全文获取类型
收费全文 | 2066篇 |
免费 | 152篇 |
国内免费 | 3篇 |
专业分类
2221篇 |
出版年
2023年 | 18篇 |
2022年 | 47篇 |
2021年 | 77篇 |
2020年 | 47篇 |
2019年 | 53篇 |
2018年 | 65篇 |
2017年 | 62篇 |
2016年 | 87篇 |
2015年 | 143篇 |
2014年 | 134篇 |
2013年 | 168篇 |
2012年 | 178篇 |
2011年 | 169篇 |
2010年 | 93篇 |
2009年 | 92篇 |
2008年 | 107篇 |
2007年 | 90篇 |
2006年 | 94篇 |
2005年 | 81篇 |
2004年 | 76篇 |
2003年 | 58篇 |
2002年 | 46篇 |
2001年 | 19篇 |
2000年 | 13篇 |
1999年 | 16篇 |
1998年 | 18篇 |
1997年 | 17篇 |
1996年 | 16篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1971年 | 3篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1958年 | 3篇 |
1957年 | 2篇 |
1952年 | 2篇 |
排序方式: 共有2221条查询结果,搜索用时 12 毫秒
71.
Noraziah Nordin Suzy Munir Salama Shahram Golbabapour Maryam Hajrezaie Pouya Hassandarvish Behnam Kamalidehghan Nazia Abdul Majid Najihah Mohd Hashim Hanita Omar Mehran Fadaienasab Hamed Karimian Hairin Taha Hapipah Mohd Ali Mahmood Ameen Abdulla 《PloS one》2014,9(11)
A natural source of medicine, Enicosanthellum pulchrum is a tropical plant which belongs to the family Annonaceae. In this study, methanol extract from the leaves and stems of this species was evaluated for its gastroprotective potential against mucosal lesions induced by ethanol in rats. Seven groups of rats were assigned, groups 1 and 2 were given Tween 20 (10% v/v) orally. Group 3 was administered omeprazole 20 mg/kg (10% Tween 20) whilst the remaining groups received the leaf and stem extracts at doses of 150 and 300 mg/kg, respectively. After an additional hour, the rats in groups 2–7 received ethanol (95% v/v; 8 mL/kg) orally while group 1 received Tween 20 (10% v/v) instead. Rats were sacrificed after 1 h and their stomachs subjected to further studies. Macroscopically and histologically, group 2 rats showed extremely severe disruption of the gastric mucosa compared to rats pre-treated with the E. pulchrum extracts based on the ulcer index, where remarkable protection was noticed. Meanwhile, a significant percentage of inhibition was shown with the stem extract at 62% (150 mg/kg) and 65% (300 mg/kg), whilst the percentage with the leaf extract at doses of 150 and 300 mg/kg was 63% and 75%, respectively. An increase in mucus content, nitric oxide, glutathione, prostaglandin E2, superoxide dismutase, protein and catalase, and a decrease in malondialdehyde level compared to group 2 were also obtained. Furthermore, immunohistochemical staining of groups 4–7 exhibited down-regulation of Bax and up-regulation of Hsp70 proteins. The methanol extract from the leaves and the stems showed notable gastroprotective potential against ethanol. 相似文献
72.
Melgar-Fernández R Demare P Hong E Rosas MA Escalante J Muñoz-Muñiz O Juaristi E Regla I 《Bioorganic & medicinal chemistry letters》2004,14(1):191-194
The synthesis of four novel analogues of metoprolol, a well-known beta1-blocker used to reduce arterial blood pressure, is described. The preparation of (2S,2'S)-7, (2R,2'S)-7, (2R,2'R)-8, and (2S,2'R)-8 was based on the reaction of racemic 2-[4-(2'-methoxyethyl)-phenoxymethyl]-oxirane (4) with (R)- or (S)-2-amino-1-butanol. Salient characteristics of analogues 7 and 8 relative to metoprolol are the incorporation of an additional stereogenic center, as well as a methyl group and a hydroxyl function on the nitrogen-containing chain. These novel derivatives present significant hypotensive and bradycardiac activity, although no blocking action toward beta1 and beta2 adrenergic receptor. 相似文献
73.
