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   341884篇
  免费   30631篇
  国内免费   12116篇
耳鼻咽喉   2646篇
儿科学   5160篇
妇产科学   4390篇
基础医学   57039篇
口腔科学   6742篇
临床医学   23854篇
内科学   55635篇
皮肤病学   5271篇
神经病学   31534篇
特种医学   8930篇
外国民族医学   93篇
外科学   24362篇
综合类   44062篇
现状与发展   40篇
一般理论   6篇
预防医学   14372篇
眼科学   3432篇
药学   53733篇
  78篇
中国医学   12780篇
肿瘤学   30472篇
  2023年   5411篇
  2022年   7204篇
  2021年   13993篇
  2020年   12328篇
  2019年   11736篇
  2018年   11348篇
  2017年   11258篇
  2016年   11234篇
  2015年   13041篇
  2014年   19948篇
  2013年   22823篇
  2012年   19418篇
  2011年   22643篇
  2010年   18746篇
  2009年   19149篇
  2008年   18995篇
  2007年   17314篇
  2006年   15319篇
  2005年   13306篇
  2004年   11578篇
  2003年   10638篇
  2002年   8542篇
  2001年   7284篇
  2000年   6074篇
  1999年   5302篇
  1998年   4459篇
  1997年   4328篇
  1996年   3736篇
  1995年   3707篇
  1994年   3421篇
  1993年   2986篇
  1992年   2443篇
  1991年   2250篇
  1990年   1852篇
  1989年   1594篇
  1988年   1449篇
  1987年   1282篇
  1986年   1312篇
  1985年   2257篇
  1984年   2318篇
  1983年   1665篇
  1982年   1753篇
  1981年   1502篇
  1980年   1239篇
  1979年   1033篇
  1978年   701篇
  1977年   557篇
  1976年   571篇
  1975年   432篇
  1974年   318篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
We aimed to explore the correlation between P27 expression and Helicobacter pylori (H. pylori) infection in gastric cancer, so as to provide evidence for understanding the pathogenesis of gastric cancer caused by H. pylori infection. A total of 82 samples of gastric cancer tissues and 56 samples of tumor-adjacent normal tissues collected from the gastrectomy were enrolled in this study. Then, 14C-urease breathing test was carried out to evaluate the infection of H. pylori in gastric cancer tissues, the expression of P27 in the tissue samples was detected by the immunohistochemistry staining, and the correlation between the H. pylori infection and P27 expression in gastric cancer was analyzed. Of 82 gastric cancer patients, there were 53 patients with H. pylori infection (64.63%). Among the patients with highly or moderately differentiated gastric cancer, the expression of P27 was much higher than that of patients with poorly differentiated gastric cancer (p < 0.01). Besides, comparison of the P27 expression between males and females, among different age groups, tumor sizes, TNM stages, tumor infiltration degrees, or lymph node metastasis, showed no significant differences (p > 0.05). Analysis of the correlation revealed that P27 expression was negatively correlated with the infection of H. pylori (p < 0.01). Multifactorial logistics regression analysis indicated that tumor differentiation was a risk factor of P27-positive expression in gastric cancer tissues (p < 0.01). In addition, P27 expression in the gastric cancer tissues was lower than that in the tumor-adjacent normal tissues (p < 0.01). In gastric cancer patients, expression of P27 is correlated with H. pylori infection which, via downregulating P27, can cause the cancerization of gastric mucosa, and P27, for its role in the development and progression of gastric cancer, is a potential auxiliary indicator for clinical diagnosis whether gastric cancer is complicated with H. pylori infection. So, P27 is a key indicator for diagnosis, treatment, and prognostic evaluation of disease in the advanced stage.  相似文献   
42.
