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   34145篇
  免费   1987篇
  国内免费   120篇
耳鼻咽喉   476篇
儿科学   986篇
妇产科学   777篇
基础医学   4219篇
口腔科学   1577篇
临床医学   2513篇
内科学   8553篇
皮肤病学   783篇
神经病学   2848篇
特种医学   814篇
外科学   5382篇
综合类   253篇
一般理论   10篇
预防医学   2656篇
眼科学   797篇
药学   1798篇
  2篇
中国医学   132篇
肿瘤学   1676篇
  2024年   100篇
  2023年   239篇
  2022年   517篇
  2021年   1158篇
  2020年   642篇
  2019年   1030篇
  2018年   1186篇
  2017年   773篇
  2016年   786篇
  2015年   971篇
  2014年   1369篇
  2013年   1665篇
  2012年   2538篇
  2011年   2632篇
  2010年   1534篇
  2009年   1308篇
  2008年   2137篇
  2007年   2258篇
  2006年   2043篇
  2005年   1951篇
  2004年   1708篇
  2003年   1489篇
  2002年   1438篇
  2001年   531篇
  2000年   528篇
  1999年   474篇
  1998年   289篇
  1997年   217篇
  1996年   168篇
  1995年   153篇
  1994年   136篇
  1993年   116篇
  1992年   237篇
  1991年   204篇
  1990年   184篇
  1989年   174篇
  1988年   119篇
  1987年   123篇
  1986年   105篇
  1985年   96篇
  1984年   84篇
  1983年   79篇
  1982年   66篇
  1981年   60篇
  1980年   42篇
  1979年   56篇
  1978年   52篇
  1977年   43篇
  1973年   49篇
  1972年   39篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Annals of Surgical Oncology - The liver-first approach in patients with synchronous colorectal liver metastases (CRLM) has gained wide consensus but its role is still to be clarified. We aimed to...  相似文献   
102.
BACKGROUND CONTEXTManual contouring of spinal rods is often required intraoperatively for proper alignment of the rods within the pedicle screw heads. Residual misalignments are frequently reduced by using dedicated reduction devices. The forces exerted by these devices, however, are uncontrolled and may lead to excessive reaction forces. As a consequence, screw pullout might be provoked and surrounding tissue may experience unfavorable biomechanical loads. The corresponding loads and induced tissue deformations are however not well identified. Additionally, whether the forced reduction alters the biomechanical behavior of the lumbar spine during physiological movements postoperatively, remains unexplored.PURPOSETo predict whether the reduction of misaligned posterior instrumentation might result in clinical complications directly after reduction and during a subsequent physiological flexion movement.STUDY DESIGNFinite element analysis.METHODSA patient-specific, total lumbar (L1–S1) spine finite element model was available from previous research. The model consists of poro-elastic intervertebral discs with Pfirrmann grade-dependent material parameters, with linear elastic bone tissue with stiffness values related to the local bone density, and with the seven major ligaments per spinal motion segment described as nonlinear materials. Titanium instrumentation was implemented in this model to simulate a L4, L5, and S1 posterolateral fusion. Next, coronal and sagittal misalignments of 6 mm each were introduced between the rod and the screw head at L4. These misalignments were computationally reduced and a physiological flexion movement of 15° was prescribed. Non-instrumented and well-aligned instrumented models were used as control groups.RESULTSPulling forces up to 1.0 kN were required to correct the induced misalignments of 6 mm. These forces affected the posture of the total lumbar spine, as motion segments were predicted to rotate up to 3 degrees and rotations propagated proximally to and even affect the L1–2 level. The facet contact pressures in the corrected misaligned models were asymmetrical suggesting non-physiological joint loading in the misaligned models. In addition, the discs and vertebrae experienced abnormally high forces as a result of the correction procedure. These effects were more pronounced after a 15° flexion movement following forced reduction.CONCLUSIONSThe results of this study indicate that the correction of misaligned posterior instrumentation can result in high forces at the screws consistent with those reported to cause screw pullout, and may cause high-tissue strains in adjacent and downstream spinal segments.CLINICAL SIGNIFICANCEProper alignment of spinal posterior instrumentation may reduce clinical complications secondary to unfavorable biomechanics.  相似文献   
103.
104.
