首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   209篇
  免费   2篇
  国内免费   1篇
化学   78篇
力学   4篇
数学   30篇
物理学   100篇
  2022年   5篇
  2021年   6篇
  2020年   1篇
  2019年   5篇
  2018年   6篇
  2017年   7篇
  2016年   5篇
  2015年   4篇
  2014年   6篇
  2013年   12篇
  2012年   13篇
  2011年   20篇
  2010年   8篇
  2009年   11篇
  2008年   14篇
  2007年   12篇
  2006年   6篇
  2005年   7篇
  2004年   7篇
  2003年   3篇
  2002年   27篇
  2001年   7篇
  2000年   2篇
  1999年   1篇
  1998年   1篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1992年   5篇
  1991年   1篇
  1990年   1篇
  1988年   1篇
  1984年   1篇
  1980年   1篇
  1979年   1篇
排序方式: 共有212条查询结果,搜索用时 15 毫秒
71.
Biomphalaria glabrata and Biomphalaria straminea have been identified as intermediate hosts for Schistosoma mansoni. Several studies have found two cell types in the hemolymph of B. glabrata (hyalinocytes and granulocytes). However, there are no studies describing the hemocytes of B. straminea. With the aim of further describing the hemocyte subsets in B. glabrata and B. straminea, we conducted a detailed study using optical microscopy and transmission electron microscopy. Based on the morphological characteristics of the cells, we identified the same types of hemocytes in two species of molluscs, namely: blast-like cells, granulocytes, type I hyalinocytes, type II hyalinocytes and type III hyalinocytes. Blast-like cells had a spherical profile with a central nucleus filling almost the whole cell. Granulocytes were characterized by presenting variable numbers of granules. Type I hyalinocytes were the most abundant cell type and displayed various cytoplasmic projections. Type II and type III hyalinocytes had never previously been reported. They were few in number and were characterized by having an eccentric nucleus. From these results, it is concluded that there are five types of cells in the hemolymph of B. glabrata and B. straminea. Further studies are now needed to identify the role of these hemocytes in the immune response of these snails.  相似文献   
72.
We consider Bell tests involving bipartite states shared between three parties. We show that the simple inclusion of a third part may greatly simplify the measurement scenario (in terms of the number of measurement settings per part) and allows the identification of previously unknown nonlocal resources.  相似文献   
73.
We investigate the temperature-dependent polymorphs in diindenoperylene (DIP) thin films on sapphire and silicon oxide substrates using in situ X-ray scattering. On both substrates the DIP unit cell is very similar to the high-temperature phase of bulk crystals, with the substrate stabilising this structure well below the temperature where a phase transition to a low-temperature phase is observed in the bulk. Lowering the substrate temperature for DIP growth leads to a change in molecular orientation and an additional polymorph appears, with both these effects being more pronounced on sapphire as compared to silicon oxide. Using real-time reciprocal-space mapping we observe an expansion of the in-plane unit cell during DIP growth, which may be due to changes in molecular orientation as well as strain in the first monolayers. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.  相似文献   
74.
In this paper we proceed into the next step of formalization of a consistent dual theory for mass dimension one spinors. This task is developed approaching the two different and complementary aspects of such duals, clarifying its algebraic structure and the so called τ-deformation. The former regards the mathematical equivalence of the recent proposed Lorentz preserving dual with the duals of algebraic spinors, from Clifford algebras, showing the consistency and generality of the new dual. Moreover, by revealing its automorphism structure, the hole of the τ-deformation and contrasting the action group orbits with other Lorentz breaking scenarios, we argue that the new mass dimension one dual theory is placed over solid and consistent basis.  相似文献   
75.
Hydrogen-bonding networks of π-extended 4,4′-bipyridines, 2,5-di(4-pyridyl)thiophene (1), 2,5-di(4-pyridyl)furan (2) and 1,4-di(4-pyridyl)benzene (3) with 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid, CA) have been investigated. The dipyridyl compounds afforded complexes 4 [(dication of 1)·(monoanion of CA)2], 5 [(dication of 2)·(dianion of CA)·(MeOH)] and 6 [(3)·(dication of 3)·(dianion of CA)·(H2O)6] with CA. X-ray structure analyses revealed the formation of unusual molecular tape and sheet structures involving N–H ?O, O–H ?O, C–H ?O and N–H ?N hydrogen bonds, where the aromatic spacer groups play an important role in constructing the unique crystal structures.  相似文献   
76.
77.
78.
Separation of the blood forms of trypanosomes from the blood of infected animals is difficult, especially in the case of Trypanosoma cruzi Y strain. Two procedures to isolate the Y strain blood forms of T. cruzi using polyvinyl pyrrolidone-coated silica (percoll) and histopaque are reported in this study. The recovery rates of parasites were 16 +/- 5 and 68 +/- 16%, respectively. The parasites isolated by these methods presented normal motility and morphology and were infective to albino mice with prepatent periods, parasitemia curves, and polymorphism patterns during the infection that were similar to those of control parasites. In addition, the preservation of surface antigens was confirmed by immunocytochemical studies.  相似文献   
79.
Chaos and multiple periods are presented for the harmonically excited unsymmetrical spring and damping system with clearance. This paper demonstrates the non-linear behaviour of the motion through simulation and experiment. Intensive care and caution are taken in the experiments to observe the chaos and the multiple periods properly. The focus in this paper is mainly on the change of the bilinear spring stiffness ratio as a prime factor by which chaotic motions occur from quasi-periodic motion. Other investigations and effects on motion are also discussed for the changing of the extent of clearance. The investigations are based on frequency response curves. To understand the dynamics of the non-linearity of this model, all possible data processing and displaying techniques are taken into account. To observe the overall phenomena of this bilinear system, the resonance curves and the bifurcation diagrams are taken thoroughly for a wide frequency region.  相似文献   
80.
A new ligand, (2-ethoxy-6-(1H imadazo[4,5-f][1,10]phenanthroline-2-yl)phenol) (HEPIP) and its three Co(III) complexes [Co(phen)2(HEPIP)](ClO4)3 (1), [Co(bpy)2(HEPIP)](ClO4)3 (2) and [Co(dmb)2(HEPIP)](ClO4)3 (3) have been synthesized and characterized. All three Co(III) complexes exhibited antitumor activity against four human tumor cell lines. The interaction of these complexes with calf thymus DNA was studied by absorption and emission spectroscopy, viscosity measurements and DNA cleavage assays. The DNA-binding constants of complexes 1, 2 and 3 were determined as 6.13 × 105, 4.46 × 105 and 3.72 × 105 M?1, respectively. The complexes appear to interact with DNA through intercalation. Studies on the mechanism of photocleavage indicated that both superoxide anion radical and singlet oxygen may play an important role.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号