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   3413篇
  免费   199篇
  国内免费   9篇
耳鼻咽喉   86篇
儿科学   201篇
妇产科学   73篇
基础医学   538篇
口腔科学   104篇
临床医学   270篇
内科学   613篇
皮肤病学   91篇
神经病学   246篇
特种医学   163篇
外科学   309篇
综合类   82篇
一般理论   1篇
预防医学   163篇
眼科学   171篇
药学   234篇
中国医学   25篇
肿瘤学   251篇
  2023年   31篇
  2022年   54篇
  2021年   113篇
  2020年   73篇
  2019年   95篇
  2018年   89篇
  2017年   68篇
  2016年   96篇
  2015年   107篇
  2014年   132篇
  2013年   177篇
  2012年   236篇
  2011年   276篇
  2010年   153篇
  2009年   148篇
  2008年   201篇
  2007年   202篇
  2006年   152篇
  2005年   187篇
  2004年   145篇
  2003年   140篇
  2002年   126篇
  2001年   92篇
  2000年   58篇
  1999年   42篇
  1998年   23篇
  1997年   23篇
  1996年   13篇
  1995年   13篇
  1994年   9篇
  1993年   8篇
  1992年   17篇
  1991年   26篇
  1990年   21篇
  1989年   14篇
  1988年   23篇
  1987年   24篇
  1986年   15篇
  1985年   22篇
  1984年   11篇
  1983年   12篇
  1982年   8篇
  1980年   15篇
  1979年   11篇
  1977年   13篇
  1976年   11篇
  1975年   16篇
  1974年   10篇
  1972年   9篇
  1971年   12篇
排序方式: 共有3621条查询结果,搜索用时 31 毫秒
101.
Human papilloma virus (HPV) infection is a major cause of cervix cancer, but a number of infected women do not develop invasive lesions, suggesting that HPV infection in itself is not a sufficient factor and that other cofactors, such as smoking, play an important role in development of cervix cancer. Alongside active cigarette smoking, passive smoking is an independent risk factor for cervix cancer. Smoking maintains cervical HPV infection longer and decreases potential of clearing an oncogenic infection. Thus, it is quite possible that polymorphism at detoxifying enzyme coding loci such as GSTM1, GSTT1, and GSTP1 may determine susceptibility to cervix cancer. This study evaluates the combined effects of genetic polymorphisms of GSTM1, GSTT1, and GSTP1 on susceptibility to cervical cancer and interaction of these genes with smoking. On individual analysis of GSTM1, GSTT1, and GSTP1, it was observed that passive smokers having genotypes GSTM1 (null) (OR = 7.0, 95% CI = 2.19-22.36, P = 0.0005), GSTT1 (null) (OR = 10.2, 95% CI = 1.23-84.18, P = 0.02), and GSTP1 (ile/val) (OR = 6.4, 95% CI = 2.25-18.38, P = 0.0005) have an increased risk of developing cervix cancer. It is thus concluded that cervical cancer risk is increased in passive smokers with GSTM1 (null), GSTT1 (null), and GSTP1 (ile/val) genotypes.  相似文献   
102.
OBJECTIVE: Osteoporosis is a significant health problem in postmenopausal women. Consequently, new and effective therapies are being sought to preserve bone mass and prevent osteoporosis in this population of women. The objective of this study was to compare the effects of lasofoxifene with raloxifene and placebo on indices of bone health in postmenopausal women. DESIGN: A randomized, double-blind, placebo- and active treatment-controlled study of 2 years duration was conducted. Women included 410 postmenopausal women aged 47 to 74 years. The four treatment groups were: lasofoxifene 0.25 mg/day, or 1.0 mg/day, raloxifene 60 mg/day, or placebo daily. All women received daily calcium and vitamin D supplements. The primary endpoint was percent change from baseline to 2 years in lumbar spine bone mineral density (BMD) in all women having baseline and at least one follow-up bone density measurement. Total hip BMD, biochemical markers of bone turnover, low-density lipoprotein cholesterol, and safety were also evaluated in all women. RESULTS: Both doses of lasofoxifene significantly increased lumbar spine BMD compared with raloxifene (P < or = 0.05) and with placebo treatment (P < or = 0.05). Least squares mean increases (95% CI) from baseline in lumbar spine BMD, compared with placebo, were 3.6% (1.9, 5.2) for lasofoxifene 0.25 mg/day, 3.9% (2.4, 5.5) for lasofoxifene 1.0 mg/day, and 1.7% (0.3, 3.0) for raloxifene. The two doses of lasofoxifene and raloxifene were equally effective at increasing total hip BMD. Lasofoxifene and raloxifene significantly reduced the levels of biochemical markers of bone turnover compared with placebo. In general, the effects of lasofoxifene were greater than the responses to raloxifene. At 2 years, lasofoxifene significantly (P < or = 0.05) reduced low-density lipoprotein cholesterol levels by 20.6% and 19.7% with 0.25 mg/day and 1 mg/day, respectively, compared with raloxifene (12.1%) and placebo (3.2%). Lasofoxifene and raloxifene had a similar adverse event profile with low rate of discontinuations due to adverse events. CONCLUSIONS: Lasofoxifene may be an effective and well-tolerated treatment option for the prevention of bone loss in postmenopausal women.  相似文献   
103.
