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   10031篇
  免费   822篇
  国内免费   36篇
耳鼻咽喉   59篇
儿科学   356篇
妇产科学   241篇
基础医学   1532篇
口腔科学   131篇
临床医学   1233篇
内科学   1945篇
皮肤病学   155篇
神经病学   1232篇
特种医学   156篇
外科学   996篇
综合类   72篇
一般理论   14篇
预防医学   1214篇
眼科学   163篇
药学   690篇
中国医学   18篇
肿瘤学   682篇
  2024年   29篇
  2023年   204篇
  2022年   312篇
  2021年   507篇
  2020年   373篇
  2019年   447篇
  2018年   439篇
  2017年   350篇
  2016年   363篇
  2015年   354篇
  2014年   440篇
  2013年   556篇
  2012年   839篇
  2011年   826篇
  2010年   408篇
  2009年   384篇
  2008年   568篇
  2007年   632篇
  2006年   543篇
  2005年   472篇
  2004年   427篇
  2003年   365篇
  2002年   308篇
  2001年   72篇
  2000年   49篇
  1999年   53篇
  1998年   64篇
  1997年   38篇
  1996年   24篇
  1995年   28篇
  1994年   23篇
  1993年   13篇
  1992年   30篇
  1991年   33篇
  1990年   24篇
  1989年   22篇
  1988年   27篇
  1987年   18篇
  1986年   17篇
  1985年   22篇
  1984年   17篇
  1983年   21篇
  1982年   10篇
  1981年   13篇
  1980年   9篇
  1979年   12篇
  1976年   11篇
  1975年   8篇
  1974年   12篇
  1973年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The aim of this paper is to examine some of the issues that surround food and the environment, particularly conventional and organic agriculture and food distribution, and to look at some of the health implications. It is argued that the links between food, health and the environment are strong. Consumers have the power to have an impact positively or negatively on the environment via their dietary choices. By providing information and advice about the environmental as well as the health impact of food choices, health and nutrition professionals could increase consumers' awareness of such issues.  相似文献   
102.
Development of nitric oxide neurons in the chick embryo retina   总被引:3,自引:0,他引:3  
Nitric oxide (NO) is a gas involved in neurotransmission in the central nervous system (CNS) and in vertebrate retinas. This paper describes five types of nitrergic neurons in developing and adult chick retina using the nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) reaction. Three of them, nitrergic types 1, 2 and 3, were observed in the inner nuclear layer, while nitrergic type 4 was observed in the ganglion cell layer; nitrergic type 5 were the retinal photoreceptors. Cell processes formed four nitrergic networks, which could be observed in the inner plexiform layer (IPL), at sublayers 1, 3a, 3b and 4. Another nitrergic network was observed in the outer plexiform layer (OPL). From hatching, the dendritic branches were completely developed in the IPL and in the OPL, forming the mentioned networks. Current evidence suggests that NO is coexpressed with other neurotransmitters in neurons of the CNS. Double-staining procedures, using NADPHd and 5HT immunohistochemistry in chicken retina, in a sequential or in an alternative manner, did not reveal the coexistence of these two neurotransmitters in the same neurons, but their networks matched in sublayers 1 and 4 of the IPL.  相似文献   
103.
原发性脑出血伴有血栓危险因素的患者治疗比较棘手,如以下病例:老年男性,55岁,因右侧肢体无力入院。既往患有难治陛高血压、Ⅱ型糖尿病、心绞痛及高脂血症。约10年前右侧肢体曾有一次轻微卒中。入院时所服药物为:阿司匹林75mg,1次/日;阿托伐他汀10mg,1次/日;苄氟噻嗪2.5mg,1次/日;雷米普利2.5mg,1次/日;氨氯地平5mg,1次/日;  相似文献   
104.
