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   6207篇
  免费   322篇
  国内免费   40篇
耳鼻咽喉   35篇
儿科学   133篇
妇产科学   82篇
基础医学   1298篇
口腔科学   131篇
临床医学   323篇
内科学   685篇
皮肤病学   35篇
神经病学   1379篇
特种医学   53篇
外科学   251篇
综合类   198篇
现状与发展   1篇
一般理论   1篇
预防医学   716篇
眼科学   32篇
药学   987篇
中国医学   58篇
肿瘤学   171篇
  2023年   65篇
  2022年   90篇
  2021年   175篇
  2020年   175篇
  2019年   267篇
  2018年   191篇
  2017年   153篇
  2016年   136篇
  2015年   163篇
  2014年   260篇
  2013年   390篇
  2012年   262篇
  2011年   333篇
  2010年   264篇
  2009年   308篇
  2008年   265篇
  2007年   268篇
  2006年   253篇
  2005年   195篇
  2004年   164篇
  2003年   155篇
  2002年   136篇
  2001年   99篇
  2000年   100篇
  1999年   62篇
  1998年   80篇
  1997年   68篇
  1996年   60篇
  1995年   47篇
  1994年   35篇
  1993年   46篇
  1992年   50篇
  1991年   44篇
  1990年   35篇
  1988年   38篇
  1987年   32篇
  1986年   48篇
  1985年   113篇
  1984年   132篇
  1983年   102篇
  1982年   102篇
  1981年   89篇
  1980年   86篇
  1979年   80篇
  1978年   47篇
  1977年   55篇
  1976年   38篇
  1975年   38篇
  1974年   36篇
  1973年   39篇
排序方式: 共有6569条查询结果,搜索用时 31 毫秒
91.
The assumption that drugs used as unconditioned stimuli in conditioned taste aversion (CTA) studies act centrally was tested by comparing the effects of systemic and intracerebral injections of harmaline hydrochloride (H) in 340 rats. Intraperitoneal injection of 5–20 mg/kg but not of 2.5 mg/kg H administered 5 min after 15-min saccharin (0.1%) drinking decreased saccharin-water preference in a two-choice retention test, performed 48 h later, from 55% to 20%. Since CTA was not diminished when H (10 mg/kg) was injected into rats anesthetised immediately after saccharin drinking by pentobarbital (40 mg/kg), H (1.7–50 g) was administered intracerebrally to anesthetised rats fixed in the stereotaxic apparatus. Injection of 3–6 g H into the inferior olive elicited CTA comparable to that of systemic injection of 10 mg/kg H. Injections of 6 and 50 g H into cerebellum and bulbar reticular formation elicited weaker CTA while neocortical, hypothalamic and mesencephalic applications were ineffective. CTA could also be elicited when 50 g but not 6 g H was injected into the inferior olive 1 or 2 h after saccharin drinking. This delay-dependent effect and failure of non-contingent H administration to change saccharin preference indicates that the H-induced CTA is not contaminated by a non-specific increase in neophobia. It is concluded that H probably elicits CTA by activation of caudal bulbar structures, including the nucleus of the solitary tract, area postrema and lateral reticular formation.  相似文献   
92.
Eating behaviors are influenced by the reinforcing properties of foods that can favor decisions driven by reward incentives over metabolic needs. These food reward-motivated behaviors are modulated by gut-derived peptides such as ghrelin and glucagon-like peptide-1 (GLP-1) that are well-established to promote or reduce energy intake, respectively. In this review we highlight the antagonizing actions of ghrelin and GLP-1 on various behavioral constructs related to food reward/reinforcement, including reactivity to food cues, conditioned meal anticipation, effort-based food-motivated behaviors, and flavor-nutrient preference and aversion learning. We integrate physiological and behavioral neuroscience studies conducted in both rodents and human to illustrate translational findings of interest for the treatment of obesity or metabolic impairments. Collectively, the literature discussed herein highlights a model where ghrelin and GLP-1 regulate food reward-motivated behaviors via both competing and independent neurobiological and behavioral mechanisms.  相似文献   
93.
将2000~2019年20起我国境内医院空调系统火灾数据进行统计并分析火灾的时间、起火医院的类型和等级、起火部位和点位的特点及产生的原因,希望给同行一些警示。  相似文献   
94.
95.
The uptake of contralateral prophylactic mastectomy (CPM) has increased steadily over the last twenty years in women of all age groups and breast cancer stages. Since contralateral breast cancer is relatively rare and the breast cancer guidelines only recommend CPM in a small subset of patients with breast cancer, the drivers of this trend are unknown. This review aims to evaluate the evidence for and acceptability of CPM, data on patient rationales for choosing CPM, and some of the factors that might impact patient preferences. Based on the evidence, future recommendations will be provided. First, data on contralateral breast cancer risk and CPM rates and trends are addressed. After that, the evidence is structured around four main patient rationales for CPM formulated as questions that patients might ask their surgeon: Will CPM reduce mortality risk? Will CPM reduce the risk of contralateral breast cancer? Can I avoid future screening with CPM? Will I have better breast symmetry after CPM? Also, three different guidelines regarding CPM will be reviewed. Studies indicate a large gap between patient preferences for radical risk reduction with CPM and the current approaches recommended by important guidelines. We suggest a strategy including shared decision-making to enhance surgeons’ communication with patients about contralateral breast cancer and treatment options, to empower patients in order to optimize the use of CPM incorporating accurate risk assessment and individual patient preferences.  相似文献   
96.
