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   8698篇
  免费   468篇
  国内免费   67篇
耳鼻咽喉   104篇
儿科学   119篇
妇产科学   74篇
基础医学   1146篇
口腔科学   214篇
临床医学   474篇
内科学   2193篇
皮肤病学   234篇
神经病学   720篇
特种医学   411篇
外科学   1661篇
综合类   47篇
一般理论   1篇
预防医学   199篇
眼科学   79篇
药学   447篇
中国医学   22篇
肿瘤学   1088篇
  2024年   7篇
  2023年   80篇
  2022年   112篇
  2021年   297篇
  2020年   135篇
  2019年   215篇
  2018年   258篇
  2017年   205篇
  2016年   275篇
  2015年   266篇
  2014年   326篇
  2013年   353篇
  2012年   569篇
  2011年   650篇
  2010年   372篇
  2009年   347篇
  2008年   512篇
  2007年   598篇
  2006年   557篇
  2005年   578篇
  2004年   510篇
  2003年   470篇
  2002年   490篇
  2001年   90篇
  2000年   70篇
  1999年   94篇
  1998年   107篇
  1997年   115篇
  1996年   73篇
  1995年   83篇
  1994年   37篇
  1993年   53篇
  1992年   40篇
  1991年   34篇
  1990年   40篇
  1989年   25篇
  1988年   29篇
  1987年   25篇
  1986年   14篇
  1985年   12篇
  1984年   8篇
  1983年   14篇
  1982年   12篇
  1981年   10篇
  1980年   10篇
  1979年   10篇
  1978年   11篇
  1975年   4篇
  1974年   7篇
  1967年   5篇
排序方式: 共有9233条查询结果,搜索用时 968 毫秒
121.
This aim of this study was to compare universal adhesives and two‐step self‐etch adhesives in terms of dentin bond fatigue durability in self‐etch mode. Three universal adhesives – Clearfil Universal, G‐Premio Bond, and Scotchbond Universal Adhesive – and three‐two‐step self‐etch adhesives – Clearfil SE Bond, Clearfil SE Bond 2, and OptiBond XTR – were used. The initial shear bond strength and shear fatigue strength of resin composite bonded to adhesive on dentin in self‐etch mode were determined. Scanning electron microscopy observations of fracture surfaces after bond strength tests were also made. The initial shear bond strength of universal adhesives was material dependent, unlike that of two‐step self‐etch adhesives. The shear fatigue strength of Scotchbond Universal Adhesive was not significantly different from that of two‐step self‐etch adhesives, unlike the other universal adhesives. The shear fatigue strength of universal adhesives differed depending on the type of adhesive, unlike those of two‐step self‐etch adhesives. The results of this study encourage the continued use of two‐step self‐etch adhesive over some universal adhesives but suggest that changes to the composition of universal adhesives may lead to a dentin bond fatigue durability similar to that of two‐step self‐etch adhesives.  相似文献   
122.
123.
Recent commercial approval of cancer vaccine, demonstrating statistically significant improvement in overall survival of prostate cancer patients has spurred renewed interest in active immunotherapies; specifically, strategies that lead to enhanced biological activity and robust efficacy for dendritic cell vaccines. A simple, widely used approach to generating multivalent cancer vaccines is to load tumor whole cell lysates into dendritic cells (DCs). Current DC vaccine manufacturing processes require co-incubation of tumor lysate antigens with immature DCs and their subsequent maturation. We compared electroloading of tumor cell lysates directly into mature DCs with the traditional method of lysate co-incubation with immature DCs. Electroloaded mature DCs were more potent in vitro, as judged by their ability to elicit significantly (p < 0.05) greater expansion of peptide antigen-specific CD8+ T cells, than either lysate-electroloaded immature DCs or lysate-co-incubated immature DCs, both of which must be subsequently matured. Expanded CD8+ T cells were functional as judged by their ability to produce IFN-γ upon antigen-specific re-stimulation. The electroloading technology used herein is an automated, scalable, functionally closed cGMP-compliant manufacturing technology supported by a Master File at CBER, FDA and represents an opportunity for translation of enhanced potency DC vaccines at clinical/commercial scale.  相似文献   
124.
Abstract

