全文获取类型
收费全文 | 858篇 |
免费 | 62篇 |
专业分类
920篇 |
出版年
2023年 | 6篇 |
2022年 | 5篇 |
2021年 | 19篇 |
2020年 | 7篇 |
2019年 | 16篇 |
2018年 | 20篇 |
2017年 | 14篇 |
2016年 | 24篇 |
2015年 | 40篇 |
2014年 | 47篇 |
2013年 | 52篇 |
2012年 | 64篇 |
2011年 | 61篇 |
2010年 | 41篇 |
2009年 | 37篇 |
2008年 | 54篇 |
2007年 | 63篇 |
2006年 | 46篇 |
2005年 | 42篇 |
2004年 | 37篇 |
2003年 | 45篇 |
2002年 | 33篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 12篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1976年 | 5篇 |
1974年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1964年 | 2篇 |
1960年 | 1篇 |
排序方式: 共有920条查询结果,搜索用时 0 毫秒
891.
(1) Octylglucoside stimulates an Mg2+-specific ATPase activity with CF1 preparations from different higher plants and the alga Chlamydomonas reinhardii. (2) Tentoxin at high concentrations (10?4–10?3 M) in the presence of octylglucoside further stimulates the Mg2+-ATPase activity of CF1 from tentoxin-sensitive species and inhibits the activity of CF1 from tentoxin-resistant species. The extent of tentoxin stimulation and inhibition varies among species. A maximal stimulation of over 2-fold was obtained with spinach CF1 and a maximal inhibition of 50% was obtained with C. reinhardii CF1. In Nicotiana spp., tentoxin had only a marginal effect on the Mg2+-ATPase activity induced by octylglucoside. 相似文献
892.
893.
894.
Ingmar A. F. M. Heijnen Martin J. Glennie J. G. J. van de Winkel 《Cancer immunology, immunotherapy : CII》1997,45(3-4):166-170
The class I IgG receptor (FcγRI) on cytotoxic effector cells has been reported to initiate destruction of tumour cells by
effector cells in vitro. We are aiming at developing an immunocompetent model to evaluate the cytotoxic capacity of human
FcγRI for the rejection of tumour cells in vivo. Therefore, we recently generated a transgenic mouse strain expressing human
FcγRI on monocytes, macrophages, and neutrophils. In these mice, the human receptor is up-regulated by granulocyte-colony-stimulating
factor (G-CSF) and is able to trigger cellular responses. Subsequently, in the present study the B cell lymphoma IIA1.6 cell
line is selected as a tumour target, and a human FcγRI-directed antitumour bispecific antibody (bsAb) is constructed and characterized.
Fab′ fragments of mAb 22, which bind hFcγRI at an epitope that is distinct from the ligand binding site, were chemically linked
to Fab′ fragments of rat anti-(mMHC class II antigens) mAb M5/114, yielding bsAb 22×M5/114. This bsAb was able to bind simultaneously
to hFcγRI and mMHC class II antigens in a dose-dependent fashion. Binding of 22×M5/114 to FcγRI was not inhibited in the presence
of human IgG. It is important to note that, MHC-class-II-expressing IIA1.6 lymphoma cells were lysed by whole blood from G-CSF-treated
transgenic mice in the presence of bsAb 22×M5/114. No lysis by whole blood from non-transgenic mice or from transgenic animals
that had not received G-CSF was observed. These results indicate that human FcγRI is able to mediate lysis of murine IIA1.6
lymphoma cells by transgenic effector cells via bsAb 22×M5/114. A trial with transgenic mice, evaluating the efficacy of these
hFcγRI-directed bsAb in combination with G-CSF for treatment of IIA1.6 B cell lymphoma, is currently in progress.
Accepted: 14 October 1997 相似文献
895.
Abstract The proliferation of murine spleen cells stimulated by a T-cell mitogen such as phytohemagglutinin (PHA) or concanavalin A (ConA) was significantly suppressed when the mice were immunized with either the viable cells or the sonicate of Salmonella typhimurium but not of Escherichia coli . The suppression of T-cell proliferation caused by the sonicate of S. typhimurium was completely restored by addition of phorbol 12-myristate-13-acetate (PMA), an activator of protein kinase C (PKC). Western blots using anti-phosphotyrosine antibodies showed that the mitogen-induced tyrosine phosphorylation of 120-, 106-,94-,76-,68- and 57-kDa proteins in murine splenic T-cells was inhibited in the mice immunized with the viable cells but not the sonicate of S. typhimurium . These results suggest that the inhibition caused by the sonicate involves suppression of PKC activity, whilst that produced by viable cells involves down-regulation of tyrosine phosphorylation, and both inhibitions correlate with the induction of cell-mediated immunity in mice, as evidenced by the induction of delayed-type hypersensitivity reactions. 相似文献
896.
