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:      
  示例: 沙坡头地区,人工植被区,变化  检索词用空格隔开表示必须包含全部检索词,用“,”隔开表示只需满足任一检索词即可!
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   1889篇
  免费   72篇
  国内免费   11篇
耳鼻咽喉   12篇
儿科学   45篇
妇产科学   51篇
基础医学   370篇
口腔科学   35篇
临床医学   110篇
内科学   350篇
皮肤病学   43篇
神经病学   111篇
特种医学   52篇
外科学   350篇
综合类   23篇
预防医学   144篇
眼科学   29篇
药学   96篇
中国医学   5篇
肿瘤学   146篇
  2024年   17篇
  2023年   12篇
  2022年   14篇
  2021年   23篇
  2020年   25篇
  2019年   44篇
  2018年   44篇
  2017年   28篇
  2016年   35篇
  2015年   43篇
  2014年   57篇
  2013年   66篇
  2012年   114篇
  2011年   107篇
  2010年   77篇
  2009年   59篇
  2008年   83篇
  2007年   81篇
  2006年   75篇
  2005年   91篇
  2004年   85篇
  2003年   79篇
  2002年   74篇
  2001年   71篇
  2000年   41篇
  1999年   45篇
  1998年   15篇
  1997年   12篇
  1996年   9篇
  1994年   9篇
  1992年   25篇
  1991年   33篇
  1990年   28篇
  1989年   28篇
  1988年   31篇
  1987年   33篇
  1986年   25篇
  1985年   16篇
  1984年   23篇
  1983年   19篇
  1979年   16篇
  1978年   22篇
  1977年   10篇
  1976年   8篇
  1975年   8篇
  1974年   12篇
  1972年   10篇
  1971年   12篇
  1969年   8篇
  1968年   13篇
排序方式: 共有1972条查询结果,搜索用时 0 毫秒
21.
Puumala virus (PUUV), carried by bank voles (Myodes glareolus), is the medically most important hantavirus in Central and Western Europe. In this study, a total of 523 bank voles (408 from Germany, 72 from Slovakia, and 43 from Czech Republic) collected between the years 2007–2012 were analyzed for the presence of hantavirus RNA. Partial PUUV genome segment sequences were obtained from 51 voles. Phylogenetic analyses of all three genome segments showed that the newfound strains cluster with other Central and Western European PUUV strains. The new sequences from ?umava (Bohemian Forest), Czech Republic, are most closely related to the strains from the neighboring Bavarian Forest, a known hantavirus disease outbreak region. Interestingly, the Slovak strains clustered with the sequences from Bohemian and Bavarian Forests only in the M but not S segment analyses. This well-supported topological incongruence suggests a segment reassortment event or, as we analyzed only partial sequences, homologous recombination. Our data highlight the necessity of sequencing all three hantavirus genome segments and of a broader bank vole screening not only in recognized endemic foci but also in regions with no reported human hantavirus disease cases.  相似文献   
22.
In this study, the acute effect of 3-nitropropionic acid was investigated on open field and startle behavior of rats, and on their cortical electrical activity. Spontaneous locomotor activity, acoustic startle response, and pre-pulse inhibition of acoustic startle were measured in male Wistar rats (10 weeks old, 180-200 g body weight) after a single dose of 10 or 20 mg/kg i.p. 3-nitropropionic acid. After the behavioral tests, the rats were anaesthetized, and spontaneous cortical electrical activity was recorded. The vertical, horizontal and local open field performance showed dose-dependent deterioration in the rats treated with 3-nitropropionic acid. The number of "noise-positive" startle responses showed non-significant changes, but the inhibition by pre-pulse was significantly reduced in the high dose animals. High dose also increased the proportion of low-frequencies in the cortical activity. 3-nitropropionic acid, known primarily to act in repeated doses (e.g., in animal models of Huntington's disease) had also some clear-cut acute effects on behavioral and electrophysiological parameters of the treated rats.  相似文献   
23.
Ni GX  Lu WW  Xu B  Chiu KY  Yang C  Li ZY  Lam WM  Luk KD 《Biomaterials》2006,27(29):5127-5133
The bone-bonding behaviors of various biomaterials have been extensively investigated. However, the precise mechanisms of bone bonding have not yet been clarified, and the differences in interfacial behaviors of biomaterial bonding with cancellous bone and cortical bone have not yet been understood. In this study, strontium-containing hydroxyapatite (Sr-HA) cement, in which 10% calcium ions were substituted by strontium, was performed in a rabbit hip replacement model. Six months later, the morphology and chemical composition of interfaces between Sr-HA cement with cancellous bone and cortical bone were evaluated by field emission scanning electron microscopy (FESEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Remarkable differences between these two interfaces were suggested both in morphology and chemical compositions. An apatite layer was found between Sr-HA cement and cancellous bone with a thickness of about 70 microm. However, only a very thin interface (about 1 microm) was formed with cortical bone. As for the cancellous bone/cement interface, high ions intensity of Ca, P, Sr, Na, and O were confirmed by FESEM-EDX and ToF-SIMS. Differences in morphology and chemical component between these two interfaces provided convincing evidences for the proposed dissolution-precipitation coupling mechanism in the formation of biological apatite.  相似文献   
24.
Digestive Diseases and Sciences - Patients with SARS-CoV-2 who present with gastrointestinal symptoms have a milder clinical course than those who do not. Risk factors for severe COVID-19 disease...  相似文献   
25.
26.
