全文获取类型
收费全文 | 1113篇 |
免费 | 73篇 |
专业分类
1186篇 |
出版年
2023年 | 6篇 |
2022年 | 14篇 |
2021年 | 16篇 |
2020年 | 6篇 |
2019年 | 14篇 |
2018年 | 11篇 |
2017年 | 14篇 |
2016年 | 20篇 |
2015年 | 49篇 |
2014年 | 55篇 |
2013年 | 52篇 |
2012年 | 89篇 |
2011年 | 89篇 |
2010年 | 48篇 |
2009年 | 35篇 |
2008年 | 64篇 |
2007年 | 87篇 |
2006年 | 64篇 |
2005年 | 56篇 |
2004年 | 45篇 |
2003年 | 53篇 |
2002年 | 60篇 |
2001年 | 20篇 |
2000年 | 15篇 |
1999年 | 14篇 |
1998年 | 24篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 22篇 |
1994年 | 11篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 12篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有1186条查询结果,搜索用时 15 毫秒
11.
Jacques J. H. Hens Marina De Wit Lodewijk V. Dekker Frans Boomsma A. Beate Oestreicher Frank Margolis† Willem Hendrik Gispen Pierre N. E. De Graan 《Journal of neurochemistry》1993,60(4):1264-1273
Abstract: The involvement of B-50, protein kinase C (PKC), and PKC-mediated B-50 phosphorylation in the mechanism of Ca2+-induced noradrenaline (NA) release was studied in highly purified rat cerebrocortical synaptosomes permeated with streptolysin-O. Under optimal permeation conditions, 12% of the total NA content (8.9 pmol of NA/mg of synaptosomal protein) was released in a largely (>60%) ATP-dependent manner as a result of an elevation of the free Ca2+ concentration from 10?8 to 10?5M Ca2+ The Ca2+ sensitivity in the micromolar range is identical for [3H]NA and endogenous NA release, indicating that Ca2+-induced [3H]NA release originates from vesicular pools in noradrenergic synaptosomes. Ca2+-induced NA release was inhibited by either N- or C-terminal-directed anti-B-50 antibodies, confirming a role of B-50 in the process of exocytosis. In addition, both anti-B-50 antibodies inhibited PKC-mediated B-50 phosphorylation with a similar difference in inhibitory potency as observed for NA release. However, in a number of experiments, evidence was obtained challenging a direct role of PKC and PKC-mediated B-50 phosphorylation in Ca2+-induced NA release. PKC pseudosubstrate PKC19-36, which inhibited B-50 phosphorylation (IC50 value, 10?5M), failed to inhibit Ca2+-induced NA release, even when added before the Ca2+ trigger. Similar results were obtained with PKC inhibitor H-7, whereas polymyxin B inhibited B-50 phosphorylation as well as Ca2+-induced NA release. Concerning the Ca2+ sensitivity, we demonstrate that PKC-mediated B-50 phosphorylation is initiated at a slightly higher Ca2+ concentration than NA release. Moreover, phorbol ester-induced PKC down-regulation was not paralleled by a decrease in Ca2+-induced NA release from streptolysin-O-permeated synaptosomes. Finally, the Ca2+- and phorbol ester-induced NA release was found to be additive, suggesting that they stimulate release through different mechanisms. In summary, we show that B-50 is involved in Ca2+-induced NA release from streptolysin-O-permeated synaptosomes. Evidence is presented challenging a role of PKC-mediated B-50 phosphorylation in the mechanism of NA exocytosis after Ca2+ influx. An involvement of PKC or PKC-mediated B-50 phosphorylation before the Ca2+ trigger is not ruled out. We suggest that the degree of B-50 phosphorylation, rather than its phosphorylation after PKC activation itself, is important in the molecular cascade after the Ca2+ influx resulting in exocytosis of NA. 相似文献
12.
Hubloher Josephine Joy Van der Sande Lisa Schaudinn Christoph Müller Volker Averhoff Beate 《International microbiology》2023,26(3):543-550
International Microbiology - Acinetobacter baumannii is an opportunistic human pathogen that has become a global threat to healthcare institutions. This Gram-negative bacterium is one of the most... 相似文献
13.
