全文获取类型
收费全文 | 151171篇 |
免费 | 2326篇 |
国内免费 | 553篇 |
专业分类
化学 | 81018篇 |
晶体学 | 1550篇 |
力学 | 6298篇 |
综合类 | 5篇 |
数学 | 17495篇 |
物理学 | 47684篇 |
出版年
2020年 | 1008篇 |
2018年 | 1858篇 |
2017年 | 1920篇 |
2016年 | 2293篇 |
2015年 | 1785篇 |
2014年 | 2121篇 |
2013年 | 5974篇 |
2012年 | 5238篇 |
2011年 | 6026篇 |
2010年 | 3726篇 |
2009年 | 3500篇 |
2008年 | 4961篇 |
2007年 | 4970篇 |
2006年 | 4961篇 |
2005年 | 7665篇 |
2004年 | 6962篇 |
2003年 | 5157篇 |
2002年 | 3236篇 |
2001年 | 3578篇 |
2000年 | 2615篇 |
1999年 | 2064篇 |
1998年 | 1722篇 |
1997年 | 1881篇 |
1996年 | 1838篇 |
1995年 | 1919篇 |
1994年 | 1693篇 |
1993年 | 1660篇 |
1992年 | 1871篇 |
1991年 | 1812篇 |
1990年 | 1762篇 |
1989年 | 1775篇 |
1988年 | 1747篇 |
1987年 | 1722篇 |
1986年 | 1630篇 |
1985年 | 2239篇 |
1984年 | 2364篇 |
1983年 | 1955篇 |
1982年 | 2295篇 |
1981年 | 2125篇 |
1980年 | 2138篇 |
1979年 | 2152篇 |
1978年 | 2287篇 |
1977年 | 2147篇 |
1976年 | 2165篇 |
1975年 | 2133篇 |
1974年 | 1942篇 |
1973年 | 2147篇 |
1972年 | 1321篇 |
1968年 | 1069篇 |
1967年 | 1125篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
1.
Journal of Applied Spectroscopy - With the COVID-19 outbreak, many challenges are posed before the scientific world to curb this pandemic. The diagnostic testing, treatment, and vaccine development... 相似文献
2.
Experimental Mechanics - Ratcheting is an important mechanical behavior of metals and alloys, which is caused by the repeated accumulations of tensile and compressive strain in circle load.... 相似文献
3.
4.
Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.
相似文献5.
Maschler Tobias Strmer-Stephan Bastian Morhard Jrg Stegmaier Thomas Tilebein Meike Griepentrog Hans W. 《Annals of Operations Research》2022,314(2):577-600
Annals of Operations Research - Selecting a vegetation layer design goes along with determining its future irrigation need. Therefore, it is essential to take a design decision that is minimising... 相似文献
6.
This review summarizes recent progress in understanding the oxygen reduction and evolution reactions at the lanthanum strontium manganite electrode of a high-temperature solid oxide cell. Information provided here is put into the perspective of the defect chemistry of lanthanum strontium manganite and its impact on the electrode reaction mechanisms itself. After summarizing recent views on the oxygen reduction reaction mechanism, the focus turns to the oxygen evolution reaction, which is significantly less treated in the literature. A combination of the information in the literature on both reactions was the basis for modified reaction mechanism of the oxygen evolution reaction to be proposed under consideration of recent experimental observations and theoretical findings. 相似文献
7.
