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   4808篇
  免费   465篇
  国内免费   12篇
耳鼻咽喉   165篇
儿科学   267篇
妇产科学   131篇
基础医学   580篇
口腔科学   130篇
临床医学   531篇
内科学   817篇
皮肤病学   55篇
神经病学   380篇
特种医学   178篇
外科学   760篇
综合类   209篇
预防医学   431篇
眼科学   169篇
药学   304篇
中国医学   2篇
肿瘤学   176篇
  2021年   71篇
  2020年   48篇
  2019年   91篇
  2018年   95篇
  2017年   74篇
  2016年   70篇
  2015年   87篇
  2014年   106篇
  2013年   155篇
  2012年   221篇
  2011年   232篇
  2010年   131篇
  2009年   142篇
  2008年   229篇
  2007年   207篇
  2006年   231篇
  2005年   198篇
  2004年   188篇
  2003年   169篇
  2002年   168篇
  2001年   168篇
  2000年   185篇
  1999年   161篇
  1998年   65篇
  1997年   57篇
  1996年   71篇
  1995年   45篇
  1994年   52篇
  1993年   45篇
  1992年   109篇
  1991年   92篇
  1990年   88篇
  1989年   88篇
  1988年   80篇
  1987年   76篇
  1986年   85篇
  1985年   85篇
  1984年   69篇
  1983年   51篇
  1982年   51篇
  1981年   37篇
  1980年   31篇
  1979年   46篇
  1978年   41篇
  1977年   38篇
  1976年   34篇
  1975年   45篇
  1974年   42篇
  1973年   32篇
  1968年   44篇
排序方式: 共有5285条查询结果,搜索用时 15 毫秒
71.
The purpose of this study was to determine whether the single nucleotide polymorphisms (SNPs) within candidate genes for attention deficit hyperactivity disorder (ADHD) are associated with the age at onset for ADHD. One hundred and forty-three SNPs were genotyped across five candidate genes ( DRD5 , SLC6A3 , HTR1B , SNAP25 , DRD4 ) for ADHD in 229 families with at least one affected offspring. SNPs with the highest estimated power to detect an association with age at onset were selected for each candidate gene, using a power-based screening procedure that does not compromise the nominal significance level. A time-to-onset analysis for family-based samples was performed on these SNPs to determine if an association exists with age at onset for ADHD. Seven consecutive SNPs surrounding the D5 dopamine receptor gene ( DRD5 ), were associated with the age at onset for ADHD; FDR adjusted q-values ranged from 0.008 to 0.023. This analysis indicates that individuals with the risk genotype develop ADHD earlier than individuals with any other genotype. A haplotype analysis across the 6 significant SNPs that were in linkage disequilibrium with one another, CTCATA , was also found to be significant (p-value = 0.02). We did not observe significant associations with age at onset for the other candidate loci tested. Although definitive conclusions await independent replication, these results suggest that a variant in DRD5 may affect age at onset for ADHD.  相似文献   
72.
Atypical femur fractures (AFF) are a rare but serious complication of long-term bisphosphonate use. Although clearly defined by ASBMR criteria, a proportion of patients with AFFs may go unrecognized and the use of qualitative fracture criteria may lead to uncertainty in AFF diagnosis, with significant therapeutic implications. A score that rapidly and accurately identifies AFFs among subtrochanteric femur fractures using quantitative, measurable parameters is needed. In a retrospective cohort of 110 female patients presenting with AFFs or typical femur fractures (TFFs), multiple logistic regression and decision tree analysis were used to develop the Sydney AFF score. This score, based on demographic and femoral geometry variables, uses three dichotomized independent predictors and adds one point for each: (age ≤80 years) + (femoral neck width <37 mm) + (lateral cortical width at lesser trochanter ≥5 mm), (score, 0 to 3). In an independent validation set of 53 female patients at a different centre in Sydney, a score ≥2 demonstrated 73.3% sensitivity and 69.6% specificity for AFF (area under the receiver-operating characteristic curve [AUC] 0.775, SE 0.063) and remained independently associated with AFF after adjustment for bisphosphonate use. The Sydney AFF score provides a quantitative means of flagging female patients with atraumatic femur fractures who have sustained an AFF as opposed to a TFF. This distinction has clear management implications and may augment current ASBMR diagnostic criteria. © 2021 American Society for Bone and Mineral Research (ASBMR).  相似文献   
73.
Organ transplant recipients (OTRs) are at increased risk of cutaneous malignancy. Skin disorders in OTRs of color (OTRoC) have rarely been systematically assessed. We aimed to ascertain the burden of skin disease encountered in OTRoC by prospectively collecting data from OTRs attending 2 posttransplant skin surveillance clinics: 1 in London, UK and 1 in Philadelphia, USA. Retrospective review of all dermatological diagnoses was performed. Data from 1766 OTRs were analyzed: 1024 (58%) white, 376 (21%) black, 261 (15%) Asian, 57 (3%) Middle Eastern/Mediterranean (ME/M), and 48 (2.7%) Hispanic; and 1128 (64%) male. Viral infections affected 45.1% of OTRs, and were more common in white and ME/M patients (P < .001). Fungal infections affected 28.1% and were more common in ME/M patients (P < .001). Inflammatory skin disease affected 24.5%, and was most common in black patients (P < .001). In addition, 26.4% of patients developed skin cancer. There was an increased risk of skin cancer in white vs nonwhite OTRs (HR 4.4, 95% CI 3.5-5.7, P < .001): keratinocyte cancers were more common in white OTRs (P < .001) and Kaposi sarcoma was more common in black OTRs (P < .001). These data support the need for programs that promote targeted dermatology surveillance for all OTRs, regardless of race/ethnicity or country of origin.  相似文献   
74.