97.
目的 以黄背草Themeda japonica为试验材料,比较分析其与阿拉伯黄背草T. triandra、中华菅T. quadrivalvis2种同属植物的叶绿体基因组特征及其与近缘物种的系统发育关系。方法 采用Illumina HiSeq高通量测序平台首次对黄背草叶绿体基因组进行测序,使用SPAdes和CpGAVAS2分别对其进行组装和注释,并用Codon W、DnaSP和MISA等对其与2种同属植物进行一系列比较基因组分析,利用最大似然法(maximum likelihood,ML)构建系统进化树。结果 3个叶绿体基因组全长为138 735~138 961 bp,具有典型的四分体结构,共注释出129个基因;黄背草与其同属的2个物种相比,反向重复区(inverted repeats,IR)收缩了2132 bp,大单拷贝区(large single copy region,LSC)扩张了约4000 bp,而小单拷贝区(small single copy region,SSC)变化不大。密码子偏好性分析显示,3个叶绿体基因组相对丰度最大和最小的密码子都相同,同义密码子相对使用丰度略有不同...  相似文献   
98.
孙越鹏  王梦雪  宋丹  耿磊 《中草药》2023,54(24):8077-8085
目的 建立一测多评(quantitative analysis of multicomponents by single-marker,QAMS)法同时检测盐沙苑子饮片中杨梅素、扁蓄苷、杨梅素-3-O-β-D-葡萄糖苷、毛蕊异黄酮葡萄糖苷、西伯利亚落叶松黄酮、沙苑子苷B、沙苑子苷A、毛蕊异黄酮、芒柄花素、鼠李柠檬素、豆甾醇、胡萝卜苷、β-谷甾醇含量的方法,并采用主成分分析法(principal component analysis,PCA)、正交偏最小二乘法-判别分析(orthogonal partial least squares-discriminant analysis,OPLS-DA)法及熵权逼近理想解排序(entropy weight-technique for order preference by similarity to ideal solution,EW-TOPSIS)法对其质量进行评价。方法 采用Lichrospher C18色谱柱;乙腈-0.2%磷酸水溶液为流动相梯度洗脱。以沙苑子苷A为内参物,建立内参物与其他12个待测成分的相对校正因子(relative co...  相似文献   
99.
Are androgens reinforcing? Androgenic-anabolic steroids (AAS) are drugs of abuse. They are taken in large quantities by athletes and others to increase performance, often with negative long-term health consequences. As a result, in 1991, testosterone was declared a controlled substance. Recently, Brower [K.J. Brower, Anabolic steroid abuse and dependence. Curr. Psychiatry Rep. 4 (2002) 377-387.] proposed a two-stage model of AAS dependence. Users initiate steroid use for their anabolic effects on muscle growth. With continued exposure, dependence on the psychoactive effects of AAS develops. However, it is difficult in humans to separate direct psychoactive effects of AAS from the user's psychological dependence on the anabolic effects of AAS. Thus, studies in laboratory animals are useful to explore androgen reinforcement. Testosterone induces a conditioned place preference in rats and mice, and is voluntarily consumed through oral, intravenous, and intracerebroventricular self-administration in hamsters. Active, gonad-intact male and female hamsters will deliver 1 microg/microl testosterone into the lateral ventricles. Indeed, some individuals self-administer testosterone intracerebroventricularly to the point of death. Male rats develop a conditioned place preference to testosterone injections into the nucleus accumbens, an effect blocked by dopamine receptor antagonists. These data suggest that androgen reinforcement is mediated by the brain. Moreover, testosterone appears to act through the mesolimbic dopamine system, a common substrate for drugs of abuse. Nonetheless, androgen reinforcement is not comparable to that of cocaine or heroin. Instead, testosterone resembles other mild reinforcers, such as caffeine, nicotine, or benzodiazepines. The potential for androgen addiction remains to be determined.  相似文献   
100.
目的:利用一种改进的三箱社交装置评价动物的社交偏好程度,并探索该方法的可行性。方法:采用注意力缺陷多动障碍(ADHD)大鼠作为社交障碍模型动物,以同源大鼠(WKY)大鼠和Wistar大鼠作为对照组,模型组采用治疗ADHD的临床常用中成药小儿黄龙颗粒(1.88 g/kg、3.75 g/kg)灌胃给药16 d。利用改进的三箱社交箱,以待测鼠在陌生鼠侧密切交流区的时间、频次、路程及相关比例作为行为学指标,检测该方法对社交行为评价的可行性。结果:与Wistar大鼠组比较,模型组大鼠与WKY组大鼠在密切交流区域及有陌生鼠侧区域的时间显著减少(P<0.01),其他指标如频次、路程及比例也均有不同程度减少,小儿黄龙颗粒两剂量均能增加模型大鼠上述各指标数值。结论:该方法能准确捕捉动物的社交行为特征,实现对动物社交偏好程度的全面、客观评价。  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