |
1992年 | 126篇 |
1991年 | 101篇 |
1990年 | 114篇 |
1989年 | 84篇 |
1988年 | 95篇 |
1987年 | 69篇 |
1986年 | 78篇 |
1985年 | 102篇 |
1984年 | 78篇 |
1983年 | 80篇 |
1982年 | 56篇 |
1981年 | 58篇 |
1980年 | 51篇 |
1979年 | 39篇 |
1977年 | 43篇 |
1976年 | 42篇 |
1975年 | 42篇 |
1974年 | 52篇 |
1973年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
101.
Metal organic frameworks (MOFs) derived carbonaceous materials have a wide range of applications in the fields of energy storage, catalysis, adsorption and separation, etc. Especially, zeolitic imidazolate framework-8 (ZIF-8) is an excellent candidate to synthesize porous carbon due to the large surface area and high nitrogen content. However, the dominated microporous structure of ZIF-8-derived carbon significantly hinders ionic mass transfer, limiting the improvement of performance. Herein, MOF-derived mesoporous carbon was prepared using ZIF-8 as carbon precursor and cheap sodium silicate (Na2SiO3) as activator. The introduction of Na2SiO3 created rich mesoporous structure and increased specific surface area, as well as the effects of pyrolysis temperature and Na2SiO3 dosage on performance was also investigated. The obtained ZIF-derived porous carbon exhibits good electrochemical performance with specific capacitance of 263 F/g at 1 A/g and excellent cycle life (96.07% after 10,000 GCD cycles) in supercapacitor. The use of cheap Na2SiO3 activator provides a new orientation for the preparation of MOF-derived carbons with rich pores, high surface area, and facilitates the large-scale application of MOF-derived carbons. 相似文献
102.
Ping Zhang Wenju Chang Hongyun Jiao Yanshang Kang Wenxuan Zhao Peipei Cui Yong Liang Wei-Yin Sun Yi Lu 《中国化学快报》2021,32(5):1717-1720
An electron-deficient [CpERhCl2]2 catalyzed annulation of N-pentafluorophenylbenzamides with internal alkynes was successfully established under mild reaction conditions, with the assistance of Lewis acid silver salt. Particularly, electron-deficient benzamide substrates were smoothly transformed into the desired products in this catalytic system. The catalytic system showed a broad tolerance for different substituents on the aromatic rings or aryl, alkyl-substituted alkynes. 相似文献
103.
104.
Chemistry of Natural Compounds - A new seco-abietanoid, 12-hydroxy-6,7-seco-abieta-8,11,13-triene-6,7-dioic acid (1), was isolated from the methanol extract of the bark of Cryptomeria japonica. The... 相似文献
105.
Steffen Cychy Sebastian Lechler Zijian Huang Michael Braun Ann Cathrin Brix Peter Blümler Corina Andronescu Friederike Schmid Wolfgang Schuhmann Martin Muhler 《催化学报》2021,42(12):2206-2215
在碱性甘油电氧化反应中,利用电化学傅里叶变换衰减全反射谱红外光谱法,研究了薄膜流动池中滴注硼酸镍催化剂负载量对玻碳电极性能的影响.连续操作的径向流动池包括一个位于内反射元件上方50μm的钻孔电极,可实现红外光谱分析.这是在确定条件下对电催化剂进行简便和可重复筛选的一个适合的方法,同时还提供了对复杂反应(如甘油氧化)产物选择性的检测.通过对泵送电解液进行更耗时的定量高效液相色谱分析,结果表明,衰减全反射红外光谱法可快速鉴定产物.在层流条件下,水中使用0.1 M甘油和1 M KOH,流速为5μL min-1时,甘油转化率较高.转化率和选择性取决于催化剂的负载量,负载量又决定了催化剂层的厚度和粗糙度.由于在更粗糙的膜中停留时间更长有利于再吸附和C-C键断裂,因此当负载量最高达210μg cm-2时,甘油转化率为73%且甲酸选择性接近80%.当最低负载量为13μg cm-2时,甘油转化率达到63%,甲酸选择性降至60%,相应地,C2物种(如乙醇酸盐)选择性较高,为8%.因此,只有催化剂负载量较低时才能形成几微米厚度范围内的薄膜,此时才适合进行优质催化剂的筛选. 相似文献
106.
Herein,we propose a novel photoelectrochemical(PEC) biosensor for dual microRNAs(miRNAs) highly sensitive and simultaneous biosensing based on strand displaced amplification(SDA) reaction.The recognition of H_(miR-21) and H_(let-7 a) by microRNA-21 and let-7 a leads to their change in hairpin structures,subsequently initiating the immobilization of abundant CdS quantum dots(CdS QD s) and methylene blue(MB) based on SDA reaction.The immobilized CdS QDs and MB produce both high PEC currents under430 nm light and 627 nm light illumination,respectively,and the generated PEC currents are closely relied on target miRNAs amounts.Thus,highly sensitive and simultaneous detection of microRNA-21 and let-7 a was readily achieved with detection limit at 6.6 fmol/L and 15.4 fmol/L based on 3σ,respectively.Further,this PEC biosensor was applied in simultaneous analysis of miRNA-21 and let-7 a in breast cancer patient's serum with acceptable results.We expect this biosensor will find more useful application in diagnosis of miRNA-related diseases. 相似文献
107.
