全文获取类型
收费全文 | 1844篇 |
免费 | 87篇 |
专业分类
1931篇 |
出版年
2024年 | 6篇 |
2023年 | 21篇 |
2022年 | 40篇 |
2021年 | 66篇 |
2020年 | 52篇 |
2019年 | 54篇 |
2018年 | 50篇 |
2017年 | 61篇 |
2016年 | 78篇 |
2015年 | 82篇 |
2014年 | 103篇 |
2013年 | 129篇 |
2012年 | 139篇 |
2011年 | 150篇 |
2010年 | 94篇 |
2009年 | 72篇 |
2008年 | 101篇 |
2007年 | 106篇 |
2006年 | 91篇 |
2005年 | 79篇 |
2004年 | 72篇 |
2003年 | 55篇 |
2002年 | 50篇 |
2001年 | 18篇 |
2000年 | 17篇 |
1999年 | 18篇 |
1998年 | 14篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1977年 | 3篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 11篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1970年 | 5篇 |
排序方式: 共有1931条查询结果,搜索用时 15 毫秒
41.
42.
Alekseev KP Vlasova AN Jung K Hasoksuz M Zhang X Halpin R Wang S Ghedin E Spiro D Saif LJ 《Journal of virology》2008,82(24):12422-12431
We sequenced and analyzed the full-length genomes of four coronaviruses (CoVs), each from a distinct wild-ruminant species in Ohio: sambar deer (Cervus unicolor), a waterbuck (Kobus ellipsiprymnus), a sable antelope (Hippotragus niger), and a white-tailed deer (Odocoileus virginianus). The fecal samples from the sambar deer, the waterbuck, and the white-tailed deer were collected during winter dysentery outbreaks and sporadic diarrhea cases in 1993 and 1994 (H. Tsunemitsu, Z. R. el-Kanawati, D. R. Smith, H. H. Reed, and L. J. Saif, J. Clin. Microbiol. 33:3264-3269, 1995). A fecal sample from a sable antelope was collected in 2003 from an Ohio wild-animal habitat during the same outbreak when a bovine-like CoV from a giraffe (GiCoV) was isolated (M. Hasoksuz, K. Alekseev, A. Vlasova, X. Zhang, D. Spiro, R. Halpin, S. Wang, E. Ghedin, and L. J. Saif, J. Virol. 81:4981-4990, 2007). For two of the CoVs (sambar deer and waterbuck), complete genomes from both the cell culture-adapted and gnotobiotic-calf-passaged strains were also sequenced and analyzed. Phylogenetically, wild-ruminant CoVs belong to group 2a CoVs, with the closest relatedness to recent bovine CoV (BCoV) strains. High nucleotide identities (99.4 to 99.6%) among the wild-ruminant strains and recent BCoV strains (BCoV-LUN and BCoV-ENT, isolated in 1998) further confirm the close relatedness. Comparative genetic analysis of CoVs of captive wild ruminants with BCoV strains suggests that no specific genomic markers are present that allow discrimination between the bovine strains and bovine-like CoVs from captive wild ruminants; furthermore, no specific genetic markers were identified that defined cell cultured or calf-passaged strains or the host origin of strains. The results of this study confirm prior reports of biologic and antigenic similarities between bovine and wild-ruminant CoVs and suggest that cattle may be reservoirs for CoVs that infect captive wild ruminants or vice versa and that these CoVs may represent host range variants of an ancestral CoV. 相似文献
43.
Mustafa Çelik Fatma Ünal Deniz Yüzbaşıoğlu Serkan Yılmaz Hüseyin Aksoy Şengül Karaman 《Cytotechnology》2006,51(2):99-104
In this investigation, clastogenic effects of Thymus kotschyanus var. glabrescens Boiss. extract (TE) and anticlastogenic effects of this extract against Mitomycin C (MMC) induced chromosome damage have been evaluated in human peripheral blood lymphocytes in vitro. Two series of experiments were conducted. In the first, only 10−5, 10−4, 10−3 and 10−2 μl ml−1 concentrations of TE were used for 48 h to detect potential clastogenicity. In the second, MMC (0.38 μg ml−1) plus 10−5, 10−4, 10−3 and 10−2 μl ml−1 concentrations of TE were used for 48 h to determine anticlastogenic effects. TE did not increase sister chromatid exchanges (SCEs) (except 10−2 μl ml concentration) and chromosome aberrations (CAs) significantly compared with negative and solvent controls. However, it decreased the frequency of MMC induced chromosome aberrations. Decreasing was significant at 10−4, 10−3 and 10−2 μl ml−1 concentrations. On the other hand, TE significantly increased MMC-induced SCEs for all treatment groups compared with positive control. 相似文献
44.
