全文获取类型
收费全文 | 2794篇 |
免费 | 189篇 |
国内免费 | 108篇 |
出版年
2024年 | 2篇 |
2023年 | 66篇 |
2022年 | 47篇 |
2021年 | 91篇 |
2020年 | 84篇 |
2019年 | 138篇 |
2018年 | 154篇 |
2017年 | 97篇 |
2016年 | 64篇 |
2015年 | 107篇 |
2014年 | 146篇 |
2013年 | 213篇 |
2012年 | 107篇 |
2011年 | 142篇 |
2010年 | 109篇 |
2009年 | 98篇 |
2008年 | 94篇 |
2007年 | 134篇 |
2006年 | 118篇 |
2005年 | 125篇 |
2004年 | 98篇 |
2003年 | 86篇 |
2002年 | 98篇 |
2001年 | 57篇 |
2000年 | 43篇 |
1999年 | 33篇 |
1998年 | 57篇 |
1997年 | 46篇 |
1996年 | 27篇 |
1995年 | 47篇 |
1994年 | 38篇 |
1993年 | 28篇 |
1992年 | 44篇 |
1991年 | 23篇 |
1990年 | 27篇 |
1989年 | 15篇 |
1988年 | 18篇 |
1987年 | 21篇 |
1986年 | 25篇 |
1985年 | 28篇 |
1984年 | 25篇 |
1983年 | 17篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有3091条查询结果,搜索用时 506 毫秒
31.
Extracellular matrix (ECM) modulates the EGF-induced migration of liver epithelial cells in serum-free,hormone-supplemented medium 总被引:2,自引:0,他引:2
Summary The influence of the extracellular matrix (ECM) glycoproteins collagen, IV laminin (LN), and fibronectin (FN) on the in vitro
migration of epithelial cells was studied using the ECM migration track method (4) with preparations immunostained for LN
and FN. The locomotion of rat liver epithelial cells stimulated to migrate in serum-free medium by epidermal growth factor
(EGF) in the presence of the protein per cm2. Neither LN nor collagen IV decreased the number of migrating cells, indicating that the inhibition is a specific effect
of fibronectin. The data also indicate that the FN-mediated inhibition of migration is an additional and not alternative mechanism
to the well-established contact inhibition of locomotion (1) which also occurs in liver epithelial cell cultures. The system
is being used for a further analysis of the factors that influence migration of normal and neoplastic epithelial cells and
the biochemical mechanisms underlying the migration reaction.
Editor’s Statement This paper describes new and heretofore neglected aspects of EGF and fibronectin action on the migratory
behavior of cultured cells. Gordon H. Sato 相似文献
32.
用含80%1,4-丁二醇的混合溶剂,以胰蛋白酶酶促,由去八肽胰岛素(DOI)合成了去六肽胰岛素(DHI),总产率为35%。1,4-丁二醇的溶解性能好,在浓度高达80—90%时不明显抑制酶活力,DOI的氨基无需保护,溶液中无高聚物或沉淀形成。 相似文献
33.
Patsy M. Brannon Bonnie M. Orrison Norman Kretchmer 《In vitro cellular & developmental biology. Plant》1985,21(1):6-14
Summary Rat pancreatic acinar cells were isolated and cultured in Ham's F12 medium with 15% bovine calf serum. Caerulein, insulin,
somatostatin, and dexamethasone (DEX) had no effect on intracellular or secreted amylase in these cultured cells. A serum-free
medium, using Waymouth's MB 752/1 supplemented with albumin, epidermal growth factor (EGF), DEX, and HEPES, was then developed
to avoid serum factors that might mask hormonal effects. In this SF medium, pancreatic acinar, cells maintained the morphological
and ultrastructural characteristics of freshly isolated cells and secreted amylase in response to the secretagogue, carbamyl
choline. Insulin, at a concentration of 1 μg/ml, significantly increased intracellular and secreted amylase activity after
3 d. This model cell system can be used to study the regulation of the synthesis of amylase and other pancreatic enzymes in
vitro. 相似文献
34.
