全文获取类型
收费全文 | 21372篇 |
免费 | 2028篇 |
国内免费 | 2005篇 |
专业分类
化学 | 16133篇 |
晶体学 | 348篇 |
力学 | 742篇 |
综合类 | 153篇 |
数学 | 2128篇 |
物理学 | 5901篇 |
出版年
2024年 | 41篇 |
2023年 | 219篇 |
2022年 | 594篇 |
2021年 | 631篇 |
2020年 | 603篇 |
2019年 | 639篇 |
2018年 | 532篇 |
2017年 | 553篇 |
2016年 | 832篇 |
2015年 | 863篇 |
2014年 | 1105篇 |
2013年 | 1510篇 |
2012年 | 1805篇 |
2011年 | 1926篇 |
2010年 | 1333篇 |
2009年 | 1221篇 |
2008年 | 1586篇 |
2007年 | 1375篇 |
2006年 | 1291篇 |
2005年 | 1108篇 |
2004年 | 920篇 |
2003年 | 747篇 |
2002年 | 829篇 |
2001年 | 564篇 |
2000年 | 428篇 |
1999年 | 328篇 |
1998年 | 225篇 |
1997年 | 174篇 |
1996年 | 199篇 |
1995年 | 156篇 |
1994年 | 137篇 |
1993年 | 120篇 |
1992年 | 110篇 |
1991年 | 113篇 |
1990年 | 90篇 |
1989年 | 74篇 |
1988年 | 43篇 |
1987年 | 40篇 |
1986年 | 29篇 |
1985年 | 48篇 |
1984年 | 31篇 |
1983年 | 26篇 |
1982年 | 23篇 |
1981年 | 22篇 |
1980年 | 18篇 |
1979年 | 17篇 |
1978年 | 22篇 |
1977年 | 14篇 |
1976年 | 18篇 |
1975年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Suvarna H. Pagire Haushabhau S. Pagire Kun-Young Park Eun Jung Bae Kwang-eun Kim Minhee Kim Jihyeon Yoon Saravanan Parameswaran Jun-Ho Choi Sungmi Park Jae-Han Jeon Jin Sook Song Myung Ae Bae In-Kyu Lee Hail Kim Jae Myoung Suh Jin Hee Ahn 《Molecules (Basel, Switzerland)》2022,27(11)
Serotonin (5-hydroxytryptophan) is a hormone that regulates emotions in the central nervous system. However, serotonin in the peripheral system is associated with obesity and fatty liver disease. Because serotonin cannot cross the blood-brain barrier (BBB), we focused on identifying new tryptophan hydroxylase type I (TPH1) inhibitors that act only in peripheral tissues for treating obesity and fatty liver disease without affecting the central nervous system. Structural optimization inspired by para-chlorophenylalanine (pCPA) resulted in the identification of a series of oxyphenylalanine and heterocyclic phenylalanine derivatives as TPH1 inhibitors. Among these compounds, compound 18i with an IC50 value of 37 nM was the most active in vitro. Additionally, compound 18i showed good liver microsomal stability and did not significantly inhibit CYP and Herg. Furthermore, this TPH1 inhibitor was able to actively interact with the peripheral system without penetrating the BBB. Compound 18i and its prodrug reduced body weight gain in mammals and decreased in vivo fat accumulation. 相似文献
72.
La2Zr2O7(LZO)过渡层以其独特的物理化学性质越来越受到人们的关注。本文以乙酰丙酮镧和乙酰丙酮锆为前驱盐,丙酸为溶剂配置前驱液,用化学溶液方法(CSD)在具有立方织构的Ni-5at%W基底上制备了LZO过渡层薄膜。研究了前驱液成分、性质以及退火温度对LZO成相以及取向的影响。用常规XRD和X射线四环衍射仪分析了LZO薄膜的相成分和织构。结果显示,在1050℃下退火可以获得强立方织构的LZO薄膜,其中(222)峰的Phi扫描半高宽值为8.95°;(400)峰的Chi扫描半高宽值为6.8°。用高分辨扫描电子显微镜(FE-SEM)观察到LZO薄膜表面均匀致密,没有裂纹和空洞。 相似文献
73.
Jie Tang Yang Yang Jingjing Qu Wenhuang Ban Hao Song Zhengying Gu Yannan Yang Larry Cai Shevanuja Theivendran Yue Wang Min Zhang Chengzhong Yu 《Chemical science》2022,13(29):8507
Pyroptosis is a programmed cell death widely studied in cancer cells for tumour inhibition, but rarely in dendritic cell (DC) activation for vaccine development. Here, we report the synthesis of sodium stabilized mesoporous aluminosilicate nanoparticles as DC pyroptosis modulators and antigen carriers. By surface modification of sodium-stabilized four-coordinate aluminium species on dendritic mesoporous silica nanoparticles, the resultant Na-IVAl-DMSN significantly activated DC through caspase-1 dependent pyroptosis via pH responsive intracellular ion exchange. The released proinflammatory cellular contents further mediated DC hyperactivation with prolonged cytokine release. In vivo studies showed that Na-IVAl-DMSN induced enhanced cellular immunity mediated by natural killer (NK) cells, cytotoxic T cells, and memory T cells as well as humoral immune response. Our results provide a new principle for the design of next-generation nanoadjuvants for vaccine applications.Na-IVAl-DMSN acts as both antigen carriers and modulators to “hyperactivate” dendritic cells (DCs) via potassium (K+) efflux dependent pyroptosis, eventually leading to enhanced adaptive and innate immunity. 相似文献
74.