Carvalho OS Cardoso PC Lira PM Rumi A Roche A Berne E Müller G Caldeira RL 《Memórias do Instituto Oswaldo Cruz》2004,99(5):503-507
The specific identification of Lymnaeid snails is based on a comparison of morphological characters of the shell, radula, renal and reproductive organs. However, the identification is complicated by dissection process, intra and interspecific similarity and variability of morphological characters. In the present study, polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) techniques targeted to the first and second internal transcribed spacers (ITS1 and ITS2) rDNA and to the mitochondrial 16S ribosomal gene (16S rDNAmt) were used to differentiate the species Lymnaea columella, L. viatrix, and L. diaphana from some localities of Brazil, Argentina, and Uruguay as well as to verify whether the molecular results corroborates the classical morphological method.PCR-RFLP analysis of the ITS1, ITS2, and 16S using 12 restriction enzymes revealed characteristic patterns for L. columella and L. diaphana which were concordant with the classical morphology. On the other hand, for L. viatrix populations a number of 1 to 6 profiles were generated while morphology provided the species pattern results. 相似文献
74.
Yasuiki Umezu Lazel B Augustus Dai Seito Kazuhiro Hayakawa Merric I Ross Omar Eton David A Swanson Kyogo Itoh 《Cancer immunology, immunotherapy : CII》1993,37(6):392-399
The roles of ultraviolet-B (UV) radiation in the immunogenicity of human cancer cells have not been fully studied. We have investigated the effects of UV radiation on metastatic melanoma and renal cell carcinoma cells with regard to MHC antigen expression and the ability to induce cytotoxic T lymphocyte (CTL) activity in peripheral blood mononuclear cells (PBMC) or tumor-infiltrating lymphocytes (TIL) against untreated autologous tumor cells. UV radiation respectively decreased or increased MHC class I expression of freshly isolated tumor cells or cultured tumor cells, and also decreased MHC class I expression of starved cultured tumor cells. It increased the ability of both freshly isolated and cultured tumor cells to induce CTL activity from PBMC against untreated autologous tumor cells. UV-irradiated subclones that were more susceptible to CTL lysis were more potent for CTL induction from TIL than either an untreated parental clone or a UV-irradiated subclone that was resistant to CTL lysis. In summary, UV radiation increased the ability of tumor cells to induce CTL activity without a corresponding effect on MHC antigen expression.This work was supported in part by a grant CA47891 from the National Cancer Institute, USA, a grant-in-aid of the comprehensive 10-years strategy for cancer control from ministry of a Health and Welfare, Japan, and the Ishibashi Research Fund, Japan 相似文献
75.
Simms TM Wright MR Hernandez M Perez OA Ramirez EC Martinez E Herrera RJ 《American journal of physical anthropology》2012,148(4):618-631
Although previous studies have characterized the genetic structure of populations from Haiti and Jamaica using classical and autosomal STR polymorphisms, the patrilineal influences that are present in these countries have yet to be explored. To address this lacuna, the current study aims to investigate, for the first time, the potential impact of different ancestral sources, unique colonial histories, and distinct family structures on the paternal profile of both groups. According to previous reports examining populations from the Americas, island-specific demographic histories can greatly impact population structure, including various patterns of sex-biased gene flow. Also, given the contrasting autosomal profiles provided in our earlier study (Simms et al.: Am J Phys Anthropol 142 (2010) 49-66), we hypothesize that the degree and directionality of gene flow from Europeans, Africans, Amerindians, and East Asians are dissimilar in the two countries. To test this premise, 177 high-resolution Y-chromosome binary markers and 17 Y-STR loci were typed in Haiti (n = 123) and Jamaica (n = 159) and subsequently utilized for phylogenetic comparisons to available reference collections encompassing Africa, Europe, Asia (East and South), and the New World. Our results reveal that both studied populations exhibit a predominantly South-Saharan paternal component, with haplogroups A1b-V152, A3-M32, B2-M182, E1a-M33, E1b1a-M2, E2b-M98, and R1b2-V88 comprising 77.2% and 66.7% of the Haitian and Jamaican paternal gene pools, respectively. Yet, European derived chromosomes (i.e., haplogroups G2a*-P15, I-M258, R1b1b-M269, and T-M184) were detected at commensurate levels in Haiti (20.3%) and Jamaica (18.9%), whereas Y-haplogroups indicative of Chinese [O-M175 (3.8%)] and Indian [H-M69 (0.6%) and L-M20 (0.6%)] ancestry were restricted to Jamaica. 相似文献
76.
