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   21784篇
  免费   1056篇
  国内免费   90篇
耳鼻咽喉   248篇
儿科学   564篇
妇产科学   432篇
基础医学   3350篇
口腔科学   536篇
临床医学   2101篇
内科学   4691篇
皮肤病学   539篇
神经病学   2526篇
特种医学   630篇
外科学   1813篇
综合类   109篇
一般理论   13篇
预防医学   1851篇
眼科学   429篇
药学   1337篇
  1篇
中国医学   79篇
肿瘤学   1681篇
  2024年   107篇
  2023年   224篇
  2022年   414篇
  2021年   712篇
  2020年   510篇
  2019年   688篇
  2018年   701篇
  2017年   533篇
  2016年   632篇
  2015年   743篇
  2014年   881篇
  2013年   1097篇
  2012年   1770篇
  2011年   1886篇
  2010年   1002篇
  2009年   905篇
  2008年   1478篇
  2007年   1480篇
  2006年   1393篇
  2005年   1306篇
  2004年   1211篇
  2003年   1090篇
  2002年   928篇
  2001年   113篇
  2000年   74篇
  1999年   120篇
  1998年   181篇
  1997年   155篇
  1996年   111篇
  1995年   89篇
  1994年   68篇
  1993年   48篇
  1992年   31篇
  1991年   22篇
  1990年   34篇
  1989年   21篇
  1988年   15篇
  1987年   18篇
  1986年   7篇
  1985年   11篇
  1984年   12篇
  1983年   14篇
  1982年   11篇
  1981年   9篇
  1980年   15篇
  1979年   9篇
  1978年   7篇
  1977年   8篇
  1975年   6篇
  1973年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.

Background:

Lung cancer is the leading cause of cancer-related deaths worldwide. The typical and atypical carcinoid (TC and AC), the large-cell neuroendocrine carcinoma (LCNEC) and the small-cell lung cancers (SCLC) are subgroups of pulmonary tumours that show neuroendocrine differentiations. With the rising impact of molecular pathology in routine diagnostics the interest for reliable biomarkers, which can help to differentiate these subgroups and may enable a more personalised treatment of patients, grows.

Methods:

A collective of 70 formalin-fixed, paraffin-embedded (FFPE) pulmonary neuroendocrine tumours (17 TCs, 17 ACs, 19 LCNECs and 17 SCLCs) was used to identify biomarkers by high-throughput sequencing. Using the Illumina TruSeq Amplicon-Cancer Panel on the MiSeq instrument, the samples were screened for alterations in 221 mutation hot spots of 48 tumour-relevant genes.

Results:

After filtering >26 000 detected variants by applying strict algorithms, a total of 130 mutations were found in 29 genes and 49 patients. Mutations in JAK3, NRAS, RB1 and VHL1 were exclusively found in SCLCs, whereas the FGFR2 mutation was detected in LCNEC only. KIT, PTEN, HNF1A and SMO were altered in ACs. The SMAD4 mutation corresponded to the TC subtype. We prove that the frequency of mutations increased with the malignancy of tumour type. Interestingly, four out of five ATM-mutated patients showed an additional alteration in TP53, which was by far the most frequently altered gene (28 out of 130; 22%). We found correlations between tumour type and IASLC grade for ATM- (P=0.022; P=0.008) and TP53-mutated patients (P<0.001). Both mutated genes were also associated with lymph node invasion and distant metastasis (P⩽0.005). Furthermore, PIK3CA-mutated patients with high-grade tumours showed a reduced overall survival (P=0.040) and the mutation frequency of APC and ATM in high-grade neuroendocrine lung cancer patients was associated with progression-free survival (PFS) (P=0.020).

Conclusions:

The implementation of high-throughput sequencing for the analysis of the neuroendocrine lung tumours has revealed that, even if these tumours encompass several subtypes with varying clinical aggressiveness, they share a number of molecular features. An improved understanding of the biology of neuroendocrine tumours will offer the opportunity for novel approaches in clinical management, resulting in a better prognosis and prediction of therapeutic response.  相似文献   
92.
An increased prevalence of liver diseases such as hepatitis C and nonalcoholic fatty liver results in an augmented incidence of the most common form of liver cancer, hepatocellular carcinoma (HCC). HCC is most often found in the cirrhotic liver and it can therefore be challenging to rely on anatomical information alone when diagnosing HCC. Valuable information on specific cellular metabolism can be obtained with high sensitivity thanks to an emerging magnetic resonance (MR) technique that uses 13C labeled hyperpolarized molecules. Our interest was to explore potential new high contrast metabolic markers of HCC using hyperpolarized 13C‐MR. This work led to the identification of a class of substrates, low molecular weight ethyl‐esters, which showed high specificity for carboxyl esterases and proved in many cases to possess good properties for signal enhancement. In particular, hyperpolarized [1,3‐13C2]ethyl acetoacetate (EAA) was shown to provide a metabolic fingerprint of HCC. Using this substrate a liver cancer implanted in rats was diagnosed as a consequence of an ~4 times higher metabolic substrate‐to‐product ratio than in the surrounding healthy tissue, (p = 0.009). Unregulated cellular uptake as well as cosubstrate independent enzymatic conversion of EAA, made this substrate highly useful as a hyperpolarized 13C‐MR marker. This could be appreciated by the signal‐to‐noise (SNR) obtained from EAA, which was comparable to the SNR reported in a literature liver cancer study with state‐of‐the‐art hyperpolarized substrate, [1‐13C]pyruvate. Also, the contrast‐to‐noise (CNR) in the EAA based metabolic ratio images was significantly improved compared with the CNR in equivalent images reported using [1‐13C]pyruvate.  相似文献   
93.
Chronic rhinosinusitis (CRS) is a common condition and affects the quality of life of approximately 16 % of adults in US and 10.9 % in Europe. Hyaluronan (HA) is a nonsulphate glycosaminoglycan found in the extracellular matrix of connective tissues, and plays an important role in the healing process and repair of mucosal surfaces. We aim to evaluate the effect of HA on nasal symptoms and endoscopic appearance in patients with CRS and nasal polyps (NP) who have not undergone sinus surgery. Eighty patients older than 18 years old were randomized to receive either open-label nebulized saline solution (NS) or intranasal corticosteroid spray (ICS) 200 µg bid or nebulized sodium hyaluronate (NHA, YABRO®) or both ICS and NHA. Results were collected at 1 month, 3 months and 3 months after treatment. Significant improvements in nasal symptoms scores, endoscopic appearance scores, radiologic scores, rhinomanometry and saccharine clearance test were observed in the NHA, ICS and ICS + NHA groups after 1 month and 3 months of treatment compared with baseline (all p ≤ 0.005). The use of oral steroids was significantly reduced after 3 months of therapy in the same groups versus baseline (all p < 0.05). The incidence of adverse events at 3 months was similar between the 4 groups (all p > 0.05). Throat irritation, nasal burning and drug-related epistaxis were not reported in the group NHA. HA, as a nebulized nasal douche preparation, improved nasal symptoms and endoscopic appearances in patients with CRS and NP who have not undergone sinus surgery.  相似文献   
94.
95.
Reprogramming of metabolism is a well-established property of cancer cells that is receiving growing attention as potential therapeutic target. Oral squamous cell carcinomas (OSCC) are aggressive and drugs-resistant human tumours displaying wide metabolic heterogeneity depending on their malignant genotype and stage of development. Dichloroacetate (DCA) is a specific inhibitor of the PDH-regulator PDK proved to foster mitochondrial oxidation of pyruvate. In this study we tested comparatively the effects of DCA on three different OSCC-derived cell lines, HSC-2, HSC-3, PE15. Characterization of the three cell lines unveiled for HSC-2 and HSC-3 a glycolysis-reliant metabolism whereas PE15 accomplished an efficient mitochondrial oxidative phosphorylation. DCA treatment of the three OSCC cell lines, at pharmacological concentrations, resulted in stimulation of the respiratory activity and caused a remarkably distinctive pro-apoptotic/cytostatic effect on HSC-2 and HSC-3. This was accompanied with a large remodeling of the mitochondrial network, never documented before, leading to organelle fragmentation and with enhanced production of reactive oxygen species. The data here presented indicate that the therapeutic efficacy of DCA may depend on the specific metabolic profile adopted by the cancer cells with those exhibiting a deficient mitochondrial oxidative phosphorylation resulting more sensitive to the drug treatment.  相似文献   
96.
One challenge in biology is signal transduction monitoring in a physiological context. Intravital imaging techniques are revolutionizing our understanding of tumor and host cell behaviors in the tumor environment. However, these deep tissue imaging techniques have not yet been adopted to investigate the second messenger calcium (Ca2+). In the present study, we established conditions that allow the in vivo detection of Ca2+ signaling in three-dimensional tumor masses in mouse models. By combining intravital imaging and a skinfold chamber technique, we determined the ability of photodynamic cancer therapy to induce an increase in intracellular Ca2+ concentrations and, consequently, an increase in cell death in a p53-dependent pathway.  相似文献   
97.
98.
99.
100.
Although the prevalence of malnutrition in the old age is increasing worldwide a synthetic understanding of the impact of aging on the intake, digestion, and absorption of nutrients is still lacking. This review article aims at filling the gap in knowledge between the functional decline of the aging gastrointestinal tract (GIT) and the consequences of malnutrition on the health status of elderly. Changes in the aging GIT include the mechanical disintegration of food, gastrointestinal motor function, food transit, chemical food digestion, and functionality of the intestinal wall. These alterations progressively decrease the ability of the GIT to provide the aging organism with adequate levels of nutrients, what contributes to the development of malnutrition. Malnutrition, in turn, increases the risks for the development of a range of pathologies associated with most organ systems, in particular the nervous-, muscoskeletal-, cardiovascular-, immune-, and skin systems. In addition to psychological, economics, and societal factors, dietary solutions preventing malnutrition should thus propose dietary guidelines and food products that integrate knowledge on the functionality of the aging GIT and the nutritional status of the elderly. Achieving this goal will request the identification, validation, and correlative analysis of biomarkers of food intake, nutrient bioavailability, and malnutrition.  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