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   3449篇
  免费   248篇
  国内免费   60篇
耳鼻咽喉   113篇
儿科学   124篇
妇产科学   96篇
基础医学   396篇
口腔科学   117篇
临床医学   424篇
内科学   541篇
皮肤病学   67篇
神经病学   268篇
特种医学   334篇
外科学   286篇
综合类   78篇
一般理论   1篇
预防医学   202篇
眼科学   110篇
药学   227篇
中国医学   2篇
肿瘤学   371篇
  2021年   31篇
  2019年   34篇
  2018年   50篇
  2017年   28篇
  2016年   31篇
  2015年   42篇
  2014年   56篇
  2013年   106篇
  2012年   95篇
  2011年   99篇
  2010年   89篇
  2009年   71篇
  2008年   98篇
  2007年   145篇
  2006年   136篇
  2005年   142篇
  2004年   127篇
  2003年   114篇
  2002年   95篇
  2001年   88篇
  2000年   89篇
  1999年   121篇
  1998年   87篇
  1997年   62篇
  1996年   83篇
  1995年   75篇
  1994年   80篇
  1993年   74篇
  1992年   89篇
  1991年   85篇
  1990年   96篇
  1989年   98篇
  1988年   88篇
  1987年   100篇
  1986年   76篇
  1985年   76篇
  1984年   64篇
  1983年   58篇
  1982年   43篇
  1981年   46篇
  1980年   44篇
  1979年   58篇
  1978年   47篇
  1977年   39篇
  1976年   31篇
  1975年   31篇
  1974年   36篇
  1973年   21篇
  1971年   17篇
  1970年   22篇
排序方式: 共有3757条查询结果,搜索用时 93 毫秒
71.
72.
Physical therapy has become standard procedure for treatment of many aspects of temporomandibular joint dysfunction. In the area of orthognathic surgery, there appears to be a significant gap in the use of physical therapy. This article offers a suggested protocol of treatment to improve the overall outcome and provide for consistency of treatment.  相似文献   
73.
74.
75.
We present a rare condition, hyperkeratosis of the areola, induced by vemurafenib. Only a few papers have described an association of BRAF inhibitors with hyperkeratosis of the areola and/or nipple. Vemurafenib is a selective BRAF inhibitor used in patients with unresectable or metastatic melanoma who are positive for the V600 mutation. This drug has been associated with numerous cutaneous side effects, both benign and malignant. We report a male patient with vemurafenib‐induced hyperkeratosis of the areola managed successfully with a topical retinoid, and describe for the first time a treatment for this side effect.  相似文献   
76.
Various modeling methods have been proposed to estimate the potential predictive ability of polygenic risk variants that predispose to various common diseases. However, it is unknown whether differences between them affect their conclusions on predictive ability. We reviewed input parameters, assumptions and output of the five most common methods and compared their estimates of the area under the receiver operating characteristic (ROC) curve (AUC) using hypothetical data representing effect sizes and frequencies of genetic variants, population disease risk and number of variants. To assess the accuracy of the estimated AUCs, we aimed to reproduce the AUCs of published empirical studies. All methods assumed that the combined effect of genetic variants on disease risk followed a multiplicative risk model of independent genetic effects, but they either assumed per allele, per genotype or dominant/recessive effects for the genetic variants. Modeling strategy and input parameters differed. Methods used simulation analysis or analytical formulas with effect sizes quantified by odds ratios (ORs) or relative risks. Estimated AUC values were similar for lower ORs (<1.2). When AUCs were larger (>0.7) due to variants with strong effects, differences in estimated AUCs between methods increased. The simulation methods accurately reproduced the AUC values of empirical studies, but the analytical methods did not. We conclude that despite differences in input parameters, the modeling methods estimate similar AUC for realistic values of the ORs. When one or more variants have stronger effects and AUC values are higher, the simulation methods tend to be more accurate.  相似文献   
77.
It is widely accepted that modern humans originated in sub-Saharan Africa approximately 150-200 thousand years ago (ka), but their route of dispersal across the currently hyperarid Sahara remains controversial. Given that the first modern humans north of the Sahara are found in the Levant approximately 120-90 ka, northward dispersal likely occurred during a humid episode in the Sahara within Marine Isotope Stage (MIS) 5e (130-117 ka). The obvious dispersal route, the Nile, may be ruled out by notable differences between archaeological finds in the Nile Valley and the Levant at the critical time. Further west, space-born radar images reveal networks of-now buried-fossil river channels that extend across the desert to the Mediterranean coast, which represent alternative dispersal corridors. These corridors would explain scattered findings at desert oases of Middle Stone Age Aterian lithic industries with bifacial and tanged points that can be linked with industries further to the east and as far north as the Mediterranean coast. Here we present geochemical data that demonstrate that water in these fossil systems derived from the south during wet episodes in general, and penetrated all of the way to the Mediterranean during MIS 5e in particular. This proves the existence of an uninterrupted freshwater corridor across a currently hyperarid region of the Sahara at a key time for early modern human migrations to the north and out of Africa.  相似文献   
78.
Transmission of HIV to heterosexual partners of infected men and women   总被引:2,自引:0,他引:2  
Future heterosexual spread of HIV will in part depend on the efficiency of transmission from men to women and from women to men. We studied seventy-eight female sexual partners of men infected with HIV and 18 male sexual partners of infected women. Participants were interviewed concerning sexual practices, use of contraception and other risk factors for HIV infection. Fifteen out of 78 (19.2%) female partners and one out of eighteen (5.5%) male partners were seropositive for HIV antibody. All couples had practised vaginal intercourse. Seropositive female partners did not differ significantly from seronegative partners with regard to length of relationship, number of acts of vaginal intercourse, other sexual practices, stage of clinical disease in the index case, or numbers of other sexual partners in the last five years. In two women, seroconversion was documented after one act of unprotected sexual intercourse. The majority of infected female partners (eight out of 15) had sexual relationships with men who were asymptomatic and did not practice anal intercourse. Biological factors such as variability in infectivity of the index case and susceptibility of the contact, as well as behavioural variables may be important in determining transmission.  相似文献   
79.
We have identified and molecularly characterized a novel deletion in the beta-globin gene cluster that increases fetal hemoglobin (HbF) synthesis in a 24-year-old Laotian man who is heterozygous for this mutation. The patient is asymptomatic with a mild anemia, hypochromia, and microcytosis (Ht = 39%, MCH = 22.8 pg, MCV = 71 fl), normal levels of HbA2 (3.0%) and 11.5% HbF (G gamma A gamma ratio 60 to 40), with heterocellular distribution (52% F cells). Extensive restriction endonuclease mapping defined the 5' breakpoint within the IVS II of the delta-globin gene, between positions 775 to 781 very similar to the 5' breakpoint of the Sicilian delta beta-thalassemia. However, the 3' breakpoint was localized between two Pst I sites 4.7 kb 3' of the beta- globin gene, thus ending about 0.7 kb upstream from the 3' breakpoint of the Sicilian delta beta-thalassemia. This results in a 12.5 kb deletion of DNA. It is of interest that the 5' breakpoint of the deletion residues within an AT-rich region which has been proposed as a specific recognition signal for recombination events, while the 3' breakpoint lies within a cluster of L1 repetitive sequences (formerly known as Kpn I family repeats). The presence of the 3' breakpoints of several other deletions within this region of L1 repeats also suggests that such sequences might serve as hot spots for recombination and eventually lead to thalassemia deletions. The similarity of the 5' and 3' breakpoints of these delta beta-thalassemias underscores the putative regulatory role of the deleted and juxtaposed sequences on the expression of the gamma-globin genes in adult life.  相似文献   
80.

