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21.
Dynamic properties of F-actin structure prompted suggestions (Squire, J. M., and Morris, E. P. (1998) FASEB J. 12, 761-771) that actin subdomain 2 movements play a role in thin-filament regulation. Using fluorescently labeled yeast actin mutants Q41C, Q41C/C374S, and D51C/C374S and azidonitrophenyl putrescine (ANP) Gln(41)-labeled alpha-actin, we monitored regulation-linked changes in subdomain 2. These actins had fully regulated acto-S1 ATPase activities, and emission spectra of regulated Q41C(AEDANS)/C374S and D51C(AEDANS)/C374S filaments did not reveal any calcium-dependent changes. Fluorescence energy transfer in these F-actins mostly occurred from Trp(340) and Trp(356) to 5-(2((acetyl)amino)ethyl)amino-naphthalene-1-sulfonate (AEDANS)-labeled Cys(41) or Cys(51) of adjacent same strand protomers. Our results show that fluorescence energy transfer between these residues is similar in the mostly blocked (-Ca(2+)) and closed (+Ca(2+)) states. Ca(2+) also had no effect on the excimer band in the pyrene-labeled Q41C-regulated actin, indicating virtually no change in the overlap of pyrenes on Cys(41) and Cys(374). ANP quenching of rhodamine phalloidin fluorescence showed that neither Ca(2+) nor S1 binding to regulated alpha-actin affects the phalloidin-probe distance. Taken together, our results indicate that transitions between the blocked, closed, and open regulatory states involve no significant subdomain 2 movements, and, since the cross-linked alpha-actin remains fully regulated, that subdomain 2 motions are not essential for actin regulation. 相似文献
22.
Mesenchymal stem cells: no longer second class marrow citizens 总被引:24,自引:0,他引:24
Gerson SL 《Nature medicine》1999,5(3):262-264
23.
We report a case of black grain mycetoma in a 74-years-old man who presented with a 50-yr. history of sinus-tract formation in the right foot. This is the first case of an Exophiala jeanselmeimycetoma successfully treated with itraconazole. In addition a review of the literature on this subject was done. 相似文献
24.
Staron RS Kraemer WJ Hikida RS Fry AC Murray JD Campos GE 《Histochemistry and cell biology》1999,111(2):117-123
The limb and trunk muscles of adult rats express four myosin heavy chain (MHC) isoforms, one slow (MHCI) and three fast (MHCIIa,
MHCIId, and MHCIIb). The distribution of these isoforms correlates with fiber types delineated using myofibrillar actomyosin
adenosine triphosphatase (mATPase) histochemistry. For example, type I fibers express MHCI and fiber types IIA, IID, and IIB
express MHCIIa, MHCIId, and MHCIIb, respectively. Fibers containing only one MHC isoform have been termed ”pure” fibers. Recent
evidence suggests that a population of ”hybrid” fibers exist in rat skeletal muscle which contain two MHC isoforms. The purpose
of the present investigation was to document the entire range of histochemically defined ”pure” and ”hybrid” fiber types in
untreated muscles of the young adult Fisher 344 rat hindlimb. The selected hindlimb muscles (soleus, tibialis anterior, extensor
digitorum longus, and gastrocnemius muscles) were removed from 12 male rats and analyzed for muscle fiber type distribution,
cross-sectional area, and MHC content. Care was taken to delineate eight fiber types (I, IC, IIC, IIA, IIAD, IID, IIDB, and
IIB) using refined histochemical techniques. Hybrid fibers were found to make up a considerable portion of the muscles examined
(a range of 8.8–17.8% of the total). The deep red portion of the gastrocnemius muscle contained the largest number of hybrid
fibers, most of which were the fast types IIAD (8.5±2.8%) and IIDB (5.2±2.3%). In conclusion, hybrid fibers make up a considerable
portion of normal rat limb musculature and are an important population that should not be ignored.
Accepted: 15 October 1998 相似文献
25.
26.
The role of DNA damage repair in aging of adult stem cells 总被引:3,自引:0,他引:3
DNA repair maintains genomic stability and the loss of DNA repair capacity results in genetic instability that may lead to a decline of cellular function. Adult stem cells are extremely important in the long-term maintenance of tissues throughout life. They regenerate and renew tissues in response to damage and replace senescent terminally differentiated cells that no longer function. Oxidative stress, toxic byproducts, reduced mitochondrial function and external exposures all damage DNA through base modification or mis-incorporation and result in DNA damage. As in most cells, this damage may limit the survival of the stem cell population affecting tissue regeneration and even longevity. This review examines the hypothesis that an age-related loss of DNA damage repair pathways poses a significant threat to stem cell survival and longevity. Normal stem cells appear to have strict control of gene expression and DNA replication whereas stem cells with loss of DNA repair may have altered patterns of proliferation, quiescence and differentiation. Furthermore, stem cells with loss of DNA repair may be susceptible to malignant transformation either directly or through the emergence of cancer-prone stem cells. Human diseases and animal models of loss of DNA repair provide longitudinal analysis of DNA repair processes in stem cell populations and may provide links to the physiology of aging. 相似文献
27.