子宫浆液性癌(uterine serous carcinoma,USC)是一种特殊类型的子宫内膜癌。有别于常见的子宫内膜样腺癌,USC较为少见,且恶性程度高,侵袭转移风险高,临床上预后较差。随着子宫内膜癌分子学研究的不断深入,分子学特征被应用于子宫内膜癌的病理分型诊断、治疗和预后评价中。研究发现USC中存在多种基因的突变,这些相关基因的突变对该病的诊断和预后具有重要的指导意义。同时,特异性的分子学改变为USC的靶向治疗提供了潜在的治疗靶点。目前,多种靶向治疗手段包括人表皮生长因子受体2(human epidermal growth factor receptor 2,HER2)抑制剂、免疫检查点抑制剂、抗血管生成治疗、磷脂酰肌醇3激酶(phosphoinositide 3-kinases,PI3K)通路抑制剂和多腺苷二磷酸核糖聚合酶[poly(ADP-ribose) polymerase,PARP]抑制剂等被应用于USC的临床治疗研究中,针对性的靶向治疗有望成为USC治疗的新突破。  相似文献   
43.
Cadmium is a toxic metal that can damage the brain and other organs. This study aimed to explore the protective effects of Potentilla anserine L. polysaccharide (PAP) against CdCl2-induced neurotoxicity in N2a and SH-SY5Y cells and in the cerebral cortex of BALB/c mice. In addition, we aimed to identify the potential mechanisms underlying these protective effects. Relative to CdCl2 treatment alone, pretreatment with PAP prevented the reduction in cell viability evoked by CdCl2, decreased rates of apoptosis, promoted calcium homeostasis, decreased ROS accumulation, increased mitochondrial membrane potential, inhibited cytochrome C and AIF release, and prevented the cleavage of caspase-3 and PARP. In addition, PAP significantly decreased the CdCl2-induced phosphorylation of CaMKII, Akt, and mTOR. In conclusion, PAP represents a potential therapeutic agent for the treatment of Cd-induced neurotoxicity, functioning in part via attenuating the activation of the mitochondrial apoptosis pathway and the Ca2+-CaMKII-dependent Akt/mTOR pathway.  相似文献   
44.
Blood pressure regulation is impacted by a spinal cord injury (SCI) due to impaired descending sympathetic vascular control. Common blood pressure problems in the SCI population include persistently low blood pressure with bouts of orthostatic hypotension and autonomic dysreflexia, which are more prevalent in individuals with lesions above the sixth thoracic vertebral level; however, they may occur regardless of the neurological level of injury. Although blood pressure disorders adversely impact daily function and quality of life, most individuals with SCI do not acknowledge this association. Few pharmacological options have been rigorously tested for safety and efficacy to manage blood pressure disorders in the SCI population. Furthermore, clinical management of any one blood pressure disorder may adversely impact others, as such treatment is complicated and not often prioritized.  相似文献   
45.
In the field of drug development, technology for producing human metabolites at a low cost is required. In this study, we explored the possibility of using prokaryotic water-soluble cytochrome P450 (CYP) to produce human metabolites. Streptomyces griseolus CYP105A1 metabolizes various non-steroidal anti-inflammatory drugs (NSAIDs), including diclofenac, mefenamic acid, flufenamic acid, tolfenamic acid, meclofenamic acid, and ibuprofen. CYP105A1 showed 4′-hydroxylation activity towards diclofenac, mefenamic acid, flufenamic acid, tolfenamic acid, and meclofenamic acid. It should be noted that this reaction specificity was similar to that of human CYP2C9. In the case of mefenamic acid, another metabolite, 3′-hydroxymethyl mefenamic acid, was detected as a major metabolite. Substitution of Arg at position 73 with Ala in CYP105A1 dramatically reduced the hydroxylation activity toward diclofenac, flufenamic acid, and ibuprofen, indicating that Arg73 is essential for the hydroxylation of these substrates. In contrast, substitution of Arg84 with Ala remarkably increased the hydroxylation activity towards diclofenac, mefenamic acid, and flufenamic acid. Recombinant Rhodococcus erythrocyte cells expressing the CYP105A1 variant R84A/M239A showed complete conversion of diclofenac into 4′-hydroxydiclofenac. These results suggest the usefulness of recombinant R. erythropolis cells expressing actinomycete CYP, such as CYP105A1, for the production of human drug metabolites.  相似文献   
46.