Huu Hieu Ho Rudy Swennen Valérie Cappuyns Elvira Vassilieva Gerda Neyens Mustafa Rajabali 《Soil & Sediment Contamination》2013,22(4):415-432
The Cam River mouth (Haiphong Province) is one of the main river mouths of the Red River System, which is one of the most important water resources in Northern Vietnam. Over the past 50 years, the strong socio-economic development in the area has caused a considerable contamination with heavy metals (Co, Cr, Cu, Mn, Ni, Pb, and Zn) and arsenic. In this study, the vertical and horizontal distributions of heavy metals and arsenic in sediments from the Cam River mouth were investigated. In addition, the history, origin, and degree of contamination were assessed. Normalized (with respect to Al) heavy metal and arsenic concentrations in sediment cores and absolute dates obtained from the 137Cs analysis were used to reconstruct the pollution history of the river mouth. As, Cu, Mn, Pb, and Zn concentrations increase rapidly by approximately two times or more from 1954 to 1975, and then remain nearly unchanged from 1975 until 2008, whereas Co, Cr, and Ni concentrations slightly increase from 1954 until 2008. In addition, background values for heavy metals and arsenic have also been determined with regard to the period before 1954. In the study area, Co, Cr, Cu, Ni, Mn, and Zn are evaluated as minorly enriched, whereas As and Pb are classified as moderately enriched. Generally, the anthropogenic activities in the Haiphong harbor and industrial zone locally contribute to the contamination by heavy metals and arsenic in the Cam River mouth. 相似文献
45.
46.
Asha S. Multani Mustafa Ozen Alpana Agrawal Vicki L. Hopwood Andrew C. Von Eschenbach Sen Pathak 《In vitro cellular & developmental biology. Animal》1999,35(4):236-239
Summary Conventional and molecular cytogenetic analyses of three murine cancer cell lines that had been induced in male athymic mice
by the injection of three different human prostate cancer cell lines revealed selective amplification of the Y chromosome.
In particular, analysis of metaphase and interphase nuclei by fluorescence in situ hybridization (FISH) with the mouse Y chromosome-specific
DNA painting probe revealed the presence of various numbers of Y chromosomes, ranging from one to eight, with a large majority
of nuclei showing two copies (46.5–60.1%). In Interphase nuclei, the Y chromosomes showed distinct morphology, allowing identification
irrespective of whether the preparations were treated for 15 min or for 5 h with Colcemid, a chemical known to cause chromosome
condensation. However, FISH performed on human lymphocyte cultures with chromosome-specific DNA painting probes other than
the Y chromosome did not reveal condensed chromosome morphology in interphase nuclei even after 12 h of Colcemid treatment.
Our FISH results indicate that (1) the Y chromosome is selectively amplified in all three cell lines; (2) the mouse Y chromosome
number is comparable in both interphase and metaphase cells; (3) the Y chromosome number varies between one and eight, with
a large majority of cells showing two or three copies in most interphase nuclei; (4) the condensation of the Y chromosome
is not affected by the duration of Colcemid treatment but by its inherent DNA constitution; and (5) the number of copies of
the Y chromosome is increased and retained not only in human prostate tumor cell lines but also in murine tumors induced by
these prostate tumor cell lines. 相似文献
47.
The membrane-bound quinoprotein glucose dehydrogenase (mGDH) in Escherichia coli contains pyrroloquinoline quinone (PQQ) and participates in the direct oxidation of D-glucose to D-gluconate by transferring electrons to ubiquinone (UQ). To elucidate the mechanism of ubiquinone reduction by mGDH, we applied a pulse radiolysis technique to mGDH with or without bound UQ8. With the UQ8-bound enzyme, a hydrated electron reacted with mGDH to form a transient species with an absorption maximum at 420 nm, characteristic of formation of a neutral ubisemiquinone radical. Subsequently, the decay of the absorbance at 420 nm was accompanied by an increase in the absorbance at 370 nm. Experiments with the PQQ-free apoenzyme showed no such subsequent absorption changes, although ubisemiquinone was formed. These results indicate that a pathway for an intramolecular electron transfer from ubisemiquinone radical at the UQ8 binding site to PQQ exists in mGDH. The first-order rate constant of this process was calculated to be equal to 1.2 x 10(3) s(-1). These findings are consistent with our proposal that during the catalytic cycle of mGDH the bound UQ8 mediates electron transfer from the reduced PQQ to UQ8 pools. 相似文献
48.
