全文获取类型
收费全文 | 4640篇 |
免费 | 351篇 |
国内免费 | 1篇 |
专业分类
4992篇 |
出版年
2023年 | 33篇 |
2022年 | 88篇 |
2021年 | 130篇 |
2020年 | 81篇 |
2019年 | 126篇 |
2018年 | 167篇 |
2017年 | 142篇 |
2016年 | 177篇 |
2015年 | 236篇 |
2014年 | 251篇 |
2013年 | 348篇 |
2012年 | 345篇 |
2011年 | 368篇 |
2010年 | 252篇 |
2009年 | 214篇 |
2008年 | 216篇 |
2007年 | 225篇 |
2006年 | 162篇 |
2005年 | 153篇 |
2004年 | 128篇 |
2003年 | 114篇 |
2002年 | 103篇 |
2001年 | 85篇 |
2000年 | 108篇 |
1999年 | 76篇 |
1998年 | 57篇 |
1997年 | 28篇 |
1996年 | 31篇 |
1995年 | 26篇 |
1994年 | 13篇 |
1993年 | 17篇 |
1992年 | 21篇 |
1991年 | 20篇 |
1990年 | 17篇 |
1989年 | 25篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 21篇 |
1985年 | 15篇 |
1984年 | 26篇 |
1983年 | 23篇 |
1982年 | 23篇 |
1981年 | 14篇 |
1980年 | 34篇 |
1979年 | 28篇 |
1978年 | 27篇 |
1977年 | 25篇 |
1976年 | 13篇 |
1974年 | 12篇 |
1973年 | 12篇 |
排序方式: 共有4992条查询结果,搜索用时 15 毫秒
91.
Yann Neuzillet Xavier Paoletti Slah Ouerhani Pierre Mongiat-Artus Hany Soliman Hugues de The Mathilde Sibony Yves Denoux Vincent Molinie Aurélie Herault May-Linda Lepage Pascale Maille Audrey Renou Dimitri Vordos Claude-Clément Abbou Ashraf Bakkar Bernard Asselain Nadia Kourda Amel El Gaaied Karen Leroy Agnès Laplanche Simone Benhamou Thierry Lebret Yves Allory Fran?ois Radvanyi 《PloS one》2012,7(12)
TP53 and FGFR3 mutations are the most common mutations in bladder cancers. FGFR3 mutations are most frequent in low-grade low-stage tumours, whereas TP53 mutations are most frequent in high-grade high-stage tumours. Several studies have reported FGFR3 and TP53 mutations to be mutually exclusive events, whereas others have reported them to be independent. We carried out a meta-analysis of published findings for FGFR3 and TP53 mutations in bladder cancer (535 tumours, 6 publications) and additional unpublished data for 382 tumours. TP53 and FGFR3 mutations were not independent events for all tumours considered together (OR = 0.25 [0.18–0.37], p = 0.0001) or for pT1 tumours alone (OR = 0.47 [0.28–0.79], p = 0.0009). However, if the analysis was restricted to pTa tumours or to muscle-invasive tumours alone, FGFR3 and TP53 mutations were independent events (OR = 0.56 [0.23–1.36] (p = 0.12) and OR = 0.99 [0.37–2.7] (p = 0.35), respectively). After stratification of the tumours by stage and grade, no dependence was detected in the five tumour groups considered (pTaG1 and pTaG2 together, pTaG3, pT1G2, pT1G3, pT2-4). These differences in findings can be attributed to the putative existence of two different pathways of tumour progression in bladder cancer: the CIS pathway, in which FGFR3 mutations are rare, and the Ta pathway, in which FGFR3 mutations are frequent. TP53 mutations occur at the earliest stage of the CIS pathway, whereas they occur would much later in the Ta pathway, at the T1G3 or muscle-invasive stage. 相似文献
92.