Rhodobacter capsulatus is a member of the group α-purple bacteria which are closely related to the ancestral endosymbiont that gave rise to mitochondria. It has therefore been hypothesized that the molecular mechanisms governing protein export in α-purple bacteria have been conserved during the evolution of mitochondria. To enable analysis of protein export in α-purple bacteria we describe here the development of a homologous cell-free synthesis/export system consisting entirely of components of R. capsulatus. Translocation of precytochrome C2 into intracytoplasmic membrane vesicles of this organism was found to require the proton-motive force and proceed at a significantly higher efficiency when membranes were present during protein synthesis. Furthermore, we show that, in this cell-free system, translocation depends on a preparation of peripheral membrane proteins Which do not possess detectable SecA- and SecB-like actvities. 相似文献
14.
Cynthia G. Fields Beate Grab Janelle L. Lauer Andrew J. Miles Ying-Ching Yu Gregg B. Fields 《Letters in Peptide Science》1996,3(1):3-16
Summary The triple-helical conformation of collagen has been proposed to be important for mediation of cellular activities, such as adhesion and activation, extracellular matrix assembly, and enzyme function. We have developed synthetic protocols that allow for the study of biological activities of specific collagen sequences in triple-helical conformation. These methods primarily involve solid-phase assembly and covalent linkage of three peptide chains. The resultant triple-helical peptides have sufficient thermal stabilities to permit structural and biological characterization under physiological conditions. The present article critically reviews the various approaches for constructing synthetic triple-helices.This paper is based on a presentation given at the Symposium on Peptide Structure and Design as part of the 31st Annual ACS Western Regional Meeting held in San Diego, CA, USA, October 18–21, 1995. 相似文献
15.
Hermann Neudeck Shiao Li Oei Beate Stiemer Hartmut Hopp Renat E Graf 《The Histochemical journal》1997,29(5):419-430
Recent immunocytochemical studies have shown that placental villous trophoblasts contain the high molecular weight cytokeratin
(CK) proteins 5/6 and 17. In the case of CK 17, trophoblastic immunostaining was positive in villi covered by fibrinoid. CKs
5/6 and 17 are expressed by hyperproliferative cells. The aim of this investigation was to examine the location of these CKs
in placental infarcts, known to be demarcated by fibrinoid and hyperproliferative trophoblasts. The results were compared
with those obtained by immunostaining against Ki-67, tenascin and α1-, α6- and β1- integrins, which are involved in cell proliferation,
differentiation and regenerative processes. Furthermore, the expression of the single CKs 7, 8, 10, 13, 14, 18 and 19 was
investigated by immunocytochemistry and immunoblotting. While low and high molecular weight CKs were present in villous and
extravillous trophoblasts, only low molecular weight CKs were detected in vascular and extravascular placental smooth muscle
cells. Placental infarcts revealed different immunoreactivities in the infarct margin and centre: high molecular CKs, tenascin,
Ki-67 and oncofoetal fibronectin predominated in the infarct margin, low molecular CKs, fibrin and integrins in the centre.
The expression of tenascin and a defined change in the expression of CK 17 indicates villous repair and hyperproliferative
mechanisms in placental infarcts.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
16.
This paper deals with epidermal structures of the sphaerodactyline gecko Sphaerodactylus cinereus : adhesive pads, cutaneous sensilla and intraepidermal axon terminals.
The adhesive pad is restricted to a single terminal scale and bears approximately 6,000 setae. The setae are complex, hair-like structures which branch and sub-branch up to five times. The terminal ends are shaped like inverted cones. They provide the friction which enables the gecko to walk even on vertical glass-plates.
Cutaneous sensilla of supposed mechanoreceptive function are found in groups of three or four at the anterior free edge of all dorsal and distal scales of the digit. The sensillum consists of a circular platelet in an epidermal depression bordered by an annular furrow and two or three bristles in a central position.
Discoid axon terminals in the digital scales are located between relatively stiff structures: the corneous layers of the epidermis and a layer of tonofibrillar bundles. The axon terminals are hypothesized to be sensitive to the internal pressure depending on hyperextension of the toe. 相似文献
The adhesive pad is restricted to a single terminal scale and bears approximately 6,000 setae. The setae are complex, hair-like structures which branch and sub-branch up to five times. The terminal ends are shaped like inverted cones. They provide the friction which enables the gecko to walk even on vertical glass-plates.
Cutaneous sensilla of supposed mechanoreceptive function are found in groups of three or four at the anterior free edge of all dorsal and distal scales of the digit. The sensillum consists of a circular platelet in an epidermal depression bordered by an annular furrow and two or three bristles in a central position.
Discoid axon terminals in the digital scales are located between relatively stiff structures: the corneous layers of the epidermis and a layer of tonofibrillar bundles. The axon terminals are hypothesized to be sensitive to the internal pressure depending on hyperextension of the toe. 相似文献
17.
