全文获取类型
收费全文 | 6791篇 |
免费 | 496篇 |
国内免费 | 2篇 |
出版年
2023年 | 20篇 |
2022年 | 22篇 |
2021年 | 117篇 |
2020年 | 76篇 |
2019年 | 89篇 |
2018年 | 158篇 |
2017年 | 124篇 |
2016年 | 247篇 |
2015年 | 327篇 |
2014年 | 344篇 |
2013年 | 478篇 |
2012年 | 506篇 |
2011年 | 575篇 |
2010年 | 363篇 |
2009年 | 327篇 |
2008年 | 426篇 |
2007年 | 418篇 |
2006年 | 412篇 |
2005年 | 358篇 |
2004年 | 365篇 |
2003年 | 339篇 |
2002年 | 329篇 |
2001年 | 60篇 |
2000年 | 53篇 |
1999年 | 60篇 |
1998年 | 70篇 |
1997年 | 59篇 |
1996年 | 62篇 |
1995年 | 57篇 |
1994年 | 32篇 |
1993年 | 46篇 |
1992年 | 48篇 |
1991年 | 30篇 |
1990年 | 36篇 |
1989年 | 18篇 |
1988年 | 12篇 |
1987年 | 15篇 |
1986年 | 18篇 |
1985年 | 25篇 |
1984年 | 26篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 14篇 |
1979年 | 9篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1975年 | 11篇 |
1974年 | 7篇 |
排序方式: 共有7289条查询结果,搜索用时 15 毫秒
991.
Anthocyanins: from plant to health 总被引:5,自引:0,他引:5
Anthocyanins are a group of natural occurring pigments responsible for the red-blue colour of many fruits and vegetables.
Anthocyanins are of interest for two reasons because they cannot only be used in the technological field as natural colorants
but also have important implications in the field of human health. Numerous studies indicate the potential effect that this
family of flavonoids may have in reducing the incidence of cardiovascular disease, cancer, hyperlipidemias and other chronic
diseases through the intake of anthocyanin-rich foods. This review examines existing literature in this area: from plant content
and distribution to health implications, including the effect of agronomic and genetic modifications on the anthocyanin content
of plants as well as other biotechnological factors and food processing. The bioavailability, metabolism, bioactivity, and
epidemiology of anthocyanins will also be reviewed. 相似文献
992.
Gray TR Shakleya DM Huestis MA 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2008,863(1):107-114
There are no analytical methods that simultaneously quantify nicotine, cotinine, trans-3'-hydroxycotinine, nornicotine and norcotinine in human meconium. Such a method could improve identification of in utero tobacco exposure, determine if maternal dose-meconium concentration relationships exist, and whether nicotine meconium concentrations predict neonatal outcomes. The first liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry method for simultaneous quantification of these analytes in meconium was developed and validated. Specimen preparation included homogenization, enzyme hydrolysis and solid phase extraction. The linear range was 1.25 or 5-500ng/g. Method applicability was evaluated with meconium collected from an in utero tobacco exposed infant. 相似文献
993.
There is considerable evidence that purines are vasoactive molecules involved in the regulation of blood flow. Adenosine is a well known vasodilator that also acts as a modulator of the response to other vasoactive substances. Adenosine exerts its effects by interacting with adenosine receptors. These are metabotropic G-protein coupled receptors and include four subtypes, A(1), A(2A), A(2B) and A(3). Adenosine triphosphate (ATP) is a co-transmitter in vascular neuroeffector junctions and is known to activate two distinct types of P2 receptors, P2X (ionotropic) and P2Y (metabotropic). ATP can exert either vasoconstrictive or vasorelaxant effects, depending on the P2 receptor subtype involved. Splanchnic vascular beds are of particular interest, as they receive a large fraction of the cardiac output. This review focus on purinergic receptors role in the splanchnic vasomotor control. Here, we give an overview on the distribution and diversity of effects of purinergic receptors in splanchnic vessels. Pre- and post-junctional receptormediated responses are summarized. Attention is also given to the interactions between purinergic receptors and other receptors in the splanchnic circulation. 相似文献
994.
