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   20488篇
  免费   1383篇
  国内免费   287篇
耳鼻咽喉   43篇
儿科学   515篇
妇产科学   206篇
基础医学   3687篇
口腔科学   368篇
临床医学   2083篇
内科学   1539篇
皮肤病学   150篇
神经病学   3993篇
特种医学   197篇
外国民族医学   1篇
外科学   520篇
综合类   1864篇
一般理论   1篇
预防医学   4052篇
眼科学   37篇
药学   2355篇
  8篇
中国医学   229篇
肿瘤学   310篇
  2023年   276篇
  2022年   458篇
  2021年   956篇
  2020年   722篇
  2019年   600篇
  2018年   543篇
  2017年   630篇
  2016年   681篇
  2015年   656篇
  2014年   1173篇
  2013年   1613篇
  2012年   1024篇
  2011年   1193篇
  2010年   838篇
  2009年   896篇
  2008年   932篇
  2007年   891篇
  2006年   844篇
  2005年   676篇
  2004年   552篇
  2003年   520篇
  2002年   457篇
  2001年   351篇
  2000年   275篇
  1999年   260篇
  1998年   216篇
  1997年   201篇
  1996年   173篇
  1995年   167篇
  1994年   148篇
  1993年   130篇
  1992年   141篇
  1991年   133篇
  1990年   114篇
  1989年   120篇
  1988年   124篇
  1987年   100篇
  1986年   151篇
  1985年   250篇
  1984年   245篇
  1983年   176篇
  1982年   217篇
  1981年   200篇
  1980年   199篇
  1979年   187篇
  1978年   129篇
  1977年   143篇
  1976年   130篇
  1975年   95篇
  1973年   77篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Tracer experiments were carried out to compare the plant uptake behavior of Tc and Re from nutrient solutions. Radish plants, transplanted to nutrient solution including various tracers, showed the same uptake and distribution of 95mTc and 183Re. The trend was the same when the 99Tc and stable-Re concentrations were increased in nutrient solution. The behavior of other elements was different from that of Tc and Re. These findings suggest the possible use of Re as the chemical analogue of Tc in soil solution to plant uptake experiments.  相似文献   
92.
胃类癌生物学行为及与预后关系的临床研究   总被引:1,自引:0,他引:1  
目的分析胃类癌特有的生物学行为与肿瘤预后之间的关系。方法总结1964年1月至2005年1月间收治的26例经手术切除、病理证实的胃类癌病例资料,对其肿瘤大小、胃壁侵犯深度、区域淋巴结转移、肝转移、术后辅助化疗和5年生存率进行分析。结果本组患者平均年龄58岁。其中18例(69.2%)肿瘤侵犯胃浆膜;12例(46.2%)有区域淋巴结转移;10例(38.5%)术后接受辅助化疗;14例(53.8%)在随访中出现肝转移。肿瘤大小与胃壁侵犯深度、区域淋巴结转移和肝转移的发生及5年生存率无关(P>0.05)。生存分析提示浆膜浸润、淋巴结转移和肝转移影响生存时间(P<0.05)。有浆膜浸润、淋巴结转移和肝转移的患者5年生存率分别为16.7%、16.7%和0,预后较差;化疗与否5年生存率比较,差异无统计学意义(P<0.05)。结论胃类癌术后辅助化疗并无益处,其预后与肿瘤的浸润深度、淋巴结转移和肝转移有关。  相似文献   
93.
The objective of this study was to use the Lille Apathy Rating Scale to assess apathy in a large population of Parkinson's disease (PD) patients and identify several different apathy profiles. One hundred fifty-nine patients with probable PD and 58 healthy controls participated in the study. Apathy was assessed using the Lille Apathy Rating Scale. Motor, cognitive, and depressive symptoms were rated on standardized scales. Data were analyzed using linear regression and multivariate analyses of variance. Thirty-two percent of the PD patients were classified as apathetic. Apathy was more frequent in patients with dementia. The four apathy dimensions contributed differently to the overall severity of the apathetic condition. Action initiation and intellectual curiosity had a marked influence. Linear regression analysis revealed that the apathy level was mainly determined by cognitive impairment, not associated with the severity of motor symptoms, and only associated with the apathy subcomponent of the Montgomery and Asberg Depression Rating Scale. Apathy is highly prevalent in PD patients. Apathy profiles vary according to the clinical presentation of PD. The high prevalence of apathy in PD suggests the involvement of frontal-subcortical circuits. Although the neurochemical substrate of apathy remains poorly characterized, the strong link between apathy and cognitive impairment observed in several studies suggests the participation of nondopaminergic circuits.  相似文献   
94.
95.
