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   56054篇
  免费   5743篇
  国内免费   101篇
耳鼻咽喉   469篇
儿科学   1593篇
妇产科学   1160篇
基础医学   7661篇
口腔科学   1561篇
临床医学   6644篇
内科学   10886篇
皮肤病学   784篇
神经病学   4988篇
特种医学   2068篇
外国民族医学   1篇
外科学   7224篇
综合类   1300篇
一般理论   53篇
预防医学   6410篇
眼科学   1170篇
药学   4639篇
中国医学   102篇
肿瘤学   3185篇
  2021年   715篇
  2020年   432篇
  2019年   791篇
  2018年   932篇
  2017年   668篇
  2016年   759篇
  2015年   880篇
  2014年   1223篇
  2013年   1842篇
  2012年   2647篇
  2011年   2716篇
  2010年   1521篇
  2009年   1477篇
  2008年   2677篇
  2007年   2817篇
  2006年   2746篇
  2005年   2741篇
  2004年   2569篇
  2003年   2498篇
  2002年   2439篇
  2001年   1630篇
  2000年   1521篇
  1999年   1557篇
  1998年   729篇
  1997年   597篇
  1996年   596篇
  1995年   583篇
  1994年   513篇
  1993年   573篇
  1992年   1281篇
  1991年   1186篇
  1990年   1125篇
  1989年   1091篇
  1988年   1022篇
  1987年   1003篇
  1986年   1024篇
  1985年   958篇
  1984年   883篇
  1983年   710篇
  1982年   533篇
  1981年   466篇
  1980年   425篇
  1979年   637篇
  1978年   534篇
  1977年   413篇
  1976年   419篇
  1975年   364篇
  1974年   469篇
  1973年   428篇
  1972年   405篇
排序方式: 共有10000条查询结果,搜索用时 453 毫秒
81.
 The behavioral effects of GBR 12909, a selective dopamine uptake inhibitor, were determined in squirrel monkeys trained to respond under a fixed-interval (FI) schedule of stimulus termination and a second-order schedule of IV drug self-administration. Intermediate doses of GBR 12909 increased FI response rate markedly, and the highest dose decreased response rate below control values. The 5HT uptake inhibitors, alaproclate and fluoxetine, and the 5HT agonist, quipazine, attenuated the behavioral-stimulant effects of GBR 12909, whereas the 5HT2A/2C antagonist, ritanserin, enhanced the behavioral-stimulant effects of the lowest dose. GBR 12909 reliably maintained self-administration, and ritanserin increased response rate maintained by the highest dose. The dopamine agonist, quinpirole, increased FI response rate in only one of three subjects, and ritanserin enhanced the behavioral-stimulant effects of quinpirole in that subject. The dopamine agonist, apomorphine, only decreased FI response rate, and ritanserin did not alter its behavioral effects. The pharmacological profile of GBR 12909 administered alone and in combination with selective 5HT drugs in the present study was similar to that obtained previously with cocaine, further demonstrating that 5HT can reliably modulate the behavioral effects of psychomotor stimulants with prominent dopaminergic actions. Received: 9 July 1996 / Final version: 22 November 1996  相似文献   
82.
83.
The Child and Adolescent Trial for Cardiovascular Health (CATCH) is a multisite intervention research study that builds on significant progress made in school health education research in the 1980s. The study has three phases: Phase I deals with study design, intervention, and measurement development, Phase II involves the main trial in 96 schools in four states, and Phase III focuses on analysis. The intervention program targets third-fifth grade students and focuses on multiple cardiovascular health behaviors, including eating habits, physical activity, and cigarette smoking. Classroom curricula, school environmental change, and family involvement programs are developed for each grade level and behavioral focus. This paper describes Phase II of CATCH with a rationale for cardiovascular health promotion with youth. The process of change that appears to be necessary for school-based health promotion and that will be tested in CATCH are presented as a framework to guide these efforts.  相似文献   
84.