Alessandra Micera Ilaria Puxeddu Bijorn Omar Balzamino Stefano Bonini Francesca Levi-Schaffer 《PloS one》2012,7(10)
In the conjunctiva, repeated or prolonged exposure to injury leads to tissue remodeling and fibrosis associated with dryness, lost of corneal transparency and defect of ocular function. At the site of injury, fibroblasts (FB) migrate and differentiate into myofibroblasts (myoFB), contributing to the healing process together with other cell types, cytokines and growth factors. While the physiological deletion of MyoFB is necessary to successfully end the healing process, myoFB prolonged survival characterizes the pathological process of fibrosis. The reason for myoFB persistence is poorly understood. Nerve Growth Factor (NGF), often increased in inflamed stromal conjunctiva, may represent an important molecule both in many inflammatory processes characterized by tissue remodeling and in promoting wound-healing and well-balanced repair in humans. NGF effects are mediated by the specific expression of the NGF neurotrophic tyrosine kinase receptor type 1 (trkANGFR) and/or the pan-neurotrophin glycoprotein receptor (p75NTR). Therefore, a conjunctival myoFB model (TGFβ1-induced myoFB) was developed and characterized for cell viability/proliferation as well as αSMA, p75NTR and trkANGFR expression. MyoFB were exposed to acute and chronic NGF treatment and examined for their p75NTR/trkANGFR, αSMA/TGFβ1 expression, and apoptosis. Both NGF treatments significantly increased the expression of p75NTR, associated with a deregulation of both αSMA/TGFβ1 genes. Acute and chronic NGF exposures induced apoptosis in p75NTR expressing myoFB, an effect counteracted by the specific trkANGFR and/or p75NTR inhibitors. Focused single p75NTR and double trkANGFR/p75NTR knocking-down experiments highlighted the role of p75NTR in NGF-induced apoptosis. Our current data indicate that NGF is able to trigger in vitro myoFB apoptosis, mainly via p75NTR. The trkANGFR/p75NTR ratio in favor of p75NTR characterizes this process. Due to the lack of effective pharmacological agents for balanced tissue repairs, these new findings suggest that NGF might be a suitable therapeutic tool in conditions with impaired tissue healing. 相似文献
77.
78.
Maroun Abi Ghanem Thomas Dehoux Omar F. Zouani Atef Gadalla Marie‐Christine Durrieu Bertrand Audoin 《Journal of biophotonics》2014,7(6):453-459
The reflection of picosecond ultrasonic pulses from a cell‐substrate interface is used to probe cell‐biomaterial adhesion with a subcell resolution. We culture monocytes on top of a thin biocompatible Ti metal film, supported by a transparent sapphire substrate. Low‐energy femtosecond pump laser pulses are focused at the bottom of the Ti film to a micron spot. The subsequent ultrafast thermal expansion launches a longitudinal acoustic pulse in Ti, with a broad spectrum extending up to 100 GHz. We measure the acoustic echoes reflected from the Ti‐cell interface through the transient optical reflectance changes. The time‐frequency analysis of the reflected acoustic pulses gives access to a map of the cell acoustic impedance Zc and to a map of the film‐cell interfacial stiffness K simultaneously. Variations in Zc across the cell are attributed to rigidity and density fluctuations within the cell, whereas variations in K are related to interfacial intermolecular forces and to the nano‐architecture of the transmembrane bonds. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
79.
Optimization of a lyophilized fast-disintegrating tablet (LFDT) formulation containing naratriptan hydrochloride, an antimigraine drug, was the foremost objective of the study, aiming in achieving fast headache pain relief. The Design-Expert® v10 software was used to generate formulations using D-optimal mixture design with four components: gelatin (X1), hydrolyzed gelatin (X2), glycine (X3), and mannitol (X4) of total solid material (TSM) w/w. The effect of the relative proportion of each component was determined on friability (Y1), hardness (Y2), and in vitro disintegration time (Y3), which was then applied for formulation optimization. In addition, their effect on tablet porosity was determined via scanning electron microscopy (SEM). Drug-excipient interaction was evaluated using differential scanning calorimetry (DSC). A comparative dissolution study against the conventional tablets was studied. Accelerated stability study was carried out in (Al/Al) and (Al/PVC) blister packs. An in vivo pharmacokinetic study was carried out to compare the optimized formulation and the conventional tablets. The optimized formulation’s responses were 0.30%, 3.4 kg, and 6.12 s for Y1, Y2, and Y3, respectively. No drug-excipient interaction was specified via DSC. The optimized formulation exhibited porous structure as determined via SEM. Dissolution study demonstrated complete dissolution within 1.5 min. Study indicated stability for 78 months in (Al/Al) blister packs. In vivo pharmacokinetic study demonstrated that Cmax, AUClast, and AUCinf were significantly higher for the developed formulation. As well, the Tmax was 1 h earlier than that of convenient tablet. An LFDT would achieve a faster onset of action for naratriptan compared to other formulations. 相似文献
80.
Wasia Rizwani Aneesa Fasim Deepshikha Sharma Divya J. Reddy Nabil A. M. Bin Omar Surya S. Singh 《PloS one》2014,9(8)