Lingli Lei Yuanyuan Zhang Ying Jiang Lulu Xiong Yingshuai Liu Chang Ming Li 《Electroanalysis》2021,33(10):2180-2186
Biomimetic electrochemical sensors are very promising not only due to their lower expense and longer stability than conventional enzymatic ones, but they also often suffer from simultaneously achieving high sensitivity and good selectivity. Here we present a well-defined Au@Co3O4/CeO2 yolk-shell nanostructure (YSN) that is first synthesized and exploited as highly efficient electrocatalysts for hydrogen peroxide (H2O2) detection. The introduced CeO2 in Co3O4 matrix greatly facilitates the migration of lattice oxygen, which increases the concentration of surface oxygen vacancies (Oa), remarkably enhancing the adsorption ability of H2O2 and promoting the decomposition of H2O2 for faster electron transfer than pristine Au@Co3O4 core-shell nanostructure (CSN). The abundant Oa of Au@Co3O4/CeO2 YSN is confirmed by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). The as-prepared biomimetic sensor delivers a wide dynamic range (5.0 nM to 5.4 μM), a low limit of detection (LOD) (2.74 nM), and a high sensitivity (35.67 μA μM−1 cm−2), paving a new way to construct an ultrasensitive and selective enzyme-free biomimetic electrochemical sensor. Furthermore, the sensor is used to real-time monitor H2O2 released from human cervical cancer cells (HeLa) and human umbilical vein endothelial cells (HUVEC), demonstrating its great potential in practical applications. 相似文献
108.
Hun Ho Park Junseong Park Hye Joung Cho Jin-Kyoung Shim Ju Hyung Moon Eui Hyun Kim Jong Hee Chang Soo Youl Kim Seok-Gu Kang 《Molecules (Basel, Switzerland)》2021,26(2)
Resident cancer cells with stem cell-like features induce drug tolerance, facilitating survival of glioblastoma (GBM). We previously showed that strategies targeting tumor bioenergetics present a novel emerging avenue for treatment of GBM. The objective of this study was to enhance the therapeutic effects of dual inhibition of tumor bioenergetics by combination of gossypol, an aldehyde dehydrogenase inhibitor, and phenformin, a biguanide compound that depletes oxidative phosphorylation, with the chemotherapeutic drug, temozolomide (TMZ), to block proliferation, stemness, and invasiveness of GBM tumorspheres (TSs). Combination therapy with gossypol, phenformin, and TMZ induced a significant reduction in ATP levels, cell viability, stemness, and invasiveness compared to TMZ monotherapy and dual therapy with gossypol and phenformin. Analysis of differentially expressed genes revealed up-regulation of genes involved in programmed cell death, autophagy, and protein metabolism and down-regulation of those associated with cell metabolism, cycle, and adhesion. Combination of TMZ with dual inhibitors of tumor bioenergetics may, therefore, present an effective strategy against GBM by enhancing therapeutic effects through multiple mechanisms of action. 相似文献
109.
Nuri Choi Gabsik Yang Joo Hyeon Jang Han Chang Kang Yong-Yeon Cho Hye Suk Lee Joo Young Lee 《Molecules (Basel, Switzerland)》2021,26(4)
Gout is a type of inflammatory arthritis caused by the deposition of monosodium uric acid (MSU) crystals in tissues. The etiology of gout is directly linked to the NLRP3 inflammasome, since MSU crystals are NLRP3 inflammasome activators. Therefore, we decided to search for a small-molecule inhibitor of the NLRP3 inflammasome for the prevention of gout inflammation. We found that loganin suppressed MSU crystals-induced caspase-1 (p20) and interleukin (IL)-1β production and apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) specks formation in mouse primary macrophages, showing its ability to inhibit the NLRP3 inflammasome. In an air pouch inflammation model, oral administration of loganin to mice prevented MSU crystals-induced production of mature IL-1β and IL-18 in air pouch exudates, resulting in decreased neutrophil recruitment. Furthermore, oral administration of loganin suppressed MSU crystals-induced gout inflammation in a mouse foot gout model, which was accompanied by the inhibition of the NLRP3 inflammasome. Loganin blocked de novo synthesis of mitochondrial DNA in air pouches and foot tissues injected with MSU crystals. Consistently, loganin prevented MSU crystals-induced mitochondrial damage in macrophages, as it increased mitochondrial membrane potential and decreased the amount of mitochondrial reactive oxygen species. These data demonstrate that loganin suppresses NLRP3 inflammasome activation by inhibiting mitochondrial stress. These results suggest a novel pharmacological strategy to prevent gout inflammation by blocking NLRP3 inflammasome activation and mitochondrial dysfunction. 相似文献
110.
Yin Su Zuo‐Chang Chen Han‐Rui Tian Yun‐Yan Xu Qianyan Zhang Su‐Yuan Xie Lan‐Sun Zheng 《中国化学》2021,39(1):93-98
Because of its unsaturated bonds, C60 is susceptible to polymerize into dimers. The implications of nitrogen doping on the geometrical and electronic structure of C60 dimers have been ambiguous for years. A quarter‐century after the discovery of azafullerene dimer (C59N)2, we reported its single crystallographic structure in 2019. Herein, the unambiguous crystal structure information of (C59N)2 is elucidated specifically, revealing that the inter‐cage C—C single bond length of (C59N)2 is comparable with that of an ordinary C(sp3)‐C(sp3) single bond, and that the most stable conformer of (C59N)2 is gauche‐conformer with a dihedral angle of 66°. To amend the structural deviations, geometrical structure of (C59N)2 is optimized by a B3LYP‐D3BJ function, which is proved to be more consistent with its single crystal structure than those by the commonly used B3LYP function. Moreover, the calculation method is also suitable for other representative fullerene dimers, such as (C60)2 and its divalent anion. Additionally, the dissociation of (C59N)2 at 473 K under mass spectrometric conditions suggests the inter‐cage C—C bond is relatively weaker than an ordinary C—C single bond, which can be explained by the interaction energies of inter‐cages. 相似文献