全文获取类型
收费全文 | 1417篇 |
免费 | 80篇 |
国内免费 | 6篇 |
出版年
2024年 | 2篇 |
2023年 | 21篇 |
2022年 | 48篇 |
2021年 | 56篇 |
2020年 | 56篇 |
2019年 | 74篇 |
2018年 | 63篇 |
2017年 | 50篇 |
2016年 | 64篇 |
2015年 | 82篇 |
2014年 | 88篇 |
2013年 | 124篇 |
2012年 | 91篇 |
2011年 | 110篇 |
2010年 | 63篇 |
2009年 | 58篇 |
2008年 | 47篇 |
2007年 | 46篇 |
2006年 | 40篇 |
2005年 | 36篇 |
2004年 | 37篇 |
2003年 | 24篇 |
2002年 | 22篇 |
2001年 | 2篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 9篇 |
1991年 | 11篇 |
1990年 | 15篇 |
1989年 | 13篇 |
1988年 | 22篇 |
1987年 | 15篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1975年 | 4篇 |
1957年 | 1篇 |
1956年 | 2篇 |
排序方式: 共有1503条查询结果,搜索用时 15 毫秒
191.
192.
193.
Musca domestica Linnaeus (house fly, Diptera: Muscidae) is a major veterinary and medical important pest all over the world. These flies have ability to develop resistance to insecticides. The present trial was performed to discover the inheritance mode (autosomal, dominance, number of genes involved) and preliminary mechanism of methoxyfenozide resistance in order to provide basic information necessary to develop resistance management strategy for this pest. A strain of M. domestica (MXY-SEL) was exposed to methoxyfenozide for 44 generations which developed a 5253.90-fold level of resistance to methoxyfenozide. The overlapping fiducial limits of LC50 values of the reciprocal crosses, F1 (MXY-SEL ♂?×?Susceptible ♀) and F1? (MXY-SEL ♀?×?Susceptible ♂), suggest that inheritance of methoxyfenozide resistance was an autosomal and likely completely dominant trait (DLC?=?0.93 and 0.94 for F1 and F1?, respectively). Backcrosses of the F1 with the parental MXY-SEL or Susceptible population predict a polygenic mode of inheritance. Piperonyl butoxide significantly altered the LC50 values, suggesting enhanced detoxification by cytochrome P450-dependent monooxygenases is a major mechanism of resistance to methoxyfenozide in the MXY-SEL strain. The estimated realized heritability was 0.07 for methoxyfenozide. These results would be helpful for the better management of M. domestica. 相似文献
194.
The association of the placental MTHFR 3′‐UTR polymorphisms,promoter methylation,and MTHFR expression with preeclampsia
下载免费PDF全文
![点击此处可从《Journal of cellular biochemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
195.
196.
Hossein Motedayyen Abbas Rezaei Amir-Hassan Zarnani Nader Tajik 《Reproductive biology》2018,18(2):182-188
Unexplained recurrent spontaneous abortion (URSA) has been assumed to be caused by a defect in maternal immunological tolerance to the fetus. Human amniotic epithelial cells (hAECs) have stem cell-like features and the ability to modulate the innate and adoptive immune responses. This study aimed to investigate whether hAECs have immunomodulatory effects on naive CD4+ T cells from URSA patients. hAECs were obtained from 15 healthy pregnant women and phenotypic profile of hAECs was determined by flow cytometry. Naive CD4+ T cells were isolated from 25 URSA patients using an immunomagnetic separation method. Naive T cells were stimulated with anti-CD3/anti-CD28 antibodies and co-cultured with different numbers of hAECs for 3 and 6 days. Immunomodulatory effect of hAECs on activation of stimulated T cell was assessed by flow cytometry and Enzyme-linked immunoasorbent assay (ELISA). The hAECs effect on pro-inflammatory cytokines production of activated T cells was also measured by ELISA. Our results indicated that hAECs significantly inhibited the activation of naive T cells in a dose-dependent manner (p?<?0.0001–0.05). They significantly reduced the production of transforming growth factor-beta1 (TGF-β1) of stimulated CD4+T cells (p?<?0.0001–0.05). Moreover, hAECs had potent immunomodulatory effects on the production of interferon-gamma (IFN-γ) and interleukin-17A (IL-17A) of activated T cells (p?<?0.0001–0.01). These findings suggest that hAECs may be a suitable cell source to modulate abnormal immune responses in women with URSA. 相似文献
197.
Hui Zhang Zhenyu Chang Khalid Mehmood Rao Zahid Abbas Fazul Nabi Mujeeb Ur Rehman Xiaoxing Wu Xinxin Tian Xiaodan Yuan Zhaoyang Li Donghai Zhou 《Biological trace element research》2018,181(1):62-70
Nano-sized copper particles are widely used in various chemical, physical, and biological fields. However, earlier studies have shown that nano copper particles (40–100 μg/mL) can induce cell toxicity and apoptosis. Therefore, this study was conducted to investigate the role of nano copper in mitochondrion-mediated apoptosis in PK-15 cells. The cells were treated with different doses of nano copper (20, 40, 60, and 80 μg/mL) to determine the effects of apoptosis using acridine orange/ethidium bromide (AO/EB) fluorescence staining and a flow cytometry assay. The levels of malondialdehyde (MDA) and superoxide dismutase (SOD) in the PK-15 cells were examined using commercially available kits. Moreover, the mRNA levels of the Bax, Bid, Caspase-3, and CYCS genes were assessed by real-time PCR. The results revealed that nano copper exposure induced apoptosis and changed the mitochondrial membrane potential. In addition, nano copper significantly altered the levels of the Bax, Bid, Caspase-3, and CYCS genes at a concentration of 40 μg/mL. To summarize, nano copper significantly (P < 0.05) decreased the level of SOD and increased the level of MDA in PK-15 cells. Altogether, these results suggest that nano copper can play an important role in inducing the apoptotic pathway in PK-15 cells, which may be the mechanism by which nano copper induces nephrotoxicity. 相似文献
198.