Many prostatectomies are performed on the basis of symptoms alone; 39% of patients referred by their family doctors and 23% of patients who were on waiting lists for prostatectomy of other hospitals, but who had not undergone any urodynamic investigations, were found to be unobstructed on urodynamic criteria. A screening peak urinary flow rate of 12 ml/s or less was associated with urodynamic evidence of obstruction in 95% of cases; 35% of patients with symptoms of outflow obstruction and a flow rate greater than 12 ml/s were also found to be obstructed. One year post-operatively, 84% of patients who were selected for surgery on combined symptomatic and urodynamic criteria were pleased symptomatically with their result. The failure of detrusor instability to resolve following prostatectomy was associated with symptomatic failure of treatment. Residual obstruction was demonstrated in 5 patients who had undergone prostatectomy and were asymptomatic at this time. This study illustrates that objective measures are necessary in the assessment of patients prior to prostatectomy in order to select only patients who are obstructed. The importance of a screening flow rate is emphasised. All patients who underwent surgery had cystometric evidence of obstruction but the symptomatic results of surgery were no better than the results in patients who had been assessed according to non-urodynamic selection criteria. We have thus failed to identify a need for routine cystometry in the pre-operative assessment of these patients. Cystometry does, however, have a role in assessing patients with pre-operative flow rates greater than 12 ml/s and in those who remain symptomatic following prostatectomy.  相似文献   
85.
The American approach to drug control is conditioned by several national characteristics, including fragmentation of the law enforcement system, a 12,000-mile international boundary and a legal system that restricts police authority to search, arrest, detain, eavesdrop and maintain intelligence files. Drug problems in the United States, though, are by all accounts greater than in any other country. Enforcement has traditionally emphasized street-level arrests, investigation of distribution networks, crop eradication and smuggling interdiction. These practices can be shown to produce arrests and seizures, but there is little evidence to show that they reduce drug supply or drug abuse. More contemporary and promising approaches include community policing, problem-oriented policing, financially oriented investigations, increased international co-operation and a renewed emphasis on drug demand reduction. The most pressing needs in law enforcement are (a) improved intelligence-gathering and analysis and (b) research on the illicit drug industry and on the effectiveness of drug control strategies.  相似文献   
86.
The talar beak is a well-described secondary sign of talocalcaneal coalition but is not pathognomonic of the condition and may be seen in other causes of restricted or abnormal subtalar motion. We present an unusual complication of talar beaks in two patients who sustained fractures through their beaks. One of the patients described did not have a talocalcaneal coalition but had developed a beak following a compound fracture dislocation of the ankle joint complicated by infection, a previously undescribed predisposing cause.  相似文献   
87.
This paper was originally developed by Calu Lester, the founder of KWICFAN, which took a novel approach to grass roots AIDS education in the black community. Calu died of AIDS before completing the work and the paper was completed by Larry L. Saxxon, who was both a friend of Calu's and an AIDS program consultant.

The paper presents a critical perspective of black America's response to the AIDS epidemic. The findings are frightening. Denial within the black community, coupled with a lack of support from the agencies responsible for funding AIDS education, has created a potential epidemiological nightmare. IV drug use continues to be a critical problem of frightening magnitude, allowing an efficient vehicle of HIV transmission. Most sadly of all, the social conditions that create and perpetuate the problematic drug abuse patterns still continue in black America. Black people are clearly becoming the new face of AIDS.  相似文献   
88.
A family of P-glycoproteins are overproduced in multidrug-resistant cells derived from the murine macrophage-like line J774.2. To determine whether individual family members are overproduced in response to different drugs, the P-glycoprotein precursors in several independently isolated cell lines, which were selected for resistance to vinblastine or taxol, were compared. Individual cell lines selected with vinblastine overproduced P-glycoprotein precursors of either 120 or 125 kDa. Taxol-selected cell lines overproduced either the 125-kDa precursor or both precursors simultaneously. Two similar but distinct peptide maps for the mature P-glycoproteins were observed. These maps corresponded to each precursor regardless of the drug used for selection. One vinblastine-resistant cell line switched from the 125- to the 120-kDa precursor when grown in increasing concentrations of drug. This change coincided with the overexpression of a distinct subset of mRNA species that code for P-glycoprotein. It is concluded that precursor expression is not drug-specific. These data suggest that individual overproduced P-glycoprotein family members are translated as distinct polypeptides. The results may help to explain the diversity in the multidrug-resistant phenotype.  相似文献   
89.
A case study of multicentric reticulohistiocytosis is presented with extensive immunohistochemical studies of the infiltrate in both paraffin and cryostat sections. These studies showed that the cells are of monocyte/macrophage origin. B- and T-cell gene rearrangement analysis of multicentric reticulohistiocytosis was also performed and showed a germline configuration.  相似文献   
90.
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