全文获取类型
收费全文 | 1049篇 |
免费 | 146篇 |
出版年
2021年 | 18篇 |
2019年 | 10篇 |
2017年 | 7篇 |
2016年 | 15篇 |
2015年 | 28篇 |
2014年 | 36篇 |
2013年 | 37篇 |
2012年 | 63篇 |
2011年 | 48篇 |
2010年 | 25篇 |
2009年 | 29篇 |
2008年 | 25篇 |
2007年 | 35篇 |
2006年 | 42篇 |
2005年 | 40篇 |
2004年 | 20篇 |
2003年 | 30篇 |
2002年 | 32篇 |
2001年 | 24篇 |
2000年 | 21篇 |
1999年 | 24篇 |
1998年 | 16篇 |
1997年 | 12篇 |
1996年 | 15篇 |
1995年 | 18篇 |
1994年 | 8篇 |
1992年 | 21篇 |
1991年 | 17篇 |
1990年 | 23篇 |
1989年 | 24篇 |
1988年 | 30篇 |
1987年 | 32篇 |
1986年 | 27篇 |
1985年 | 28篇 |
1984年 | 21篇 |
1983年 | 22篇 |
1982年 | 18篇 |
1981年 | 22篇 |
1980年 | 11篇 |
1979年 | 17篇 |
1978年 | 16篇 |
1976年 | 11篇 |
1975年 | 7篇 |
1974年 | 12篇 |
1973年 | 19篇 |
1972年 | 12篇 |
1971年 | 15篇 |
1970年 | 11篇 |
1968年 | 8篇 |
1967年 | 9篇 |
排序方式: 共有1195条查询结果,搜索用时 15 毫秒
141.
142.
Protein p0071, a major plaque protein of non-desmosomal adhering junctions,is a selective cell-type marker 总被引:1,自引:1,他引:0
Protein p0071, which originally was introduced as a member of the p120-subfamily of armadillo proteins, common to desmosomes and adhaerens junctions (AJs) and to several other cell structures (centrosomes, midbodies), has been localized by using a series of novel
mono- and polyclonal antibodies generated against various domains of the molecule. By protein analysis and immunolocalization
techniques, protein p0071 has been localized as a plaque protein in AJs of diverse epithelia and certain vascular endothelia,
in the composite junctions (areal compositae) of the intercalated disks of cardiomyocytes, and in the punctate or more extended AJs of the vast majority of cell culture
types examined, including mitotic states. Using these antibodies, we have also shown that this AJ protein occurs only rarely
or is even absent in tissues such as skeletal and smooth muscles, in a series of mesenchymal tissue cells, and in specific
desmosome-rich cells such as those of the upper layers of the epidermis and certain other stratified epithelia and Hassall
corpuscles of the thymus. We have also demonstrated that p0071 is absent from desmosomes. The occurrence of two major subtypes
of lymphatic endothelial cells, one with AJs containing p0071 and one without detectable p0071, is emphasized. Possible structural
and functional roles of p0071 are discussed in light of these new findings regarding its localization, and the addition of
p0071 to the armamentarium of cytodiagnostic cell-type markers is recommended.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
This study was supported by project grants from the German Ministry for Education and Research (BMBF) in a cooperative research
program entitled “Standardization of mesenchymal stem cells for regenerative medicine (START-MSC)” and from the Deutsche Krebshilfe
(project 10–2049) to W.W. Franke. 相似文献
143.
Rickelt S Franke WW Doerflinger Y Goerdt S Brandner JM Peitsch WK 《Cell and tissue research》2008,334(3):401-422
In the tissue integration of melanocytes and melanoma cells, an important role is attributed to cell adhesion molecules, notably
the cadherins. In cultured melanoma cells, we have previously described a more heterogeneous repertoire of cadherins than
normal, including some melanoma subtypes synthesizing the desmosomal cadherin, desmoglein 2, out of the desmosomal context.
Using biochemical and immunological characterization of junctional molecules, confocal laser scanning, and electron and immunoelectron
microscopy, we now demonstrate homo- and heterotypic cell-cell adhesions of normal epidermal melanocytes. In human epidermis,
both in situ and in cell culture, melanocytes and keratinocytes are connected by closely aligned membranes that are interspersed
by small puncta adhaerentia containing heterotypic complexes of E- and P-cadherin. Moreover, melanocytes growing in culture often begin to synthesize
desmoglein 2, which is dispersed over extended areas of intimate adhesive cell-cell associations. As desmoglein 2 is not found
in melanocytes in situ, we hypothesize that its synthesis is correlated with cell proliferation. Indeed, in tissue microarrays,
desmoglein 2 has been demonstrated in a sizable subset of nevi and primary melanomas. The biological meanings of these cell-cell
adhesion molecule arrangements, the possible diagnostic and prognostic significance of these findings, and the implications
of the heterogeneity types of melanomas are discussed.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
This work was supported in parts by grants from the Deutsche Forschungsgemeinschaft to W. K. Peitsch (project PE 896/1) and
the Deutsche Krebshilfe to W. W. Franke (project 10-2049). 相似文献
144.