We have investigated the putative role of nitric oxide (NO) as a modular of islet hormone release, when stimulated by the muscarinic receptor agonist–phospholipase C activator, carbachol, with special regard to whether the IP3-Ca2+ or the diacylglycerol-protein kinase C messenger systems might be involved. It was observed that the NO synthase (NOS) inhibitor NG-nitro-L-arginine methylester (L-NAME) markedly potentiated insulin release and modestly inhibited glucagon release induced by carbachol. Similarly, insulin release induced by the phorbol ester TPA (protein kinase C activator) was markedly potentiated. Glucagon release, however, was unaffected. Dynamic perifusion experiments with 45C2+-loaded islets revealed that the inhibitory action of L-NAME on carbachol-stimulated NO-production was reflected in a rapid and sustained increase in insulin secretion above carbachol controls, whereas the 45Ca2+-efflux pattern was similar in both groups with the exception of a slight elevation of 45C2+ in the L-NAME-carbachol group during the latter part of the perifusion. No difference in either insulin release or 45Ca2+-efflux pattern between the carbachol group and L-NAME-carbachol group was seen in another series of experiments with identical design but performed in the absence of extracellular Ca2+ . However, it should be noted that in the absence of extracellular Ca2+ both 45Ca2+-efflux and, especially, insulin release were greatly reduced in comparison with experiments in normal Ca2+. Further, in the presence of diazoxide, a potent K+
ATP-channel opener, plus a depolarizing concentration of K+ the NOS-inhibitor L-NAME still markedly potentiated carbachol-induced insulin release and inhibited glucagon release. The enantiomer D-NAME, which is devoid of NOS-inhibitory properties, did not affect carbachol-induced hormone release. TPA-induced hormone release in depolarized islets was not affected by either L-NAME or D-NAME. The pharmacological intracellular NO donor hydroxylamine dose-dependently inhibited insulin release stimulated by TPA. Furthermore, a series of perifusion experiments revealed that hydroxylamine greatly inhibited carbachol-induced insulin release without affecting the 45Ca2+-efflux pattern. In summary, our results suggest that the inhibitory effect of NO on carbachol-induced insulin release is not to any significant extent exerted on the IP3-Ca2+ messenger system but rather through S-nitrosylation of critical thiol-residues in protein kinase C and/or other secretion-regulatory thiol groups. In contrast, the stimulating action of NO on carbachol-induced glucagon release was, at least partially, connected to the IP3-Ca2+ messenger system. The main effects of NO on both insulin and glucagon release induced by carbachol were apparently exerted independently of membrane depolarization events. 相似文献
897.
Uri Liberman 《Journal of theoretical biology》1991,150(4):421-436
There is a simple correspondence between discrete dynamical systems associated with evolutionary game dynamics and general locus multiallele selection models with non-Mendelian segregation. When interpreted properly the payoff matrix has two components, a fitness matrix component and a segregation matrix component. The presence of segregation distortion which corresponds to a non-symmetric payoff matrix, is a source of instability. With non-symmetric payoff an ESS does not usually correspond to a stable equilibrium. It is always externally stable but does not necessarily have an internally stable equilibrium. 相似文献
898.
Michael Scantlebury Uri Shanas Keren Or-Chen Abraham Haim 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2009,154(4):551-556
One mechanism for physiological adjustment of small mammals to different habitats and different seasons is by seasonal acclimatization of their osmoregulatory system. We examined the abilities of broad-toothed field mice (Apodemus mystacinus) from different ecosystems (‘sub-alpine’ and ‘Mediterranean’) to cope with salinity stress under short day (SD) and long day (LD) photoperiod regimes. We compared urine volume, osmolarity, urea and electrolyte (sodium, potassium and chloride) concentrations. Significant differences were noted in the abilities of mice from the two ecosystems to deal with salinity load; in particular sub-alpine mice produced less concentrated urine than Mediterranean mice with SD− sub-alpine mice seeming to produce particularly dilute urine. Urea concentration generally decreased with increasing salinity, whereas sodium and potassium levels increased, however SD− sub-alpine mice behaved differently and appeared not to be able to excrete electrolytes as effectively as the other groups of mice. Differences observed provide an insight into the kinds of variability that are present within populations inhabiting different ecosystems, thus how populations may be able to respond to potential changes in their environment. Physiological data pertaining to adaptation to increased xeric conditions, as modelled by A. mystacinus, provides valuable information as to how other species may cope with potential climatic challenges. 相似文献
899.
Uri Pick 《Biochemical and biophysical research communications》1981,102(1):165-171
Incubation of the chloroplast coupling factor with fluorescein isothiocyanate inhibits the Ca-ATPase activity of the enzyme and results in incorporation of fluorescein into the α and β subunits. High concentrations of ATP prevent the inhibition and reduce the incorporation of fluorescein into the α and β subunits. Ca and Mg ions increase fluorescein isothiocyanate inhibition and fluorescein incorporation into the α, β and γ subunits. It is suggested that fluorescein isothiocyanate modifies the catalytic site of the enzyme by blocking lysine residues in the α and β subunits which are involved in the binding of ATP. 相似文献
900.
Kristina Stenström Ingmar Unkel Carl Magnus Nilsson Christopher Rääf Sören Mattsson 《Radiation and environmental biophysics》2010,49(1):97-107
This paper presents a study in which the specific activity of 14C in hair has been investigated as an easily determined bio-indicator of the integrated 14C exposure (over several months). The study includes 28 Swedish workers handling 14C-labelled compounds, or working in a 14C-enriched environment. Hair samples from personnel at a Swedish nuclear power plant showed very low levels of 14C contamination, if any. In contrast, personnel at the investigated research departments showed 14C levels in hair of up to 60% above the natural specific activity of 14C. Much higher levels, up to 80 times the natural specific activity of 14C, were found in hair from individuals working at a pharmaceutical research laboratory. This contamination was, however, not
solely an internal contamination. There were indications that most of the 14C in the hair originated from airborne 14C-compounds, which were adsorbed onto the hair. The difficulties in removing this external 14C contamination prior to analysis are discussed, as are the possibilities of using accelerator mass spectrometry to analyse
various types of samples for retrospective dose assessment. 相似文献