Ezzohra Nkhili Valerie Tomao Hakima El Hajji Es‐Seddik El Boustani Farid Chemat Olivier Dangles 《Phytochemical analysis : PCA》2009,20(5):408-415
Introduction – Green tea, a popular drink with beneficial health properties, is a rich source of specific flavanols (polyphenols). There is a special interest in the water extraction of green tea polyphenols since the composition of the corresponding extracts is expected to reflect the one of green tea infusions consumed worldwide. Objective – To develop a microwave‐assisted water extraction (MWE) of green tea polyphenols. Methodology – MWE of green tea polyphenols has been investigated as an alternative to water extraction under conventional heating (CWE). The experimental conditions were selected after consideration of both temperature and extraction time. The efficiency and selectivity of the process were determined in terms of extraction time, total phenolic content, chemical composition (HPLC‐MS analysis) and antioxidant activity of the extracts. Results – By MWE (80°C, 30 min), the flavanol content of the extract reached 97.46 (± 0.08) mg of catechin equivalent/g of green tea extract, vs. only 83.06 (± 0.08) by CWE (80°C, 45 min). In particular, the concentration of the most bioactive flavanol EGCG was 77.14 (± 0.26) mg of catechin equivalent/g of green tea extract obtained by MWE, vs 64.18 (± 0.26) mg/g by CWE. Conclusion – MWE appears more efficient than CWE at both 80 and 100°C, particularly for the extraction of flavanols and hydroxycinnamic acids. Although MWE at 100°C typically affords higher yields in total phenols, MWE at 80°C appears more convenient for the extraction of the green tea‐specific and chemically sensitive flavanols. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
93.
A. Nordine C. R. Tlemcani A. El Meskaoui 《In vitro cellular & developmental biology. Plant》2014,50(1):19-25
A protocol for somatic embryogenesis was developed for Thymus hyemalis, a wild species in the Mediterranean region. First, the effects of explant type, plant growth regulators [kinetin (KIN) and 2,4-dichlorophenoxyacetic acid (2,4-D)], and genotype on callus induction were tested. For callus induction, the node was the best explant; Murashige and Skoog (MS) medium supplemented with 1.8 μM 2,4-D and 0.5 μM KIN was the best medium, and the genotype had a highly significant effect. To induce production of somatic embryos, the effects of KIN, 6-benzylaminopurine (BAP), and naphthalene acetic acid (NAA) were evaluated. After 5 wk of culture in the dark, MS medium supplemented with 4.44 μM BAP, 0.54 μM NAA, and 4.65 μM KIN gave the highest percentage (85%) of embryogenic callus and the highest number of somatic embryos (27.00) per 45 mg of callus. For germination and plant recovery, somatic embryos were transferred to MS medium without plant growth regulators and plantlet conversion from developed somatic embryos was 90%. In vitro plants with adequate growth and sufficient root systems were subsequently transplanted into a mixture of peat and vermiculite (2:1?v/v) under greenhouse conditions. The survival rate of the plantlets under ex vitro conditions was 80%. 相似文献
94.
95.
Effect of Dissemination of 2,4-Dichlorophenoxyacetic Acid (2,4-D) Degradation Plasmids on 2,4-D Degradation and on Bacterial Community Structure in Two Different Soil Horizons 总被引:5,自引:4,他引:5 下载免费PDF全文
Winnie Dejonghe Johan Goris Saïd El Fantroussi Monica Hfte Paul De Vos Willy Verstraete Eva M. Top 《Applied microbiology》2000,66(8):3297-3304
Transfer of the 2,4-dichlorophenoxyacetic acid (2,4-D) degradation plasmids pEMT1 and pJP4 from an introduced donor strain, Pseudomonas putida UWC3, to the indigenous bacteria of two different horizons (A horizon, depth of 0 to 30 cm; B horizon, depth of 30 to 60 cm) of a 2,4-D-contaminated soil was investigated as a means of bioaugmentation. When the soil was amended with nutrients, plasmid transfer and enhanced degradation of 2,4-D were observed. These findings were most striking in the B horizon, where the indigenous bacteria were unable to degrade any of the 2,4-D (100 mg/kg of soil) during at least 22 days but where inoculation with either of the two plasmid donors resulted in complete 2,4-D degradation within 14 days. In contrast, in soils not amended with nutrients, inoculation of donors in the A horizon and subsequent formation of transconjugants (105 CFU/g of soil) could not increase the 2,4-D degradation rate compared to that of the noninoculated soil. However, donor inoculation in the nonamended B-horizon soil resulted in complete degradation of 2,4-D within 19 days, while no degradation at all was observed in noninoculated soil during 89 days. With plasmid pEMT1, this enhanced degradation seemed to be due only to transconjugants (105 CFU/g of soil), since the donor was already undetectable when degradation started. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes showed that inoculation of the donors was followed by a shift in the microbial community structure of the nonamended B-horizon soils. The new 16S rRNA gene fragments in the DGGE profile corresponded with the 16S rRNA genes of 2,4-D-degrading transconjugant colonies isolated on agar plates. This result indicates that the observed change in the community was due to proliferation of transconjugants formed in soil. Overall, this work clearly demonstrates that bioaugmentation can constitute an effective strategy for cleanup of soils which are poor in nutrients and microbial activity, such as those of the B horizon. 相似文献
96.