BACKGROUND AND AIM: Statistical signal detection methods such as proportional reporting ratios (PRRs) detect many drug safety signals when applied to databases of spontaneous suspected adverse drug reactions (ADRs). Impact analysis is a tool that was developed as an aid to prioritisation of such signals. This paper describes a pilot project whereby impact analysis was simultaneously introduced into practice in a regulatory setting and tested in comparison with the existing approach. METHODS: Impact analysis was run on signals detected during a 26-week period from the UK Adverse Drug Reactions On-line Information Tracking (ADROIT) database of spontaneous ADRs that met minimum criteria (PRR>or=3.0, chi2>or=4.0 and >or=3 reported cases) and related to established drugs (i.e. those that have been available for at least 2 years and no longer carry the 'black triangle' symbol). The current method of signal prioritisation (i.e. the collective judgement at a weekly meeting) was initially performed without knowledge of the findings of impact analysis. Subsequently, the meeting was presented with the findings and, where appropriate, given the opportunity to reconsider the judgement made. The categories arising from the two methods were compared and the ultimate action recorded. Inter-observer variation between scientists performing impact analysis was also assessed. RESULTS: Eighty-six separate signals were analysed by impact analysis, of which 5% were categorised as high priority (A), 14% as requiring further information (B), 31% as low priority (C) and 50% as no action required (D). In general, the new method tended to give a higher level of priority to signals than the existing approach. Overall, there was 59% agreement between the impact analysis and the collective judgement at the meetings (kappa statistic=0.30). There was slightly greater agreement between impact analysis and the final action taken (kappa statistic=0.39), indicating that the findings of an impact analysis had an influence on the outcome. Assessment of inter-observer variation demonstrated that the method is repeatable (kappa statistic for overall category=0.77). Almost 70% of those who participated in the pilot study believed that impact analysis represented an improvement in how signals were prioritised. CONCLUSIONS: Impact analysis is a repeatable method of signal prioritisation that tended to give a higher level of priority to signals than the standard approach and which had an influence on the ultimate outcome.  相似文献   
105.
PURPOSE: Liposomal lurtotecan (OSI-211) is a liposomal formulation of the water-soluble topoisomerase I inhibitor lurtotecan (GI147211), which demonstrated superior levels of activity compared with topotecan in preclinical models. We studied two schedules of OSI-211 in a randomized design in relapsed ovarian cancer to identify the more promising of the two schedules for further study. PATIENTS AND METHODS: Eligible patients had measurable epithelial ovarian, fallopian, or primary peritoneal cancer that was recurrent after one or two prior regimens of chemotherapy. Patients were randomly assigned to receive either arm A (OSI-211 1.8 mg/m(2)/d administered by 30-minute intravenous infusion on days 1, 2, and 3 every 3 weeks) or arm B (OSI-211 2.4 mg/m(2)/d administered by 30-minute intravenous infusion on days 1 and 8 every 3 weeks). The primary outcome measure was objective response, which was confirmed by independent radiologic review, and a pick the winner statistical design was used to identify the schedule most likely to be superior. RESULTS: Eighty-one patients were randomized between October 2000 and September 2001. The hematologic toxic effects were greater on arm A than on arm B (grade 4 neutropenia, 51% v 22%, respectively), as was febrile neutropenia (26% v 2.4%, respectively). Of the 80 eligible patients, eight patients (10%) had objective responses; six responders (15.4%; 95% CI, 6% to 30%) were in arm A and two responders (4.9%; 95% CI, 1% to 17%) were in arm B. CONCLUSION: The OSI-211 daily for 3 days intravenous schedule met the statistical criteria to be declared the winner in terms of objective response. This schedule was also associated with more myelosuppression than the schedule of OSI-211 administered in arm B.  相似文献   
106.