47.
PurposeOptical coherence tomography angiography (OCTA) was utilized to examine changes in ocular surface squamous neoplasia (OSSN) vascular patterns over time in individuals treated with topical medical therapy.MethodsTen individuals with OSSN diagnosed by clinical examination and high resolution (HR)-optical coherence tomography (OCT) were recruited. All individuals received topical immuno- or chemotherapy. OCTA images were obtained and analyzed at three points: presentation, mid-treatment and tumor resolution. Tumor metrics including tumor area (TA), tumor volume (TV), tumor depth (TD), and total tumor density (TTD) were calculated. Vessel area density (VAD) was also quantified within the OSSN, the subepithelium under and adjacent to the OSSN and the subepithelium of the uninvolved, contralateral eye. Vascular network changes were also subjectively evaluated.ResultsTA, TV, TD and TTD all significantly decreased with time (p < 0.001). The mean VAD within the OSSN significantly decreased (p < 0.001) between visits (presentation: 26.52 ± 6.8%, mid-treatment: 7.19 ± 5.88%, tumor resolution: 0.11 ± 0.34%). The mean subepithelial VAD under the OSSN also decreased with time (23.22 ± 11.03%, 20.99 ± 5.99% and 19.58 ± 7.08%), and after resolution the sub-tumor VAD (19.58 ± 7.08%) was comparable to the subepithelial VAD in the contralateral eye (15.47 ± 4.37%, p > 0.05). The mean VAD in the subepithelium adjacent to the OSSN increased with treatment, then decreased significantly between mid-treatment and resolution (23.26 ± 4.54, 28.30 ± 7.43% and 21.68 ± 6.10%, p = 0.009). Qualitatively, the tumor subepithelial vascular network was complex and dense but with tumor resolution appeared less tortuous and similar to the uninvolved eye.ConclusionOCTA provided insight into the pathophysiology of tumor angiogenesis, showing decreased vascular density and normalization of vascular networks associated with tumor resolution.  相似文献   
48.
吴文昊  李兴 《现代肿瘤医学》2022,(21):4022-4026
肝X受体(liver X receptors,LXRs)是孤儿核受体转录因子超家族成员,当LXRs被激活后,可调节靶基因的转录表达,不但参与胆固醇、脂肪、糖的代谢以及炎症等过程,并且在许多恶性肿瘤组织中均有表达。为全面了解肝X受体激动剂在治疗癌症中的研究现状,本文将从肝X受体激动剂与胃癌、肝癌、卵巢癌、乳腺癌、子宫内膜癌、肺癌以及结直肠癌的相关性方面进行综述。  相似文献   
49.
50.
Hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative breast cancer is defined by the presence of the estrogen receptor and/or the progesterone receptor and the absence of HER2 gene amplification. HR-positive/HER2-negative breast cancer accounts for 65%–70% of all breast cancers, and incidence increases with increasing age. Treatment varies by stage, and endocrine therapy is the mainstay of treatment in both early stage and late-stage disease. Combinations with cyclin-dependent kinase 4/6 inhibitors have reduced distant recurrence in the early stage setting and improved overall survival in the metastatic setting. Chemotherapy is used based on stage and tumor biology in the early stage setting and after endocrine resistance for advanced disease. New therapies, including novel endocrine agents and antibody-drug conjugates, are now changing the treatment landscape. With the availability of new treatment options, it is important to define the optimal sequence of treatment to maximize clinical benefit while minimizing toxicity. In this review, the authors first discuss the pathologic and molecular features of HR-positive/HER2-negative breast cancer and mechanisms of endocrine resistance. Then, they discuss current and emerging therapies for both early stage and metastatic HR-positive/HER2-negative breast cancer, including treatment algorithms based on current data.  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