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   15109篇
  免费   856篇
  国内免费   108篇
耳鼻咽喉   120篇
儿科学   435篇
妇产科学   295篇
基础医学   1944篇
口腔科学   422篇
临床医学   1227篇
内科学   3899篇
皮肤病学   290篇
神经病学   1048篇
特种医学   491篇
外国民族医学   1篇
外科学   2329篇
综合类   90篇
一般理论   5篇
预防医学   949篇
眼科学   168篇
药学   826篇
中国医学   41篇
肿瘤学   1493篇
  2023年   79篇
  2022年   122篇
  2021年   255篇
  2020年   184篇
  2019年   251篇
  2018年   356篇
  2017年   265篇
  2016年   311篇
  2015年   370篇
  2014年   524篇
  2013年   675篇
  2012年   932篇
  2011年   982篇
  2010年   593篇
  2009年   616篇
  2008年   848篇
  2007年   958篇
  2006年   895篇
  2005年   934篇
  2004年   869篇
  2003年   749篇
  2002年   767篇
  2001年   248篇
  2000年   221篇
  1999年   227篇
  1998年   247篇
  1997年   196篇
  1996年   217篇
  1995年   185篇
  1994年   185篇
  1993年   133篇
  1992年   134篇
  1991年   144篇
  1990年   124篇
  1989年   123篇
  1988年   119篇
  1987年   116篇
  1986年   121篇
  1985年   122篇
  1984年   89篇
  1983年   55篇
  1982年   72篇
  1981年   53篇
  1980年   51篇
  1979年   47篇
  1978年   39篇
  1977年   36篇
  1976年   40篇
  1975年   41篇
  1973年   22篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
The present study aims specifically at obtaining a comparison of the acute toxicity of cypermethrin (CY), a type I pyrethroid, and permethrin (PERM), a type II pyrethroid, administered orally as a single dose to neonatal and adult rats, and at assessing the importance of pyrethroid biotransformation in CY and PERM toxicity through use of drug metabolism inhibitors. Our experiments show that CY is more toxic than PERM to adult and neonatal rats. The sensitivity of neonatal rats both to CY and to PERM toxicity is higher, the younger the animals. CY is much more toxic than PERM in the neonatal rat, compared with the adult. In rats aged 8, 16, and 21 days, pretreatment with piperonil butoxide (PB), a monooxygenase inhibitor, or with tri-o-tolyl phosphate (TOTP), an esterase inhibitor, does not produce significant variations in the lethal effects of CY and PERM. Instead, in the adult rats, a significant increase in CY (X2=5.97;p<0.05) and PERM (X2=4.37;p<0.05) mortality occurred in rats pretreated with esterase inhibitors, whereas no increase in CY and PERM toxicity was found in adult animals pretreated with monooxygenase inhibitor. It was concluded that the higher level of sensitivity of the neonate rat to pyrethroid toxicity is probably due to incomplete development of the enzymes which catalyze the metabolism of pyrethroids in the liver of young animals. It is suggested that ester hydrolysis is an important pyrethroids detoxification reaction in the adult rat.  相似文献   
42.
PURPOSE: The purpose of this study was to identify the risk factors for severe discomfort after mandibular third molar surgery and to assess the validity of the Postoperative Symptom Severity (PoSSe) scale. PATIENTS AND METHODS: In a 2-year prospective study, a total of 255 unilateral impacted mandibular third molar teeth were surgically removed under local anesthesia by 3 surgeons. Standardized surgical and analgesic protocols were followed. At the review appointment, 1 week after surgery, all patients returned a completed follow-up questionnaire (PoSSe scale) and were evaluated clinically for postoperative pain (number of painkillers taken) and trismus (differences in mouth opening). Sixteen predictive variables were evaluated using stepwise logistic regression analysis to identify the risk factors associated with severe discomfort. RESULTS: Severe postoperative discomfort was predicted by these independent variables: gender, tobacco use, ramus relationship/space available, and antibiotic prophylaxis. Oral contraceptive use and operation time were not identified as risk factors. The patients' perceptions of the severity of symptoms (PoSSe scale score) was strongly correlated with clinical assessment of trismus (r = 0.54) and pain (r = 0.42). CONCLUSION: The PoSSe scale resulted in a valid and responsive measure of the severity of symptoms after surgical extraction of lower third molars and reflected the clinical severity of the postoperative discomfort. From a patient's perspective, operative factors had little bearing on the quality of life after removal of mandibular third molars.  相似文献   
43.
