全文获取类型
收费全文 | 8107篇 |
免费 | 851篇 |
国内免费 | 5篇 |
出版年
2022年 | 59篇 |
2021年 | 70篇 |
2019年 | 64篇 |
2018年 | 83篇 |
2017年 | 62篇 |
2016年 | 145篇 |
2015年 | 227篇 |
2014年 | 267篇 |
2013年 | 358篇 |
2012年 | 444篇 |
2011年 | 421篇 |
2010年 | 310篇 |
2009年 | 287篇 |
2008年 | 470篇 |
2007年 | 473篇 |
2006年 | 420篇 |
2005年 | 431篇 |
2004年 | 438篇 |
2003年 | 455篇 |
2002年 | 377篇 |
2001年 | 145篇 |
2000年 | 111篇 |
1999年 | 121篇 |
1998年 | 122篇 |
1997年 | 80篇 |
1996年 | 94篇 |
1995年 | 76篇 |
1994年 | 98篇 |
1993年 | 91篇 |
1992年 | 100篇 |
1991年 | 85篇 |
1990年 | 84篇 |
1989年 | 80篇 |
1988年 | 70篇 |
1987年 | 78篇 |
1986年 | 92篇 |
1985年 | 99篇 |
1984年 | 97篇 |
1983年 | 87篇 |
1982年 | 89篇 |
1981年 | 79篇 |
1980年 | 76篇 |
1979年 | 82篇 |
1978年 | 67篇 |
1977年 | 65篇 |
1976年 | 55篇 |
1975年 | 52篇 |
1974年 | 67篇 |
1973年 | 53篇 |
1972年 | 47篇 |
排序方式: 共有8963条查询结果,搜索用时 15 毫秒
1.
Scott P. Lawrence Nicholas A. Bright J. Paul Luzio Katherine Bowers 《Molecular biology of the cell》2010,21(20):3540-3551
The pH and lumenal environment of intracellular organelles is considered essential for protein sorting and trafficking through the cell. We provide the first evidence that a mammalian NHE sodium (potassium)/proton exchanger, NHE8, plays a key role in the control of protein trafficking and endosome morphology. At steady state, the majority of epitope-tagged NHE8 was found in the trans-Golgi network of HeLa M-cells, but a proportion was also localized to multivesicular bodies (MVBs). Depletion of NHE8 in HeLa M-cells with siRNA resulted in the perturbation of MVB protein sorting, as shown by an increase in epidermal growth factor degradation. Additionally, NHE8-depleted cells displayed striking perinuclear clustering of endosomes and lysosomes, and there was a ninefold increase in the cellular volume taken up by LAMP1/LBPA-positive, dense MVBs. Our data points to a role for the ion exchange activity of NHE8 being required to maintain endosome morphology, as overexpression of a nonfunctional point mutant protein (NHE8 E225Q) resulted in phenotypes similar to those seen after siRNA depletion of endogenous NHE8. Interestingly, we found that depletion of NHE8, despite its function as a sodium (potassium)/proton antiporter, did not affect the overall pH inside dense MVBs. 相似文献
2.
3.
Dr. Patrick R. Cammarata Lawrence Oakford David Cantu-Crouch Robert Wordinger 《Cell and tissue research》1987,250(3):633-640
Summary The bovine lens capsule has previously been shown to provide an optimal surface for the examination of epithelial cell interaction with a basement membrane. This native substrate has been used to investigate some initial aspects of attachment of mouse blastocysts and trophoblastic cellular outgrowth. Mouse blastocysts were presented to the cell-free humoral side of the anterior lens capsule, incubated for 72 h, and examined by scanning and transmission electron microscopy. Blastocysts hatch and attach from their zonae pellucidae by 30 h. Trophoblastic cells proliferate rapidly in a coronal direction, display extensive surface microvilli, and advance by the extension of numerous filipodia, many of which terminate with bulbous projections. These projections were shown by transmission electron microscopy to contain numerous vacuoles and polysomes. To simulate further the initial blastocyst-uterine interaction, a suspension of lens epithelial cells was introduced to the capsule and permitted to form a monolayer prior to the addition of the blastocysts. At 72 h the monolayer of lens cells remained intact. We observed that: a) lens cells appear to recede from the advancing trophoblastic cells, and b) trophoblastic cells extend beneath the monolayer of lens cells and thereby dislodge the cells from the lens capsule substrate. No infiltration of the capsule by the advancing trophoblastic cells was observed. The lens capsule appears to offer a promising system for the study of trophoblast-epithelial cell interaction on a natural basement membrane. 相似文献
4.
5.
During a 6-month period, 7252 faeces specimens were examined for Escherichia coli serotype O157:H7. Forty-nine specimens (0.7%) from 19 patients yielded this organism. Escherichia coli O157:H7 was the third most frequently isolated bacterial pathogen, following Campylobacter jejuni and (or) Salmonella sp. Although regional variation between laboratories determined whether Campylobacter jejuni or Salmonella was the primary bacterial pathogen isolated, E. coli O157:H7 was consistently isolated more frequently than either Shigella or Yersinia enterocolitica. 相似文献
6.
7.
R. M. Davydov Joanne Smieja S. A. Dikanov Y. Zang Lawrence Que Jr. M. K. Bowman 《Journal of biological inorganic chemistry》1999,4(3):292-301
Radiolytic reduction at 77 K of oxo-/hydroxo-bridged dinuclear iron(III) complexes in frozen solutions forms kinetically
stabilized, mixed-valent species in high yields that model the mixed-valent sites of non-heme, diiron proteins. The mixed-valent
species trapped at 77 K retain ligation geometry similar to the initial diferric clusters. The shapes of the mixed-valent
EPR signals depend strongly on the bridging ligands. Spectra of the Fe(II)OFe(III) species reveal an S=1/2 ground state with small g-anisotropy as characterized by the uniaxial component (g
z
–g
av /2<0.03) observable at temperatures as high as ∼100 K. In contrast, hydroxo-bridged mixed-valent species are characterized
by large g-anisotropy (g
z
–g
av /2>0.03) and are observable only below 30 K. Annealing at higher temperatures causes structural relaxation and changes in
the EPR characteristics. EPR spectral properties allow the oxo- and hydroxo-bridged, mixed-valent diiron centers to be distinguished
from each other and can help characterize the structure of mixed-valent centers in proteins.
Received: 27 June 1998 / Accepted: 25 February 1999 相似文献
8.
9.
Lawrence Que Jr. 《Journal of biological inorganic chemistry》2004,9(6):684-690
The oxygen activation mechanisms proposed for nonheme iron systems generally follow the heme paradigm in invoking the involvement of iron-peroxo and iron-oxo species in their catalytic cycles. However, the nonheme ligand environments allow for end-on and side-on dioxygen coordination and impart greater flexibility in the modes of dioxygen activation. The currently available evidence for nonheme iron-peroxo and iron-oxo intermediates is summarized and discussed in light of the ongoing discussion on the nature of the oxidant(s) in heme enzymes. 相似文献
10.