Summary New cell lines, designated as ML-DmDl≈10, were established from dissociated imaginal discs ofDrosophila melanogaster. The culture medium was prepared by mixing in a 1:1 ratio Cross and Sang’s M3(BF) medium, supplemented with 10% heat inactivated
fetal bovine serum (FBS), with the supernatant of a primary embryonic cell culture made in the M3(BF) medium and supplementing
this mixture with insulin. One cell line was established in the medium containing larval hemolymph instead of the primary
culture supernatan, and another was established in fresh M3(BF) medium supplemented with insulin and FBS. In these mediums,
imaginal disc cells first formed aggregates and cellular vesicles within a few weeks followed by the proliferation of thin-layered
cells around them after about 1 mo. Ten cell lines have so far been established from two kinds of imaginal discs and disc
mixtures. The ploidy of these cell lines was predominantly diploid. Population doubling time was about 50 to 70 h at 3 to
10 mo. after initiation of the culture. When the cell aggregates formed in vitro were implanted in metamorphosing larvae,
they differentiated at high frequency into adult cuticular strutures in the early phase of the primary culture. This differentiation
of aggregates was also observed, though at low frequency, in a culture maintained by dilution-transfer for 6 to 15 mo. in
vitro. 相似文献
35.
Summary Newborn rat adipocyte precursors, isolated from inguinal fat pads of 2 day-old NBR rats proliferate and undergo adipose differentiation
in defined medium in the absence of serum when cultivated on polylysine coated dishes in DME-F12 medium supplemented with
fibronectin, insulin, transferrin and FGF. After 7 days in culture in these conditions, 90% of the cells have undergone differentiation
as measured by the increase of G3PDH specific activity and by the accumulation of triglycerides in their cytoplasm. In contrast,
the cells cultivated in the presence of 10% fetal bovine serum, have a limited ability to differentiate. These results indicate
that newborn rat adipocyte precursors from inguinal fat pads do not require the presence of an undefined adipogenic factor
in order to differentiate in culture. In contrast, proliferation and differentiation are dependent on the presence of insulin
in the culture medium. Moreover, the data presented in this paper show that the rat adipocyte precursor culture represents
a rapid and reproducible system for investigating the processes of adipose tissue development and for studying the negative
and positive regulators of the adipose differentiation in a controlled environment.
This work was supported by grants from the Juvenile Diabetes Foundation, File #185221 and from the National Institutes of
Health 1 PO1 CA37589.
Editor’s Statement This paper extends to primary cultures the serum-free methods previously applied to studies of adipocyte
differentiation in established lines. The observation that serum can block differentiation in this system suggests the existence
of previously unrecognized circulating plasma or platelet factors affecting adipocyte differentiation, and the model developed
provides an assay for the identification of these factors. 相似文献
36.
Insulin (100 U/ml) stimulated protein synthesis and PGF2 release in isolated rabbit muscle, but had little effect on the rate of protein degradation. The effect of insulin persisted for at least 5 h after removal of the hormone. Indomethacin, added at the start of the incubation, inhibited the stimulatory effect of insulin on protein synthesis and PGF2 release, but did not block the binding of iodinated insulin. When added 2 h after insulin, indomethacin did not inhibit the stimulation of protein synthesis but completely inhibited the increase in PGF2 release. The results suggest that the stimulation of protein synthesis by insulin is mediated by metabolites of membrane phospholipids but that these changes are involved during the phase of response that immediately follows the binding of insulin to its receptor. 相似文献
37.
In 12 h fasted rats, rates of muscle protein synthesis were stimulated by refeeding for 1 h and by intragastric or intravenous infusion of an amino acid plus glucose mixture for 1 hr, but not by intravenous infusion of amino acids alone for 1 h. Intravenous injection of anti-insulin serum suppressed the response to feeding and to intragastric infusion, but not to intravenous infusion. It is concluded that the response of muscle protein synthesis to food intake is mediated by both insulin and amino acids acting in concert. 相似文献
38.