The current study examined the relevance of relationship functioning to partners’ agreement or consensus about joint effort surrounding COVID-19 prevention. Interdependence theory has been widely used to understand how relationship partners influence health behavior, including how sexual minority male (SMM) couples regulate HIV risk. Couples with better relationship functioning tend to be more successful at negotiating joint (shared) goals and subsequently accomplishing them. The study recruited 134 cis-male, SARS-CoV-2 negative adults in relationships with cis-male partners from phone-based social networking applications. Participants completed an online survey assessing relationship functioning (Perceived Relationship Components Questionnaire), COVID-19 prevention behaviors, and risk perceptions. Partners’ consensus around joint COVID-19 prevention effort was assessed using an adapted version of the Preferences for Sexual Health Outcomes scale. Path analyses indicated that consensus for joint prevention effort predicted social distancing (B?=?0.23; p?=?.001) and the number of other COVID-19 prevention behaviors engaged in (B?=?0.17; p?=?.003) above and beyond perceived risk and relationship functioning. Relationship satisfaction predicted higher levels of consensus for joint COVID-19 prevention effort (B?=?0.40; p?=?.029). Findings suggest that the theoretical foundations of successful HIV prevention interventions that utilize joint goal formation may generalize to the prediction of COVID-19 prevention behavior and may be leveraged to mitigate the risk of SARS-CoV-2 infection among SMM in relationships. Interventions that overlook the potential for dyadic regulation of health behavior may miss opportunities to capitalize on shared coping resources and fail to address relational barriers to prevention.

  相似文献   
75.
76.
The antinociceptive effects of (THC-7-oic) acid have been investigated further with particular regard to the influence of certain experimental parameters in the hot plate test. These included the degree of the thermal stimulus, the nature of the vehicle and a possible role for copper in the response. A temperature effect similar to that seen with nonsteroidalantiinflammatory drugs (NSAIDs) was observed, 55° produced observable antinociception, however, at a surface temperature of 58°C no drug effect was seen. Non-aqeous vehicles such as peanut oil increased the potency of THC-7-oic acid. Finally, the substitution of purified water for tap water reduced,the drug response which could be partially restored by adding copper to the purified drinking water. An increase in the inhibitory effect when copper was added was also seenin vitro in a cell culture model where the acid reduced prostaglandin synthesis induced by THC. Our findings suggest that THC-7-oic acid probably acts by mechanisms similar to the NSAIDs and that the above mentioned experimental conditions can greatly influence the outcome of studies with this agent.  相似文献   
77.
The Glycine tabacina polyploid complex has been shown to include a minimum of two morphological and crossing groups, which also differ in chloroplast DNA (cpDNA) restriction map and nuclear ribosomal gene repeat phenotype. These AAB2B2 and BBB2B2 G. tabacina polyploids contain plastomes referable to the A and B diploid plastome groups of subgenus Glycine, respectively. Eight different cpDNA variants were observed among the 65 B-type polyploids studied, six of which were identical for numerous restriction site characters to plastome types found among the highly polymorphic B genome diploid species. It is hypothesized that there have been numerous independent origins of polyploid G. tabacina: at least one AA x B2B2 event and a minimum of five BB x B2B2 events involving different BB types as female progenitor. Low amounts of cpDNA divergence between diploid and polyploid plastomes and among the plastomes of geographically disjunct polyploids suggest that the origin and dispersal of polyploids are relatively recent events. All hypothesized diploid progenitors are native to Australia, while both A- and B-type G. tabacina polyploids occur on islands of the Pacific outside the range of diploids. The presence of several different plastome types of polyploid G. tabacina in the Pacific islands suggests that several colonization events have occurred.  相似文献   
78.
Summary There is very suggestive evidence for a role of serotonin release from platelets in the mechanisms for platelet aggregation, arterial thrombosis, and arterial spasm. These effects are mediated via the 5HT2 receptor and are specifically antagonized by ketanserin. The recently published PACK study was a randomized controlled trial of the effects of ketanserin in patients with intermittent claudication. The purpose of the trial was to discover whether ketanserin treatment would reduce the incidence of atherosclerotic complications such as myocardial infarction or stroke. An unexpected adverse interaction between ketanserin and potassium-losing diuretics was observed, causing an excess of deaths in the group taking this combination of drugs. The intention-to-treat analysis showed no overall difference between ketanserin and placebo in terms of cardiovascular complications. Withdrawal of patients taking potassium-losing diuretics left insufficient numbers of patients in the study to answer the original question. However, the on-treatment analysis excluding those taking the combination suggested strongly, although did not prove, that ketanserin reduced thrombotic episodes by about 25%. It is concluded that the risks of interactions between many drugs and potassium-losing diuretics make the use of the latter undesirable. Further studies on ketanserin, possibly combined with thromboxane A2 inhibitors, seem highly desirable.  相似文献   
79.
Australia is a country of 17 million people from diverse cultural and racial backgrounds. To respond to this diversity, the Australian Commonwealth Government in 1986 announced an Access and Equity Strategy as part of the Agenda for a Multicultural Australia. The Strategy was evaluated in 1991, and included five locality studies which assessed the implementation of the Strategy from the perspective of target groups of Aboriginal and non-English speaking people (NESB). This article describes this evaluation and the development of the Australian multicultural policy within which the Strategy is conceived. The findings and recommendations from the locality studies provide case examples of government wide policy development and implementation processes.  相似文献   
80.
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