全文获取类型
收费全文 | 2336篇 |
免费 | 78篇 |
国内免费 | 20篇 |
专业分类
化学 | 1384篇 |
晶体学 | 29篇 |
力学 | 44篇 |
数学 | 429篇 |
物理学 | 548篇 |
出版年
2022年 | 17篇 |
2021年 | 22篇 |
2020年 | 41篇 |
2019年 | 58篇 |
2018年 | 31篇 |
2017年 | 27篇 |
2016年 | 73篇 |
2015年 | 44篇 |
2014年 | 59篇 |
2013年 | 121篇 |
2012年 | 123篇 |
2011年 | 133篇 |
2010年 | 72篇 |
2009年 | 64篇 |
2008年 | 143篇 |
2007年 | 133篇 |
2006年 | 134篇 |
2005年 | 128篇 |
2004年 | 89篇 |
2003年 | 89篇 |
2002年 | 78篇 |
2001年 | 29篇 |
2000年 | 31篇 |
1999年 | 24篇 |
1998年 | 29篇 |
1997年 | 37篇 |
1996年 | 34篇 |
1995年 | 24篇 |
1994年 | 30篇 |
1993年 | 23篇 |
1992年 | 21篇 |
1991年 | 26篇 |
1990年 | 21篇 |
1989年 | 26篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1985年 | 28篇 |
1984年 | 35篇 |
1983年 | 21篇 |
1982年 | 30篇 |
1981年 | 28篇 |
1980年 | 18篇 |
1979年 | 25篇 |
1978年 | 22篇 |
1977年 | 21篇 |
1976年 | 18篇 |
1975年 | 19篇 |
1974年 | 26篇 |
1973年 | 18篇 |
1972年 | 14篇 |
排序方式: 共有2434条查询结果,搜索用时 765 毫秒
941.
Maricarmen Hernndez-Rodríguez Pablo I. Mendoza Snchez Joel Martínez Martha E. Macías Prez Erika Rosales Cruz Teresa oek Dorota Maciejewska Ren Miranda Ruvalcaba Elvia Mera Jimnez María I. Nicols-Vzquez 《Molecules (Basel, Switzerland)》2022,27(5)
Glioblastoma multiforme (GBM) represents the most malignant type of astrocytoma, with a life expectancy of two years. It has been shown that Poly (ADP-ribose) polymerase 1 (PARP-1) protein is over-expressed in GBM cells, while its expression in healthy tissue is low. In addition, perezone, a phyto-compound, is a PARP-1 inhibitor with anti-neoplastic activity. As a consequence, in the present study, both in vitro and computational evaluations of perezone and its chemically related compound, perezone angelate, as anti-GBM agents were performed. Hence, the anti-proliferative assay showed that perezone angelate induces higher cytotoxicity in the GBM cell line (U373 IC50 = 6.44 μM) than perezone (U373 IC50 = 51.20 μM) by induction of apoptosis. In addition, perezone angelate showed low cytotoxic activity in rat glial cells (IC50 = 173.66 μM). PARP-1 inhibitory activity (IC50 = 5.25 μM) and oxidative stress induction by perezone angelate were corroborated employing in vitro studies. In the other hand, the performed docking studies allowed explaining the PARP-1 inhibitory activity of perezone angelate, and ADMET studies showed its probability to permeate cell membranes and the blood–brain barrier, which is an essential characteristic of drugs to treat neurological diseases. Finally, it is essential to highlight that the results confirm perezone angelate as a potential anti-GBM agent. 相似文献
942.
943.
The contents of issues 5 and 6 for the calendar year 2013 are summarized in the current review of the journal Structural Chemistry. A brief thermochemical commentary is added to the summary of each paper. 相似文献
944.
Joel F. Liebman 《Structural chemistry》2014,25(5):1593-1595
The year 2014 has been declared “The International Year of Crystallography.” Coincidentally, it is the 50th anniversary of the death of Isidor Fankuchen, a premier pioneering practitioner of this discipline. The current study discusses some of Fankuchen’s contributions to our understanding of molecular structure and how he personally and professionally impacted the author. 相似文献
945.
