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   25877篇
  免费   1275篇
  国内免费   219篇
耳鼻咽喉   170篇
儿科学   650篇
妇产科学   226篇
基础医学   3290篇
口腔科学   460篇
临床医学   1618篇
内科学   7211篇
皮肤病学   387篇
神经病学   1653篇
特种医学   1066篇
外科学   4466篇
综合类   100篇
预防医学   638篇
眼科学   456篇
药学   1690篇
中国医学   43篇
肿瘤学   3247篇
  2023年   187篇
  2022年   368篇
  2021年   653篇
  2020年   322篇
  2019年   497篇
  2018年   643篇
  2017年   475篇
  2016年   642篇
  2015年   668篇
  2014年   910篇
  2013年   1036篇
  2012年   1638篇
  2011年   1825篇
  2010年   1029篇
  2009年   873篇
  2008年   1506篇
  2007年   1738篇
  2006年   1698篇
  2005年   1687篇
  2004年   1633篇
  2003年   1590篇
  2002年   1545篇
  2001年   350篇
  2000年   286篇
  1999年   350篇
  1998年   371篇
  1997年   301篇
  1996年   288篇
  1995年   223篇
  1994年   203篇
  1993年   183篇
  1992年   205篇
  1991年   192篇
  1990年   168篇
  1989年   147篇
  1988年   117篇
  1987年   91篇
  1986年   94篇
  1985年   72篇
  1984年   66篇
  1983年   52篇
  1982年   50篇
  1981年   50篇
  1980年   29篇
  1979年   33篇
  1978年   33篇
  1977年   24篇
  1975年   25篇
  1974年   23篇
  1973年   22篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.

Background and aim

Recent studies of several carcinomas have reported that aquaporin possesses novel oncogenic properties. The aim of this study was to clarify the involvement of aquaporin-1 and ?5 in the proliferation, invasion and metastasis of soft tissue sarcomas.

Materials and methods

The expression of aquaporin-1 and -5 was immunohistochemically examined in 73 soft tissue sarcomas as well as in benign, locally aggressive soft tissue tumors, and in soft tissues of adult humans and human fetuses. The mRNA and protein expression of aquaporin-1 and -5 genes were quantified in 19 sarcoma tissues.

Results

Aquaporin-1 was expressed in the tumor cells of 37 (51%) and aquaporin-5 in 29 (40%) of 73 soft tissue sarcomas. Two expression patterns were identified: a differentiation-dependent pattern, similar to their expression in adult human soft tissue and in benign soft tissue tumors, and an aggressiveness-related pattern, that is similar to their expression in the mesenchymal cells of the developing fetal limb. The latter expression pattern proved to be an independent prognostic factor for patients with soft tissue sarcoma, in which aquaporin-1 was related to the invasiveness, and aquaporin-5 to the proliferation of soft tissue sarcoma cells.

Conclusion

These results indicate pivotal roles for aquaporin-1 and -5 in the aggressive growth and metastatic potential of soft tissue sarcomas, suggesting that they are promising targets for the treatment of patients with intractable soft tissue sarcoma.  相似文献   
992.

Objective

Immunodeficiency, centromeric instability, and facial anomalies (ICF) syndrome is a rare autosomal recessive primary immunodeficiency. Hypogammaglobulinemia is a major manifestation of ICF syndrome, but immunoglobulin replacement therapy does not seem to be effective for some ICF patients. Therefore, we aimed to reassess the immunological characteristics of this syndrome.

Methods

Eleven Japanese patients with ICF syndrome were enrolled. We performed whole-exome sequencing in four cases and homozygosity mapping using SNP analysis in two. We evaluated their clinical manifestations and immunological status.