Novel mutations in the PATCHED gene in basal cell nevus syndrome   总被引:1,自引:0,他引:1  
Basal cell nevus syndrome (BCNS) is an autosomal dominant disease characterized by the presence of multiple basal cell carcinomas, odontogenic keratocysts, palmoplantar pits, and calcification in the falx cerebri caused by mutational inactivation of the PTCH gene. To investigate the molecular basis of BCNS in Chinese, we did a mutational analysis of the PTCH gene by performing denaturing high-performance liquid chromatography in three BCNS families. In this study, three novel mutations, two 1-bp frameshift insertions, i.e., 1468insA and 2392insC, and one 8-bp deletion, i.e., IVS5 + 1delGTAAGTGT, affecting a donor splice site, were identified. All the mutations cause a shift of the open reading frames and lead to premature termination of PTCH protein translation. Our results showed that mutational inactivation of the PTCH gene causes BCNS in Chinese.  相似文献   
27.
Duchenne and Becker muscular dystrophies (DMD/BMD) are X-linked recessive disorders caused by mutations in the dystrophin gene. A large intragenic deletion has been described in about 65% of DMD/BMD patients. Mothers of affected males are DMD/BMD carriers in two thirds of the cases. Routine deletions detection in DMD/BMD males is performed using multiplex polymerase chain reaction (mPCR), RT-PCR with a protein truncation test (PTT) or using Southern blotting. In females the deletions detection is complicated by the presence of a normal gene copy on the second X-chromosome. We are presenting the diagnostic strategy using FISH for the deletions detection in the dystrophin gene of female DMD/BMD carriers. We have used a set of six cosmid probes for the detection of the most frequently deleted areas of the dystrophin gene from the Department of Human Genetics, Leiden University Medical Center. We have examined 14 mothers of DMD/BMD males with a deletion in the dystrophin gene identified using mPCR. Four mothers of affected males have been diagnosed as carriers of a deletion in the dystrophin gene. We have revealed no deletion mutations in the exons examined in a control group of four healthy females. No discrepancy has been found between the FISH analysis results and the results of mPCR. Our results indicate that FISH is an effective and direct method for the identification of DMD/BMD carriers and we suggest this method as a method of a first choice in the identification of DMD/BMD carriers.  相似文献   
28.
Consistent deficits in the cholinergic system are evident in Alzheimer's disease (AD) patients, including selective loss of alpha4beta2 nicotinic acetylcholine receptors in the brains of AD patients. Knockout mice for the beta2 subunit have impaired neuronal survival in ageing. Accordingly, we have analysed polymorphisms in the genes that encode the alpha4 and beta2 subunits, CHRNA4 and CHRNB2 respectively, for genetic associations with late-onset AD. A significant association for disease was observed for a non-coding polymorphism in CHRNB2 (odds ratio=0.57, 95% confidence interval=0.35-0.95, P=0.024). Replication analysis was performed in two further sample sets. While these did not individually yield significant results, a significant association remained when all samples were pooled (odds ratio=0.70, 95% confidence interval=0.52-0.95, P=0.019). These data suggest that this variant warrants further examination in large case-control series.  相似文献   
29.
PurposeIn 2015, the American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology (AMP) published consensus standardized guidelines for sequence-level variant classification in Mendelian disorders. To increase accuracy and consistency, the Clinical Genome Resource Familial Hypercholesterolemia (FH) Variant Curation Expert Panel was tasked with optimizing the existing ACMG/AMP framework for disease-specific classification in FH. In this study, we provide consensus recommendations for the most common FH-associated gene, LDLR, where >2300 unique FH-associated variants have been identified.MethodsThe multidisciplinary FH Variant Curation Expert Panel met in person and through frequent emails and conference calls to develop LDLR-specific modifications of ACMG/AMP guidelines. Through iteration, pilot testing, debate, and commentary, consensus among experts was reached.ResultsThe consensus LDLR variant modifications to existing ACMG/AMP guidelines include (1) alteration of population frequency thresholds, (2) delineation of loss-of-function variant types, (3) functional study criteria specifications, (4) cosegregation criteria specifications, and (5) specific use and thresholds for in silico prediction tools, among others.ConclusionEstablishment of these guidelines as the new standard in the clinical laboratory setting will result in a more evidence-based, harmonized method for LDLR variant classification worldwide, thereby improving the care of patients with FH.  相似文献   
30.
Keratin 19 and nuclear reactivity to an endogenous lectin, galectin-1, represent a potential marker of epidermal stem cells. We detected expression of keratin 19 and nuclear binding sites for galectin-1 in adult cells migrating from the hair follicle, where cells expressing keratin 19 are located in the bulge region. The results were compared with the expression of both markers in cells adhering from suspension prepared from the interfollicular epidermis without keratin-19-positive cells and with nuclear binding sites for galectin-1. The results were compared with data from basal cell carcinomas. All cells were analyzed concerning size, as it is known that cell diameter influences the clonogenic potential of keratinocytes. The major result of this study is the observation of transient expression of keratin 19 and nuclear galectin-1 binding sites in originally negative interfollicular epidermal cells induced by adhesion. These cells were very small in size, similar to basal cells of the interfollicular epidermis or the bulge region of the hair follicle. The influence of the suspension regimen on beta1-integrin expression, cell diameter and growth was also monitored. A population of cells highly positive for beta1 integrin of the same diameter as keratin-19-positive cells insensitive to induction of terminal differentiation by lack of anchorage was characterized. Cells of the same size were also observed in the keratin-19-positive cells of basal cell carcinomas. In conclusion, the expression of poor levels of differentiation induced by cell adhesion is transient. Also, keratin 19 expression should not be exclusively regarded as a marker of stem cell activity.  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