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   26168篇
  免费   1955篇
  国内免费   74篇
耳鼻咽喉   232篇
儿科学   749篇
妇产科学   533篇
基础医学   3151篇
口腔科学   362篇
临床医学   2621篇
内科学   5150篇
皮肤病学   702篇
神经病学   2316篇
特种医学   1043篇
外国民族医学   1篇
外科学   3978篇
综合类   416篇
一般理论   60篇
预防医学   2274篇
眼科学   851篇
药学   1783篇
中国医学   19篇
肿瘤学   1956篇
  2022年   143篇
  2021年   349篇
  2020年   227篇
  2019年   346篇
  2018年   428篇
  2017年   367篇
  2016年   400篇
  2015年   447篇
  2014年   699篇
  2013年   1026篇
  2012年   1526篇
  2011年   1574篇
  2010年   895篇
  2009年   814篇
  2008年   1522篇
  2007年   1580篇
  2006年   1563篇
  2005年   1635篇
  2004年   1592篇
  2003年   1493篇
  2002年   1482篇
  2001年   411篇
  2000年   327篇
  1999年   355篇
  1998年   356篇
  1997年   324篇
  1996年   294篇
  1995年   278篇
  1994年   248篇
  1993年   245篇
  1992年   285篇
  1991年   252篇
  1990年   230篇
  1989年   237篇
  1988年   206篇
  1987年   196篇
  1986年   192篇
  1985年   225篇
  1984年   217篇
  1983年   219篇
  1982年   248篇
  1981年   256篇
  1980年   215篇
  1979年   169篇
  1978年   178篇
  1977年   170篇
  1976年   120篇
  1975年   134篇
  1974年   143篇
  1973年   110篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
101.
Statins, inhibitors of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase, are well-established agents to lower cholesterol levels and prevent cardiovascular morbidity. Independent of their lipid-lowering properties, statins have been shown to exert pleiotropic immunomodulatory effects in various animal models of human autoimmune disease. In experimental autoimmune encephalomyelitis, a murine model for multiple sclerosis, statins prevented disease onset and even reversed paralysis when treatment was initiated after experimental autoimmune encephalomyelitis was fully established. Furthermore, well-tolerated oral statins were recently shown to exert synergistic benefit in experimental autoimmune encephalomyelitis in combination with existing agents for multiple sclerosis therapy. Based primarily on these encouraging results, statins are now being tested in clinical trials as a mono-therapy for multiple sclerosis, as well as in combination with approved disease-modifying therapies.  相似文献   
102.
Magnetic resonance spectroscopic imaging (MRSI) provides spatially resolved metabolite information that is invaluable for both neuroscience studies and clinical applications. However, lengthy data acquisition times, which are a result of time-consuming phase encoding, represent a major challenge for MRSI. Fast MRSI pulse sequences that use echo-planar readout gradients, such as proton echo-planar spectroscopic imaging (PEPSI), are capable of fast spectral-spatial encoding and thus enable acceleration of image acquisition times. Combining PEPSI with recent advances in parallel MRI utilizing RF coil arrays can further accelerate MRSI data acquisition. Here we investigate the feasibility of ultrafast spectroscopic imaging at high field (3T and 4T) by combining PEPSI with sensitivity-encoded (SENSE) MRI using eight-channel head coil arrays. We show that the acquisition of single-average SENSE-PEPSI data at a short TE (15 ms) can be accelerated to 32 s or less, depending on the field strength, to obtain metabolic images of choline (Cho), creatine (Cre), N-acetyl-aspartate (NAA), and J-coupled metabolites (e.g., glutamate (Glu) and inositol (Ino)) with acceptable spectral quality and localization. The experimentally measured reductions in signal-to-noise ratio (SNR) and Cramer-Rao lower bounds (CRLBs) of metabolite resonances were well explained by both the g-factor and reduced measurement times. Thus, this technology is a promising means of reducing the scan times of 3D acquisitions and time-resolved 2D measurements.  相似文献   
103.
Dopamine replacement therapy (DRT) for Parkinson's disease (PD) has recently been linked to the development of a number of nonmotor behavioral control problems. Punding, one of these nonmotor problems, is a term used to describe complex, purposeless stereotyped behaviors such as the repetitive handling or sorting of objects. A self-report questionnaire was adapted to assess punding in the context of dysfunctional hobby-related activities. We report the results of a survey of PD outpatients from a PD research clinic (n = 141) and non-PD controls (n = 103); conducted to identify clinical and psychological factors predictive of punding behaviors. The PD group reported hobbies and activities, which scored significantly higher on the Punding Scale than controls. Higher impulsivity, poorer disease-related quality of life, younger age of disease onset, and concomitant daily medication dosage from dopamine receptor agonists were independently predictive of higher Punding Scale scores in the PD group. These findings are similar to those seen in dopamine dysregulation syndrome, and provide further evidence for the role of impulsivity and age at disease onset in DRT-related nonmotor behavioral problems in PD.  相似文献   
104.