Kinocilia of epidermal sensory cells in fixed marine Turbellaria often terminate as flattened biconcave discs. The distal part of the ciliary axoneme curves back upon itself forming a 360 degree loop which is enveloped by the plasmalemma. In living animals this structure can be induced by the addition of sodium cacodylate, monobasic sodium phosphate, dibasic sodium phosphate, sucrose, calcium chloride, or formaldehyde to the sea water. Specimens treated with sodium chloride, glutaraldehyde, or osmium tetroxide do not show modified cilia. In animals prepared for EM at low temperature and with a buffered hypotonic fixative less kinocilia are modified than in animals treated with a buffered iso- or hypertonic fixative and at a higher temperature. It is assumed that the unusually shaped cilia, described as "paddle cilia" or "discocilia" in other invertebrates, do not represent a genuine but an artificial structure. 相似文献
18.
Monociliary receptors in interstitial Proseriata and Neorhabdocoela (Turbellaria Neoophora) 总被引:6,自引:0,他引:6
Summary The ultrastructure of monociliary receptors in 10 species of the Proseriata and Neorhabdocoela is described, with particular reference to the epidermal dendritic part.Sensory cells with a single kinocilium situated at the level of the distal epidermis membrane are considered as mechano- or chemoreceptors.There exist sensory cells with a dendrite penetrating one epidermis cell and bearing an embedded kinocilium and a collar of 8 stereocilia or ridges with a fribrillose substructure. These collared receptors probably function as mechanoreceptors.In comparison with collared sensory cells in species of other turbellarian orders, the embedded receptors in the Proseriata and Neorhabdocoela are more advanced and possess synapomorphous characteristics. With the embedded receptors a new evidence is given for the close phylogenetic relationship between the Proseriata and Neorhabdocoela.The distribution of collared cells in the animal system and their phylogenetic implication for a choanoflagellate origin of the Metazoa are briefly discussed.List of abbreviations ar
annular rootlet
- bm
basement membrane
- cb
crystalline body
- cc
collar cell
- cw
cell web
- cwt
cell web-thickening
- d
dendrite
- kc
kinocilium
- lm
longitudinal musculature
- mv
microvilli
- n
nerve
- nt
neurotubuli
- pb
parenchymal branches
- r
rootlet
- rd
ridges
- rh
rhabdite
- rm
ring musculature
- sc
stereocilia
- sd
septate desmosomes
- tm
transversal musculature
- u
ultrarhabdites
- za
zonula adhaerens 相似文献
19.
Beate Ackermann-Schmidt Roland Süssmuth Franz Lingens 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1982,699(2)
The mutagen 1,1′-hexamethylene-bis[(5-p-chlorophenyl)-biguanide] reacts at 37°C with guanosine and guanine to yield xanthosine or xanthine and oxidizes cysteine to cystine. After treatment of a guanosine-labelled DNA sample from Escherichia coli with the mutagen xanthine could be detected as a reaction product. At a slow rate the mutagen is hydrolysed spontaneously yielding urea, 1,6-hexanediol and 4-chloroaniline. The reaction mechanisms both of the hydrolysis and of the reaction with cysteine and guanosine are discussed. 相似文献
20.
Beate Sopott-Ehlers 《Hydrobiologia》1981,84(1):253-257
The Schlauchdrüsen or paracnids of Coelogynopora axi Sopott, 1972 consist of two components: a muscle cell and a secretory cell.The secretory cell is provided with a tube, which bears a border of microvilli. In the normal position the tube is situated in the interior of the secretory cell, and the microvilli stand at the inner side of the tube. After expulsion of the tube the microvilli are situated at its free surface.The evagination takes place in response to chemical stimuli and is effected by the contraction of the myofibrils of the muscle cell.The paracnids are supposed to be mechanisms of defense.However, conformities with nematocysts and spirocysts of the cnidarians do not exist.The paracnids in other species of the Coelogynoporidae, for example in Invenusta paracnida (Karling, 1966) and Carenscoilia bidentata Sopott, 1972 differ from those of C. axi in many details.Abbreviations bl-
basement lamina
- ep-
epidermis
- hd-
hemidesmosomes
- mc-
muscle cell
- mt-
microtubules
- mv-
microvilli
- nsc-
nucleus of the secretory cell
- sb-
bowl containing secretion granules
- sc-
secretory cell
- sd-
septate desmosome-like structures
- sg-
secretion granules
- t-
tube
- tf-
tonofilaments 相似文献