Callus was produced on cotyledon, shoot tip, hypocotyl and root explants of twoCorchorus species on several media. Cytokinin was necessary for callus production on cotyledon explants. BothC.olitorius genotypes produced most callus on media with zeatin and either NAA or IAA, and theC.capsularis genotype produced most callus on media with IAA and either zeatin or BA. High frequencies of regenerated shoots were obtained
from shoot tip explants of both species, from the apical meristem and from callus. Media with 2.0 mg 1−1 BA were superior for both species, and media with zeatin were equally good forC.capsularis only. More regeneration was obtained for all genotypes after subculture of callus on media with 2.0 mg 1−1 zeatin. Cotyledon callus produced less regeneration, also with differences between genotypes; explants of both genotypes
ofC.olitorius produced regeneration on a medium with NAA and zeatin, and theC.capsularis genotype produced regeneration on a medium with IAA and BA. Limited regeneration from root explant callus was obtained forC.capsularis only on medium with BA and IAA. Regeneration was not obtained from hypocotyl callus. Further regeneration of shoots of both
species was obtained from secondary callus after subculture, and from nodal segments of regenerated shoots and of seedling
shoots cultured on basic MS medium without growth hormones. Roots were produced on about 80% of all shoots after transference
to medium with 0.2 mg 1−1 IBA, and rooted plantlets survived and flowered normally after transference to compost. 相似文献
199.
Myrothecium verrucaria was found to be an effective pathogen against kudzu grown in the greenhouse and the field. M. verrucaria produced large amounts of macrocyclic trichothecenes when cultured on solid rice medium, including epiroridin E (16.8 mg/g crude extract), epiisororidin E (1 mg/g), roridin E (8.7 mg/g), roridin H (31.3 mg/g), trichoverrin A (0.6 mg/g), trichoverrin B (0.1 mg/g), verrucarin A (37.4 mg/g), and verrucarin J (2.2 mg/g). Most of these toxins were also isolated from M. verrucaria spores and mycelia grown on potato dextrose agar medium, including epiroridin E (32.3 mg/g), epiisororidin E (28.6 mg/g), roridin E (0 mg/g), roridin H (60 mg/g), trichoverrin A (1.3 mg/g), trichoverrin B (1.8 mg/g), verrucarin A (13.8 mg/g), and verrucarin J (131 mg/g). When M. verrucaria was cultured on liquid media, the numbers but not the amounts of toxins decreased. Only epiroridin E (28.3 mg/g), epiisororidin E (29.6 mg/g), verrucarin B (195 mg/g) and verrucarin J (52.6 mg/g) were measured when the fungus was cultured on cornsteep medium. On soyflour-cornmeal broth M. verrucaria produced several toxins, including epiroridin E (58.1 mg/g), epiisororidin E (5.8 mg/g), verrucarin B (29.9 mg/g) and verrucarin J (32 mg/g). In contrast, no macrocyclic trichothecenes were detected by HPLC analysis of plant tissues of kudzu, sicklepod, and soybean treated with aqueous suspensions of M. verrucaria spores formulated with a surfactant. Chloroform-methanol extracts of kudzu leaves and stems treated with M. verrucaria spores were less cytotoxic to four cultured mammalian cell lines than the corresponding extracts from control plants. Purified macrocyclic trichothecenes (verrucarin A and T-2 toxin) were very cytotoxic to the same cell lines (< or = 2 ng/ml). These results show that neither intact macrocyclic trichothecenes nor toxic metabolites could be detected in plant tissues after treatment with M. verrucaria spores. These results argue for both safety and efficacy for the use of M. verrucaria in biological control of kudzu and other noxious weeds, and support proceeding to animal feeding trials for further evaluation of safety. 相似文献
200.
Bijan Keikhaei Pejman Slehi-fard Gholamreza Shariati Abbas Khosravi 《Biochemical genetics》2018,56(5):506-521
Alpha thalassemia is the most prevalent monogenic gene disorder in the world, especially in Mediterranean countries. In the current hematological phenotype of patients with different genotypes, the effects of missense mutations on the protein function and also stability were evaluated in a large cohort study. A total of 1,560 subjects were enrolled in the study and divided into two groups: 259 normal subjects; and 1301 alpha-thalassemia carriers. Genomic DNA was extracted and analyzed using ARMS PCR, Multiplex Gap, and direct sequencing. The effects of single nucleotide change on the protein function and stability were predicted by freely available databases of human polymorphisms. Sixty-three different genotypes were seen in the patients. The more prevalent was heterozygote form of ?α3.7 (41.4%) followed by ?α3.7 homozygote (11.6%) and ?MED (3.8%). The significant differences were seen in mean hemoglobin level [F?=?20.5, p?<?0.001] between the Alpha-globin genotypes, when adjusted for gender. Moreover, 28 different mutations were found in our study. A significant relationship was seen between ethnicity and the alpha-globin mutation frequency χ2 (df;8)?=?38.36, p?<?0.0001). Different genotypes could display as different phenotypes. The mutation frequency distributions in our region are different from those of other parts of Iran. Significant differences are seen in the spectrum of mutation frequency among various ethnicities. Finally, some missense mutations might not have considerable effect on the proteins, and they could be neutral mutations. 相似文献