全文获取类型
收费全文 | 3810篇 |
免费 | 532篇 |
国内免费 | 468篇 |
专业分类
化学 | 2864篇 |
晶体学 | 36篇 |
力学 | 227篇 |
综合类 | 76篇 |
数学 | 449篇 |
物理学 | 1158篇 |
出版年
2024年 | 19篇 |
2023年 | 67篇 |
2022年 | 140篇 |
2021年 | 144篇 |
2020年 | 167篇 |
2019年 | 155篇 |
2018年 | 126篇 |
2017年 | 130篇 |
2016年 | 180篇 |
2015年 | 160篇 |
2014年 | 230篇 |
2013年 | 283篇 |
2012年 | 302篇 |
2011年 | 343篇 |
2010年 | 244篇 |
2009年 | 206篇 |
2008年 | 214篇 |
2007年 | 205篇 |
2006年 | 174篇 |
2005年 | 154篇 |
2004年 | 134篇 |
2003年 | 104篇 |
2002年 | 114篇 |
2001年 | 90篇 |
2000年 | 93篇 |
1999年 | 95篇 |
1998年 | 84篇 |
1997年 | 65篇 |
1996年 | 61篇 |
1995年 | 54篇 |
1994年 | 52篇 |
1993年 | 35篇 |
1992年 | 46篇 |
1991年 | 17篇 |
1990年 | 34篇 |
1989年 | 17篇 |
1988年 | 12篇 |
1987年 | 5篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有4810条查询结果,搜索用时 15 毫秒
161.
Nonlinear Dynamics - In this paper, a novel robust fractional-order sliding mode (FOSM)-based state constrained control scheme is designed for uncertain quadrotor UAVs (QUAVs). Model uncertainties... 相似文献
162.
163.
Meiru Lu Dr. Xiaoling Wu Dr. Changlong Hao Prof. Chuanlai Xu Prof. Hua Kuang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(28):7023-7030
Nonylphenols (NPNs) are persistent endocrine disruptors and their release into the environment is causing increasing concern about their impact on human health. Herein, an ultrasensitive electrochemical immunosensor was developed for the detection of NPNs in the leachates from 61 instant noodle containers (INCs) from 8 countries across Southeast Asia. Gold nanoclusters (AuNCs) were self-assembled with reduced graphene oxide (rGO; polyethylenimine–rGO) and used to modify a glassy carbon electrode (GCE), which showed excellent electrical conductivity. An anti-NPN antibody was then immobilized on the AuNCs and, if it specifically bound NPN, the reduction in conductivity of the GCE was remarkable. The designed immunosensor has a low detection limit (5.25 ng L−1) and high sensitivity for NPNs in the leachates of INCs. Remarkably, the leaching of estrogen-like compounds from different plastics of INCs and the correlation between NPN content and total estrogenic activity were thoroughly investigated. High temperatures caused polyethylene and polystyrene INCs to release more estrogen-like compounds than that of polypropylene INCs; this increased release of NPNs was associated with higher estrogen activity in living cells. These data fill the gap in human and environmental exposure to estrogen-like compounds through INCs. 相似文献
164.
165.
166.
Small molecule‐mediated glass transition of acrylic copolymers: Effect of hydrogen bonding strength on glass transition temperature
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Chongyang Liu Xiaotong Yin Yu Lin Aiguo Guan Guozhang Wu 《Journal of Polymer Science.Polymer Physics》2015,53(6):400-408
Poly(styrene‐co‐ethyl acrylate) [P(St‐co‐EA)] with different ratios of St/EA was mixed with the small molecule 4,4′‐thio‐bis(6‐tert‐butyl‐m‐methyl phenol) (AO300) to investigate the influence of hydrogen bonding strength on the glass transition behavior. The glass transition temperature (Tg) linearly increased after adding AO300, and the slope value decreased with increased St/EA ratio. All lines could be extended to 62 °C, demonstrating that Tg of the small molecule in situ detected by the polymer chain was much higher than that by small molecule itself (29 °C). Fourier transform infrared spectroscopy analysis showed that the small molecules began to be self‐associated at a concentration where the hydrogen bonded carbonyl ratio of the bulk polymer was approximately 0.5 and irrespective of the St/EA ratio. Above the critical loading, the mixture's Tg negatively deviated from the linearly extended lines because of self‐association of the small molecules. The apparent Tg of AO300 was found to strongly depend on intermolecular hydrogen bonding number and strength. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 400–408 相似文献
167.
