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   1659篇
  免费   105篇
  国内免费   6篇
耳鼻咽喉   31篇
儿科学   93篇
妇产科学   31篇
基础医学   255篇
口腔科学   96篇
临床医学   131篇
内科学   280篇
皮肤病学   40篇
神经病学   87篇
特种医学   104篇
外科学   167篇
综合类   46篇
预防医学   215篇
眼科学   39篇
药学   65篇
中国医学   1篇
肿瘤学   89篇
  2022年   8篇
  2021年   26篇
  2020年   13篇
  2019年   22篇
  2018年   37篇
  2017年   25篇
  2016年   19篇
  2015年   27篇
  2014年   30篇
  2013年   45篇
  2012年   74篇
  2011年   75篇
  2010年   60篇
  2009年   53篇
  2008年   72篇
  2007年   88篇
  2006年   86篇
  2005年   68篇
  2004年   82篇
  2003年   70篇
  2002年   54篇
  2001年   49篇
  2000年   37篇
  1999年   38篇
  1998年   45篇
  1997年   35篇
  1996年   34篇
  1995年   42篇
  1994年   28篇
  1993年   16篇
  1992年   38篇
  1991年   33篇
  1990年   26篇
  1989年   42篇
  1988年   32篇
  1987年   20篇
  1986年   32篇
  1985年   33篇
  1984年   31篇
  1983年   34篇
  1982年   18篇
  1981年   9篇
  1980年   11篇
  1979年   10篇
  1978年   8篇
  1977年   9篇
  1976年   3篇
  1974年   4篇
  1972年   4篇
  1967年   2篇
排序方式: 共有1770条查询结果,搜索用时 109 毫秒
61.
Prospective clinical studies have suggested that the rate of congenital cryptorchidism has increased since the 1950s. It has been hypothesized that this may be related to environmental factors. Testicular descent occurs in two phases controlled by Leydig cell-derived hormones insulin-like peptide 3 (INSL3) and testosterone. Disorders in fetal androgen production/action or suppression of Insl3 are mechanisms causing cryptorchidism in rodents. In humans, prenatal exposure to potent estrogen diethylstilbestrol (DES) has been associated with increased risk of cryptorchidism. In addition, epidemiological studies have suggested that exposure to pesticides may also be associated with cryptorchidism. Some case-control studies analyzing environmental chemical levels in maternal breast milk samples have reported associations between cryptorchidism and chemical levels. Furthermore, it has been suggested that exposure levels of some chemicals may be associated with infant reproductive hormone levels.  相似文献   
62.
Glioblastoma muhiforme (GBM) is a highly invasive brain tumour that is unvaryingly fatal in humans clesplte even aggres- sive therapeutic approaches such as surgical resection followed by chemotherapy and radiotherapy. Unconventional treatment options such as gene therapy provide an intriguing option for curbing glioma related deaths. To date, gene therapy has yielded encouraging results in preclinical animal models as well as promising safety profiles in phase I clinical trials, but has failed to demonstrate significant therapeutic efficacy in phase III clinical trials. The most widely studied antiglioma gene therapy strategies are suicide gene therapy, genetic immuno- therapy and oncolytic virotherapy, and we have attributed the challenging transition of these modalities into the clinic to four major road- blocks : ( 1 ) anatomical features of the central nervous system, (2) the host immune system, (3) heterogeneity and invasiveness of GBM and (4) limitations in current GBM animal models. In this review, we discuss possible ways to jump these hurdles and develop new gene therapies that may be used alone or in synergy with other modalities to provide a powerful treatment option for patients with GBM.  相似文献   
63.
64.
Mass lesions presenting at the craniocervical junction often present a unique challenge due to the complex anatomic arrangement limiting access for tissue diagnosis. The transoral approach has predominantly been used for percutaneous vertebroplasty of high cervical vertebrae with limited literature describing image guided biopsy for bony lesions in this region in the pediatric patient. We describe a technique of computed tomography guided transoral biopsy of a poorly differentiated chordoma located at the C1–C2 level in a 5-year-old child, and review this diagnosis.  相似文献   
65.

Background

Lumbar disc disease (LDD) is one of the leading causes of disability in the working‐age population. A functional single‐nucleotide polymorphism (SNP), +1184T→C, in exon 8 of the cartilage intermediate layer protein gene (CILP) was recently identified as a risk factor for LDD in the Japanese population (odds ratio (OR) 1.61, 95% CI 1.31 to 1.98), with implications for impaired transforming growth factorβ1 signalling.