Pseudoangiosarcomatous squamous cell carcinoma, also called pseudovascular, pseudoangiomatoid or adenoid pseudovascular carcinoma, is an uncommon and highly aggressive variant of squamous cell carcinoma. Histologically, it is characterized by proliferation of atypical keratinocytes with acantholysis and formation of pseudovascular spaces, forming anastomosed channels lined with neoplastic cells that invade the dermis. These cells are positive for cytokeratin and negative for vascular markers such as CD31 and CD34. There are few reports of this variant in the literature. Skin, breast, lung and vulva involvement have been described, but to the best of our knowledge, no cases involving the penis has been described. This study aims to describe the first case of angiosarcomatous squamous cell carcinoma of the penis. The patient presented with a painful lesion in the penis associated with urinary retention. Macroscopic findings exhibited an ulcerative vegetating lesion that involving the entire glans and part of the penile body, as well as infiltration of penile structures and scrotal skin. Microscopy shows atypical proliferation of sarcomatous keratinocyte pattern mimicking vascular spaces. Human papilloma virus (HPV) biomarkers and polymerase chain reaction (PCR) were all negative. Advanced penile squamous cell carcinoma with aggressive lymph node metastasis. This report presents the first case of penile pseudoangiosarcomatous squamous cell carcinoma, as an important differential diagnosis.  相似文献   
105.
106.
Local anaesthesia for fibreoptic bronchoscopy should be given by a safe technique that is not unpleasant to the patient and should provide acceptable conditions for the bronchoscopist. Single injection transcricoid local anaesthesia was compared with the "spray as you go" technique in patients having day case fibreoptic bronchoscopy. Patients were randomised to receive either 100 mg lignocaine by a single cricothyroid puncture or 240 mg lignocaine instilled through the bronchoscope under direct vision. Further doses were given by the operator to both groups as required. The 30 patients receiving transcricoid lignocaine coughed less (3.56 (SD 3.1) coughs/min) than the 32 patients receiving lignocaine through the bronchoscope (5.89 (4.8)/min) despite receiving a lower total dose of lignocaine (322 (25.9) v 451 (20.9) mg). Cricothyroid puncture was not associated with any complications and was not unpleasant for the patients.  相似文献   
107.
Bill 7, the most recent amendment to the Ontario Mental Health Act was introduced in December 1986. It has resulted in some major changes to the practice of psychiatry, especially in provincial hospitals. We compared patients who had discharged themselves against medical advice (AMA) during the six months before the Bill was enacted, with those who discharged themselves AMA in the 12 months following. Significantly more patients discharged themselves AMA in the post- than the pre-Bill period. The majority of these were potentially treatable, acutely ill individuals with schizophrenia or affective disorder. We argue that Bill 7 has largely failed in its objective to improve the overall "quality of care" to psychiatric patients, at least in the short term.  相似文献   
108.
This paper deals with the study of 927 patients of both sexes, with multiprogramable pacemakers implanted during 1987-1988 period, at the "Comandante Manuel Fajardo" Teaching Hospital and the Institute of Cardiology and Cardiovascular Surgery. Complications accounted for 14.9% and the most frequent were, in decreasing order, as follows: sepsis of the pocket (46.7%), hematoma of the pocket, increased threshold and, in a lower percentage, aseptic necrosis (5.7%). Emphasis is made in the role of the nurse in front of a patient with pacemaker and of the different complications presented.  相似文献   
109.
Purpose To characterize and predict cycles generating slowcleaving embryos in in vitro fertilization, 86 cycles were retrospectively divided into two groups (slow, n=41, and fast, n=45 according to whether the number of blastomeres per embryo on day 3 was or > than the mean of the distribution, respectively.Results Cycles generating slowcleaving embryos were treated with luteinizing hormonereleasing hormone agonist before ovarian stimulation for a shorter period (12.1±0.5 versus 15.6±1.1 days; P0.01) and had higher immaturity grade of oocyte-corona-cumulus complexes which resulted in embryos (1.6±0.1 vs 1.3±0.1; P0.05) when compared to cycles producing fastcleaving embryos. Both variables entered in a logistic regression model applied in order to predict the probability of a cycle generating slowcleaving embryos (goodness-of-fit chisquare=180.0, degrees of freedom (df)=80, P=0.4786. This model predicted correctly 86.7% (13 of 15) of cycles generating slowcleaving embryos and 83.3% (10 of 12) of cycles producing fastcleaving embryos when the estimated probability of a cycle producing slowcleaving embryos was 0.7 or 0.3, respectively.Conclusion Shorter treatment with hormone-releasing hormone agonist before ovarian stimulation and higher immaturity grade of oocyte-corona-cumulus complexes which result in embryos are predictive characteristics of in vitro fertilization cycles generating slow-cleaving embryos.  相似文献   
110.
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