Mesenchymal stem cell therapy: A promising cell‐based therapy for treatment of myocardial infarction 下载免费PDF全文
Ayman El‐Sayed Shafei Mahmoud Ahmed Ali Hazem G. Ghanem Ahmed I. Shehata Ahmed A. Abdelgawad Hossam R. Handal Kareem A. Talaat Ahmed E. Ashaal Amal S. El‐Shal 《The journal of gene medicine》2017,19(12)
For decades, mesenchymal stem (MSCs) cells have been used for cardiovascular diseases as regenerative therapy. This review is an attempt to summarize the types of MSCs involved in myocardial infarction (MI) therapy, as well as its possible mechanisms effects, especially the paracrine one in MI focusing on the studies (human and animal) conducted within the last 10 years. Recently, reports showed that MSC therapy could have infarct‐limiting effects after MI in both experimental and clinical trials. In this context, various types of MSCs can help cardiac regeneration by either revitalizing the cardiac stem cells or revascularizing the arteries and veins of the heart. Furthermore, MSCs could produce paracrine growth factors that increase the survival of nearby cardiomyocytes, as well as increase angiogenesis through recruitment of stem cell from bone marrow or inducing vessel growth from existing capillaries. Recent research suggests that the paracrine effects of MSCs could be mediated by extracellular vesicles including exosomes. Exosomal microRNAs (miRNAs) released by MSCs are promising therapeutic hotspot target for MI. This could be attributed to the role of miRNA in cardiac biology, including cardiac regeneration, stem cell differentiation, apoptosis, neovascularization, cardiac contractility and cardiac remodeling. Furthermore, gene‐modified MSCs could be a recent promising therapy for MI to enhance the paracrine effects of MSCs, including better homing and effective cell targeted tissue regeneration. Although MSC therapy has achieved considerable attention and progress, there are critical challenges that remains to be overcome to achieve the most effective successful cell‐based therapy in MI. 相似文献
97.
Summary The plasma membrane of Paramecium aurelia is covered with a ruthenium red stainable surface coat. Results obtained after digestion with pronase, trypsin and neuraminidase suggest the glycoprotein nature of this structure. Lipid extraction also affects the surface coat forming material. The results are consistent with the model proposed by Ginsburg and Kobata dealing with spatial configuration of the surface coat components.Authors are grateful to Mrs. D. Kucharczyk for very efficient technical assistence, to Mrs. Z. Kaminska for sectioning the material and Mr. A. Renski for help with the electron microscope service. 相似文献
98.
Anterior pituitary gland and hypothalamic 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity was measured in the immature castrated estradiol primed rat to determine if differences in enzyme activity could explain the progesterone induced reduction of bound estradiol nuclear receptors of the anterior pituitary gland but not the hypothalamus. Higher levels of 17 beta-HSD activity were found in the anterior pituitary gland as compared to the hypothalamus. The enzyme activity in the anterior pituitary gland was stimulated by progesterone administered either in combination with estradiol for 4 days or as a single injection following 4 days of estradiol priming. No progesterone effects were found on hypothalamic 17 beta-HSD. Under the experimental conditions used, progesterone administration did not alter uterine 17 beta-HSD. An increase in anterior pituitary gland and uterine 17 beta-HSD was also induced by estrogen administration. 相似文献
99.
100.