Cheng Wang Qing N. Chan Renlin Zhang Sanghoon Kook Evatt R. Hawkes Guan H. Yeoh Paul R. Medwell 《Journal of nanoparticle research》2016,18(5):127
The thermophoretic sampling of particulates from hot media, coupled with transmission electron microscope (TEM) imaging, is a combined approach that is widely used to derive morphological information. The identification and the measurement of the particulates, however, can be complex when the TEM images are of low contrast, noisy, and have non-uniform background signal level. The image processing method can also be challenging and time consuming, when the samples collected have large variability in shape and size, or have some degree of overlapping. In this work, a three-stage image processing sequence is presented to facilitate time-efficient automated identification and measurement of particulates from the TEM grids. The proposed processing sequence is first applied to soot samples that were thermophoretically sampled from a laminar non-premixed ethylene-air flame. The parameter values that are required to be set to facilitate the automated process are identified, and sensitivity of the results to these parameters is assessed. The same analysis process is also applied to soot samples that were acquired from an externally irradiated laminar non-premixed ethylene-air flame, which have different geometrical characteristics, to assess the morphological dependence of the proposed image processing sequence. Using the optimized parameter values, statistical assessments of the automated results reveal that the largest discrepancies that are associated with the estimated values of primary particle diameter, fractal dimension, and prefactor values of the aggregates for the tested cases, are approximately 3, 1, and 10 %, respectively, when compared with the manual measurements. 相似文献
168.
Ultrathin Mn Doped Ni-MOF Nanosheet Array for Highly Capacitive and Stable Asymmetric Supercapacitor
Dengchao Zheng Hao Wen Xun Sun Xin Guan Jie Zhang Wenli Tian Hao Feng Dr. Hongjing Wang Prof. Yadong Yao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(71):17149-17155
In this study, we demonstrate that an Mn-doped ultrathin Ni-MOF nanosheet array on nickel foam (Mn0.1-Ni-MOF/NF) serves as a highly capacitive and stable supercapacitor positive electrode. The Mn0.1-Ni-MOF/NF shows an areal capacity of 6.48 C cm−2 (specific capacity C: 1178 C g−1) at 2 mA cm−2 in 6.0 m KOH, outperforming most reported MOF-based materials. More importantly, it possesses excellent cycle stability to maintain 80.6 % capacity after 5000 cycles. An asymmetric supercapacitor device utilizing Mn0.1-Ni-MOF/NF as the positive electrode and activated carbon as the negative electrode attains a high energy density of 39.6 Wh kg−1 at 143.8 Wkg−1 power density with a capacitance retention of 83.6 % after 5000 cycles. 相似文献
169.
Dr. Yong Guan Jonathan W. Attard Prof. Dr. Anita E. Mattson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(8):1742-1747
The stereocontrolled construction of biologically relevant chromanones and tetrahydroxanthones has been achieved through the addition of alkynes to benzopyrylium trilfates under the influence of copper bis(oxazoline) catalysis. Excellent levels of enantiocontrol (63–98 % ee) are achieved in the addition of a variety of alkynes to an array of chromenones with a hydrogen in the 2-position. Promising levels of enantiocontrol (54–67 % ee) are achieved in the alkynylation of chromenones with esters in the 2-position, generating tertiary ether stereocenters resembling those frequently found in naturally occurring metabolites. 相似文献
170.
Mian Fu Xiaomei Zhuang Tianhong Zhang Ying Guan Qingbin Meng Yongjun Zhang 《Macromolecular bioscience》2020,20(9)
Leuprolide has been widely used in androgen deprivation therapy for the treatment of advanced prostate cancer, but its use is still limited due to its short half‐life. Herein, hydrogen‐bonded layer‐by‐layer films are fabricated from PEGylated leuprolide (PEG‐LEU) and tannic acid (TA). Because of its dynamic nature, the film disintegrates gradually in water and releases PEG‐LEU and TA. The in vitro release profile indicated perfect zero‐order kinetics, which is explained by the unique release mechanism. When implanted subcutaneously in male rats, the films maintain a constant serum drug level. For a 60‐bilayer film, the serum drug level is maintained constant for ≈24 days. No initial burst release is observed, suggesting that the in vivo release also follows zero‐order kinetics. Initially, an increase in the level of serum testosterone is induced by the released drug, followed by testosterone suppression to a constant level below the castrate level, which could be maintained as long as a constant serum drug level is maintained. Since the new drug carriers avoid an initial burst release of the drug and maintain a constant serum drug level and hence a constant serum testosterone level below the castrate level, these carriers are highly promising for androgen deprivation therapy. 相似文献