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   4880篇
  免费   223篇
  国内免费   15篇
耳鼻咽喉   59篇
儿科学   101篇
妇产科学   74篇
基础医学   586篇
口腔科学   81篇
临床医学   368篇
内科学   1329篇
皮肤病学   100篇
神经病学   270篇
特种医学   173篇
外科学   752篇
综合类   41篇
预防医学   171篇
眼科学   57篇
药学   345篇
中国医学   8篇
肿瘤学   603篇
  2023年   24篇
  2022年   28篇
  2021年   96篇
  2020年   37篇
  2019年   43篇
  2018年   51篇
  2017年   39篇
  2016年   40篇
  2015年   46篇
  2014年   65篇
  2013年   107篇
  2012年   165篇
  2011年   164篇
  2010年   114篇
  2009年   126篇
  2008年   189篇
  2007年   251篇
  2006年   219篇
  2005年   214篇
  2004年   190篇
  2003年   184篇
  2002年   199篇
  2001年   182篇
  2000年   210篇
  1999年   207篇
  1998年   79篇
  1997年   81篇
  1996年   64篇
  1995年   53篇
  1994年   38篇
  1993年   34篇
  1992年   146篇
  1991年   151篇
  1990年   144篇
  1989年   135篇
  1988年   126篇
  1987年   108篇
  1986年   96篇
  1985年   100篇
  1984年   73篇
  1983年   59篇
  1981年   27篇
  1980年   23篇
  1979年   62篇
  1978年   31篇
  1977年   35篇
  1974年   45篇
  1971年   23篇
  1969年   22篇
  1968年   22篇
排序方式: 共有5118条查询结果,搜索用时 979 毫秒
61.
The effects of diazepam on the crossed extensor reflex (CER) were compared between intact and spinally transected rats and also between IVth and lateral ventricular administration. The CER of the chronic spinal rat was not influenced by 0.05-2 mg/kg doses of diazepam, which was 5-200 times larger than the ED50 of the intact preparation. The IVth ventricular injection required only half as much diazepam compared to the lateral ventricular injection and the elapsed time between drug administration to the peak effect was significantly shorter. According to these findings, benzodiazepines seem to act primarily on the supraspinal structure near the IVth ventricle and thus depress the CER.  相似文献   
62.
The earliest morphological evidence of altered growth potential of pancreatic acinar cells of the rats treated with carcinogen, such as azaserine, is the development of nodules of atypical acinar cells, some of which are considered to appear, eventually, as acinar cell carcinomas. On the other hand, there exist nodular lesions in the human pancreas, which are similar to atypical acinar cell nodules of the rats, in the sense of nodularity, multiplicity, size, and cytological features, such as pale cytoplasm. To clarify the plausibility of the human nodular lesions as a precursor of acinar cell carcinoma of the pancreas, light and electron microscopical studies were performed, using pancreases of 115 semi-consecutive series of autopsy cases and 20 surgical cases. Multiple nodular lesions were found in 3 autopsy cases and one surgical cases. Ultrastructurally, markedly dilated cysterna of rough-surfaced endoplasmic reticulum and intracisternal granules were the most prominent characteristics of the atypical cells of the nodules. These features are neither reported in chemically induced atypical acinar cell nodules and carcinomas nor in human acinar cell carcinomas. The human lesions were considered to be of degenerative nature rather than neoplastic.  相似文献   
63.
64.
Sputum cytology was performed in 179 cases of squamous-cell carcinoma of the lung; 134 cases were diagnosed as positive. There were no significant differences in diagnostic accuracy of sputum cytology between tumors sizes. In cases with tumors extending proximally into the main, lobar, or segmental bronchi, the diagnostic accuracy of sputum cytology was significantly higher than in cases where the proximal invasion of tumor was limited to the peripheral bronchi. In cases with tumors 3 cm or less in diameter, when tumors extended proximally into main, lobar, or segmental bronchi, the diagnostic accuracy of sputum cytology was significantly higher than in cases with tumors extending proximally into subsegmental or subsubsegmental bronchi. In peripherally located squamous-cell carcinoma, in cases in which the tumor arose in subsegmental or subsubsegmental bronchi, carcinoma could be detected by sputum cytology even when it was roentgenographically occult.  相似文献   
65.
