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   4071篇
  免费   228篇
  国内免费   50篇
耳鼻咽喉   8篇
儿科学   112篇
妇产科学   27篇
基础医学   583篇
口腔科学   87篇
临床医学   261篇
内科学   1165篇
皮肤病学   22篇
神经病学   252篇
特种医学   180篇
外科学   749篇
综合类   19篇
预防医学   80篇
眼科学   23篇
药学   221篇
中国医学   6篇
肿瘤学   554篇
  2023年   37篇
  2022年   68篇
  2021年   135篇
  2020年   65篇
  2019年   76篇
  2018年   142篇
  2017年   88篇
  2016年   115篇
  2015年   129篇
  2014年   164篇
  2013年   183篇
  2012年   351篇
  2011年   352篇
  2010年   174篇
  2009年   158篇
  2008年   256篇
  2007年   289篇
  2006年   268篇
  2005年   215篇
  2004年   225篇
  2003年   237篇
  2002年   194篇
  2001年   35篇
  2000年   34篇
  1999年   42篇
  1998年   52篇
  1997年   35篇
  1996年   34篇
  1995年   31篇
  1994年   19篇
  1993年   26篇
  1992年   31篇
  1991年   11篇
  1990年   13篇
  1989年   8篇
  1988年   11篇
  1987年   14篇
  1986年   3篇
  1985年   5篇
  1984年   6篇
  1983年   2篇
  1982年   2篇
  1980年   1篇
  1979年   2篇
  1977年   2篇
  1975年   2篇
  1972年   1篇
  1971年   1篇
  1970年   2篇
  1967年   1篇
排序方式: 共有4349条查询结果,搜索用时 15 毫秒
81.
Many chemicals released into the environment have the capacity to disrupt the normal development of aquatic animals. We investigated the influence of nonylphenol (NP), bisphenol-A (BPA), and 17beta-estradiol (E2) on developing Xenopus laevis embryos, as a model animal in the aquatic environment. Embryos were exposed to eight different concentrations of NP, BPA or E2 between 3 and 96 h post-fertilization (p.f.). Short body length, microcephaly, flexure, edema, and abnormal gut coiling were induced by 20 microM NP, BPA or 10 microM E2 by 96 h p.f. To clarify sensitive stages to these compounds, embryos were exposed to chemicals for 45 or 48 h starting at different developmental stages and experiments were terminated 96 h p.f. BPA and NP induced abnormalities in developing X. laevis, though the sensitive stages of embryos to these chemicals are different, BPA affecting earlier stages and NP affecting at later stages. To analyze the functional mechanisms of BPA and NP in induction of morphological changes, we adapted a DNA array technology and identified 6 X. laevis genes, XIRG, alpha skeletal tropomyosin, cyclin G1, HGF, troponin C2, and ribosomal protein L9. These findings may provide important clues to elucidate common mechanisms underlying teratogenic effects of these chemicals.  相似文献   
82.
The aim of the study described here was to clarify the diagnostic value of the fluttering sign, a new sign that characterizes hepatic hemangiomas in gray-scale ultrasonography (US). It refers to a phenomenon in which the speckled echogenicity inside the hemangioma changes continuously and seems to be moving. A total of 172 hemangiomas diagnosed with contrast-enhanced US were evaluated. The fluttering sign was found in 123 of 172 hemangiomas (71.5%). Its prevalence was significantly higher than that of the marginal strong echo (89/172, 51.7%, p < 0.001), posterior acoustic enhancement (103/172, 59.9%, p = 0.031) and chameleon sign (100/172, 58.1%, p = 0.013). In addition, the fluttering sign was observed significantly more frequently in mixed or hypo-echoic tumors than in hyper-echoic tumors (p < 0.001), relatively large tumors (p < 0.001) and tumors that were less than 5 cm from the body surface (p = 0.015). The fluttering sign in gray-scale US has great potential to be a new complementary sign for the diagnosis of hemangioma.  相似文献   
83.
84.
85.
86.
Annals of Nuclear Medicine - Albumin–globulin ratio (AGR), which is calculated by dividing serum albumin by serum globulin, is considered as a cancer-related inflammation biomarker. Although...  相似文献   
87.
The optimization of photorefractivity (PR) based on a poly(N‐vinylcarbazole) (PVCz) composite devise is proposed from the perspectives of chemistry and physics. The device's PR chemistry (dependence of PVCz's molecular weight) and physics (dependence of grating periodicity and laser wavelength) are studied. Increasing the molecular weight of PVCz from 23 000 to 1 270 000 g mol?1 significantly increases diffraction efficiency, grating build‐up speed (inverse of response time), and sensitivity. Narrowing grating period from 5.1 to 1.1 μm gives faster response time and larger optical gain. Shorter wavelength of writing laser from 633 to 532 nm provides higher diffraction efficiency, faster response time, and larger optical gain.

  相似文献   

88.
Chromophobe renal cell carcinoma (RCC) accounts for approximately 5% of renal epithelial neoplasms. Multiple and/or bilateral chromophobe RCCs in an individual are generally rare but frequently occur in patients with Birt–Hogg–Dubé syndrome (BHDS) and in patients with tuberous sclerosis complex (TSC). The responsible genes in both BHDS and TSC act as tumor suppressors. Therefore, it seems that some genetic backgrounds are required for the generation and progression of multiple chromophobe RCCs. Here, we report a case of multiple and bilateral chromophobe RCCs along with several small‐sized capsular angiomyolipomas known as ‘capsulomas’ in a 39‐year‐old woman who had neither a particular medical history nor specific gene mutation. There has been no report of sporadic multiple chromophobe RCCs and ‘capsulomas’ developing in a patient without genetic features, having potential for novel genetic variation.  相似文献   
89.
Background: Host effector mechanism against Mycobacterium tuberculosis (Mtb) infection is dependent on innate immune response by macrophages and neutrophils and the alterations in balanced adaptive immunity. Coordinated release of cytolytic effector molecules from NK cells and effector T cells and the subsequent granule-associated killing of infected cells have been documented; however, their role in clinical tuberculosis (TB) is still controversy.Objective: To investigate whether circulating granulysin and other effector molecules are associated with the number of NK cells, iNKT cells, Vγ9+Vδ2+ T cells, CD4+ T cells and CD8+ T cells, and such association influences the clinical outcome of the disease in patients with pulmonary TB and HIV/TB coinfection.Methods: Circulating granulysin, perforin, granzyme-B and IFN-γ levels were determined by ELISA. The isoforms of granulysin were analyzed by Western blot analysis. The effector cells were analyzed by flow cytometry.Results: Circulating granulysin and perforin levels in TB patients were lower than healthy controls, whereas the granulysin levels in HIV/TB coinfection were much higher than in any other groups, TB and HIV with or without receiving HAART, which corresponded to the number of CD8+ T cells which kept high, but not with NK cells and other possible cellular sources of granulysin. In addition, the 17kDa, 15kDa and 9kDa isoforms of granulysin were recognized in plasma of HIV/TB coinfection. Increased granulysin and decreased IFN-γ levels in HIV/TB coinfection and TB after completion of anti-TB therapy were observed.Conclusion: The results suggested that the alteration of circulating granulysin has potential function in host immune response against TB and HIV/TB coinfection. This is the first demonstration so far of granulysin in HIV/TB coinfection.  相似文献   
90.
Journal of Natural Medicines - The lycopene content of tomatoes is important because of its effects on vital physiological functions such as improvement of glucose tolerance and non-alcoholic fatty...  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