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   1944篇
  免费   145篇
  国内免费   9篇
耳鼻咽喉   20篇
儿科学   53篇
妇产科学   29篇
基础医学   345篇
口腔科学   17篇
临床医学   201篇
内科学   367篇
皮肤病学   32篇
神经病学   86篇
特种医学   129篇
外科学   221篇
综合类   57篇
一般理论   1篇
预防医学   136篇
眼科学   174篇
药学   110篇
肿瘤学   120篇
  2021年   20篇
  2020年   12篇
  2019年   21篇
  2018年   35篇
  2017年   24篇
  2016年   16篇
  2015年   25篇
  2014年   31篇
  2013年   61篇
  2012年   79篇
  2011年   73篇
  2010年   69篇
  2009年   63篇
  2008年   58篇
  2007年   79篇
  2006年   78篇
  2005年   83篇
  2004年   116篇
  2003年   85篇
  2002年   67篇
  2001年   78篇
  2000年   71篇
  1999年   62篇
  1998年   44篇
  1997年   31篇
  1996年   38篇
  1995年   42篇
  1994年   22篇
  1993年   15篇
  1992年   36篇
  1991年   18篇
  1990年   26篇
  1989年   49篇
  1988年   33篇
  1987年   43篇
  1986年   33篇
  1985年   29篇
  1984年   36篇
  1983年   31篇
  1982年   20篇
  1981年   32篇
  1980年   22篇
  1979年   27篇
  1978年   13篇
  1977年   14篇
  1976年   12篇
  1975年   13篇
  1974年   14篇
  1969年   9篇
  1966年   14篇
排序方式: 共有2098条查询结果,搜索用时 218 毫秒
51.
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   
52.
The British HIV Association (BHIVA) has published guidelines for immunization of HIV-infected adults. A chart review of 200 HIV-infected patients diagnosed was conducted to determine shortcomings in previous practice and determine which vaccines should routinely be given in specialist HIV clinics and which might be able to be delegated to primary care clinics. Data were collected on administration of three categories of vaccinations: (1) vaccines used in all individuals with chronic disease (pneumococcal, influenza, swine flu H1N1); (2) targeted vaccinations used in non-immune individuals with HIV who are at risk of exposure (hepatitis A and hepatitis B); (3) routine vaccines traditionally delivered to the whole population (measles/mumps/rubella [MMR], diphtheria/tetanus/pertussis and meningitis C/ACWY). Pneumococcal vaccine was delivered to 54% of eligible patients, 52% of eligible individuals completed a full hepatitis B programme of vaccination and 21% (42/200) were naturally immune; hepatitis A vaccine was delivered to 36% of eligible individuals. With increasing demands on resources, it seems likely that HIV services will have to harness resources of primary care in vaccine programmes in relation to routine vaccines. By improving communication between primary and secondary care mistakes with live vaccination decisions could be avoided; HIV services should continue to perform targeted and chronic disease vaccines, i.e. for category 1 and category 2 vaccines.  相似文献   
53.
Clinical trials using kinase inhibitors have demonstrated transient partial responses and disease control in patients with progressive medullary thyroid cancer (MTC). The goal of this study was to identify potential combinatorial strategies to improve on these results using sorafenib, a multikinase inhibitor with activity in MTC, as a base compound to explore signaling that might predict synergystic interactions. Two human MTC cell lines, TT and MZ-CRC-1, which harbor endogenous C634W or M918T RET mutations, respectively, were exposed to sorafenib, everolimus, and AZD6244 alone and in combination. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrasodium bromide (MTT) and poly (ADP-ribose) polymerase (PARP) cleavage assays were performed to measure cell survival and apoptosis. Western blots were performed to confirm activity of the compounds and to determine possible mechanisms of resistance and predictors of synergy. As a solitary agent, sorafenib was the most active compound on MTT assay. Western blots confirmed that sorafenib, everolimus, and AZD6244 inhibited their anticipated targets. At concentrations below its IC(50), sorafenib-treated TT and MZ-CRC-1 cells demonstrated transient inhibition and then re-activation of Erk over 6?h. In concordance, synergistic effects were only identified using sorafenib in combination with the Mek inhibitor AZD6244 (P<0.001 for each cell line). Cells treated with everolimus demonstrated activation of Akt and Ret via TORC2 complex-dependent and TORC2 complex-independent mechanisms respectively. Everolimus was neither additive nor syngergistic in combination with sorafenib or AZD6244. In conclusion, sorafenib combined with a Mek inhibitor demonstrated synergy in MTC cells in vitro. Mechanisms of resistance to everolimus in MTC cells likely involved TORC2-dependent and TORC2-independent pathways.  相似文献   
54.
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   
55.
56.
57.
58.
Phytotoxicity of foliar-applied urea   总被引:5,自引:0,他引:5       下载免费PDF全文
Recent work in our laboratory showed that the adverse effect of urea fertilizer on seed germination and seedling growth in soil is due to ammonia produced through hydrolysis of urea by soil urease (NH2CONH2 + H2O → 2NH3 + CO2) and can be eliminated by amending the fertilizer with a small amount of a urease inhibitor such as phenylphosphorodiamidate. Because the leaf-tip necrosis often observed after foliar fertilization of plants with urea is usually attributed to ammonia formed through hydrolysis of urea by plant urease, we studied the possibility that this necrosis could be eliminated or reduced by adding phenylphosphorodiamidate to the urea fertilizer. We found that, although addition of this urease inhibitor to foliar-applied urea increased the urea content and decreased the ammonia content and urease activity of soybean [Glycine max. (L.) Merr.] leaves fertilized with urea, it increased the leaf-tip necrosis observed after fertilization. We conclude that this necrosis resulted from accumulation of toxic amounts of urea rather than from formation of toxic amounts of ammonia. This conclusion was supported by our finding that the necrotic areas of soybean leaves treated with urea or with urea and phenylphosphorodiamidate contained much higher concentrations of urea than did the nonnecrotic areas.  相似文献   
59.
60.
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