全文获取类型
收费全文 | 2052篇 |
免费 | 88篇 |
国内免费 | 6篇 |
出版年
2024年 | 4篇 |
2023年 | 22篇 |
2022年 | 44篇 |
2021年 | 77篇 |
2020年 | 55篇 |
2019年 | 69篇 |
2018年 | 65篇 |
2017年 | 68篇 |
2016年 | 82篇 |
2015年 | 96篇 |
2014年 | 108篇 |
2013年 | 146篇 |
2012年 | 155篇 |
2011年 | 172篇 |
2010年 | 101篇 |
2009年 | 87篇 |
2008年 | 117篇 |
2007年 | 114篇 |
2006年 | 102篇 |
2005年 | 89篇 |
2004年 | 79篇 |
2003年 | 53篇 |
2002年 | 49篇 |
2001年 | 19篇 |
2000年 | 17篇 |
1999年 | 19篇 |
1998年 | 14篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1977年 | 3篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 12篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1970年 | 5篇 |
排序方式: 共有2146条查询结果,搜索用时 31 毫秒
991.
Twenty Salmonella Infantis strains resistant against kanamycin, tetracycline, neomycin, spectinomycin, sulphonamide, nalidixic acid and trimethoprim
were selected for this study out of 103 Salmonella strains isolated from broiler samples collected from several markets in the Bolu and Ankara regions of Turkey. The resistance
genes aadA1, aphA1, sul1, tet(A), dfrA5/dfrA14 and gyrA were determined for these multidrug-resistant S. Infantis strains. S. Infantis strains contained a mega plasmid with the molecular size of 206 kb. The strains were divided
into three groups according to the pulsed field gel electrophoresis patterns of XbaI digested chromosomal DNA. A Ser83→Tyr83 point mutation was found in the gyrA gene of all quinolone-resistant isolates. Filter mating experiments showed that 206 kb plasmid transferred nalidixic acid
resistance associated with class I integrons. 相似文献
992.
Phylogeography and evolutionary history of reassortant H9N2 viruses with potential human health implications 总被引:2,自引:0,他引:2
Fusaro A Monne I Salviato A Valastro V Schivo A Amarin NM Gonzalez C Ismail MM Al-Ankari AR Al-Blowi MH Khan OA Maken Ali AS Hedayati A Garcia Garcia J Ziay GM Shoushtari A Al Qahtani KN Capua I Holmes EC Cattoli G 《Journal of virology》2011,85(16):8413-8421
Avian influenza viruses of the H9N2 subtype have seriously affected the poultry industry of the Far and Middle East since the mid-1990s and are considered one of the most likely candidates to cause a new influenza pandemic in humans. To understand the genesis and epidemiology of these viruses, we investigated the spatial and evolutionary dynamics of complete genome sequences of H9N2 viruses circulating in nine Middle Eastern and Central Asian countries from 1998 to 2010. We identified four distinct and cocirculating groups (A, B, C, and D), each of which has undergone widespread inter- and intrasubtype reassortments, leading to the generation of viruses with unknown biological properties. Our analysis also suggested that eastern Asia served as the major source for H9N2 gene segments in the Middle East and Central Asia and that in this geographic region within-country evolution played a more important role in shaping viral genetic diversity than migration between countries. The genetic variability identified among the H9N2 viruses was associated with specific amino acid substitutions that are believed to result in increased transmissibility in mammals, as well as resistance to antiviral drugs. Our study highlights the need to constantly monitor the evolution of H9N2 viruses in poultry to better understand the potential risk to human health posed by these viruses. 相似文献
993.
Baig JA Kazi TG Shah AQ Afridi HI Khan S Kolachi NF Kandhro GA Wadhwa SK Shah F 《Biological trace element research》2011,143(2):772-786
The arsenic (As) hazardous quotient was estimated based on concentration of As in drinking water and scalp hair of male subjects
of two age groups (n = 360) consuming As contaminated water at different levels and non-contaminated drinking water. The total As concentrations
in drinking water of less-exposed (LE) and high-exposed (HE) areas was found to be 3- to 30-fold higher than the permissible
limit of the World Health Organization (2004) for drinking water, while the levels of As in drinking water of non-exposed
(NE) areas was within the permissible limit. The levels of As in scalp hair samples of male subjects of two age groups belonging
to NE, LE, and HE areas ranged from 0.01 to 0.27, 0.11–1.31, and 0.36–6.80 μg/g, respectively. A significant correlation between
As contents of drinking water and As concentration in scalp hair was observed in sub-district Gambit (r = 0.825–0.852, p < 0.001) as compared to those subjects belonging to LE sub-district Thari Mirwah. A toxicity risk assessment provides a hazard
quotient corresponding to <10 that indicates non-carcinogenic exposure risk of understudy areas. 相似文献
994.
