首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1218篇
  免费   69篇
  国内免费   4篇
耳鼻咽喉   5篇
儿科学   24篇
妇产科学   20篇
基础医学   151篇
口腔科学   22篇
临床医学   96篇
内科学   238篇
皮肤病学   26篇
神经病学   92篇
特种医学   20篇
外科学   162篇
综合类   16篇
预防医学   91篇
眼科学   137篇
药学   108篇
中国医学   15篇
肿瘤学   68篇
  2023年   6篇
  2022年   29篇
  2021年   41篇
  2020年   21篇
  2019年   44篇
  2018年   41篇
  2017年   36篇
  2016年   55篇
  2015年   41篇
  2014年   62篇
  2013年   71篇
  2012年   91篇
  2011年   114篇
  2010年   48篇
  2009年   47篇
  2008年   81篇
  2007年   88篇
  2006年   56篇
  2005年   64篇
  2004年   55篇
  2003年   54篇
  2002年   44篇
  2001年   16篇
  2000年   12篇
  1999年   13篇
  1998年   2篇
  1997年   4篇
  1996年   2篇
  1995年   2篇
  1994年   4篇
  1993年   6篇
  1992年   6篇
  1991年   10篇
  1990年   1篇
  1989年   2篇
  1988年   3篇
  1987年   1篇
  1986年   1篇
  1982年   2篇
  1981年   1篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
  1977年   2篇
  1976年   2篇
  1975年   2篇
  1974年   2篇
  1973年   1篇
  1972年   1篇
排序方式: 共有1291条查询结果,搜索用时 15 毫秒
1.
2.
Odds ratio was used to evaluate relationship between sepsis in cattle less than 1 year old and mastitis in cows and erythrocyte glutathione peroxides (GSH-PX) activity as an indicator of selenium status. Data were from 178 blood samples collected from referred cases to Urmia University, Veterinary Teaching Hospital. Low activity of GSH-PX was significantly associated with higher odds of developing sepsis (P=0.005) in young cattle and mastitis (P=0.044) in adult cows. The odds ratios for the low activity of GSH-PX on incidence of sepsis and mastitis were 4.74 and 3.95, respectively. Selenium deficiency was associated with sepsis in young cattle and mastitis in cows, i.e., cattle with low activity of erythrocyte GSH-PX were at increased risk of sepsis and mastitis.  相似文献   
3.
Missense mutations of the human skeletal muscle voltage-gated Na+ channel (hSkM1) cause a variety of neuromuscular disorders. The mutation R1448H results in paramyotonia congenita and causes cold-induced myotonia with subsequent paralysis. The mutation M1360V causes an overlapping syndrome with both K+-induced muscle weakness and cold-induced myotonia. The molecular mechanisms of the temperature dependence of these disorders are not well understood. Therefore we investigated physiological parameters of these Na+ channel mutations at different temperatures. Channel proteins were recombinantly expressed in human embryonic kidney cells and studied electrophysiologically, using the whole-cell patch-clamp technique. We compared the wild-type (WT) channel with both mutants at different temperatures. Both mutations had slower inactivation and faster recovery from inactivation compared to WT channels. This effect was more pronounced at the R1448H mutation, leading to a larger depolarization of the cell membrane causing myotonia and paralysis. The voltage dependence of activation of R1448H was shifted to more negative membrane potentials at lower temperature but not at the M1360V mutation or in the WT. The window current by mutation R1448H was increased at lower temperatures. The results of this study may explain the stronger cold-induced clinical symptoms resulting from the R1448H mutation in contrast to the M1360V mutation.  相似文献   
4.
Genetics of the central MHC   总被引:4,自引:0,他引:4  
The MHC, primarily known for its antigen-presenting class I and II molecules, harbours, within a central segment of less than 1 Mb, a dense collection of genes involved in various biological functions. Although MHC I and MHC II are principal players of adaptive immunity, several loci within this central (still called class III) MHC region encode members of the innate immune system. These include the long known factors of the complement system--potentially inhibitory and triggering natural killer receptors as well as stress proteins. Whether this physical proximity is fortuitous or functionally advantageous is an important question for the future of MHC genetics.  相似文献   
5.
Mitochondrial DNA and Y-Chromosome Variation in the Caucasus   总被引:7,自引:3,他引:7  
We have analyzed mtDNA HVI sequences and Y chromosome haplogroups based on 11 binary markers in 371 individuals, from 11 populations in the Caucasus and the neighbouring countries of Turkey and Iran. Y chromosome haplogroup diversity in the Caucasus was almost as high as in Central Asia and the Near East, and significantly higher than in Europe. More than 27% of the variance in Y‐haplogroups can be attributed to differences between populations, whereas mtDNA showed much lower heterogeneity between populations (less then 5%), suggesting a strong influence of patrilocal social structure. Several groups from the highland region of the Caucasus exhibited low diversity and high differentiation for either or both genetic systems, reflecting enhanced genetic drift in these small, isolated populations. Overall, the Caucasus groups showed greater similarity with West Asian than with European groups for both genetic systems, although this similarity was much more pronounced for the Y chromosome than for mtDNA, suggesting that male‐mediated migrations from West Asia have influenced the genetic structure of Caucasus populations.  相似文献   
6.
