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   2083篇
  免费   165篇
  国内免费   39篇
耳鼻咽喉   20篇
儿科学   35篇
妇产科学   67篇
基础医学   276篇
口腔科学   64篇
临床医学   260篇
内科学   457篇
皮肤病学   11篇
神经病学   126篇
特种医学   47篇
外科学   268篇
综合类   252篇
现状与发展   1篇
预防医学   96篇
眼科学   40篇
药学   176篇
  1篇
中国医学   21篇
肿瘤学   69篇
  2024年   6篇
  2023年   34篇
  2022年   67篇
  2021年   86篇
  2020年   82篇
  2019年   71篇
  2018年   81篇
  2017年   73篇
  2016年   69篇
  2015年   91篇
  2014年   133篇
  2013年   162篇
  2012年   78篇
  2011年   99篇
  2010年   111篇
  2009年   102篇
  2008年   99篇
  2007年   103篇
  2006年   79篇
  2005年   55篇
  2004年   66篇
  2003年   59篇
  2002年   49篇
  2001年   36篇
  2000年   34篇
  1999年   24篇
  1998年   28篇
  1997年   40篇
  1996年   29篇
  1995年   23篇
  1994年   27篇
  1993年   22篇
  1992年   15篇
  1991年   11篇
  1990年   16篇
  1989年   14篇
  1988年   16篇
  1987年   14篇
  1986年   8篇
  1985年   10篇
  1984年   17篇
  1983年   10篇
  1982年   14篇
  1981年   10篇
  1980年   1篇
  1979年   2篇
  1978年   2篇
  1977年   4篇
  1974年   4篇
  1971年   1篇
排序方式: 共有2287条查询结果,搜索用时 15 毫秒
41.
To explore the optimal way to manage patients with high-grade squamous intraepithelial lesion (HSIL) and positive margin by identifying the risk factors for its recurrence and residue.A retrospective study was conducted on 267 cases of a pathologically confirmed HSIL with positive margin following conization by loop electrosurgical excisional procedure (LEEP) between January 2010 and December 2015. One hundred two cases were selected for regular follow-up every 6 months, and 165 cases were selected for a second surgery (repeat cervical conization or hysterectomy) within 3 months of initial LEEP. We analyzed the association between recurrent or residual diseases and these factors: age, menopausal status, ThinPrep cytologic test (TCT) results, high-risk human papillomavirus (HR-HPV) infection, pathological grades of the margin, number of involved margins, and glandular involvement.The recurrence rate among 102 cases who underwent follow-up was 17.6% (18/102). The factors: atypical squamous cells of undetermined significance cannot exclude HSIL (ASC-H) or higher lesions in the pre-LEEP TCT (P = .038), persistent HR-HPV infection at the 6th month post-LEEP (P = .03), HSIL-positive margin (P = .003), and multifocal-involved margin (P = .002) were significantly associated with recurrent disease, while age, menopause, and pre-LEEP HR-HPV infection were not associated with recurrent disease (P > .05). The residual rate among 165 patients who underwent a second surgery was 45.5% (75/165), of which 15 cases were residual cervical cancer. The factors: menopause (P = .02), ≥ASC-H in pre-LEEP TCT (P = .04), pre-LEEP HR-HPV infection (P = .04), ≥HSIL-positive margin (P < .001), and multifocal-involved margin (P < .001) significantly increased the risk of residual disease. No correlation existed between residual disease and age or glandular involvement (P > .05).For patients with a positive margin after LEEP, regular follow-up or second surgery should be selected according to fertility requirement and pathological characteristics of the positive margin, as well as TCT and HR-HPV infection condition.  相似文献   
42.
Serving as one of our primary environmental inputs, vision is the most sophisticated sensory system in humans. Here, we present recent findings derived from energetics, genetics and physiology that provide a more advanced understanding of color perception in mammals. Energetics of cistrans isomerization of 11-cis-retinal accounts for color perception in the narrow region of the electromagnetic spectrum and how human eyes can absorb light in the near infrared (IR) range. Structural homology models of visual pigments reveal complex interactions of the protein moieties with the light sensitive chromophore 11-cis-retinal and that certain color blinding mutations impair secondary structural elements of these G protein-coupled receptors (GPCRs). Finally, we identify unsolved critical aspects of color tuning that require future investigation.  相似文献   
43.
44.
AIM: Patients with recurrent syncope undiagnosed after extensive non-invasive and invasive testing pose a diagnostic and therapeutic dilemma. Holter monitoring is nondiagnostic in 90% of cases. Recent developments in loop recorder technology permit long-term ECG monitoring in patients with recurrent unexplained syncope. The aim of this study was to report the worldwide experience with a new subcutaneously implantable loop recorder, implanted in 133 patients with unexplained syncope and negative laboratory investigations. METHODS AND RESULTS: The implantable loop recorder monitors continuously a single lead electrogram using two sensing electrodes on the device shell. The device was implanted in 133 patients, 67 male and 66 female with recurrent syncope. During a mean follow-up of 10.8 +/- 4.3 months after device implantation, 83 patients (62%) experienced syncope or pre-syncope. In the remaining 50 patients no diagnosis could be made because either no events occurred, the patients were lost to follow-up, had adverse events, or died prior to diagnosis. In 72 of the 83 patients with syncope during follow-up (87%), loop recording definitively determined whether an arrhythmia was the cause of symptoms or not. Diagnosis included bradycardia in 21 patients, pacemaker dysfunction in one patient, and tachycardia in 10 patients. One patient experienced multiple rhythm disturbances. Syncope was non-arrhythmic in 40 patients. The remaining 11 patients failed to press the activator. Therapy was instituted in all patients, in whom an arrhythmic cause was found. Severe anticipated device related complications occurred in three patients. CONCLUSION: An implantable loop recorder is useful for establishing a diagnosis when symptoms are recurrent but too infrequent for conventional monitoring techniques.  相似文献   
45.
