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   13640篇
  免费   1168篇
  国内免费   988篇
耳鼻咽喉   123篇
儿科学   151篇
妇产科学   110篇
基础医学   1722篇
口腔科学   288篇
临床医学   1875篇
内科学   2080篇
皮肤病学   89篇
神经病学   745篇
特种医学   460篇
外国民族医学   10篇
外科学   1252篇
综合类   2325篇
现状与发展   2篇
一般理论   1篇
预防医学   765篇
眼科学   388篇
药学   1461篇
  14篇
中国医学   732篇
肿瘤学   1203篇
  2024年   206篇
  2023年   361篇
  2022年   646篇
  2021年   734篇
  2020年   550篇
  2019年   499篇
  2018年   479篇
  2017年   480篇
  2016年   423篇
  2015年   609篇
  2014年   760篇
  2013年   671篇
  2012年   962篇
  2011年   1170篇
  2010年   603篇
  2009年   523篇
  2008年   670篇
  2007年   629篇
  2006年   676篇
  2005年   705篇
  2004年   444篇
  2003年   377篇
  2002年   343篇
  2001年   257篇
  2000年   274篇
  1999年   356篇
  1998年   227篇
  1997年   221篇
  1996年   141篇
  1995年   147篇
  1994年   107篇
  1993年   77篇
  1992年   78篇
  1991年   76篇
  1990年   75篇
  1989年   51篇
  1988年   41篇
  1987年   23篇
  1986年   34篇
  1985年   36篇
  1984年   25篇
  1983年   11篇
  1982年   5篇
  1981年   5篇
  1980年   2篇
  1979年   6篇
  1976年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Background: Prolactin (PRL), a polypeptide hormone produced by the pituitary gland, is involved in the regulation of humoral and cell mediated immune responses. PRL levels have been investigated in several autoimmune diseases including systemic lupus erythematosus (SLE), however, yielded different and inconsistent results. This study aims to derive a more precise evaluation on plasma/serum PRL levels in SLE patients, as well as the potential influential factors.

Methods: Studies published from 1 January 1987 to 31 December 2015 in English, which comparing plasma/serum PRL levels between SLE group and control group were searched in PubMed, EMBASE and The Cochrane Library databases. Pooled standard mean difference (SMD) with 95% confidence interval (CI) was calculated by fixed-effects or random-effect model analysis. Heterogeneity test was performed by the Q statistic and quantified using I2, publication bias was evaluated using a funnel plot and Egger’s linear regression test.

Results: Five-hundred and forty-seven articles were obtained after searching databases, and 12 studies with 429 SLE patients and 326 controls were finally included. Meta-analysis revealed that, compared with the control group, the SLE group had significantly higher plasma/serum PRL levels (< 0.001), with the SMD of 1.26 and 95%CI (0.70,1.82). Subgroup analyses showed that SLE patients from Asia and Europe had higher plasma/serum PRL levels. However, no significant change in plasma/serum PRL levels was observed in SLE patients from America (> 0.05).

Conclusions: Overall, our study suggests that SLE patients have higher plasma/serum PRL level, but with a regional difference.  相似文献   

22.
Proliferation, invasion, immortalization and metastasis are the main malignant characteristics of cancer. Previous studies have shown that high-intensity focused ultrasound (US), or HIFU, can induce irreversible damage both to breast cancer cells and to tumor blood vessels. However, light microscopy alone may not always show this clearly. In this study, molecular biologic techniques were used to examine any changes in molecular markers associated with malignant behavior after exposure to HIFU. A total of 48 women with breast cancer were randomized to a control group (mastectomy) and a HIFU group (HIFU followed by mastectomy). Immunohistochemical staining, messenger RNA (mRNA) in situ hybridization and telomere-repeat amplification protocol-enzyme-linked immunosorbent assay (TRAP-ELISA) techniques were used to detect tumor expression of proliferating cell nuclear antigen (PCNA), cell adhesion molecule CD44v6, matrix metalloproteinase-9 (MMP-9), erbB2 mRNA, and to measure telomerase activity in both groups. The results demonstrated that there were significant alterations in expression of PCNA, CD44v6, MMP-9, erbB2 mRNA, and a dramatic decrease in telomerase activity in the HIFU group. It is concluded that malignant tumor characteristics are arrested by HIFU, and that biologic factors are potential markers for assessing HIFU efficacy.  相似文献   
23.
24.
25.
26.
27.

Background

The extension of sepsis encompassing the preterm newborn’s brain is often overlooked due to technical challenges in this highly vulnerable population, yet it leads to substantial long-term neurodevelopmental disabilities. In this study, we demonstrate how neonatal neuroinflammation following postnatal E. coli lipopolysaccharide (LPS) exposure in rat pups results in persistent reduction in sialylation of cerebral glycoproteins.

Methods

Male Sprague-Dawley rat pups at postnatal day 3 (P3) were injected in the corpus callosum with saline or LPS. Twenty-four hours (P4) or 21?days (P24) following injection, brains were extracted and analyzed for neuraminidase activity and expression as well as for sialylation of cerebral glycoproteins and glycolipids.

Results

At both P4 and P24, we detected a significant increase of the acidic neuraminidase activity in LPS-exposed rats. It correlated with significantly increased neuraminidase 1 (Neu1) mRNA in LPS-treated brains at P4 and with neuraminidases 1 and 4 at P24 suggesting that these enzymes were responsible for the rise of neuraminidase activity. At both P4 and P24, sialylation of N-glycans on brain glycoproteins decreased according to both mass-spectrometry analysis and lectin blotting, but the ganglioside composition remained intact. Finally, at P24, analysis of brain tissues by immunohistochemistry showed that neurons in the upper layers (II–III) of somatosensory cortex had a reduced surface content of polysialic acid.

Conclusions

Together, our data demonstrate that neonatal LPS exposure results in specific and sustained induction of Neu1 and Neu4, causing long-lasting negative changes in sialylation of glycoproteins on brain cells. Considering the important roles played by sialoglycoproteins in CNS function, we speculate that observed re-programming of the brain sialome constitutes an important part of pathophysiological consequences in perinatal infectious exposure.
  相似文献   
28.

Background

Most monoclonal antibodies against mouse antigens have been derived from rat spleen-mouse myeloma fusions, which are valuable tools for purposes ranging from general laboratory reagents to therapeutic drugs, and yet selecting and expressing them remains a time-consuming and inefficient process. Here, we report a novel approach for the rapid high-throughput selection and expression of recombinant functional rat monoclonal antibodies with different isotypes.

Results

We have developed a robust system for generating rat monoclonal antibodies through several processes involving simultaneously immunizing rats with three different antigens expressing in a mixed cell pools, preparing hybridoma cell pools, in vitro screening and subsequent cloning of the rearranged light and heavy chains into a single expression plasmid using a highly efficient assembly method, which can decrease the time and effort required by multiple immunizations and fusions, traditional clonal selection and expression methods. Using this system, we successfully selected several rat monoclonal antibodies with different IgG isotypes specifically targeting the mouse PD-1, LAG-3 or AFP protein from a single fusion. We applied these recombinant anti-PD-1 monoclonal antibodies (32D6) in immunotherapy for therapeutic purposes that produced the expected results.

Conclusions

This method can be used to facilitate an increased throughput of the entire process from multiplex immunization to acquisition of functional rat monoclonal antibodies and facilitate their expression and feasibility using a single plasmid.
  相似文献   
29.
30.
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