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   4134篇
  免费   271篇
  国内免费   32篇
耳鼻咽喉   47篇
儿科学   79篇
妇产科学   64篇
基础医学   615篇
口腔科学   65篇
临床医学   391篇
内科学   1056篇
皮肤病学   71篇
神经病学   422篇
特种医学   164篇
外科学   603篇
综合类   12篇
一般理论   2篇
预防医学   251篇
眼科学   45篇
药学   298篇
中国医学   11篇
肿瘤学   241篇
  2023年   47篇
  2022年   173篇
  2021年   282篇
  2020年   105篇
  2019年   156篇
  2018年   140篇
  2017年   110篇
  2016年   137篇
  2015年   154篇
  2014年   192篇
  2013年   216篇
  2012年   316篇
  2011年   322篇
  2010年   199篇
  2009年   155篇
  2008年   244篇
  2007年   235篇
  2006年   225篇
  2005年   196篇
  2004年   168篇
  2003年   146篇
  2002年   125篇
  2001年   31篇
  2000年   28篇
  1999年   20篇
  1998年   22篇
  1997年   20篇
  1996年   17篇
  1995年   18篇
  1994年   16篇
  1993年   9篇
  1992年   12篇
  1991年   10篇
  1990年   12篇
  1989年   13篇
  1988年   10篇
  1987年   7篇
  1986年   19篇
  1985年   14篇
  1984年   18篇
  1983年   6篇
  1982年   5篇
  1979年   9篇
  1978年   11篇
  1976年   4篇
  1975年   11篇
  1974年   5篇
  1973年   9篇
  1971年   4篇
  1970年   6篇
排序方式: 共有4437条查询结果,搜索用时 156 毫秒
91.
92.
Somatic mosaicism for DNA copy‐number alterations (SMC‐CNAs) is defined as gain or loss of chromosomal segments in somatic cells within a single organism. As cells harboring SMC‐CNAs can undergo clonal expansion, it has been proposed that SMC‐CNAs may contribute to the predisposition of these cells to genetic disease including cancer. Herein, the gross genomic alterations (>500 kbp) were characterized in uninvolved mammary glandular tissue from 59 breast cancer patients and matched samples of primary tumors and lymph node metastases. Array‐based comparative genomic hybridization showed 10% (6/59) of patients harbored one to 359 large SMC‐CNAs (mean: 1,328 kbp; median: 961 kbp) in a substantial portion of glandular tissue cells, distal from the primary tumor site. SMC‐CNAs were partially recurrent in tumors, albeit with considerable contribution of stochastic SMC‐CNAs indicating genomic destabilization. Targeted resequencing of 301 known predisposition and somatic driver loci revealed mutations and rare variants in genes related to maintenance of genomic integrity: BRCA1 (p.Gln1756Profs*74, p.Arg504Cys), BRCA2 (p.Asn3124Ile), NCOR1 (p.Pro1570Glnfs*45), PALB2 (p.Ser500Pro), and TP53 (p.Arg306*). Co‐occurrence of gross SMC‐CNAs along with point mutations or rare variants in genes responsible for safeguarding genomic integrity highlights the temporal and spatial neoplastic potential of uninvolved glandular tissue in breast cancer patients.  相似文献   
93.
94.
Research during the past century has clearly shown that endothelial injury (EI) and/or endothelial dysfunction (ED) are among the major events determining the onset of atherosclerosis. Included in the events that may elicit endothelial damage, vasoconstriction (VC) has received relatively little attention. This conceptual review attempts to show that in elastic and conduit arteries, VC is not only capable of producing EI/ED, but is also closely associated with many recognized proatherogenic stimuli. Of related interest is the observation that a number of suspected antiatherogenic stimuli oppose VC by their vasodilatory effects, lending further support to this relationship. In addition, recent developments in the knowledge of the molecular basis of VC (including the role of specific inhibitors) are discussed, and their potential for preventing lesion formation and thus becoming novel therapeutic alternatives against the onset of atherosclerosis are highlighted.  相似文献   
95.
Recent studies in hypertensive populations that have used the serum aldosterone (SA) to plasma renin activity (PRA) ratio as a screening test have demonstrated a high prevalence of primary aldosteronism (PA). This frequency is higher than that previously described when hypokalemia was used as a screening tool. However, other factors, such as the characteristics of hypertensive disease, could also influence the prevalence of PA. We studied 609 essential hypertensive patients, classified according to the Joint National Committee VI (JNC VI), in 3 different stages depending on the severity of their hypertensive disease. We measured SA and PRA and calculated the SA-PRA ratio for all patients. An SA-PRA ratio >25 was detected in 63 of 609 patients, and the fludrocortisone test confirmed the PA diagnoses in 37 of 609 (6.1%) cases. PA prevalence according to hypertension stage was as follows: stage 1, 6 of 301 cases (1.99%); stage 2, 15 of 187 cases (8.02%); and stage 3, 16 of 121 cases (13.2%). PA patients were slightly younger than the other hypertensive patients (48.4+/-10.5 vs 53.6+/-10.2 years; P<0.05). Serum potassium levels were normal in 36 of 37 PA patients; only 1 patient had minor hypokalemia. Computed tomography scans showed bilateral adrenal enlargement in 7 and an adrenal nodule in 2 cases. In summary, we found a high frequency of PA in essential hypertensives classified in stages 2 and 3 according to the JNC VI. The low frequency of computed tomography scan abnormalities and hypokalemia suggests that the diagnosis for most PA patients corresponds to attenuated forms of the disease.  相似文献   
96.