46.
Over the years, olive mill wastewater (OMW), which is generated from olive oil production has attracted considerable attention as one of the most polluted wastewaters due to its high concentrations of toxic compounds. It is a truism nowadays to guide research towards a novel and efficient technologies in order to treat this hazardous waste.In this paper, detoxification of OMW in an external loop airlift reactor (ALR) by electrocoagulation (EC) powered by photovoltaic solar system as a renewable and sustainable energy source was investigated. The effects of the operating parameters, such as electrolysis time, initial pH, current density (CD), and the axial position of the electrode were studied in continuous flow with two aluminum electrodes. A rate of abatement of about 79.24% for COD, 94.82% for polyphenols and 97.87% for dark color was observed within 40 min of treatment at 32.14 mA/cm2 current density, a position of the electrodes at 35 cm from the bottom of the riser compartment, and initial pH of 5.6. Furthermore, under these optimal conditions, the power supplied by photovoltaic cells led to amount of electrode dissolved (ELC) and specific energy consumption (SEC) of around 0.1118 kg/m3 and 9.86 kWh/m3, respectively. It has been proven that the EC treatment of OMW in ALR coupled with renewable energy source offers a low operation cost (0.2 USD/m3) compared to other treatment processes.  相似文献   
47.
It has been demonstrated that the immunodominant V3 loop of HIV-1 gp120 and its flanking regions bear sequence and structural homology to the framework and complementarity-determining regions of human immunoglobulins. It has been proposed that the Ig-like domain of gp120 might encode idiotypes and in this way permit HIV-1 entry into the immune regulatory network. This notion is strongly supported by results demonstrating that the anti-V3 loop and anti-Ig antibodies of healthy individuals share complementary structure and that V3 reactive antibodies are present in HIV-negative sera. This might be the mechanism by which HIV induces immunological abnormalities, and it should be taken into consideration in AIDS vaccine development.  相似文献   
48.
49.
Implantable left ventricular assist devices (LVADs) have been adapted clinically for right‐sided mechanical circulatory support (RVAD). Previous studies on RVAD support have established the benefits of outflow cannula restriction and rotational speed reduction, and recent literature has focused on assessing either the degree of outflow cannula restriction required to simulate left‐sided afterload, or the limitation of RVAD rotational speeds. Anecdotally, the utility of outflow cannula restriction has been questioned, with suggestion that banding may be unnecessary and may be replaced simply by varying the outflow conduit length. Furthermore, many patients have a high pulmonary vascular resistance (PVR) at the time of ventricular assist device (VAD) insertion that reduces with pulmonary vascular bed remodeling. It is therefore important to assess the potential changes in flow through an RVAD as PVR changes. In this in vitro study, we observed the use of dual HeartWare HVAD devices (HeartWare Inc., Framingham, MA, USA) in biventricular support (BiVAD) configuration. We assessed the pumps' ability to maintain hemodynamic stability with and without banding; and with varying outflow cannulae length (20, 40, and 60 cm). Increased length of the outflow conduit was found to produce significantly increased afterload to the device, but this was not found to be necessary to maintain the device within the manufacturer's recommended operational parameters under a simulated normal physiological setting of mild and severe right ventricular (RV) failure. We hypothesize that 40 cm of outflow conduit, laid down along the diaphragm and then up over the RV to reach the pulmonary trunk, will generate sufficient resistance to maintain normal pump function.  相似文献   
50.
BACKGROUND: The heterogeneity of ventricular repolarization is an important proarrhythmic factor. QT dispersion has been proposed to reflect the inhomogeneity of ventricular repolarization, but a poor reproducibility limits its clinical applicability. Reliable noninvasive methods to quantify abnormalities in ventricular repolarization are still lacking. The T-loop morphology analysis is a novel method aimed at quantifying ventricular repolarization. HYPOTHESIS: To test the ability of the T-loop morphology analysis to discriminate between hypertensive patients and healthy subjects, 105 hypertensive patients (mean age 63.6 +/- 12.3 years) and 110 healthy controls (mean age 49.7 +/- 14.3 years) were evaluated. METHODS: The maximum QT interval (QT maximum), the minimum QT interval (QT minimum), and their difference (QT dispersion) were calculated from a digitally recorded 12-lead electrocardiogram (ECG) in both study groups. X, Y, and Z leads were reconstructed from the 12-lead ECG, and the amplitude of the maximum T vector (T amplitude) and the angle between the maximum T vector and X axis (T angle) were calculated from the projection of the T loop in the frontal plane. RESULTS: T amplitude (p < 0.001), T angle (p = 0.05), and QT dispersion (p = 0.04) were significantly different between hypertensive patients and controls, while QT maximum (p = 0.14) and QT minimum (p = 0.35) did not differ between the groups. T amplitude was the only marker which differed between hypertensive patients without ECG criteria for left ventricular hypertrophy and controls (p = 0.002). CONCLUSIONS: T-loop features and particularly T amplitude are significantly different between hypertensive patients and healthy controls and may serve as early markers of repolarization abnormalities in a hypertensive population.  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