全文获取类型
收费全文 | 398篇 |
免费 | 42篇 |
专业分类
440篇 |
出版年
2021年 | 3篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 15篇 |
2012年 | 15篇 |
2011年 | 14篇 |
2010年 | 11篇 |
2009年 | 19篇 |
2008年 | 17篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 14篇 |
2004年 | 16篇 |
2003年 | 13篇 |
2002年 | 11篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 14篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1973年 | 3篇 |
1971年 | 4篇 |
1968年 | 3篇 |
1952年 | 3篇 |
1942年 | 3篇 |
1911年 | 3篇 |
1908年 | 2篇 |
1907年 | 9篇 |
排序方式: 共有440条查询结果,搜索用时 15 毫秒
361.
L F Kress 《Journal of cellular biochemistry》1986,32(1):51-58
Human plasma serine proteinase inhibitors (serpins) gradually lost activity when incubated with catalytic amounts of snake venom or bacterial metalloproteinases. Electrophoretic analyses indicated that antithrombin III, C1-inhibitor, and alpha 2-antiplasmin had been converted by limited proteolysis into modified species which retained inhibitory activity. Further proteolytic attack resulted in the formation of inactivated inhibitors; alpha 1-proteinase inhibitor (alpha 1-antitrypsin) and alpha 1-antichymotrypsin were also enzymatically inactivated, but active intermediates were not detected. Sequence analyses indicated that the initial, noninactivating cleavage occurred in the amino-terminal region of the inhibitors. Inactivation resulted in all cases from the limited proteolysis of a single bond near, but not at, the reactive site bond in the carboxy-terminal region of the inhibitors. The results indicate that the serpins have two regions which are susceptible to limited proteolysis--one near the amino-terminal end and another in the exposed reactive site loop of the inhibitor. 相似文献
362.
A Kress 《Tissue & cell》1985,17(2):215-226
The copulatory apparatus of a primitive opisthobranch, Runcina, is described. The apparatus is comprised of the following organs: the spermatic bulb, the prostrate, the penis and the penial sac. The spermatic bulb wall consists of cuboidal epithelium with forked microvilli and densely arranged cilia. Prior to copulation the interior is tightly packed with sperm. The prostate is lined with alternating glandular and supporting cells, the latter being compressed but with a mushroom-shaped apex bearing a few forked microvilli and many cilia. The glandular cells produce differing secretions, each cell producing a single type. Large paracrystalline structures enclosed in cells close to the penial area are particularly striking. Considerable amounts of the secretory products are accumulated in the protruding cell apices. One type of inclusion is found at a later stage, packed around the sperm mass within the spermatophore; its function, and the fate of the other secretions is not yet clear. The epithelium of the penis is of more columnar structure, covered with forked microvilli and extremely long cilia which are anchored by long rootlets in the cells. Some of the cells contain large electron-dense secretory granules, others hold accumulations of small secretory vesicles in their apices. It seems likely that these contribute towards the outer layer of spermatophore. The wall of the penial sac is lined by one to two rows of flat-cuboidal cells bearing sparse forked microvilli and cilia. 相似文献
363.
Horst Kress 《Developmental biology》1982,93(1):231-239
After SDS-polyacrylamide gel electrophoresis two glycosylated glue proteins are found in the salivary glands of Drosophila virilis late third instar larvae. Synthesis of larval glue protein 1 occurs in three successive steps: at first a precursor protein with a molecular weight of about 138,000 daltons is formed. This is modified by two subsequent steps of glycosylation, the first one involving hexosamine, the second one hexoses. Studies with tunicamycin and β-hydroxynorvaline suggest that glycosylation occurs at threonine residues. Larval glue protein 2 has a molecular weight of approximately 15,000 daltons and is weakly glycosylated. The synthesis of glue proteins is stage specific. It starts at about 120 hr after oviposition and attains its maximal rate about 20 hr later. At this time the larvae leave the food. Between ecdysone release and puparium formation (146–151 hr) larval glue protein synthesis is terminated. Throughout the prepupal stage a different set of glycoproteins is synthesized. Thus, the larval-prepupal transition is accompanied by the reprogramming of glycoprotein synthesis in salivary glands. The secretion products formed during the two developmental stages seem to possess different biological functions. 相似文献
364.