Minjeong Ji Hee Jung Ryu Hyeon-Man Baek Dong Min Shin Jeong Hee Hong 《Experimental & molecular medicine》2022,54(4):503
Rheumatoid arthritis (RA) is an autoimmune disease characterized by aggressive fibroblast-like synoviocytes (FLSs) and pannus formation. Various therapeutic strategies have been developed against inflammatory cytokines in RA in recent decades. Based on the migratory features of FLSs, we examined whether modulation of the migratory module attenuates RA severity. In this study, inflamed synovial fluid-stimulated FLSs exhibited enhanced migration and migratory apparatus expression, and sodium bicarbonate cotransporter n1 (NBCn1) was identified in primary cultured RA-FLSs for the first time. The NBC inhibitor S0859 attenuated the migration of FLSs induced with synovial fluid from patients with RA or with TNF-α stimulation. Inhibition of NBCs with S0859 in a collagen-induced arthritis (CIA) mouse model reduced joint swelling and destruction without blood, hepatic, or renal toxicity. Primary FLSs isolated from the CIA-induced mouse model also showed reduced migration in the presence of S0859. Our results suggest that inflammatory mediators in synovial fluid, including TNF-α, recruit NBCn1 to the plasma membrane of FLSs to provide dynamic properties and that modulation of NBCn1 could be developed into a therapeutic strategy for RA.Subject terms: Chemotaxis, Bone, Ion channel signalling, Rheumatoid arthritis, Drug development 相似文献
75.
采用固相反应法成功制备出一批Y123与Y211的摩尔比为1∶0.47的混合物,并在此混合物的基础上掺入CeO2,掺入的比例x分别为0.5wt%、1.0wt%、2.0wt%、3.0wt%、4.0wt%。采用了X-射线衍射仪对样品的晶格结构进行了分析,测量结果表明:x=1.0wt%时掺杂效果最好,同时也充分说明Y123的晶格结构与其超导电性之间存在着一种内在的必然关联。并通过对其测试临界转变温度以及转变宽度,测量结果也充分验证了上述结论。 相似文献
76.
Chang Hyeong Lee Kyung Duk Park Bongsoo Jang 《Journal of mathematical chemistry》2013,51(7):1945-1960
In this paper, we present the multistage homotopy perturbation method for finding the solution of the chemical kinetics with nonlinear reactions. We develop a general scheme for finding the analytic solution of chemical reaction networks and apply it to motivating chemical examples such as the enzyme kinetics model and the Brusselator model. We illustrate the numerical result for the models and show the accuracy of the method. 相似文献
77.
Sang‐Mi Park Kyoung‐Soo Yook Woo‐Hyung Lee Yongtaek Hong Jun‐Yeob Lee In‐Nam Kang 《Journal of polymer science. Part A, Polymer chemistry》2013,51(23):5111-5117
Two new thermally crosslinkable hole‐transporting polymers, X‐PTPA and X‐PCz, were synthesized via Yamamoto coupling reactions. The number‐averaged molecular weights (Mn) of X‐PTPA and X‐PCz were found to be 45,000 and 48,000, respectively, and therewith, polydispersity indices were of 1.8 and 1.7, respectively. Thermally crosslinked X‐PTPA and X‐PCz exhibit excellent solvent resistance and stable optoelectronic properties. The UV–visible maximum absorption peaks of X‐PTPA and X‐PCz in the thin film state are at 389 and 322 nm, respectively. The HOMO levels of X‐PTPA and X‐PCz are estimated to be ?5.27 and ?5.39 eV, respectively. Multilayered devices (ITO/crosslinked X‐PTPA or X‐PCz/SY‐PPV/LiF/Al) were fabricated with SY (SuperYellow) as the emitting layer. The maximum efficiency of the multilayered device with a crosslinked X‐PTPA layer is approximately three times higher than that of the device without a crosslinked X‐PTPA layer and much higher than that of the crosslinked X‐PCz device. This result can be explained by the observations that crosslinked X‐PTPA produces increased electron accumulation within the emitter, SY, and also efficient exciton formation due to improved charge balance. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5111–5117 相似文献
78.
DABCO-catalyzed dimerization of Morita–Baylis–Hillman acetates to synthesize a series of 3-alkyl-4-(E)-alkenyl-cyclohex-1-ene-1,4-dicarbonyl compounds in excellent yields with modest to excellent diastereoselectivity is reported. A plausible reaction mechanism is also proposed on the basis of previous literature and preliminary investigation the asymmetric version of the reaction. 相似文献
79.
In this paper, dielectric properties of various thick PVP films cured at temperatures between 125° C and 200 °C are investigated. The thicknesses of PVP films are adjusted by varying their concentration in PGMEA solvent from 10 wt% to 2.5 wt%. Through FT-IR, C–V, SEM, and AFM analyses, the optimum curing process temperatures (150 °C for 10 wt% and 7.5 wt% samples, and 175 °C for 5 wt% samples) where PET substrates can be thermally endured are proposed in terms of their low hysteresis voltage in the C–V curve (1–2 V in 10 wt% samples, below 1 V in 7.5 wt% samples, and 0.5 V in 5 wt% samples). 相似文献
80.