全文获取类型
收费全文 | 1481篇 |
免费 | 97篇 |
国内免费 | 1篇 |
出版年
2024年 | 5篇 |
2023年 | 21篇 |
2022年 | 68篇 |
2021年 | 89篇 |
2020年 | 55篇 |
2019年 | 83篇 |
2018年 | 77篇 |
2017年 | 52篇 |
2016年 | 67篇 |
2015年 | 65篇 |
2014年 | 74篇 |
2013年 | 116篇 |
2012年 | 116篇 |
2011年 | 97篇 |
2010年 | 63篇 |
2009年 | 55篇 |
2008年 | 55篇 |
2007年 | 55篇 |
2006年 | 37篇 |
2005年 | 43篇 |
2004年 | 37篇 |
2003年 | 37篇 |
2002年 | 38篇 |
2001年 | 12篇 |
2000年 | 17篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1989年 | 5篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1978年 | 11篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1971年 | 4篇 |
1967年 | 4篇 |
1962年 | 2篇 |
排序方式: 共有1579条查询结果,搜索用时 234 毫秒
991.
992.
Dias EP Sayed Picciani BL de Carla Batista Santos V Oliveira Silva-Junior G Heffer Cantisano M Silva-Junior A 《Acta cytologica》2012,56(4):453-456
Oral lesions are common in human immunodeficiency virus (HIV)-infected patients, which may indicate impairment of the patient's general health status, and, in many cases, the oral lesions are the first sign of an HIV infection. Oral hairy leukoplakia (OHL) is a benign lesion of the oral mucosa related to Epstein-Barr virus (EBV) observed in HIV-positive individuals. The aim of this study was to report the contribution of oral cytopathology in the investigation of the HIV/AIDS status of patients as well as in the clinical and subclinical identification of OHL. Three patients were referred to the Oral Medicine Clinic in 2010. The patients were submitted to oral examination, and scrapes of the tongue were obtained. The Papanicolaou staining technique was used, and cytopathological analysis showed nuclear changes corresponding to cytopathic effects of EBV epithelial infection and candidiasis. The final diagnosis was OHL and candidiasis. Based on cytopathological diagnosis, an HIV serologic test was requested which revealed positive HIV serology. None of the patients was aware of their HIV serological status, and thus the cytopathology, by identifying OHL, contributed to the early diagnosis of HIV/AIDS. Cytopathology should be used as a routine procedure and it may be the method of choice for clinical and subclinical OHL diagnosis. 相似文献
993.
Chang F Lacey MR Bouljihad M Höner Zu Bentrup K Fortgang IS 《American journal of physiology. Gastrointestinal and liver physiology》2012,302(2):G195-G206
Tumor necrosis factor (TNF) is a key player in inflammatory bowel disease and has been variably associated with carcinogenesis, but details of the cross talk between inflammatory and tumorigenic pathways remain incompletely understood. It has been shown that, in C57BL/6 mice, signaling via TNF receptor 1 (TNFR1) is protective from injury and inflammation in experimental colitis. Therefore, we hypothesized that loss of TNFR1 signaling would confer increased risk of developing colitis-associated carcinoma. Using three models of murine tumorigenesis based on repeated bouts of inflammation or systemic tumor initiator, we sought to determine the roles of TNF and TNFR1 with regard to neoplastic transformation in the colon in wild-type (WT), TNFR1 knockout (R1KO), and TNF knockout (TNFKO) mice. We found R1KO animals to have more severe disease, as defined by weight loss, hematochezia, and histology. TNFKO mice demonstrated less weight loss but were consistently smaller, and rates and duration of hematochezia were comparable to WT mice. Histological inflammation scores were higher and neoplastic lesions occurred more frequently and earlier in R1KO mice. Apoptosis is not affected in R1KO mice although epithelial proliferation following injury is more ardent even before tumorigenesis is apparent. Lastly, there is earlier and more intense expression of activated β-catenin in these mice, implying a connection between TNFR1 and Wnt signaling. Taken together, these findings show that in the context of colitis-associated carcinogenesis TNFR1 functions as a tumor suppressor, exerting this effect not via apoptosis but by modulating activation of β-catenin and controlling epithelial proliferation. 相似文献
994.
Hydraulic fracturing is used to increase the permeability of shale gas formations and involves pumping large volumes of fluids into these formations. A portion of the frac fluid remains in the formation after the fracturing process is complete, which could potentially contribute to deleterious microbially induced processes in natural gas wells. Here, we report on the geochemical and microbiological properties of frac and flowback waters from two newly drilled natural gas wells in the Barnett Shale in North Central Texas. Most probable number studies showed that biocide treatments did not kill all the bacteria in the fracturing fluids. Pyrosequencing-based 16S rRNA diversity analyses indicated that the microbial communities in the flowback waters were less diverse and completely distinct from the communities in frac waters. These differences in frac and flowback water communities appeared to reflect changes in the geochemistry of fracturing fluids that occurred during the frac process. The flowback communities also appeared well adapted to survive biocide treatments and the anoxic conditions and high temperatures encountered in the Barnett Shale. 相似文献
995.