Ayoub A. Mohamed Abdel Aziem A. Ali Naji I. Ali Elshafaee H. Abusalama Mustafa I. Elbashir Ishag Adam 《Biological trace element research》2011,140(3):284-290
The study was conducted to investigate determinants (clinical, nutritional, and nonnutritional factors) of anemia among pregnant
women in Kassala, eastern Sudan. Sociodemographic characteristics were gathered; serum ferritin, zinc, albumin, and C-reactive
protein were measured using different laboratory methods in a cross-sectional study of 250 pregnant women. Of the 250 women,
58.4% had anemia (hemoglobin (HB) <11 g/dl), 6.8% had severe anemia (HB < 7 g/dl), 19.6% had iron deficiency (S-ferritin <15 μg/l),
14.8% had iron deficiency anemia (<11 g/dl and S-ferritin <15 μg/l), and 38% had zinc deficiency (<80 μg/ml). S-albumin, zinc,
and ferritin were significantly lower in patients with severe anemia. While age, gestational age, ferritin, and C-reactive
protein were not predictors for anemia, primigravidae (OR = 2.7, 95% CI = 1.1–6.7, P = 0.02), low S-albumin (OR = 5.9, 95% CI = 1.4–25.2, P = 0.01), and low S-zinc (OR = 2.6, 95% CI = 1.0–6.6, P = 0.03) were the predictors for anemia. While there was no significant correlation between hemoglobin, S-zinc, and S-ferritin,
there was a significant positive correlation between hemoglobin and S-albumin (r = 0.308, P = 0.001) and significant inverse correlation between hemoglobin and C-reactive protein (r = 0.169, P = 0.007). Thus, the role of chronic inflammation and zinc as possible contributing factors to anemia in pregnancy has important
implications for the clinical evaluation and treatment of these women. 相似文献
995.
Hassan Imran Afridi Tasneem Gul Kazi Naveed Kazi Ghulam Abbas Kandhro Jameel Ahmed Baig Abdul Qadir Shah Sumaira Khan Nida Fatima Kolachi Sham Kumar Wadhwa Faheem Shah Mohammad Khan Jamali Mohammad Balal Arain 《Biological trace element research》2011,142(3):284-301
Psoriasis is a noncontiguous common and chronic skin disorder. The aim of the present study was to compare the level of trace elements cadmium (Cd), chromium (Cr), Nickel (Ni), and zinc (Zn) in biological samples (whole blood, urine, and scalp hair) of psoriasis patients of both gender age ranged (25–55 years) at mild, moderate severe, and more severe stage (n?=?418) living in the vicinity of cement factory. For comparison purposes, healthy age-matched referent subjects, residents of industrial and non-industrial area, of both gender were also selected (n?=?241). The concentrations of trace and toxic elements were measured by atomic absorption spectrophotometer prior to microwave-assisted acid digestion. The validity and accuracy of methodology was checked by using certified reference materials (CRMs) and conventional wet acid digestion method on same CRMs and real samples. The results of this study showed that the mean values of Cd, Cr, Ni, and Pb were significantly higher in scalp hair, blood, and urine samples of mild and severe psoriasis patients as compared to referents (p?<?0.001), while the concentration of Zn was lower in the scalp hair and blood, but higher in the urine samples of psoriasis patients. The deficiency of Zn in psoriasis patients may be undoubtedly caused by the toxic element exposures via cement factory. 相似文献
996.
Hassan Imran Afridi Tasneem Gul Kazi Naveed Kazi Sirajuddin Ghulam Abbas Kandhro Jameel Ahmed Baig Abdul Qadir Shah Sham Kumar Wadhwa Sumaira Khan Nida Fatima Kolachi Faheem Shah Mohammad Khan Jamali Mohammad Balal Arain 《Biological trace element research》2011,142(3):350-361
The causes of night blindness in children are multifactorial, and particular consideration has been given to childhood trace metals toxicity, which is the most common problem found in underdeveloped countries. This study was designed to compare the levels of cadmium (Cd), lead (Pb), and nickel (Ni) in scalp hair, blood, and urine of night blindness children age ranged 3–7 and 8–12 years of both genders, comparing them to sex- and age-matched controls. A microwave-assisted wet acid digestion procedure was developed as a sample pretreatment, for the determination of Cd, Pb, and Ni in biological samples of night blindness children. The proposed method was validated by using conventional wet digestion and certified reference samples of hair, blood, and urine. The digests of all biological samples were analyzed for Cd, Pb, and Ni by electrothermal atomic absorption spectrometry. The results indicated significantly higher levels of Cd, Pb, and Ni in the biological samples (blood, scalp hair, and urine) of male and female night blindness children, compared with control subjects of both genders. These data present guidance to clinicians and other professional investigating toxicity of trace metals in biological samples of night blindness children. 相似文献
997.