104.
The complement lectin pathway, an essential component of the innate immune system, is geared for rapid recognition of infections as each C4b deposited via this pathway is capable of forming a C3/C5 convertase. In the present study, role of C4b-binding protein (C4BP) in regulating the lectin pathway C3/C5 convertase assembled on zymosan and sheep erythrocytes coated with mannan (EMan) was examined. While the C4BP concentration for inhibiting 50% (IC50) formation of surface-bound C3 convertase on the two surfaces was similar to that obtained for the soluble C3 convertase (1.05 nM), 3- and 41-fold more was required to inhibit assembly of the C5 convertase on zymosan (2.81 nM) and EMan (42.66 nM). No difference in binding interactions between C4BP and surface-bound C4b alone or in complex with C3b was observed. Increasing the C4b density on zymosan (14,000–431,000 C4b/Zym) increased the number of C4b bound per C4BP from 2.87 to 8.23 indicating that at high C4b density all seven α-chains of C4BP are engaged in C4b-binding. In contrast, the number of C4b bound per C4BP remained constant (3.79 ± 0.60) when the C4b density on EMan was increased. The data also show that C4BP regulates assembly and decay of the lectin pathway C3/C5 convertase more stringently than the classical pathway C3/C5 convertase because of a 7- to 13-fold greater affinity for C4b deposited via the lectin pathway than the classical pathway. C4BP thus regulates efficiently the four times greater potential of the lectin pathway than the classical pathway in generating the C3/C5 convertase and hence production of pro-inflammatory products, which are required to fight infections but occasionally cause pathological inflammatory reactions.  相似文献   
105.
HLA‐DRB1*0401 expression in humans has been associated with a predisposition to developing rheumatoid arthritis (RA) and collagen‐induced arthritis (CIA), while HLA‐DRB1*0402 is not associated with susceptibility. Here, we determined if mice transgenic (Tg) for human *0401 have a CD4+ T‐cell repertoire that predetermines proinflammatory cytokine production. The data show that both *0401 and *0402 Tg mice can produce TH1/TH17 cytokines, although the kinetics of response may be different. However, in the context of antigen‐specific responses in a CIA model, *0402 Tg mice generate a TH2 response that may explain their resistance to developing arthritis. In addition, a significant subset of naïve CD4+ T cells from *0402 Tg mice can be activated in polarizing conditions to differentiate into Treg cells that produce IFN‐γ. *0401 Tg mice harbor memory CD4+ T cells that differentiate into IL‐17+ cells in various polarizing conditions. Our data suggest that *0401 Tg mice generate a strong immune response to lipopolysaccharide and may be efficient in clearing infection, and may *0401 have been evolutionarily selected for this ability. Autoimmunity, such as RA, could likely be a bystander effect of the cytokine storm that, along with the presence of low Treg‐cell numbers in *0401 Tg mice, causes immune dysregulation.  相似文献   
106.
Malaria and dengue are the two most important vector-borne human diseases caused by mosquito vectors Anopheles stephensi and Aedes aegypti, respectively. Of the various strategies adopted for eliminating these diseases, controlling of vectors through herbs has been reckoned as one of the important measures for preventing their resurgence. Artemisia annua leaf chloroform extract when tried against larvae of A. stephensi and A. aegypti has shown a strong larvicidal activity against both of these vectors, their respective LC50 and LC90 values being 0.84 and 4.91 ppm for A. stephensi and 0.67 and 5.84 ppm for A. aegypti. The crude extract when separated through column chromatography using petroleum ether-ethyl acetate gradient (0–100 %) yielded 76 fractions which were pooled into three different active fractions A, B and C on the basis of same or nearly similar R f values. The aforesaid pooled fractions when assayed against the larvae of A. stephensi too reported a strong larvicidal activity. The respective marker compound purified from the individual fractions A, B and C, were Artemisinin, Arteannuin B and Artemisinic acid, as confirmed and characterized through FT-IR and NMR. This is our first report of strong mortality of A. annua leaf chloroform extract against vectors of two deadly diseases. This technology can be scaled up for commercial exploitation.  相似文献   
107.