Background

Current approaches to chemical screening, prioritization, and assessment are being reenvisioned, driven by innovations in chemical safety testing, new chemical regulations, and demand for information on human and environmental impacts of chemicals. To conceptualize these changes through the lens of a prevalent disease, the Breast Cancer and Chemicals Policy project convened an interdisciplinary expert panel to investigate methods for identifying chemicals that may increase breast cancer risk.

Methods

Based on a review of current evidence, the panel identified key biological processes whose perturbation may alter breast cancer risk. We identified corresponding assays to develop the Hazard Identification Approach for Breast Carcinogens (HIA-BC), a method for detecting chemicals that may raise breast cancer risk. Finally, we conducted a literature-based pilot test of the HIA-BC.

Results

The HIA-BC identifies assays capable of detecting alterations to biological processes relevant to breast cancer, including cellular and molecular events, tissue changes, and factors that alter susceptibility. In the pilot test of the HIA-BC, chemicals associated with breast cancer all demonstrated genotoxic or endocrine activity, but not necessarily both. Significant data gaps persist.

Conclusions

This approach could inform the development of toxicity testing that targets mechanisms relevant to breast cancer, providing a basis for identifying safer chemicals. The study identified important end points not currently evaluated by federal testing programs, including altered mammary gland development, Her2 activation, progesterone receptor activity, prolactin effects, and aspects of estrogen receptor β activity. This approach could be extended to identify the biological processes and screening methods relevant for other common diseases.

Citation

Schwarzman MR, Ackerman JM, Dairkee SH, Fenton SE, Johnson D, Navarro KM, Osborne G, Rudel RA, Solomon GM, Zeise L, Janssen S. 2015. Screening for chemical contributions to breast cancer risk: a case study for chemical safety evaluation. Environ Health Perspect 123:1255–1264; http://dx.doi.org/10.1289/ehp.1408337  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