Paul A. Gurr Joel M. P. Scofield Jinguk Kim Qiang Fu Sandra E. Kentish Greg G. Qiao 《Journal of polymer science. Part A, Polymer chemistry》2014,52(23):3372-3382
This article demonstrates the successful fabrication of thin‐film‐composite (TFC) membranes containing well‐defined soft‐hard‐soft triblock copolymers. Based on “hard” polyimide (PI) and “soft” polydimethylsiloxane (PDMS), these triblock copolymers (PDMS‐b‐PI‐b‐PDMS), were prepared via condensation polymerization, and end‐group allylic functionalization to prepare the polyimide component and subsequent “click” coupling with the soft azido functionalized PDMS component. The selective layer consisted of pure PDMS‐b‐PI‐b‐PDMS copolymers which were cast onto a precast crosslinked‐PDMS gutter layer which in turn was cast onto a porous polyacrylonitrile coated substrate. The TFC membranes' gas transport properties, primarily for the separation of carbon dioxide (CO2) from nitrogen (N2), were determined at 35 °C and at a feed pressure of 2 atm. The TFC membranes showed improvements in gas permselectivity with increasing PDMS weight fraction. These results demonstrate the ability for glassy, hard polymer components to be coated onto otherwise incompatible surfaces of highly permeable soft TFC substrates through covalent coupling. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3372–3382 相似文献
946.
Maja Ponikvar-Svet Diana N. Zeiger Loryn R. Keating Joel F. Liebman 《Structural chemistry》2014,25(5):1581-1592
The contents of issues 3 and 4 for the calendar year 2013 are summarized in the current review of the journal Structural Chemistry. A brief thermochemical commentary is added to the summary of each paper. 相似文献
947.
High‐performance thin film composite membranes with well‐defined poly(dimethylsiloxane)‐b‐poly(ethylene glycol) copolymer additives for CO2 separation 下载免费PDF全文
Joel M. P. Scofield Paul A. Gurr Jinguk Kim Qiang Fu Andri Halim Sandra E. Kentish Greg G. Qiao 《Journal of polymer science. Part A, Polymer chemistry》2015,53(12):1500-1511
A series of well‐defined diblock copolymers (BCPs) consisting of poly(ethylene glycol) (PEG) and poly(dimethylsiloxane) (PDMS) were synthesized and blended with commercially available PEBAX® 2533 to form the active layer of thin‐film composite (TFC) membranes, via spin‐coating. BCPs with a PEG component ranging from 1 to 10 kDa and a PDMS component ranging from 1 to 10 kDa were synthesized by a facile condensation reaction of hydroxyl terminated PEG and carboxylic acid functionalized PDMS. The BCP/PEBAX® 2533 blends up to 50 wt % on cross‐linked PDMS gutter layers were tested at 35 °C and 350 kPa. TFC membranes containing BCPs of 1 kDa PEG and 1–5 kDa PDMS produced optimal results with CO2 permeances of approximately 1000 GPU which is an increase up to 250% of the permeance of pure PEBAX® 2533 composite membranes, while maintaining a CO2/N2 selectivity of 21. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1500–1511 相似文献
948.
A surface modification has been developed which yields fused silica capillaries with switchable electroosmotic flow (anodal/cathodal). The capillary surface is a composite material consisting of unreacted silanol groups, a layer of positively charged quaternary ammonium functions, and a hydrophilic layer of long polyether chains. Because of the presence of positively and negatively charged groups, the net charge of the capillary surface can be varied from positive to negative by changing the pH of the running electrolyte, thus enabling manipulation of the magnitude and direction of the electroosmotic flow. The long polyether chains were effective in shielding biomacromolecules from the charged inner surface of the capillary, thus minimizing electrostatic interaction of the solutes with both unreacted silanols and the quaternary ammonium groups which had been introduced. As a consequence, high separation efficiencies were achieved with proteins, nucleotides, and a series of acidic oligosaccharides. 相似文献
949.
950.
The emission spectrum of iodine has been photographed in the visible region at high resolution, and 16 bands of the system have been rotationall analyzed. Centrifugal distortion constants for the B state are calculated from the empirical (RKR) potential curve using a method which employs semiclassical phase integrals. The results of the rotational analysis are processed together with earlier results to yield improved spectroscopic parameters for the B state, valid for 3 < v′ < 40. 相似文献