There is accumulating evidence, reviewed by Caudiano (this issue), that cognitive behavior therapy (CBT) is an effective adjunct treatment for schizophrenia. Schizophrenia treatment and research provides a range of challenges that are probably not present in other mental health problems. These include contextual issues, clinical issues, scientific and methodological issues, practical and pragmatic issues, public concern, and human rights issues. This paper discusses these issues with emphasis on the clinical and research challenges for the future.  相似文献   
96.
大鼠红核和颈段皮质脊髓背侧束联合损伤模型的建立   总被引:3,自引:0,他引:3  
目的 为研究脊髓损伤后的可塑性变化 ,建立大鼠红核和皮质脊髓背侧束 (dCST)联合损伤模型。方法 立体定位仪下 ,致伤颈 3dCST和双侧红核 ,甲苯胺蓝染色显示损伤范围。示踪剂观测皮质脊髓腹侧束 (vCST)的出芽情况 ;同时 ,评定大鼠前肢功能的变化情况。结果 精确地致伤红核和dCST后 ,vCST的出芽数量和大鼠前肢功能评分成显著负相关 (P <0 0 1)。结论 大鼠红核和dCST联合损伤模型是研究脊髓损伤后可塑性变化的良好模型  相似文献   
97.
低温保存动脉的粘弹性力学评价指标的初步建立   总被引:1,自引:0,他引:1  
目的 建立低温保存动脉的粘弹性力学评价指标.方法 使用动态力学分析仪(DMA-2980, TA Instruments, New Castle, Delaware, USA) 比较研究不同低温保存方案下动脉蠕变行为与新鲜对照组的差异.结果 低温保存动脉相对新鲜对照组而言,其粘弹性均有损失;随降温速率的增加(1.5, 5, 10℃/min),其粘弹性损失趋于增加,即1.5℃/min 为本研究中最佳降温速率.结论 粘弹性力学性能是低温保存动脉的潜在的重要评价指标.  相似文献   
98.
Effects of daily administrations of d-amphetamine were studied on key peck responses of pigeons maintained under a multiple fixed-interval 2-min, fixed-ratio 30-responseschedule. Under the fixed-interval schedule, a pause was followed by a transition to increasing rates of responding until food presentation. Under the fixed-ratio schedule, higher sustained rates of responding were maintained. Low to intermediate doses (0.3-1.0 mg/kg) of d-amphetamine changed the temporal patterns and occasionally increased rates of responding under the fixed-interval schedule. Higher doses decreased rates of responding under bothschedules. With daily injections of 1.0 mg/kg d-amphetamine prior to experimental sessions, the effects of this dose on rates and patterns of responding were attenuated, and d-anphetamine dose-effect curves were shifted to the right, primarily under the fixed-ratio schedule. Similar results were obtained with daily presession injections of 5.6 mg/kg d-amphetamine in a second group of pigeons, except that rates of responding under both schedules were decreased by this daily dose, and did not return completely to control values with repeated injections. In a third group of pigeons, 1.0 mg/kg d-amphetamine administered daily, after experimental sessions, did not alter dose-effect functions for d-amphetamine. In a second experiment, pigeons were trained to peck one response key when given 1.0 mg/kg d-amphetamine and a different key when given presession water injections. Increasing doses of d-amphetamine produced incresing percentages of d-amphetamine-key responses. Repeated administration of 5.6 mg/kg d-amphetamine shifted these dose-effect functions to the right one-half log unit. Results suggested that decreases in reinforcement frequency are not a necessary condition for the development of behavioral tolerance to d-amphetamine.  相似文献   
99.
Contralateral intrastriatal injection of 0.1 pmol or 1 pmol of endothelin-1 produced ipsilateral turning behaviour in rats with unilateral 6-hydroxydopamine (6-OHDA) lesions of the nigrostriatal pathway. This effect could be abolished by pretreatment with either the endothelinETA/B receptor antagonist bosentan (1 nmol, intrastriatally) or the dopamine D2 receptor antagonist raclopride (0.1 mg/kg, s.c.) suggesting that endothelin is acting at endothelin receptors to evoke ipsilateral turning behaviour and that this response is mediated by dopamine. Similar ipsilateral turning behaviour was observed upon intrastriatal injection of 1 pmol of endothelin-3 or the specific ETB receptor agonist, [Ala1,3,11,15]endothelin-1 when compared to endothelin-1. Pretreatment with the specific ETB receptor antagonist BQ788 blocked the ipsilateral turning response to intrastriatal injection of endothelin-1 while pretreatment with the specific ETA receptor antagonist BQ123 did not significantly change the response to injection of endothelin-1. This indicates that endothelin-1, which has affinity for both ETA and ETB receptors, is most likely acting at the ETB receptor to elicit its effect. These results suggest that low doses of endothelin may act at ETB receptors to evoke the release of dopamine from the striatum in vivo.  相似文献   
100.
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