Villalobos-Comparán M Teresa Flores-Dorantes M Teresa Villarreal-Molina M Rodríguez-Cruz M García-Ulloa AC Robles L Huertas-Vázquez A Saucedo-Villarreal N López-Alarcón M Sánchez-Muñoz F Domínguez-López A Gutiérrez-Aguilar R Menjivar M Coral-Vázquez R Hernández-Stengele G Vital-Reyes VS Acuña-Alonzo V Romero-Hidalgo S Ruiz-Gómez DG Riaño-Barros D Herrera MF Gómez-Pérez FJ Froguel P García-García E Teresa Tusié-Luna M Aguilar-Salinas CA Canizales-Quinteros S 《Obesity (Silver Spring, Md.)》2008,16(10):2296-2301
Common polymorphisms in the fat mass and obesity-associated gene (FTO) have shown strong association with obesity in several populations. In the present study, we explored the association of FTO gene polymorphisms with obesity and other biochemical parameters in the Mexican population. We also assessed FTO gene expression levels in adipose tissue of obese and nonobese individuals. The study comprised 788 unrelated Mexican-Mestizo individuals and 31 subcutaneous fat tissue biopsies from lean and obese women. FTO single-nucleotide polymorphisms (SNPs) rs9939609, rs1421085, and rs17817449 were associated with obesity, particularly with class III obesity, under both additive and dominant models (P = 0.0000004 and 0.000008, respectively). These associations remained significant after adjusting for admixture (P = 0.000003 and 0.00009, respectively). Moreover, risk alleles showed a nominal association with lower insulin levels and homeostasis model assessment of B-cell function (HOMA-B), and with higher homeostasis model assessment of insulin sensitivity (HOMA-S) only in nonobese individuals (P (dom) = 0.031, 0.023, and 0.049, respectively). FTO mRNA levels were significantly higher in subcutaneous fat tissue of class III obese individuals than in lean individuals (P = 0.043). Risk alleles were significantly associated with higher FTO expression in the class III obesity group (P = 0.047). In conclusion, FTO is a major risk factor for obesity (particularly class III) in the Mexican-Mestizo population, and is upregulated in subcutaneous fat tissue of obese individuals. 相似文献
995.
White RM Sessa A Burke C Bowman T LeBlanc J Ceol C Bourque C Dovey M Goessling W Burns CE Zon LI 《Cell Stem Cell》2008,2(2):183-189
The zebrafish is a useful model for understanding normal and cancer stem cells, but analysis has been limited to embryogenesis due to the opacity of the adult fish. To address this, we have created a transparent adult zebrafish in which we transplanted either hematopoietic stem/progenitor cells or tumor cells. In a hematopoiesis radiation recovery assay, transplantation of GFP-labeled marrow cells allowed for striking in vivo visual assessment of engraftment from 2 hr-5 weeks posttransplant. Using FACS analysis, both transparent and wild-type fish had equal engraftment, but this could only be visualized in the transparent recipient. In a tumor engraftment model, transplantation of RAS-melanoma cells allowed for visualization of tumor engraftment, proliferation, and distant metastases in as little as 5 days, which is not seen in wild-type recipients until 3 to 4 weeks. This transparent adult zebrafish serves as the ideal combination of both sensitivity and resolution for in vivo stem cell analyses. 相似文献
996.
León D Sánchez-Nogueiro J Marín-García P Miras-Portugal MA 《Neurochemistry international》2008,52(6):1148-1159
The present work reports that activation of P2X7 receptor induces synaptic vesicle release in granule neurons and phosphorylation of synapsin-I by calcium-calmodulin-dependent protein kinase II (CaMKII), which in turn modulates secretory event. ATP, in absence of magnesium, induced a concentration-dependent glutamate release with an EC50 value of 1.95 microM. The involvement of P2X7 receptor was suggested when maximal secretory response was significantly reduced by the selective P2X7 antagonist Brilliant Blue G (BBG; 100 nM) and abolished by removing extracellular Ca2+. The involvement of P2X7 receptor on synaptic vesicle release was confirmed by measuring the release of FM 1-43 dye. In this case, pharmacological activation of P2X7 was achieved with the more selective agonist 2'-3'-o-(4-benzoylbenzoyl)-adenosine 5'-triphosphate (BzATP; 100 microM) showing a significant FM 1-43 release that was blocked by BBG (100 nM), by Zn2+ ions (100 microM), both P2X7 blockers, but not by suramin (100 microM), antagonist of P2X1, P2X2, P2X3 and P2X5. In addition, BzATP, through P2X7 receptor activation, significantly increased the phosphorylation of synapsin-I, the main presynaptic target of CaMKII. Both effects mediated by BzATP were inhibited by the CaMKII inhibitors KN-62 (10 microM) and KN-93 (10 microM). These results suggest, therefore, that Ca2+ entrance mediated by P2X7 receptor induces glutamate release and in parallel synapsin-I phosphorylation. 相似文献
997.