Results

We newly diagnosed six ICF patients who had tentatively been diagnosed with common variable immunodeficiency. We identified two novel mutations in the DNMT3B gene and one novel mutation in the ZBTB24 gene. All patients showed low serum IgG and/or IgG2 levels and were treated by periodic immunoglobulin replacement therapy. Three of the six patients showed worse results of the mitogen-induced lymphocyte proliferation test. Analyses of lymphocyte subpopulations revealed that CD19+CD27+ memory B cells were low in seven of nine patients, CD3+ T cells were low in three patients, CD4/8 ratio was inverted in five patients, CD31+ recent thymic emigrant cells were low in two patients, and CD19+ B cells were low in four patients compared with those in the normal controls. ICF2 patients showed lower proportions of CD19+ B cells and CD16+56+ NK cells and significantly higher proportions of CD3+ T cells than ICF1 patients. T cell receptor excision circles were undetectable in two patients. Despite being treated by immunoglobulin replacement therapy, three patients died of influenza virus, fatal viral infection with persistent Epstein–Barr virus infection, or JC virus infection. One of three dead patients showed normal intelligence with mild facial anomaly. Two patients presented with autoimmune or inflammatory manifestations. Infectious episodes decreased in three patients who were started on trimethoprim–sulfamethoxazole and/or antifungal drugs in addition to immunoglobulin replacement therapy. These patients might have suffered from T cell immunodeficiency.

Conclusion

These results indicate that patients with ICF syndrome have a phenotype of combined immunodeficiency. Thus, to achieve a better prognosis, these patients should be treated as having combined immunodeficiency in addition to receiving immunoglobulin replacement therapy.
  相似文献   
993.

Purpose

Protein ingestion after resistance exercise increases muscle protein synthesis (MPS) in a dose-dependent manner. However, the molecular mechanism(s) for the dose-dependency of MPS remains unclear. This study aimed to determine the dose response of mammalian target of rapamycin (mTOR) signaling in muscle with ingestion of protein after resistance exercise.

Methods

Fifteen male subjects performed four sets of six unilateral isokinetic concentric knee extensions. Immediately after exercise, eight subjects consumed water only. The other seven subjects, in a randomized-order crossover design, took either a 10 [3.6 g essential amino acids (EAA)] or 20 g (7.1 g EAA) solution of whey protein. Muscle biopsies from the vastus lateralis muscle were taken 30 min before and 1 h after resistance exercise. Phosphorylation of Akt (Ser473), mTOR (Ser2448), 4E-BP1 (Thr37/46), and S6K1 (Thr389) was measured by western blotting.

Results

Concentric knee extension exercise alone did not increase phosphorylation of Akt and mTOR 1 h after exercise, but ingesting protein after exercise significantly increased the phosphorylation of Akt and mTOR in a dose-dependent manner (P < 0.05). 4E-BP1 phosphorylation significantly decreased after resistance exercise (P < 0.05), but subjects who took 10 or 20 g of protein after exercise showed increased 4E-BP1 from post-exercise dephosphorylation (P < 0.05). S6K1 phosphorylation significantly increased after resistance exercise (P < 0.05), and 20 g of protein further increased S6K1 phosphorylation compared with ingestion of 10 g (P < 0.05).

Conclusions

These findings suggest that whey protein intake after resistance exercise activates mTOR signaling in a dose-dependent manner in untrained men.  相似文献   
994.
Mutated epidermal growth factor receptor (EGFR) and signaling pathways were associated with multiple brain and intra-pulmonary metastases, oncogenic progression and metastasis. However, features of metastasis to other organs and the independent prognostic influence of metastatic lesions were not elucidated in patients with lung cancer harboring EGFR mutations. Between January 2007 and April 2012, we treated 277 patients diagnosed with stage IV lung adenocarcinoma. Studied were 246 patients with available tumor EGFR mutation data who also underwent radiographic evaluation of lung, abdominal, brain, and bone metastases. The EGFR mutated group (N = 98) had significantly more metastatic lesions in the brain and bone than the wild-type group (N = 148): brain, 3 (1–93) versus 2 (1–32) median (range), P = 0.023; bone, 3 (1–43) versus 2 (1–27), P = 0.035, respectively. In addition, EGFR mutations were significantly more frequent in patients with multiple than non-multiple lung metastases (24/40 vs. 12/42, P = 0.004). Multivariate analysis showed that bone metastasis was a significant independent negative predictive factor of overall survival (OS) in patients with mutated [hazard ratio (HR) 2.04; 95 % confidence interval (CI) 1.17–3.64; P = 0.011] and wild-type EGFR (HR 2.09; 95 % CI 1.37–3.20; P < 0.001). In conclusion, patients with mutated EGFR had more lung, brain, and bone metastases, and bone metastasis was an independent negative predictor of OS.  相似文献   
995.