Doctor Raul Dodsworth Machado Wanderley de Souza Gerson Cotta-Pereira Gustavo de Oliveira Castro 《Cell and tissue research》1976,174(3):355-366
Summary The general ultrastructure of the electrocyte, the basic unit of the electric organs of Electrophorus electricus, is analyzed. Presented herein are detailed observations of the syncytial surface, its fibrillar coat, invaginations of the plasma membrane and synaptic terminals. Using Thiéry's method glycogen granules were identified in the syncytial cytoplasm and inside the synaptic terminals, their size and structure being compatible with the muscular origin of the electric organs, to which the filamentous meshwork found in the cytoplasm may be related. Among the perinuclear-organelles, are dense bodies with crystalline patterns. The mitochondrial matrix contains dense granules, their size and structure varying according to the organ to which they belong and to the fixation method used.This work has been supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Conselho de Ensino para Graduados da UFRJ and Banco Nacional de Desenvolvimento Econômico, FUNTEC-241 相似文献
28.
Ines Gerson Robert L. Seecof Raymond L. Teplitz 《In vitro cellular & developmental biology. Plant》1976,12(9):615-622
Summary Cultures of embryonicDrosophila melanogaster cells were examined by electron microscopy and events in myogenesis were recorded. Thick and thin myofilaments, T-tubules
and sarcoplasmic reticulum all appeared at about the same time, 10.5 hr. This was about 5 hr after the final division of myoblasts
and about the time that muscle cells were elongating, aligning and fusing. Sarcoplasm typical of insect muscle was detected
by 18.5 hr, as were myotendonal and tendocuticular junctions. Two populations of myocytes were detected, the cytoplasm of
one more electron-dense than the other. The only previous report of myofibrilogenesis in invertebrate embryos had described
novel mechanisms. InDrosophila embryonic material, however, the sequence of myofibrilogenesis resembled that in post-embryonic insect or vertebrate material.
Mrs. Pilar Toribio-Fiorio provided excellent technical assistance, and Patricia Minter, the secretarial expertise.
This investigation was supported, in part, by NIH Grant NS9330 and the James Douglas Research Fund to Robert L. Seecof and
NIH Grant No. 1 RO1 CA17223-01 to Raymond L. Teplitz. 相似文献
29.
30.
R. S. Staron William J. Kraemer Robert S. Hikida David W. Reed Jerry D. Murray Gerson E. R. Campos Scott E. Gordon 《Histochemistry and cell biology》1998,110(1):73-80
The effects of two different duration spaceflights on the extent of atrophy, fiber type composition, and myosin heavy chain
(MHC) content of rat soleus muscles were compared. Adult male Fisher rats (n=12) were aboard flight STS-57 and exposed to 10 days of microgravity and adult ovariectomized female Spraque-Dawley rats
(n=12) were aboard flight STS-62 for 14 days. Soleus muscles were bilaterally removed from the flight and control animals and
frozen for subsequent analyses. Muscle wet weights, fiber types (I, IC, IIC, and IIA), cross-sectional area, and MHC content
were determined. Although a significant difference was found between the soleus wet weights of the two ground-based control
groups, they were similar with regard to MHC content (ca 90% MHCI and ca 10% MHCIIa) and fiber type composition. Unloading
of the muscles caused slow-to-fast transformations which included a decrease in the percentage of type I fibers and MHCI,
an increase in fibers classified as type IC, and the expression of two fast myosin heavy chains not found in the control rat
soleus muscles (MHCIId and MHCIIb). Although the amount of atrophy (ca 26%) and the extent of slow-to-fast transformation
(decrease in the percentage of MHCI from 90% to 82.5%) in the soleus muscles were similar between the two spaceflights, the
percentages of the fast MHCs differed. After 14 days of spaceflight, the percentage of MHCIIa was significantly lower and
the percentages of MHCIId and MHCIIb were significantly higher than the corresponding MHC content of the soleus muscles from
the 10-day animals. Indeed, MHCIId became the predominant fast MHC after 14 days in space. These data suggest fast-to-faster
transformations continued during the longer spaceflight.
Accepted: 8 January 1998 相似文献