Anxiolytic-like effects of intra-lateral septal nuclei (LSN) infusions of the neuropeptide Y (NPY) alone or combined with estradiol benzoate were assessed in ovariectomized Wistar rats in two animal models of anxiety-like behavior. In a conflict test, immediately punished responses were assessed: 17-beta-estradiol (50.0microg/rat, P<0.05) plus vehicle (intra-LSN) or intra-LSN infusions of NPY (2.5microg/microl, P<0.05; 3.0microg/mul, P<0.05) plus vehicle (systemic route) or the combination of subthreshold doses of 17-beta-estradiol (25.0microg/kg) plus intra-LSN infusions of NPY (2.0microg/mul, P<0.05) increased the amount of immediately punished reinforcers. In the elevated plus-maze test several spatial-temporal variables were evaluated: 17-beta-estradiol (50.0microg/kg, P<0.05) plus vehicle (intra-LSN) or intra-LSN infusions of NPY (2.5microg/mul, P<0.05; 3.0microg/mul, P<0.05) plus vehicle (systemic route) or the combination of subthreshold doses of 17-beta-estradiol (25.0microg/kg) plus intra-LSN infusions of NPY (2.0microg/mul, P<0.05) produced anxiolytic-like actions without affecting locomotion. It is concluded that estradiol or NPY may produce anxiolytic-like actions and that subthreshold doses of estradiol and subthreshold doses of NPY when combined produced anxiolytic-like actions. 相似文献
998.
999.
Bratsos I Bergamo A Sava G Gianferrara T Zangrando E Alessio E 《Journal of inorganic biochemistry》2008,102(4):606-617
We performed extensive studies on the kinetics of hydrolysis of a series of Ru(II)-dmso complexes containing dicarboxylate ligands, such as oxalate, malonate, succinate and 1,1-cyclobutane dicarboxylate (cbdc), derived from anticancer-active Ru(II)-dmso-Cl precursors. The in vitro antitumor activity of those compounds in comparison with their chloride precursors was evaluated against two tumor cell lines, the human KB oral carcinoma and the murine B16-F10 melanoma. The aim of this study was to assess how the nature of the anionic ligands (i.e. dicarboxylates vs. chlorides) affects the chemical behavior and the in vitro antitumor activity of Ru(II)-dmso complexes. Among the tested compounds only one complex, the dimer [fac-Ru(dmso-S)(3)(H(2)O)(mu-cbdc)](2) (5), exhibited moderate activity against both cell lines. Interestingly, this compound is the most kinetically stable in aqueous solution among those investigated. Despite the moderate in vitro activity, in an in vivo test, complex 5 exhibited no activity against both the primary tumor growth and the formation of spontaneous metastases on the MCa mammary carcinoma model. 相似文献
1000.
Kowalik-Jankowska T Biega L Kuczer M Konopińska D 《Journal of inorganic biochemistry》2008,102(8):1615-1622
The stoichiometry, stability constants and solution structure of the complexes formed in the reaction of copper(II) with hexapeptide NPTNLH, i.e. the Neobelliera Bullata Trypsin Modulating Oostatic Factor (Neb-TMOF), and its analogues DPTNLH, Ac-NPTNLH and Ac-DPTNLH have been determined by potentiometric, UV-visible, CD and EPR spectroscopic methods. Upon raising pH for Ac-NPTNLH and Ac-DPTNLH peptides, copper(II) coordination starts from the imidazole nitrogen of the His6; afterwards three deprotonated amide nitrogens are progressively involved in metal ions coordination. In a wide pH range of 4.5-8.5 for the NPTNLH and DPTNLH ligands the CuL complex dominates with the imidazole nitrogen of His6 coordinated to form a macrochelate. The N-terminal amino group of the NPTNLH and DPTNLH peptides takes part in the coordination of the metal ion in the CuL, CuH−1L and CuH−2L complexes. However, at pH above 9 the CuH−3L complex with the {NIm, 3N−} coordination mode is formed. For the CuH−2L complex the spectroscopic data clearly indicate the 4N {NH2, CO or COO−, 2N−, NIm} bonding mode with the axial coordination of the N-terminal amine group to the metal ion. 相似文献