Background

Adenosine-to-inosine (A-to-I) RNA editing is catalyzed by adenosine deaminases acting on RNA (ADAR) enzymes. Recent evidence suggests that RNA editing of antizyme inhibitor 1 (AZIN1) RNA is emerging as a key epigenetic alteration underlying cancer pathogenesis.

Methods

We evaluated AZIN1 RNA editing levels, and the expression of its regulator, ADAR1, in 280 gastric tissues from 140 patients, using a RNA editing site-specific quantitative polymerase chain reaction assays. We also analyzed the clinical significance of these results as disease biomarkers in gastric cancer (GC) patients.

Results

Both AZIN1 RNA editing levels and ADAR1 expression were significantly elevated in GC tissues compared with matched normal mucosa (P?<?0.0001, 0.0008, respectively); and AZIN1 RNA editing was positively correlated with ADAR1 expression. Elevated expression of ADAR1 significantly correlated with poor overall survival (P?=?0.034), while hyper-edited AZIN1 emerged as an independent prognostic factor for OS and disease-free survival in GC patients [odds ratio (OR):1.98, 95% CI 1.17–3.35, P?=?0.011, OR: 4.55, 95% CI 2.12–9.78, P?=?0.0001, respectively]. Increased AZIN1 RNA editing and ADAR1 over-expression were significantly correlated with key clinicopathological factors, such as advanced T stage, presence of lymph node metastasis, distant metastasis, and higher TNM stages in GC patients. Logistic regression analysis revealed that hyper-editing status of AZIN1 RNA was an independent risk factor for lymph node metastasis in GC patients [hazard ratio (HR):3.03, 95% CI 1.19–7.71, P?=?0.02]. Conclusions: AZIN1 RNA editing levels may be an important prognostic biomarker in GC patients, and may serve as a key clinical decision-making tool for determining preoperative treatment strategies in GC patients.
  相似文献   
996.
997.
Photodynamic therapy (PDT) is a new therapeutic approach for the palliative treatment of malignant bile duct obstruction. In this study, we designed photosensitizer-embedded self-expanding nonvascular metal stent (PDT-stent) which allows repeatable photodynamic treatment of cholangiocarcinoma without systemic injection of photosensitizer. Polymeric photosensitizer (pullulan acetate-conjugated pheophorbide A; PPA) was incorporated in self-expanding nonvascular metal stent. Residence of PPA in the stent was estimated in buffer solution and subcutaneous implantation on mouse. Photodynamic activity of PDT-stent was evaluated through laserexposure on stent-layered tumor cell lines, HCT-116 tumor-xenograft mouse models and endoscopic intervention of PDT-stent on bile duct of mini pigs. Photo-fluorescence imaging of the PDT-stent demonstrated homogeneous embedding of polymeric Pheo-A (PPA) on stent membrane. PDT-stent sustained its photodynamic activities at least for 2 month. And which implies repeatable endoscopic PDT is possible after stent emplacement. The PDT-stent after light exposure successfully generated cytotoxic singlet oxygen in the surrounding tissues, inducing apoptotic degradation of tumor cells and regression of xenograft tumors on mouse models. Endoscopic biliary in-stent photodynamic treatments on minipigs also suggested the potential efficacy of PDT-stent on cholangiocarcinoma. In vivo and in vitro studies revealed our PDT-stent, allows repeatable endoscopic biliary PDT, has the potential for the combination therapy (stent plus PDT) of cholangiocarcinoma.  相似文献   
998.