Elham Moasser Seyed Reza Kazemi-Nezhad Mostafa Saadat Negar Azarpira 《Molecular biology reports》2012,39(12):10187-10192
Diabetes Mellitus is characterized by chronic hyperglycemia and associated with an increased production of reactive oxygen species (ROS). Oxidative stress is the result of accumulation of free radicals in tissues which specially affects beta cells in pancreas. Glutathione S-transferases (GSTs) are a family of antioxidant enzymes that include several classes of GSTs. These enzymes have important roles in decreasing of ROS species and act as a kind of antioxidant defense. To investigate the association between GSTs polymorphism with type 2 diabetes mellitus (T2DM), we investigated the frequency of GSTM1, T1 and P1 genotypes in patients with T2DM and controls. The genotypes of GSTT1, M1 and P1 were determined in 171 clinically documented T2DM patients and 169 normal cases (as controls) by multiplex polymerase chain reaction and PCR–RFLP. In diabetic patients, the frequency of GSTM1-null genotype was significantly (OR?=?1.74; 95?% CI?=?1.13–2.69, P?=?0.016) higher than that in control. However, the frequency of GSTT1 (OR?=?1.29; 95?% CI?=?0.07–2.14, P?=?0.367) and GSTP1 (OR?=?0.83; 95?% CI?=?0.53–1.30, P?=?0.389) genotypes were not significantly different comparing both groups. Also, the frequency of both GSTT1-null and GSTM1-null genotypes in patients (19.88?%) was significantly higher compared to controls with the same genotypes (11.83?%, P?=?0.022). Our results indicated that GSTM1 and GSTT1 genotypes might be involved in the pathogenesis of T2DM in south Iranian population. 相似文献
996.
Genetic polymorphisms in genes encoding glutathione S-transferase T1 (GSTT1, a member of class theta) and M1 (GSTM1, a member of class mu) have been defined. Previous studies have revealed that there was significant difference between populations for allelic frequency of several members of GSTs. In order to find the prevalence of null genotypes of GSTM1 and GSTT1 in Afghanis populations the present study was carried out. The total study subjects consisted of 656 unrelated healthy Afghanis refugees living in Fars province (southern Iran). From these 257, 217, 120, and 62 individuals were Pashtuns, Tajiks, Hazaras, and Uzbeks, respectively. Genetic polymorphisms for GSTT1 and GSTM1 were detected by multiplex PCR. The prevalence of null genotype of GSTM1 in Pashtuns, Tajiks, Hazaras, and Uzbeks was 42.4, 48.4, 52.5, and 40.3 %, respectively. There was no significant difference between these populations for the genotypic distribution of the GSTM1 polymorphism (χ(2) = 4.67, df = 3, P = 0.197). The frequency of GSTT1 null genotype in Pashtuns, Tajiks, Hazaras, and Uzbeks was 7.4, 25.3, 25.0, and 29.0 %, respectively. The observed difference between populations for prevalence of GSTT1 null genotype was statistically significant (χ(2) = 35.54, df = 3, P < 0.001). In comparison with European and Asian populations, Afghanistan populations like Iranian populations showed intermediate frequency for GSTT1 and GSTM1 null genotypes. 相似文献
997.
Sayed Mohammad Masoumi Danial Kahrizi Hossein Rostami-Ahmadvandi Jahad Soorni Sara Kiani Ali Mostafaie Kheirollah Yari 《Molecular biology reports》2012,39(12):10361-10365
Cumin (Cuminum cyminum L.), Fennel (Foeniculum vulgare L.) and Longleaf (Falcaria vulgaris Bernh) that all belong to Apiaceae family as medicinal plants are very important in many countries. Study of genetic diversity for medicinal plant is important for researches in future. One of the methods to evaluate plant genetic diversity and classification of them is the electrophoresis of seed storage proteins. This research was conducted in order to evaluate seed protein variability in different Iranian Cumin, Fennel and Longleaf accessions and grouping them based on these proteins as a biochemical marker. For this purpose, the samples were first powdered in liquid nitrogen and seed protein was extracted with extraction buffer. Then total soluble proteins were resolved on 12.5?% sodium dodecyl sulphate polyacrylamide gel electrophoresis gels. The electrophoretic protein pattern showed 38 bands that were low polymorphism among the accessions. The result of cluster analysis showed that the accessions were classified in three groups (all 29 Cumin accessions in the first group, three Fennel ecotypes in second group and three Longleaf accessions in the last one). 相似文献
998.
