全文获取类型
收费全文 | 1555篇 |
免费 | 200篇 |
国内免费 | 303篇 |
专业分类
化学 | 1252篇 |
晶体学 | 9篇 |
力学 | 97篇 |
综合类 | 20篇 |
数学 | 287篇 |
物理学 | 393篇 |
出版年
2024年 | 3篇 |
2023年 | 12篇 |
2022年 | 27篇 |
2021年 | 44篇 |
2020年 | 39篇 |
2019年 | 40篇 |
2018年 | 48篇 |
2017年 | 28篇 |
2016年 | 66篇 |
2015年 | 53篇 |
2014年 | 90篇 |
2013年 | 116篇 |
2012年 | 116篇 |
2011年 | 112篇 |
2010年 | 102篇 |
2009年 | 91篇 |
2008年 | 103篇 |
2007年 | 82篇 |
2006年 | 84篇 |
2005年 | 101篇 |
2004年 | 96篇 |
2003年 | 86篇 |
2002年 | 114篇 |
2001年 | 117篇 |
2000年 | 50篇 |
1999年 | 37篇 |
1998年 | 38篇 |
1997年 | 17篇 |
1996年 | 26篇 |
1995年 | 12篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1992年 | 16篇 |
1991年 | 10篇 |
1990年 | 16篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有2058条查询结果,搜索用时 15 毫秒
51.
A new tetranuclear cluster [Co4(bm)6Cl2]·(H2O)2·(CH3OH)(1, Hbm is(1H-benzimidazol-2-yl)-methanol) has been synthesized by solvothermal method and structurally determined by IR, elemental analysis, and single-crystal X-ray diffraction. Complex 1 belongs to monoclinic space group P21/n with a = 21.1713(5), b = 12.7948(3), c = 24.0195(9) , β = 95.309(3)°, V = 6478.6(3) 3, Z = 4, F(000) = 2568, Dc = 1.289 g·cm–3, Mr = 1257.63, μ = 9.096 mm–1, S = 1.000, the final R = 0.0861 and wR = 0.2552 for 4956 observed reflections with I 2σ(I). Two connected face-sharing cubes are observed in the framework of 1, each with one vertex missing. Complex 1 forms a 2-D network through N–H···O hydrogen bonds. The apparent holes can be observed. 相似文献
52.
Transition metal phosphides (TMPs) are prospective anode materials for lithium-ion batteries (LIBs) due to their high theoretical capacities and low redox voltages. Herein, we report a template directing method to develop a tube-sheath hybrid composing of cobalt phosphide particles encapsulated in metal organic frameworks (MOFs) derived N-doped carbon sheaths (CoxP@NC). The utilization of directing template leads to a homogenous distribution of the subsequently formed cobalt phosphide particles, restrains the aggregation of cobalt phosphides, and thus results in the superb rate capability and cyclability. Contributable to the integrated merits of the interior downsized cobalt phosphide particles and the outer ZIF-67 derived porous carbon sheath, the volume expansion during cycling is effectively suppressed. The CoxP@NC hybrid shows superb electrochemical performance as anode material for LIB, with good reversible capacity of 928 mAh·g?1 after 100 cycles at 0.1 A g?1, and high stability of 526 mAh·g?1 after 600 cycles at 1.0 A g?1. This work provides a route for rational design of MOF derived carbon-based anode material for LIB, which could also be applied as a promising platform in diverse field. 相似文献
53.
Shanwen Zhang Chun Gui Mingwei Shao Pachaiyappan Saravana Kumar 《Natural product research》2020,34(11):1499-1504
AbstractTunicamycin E (1), featuring a methyl substitution at C-10′, was isolated from marine-derived Streptomyces xinghaiensis SCSIO S15077 originated from the South China Sea sediment together with six known compounds, tunicamycin B (2), tunicamycin X (3), tunicamycin A (4), streptovirudin D2 (5), tunicamycin C (6), and tunicamycin C3 (7). The structure of compound 1 was elucidated by detailed spectroscopic data analyses. All the compounds exhibited strong to moderate antibacterial activity against Gram-positive bacteria Bacillus thuringiensis BT01 and B. thuringiensis W102 with MIC values ranging from 0.008 to 2 μg/mL. Moreover, compounds 1–7 exhibited moderate antifungal activity against Candida albicans ATCC 96901 and C. albicans CMCC (F) 98001 with MIC values ranging from 2 to 32 μg/mL. This is the first report that tunicamycins exhibit antimicrobial activities against B. thuringiensis, C. albicans CMCC (F) 98001 and a fluconazole resistant strain C. albicans ATCC 96901. 相似文献
54.
