全文获取类型
收费全文 | 5792篇 |
免费 | 539篇 |
国内免费 | 12篇 |
出版年
2022年 | 51篇 |
2021年 | 110篇 |
2020年 | 71篇 |
2019年 | 100篇 |
2018年 | 148篇 |
2017年 | 123篇 |
2016年 | 169篇 |
2015年 | 266篇 |
2014年 | 268篇 |
2013年 | 350篇 |
2012年 | 386篇 |
2011年 | 362篇 |
2010年 | 234篇 |
2009年 | 185篇 |
2008年 | 257篇 |
2007年 | 234篇 |
2006年 | 241篇 |
2005年 | 207篇 |
2004年 | 233篇 |
2003年 | 188篇 |
2002年 | 203篇 |
2001年 | 154篇 |
2000年 | 172篇 |
1999年 | 122篇 |
1998年 | 53篇 |
1997年 | 46篇 |
1996年 | 51篇 |
1995年 | 40篇 |
1994年 | 52篇 |
1993年 | 46篇 |
1992年 | 83篇 |
1991年 | 72篇 |
1990年 | 74篇 |
1989年 | 61篇 |
1988年 | 69篇 |
1987年 | 50篇 |
1986年 | 67篇 |
1985年 | 54篇 |
1984年 | 60篇 |
1983年 | 38篇 |
1979年 | 42篇 |
1978年 | 28篇 |
1977年 | 30篇 |
1976年 | 28篇 |
1973年 | 25篇 |
1972年 | 28篇 |
1970年 | 30篇 |
1969年 | 34篇 |
1968年 | 28篇 |
1967年 | 25篇 |
排序方式: 共有6343条查询结果,搜索用时 78 毫秒
1.
A González-Fernández J Sans P Aller C de la Torre 《Cell biology international reports》1985,9(3):237-243
Bromosubstitution for most of the S period in synchronous populations of Allium cepa L. meristematic cells resulted in a delay in the late S-G2 transition point where protein synthesis is needed for later mitotic entrance to occur. This retardation in the position of the transition point was not accompanied by the expected delay in the entrance into mitosis, suggesting that such protein synthesis is a requisite, but not a timer for prophase triggering. 相似文献
2.
3.
4.
An Na+-stimulated Mg2+-transport system in human red blood cells 总被引:5,自引:0,他引:5
The initial rate of net Mg2+ efflux was measured in human red blood cells by atomic absorption. In fresh erythrocytes incubated in Na+,K+-Ringer's medium this rate was 7.3 +/- 2.8 mumol/l cells per h (mean +/- S.D. of 14 subjects) with an energy of activation of 13 200 cal/mol. Cells with total Mg2+ contents ([ Mg]i) ranging from 1.8 to 24 mmol/l cells were prepared by using a modified p-chloromercuribenzenesulphonate method. Mg2+ efflux was strongly stimulated by increases in [Mg]i and in external Na+ concentrations ([ Na]o). A kinetic analysis of Mg2+ efflux as a function of [Mg]i and [Na]o revealed the existence of two components: an Na+-stimulated Mg2+ efflux, which exhibited a Michaelian-like dependence of free internal Mg2+ content (apparent dissociation constant = 2.6 +/- 1.4 mmol/l cells; mean +/- S.D. of six subjects) and on external Na+ concentration (apparent dissociation constant = 20.5 +/- 1.9 mM; mean +/- S.D. of four subjects) and a variable maximal rate ranging from 35 to 370 mumol/l cells per h, and an Na+-independent Mg2+ efflux, which showed a linear dependence on internal Mg2+ content with a rate constant of (6.6 +/- 0.7) X 10(-3) h-1. Fluxes catalyzed by the Na+-stimulated Mg2+ carrier were partially dependent on the ATP content of the cells and completely inhibited by quinidine (IC50 = 50 microM) and by Mn2+ (IC50 = 0.5-1.0 mM). 相似文献
5.
Prof. Dr. K. v. Dalla Torre 《Plant Systematics and Evolution》1898,48(9):346-351
Ohne Zusammenfassung 相似文献
6.
Differential and integral W-values for ionization in gaseous water for electron and proton irradiation have been analyzed from the theoretical point of view for consistency between ionization and total inelastic collision cross sections. For low-energy electrons, which are ubiquitous for all primary radiations, the experimental or compiled cross sections from different sources are sometimes not consistent with one another. A practical, self-consistent procedure is outlined in such cases. The high-energy asymptotic W-values for differential and integral ionization are calculated to be 33.7 and 34.7 eV, respectively, for electron irradiation and 34.6 and 32.5 eV, respectively, for proton irradiation. The computed variations of the W-values with energy are generally in good agreement with experiment. Integral primary W-values due only to the interactions between the incident particle and the water vapor are calculated to be 43.5 and 45.0 eV for electrons and protons, respectively, in the high-energy asymptotic limit. 相似文献
7.
Summary Pollen mother cells at early meiotic prophase fromFritillaria lanceolata, F. mutica, Tulbaghia violacea, the lily “Formobel”,Triticum aegilopoides, T. dicoccoides, T. aestivum and synaptic and asynaptic forms ofT. durum were studied in thin sections with the electron microscope (a) in relation to distribution of nuclear pores (b) in respect
of fine structure of the pore complex in those of the first four. The pores were distributed in random clusters during leptotene
to pachytene in all plants, except in the two forms ofT. durum where there were either no pores or so few that they were not detectable. Probably correlated with this, the two membranes
of the nuclear envelope were often widely separated and frequently sacculated. No pores were seen at leptotene in the part
of the envelope to which, in theFritillarias and lily, the nucleolus was adpressed at this time. Evidence supporting a recent model which proposes that annuli are composed
of three rings of eight granular subunits was obtained. These subunits as well as a dense central element, observed in most
pores, were composed of filaments about 3 nm in diameter and evidently protein in character. There was evidence of a continuity
between filaments in the central element and those in the rings of subunits which encircle the pore aperture at both the nuclear
and cytoplasmic sides of the pore. In profiles of pores knobbed filaments were sometimes seen extending laterally from the
pore wall into the perinuclear space at two sides. Questions concerning the role of the annulus are discussed.
The author wish to thank Mr. R. F. Scott for construction to the model. 相似文献
8.
9.
10.