Genes interact in networks to orchestrate cellular processes. Analysis of these networks provides insights into gene interactions and functions. Here, we took advantage of normal variation in human gene expression to infer gene networks, which we constructed using correlations in expression levels of more than 8.5 million gene pairs in immortalized B cells from three independent samples. The resulting networks allowed us to identify biological processes and gene functions. Among the biological pathways, we found processes such as translation and glycolysis that co-occur in the same subnetworks. We predicted the functions of poorly characterized genes, including CHCHD2 and TMEM111, and provided experimental evidence that TMEM111 is part of the endoplasmic reticulum-associated secretory pathway. We also found that IFIH1, a susceptibility gene of type 1 diabetes, interacts with YES1, which plays a role in glucose transport. Furthermore, genes that predispose to the same diseases are clustered nonrandomly in the coexpression network, suggesting that networks can provide candidate genes that influence disease susceptibility. Therefore, our analysis of gene coexpression networks offers information on the role of human genes in normal and disease processes.The functions of many human genes are unknown. It is not unusual that when one searches the literature on a gene, one fails to find any papers that provide information on its biological roles. Identifying gene function is difficult, especially if no hints, such as homologies to known genes, are available to direct the search. However, since genes work by interacting with other genes, we may learn about their functions through their neighboring genes (Stuart et al. 2003; Ayroles et al. 2009). Identifying gene function is increasingly important; in the last several years, genome-wide association studies (GWAS) have identified DNA variants that are associated with common complex diseases. But for many of these studies, the functional links between the susceptibility genes and the diseases are unknown.In this study, we used correlations in expression levels of more than 8.5 million human gene pairs in immortalized B cells from three data sets to infer gene coexpression networks. The resulting gene networks were based on correlations between genes that were found reproducibly in the three data sets. This provided us with gene networks in which we had high confidence in the gene correlations. We then used the networks to identify key biological processes and interactions among those processes in our cells. Then, we identified the functions of 36 human genes with no known functions and four genes that have been implicated in GWAS as susceptibility genes for common human diseases, including IFIH1, which was recently found to be associated with type 1 diabetes.  相似文献   
108.

The aim of the study was to analyse risk factors, surgical findings, ovarian salvage rate and histology of ovarian mass. We reviewed 81 cases of surgically proven ovarian torsion retrospectively from June 2014 to June 2019 at a tertiary care referral centre in South India. Demographic, clinical and surgical details of all patients were noted from the medical records. Mean age of the patients was 26 years. Most of the patients were nulliparous and had a pre-existing ovarian mass of size >?5 cm. Ovarian salvage rate was 43.2%. Concomitant cystectomy with detorsion was done in 30 patients without increase in blood loss or complications. Extensive necrosis was present in 78.2% of oophorectomy specimens. Most common histology of ovarian mass in cystectomy specimens was simple ovarian cyst.

  相似文献   
109.
Objective :To investigate the sources of lead in the environment in children with elevated blood, with the help of a Field Portable X-Ray Fluorescence Analyzer.Methods : One hundred and seven school children were chosen for this study on a random basis, from Mangalore and Karnataka. Their blood lead was analyzed. Of the cases analyzed, 10 students whose blood lead level was more than 40 μg/dl were investigated using a field portable X-Ray Fluorescence Analyzer. This is the first time such a device has been available for this purpose in India.Results: The ‘likely’ source of lead exposure could be determined in eight cases which was from the immediate environment of the children like ‘lead-based’ paint on surfaces in the house, on playground and other exterior equipment; lead storage batteries, contaminated dust and soil and other lead-containing substances.Conclusion: The use of an X-Ray Fluorescence Analyser appeared to be useful in determining the source of lead  相似文献   
110.
The present paper reports a combination of radioanalytical and green methodology for the ultra-trace scale speciation of molybdenum. The differential attitude of iron-doped calcium alginate (Fe–CA) and chitosan biopolymers towards no-carrier-added 93mMo radionuclide was studied to develop environmentally sustainable speciation methodology in ultra-trace scale. The affinity of 93mMo towards the Fe–CA beads is greater than that of chitosan. Species information was obtained by comparing the adsorption profile of 93mMo on Fe–CA and chitosan biopolymer with the software code CHEAQS PRO program. From the experimental results it is concluded that no-carrier-added 93mMo radionuclide form mononuclear species instead of polynuclear species in aqueous solution. Use of biodegradable, non-toxic biopolymer makes this method a step forward towards green chemistry.  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