LGBT+ Individuals’ Perceptions of Healthcare Services in Turkey: A Cross-sectional Qualitative Study
Şükrü Keleş Mustafa Volkan Kavas Neyyire Yasemin Yalım 《Journal of bioethical inquiry》2018,15(4):497-509
When accessing healthcare services, LGBT+ individuals are often exposed to segregating and marginalizing discourses. Knowledge about how such experiences are reflected in the moral world of LGBT+ individuals living in Turkey is limited. This study examined LGBT+ individuals’ lived experiences when utilizing healthcare services. The findings are discussed in terms of moral discourses related to LGBT+ individuals’ gender identity and sexual orientation. A qualitative field study was conducted using semi-structured interviews with fifty-five LGBT+ individuals from Turkish cities who were in contact with various non-governmental organizations that conduct studies on gender identity and sexual orientation. A questionnaire was administered with items on participants’ demographic information, experiences, behavioural patterns, and knowledge regarding healthcare services. The data were analysed thematically. The findings were evaluated within the framework of “access to healthcare service” theme related to “healthcare service demand” context. Additionally, the “interaction with physicians” theme was addressed in the context of “physician–patient/counselee relationship.” LGBT+ individuals state that they are exposed to stigmatizing and segregating discourses by healthcare professionals, which might pose an obstacle for adaptive health-seeking behaviours. These results suggest that physicians’ professional approach has a considerable influence on LGBT+ individuals’ capacity for utilizing healthcare services. 相似文献
49.
Nazıroğlu M 《The Journal of membrane biology》2011,241(2):51-57
Melastatin-like transient receptor potential 2 (TRPM2) channel activation/inhibition mechanisms in response to ADP-ribose
(ADPR), oxidative stress, flufenamic acid (FFA) and 2-aminoethoxydiphenyl borate (2-APB) are not clear. We tested the effects
of FFA and 2-APB on ADPR-induced TRPM2 cation channel currents in rat native bone marrow megakaryocytes. Megakaryocyte cells
were freshly isolated from rat bone marrow and studied with the conventional whole-cell patch-clamp technique. Extracellular
H2O2, FFA and 2-APB were added through the patch chamber, while intracellular ADPR was applied through the pipette. Nonselective
cation currents were consistently induced by ADPR but not H2O2. Current density of ADPR in the cells was significantly (P < 0.001) higher than in control. The time courses of ADPR effects in the megakaryocytes were characterized by a delay of
2.24 ± 0.73. The ADPR-induced Ca2+ gate was not blocked by either the IP3 receptor inhibitor 2-APB or the PLC inhibitor FFA. In conclusion, TRPM2 channels were constitutively activated by intracellular
ADPR, although the channel currents in rat native megakaryocytes were not affected by extracellular H2O2, 2-APB or FFA. Activation of TRPM2 channels in megakaryocytes seems to be intracellular and ADPR-dependent. 相似文献
50.
Yavuz N Unal E Dogan M Kiziler AR Aydemir B Titiz I 《Biological trace element research》2005,106(3):205-209
Serum free prostate-specific antigen (fPSA) is the most useful tumor marker for prostatic cancer screening. However, recently,
fPSA has also been detected in sera from patients with pancreatic diseases. In addition, it has been shown that zinc (Zn)
concentration might change in both serum and tissues in pancreatic disease. In the present study, we measured serum concentrations
of fPSA and Zn as possible markers and prognostic factors in an experimental acute-pancreatitis model. Twenty-five female
Wistar albino rats were divided into two groups: the control group (n=10) and the experimental group (n=15). Acute pancreatitis was induced by injection of ethyl alcohol into the common biliary duct. The animals were sacrificed
24 h later to detect the concentrations of serum fPSA and Zn. fPSA values were detected to be significantly higher in the
experimental group p<0.001). There was also a significant decrease in the serum Zn level of the acute-pancreatitis group (p<0.001). In conclusion, these findings suggested that a combination of these parameters might represent a significant improvement
on the diagnostic value of each of them separately and provide a powerful tool for differential diagnosis and prognosis in
pancreatic diseases. 相似文献