CAPN3 (also called p94/calpain‐3) is a skeletal muscle‐specific calpain, an intracellular cysteine protease. Loss of CAPN3 protease activity and/or structural functions cause limb‐girdle muscular dystrophy type 2A (LGMD2A). However, the precise mechanism of action of CAPN3 in skeletal muscles in vivo remains largely elusive. By studying the protein modifications that regulate CAPN3 activity, we found that CAPN3 was phosphorylated. By performing mutagenesis and mass spectrometry analyses, we identified two Ser residues at positions 629 and 636 in human CAPN3 that are phosphorylated and showed that S629 is a major phosphorylation site. Intriguingly, rapid and exhaustive autolysis of CAPN3 was slightly attenuated by the substitution of S629. In skeletal muscles, phosphorylated CAPN3 was enriched in the myofibril fraction. These results imply that phosphorylated CAPN3 is a myofibril structural component and/or participates in myofibril‐based signaling pathways, rather than functions as a protease. We evaluated the relationship between phosphorylated CAPN3 and the pathology of LGMD2A. The level of phosphorylated CAPN3 was greatly reduced in LGMD2A muscles. Our findings suggest that phosphorylated CAPN3 is involved in the pathology of LGMD2A through defects in myofibril integrity and/or signaling pathways. This is the first report that phosphorylation of CAPN3 may be involved in its physiological function.  相似文献   
999.
We reviewed the clinicopathological findings of eight cases of sessile serrated adenoma/polyps (SSA/Ps) with carcinoma, the largest diameter of which was 10 mm or less. All lesions were polyps located in the right side of the colon. Four lesions showed submucosal invasion and one lesion invaded the proper muscle layer. The depth of invasion, however, did not seem to be related to the carcinoma area size. Most carcinomas were well to moderately differentiated tubular adenocarcinomas focally showing some serrated appearances, and the predominant component of one carcinoma was a poorly differentiated medullary growth with inflammatory stroma. Rapid progression to invasive carcinoma from SSA/P was suggested for the carcinoma with proper muscle invasion whereas one submucosally invasive carcinoma was considered to progress over 7 years. Immunohistochemically, it was suggested that with or without hMLH1 protein loss, alterations of p53 and/or Wnt signaling pathway can be involved in the cancerization through SSA/Ps. The carcinomas irregularly imitated the mucin expression of the SSA/Ps (positive for MUC5AC and MUC2, and MUC6 expression in crypt bases), which was lost with progression of the carcinomas. Analyses of small SSA/P lesions with cancerization would facilitate the understanding of the mode of progression of SSA/Ps and their early detection.  相似文献   
1000.
The ciliary zonule in the eye, also known as Zinn’s zonule, is composed of oxytalan fibers, which are bundles of microfibrils consisting mainly of fibrillin-1. However, it is still unclear which of the microfibril-associated molecules present in the ciliary zonule controls oxytalan fibers. Microfibril-associated glycoprotein-1 (MAGP-1) is the only microfibril-associated molecule identified in the human ciliary zonule. In the present study, we used siRNA against MAGP-1 in cultures of human non-pigmented ciliary epithelial cells to examine the extracellular deposition and appearance of fibrillin-1 employing Western blotting and immunofluorescence. MAGP-1 suppression led to a reduction of fibrillin-1 deposition. Immunofluorescence also confirmed that RNAi-mediated down-regulation of MAGP-1 led to suppression of fiber development. These results suggest that MAGP-1 plays a crucial role in the extracellular deposition of fibrillin-1 during formation of the human ciliary zonule.  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