P. A. Hernandez I. Franke S. K. Herzog V. Pacheco L. Paniagua H. L. Quintana A. Soto J. J. Swenson C. Tovar T. H. Valqui J. Vargas B. E. Young 《Biodiversity and Conservation》2008,17(6):1353-1366
Conservationists are increasingly relying on distribution models to predict where species are likely to occur, especially
in poorly-surveyed but biodiverse areas. Modeling is challenging in these cases because locality data necessary for model
formation are often scarce and spatially imprecise. To identify methods best suited to modeling in these conditions, we compared
the success of three algorithms (Maxent, Mahalanobis Typicalities and Random Forests) at predicting distributions of eight
bird and eight mammal species endemic to the eastern slopes of the central Andes. We selected study species to have a range
of locality sample sizes representative of the data available for endemic species of this region and also that vary in their
distribution characteristics. We found that for species that are known from moderate numbers (N = 38–94) of localities, the three methods performed similarly for species with restricted distributions but Maxent and Random
Forests yielded better results for species with wider distributions. For species with small numbers of sample localities (N = 5–21), Maxent produced the most consistently successful results, followed by Random Forests and then Mahalanobis Typicalities.
Because evaluation statistics for models derived from few localities can be suspect due to the poor spatial representation
of the evaluation data, we corroborated these results with review by scientists familiar with the species in the field. Overall,
Maxent appears to be the most capable method for modeling distributions of Andean bird and mammal species because of the consistency
of results in varying conditions, although the other methods have strengths in certain situations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
145.
Aging and chronic exercise training influence leg venous compliance. Venous compliance affects responses to an orthostatic stress; its effect on tolerance to maximal lower body negative pressure (LBNP) in the elderly is unknown. The purpose of this study was to determine the influence of age and fitness, a surrogate measure of exercise training, on calf venous compliance and tolerance to maximal LBNP in men and women. Forty participants, 10 young fit (YF; age = 22.6 +/- 0.5 yr, peak oxygen uptake = 57.1 +/- 2.0 ml.kg(-1).min(-1)), 10 young unfit (YU; 23.1 +/- 1.0 yr, 41.1 +/- 2.0 ml.kg(-1).min(-1)), 10 older fit (OF; 73.9 +/- 2.0 yr, 39.0 +/- 2.0 ml.kg(-1).min(-1)), and 10 older unfit (OU; 70.9 +/- 1.6 yr, 27.1 +/- 2.0 ml.kg(-1).min(-1)), underwent graded LBNP to presyncope or 4 min at -100 mmHg. By utilizing venous occlusion plethysmography, calf venous compliance was determined by using the first derivative of the pressure-volume relation during cuff pressure reduction. We found that the more fit groups had greater venous compliance than their unfit peers (P < 0.05) as did the young groups compared with their older peers (P < 0.05) such that OU < YU = OF < YF. LBNP tolerance did not differ between groups. In conclusion, these data suggest that aging reduces, and chronic exercise increases, venous compliance. However, these data do not support a significant influence of venous compliance on LBNP tolerance. 相似文献
146.
147.
The turbidimetric determination of folic acid concentration in serum and erythrocytes was made by means of a spectrophotometer multiscan in 35 conservatively treated patients with chronic renal failure with a minimum creatine retention of 309 mumol/l and in 63 hemodialysed patients with terminal renal insufficiency. The result showed a statistically significant diminution of serum folic acid concentration in those patients treated in a conservative manner and a significant diminution of plasmatic and erythrocytic folate++ activity in patients under hemodialysis. There was a correlation between the folic acid concentration and the hemoglobin level in both groups of patients, whereas there was no correlation to the number of leukocytes and thrombocytes. A protein deficiency diet or loss of dialysis through the capillary membrane could be found to be the cause for the loss of folic acid. The possibility of folate++ substitutive therapy and its performance was discussed and recommended for selected indications. 相似文献
148.
R Franke 《Chemico-biological interactions》1973,6(1):1-17
The results of quantitative structure-activity analysis show that the potency of polycyclic hydrocarbons as inducers of microsomal arylhydrocarbon hydroxylase (AHH) can be quantitatively described in terms of hydrophobic interactions, chemical reactivity, and the ability to participate in charge-transfer interactions. The rate-determining step in enzyme induction is probably the formation of a reactive K-region metabolite of the hydrocarbons which then reacts with a specific repressor. The same mechanism is proposed for chemical carcinogenesis on the ground of similarities in structure-activity relationships for both processes. It is suggested that AHH induction is the first step in chemical carcinogenesis. 相似文献
149.
Werner W. Franke Christine Grund Brian W. Jackson Karl Illmensee 《Differentiation; research in biological diversity》1984,25(1-3):121-141
Abstract. The ultrastructure of the day 8.5 mouse embryo has been studied by transmission electron microscopy, with special emphasis on the primary mesenchymal cells and their interaction with cells of the embryonic ectoderm and the proximal endoderm. The organization of the two polar epithelial cell layers (embryonic ectoderm and proximal endoderm), the isolated cells of the distal endoderm and the primary mesenchymal cells is described. Primary mesenchymal cells are different from embryonic ectoderm cells, from which they are derived, not only by the absence of desmosomes and intermediate-sized filaments of the cytokeratin type but also by their variable morphology not exhibiting stable polar architecture, and their numerous cytoplasmic processes which make contacts with the basal lamina of the ectoderm, the basal cell surface of the proximal endoderm, and other mesenchymal cells. Over most of the embryo the embryonic ectoderm is covered by a typical basal lamina, except for certain regions that are frequently characterized by cytoplasmic projections ('blebs') from the basal cell surface membrane. In contrast, the basal surface of the proximal endoderm is not covered by a continuous basal lamina and reveals mushroom-like protrusions of the cortical cytoplasm. Junctions between primary mesenchymal cells are numerous and include adhaerens-type formations of various sizes as well as gap junctions. Occasionally, a special type of junction between mesenchymal cells and embryonic ectoderm has been found, resulting in local interruptions of the basal lamina. The observations are discussed in relation to possible mechanisms of mesoderm formation and the drastic changes of cell character that accompany this process, including cytoskeletal changes such as the disappearance of cytokeratin filaments and the expression of vimentin. 相似文献
150.