全文获取类型
收费全文 | 3214篇 |
免费 | 187篇 |
国内免费 | 12篇 |
专业分类
化学 | 2656篇 |
晶体学 | 44篇 |
力学 | 53篇 |
数学 | 342篇 |
物理学 | 318篇 |
出版年
2023年 | 21篇 |
2022年 | 43篇 |
2021年 | 42篇 |
2020年 | 45篇 |
2019年 | 60篇 |
2018年 | 41篇 |
2017年 | 26篇 |
2016年 | 93篇 |
2015年 | 112篇 |
2014年 | 115篇 |
2013年 | 195篇 |
2012年 | 237篇 |
2011年 | 262篇 |
2010年 | 121篇 |
2009年 | 142篇 |
2008年 | 221篇 |
2007年 | 215篇 |
2006年 | 212篇 |
2005年 | 188篇 |
2004年 | 156篇 |
2003年 | 123篇 |
2002年 | 135篇 |
2001年 | 51篇 |
2000年 | 32篇 |
1999年 | 44篇 |
1998年 | 25篇 |
1997年 | 34篇 |
1996年 | 39篇 |
1995年 | 29篇 |
1994年 | 28篇 |
1993年 | 23篇 |
1992年 | 24篇 |
1991年 | 20篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 20篇 |
1985年 | 17篇 |
1984年 | 12篇 |
1983年 | 16篇 |
1982年 | 15篇 |
1981年 | 6篇 |
1980年 | 15篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 8篇 |
排序方式: 共有3413条查询结果,搜索用时 0 毫秒
171.
We report the results of in situ AFM measurements examining the phase transition of bilayers formed from the zwitterionic phospholipid, DMPC, 1,2-dimyristoyl-sn-glycero-3-phosphocholine, supported on mica. The images show that the fluid to gel phase transition process features substantial tearing of the bilayer due to the density change between the two phases. The gel to fluid transition is strongly affected by the resultant stress introduced into the gel phase, which changes the degree of cooperativity, the shape of developing fluid phase regions, and the course of the transition. 相似文献
172.
Background
In the past, ciliated receptor neurons, basal cells, and supporting cells were considered the principal components of the main olfactory epithelium. Several studies reported the presence of microvillous cells but their function is unknown. A recent report showed cells in the main olfactory epithelium that express the transient receptor potential channel TrpM5 claiming that these cells are chemosensory and that TrpM5 is an intrinsic signaling component of mammalian chemosensory organs. We asked whether the TrpM5-positive cells in the olfactory epithelium are microvillous and whether they belong to a chemosensory system, i.e. are olfactory neurons or trigeminally-innervated solitary chemosensory cells. 相似文献173.
174.
175.
176.
While fluorescence can be clearly observed in resonance-stabilized acyclic anions, its occurrence is insufficient for unambiguous assignment of either ion-pairing type or anion geometry. As in cyclic, aromatic anions, the requirement for contact ion-pairing is less severe in the excited state than in the ground state. The fluorescence lifetimes of acyclic anions are affected more by the associated cation than by the type of ion-pairing. 相似文献
177.
178.
Ondeykal JG Herath KB Jayasuriya H Polishook JD Bills GF Dombrowski AW Mojena M Koch G DiSalvo J DeMartino J Guan Z Nanakorn W Morenberg CM Balick MJ Stevenson DW Slattery M Borris RP Singh SB 《Molecular diversity》2005,9(1-3):123-129
The chemokines (CXCL9, CXCL10 and CXCL11) and associated CXCR3 receptor are expressed during the inflammatory process from multiple sclerosis, atherosclerosis or organ transplantation resulting in the recruitment of lymphocytes leading to tissue damage. It is hypothesized that blocking of the ligand/CXCR3 receptor interaction has potential to provide opportunity for development of agents that would block tissue rejection. In this paper, four classes of natural product inhibitors (IC50 ranging 0.1–41 M) have been described that block the CXCR3 receptor interaction of IP-10 ligand. These include a cyclic thiopeptide (duramycin), polyketide glycosides (roselipins), steroidal glycosides (hypoglausin A and dioscin) and a novel alkyl pyridinium alkaloid that were isolated by bioassay-guided fractionation of the organic extracts derived from actinomycete, fungal, plant and marine sources and discovered using 125 I IP-10/CXCR3 binding assay. Duramycin was the most potent with an IC50 of 0.1 M. Roselipins 2A, 2B and 1A showed IC50 values of 14.6, 23.5, and 41 M, respectively. Diosgenin glycosides dioscin, hypoglaucin A and kallstroemin D exhibited IC50 values of 2.1, 0.47 and 3 M, respectively. A novel cyclic 3-alkyl pyridinium salt isolated from a sponge displayed a binding IC50 of 0.67 M. 相似文献
179.
Significant progress has been made recently in our understanding of the structure/function relationships of the catalytic C-cluster of carbon monoxide dehydrogenases. Several structures of this enzyme have been reported, some of them at very high resolution. One recurrent problem, however, is the high degree of heterogeneity within each structure, as well as between the different X-ray models. Here, we have tried to relate the structural data with the wealth of spectroscopic and biochemical information gathered over many years. As a result, we propose a catalytic cycle that is consistent with both observations and stereochemistry. We also give alternatives to one of the most difficult aspects of the cycle, namely, the location of the two electrons in the most reduced state of the C-cluster. 相似文献
180.
Wipf P Lynch SM Powis G Birmingham A Englund EE 《Organic & biomolecular chemistry》2005,3(21):3880-3882
A series of palmarumycin prodrugs and water-soluble analogs has been synthesized and assayed for inhibition of the thioredoxin-thioredoxin reductase system. Increased aqueous solubility led to an improved in vivo activity profile. 相似文献