Aim

To validate this finding in two different ethnic cohorts with LDD.

Methods

This SNP and flanking SNPs were analysed in 243 Finnish patients with symptoms of LDD and 259 controls, and in 348 Chinese subjects with MRI‐defined LDD and 343 controls.

Results and conclusion

The results showed no evidence of association in the Finnish (OR = 1.35, 95% CI 0.97 to 1.87; p = 0.14) or the Chinese (OR = 1.05, 95% CI 0.77 to 1.43; p = 0.71) samples, suggesting that cartilage intermediate layer protein gene is not a major risk factor for symptoms of LDD in Caucasians or in the general population that included individuals with or without symptoms.Lumbar disc disease (LDD) is one of the leading causes of disability in the working‐age population. Radiological changes indicative of LDD are common, but only a proportion develops complications such as disc herniation and sciatica. Although the aetiology of LDD is not well understood, there is strong evidence for the involvement of both genetic and environmental factors.1,2A recent study reported an association between LDD and a functional single‐nucleotide polymorphism (SNP) (rs2073711), +1184T→C, in exon 8 of the cartilage intermediate layer protein gene (CILP) in a Japanese group (odds ratio (OR) 1.61, 95% CI 1.31 to –1.98).3 The allelic change resulted in amino acid substitution Ile395Thr. CILP is expressed widely in intervertebral discs and its expression increases as disc degeneration progresses.3 CILP interacts directly with transforming growth factor (TGF)β1, inhibiting the TGFβ1‐mediated induction of extracellular matrix proteins such as aggrecan and collagen II.3 Functional studies showed that the C allele (coding for Thr395) increased binding and inhibition of TGFβ1, suggesting that regulation of TGFβ1 signalling by CILP plays a crucial role in the aetiology and pathogenesis of LDD.3Argument for a causal role would be strengthened if the same association could be replicated in a distinct population, and in clinical cases of LDD defined by MRI changes indicative of LDD in general. Therefore, we investigated the association between CILP polymorphisms and LDD in a Finnish sample with symptoms of LDD, and in a Chinese sample with only MRI‐defined LDD. These samples were informative in previous studies demonstrating association of LDD with the vitamin D receptor gene4 and the Gln326Trp (Trp2) allele of COL9A25 in Chinese and the Arg103Trp (Trp3) allele of COL9A3 in Finns.6 Thus, the Chinese sample is comparable with the Finnish dataset, and a correlation can then be drawn with the Japanese dataset.  相似文献   
66.
Laminin (Lm) alpha4 chain, a constituent of Lm-411 and Lm-421, is mainly localized to mesenchyme-derived tissues, and is suggested to have a role in formation and function of endothelium, transmigration of inflammatory cells through endothelium, and invasion of certain tumors. In this study, we evaluated the distribution of alpha4 chain Lms in 33 conventional (clear cell) renal cell carcinomas (RCCs) (31 primary tumors, two metastases), two papillary RCCs, and two oncocytomas by immunohistochemistry. In all tumors, immunoreactivity for Lm alpha4 chain was found in vasculature and stroma. Basement membranes were detected around tumor cell islets in 34/37 tumors. They showed immunoreactivity for Lm alpha4 chain in 28/34 cases. Northern blotting, inhibition of protein secretion with monensin, and immunoprecipitation combined with Western blotting showed that Caki-2, ACHN, and Caki-1 renal carcinoma cell lines produce alpha4 chain Lms. In cell adhesion assay, recombinant human Lm-411 did not promote adhesion of renal carcinoma cells but inhibited adhesion to fibronectin (Fn). In cell migration assay, the cells migrated more on Lm-411 than on Fn. The results suggest that alpha4 chain Lms have a de-adhesive function and could thus play a role in detachment, migration and invasion of renal carcinoma cells in vivo.  相似文献   
67.
68.
69.
70.
Four patients with total occlusion of the left main coronary artery are described. Angina pectoris was severe (NYHA class 3-4) and had lasted 20 months to seven years. Three patients had experienced a myocardial infarction. All displayed large collaterals arising from a nearly normal right coronary artery and feeding both the left anterior descending and the left circumflex arteries. The left ventricular ejection fractions ranged from 20% to 65%, and all patients had varying degrees of left ventricular asynergy. Coronary artery bypass surgery resulted in a marked improvement in three patients; one patient who underwent an aneurysmectomy died two months after the operation. The data show that total occlusion of the left main coronary artery is compatible with survival if adequate collateral supply develops from the right coronary artery. In this rare angiographic subset collateral circulation is clearly functionally significant.  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