M. F. Frosolono Y. Kress M. Wittner R. M. Rosenbaum 《In vitro cellular & developmental biology. Plant》1976,12(10):708-717
Summary Type II cell enriched fractions were isolated from rabbit and rat lungs using density gradient centrifugation. Cultures established
from these fractions contained predominantly cells similar in most morphological respects to type II pneumocytes. These were
in continuous replicating culture for 1 year and still exhibited contact inhibition. Membrane-bound structures reminiscent
of, but no longer strictly identical to, type II cell lamellar cytosomes were seen in cells from these long-term cultures
although their numbers were reduced in comparison to lamellar bodies in freshly isolated cells. Mitochondrial numbers and
sizes, determined morphometrically, were reduced after culture in comparison to freshly isolated type II cells and those in
situ. Phosphatidylcholine was synthesized by these cells and released into the extracellular medium. Application of laser
activated electronic sizing data, confirmed by direct micrometry, demonstrated a significant increase in cell size as a function
of culture. This sizing data, after prior confirmation by electron microscopy, was used as an aid in identifying type II cells
and macrophages in dispersion, especially with those cells derived from rabbit lungs. 相似文献
365.
366.
367.
Two new speciesGuzmania herrerae andG. scandens, that have been mistakenly identified asG. dissitiflora are described and illustrated. All three taxa belong to a natural complex of species that corresponds to the formerly recognized segregate genusMassangea E. Morren. However, without additional morphological and molecular evidence we believe it is premature to recognize this species complex as a genus separate fromGuzmania. 相似文献
368.
369.
The primary pollinator of Polynesian heliconias,Heliconia laufao andH. paka, is the Wattled Honeyeater,Foulehaio carunculata. This report is the first documentation of pollination by honeyeaters in the genusHeliconia and the first record ofF. carunculata as a pollinator of a plant species. The Polynesian heliconias bear inflorescences that produce 2–4 hermaphroditic flowers per day for a period of 2–3 months. Each flower secretes abundant nectar (125–184 l) with low sugar concentration (15–18% sucrose-equivalents, weight per weight basis) which is available at anthesis just before dawn. Ninety percent of flower visits occur between anthesis and mid-morning. The honeyeaters perch on inflorescence bracts, and probing of the flower results in pollen deposition on the head and bill from where pollen is transferred between flowers. No statements on compatibility can be made forHeliconia paka; however,Heliconia laufao appears to be self-compatible. Calculations of energetic values of nectar of the Polynesian heliconias and Daily Energy Expenditures ofF. carunculata suggest that populations ofH. laufao andH. paka serve as rich energy resources for their pollinators. 相似文献
370.
Cigarette smoke elicits leukocyte adhesion to endothelium in hamsters: Inhibition by CuZn-SOD 总被引:5,自引:0,他引:5
Hans-Anton Lehr Eberhard Kress Michael D. Menger Hans P. Friedl Christoph Hübner Karl E. Arfors Konrad Messmer 《Free radical biology & medicine》1993,14(6):573-581
Although cigarette smoking has been identified as a major risk factor for cardiovascular diseases, the underlying pathomechanism is largely unknown. Using a dorsal skinfold chamber model in Syrian golden hamsters for intravital microscopy on striated muscle microcirculation, we investigated whether cigarette smoke (CS) affects the adhesion of circulating leukocytes to the endothelium, a constant feature of early atherogenesis and a hallmark of ischemia-reperfusion injury. Awake hamsters were exposed for 5 min to the mainstream smoke of one cigarette (2R 1 research cigarette), inducing nicotine, cotinine, and carboxyhemoglobin plasma levels comparable to levels found in human smokers. In control animals (n = 7), CS exposure elicited the rolling and subsequent adhesion of fluorescently stained leukocytes to the endothelium of arterioles and postcapillary venules. Leukocyte/endothelium interaction was preceded by an early rise in xanthine oxidase activity and intravascular hemolysis. Leukocyte adhesion and xanthine oxidase (Xo) activation were significantly attenuated in hamsters pretreated with superoxide dismutase (5 mg/kg, 10 min prior to CS, n= 7), suggesting a key role of superoxide in this event. These in vitro results suggest a novel pathomechanism of CS-induced cardiovascular pathology. 相似文献