Induction of oxidative stress during the sperm preparation process for assisted reproductive techniques (ART) in men can weaken sperm parameters. Vitamin E (VE) is considered a factor in boosting male fertility. This experimental study (in vitro) aimed to assess the impact of VE supplementation on sperm quality and lipid peroxidation during sperm sampling at different times. For this mention, semen samples were collected from 50 asthenoteratozoospermic men. Samples were divided into control and test groups for 2, 4 and 6 hr that the test group was incubated with VE (2 mM). In two groups, total motility, progressive motility and viability based on the WHO 2010 criteria were assessed. Moreover, malondialdehyde (MDA) levels were evaluated in each group. In the control group, total and progressive motility and sperm viability were decreased significantly after 2 hr; however, MDA levels were increased significantly after 6 hr. Also, in the test group, sperm parameters were increased significantly after 2 hr, and MDA levels were decreased significantly after 6 hr compared to the control group. In outcome, in vitro VE supplementation may protect spermatozoa from the adverse effect of oxidative stress during sperm preparation via preservation antioxidant processes in normal condition.  相似文献   
7.
Intraductal carcinoma (IDC) is a rare salivary gland tumor that is considered analogous to ductal carcinoma in-situ of the breast, demonstrating a complex neoplastic epithelial proliferation surrounded by a continuous layer of presumed non-neoplastic myoepithelial cells. It is subcategorized into intercalated duct, apocrine, and hybrid subtypes based on morphologic and immunohistochemical features, with frequent NCOA4-RET and TRIM27-RET fusions, respectively, seen in intercalated duct and hybrid tumors. However, as an expanding clinicopathologic spectrum of IDC has been documented, controversy has emerged as to whether this tumor type is best defined by its intraductal growth pattern or distinctive molecular and immunophenotypic differentiation. Here, we further explore the nature of IDC by evaluating four cases that arose within intraparotid lymph nodes. These intercalated-duct phenotype tumors with diffuse S100 protein expression demonstrated a crowded and complex epithelial proliferation arranged in cystic, cribriform, and micropapillary architecture, surrounded by an intact myoepithelial cell layer, and were completely intranodal. Of two tumors with tissue available for molecular analysis, one demonstrated a NCOA4-RET fusion and one harbored a STRN-ALK fusion that is novel to IDC. Not only does the intranodal presence of IDC present a challenging differential diagnosis, but the complex nature of this proliferation within lymph node tissue raises questions as to whether the myoepithelial component of IDC is actually non-neoplastic in nature. Furthermore, identification of a STRN-ALK fusion expands the genetic spectrum of IDC and adds to evidence of an emerging role for ALK in salivary gland tumors. Further attention to the nature of the myoepithelial cells and documentation of alternate fusion events in IDC may inform continued discussion about its appropriate classification.  相似文献   
8.
Anti-oxidant effect of flavonoids on hemoglobin glycosylation   总被引:7,自引:0,他引:7  
A high glucose concentration has been found to lead to the glycosylation of amino groups of lysine residue in proteins. The addition of reducing agent not only prevents this reaction but also reverses it. On the other hand, flavonoids which found in plant sources have antioxidant properties. Since the glycosylation of protein is an oxidation reaction, therefore, antioxidants should be able to prevent this reaction. In this study, the best concentration and time to incubate glucose with hemoglobin was investigated. Then the glycosylation degree of hemoglobin in the presence of flavonoids and their absence was measured by means of a colorimetric method. Different concentration of flavonoids (Quercetin, Rutin, Kaempferol) were used. The preventing effect on hemoglobin glycosylation by the three concentrations; 0.5, 5, 10 micrograms/ml was estimated as follows: for Rutin; 11%, 27%, 42%, Quercetin; 3%, 37%, 52%, Kaempferol; 10%, 12%, 15% respectively. So, the in vivo effect should be investigated and then plants that containing flavonoids can be utilized to prevent or treat complication of diabetes.  相似文献   
9.
10.
Glycine receptor channels are pentameric ligand-gated ion channels that respond to the application of inhibitory neurotransmitters by opening of a chloride-selective central pore. Topiramate (TPM) is a broad-spectrum antiepileptic drug used as add-on or monotherapy for focal seizures. In the present study the interaction of TPM with glycine receptor channels was studied on outside-out patches from HEK293 cells expressing alpha1beta glycine receptor channels. The patch clamp techniques combined with ultra fast solution exchange enabled us to investigate the kinetics of receptor channels in presence of TPM. Our study showed no agonistic or potentiating effect for TPM on glycine receptor channels. However, in presence of 1 mM glycine + 1 mM TPM, the desensitization got faster and the peak current amplitude decreased. After the end of glycine + TPM pulses, off-currents occurred, suggestive for a specific channel block mechanism.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号