The conversion of [1,2-3H]corticosterone to 18-hydroxycorticosterone in vitro was studied on human and animal adrenal tissue homogenates. Human adrenals were surgically resected from a patient with Cushing's disease. Sheep adrenal homogenates were prepared from the pooled glands of 20 animals. Incubations supplemented with a NADPH generating system were performed in order to evaluate the effect of aminoglutethimide and its closely related compound glutethimide on corticosterone 18-hydroxylation in vitro. Increasing concentrations of the two drugs were assayed on both human and animal adrenal homogenates. Aminoglutethimide was clearly found to inhibit corticosterone 18-hydroxylation in sheep adrenal homogenates as a 72.6% inhibition occurred in the presence of only 0.2 mumole of the drug. Inhibition reached 91.1% in the presence of 0.5 mumole aminoglutethimide. When added to the human incubated adrenal, a 59.4% inhibition occurred in the presence of 0.5 mumole aminoglutethimide. Glutethimide, a sedative of wide clinical usage, was also found to inhibit corticosterone 18-hydroxylation but the inhibitory effect occurred only in the presence of much higher concentrations. In fact, 5.0 mumoles were necessary to obtain a 43.9% inhibition of 18-hydroxycorticosterone synthesis. This study clearly demonstrates the marked inhibitory effect of aminoglutethimide on corticosterone 18-hydroxylation. Glutethimide, to a lesser extent, also inhibits 18-hydroxycorticosterone synthesis.  相似文献   
97.
Constitutional thinness: unusual human phenotype of low bone quality   总被引:1,自引:0,他引:1  
CONTEXT: Low fat mass and hormonal or nutritional deficiencies are often incriminated in bone loss related to thinness. Constitutional thinness has been described in young women with low body mass index (BMI) but close-to-normal body composition, physiological menstruation, no hormonal abnormalities, and no anorexia nervosa (AN) psychological profile. OBJECTIVE: Our objective was to determine whether constitutional thinness is associated with impaired bone quality. DESIGN, SETTING, AND PARTICIPANTS: This was an observational, cross-sectional study on 25 constitutionally thin and 44 AN young women with similar low BMI (<16.5 kg/m2) and 28 age-matched controls. MAIN OUTCOME MEASURES: Femoral and lumbar spine bone mineral density by dual-energy x-ray absorptiometry, distal tibia and radius bone architecture and breaking strength by three-dimensional peripheral quantitative computed tomography, and bone turnover markers were determined. RESULTS: Constitutionally thin subjects displayed a higher percentage of fat mass than AN subjects but had similar lumbar and femoral bone mineral density, which were significantly lower than in controls (P < 0.001). Constitutionally thin subjects displayed more markedly impaired trabecular and cortical bone parameters in the distal tibia than in the radius. AN bone structure was impaired only in subjects with a long history of disease. Calculated breaking strength was decreased in constitutional thinness and long-standing AN in both the radius and the tibia. Bone markers in constitutionally thin subjects were similar to those of controls. Osteoprotegerin to receptor activator of nuclear factor kappa B ligand ratio was higher in constitutionally thin subjects than in controls or AN women. CONCLUSIONS: Young women with constitutional thinness present an unexpectedly high prevalence of low bone mass (44%) associated with small bone size, overall diminished breaking strength, but normal bone turnover. Mechanisms related to insufficient skeletal load and/or genetics are proposed to explain this new phenotype of impaired bone quality.  相似文献   
98.
Fragile X-associated tremor/ataxia syndrome (FXTAS), a late-onset movement disorder affecting FMR1 premutation carriers, is associated with cerebral and cerebellar lesions. The aim of this study was to test whether computational anatomy can detect similar patterns in asymptomatic FMR1 premutation carriers (mean age 46.7 years) with qualitatively normal -appearing grey and white matter on brain MRI. We used a multimodal imaging protocol to characterize brain anatomy by automated assessment of gray matter volume and white matter properties. Structural changes in the hippocampus and in the cerebellar motor network with decreased gray matter volume in lobule VI and white matter alterations of the corresponding afferent projections through the middle cerebellar peduncles are demonstrated. Diffuse subcortical white matter changes in both hemispheres, without corresponding gray matter alterations, are only identified through age × group interactions. We interpret the hippocampal fimbria and cerebellar changes as early alterations with a possible neurodevelopmental origin. In contrast, progression of the diffuse cerebral hemispheric white matter changes suggests a neurodegenerative process, leading to late-onset lesions, which may mark the imminent onset of FXTAS.  相似文献   
99.
The Non‐Motor Symptoms Scale (NMSS) was developed and validated in 2007 as the first instrument for the comprehensive assessment of a range of non‐motor symptoms in Parkinson's disease (PD). Thirteen years have elapsed since its introduction and extensive international validation with good psychometric attributes has been carried out. Here, we review the validation data of the NMSS and its cross‐validity with other scales, and describe the key evidence derived from use of the NMSS in clinical studies. To date, over 100 clinical studies and trials have made use of it as an outcome measure, showing consistent and strong correlations between NMSS burden and health‐related quality of life measures. Moreover, the scale has shown to be capable of detecting longitudinal changes in non‐motor symptoms, where studies have shown differential changes over time of several of the NMSS domains. The scale has become a key outcome in several randomized clinical trials. Highlighting the prevalence and importance of non‐motor symptoms to quality of life in patients with PD, the development of NMSS has also been useful in signposting clinical and biomarker based research addressing non‐motor symptoms in PD.  相似文献   
100.
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