Akemichi Ueno Naokatu Arakaki Toshiya Oribe Yoshiro Takeda 《Molecular and cellular biochemistry》1986,70(2):121-130
Summary A two-chain polypeptide, which corresponds to amino acid residues 115–143 and 144–184(185) of bovine serum albumin, connected to each other by a disulfide bridge, potentiated the effects of insulin on glucose transport and glucose metabolism in isolated rat adipocytes. Although the peptide alone had little activity, it shifted the concentration-response curves of insulin-stimulated D-[I-14C]glucose oxidation, 2-deoxyglucose transport, and lipid synthesis from D-[U-14C]glucose to lower insulin concentrations. It also increased the maximal responses of these parameters to insulin. However, it did not affect insulin binding to adipocytes. The peptide protected insulin considerably from degradation, but this effect alone cannot account for its effect in increasing the maximal responses to the hormone, and even when degradation of a submaximal concentration of insulin was suppressed by bacitracin, the peptide still had an enhancing effect. These results suggest not only that the peptide influences a step distal to receptor-mediated insulin binding but also that inhibition of insulin degradation alone cannot explain its total effect.The peptide lost its insulin-stimulating activity completely when it was further digested with V8 or lysinespecific endopeptidase, or when it was reduced and then carboxamidomethylated or oxidized with performic acid. Similar active tryptic fragments were obtained from human and rat albumins.Insulin-stimulating peptides should be useful in studies on the mechanisms of insulin action including both the sensitivities and responsiveness of target cells to the hormone.Abbreviations ISP
insulin-stimulating peptide
- HEPES
N-(2-hydroxyethyl)piperazine-N-2-ethanesulfonic acid
- HPLC
high-performance liquid chromatography
- SDS
sodium dodecyl sulfate 相似文献
39.
Dose-response comparisons of canine plasma gastroenteropancreatic hormone responses to bombesin and the porcine gastrin-releasing peptide (GRP) 总被引:4,自引:0,他引:4
T J McDonald M A Ghatei S R Bloom T E Adrian T Mochizuki C Yanaihara N Yanaihara 《Regulatory peptides》1983,5(2):125-137
This study compares the potencies of the porcine gastrin-releasing peptide (pGRP) and bombesin, in causing elevations of canine plasma gastroenteropancreatic (GEP) levels. In the dose range 0-600 pmol . kg-1 . h-1, infusion of both peptides resulted in obvious dose-related elevations of plasma levels of gastrin, pancreatic polypeptide, enteroglucagon, immunoreactive pancreatic glucagon, and insulin. In this dose range, no significant difference in potency between the two peptides in elevating plasma levels of the above hormones was observed. The results of this study, demonstrating equimolar potency of pGRP and bombesin, are in contrast to previous studies reporting that pGRP was less potent than bombesin in causing certain bioactivities in the rat following intracranial administration of the two peptides. 相似文献
40.
Adrian S. Dobs Christiane Broussolle M. Daniel Lane 《In vitro cellular & developmental biology. Plant》1989,25(2):112-114
Summary The insulin-producing cell line RINm5F, has been used in short-term experiments to evaluate insulin secretion. We sought to
maintain the responsiveness of these cells to stimuli for up to 2 days. We examined the course of new insulin synthesis over
this period by measuring at intervals immunoreactive insulin (IRI) in two parts: IRI in the medium (M) and IRI extracted from
the cells (C). Control cells were incubated in RPMI 1640/2.8 mM glucose/10% fetal bovine serum/200 μg/ml bacitracin (to prevent
insulin degradation). The addition of dibutyryl cAMP 10 mM to the experimental dishes significantly increased total (M+C)
IRI at 48 hr to 37% above the insulin content of the control dishes (p<0.01). Theophylline 10 mM increased total (M+C) IRI
by 24% over control (p<0.05) after 24 hrs. Glucose, glyceraldehyde, leucine, arginine, glucagon and tolbutamide, other stimulants
of insulin production, had no effect. Under the experimental conditions reported here, including the use of bacitracin, IRI
synthesis can be studied for up to 48 hr.
Portions of this study have been published in abstract form for the 47th Annual Meeting of the American Diabetes Association,
Indianapolis, Indiana, 1987.
Supported in part by the American Diabetic Association, Maryland Affiliate. 相似文献