Atopic dermatitis is characterized by leukocyte migration into the skin dermis and typically driven by excessive chemokine production at the site of inflammation. Conventional topical formulations such as gels, creams, and ointments are insufficient for this treatment because of low penetration of drug molecules into the targeted skin tissues. Herein, using a simple, green, sustainable strategy, we have developed novel primary zein nanoparticles embedded in curcumin (Cur) and coated with silk sericin (ZHSCs) for the topical delivery of Cur to penetrate into the dermis and exercise anti-dermatitis effects on the lesion with minimal side-effects. Transdermal delivery experiments and porcine skin fluorescence imaging indicated that ZHSCs facilitate the penetration of Cur across the epidermis layer of skin to reach deep-seated sites. Notably, ZHSCs = 1:0.25 (zein-to-silk sericin mass ratios of 1:0.25) markedly elevated the skin permeability and cumulative turnover of Cur transferred, which were provided a greater than a 3.8-fold increase relative to free Cur. The special nanoparticles of ZHS = 1:0.25 possessed the deepest localization depth and experience a transition of the particle structure and core-shell separation after penetrating into the dermis of skin. In a cell model of dermatitis induced by tumor necrosis factor α/interferon γ co-stimulation, compared with free Cur, Cur-loaded ZHS nanoparticles down-regulated the generation of inflammatory cytokines and chemokines in keratinocytes through suppression of the nuclear translocation of NF-κBp65 and hence exerted an anti-dermatitis effect. This strategy may provide new avenues and direction for the demanding issues of valid topical delivery systems. 相似文献
8.
Dr. Waleed Alsalahi Dr. Adam W. Augustyniak Dr. Włodzimierz Tylus Prof. Dr. Anna M. Trzeciak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(6):e202103538
The new nanocomposites, Pd/C/ZrO2, PdO/ZrO2, and Pd/PdO/ZrO2, were prepared by thermal conversion of Pd@UiO-66-Zr−NH2 (MOF) in nitrogen or air atmosphere. The presence of Pd nanoparticles, uniformly distributed on the ZrO2 or C/ZrO2 matrix, was evidenced by transmission electron microscopy, scanning electron microscopy (SEM), Raman and X-ray Photoelectron Spectroscopy (XPS) methods. All pyrolysed composites retained the shape of the MOF template. They catalyze carbonylative Suzuki coupling under 1 atm CO with an efficiency significantly higher than the original Pd@UiO-66-Zr−NH2. The most active PdO/ZrO2 composite, formed benzophenone with TOF up to 1600 h−1, while by using Pd@UiO-66-Zr−NH2, much lower TOF values, 51–95 h−1, were achieved. After the reaction, PdO/ZrO2 was recovered with the same composition and catalytic activity. Very good results were also obtained in the transfer hydrogenation of benzophenones to alcohols with Pd/C/ZrO2 and PdO/ZrO2 catalysts under microwave irradiation. 相似文献
9.
Georgia Ivanova Nadezhda Bozova Nikolay Petkov Dr. Cunbin An Dr. Benlin Hu Monika Mutovska Konstantin Konstantinov Dr. Yulian Zagranyarski Dr. Vladimira Videva Adelina Yordanova Prof. Martin Baumgarten Prof. Anela Ivanova 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(16):e202104411
Computational modeling of the optical characteristics of organic molecules with potential for thermally activated delayed fluorescence (TADF) may assist markedly the development of more efficient emitting materials for organic light-emitting diodes. Recent theoretical studies in this area employ mostly methods from density functional theory (DFT). In order to obtain accurate predictions within this approach, the choice of a proper functional is crucial. In the current study, we focus on testing the performance of a set of DFT functionals for estimation of the excitation and emission energy and the excited singlet-triplet energy gap of three newly synthesized compounds with capacity for TADF. The emitters are designed specifically to enable charge transfer by π-electron conjugation, at the same time possessing high-energy excited triplet states. The functionals chosen for testing are from various groups ranging from gradient-corrected through global hybrids to range-separated ones. The results show that the monitored optical properties are especially sensitive to how the long-range part of the exchange energy is treated within the functional. The accurate functional should also be able to provide well balanced distribution of the π-electrons among the molecular fragments. Global hybrids with moderate (less than 0.4) share of exact exchange (B3LYP, PBE0) and the meta-GGA HSE06 are outlined as the best performing methods for the systems under study. They can predict all important optical parameters correctly, both qualitatively and quantitatively. 相似文献
10.
Yang T. L. Kao C. L. Kuo C. E. Yeh H. C. Li W. J. Li H. T. Chen C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the... 相似文献