Over the last five years a policy of systematic screening for small hepatocellular carcinomas (HCC) in patients at risk has led to an increasing number of resections in patients with cirrhosis. Remarkable progress in the surgery of HCC in cirrhosis has been accomplished through: (a) a better understanding of the surgical anatomy of the liver, (b) the definition of new types of liver resection aimed at reducing the amount of parenchyma removed while still being oncologically satisfactory, (c) the reduction of intraoperative blood loss by various techniques of clamping afferent and efferent vessels, (d) the systematic use of intraoperative ultrasonography, and (e) the prevention of postoperative variceal bleeding and the formation of ascites. Results of resection of small HCC in cirrhosis have been quite impressive in Japanese series, with a low operative mortality and above 50% three-year survivals. Results in the West have been somewhat less good. Differences in the pathology of these tumours and particularly in the rate of encapsulation could account for these differences. Clearly, surgical resection has become an established treatment for small HCC in cirrhosis. More information is needed on the results of surgery in operated patients and this should be compared with the natural history of small HCC in cirrhosis in order to better define the patients who will most benefit from these operations and which tests performed at which intervals, are most reliable in screening patients at risk.  相似文献   
44.
45.
46.
47.
As a part of our interest in the performance of [Ti2(OC2H5)8Cl]2Mg2(μ-Cl)2 as Ziegler-Natta catalyst, the polymerization of styrene with a toluene solution of this compound and methyl-aluminoxane as cocatalyst was performed. It was found that the present catalytic system promotes the syndiospecific polymerization of styrene with high stereoregularity and the results were compared with those obtained with MgCl2-supported or unsupported Ti(OC2H5)4 catalysts. Determination of the titanium oxidation states and electron spin resonance (ESR) measurements both in the absence and in the presence of styrene were carried out for all the catalytic systems aimed at shedding some light on the nature of the active species.  相似文献   
48.
Cryopreserved human peripheral blood mononuclear cells (PBMC) were tested for natural killer (NK) and antibody-dependent cellular cytotoxicity (ADCC) and for high-affinity (29°C) and total (4°C) rosette formation with sheep erythrocytes. PBMC produced variable NK activity following freezing and thawing, but consistently reacted well in ADCC. A significant correlation was found between low NK activity and a decreased percentage of low-affinity rosette-forming cells. On the contrary, the number of large granular lymphocytes (LGL), among which NK cells are restricted, and the reactivity with the monoclonal antibody OKT10, which recognizes the majority of LGL in the peripheral blood, were not significantly altered by cryopreservation. Cryopreserved cells proved to be excellent controls for determining the day-to-day variability of the NK assay and for selecting optimum conditions for this test in the clinical immunology laboratory.  相似文献   
49.
The 43 kDa glycoprotein (gp43) of Paracoccidioides brasiliensis is the major diagnostic antigen of paracoccidioidomycosis (PCM), a prevalent fungal infection in South America. A 15-mer sequence from gp43, denominated P10, induced T-CD4+ T helper 1 cellular immune responses in mice of three different haplotypes and protected against intratracheal challenge by a virulent isolate of P. brasiliensis. In an attempt to improve delivery of P10, a promiscuous antigen also presented by human leucocyte antigen-DR alleles, aiming at immunotherapy, we synthesized a multiple antigen peptide with the protective T-cell epitope expressed in a tetravalent 13-mer analog of P10 (M10). M10 induced specific lymph node cell proliferation in mice preimmunized with peptides in complete Freund's adjuvant (CFA). In addition, M10 immunization without CFA significantly protected intratracheally infected mice. We conclude that M10 is a candidate for an anti-PCM vaccine. In this report we describe: (1) the synthesis of M10; (2) the induction of M10-elicited T-cell response and (3) in vivo protection of mice immunized with M10 and challenged by a virulent strain of P. brasiliensis.  相似文献   
50.
A nested case-control study of low birth weight and preterm delivery was performed with singleton women. Immunoglobulin A (IgA) against the Gardnerella vaginalis hemolysin (anti-Gvh IgA) and sialidase and prolidase activities were determined in vaginal fluid at 17 weeks of gestation. Sialidase positivity and bacterial vaginosis with high prolidase activity were associated with 2- and 11-fold increased risks for low birth weight, respectively. No woman with bacterial vaginosis plus a strong anti-Gvh IgA response had an adverse outcome.  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