We utilized Percoll density gradient centrifugation to isolate and fractionate chloroplasts of Korean winter wheat cultivar
cv. Kumgang (Triticum aestivum L.). The resulting protein fractions were separated by one dimensional polyacrylamide gel electrophoresis (1D-PAGE) coupled
with LTQ-FTICR mass spectrometry. This enabled us to detect and identify 767 unique proteins. Our findings represent the most
comprehensive exploration of a proteome to date. Based on annotation information from the UniProtKB/Swiss-Prot database and
our analyses via WoLF PSORT and PSORT, these proteins are localized in the chloroplast (607 proteins), chloroplast stroma
(145), thylakoid membrane (342), lumens (163), and integral membranes (166). In all, 67% were confirmed as chloroplast thylakoid
proteins. Although nearly complete protein coverage (89% proteins) has been accomplished for the key chloroplast pathways
in wheat, such as for photosynthesis, many other proteins are involved in regulating carbon metabolism. The identified proteins
were assigned to 103 functional categories according to a classification system developed by the iProClass database and provided through Protein Information Resources. Those functions include electron transport, energy,
cellular organization and biogenesis, transport, stress responses, and other metabolic processes. Whereas most of these proteins
are associated with known complexes and metabolic pathways, about 13% of the proteins have unknown functions. The chloroplast
proteome contains many proteins that are localized to the thylakoids but as yet have no known function. We propose that some
of these familiar proteins participate in the photosynthetic pathway. Thus, our new and comprehensive protein profile may
provide clues for better understanding that photosynthetic process in wheat. 相似文献
999.
Majida Charif Safaa Bounaceur Omar Abidi Halima Nahili Hassan Rouba Mostafa Kandil Redouane Boulouiz Abdelhamid Barakat 《Molecular biology reports》2012,39(12):11011-11016
Congenital hearing impairment (HI) affects one in 1,000 newborns and has a genetic cause in 50?% of the cases. Autosomal recessive non-syndromic hearing impairment is responsible for 70–80?% of all hereditary cases of HI. Recently, it has been demonstrated that, mutations of LRTOMT are associated with profound nonsyndromic hearing impairment at the DFNB63 locus. The objective of this study is to evaluate the carrier frequency of c.242G>A mutation in LRTOMT gene and define the contribution of this gene in the etiology of deafness in Moroccan population. We screened 105 unrelated Moroccan families with non-syndromic HI and 120 control individuals for mutation in the exon 8 of the LRTOMT gene, by sequencing and PCR-RFLP. The Homozygous c.242G>A mutation was found in 8.75?% of the families tested and in 4.16?% of control in the heterozygous state. Our results show that after the GJB2 gene mutation in LRTOMT gene is the second cause of congenital hearing impairment in Moroccan patients. This finding should facilitate diagnosis of congenital deafness of the affected subjects in Morocco. 相似文献
1000.
Akbarzadeh S Ghasemi S Kalantarhormozi M Nabipour I Abbasi F Aminfar A Jaffari SM Motamed N Movahed A Mirzaei M Rahbar AR 《Gynecological endocrinology : the official journal of the International Society of Gynecological Endocrinology》2012,28(7):521-524
Polycystic ovary syndrome (PCOS) is an endocrine disorder in women. Omentin-1 and vaspin are secretary adipokines that are produced by the visceral adipose tissue. These levels change in obese women with PCOS. The aim of this study is to investigate whether omentin and vaspin levels change in nonobese PCOS subjects. This study is a cross-sectional case control study in which 39 women with PCOS were picked out for this study. The inclusion criteria were based on the Rotterdam 2003 diagnostic criteria. The control group consisted of 39 women with normal pelvic sonographic reports having regular menstruation and showing no signs of infertility. The fasting plasma glucose (FPG), triglyceride (TG), Chol, and high-density lipoprotein cholesterol (HDL-C), insulin, testosterone, omentin and vaspin were measured by the enzymatic methods. The differences within these groups were calculated by the un-paired t-test and the Mann-Whitney test. The results from this study show a significant increase in the amount of insulin, testosterone, homeostasis model assessments for insulin resistance, TG and lower HDL in the patient group. No significant differences were seen in omentin, vaspin, FPG, Cho, low-density lipoprotein, very low-density lipoprotein cholesterol, blood urea nitrogen, Cr and homeostasis model assessments for B cell function levels between groups. Results show that PCOS is not a determinant of decreased omentin and vaspin plasma levels and those high androgen level and insulin resistances are warning signs of PCOS. 相似文献