Leukotriene has been proposed as a factor of tumour induced brain oedema. Independently of its size, meningioma occasionally shows various extents of peritumoural oedema. We investigated LTC4 tissue contentsLTC4 catabolic and synthetic activity in 12 human meningiomas and their correlation with peritumoural oedema was studied. LTC4 contents were varied from 0.01 to 8.21 pg/mg tissue. When LTA4/ an unstable expoxide intermediate was incubated with tumour homogenate, LTC4 was rapidly synthesized. However; LTC4 levels generated by incubating LTA4 with each homogenate were much different in each case. Degradation of LTC4 to LTD4, LTE4, and other polar materials was also rapid by incubation with tumour homogenates. Approximately 70% of added UC4 was transformed to LTD4/ LTE4 nor 6-trans LTB4 diastereoisomers during 30 min incubation at 37 °C. The results suggested that there were significant LTC4 tissue contents and LTC4 synthetic and catabolic activity in meningiomas. Oedema index ranged from 1.0 (no peritumoural oedema) to 67.5. No significant correlationi, however', was observed not only between the LTC4 tissue contents and LTC4 synthetic or catabolic activities but also between each of these three parameters and peritumoural oedema. Thus, these results do not support a significant correlation of sulfidopeptide LTs with oedema formation in meningioma patients. Since leukotrienes are extremely unstable compounds, LTC4 tissue contents should be carefully discussed along with a consideration of rapid LTC4 synthesis and catabolism. Further role of leukotrienes in meningioma tissue should be studied.  相似文献   
125.
Individuals with inherited skin diseases often pose one of the most difficult diagnostic challenges in dermatology. The hunt for the underlying molecular pathology may involve candidate gene screening or linkage analysis, which is usually determined by the initial history, the physical findings and laboratory tests. Recent technical advances in DNA sequencing, however, are shifting the diagnostic paradigm. Notably, next‐generation sequencing allows a more comprehensive approach to diagnosing inherited diseases, with potential savings of both time and money. In the setting of a paediatric dermatology genetics clinic in Kuwait, we therefore performed whole‐exome sequencing on seven individuals without a priori detailed knowledge of the patients’ disorders: from these sequencing data, we diagnosed X‐linked hypohidrotic ectodermal dysplasia (two cases), acrodermatitis enteropathica, recessive erythropoietic protoporphyria (two siblings) and localized recessive dystrophic epidermolysis bullosa (two siblings). All these groups of disorders are clinically and genetically heterogeneous, but the sequencing data proved inherently useful in improving patient care and avoiding unnecessary investigations. Our observations highlight the value of whole‐exome sequencing, in combination with robust bioinformatics analysis, in determining the precise molecular pathology and clinical diagnosis in patients with genetic skin disorders, notably at an early stage in the clinical evaluation of these often complex disorders and thereby support a new paradigm for future diagnostics.  相似文献   
126.
127.
The purpose of this study was to evaluate the influence of duration of phosphoric acid pre‐etching on the bond durability of universal adhesives and the surface free‐energy characteristics of enamel. Three universal adhesives and extracted human molars were used. Two no‐pre‐etching groups were prepared: ground enamel; and enamel after ultrasonic cleaning with distilled water for 30 s to remove the smear layer. Four pre‐etching groups were prepared: enamel pre‐etched with phosphoric acid for 3, 5, 10, and 15 s. Shear bond strength (SBS) values of universal adhesive after no thermal cycling and after 30,000 or 60,000 thermal cycles, and surface free‐energy values of enamel surfaces, calculated from contact angle measurements, were determined. The specimens that had been pre‐etched showed significantly higher SBS and surface free‐energy values than the specimens that had not been pre‐etched, regardless of the aging condition and adhesive type. The SBS and surface free‐energy values did not increase for pre‐etching times of longer than 3 s. There were no significant differences in SBS values and surface free‐energy characteristics between the specimens with and without a smear layer. The results of this study suggest that phosphoric acid pre‐etching of enamel improves the bond durability of universal adhesives and the surface free‐energy characteristics of enamel, but these bonding properties do not increase for phosphoric acid pre‐etching times of longer than 3 s.  相似文献   
128.
Finite element analysis method (FEM) provides suitable methodology to analyze a target with complex shape such as VSP patch. In this study, by employing the FEM, Ito and colleagues showed the importance of using a large patch to eliminate the dead space between the patch and LV endocardium. Intuitionally many surgeons believed the same way, but it now has been proven mathematically. Although the FEM model has some limitation in part due to too much simplified model, I believe that the study provides useful information to the patch mechanics for VSP closure and that it will help improving the outcome of surgical treatment of VSP.  相似文献   
129.
130.

Background

Several studies have reported that viral infections are related to lung cancer. We previously reported the involvement of Torque teno virus (TTV) in patients with lung cancer and idiopathic pulmonary fibrosis. However, the role of TTV in lung cancer growth, and its influence on changes in TTV DNA titers due to idiopathic pulmonary fibrosis (IPF) in lung cancer patients are poorly understood.

Methods

Serum TTV DNA titers were measured in serum samples obtained from patients with lung cancer. Forty-eight patients with primary lung cancer, including 8 patients with IPF, were enrolled. Serum TTV DNA titers were quantitated before and after chemotherapy. In addition, patients were classified into two groups according to the presence or absence of IPF, and clinical characteristics were compared between these two groups.

Results

Among the 33 patients with partial response to treatment or stable disease in the lung cancer, the mean TTV DNA titer in 28 patients without IPF had significantly decreased after chemotherapy. In contrast, the mean TTV DNA titer in the 5 patients with IPF tended to increase after chemotherapy. In the 15 patients with progressive lung cancer, TTV DNA titers were significantly elevated in those with and without IPF.

Conclusion

In lung cancer patients without IPF, changes in TTV titers may be correlated with tumor growth. However, in lung cancer patients with IPF, TTV titers were not consistently associated with chemotherapy responses. Therefore, IPF may have an influence on changes in TTV DNA titers.  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