PURPOSE: There are significant differences in reported frequencies, modes of inactivation, and clinical significance of CDKN2A in urothelial cell carcinoma (UCC). We aimed to address these issues by investigating all possible modes of inactivation and clinicopathologic variables in a single tumor panel. EXPERIMENTAL DESIGN: Fifty microdissected UCCs were examined. CDKN2A gene dosage (quantitative real-time PCR), allelic status (microsatellite analysis), hypermethylation (methylation-specific PCR), mutation status (denaturing high-performance liquid chromatography and sequencing), protein expression (immunohistochemistry), and clinicopathologic variables (stage, grade, and disease recurrence during follow-up) were assessed. RESULTS: Exon 2 was underrepresented in 20 of 46 (43%) and exon 1beta in 21 of 46 (46%) of cases. Underrepresentation of exon 2 was accompanied by loss of heterozygosity (LOH) of 9p in 6 of 18 (30%) and of exon 1beta in 11 of 19 assessable cases (58%). Overall, LOH of 9p was identified in 15/41 (37%). Homozygous deletion of exons 2 and 1beta was detected in 16 of 46 (35%) and 10 of 46 tumors (22%), respectively. Co-deletion was most common, but exon 2-specific homozygous deletion was also detected. In tumors without homozygous deletion, p16 promoter hypermethylation was detected in 1 of 18 (6%). Hypermethylation of the p14ARF promoter or mutations in CDKN2A were not observed. Homozygous deletion of exon 2 or LOH on 9p were associated with invasion. Homozygous deletion of exon 2 or exon 1beta was associated with recurrent disease. CONCLUSIONS: These results confirm CDKN2A as a clinically relevant target for inactivation in UCC and show that the true frequency of alteration is only revealed by comprehensive analysis. Our results suggest that CDKN2A may be haploinsufficient in human cancer.  相似文献   
107.
Researchers and clinicians worldwide share concerns that many youngsters with attention-deficit/hyperactivity disorder (ADHD) and/or disruptive behaviour disorders (DBDs) do not receive appropriate treatment despite availability of effective therapies. At the request of Johnson and Johnson (sponsor), 11 international experts in child and adolescent psychiatry were selected by Professor Stan Kutcher (chair) to address these concerns. This paper describes the experts' consensus conclusions, including treatment practice suggestions for physicians involved in the early treatment of youngsters with ADHD (or hyperkinetic disorder, in countries preferring this classification) and/or DBDs internationally: suggested first-line treatment for ADHD without comorbidity is psychostimulant medication aided by psychosocial intervention. For ADHD with comorbid conduct disorder (CD), psychosocial intervention combined with pharmacotherapy is suggested. For primary CD, suggested first-line treatment is psychosocial intervention, with pharmacotherapy considered as an 'add-on' when aggression/impulsivity is marked and persistent. Pharmacotherapy requires careful titration; full-day coverage is the suggested goal. Regular long-term follow-up is recommended.  相似文献   
108.
Low-dose exposure of neonatal mice to nicotine has earlier been shown to induce an altered behavioral response to nicotine in adulthood. Organophosphorus insecticides are known to affect the cholinergic system by inhibition of acetylcholinesterase. This study was undertaken to investigate whether neonatal exposure to nicotine makes mice more susceptible to a known cholinergic agent. Neonatal, 10-day-old, male mice were exposed to nicotine-base (33 microg/kg body weight) or saline s.c. twice daily on five consecutive days. At 5 months of age the animals were exposed to paraoxon (0.17 or 0.25 mg/kg body weight [29% and 37% inhibition of cholinesterase, respectively]) or saline sc every second day for 7 days. Before the first paraoxon injection, the animals were observed for spontaneous motor behavior. The spontaneous motor behavior test did not reveal any differences in behavior between the treatment groups. Immediately after the spontaneous behavior test, the animals received the first injection of paraoxon and were observed for acute effects of paraoxon on spontaneous motor behavior. The acute response to paraoxon in the spontaneous motor behavior test was a decreased level of activity in mice neonatally exposed to nicotine. Control animals showed no change in activity. Two months after the paraoxon treatment, the animals were again tested for spontaneous motor behavior. Animals neonatally exposed to nicotine and exposed to paraoxon as adults showed a deranged spontaneous motor behavior, including hyperactivity and lack of habituation.  相似文献   
109.
110.
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