Objective Gallstone bacteria provide a reservoir for biliary infections. Slime production facilitates adherence, whereas β-glucuronidase and phospholipase generate colonization surface. These factors facilitate gallstone formation, but their influence on infection severity is unknown. Methods Two hundred ninety-two patients were studied. Gallstones, bile, and blood (as applicable) were cultured. Bacteria were tested for β-glucuronidase/phospholipase production and quantitative slime production. Infection severity was correlated with bacterial factors. Results Bacteria were present in 43% of cases, 13% with bacteremia. Severe infections correlated directly with β-glucuronidase/phospholipase (55% with vs 13% without, P < 0.0001), but inversely with slime production (55 vs 8%, slime <75 or >75, P = 0.008). Low slime production and β-glucuronidase/phospholipase production were additive: Severe infections were present in 76% with both, but 10% with either or none (P < 0.0001). β-Glucuronidase/phospholipase production facilitated bactibilia (86% with vs 62% without, P = 0.03). Slime production was 19 (±8) vs 50 (±10) for bacteria that did or did not cause bacteremia (P = 0.004). No bacteria with slime >75 demonstrated bacteremia. Conclusions Bacteria-laden gallstones are biofilms whose characteristics influence illness severity. Factors creating colonization surface (β-glucuronidase/phospholipase) facilitated bacteremia and severe infections; but abundant slime production, while facilitating colonization, inhibited detachment and cholangiovenous reflux. This shows how properties of the gallstone biofilm determine the severity of the associated illness. Presented at the annual meeting of the Society for Surgery of the Alimentary Tract, held May 20–24, 2006 in Los Angeles, California.  相似文献   
105.
106.
107.
BACKGROUND AND PURPOSE: Intimal-medial thickening (IMT) of the carotid wall is an accepted peripheral marker of atherosclerosis. It is associated with increased risk for myocardial infarction and stroke, and lower attention-executive-psychomotor functioning. The purpose of this study was to examine the relationship between IMT and brain activity during a verbal working memory (VWM) task in patients with cardiovascular disease (CVD). METHODS: Thirteen CVD patients underwent functional magnetic resonance imaging (fMRI) during a 2-Back VWM task, and B-mode ultrasound of the carotid arteries. IMT was calculated using an automated algorithm based on a validated edge-detection technique. The relationship between IMT and 2-Back-related brain activity was modeled using partial correlations controlling for age and small vessel disease as measured by white matter signal hyperintensities on MRI (WMH). RESULTS: Higher IMT was associated with lower 2-Back-related signal intensity and in the right middle frontal gyrus, independent of age and WMH. CONCLUSIONS: IMT may be one mechanism contributing to brain dysfunction in CVD. The blood oxygenation level-dependent (BOLD) contrast appears to be highly sensitive to peripheral vascular health as measured by IMT. Future studies should examine the sensitivity and specificity of the BOLD response for predicting cognitive decline in CVD.  相似文献   
108.
109.
Gonadotropin-releasing hormone (GnRH) and olfactory neurons migrate together from the olfactory placode, and GnRH neurons eventually reside in the hypothalamus. Hypogonadism in male infants may be diagnosed in the first 6 months of life but cannot be diagnosed during childhood until puberty occurs. Patients with low serum testosterone and low serum gonadotropin levels have idiopathic hypogonadotropic hypogonadism (IHH). Mutations in three genes (KAL1, FGFR1, and GNRHR) comprise most of the known genetic causes of IHH. Treatment with testosterone is indicated if fertility is not desired, whereas GnRH or gonadotropin treatment induces spermatogenesis and fertility.  相似文献   
110.
BACKGROUND: Linkage studies by us and others have confirmed that chromosome 1q23.3 is a susceptibility locus for schizophrenia. Based on this information, several research groups have published evidence that markers within both the RGS4 and CAPON genes, which are 700 kb apart, independently showed allelic association with schizophrenia. Tests of allelic association with both of these genes in our case control sample were negative. Therefore, we carried out further fine mapping between the RGS4 and CAPON genes. METHODS: Twenty-nine SNP and microsatellite markers in the 1q23.3 region were genotyped in the United Kingdom based sample of 450 cases and 450 supernormal control subjects. RESULTS: We detected positive allelic association after the eighth marker was genotyped and found that three microsatellite markers (p = .011, p = .014, p = .049) and two SNPs (p = .004, p = .043) localized in the 700 kb region between the RGS4 and CAPON genes, within the UHMK1 gene, were associated with schizophrenia. Tests of significance for marker rs10494370 remained significant following Bonferroni correction (alpha = .006) for multiple tests. Tests of haplotypic association were also significant for UHMK1 (p = .009) using empirical permutation tests, which make it unnecessary to further correct for both multiple alleles and multiple markers. CONCLUSIONS: These results provide preliminary evidence that the UHMK1 gene increases susceptibility to schizophrenia. Further confirmation in adequately powered samples is needed. UHMK1 is a serine threonine kinase nuclear protein and is highly expressed in regions of the brain implicated in schizophrenia.  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