Let W be a potential on R 2 which is equivariant by the symmetry group of the equilateral triangle and has three minima. We show that the elliptic system possesses a nontrivial smooth solution U : R 2 → R 2. Here DW(U)T is the transpose of the derivative DW( U ). The natural energy of the problem is unbounded and compactness techniques cannot be applied. The proof depends on careful energy estimates and asymptotics for several one-dimensional problems and for two-dimensional problems on bounded domains. © 1996 John Wiley & Sons, Inc. 相似文献
55.
Can Liao Wei Wang Junling Wang Longfei Han Shuilai Qiu Lei Song Zhou Gui Yongchun Kan Yuan Hu 《Journal of Energy Chemistry》2021,(5):1-10
To date,lithium-ion batteries are becoming increasingly significant in the application of portable devices and electrical vehicles,and revolutionary progress in theoretical research and industrial application has been achieved.However,the commercial polyolefin separators with unsatisfying electrolytes affinity and poor thermal stability have extremely restricted the further application of lithium-ion batteries,especially in the high-temperature fields.In this work,magnetron sputtering deposition technique is employed to modify the commercial polyimide separator by coating silicon nitride on both sides.Magnetron sputtering deposition modified polyimide(MSD-PI)composite separator shows high thermal stability and ionic conductivity.More importantly,compared with the cells using Celgard separator,the cells with MSD-PI separator exhibit superior electrochemical performance,especially long-term cycle performance under high temperature environment,owing to the high thermal conductivity of surface Si3 N4 particles.Hence,lithium-ion batteries with MSD-PI separator are capable of improving thermal safety and capacity retention,which demonstrates that magnetron sputtering deposition technique could be regarded as a promising strategy to develop advanced organic/inorganic composite separators for high-temperature lithium-ion batteries. 相似文献
56.
57.
58.
Two new eudesmane sesquiterpene lactones were isolated from the stalk of Lactuca sativa var.anagustata L and their structureswere elucidated by means of spectroscopic methods,including 2D NMR(~1H-~1H COSY,HMBC and NOESY) as 1β-O-β-D-glucopyranosyl-4α-hydroxyl-5α,6β,11βH-eudesma-12,6α-olide(1) and 1β-hydroxyl-15-O-(p-methoxyphenylacetyl)-5α,6β,11βH-eudesma-3-en-12,6α-olide(2). 相似文献
59.
在模拟人体生理条件下,结合紫外光谱和分子对接模型运用荧光光谱研究了腺苷与人血清白蛋白(HSA)间的键合作用。腺苷有较强的能力猝灭人血清白蛋白的内源荧光,且根据Stern-Volmer方程判断出猝灭机制为静态猝灭。本文运用相应的荧光值和Vant’Hoff热力学方程求得了不同温度下的结合常数(K)以及一些热力学参数,如焓变(ΔH)和熵变(ΔS)。结果表明:键合过程中疏水作用力对新化合物的稳定性起主要作用,这与分子对接模型方法研究的结果基本一致。另外还研究了常见离子对结合常数的影响。 相似文献
60.
The entire gene of carboxyltransferase(CT) domain of acetyl-CoA carboxylase(ACCase) from Chinese Spring wheat(CSW) plastid was cloned firstly, and the 2.3 kb gene was inserted into PET28a^+ vector and expressed in E. coil in a soluble state. The (His)6 fusion protein was identified by SDS-PAGE and Western blot. The recombinant protein was purified by affinity chromatography, and the calculated molecular mass(Mr) was 88000. The results of the sequence analysis indicate that the cloned gene(GeneBank accession No. EU124675) was a supplement and revision of the reported ACCase CT partial cDNA from Chinese Spring wheat plastid. The recombinant protein will be significant for us to investigate the recognizing mechanism between ACCase and herbicides, and further to screen new herbicides. 相似文献