Hassan Imran Afridi Tasneem Gul Kazi Naveed Kazi Ghulam Abbas Kandhro Jameel Ahmed Baig Abdul Qadir Shah Sham Kumar Wadhwa Sumaira Khan Nida Fatima Kolachi Faheem Shah Mohammad Khan Jamali Mohammad Balal Arain Sirajuddin 《Biological trace element research》2011,142(3):323-334
The causes of night blindness in children are multifactorial, and particular consideration has been given to childhood nutritional deficiency, which is the most common problem found in underdeveloped countries. Such deficiency can result in physiological and pathological processes that in turn influence hair composition. This study was designed to compare the levels of zinc (Zn), copper (Cu), and iron (Fe) in scalp hair, blood, and urine of both genders of children with night blindness with age range of 3–7 and 8–12 years, comparing them to sex- and age-matched controls. A microwave-assisted wet acid digestion procedure was developed as a sample pretreatment, for the determination of zinc, copper, and iron in biological samples of children with night blindness. The proposed method was validated by using conventional wet digestion and certified reference samples of hair, blood, and urine. The digests of all biological samples were analyzed for Cu, Fe, and Zn by flame atomic absorption spectrometry using an air/acetylene flame. The results indicated significantly lower levels of Fe, Cu, and Zn in the biological samples (blood and scalp hair) of male and female children with night blindness, compared with control subjects of both genders. These data present guidance to clinicians and other professionals investigating the deficiency of essential trace metals in biological samples (scalp hair and blood) of children with night blindness. 相似文献
998.
Korkmaz S Erturan I Nazıroğlu M Uğuz AC Ciğ B Övey IS 《The Journal of membrane biology》2011,244(3):113-120
Behçet disease (BD) is a chronic, inflammatory, and multisystemic condition with an uncertain pathogenesis. One of the major immunologic findings in BD pathogenesis is increase in activity of neutrophil. An increase in the cytosolic free Ca2+ [Ca2+]i concentration that induces Ca2+ signaling is an important step that participates in the neutrophil activation and reactive oxygen species production that leads to tissue damage in body cells. We aimed to investigate the effects of colchicine on oxidative stress and Ca2+ release in serum and neutrophil of BD patients with active and inactive periods. Twelve Behçet patients (6 active and 6 inactive) and 6 control subject were included in the study. Disease activity was considered by clinical findings. Serum and neutrophil samples were obtained from the patients and control subjects. Neutrophils from patients with active BD were divided into three subgroups and were incubated with colchicine, verapamil + diltiazem, and colchicine + verapamil + diltiazem, respectively. Erythrocyte sedimentation rate, leucocytes counts, serum C-reactive protein, neutrophil, and serum lipid peroxidation and intracellular Ca2+ release levels were higher in active and inactive groups than in the control group, although their levels were lower in active group than in inactive group. However, neutrophil Ca2+ release levels were decreased in colchicine, verapamil + diltiazem, and colchicine + verapamil + diltiazem groups group compared to active group. Serum glutathione, vitamin A, vitamin E, and β-carotene concentrations were lower in active and inactive groups than in the control group, although serum vitamin E and β-carotene concentrations were higher in the inactive group than in the active group. Neutrophil and serum glutathione peroxidase activity within the three groups did not change. In conclusion, we observed the importance of Ca2+ influx into the neutrophils and oxidative stress in the pathogenesis and activation of the patients with BD. Colchicine induced protective effects on oxidative stress by modulating Ca2+ influx in BD patients. 相似文献
999.
We investigated the effects of colchicine on oxidative stress and Ca2+ release in serum and polymorphonuclear leucocytes (PMNs) of Familial Mediterranean Fever (FMF) patients with attack, remission
and unremission periods. Eighteen FMF patients and six age-matched healthy subjects in four groups were used. The first group
was a control. The second group included patients with active FMF. The third and fourth groups were patients with remission
and unremission, respectively. Colchicine (1.5 mg/day) was given to the third and fourth groups for 1 month. PMN cells, serum
lipid peroxidation and intracellular Ca2+-release levels in the attack and unremission groups were higher than in those in controls, although they were lower in the
remission group than in the attack group. Serum vitamin E and β-carotene concentrations were higher in the remission group
than in the control and attack groups. However, PMN, serum lipid peroxidation and Ca2+-release levels were further increased in the unremission group compared to the attack group. Glutathione peroxidase, reduced
glutathione and vitamin A values in the four groups did not change by FMF and colchicine. In conclusion, we observed that
colchicine induced protective effects on oxidative stress by modulating vitamin E, β-carotene and Ca2+-release levels in FMF patients with a remission period. 相似文献
1000.
Shakhmaeva II Bulatov ER Bondar OV Saifullina DV Culha M Rizvanov AA Abdullin TI 《Journal of biotechnology》2011,152(3):102-107
We propose a new method for the separation of nucleic acids using multi-layered carbon nanotubes (CNTs) as an adsorbent. According to agarose gel electrophoresis, oxidized water-stable CNTs adsorb certain forms of nucleic acids, such as high molecular weight RNA, chromosomal DNA, linear and denatured forms of plasmid DNA. However, CNTs do not adsorb supercoiled form of plasmid DNA. Nucleic acids bound to CNTs can be readily removed by centrifugation whereas supercoiled plasmid DNA remains in solution. Upon the addition of divalent metal ions supercoiled plasmid DNA forms relatively stable complexes with CNTs due to chelation. Thus, new details about association of nucleic acids with CNTs were revealed and stoichiometry of the complexes was estimated. Our results can be used for fine purification of supercoiled plasmid DNA for gene therapy applications as well as manipulation of nucleic acids for biosensor design. 相似文献