F1 cynomolgus monkeys bred in captivity and thought to be "SPF" had latent cytomegalovirus (CMV) infection although less frequently than in wild-born monkeys. Latent CMV could be activated under severe immunosuppression by inoculation with a certain strain of varicella-zoster virus (VZV) as shown in a previous study. We carried out further experiments using live and formalin-inactivated VZV in F1 monkeys which were sero-positive for CMV, but not for any other viruses. The results showed that both live and inactivated VZV were equivalent in permitting activation of latent CMV, suggesting that the VZV inoculum merely played an immunogenic, but not any virological, role in this case. Captive F1 monkeys, however, carried fewer CMV, and/or resisted CMV reactivation more than the wild monkeys in the previous studies, judging from the time required for generalized CMV infection to become expressed.  相似文献   
66.
BACKGROUND: Correcting Th1/Th2 imbalance with administration of IL-12 before and during antigen challenge holds therapeutic promise in asthma. However, the effects of IL-12 on the established asthmatic responses have not fully been examined. OBJECTIVE: We investigated whether IL-12 administered after antigen challenge could diminish airway hyper-reactivity (AHR) and eosinophilia in mice actively sensitized to ovalbumin. We also have investigated the ability of administered IL-12 to induce IL-18 receptor (IL-18R) expression that may lead possible synergic action of IL-12 with endogenous IL-18. METHODS: C57BL/6 mice immunized to ovalbumin (OVA) by intraperitoneal (i.p.) injection, were challenged three times with an aerosol of OVA every second day for 8 days. Recombinant IL-12 (500 ng) was intravenously administered on a single occasion 1 h after the final challenge of mice. Mice were analysed for effects of IL-12 on AHR, inflammatory cell infiltration and cytokine levels in lung tissue as well as serum immunoglobulin (Ig) E levels. Immunohistochemistry for IL-18R was performed using rat monoclonal antibody specific for murine IL-18Ralpha (IL-1 receptor related protein; IL-1Rrp). RESULTS: An intravenous IL-12 administration diminished AHR, pulmonary eosinophilia and T lymphocyte infiltration, serum IgE, IL-4 and IL-13 in lung tissue. Expression of IL-18R was induced in the mononuclear cells in the lung of mice exposed to OVA. IL-12 administration enhanced the IL-18R expression compared with the control. CONCLUSION: These data indicate that IL-12 can attenuate established antigen-induced AHR and inflammation. In this mechanism it would be interpreted as follows: IL-12 administration in OVA-challenged mice decreased IL-4 production and IgE production thereafter through direct effect on inhibiting the activation of established Th2 cells response and also combined effect with up-regulation of IL-18R expression by inflammatory cells in the lung.  相似文献   
67.
68.
We evaluated a new immunoblot assay (Helicoblot 2.1) for Helicobacter pylori infection and CagA and VacA status by using serum samples from 222 patients. The test accurately detected H. pylori infection and VacA status, but improvements in the interpretation criteria are required before it can be recommended for determination of CagA status.  相似文献   
69.
Thromboplastic and fibrinolytic activities of V2 and V7 carcinomas, the two transplantable rabbit tumors of the same viral origin, were studied in relation to fibrin deposition and thrombus formation in the tumors. Thromboplastic activity of V7 carcinoma was comparatively high, while that of V2 carcinoma was as low as that of muscle tissue. More fibrin deposits in the stroma and more thrombi in the small vessels were found at the advancing border of V7 carcinoma than that of V2 carcinoma. These differences might be associated with higher thromboplastic activity of V7 carcinoma than that of V2 carcinoma. Fibrinolytic activity of both tumors was high and it was confirmed to be localized in the tumor cells by Todd's method. Fibrin deposits in the stroma were found more abundantly somewhat apart from the advancing border of the tumor nests of both tumors. It was suggested that plasmin activated by plasminogen activator released locally from the tumor cells might digest fibrin deposited in the stroma just close to the tumor nests.  相似文献   
70.
Running-wheel activity for 24 hr and activity patterns were studied during chronic theophylline administration. Theophylline altered the normal relations between activity level and illumination. Dark-time activity was decreased to approximately 50% and 24 hr activity was unaffected. These observations were consistent with previous results showing that theophylline suppressed dark-time feeding but had no effect on 24 hr food intake. A possible mechanism to account for these results may be dependent on levels and turnover of brain norepinephrine.  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