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   82594篇
  免费   5815篇
  国内免费   650篇
耳鼻咽喉   856篇
儿科学   1927篇
妇产科学   1233篇
基础医学   11262篇
口腔科学   1595篇
临床医学   8312篇
内科学   18009篇
皮肤病学   1740篇
神经病学   8180篇
特种医学   3770篇
外国民族医学   16篇
外科学   12336篇
综合类   1574篇
现状与发展   1篇
一般理论   15篇
预防医学   4910篇
眼科学   1319篇
药学   5484篇
  6篇
中国医学   689篇
肿瘤学   5825篇
  2023年   697篇
  2022年   1327篇
  2021年   2471篇
  2020年   1504篇
  2019年   2096篇
  2018年   2453篇
  2017年   1866篇
  2016年   2070篇
  2015年   2446篇
  2014年   3105篇
  2013年   3913篇
  2012年   6034篇
  2011年   6068篇
  2010年   3663篇
  2009年   3196篇
  2008年   4929篇
  2007年   5062篇
  2006年   4728篇
  2005年   4571篇
  2004年   4058篇
  2003年   3883篇
  2002年   3542篇
  2001年   1546篇
  2000年   1427篇
  1999年   1368篇
  1998年   818篇
  1997年   655篇
  1996年   545篇
  1995年   430篇
  1994年   424篇
  1993年   337篇
  1992年   655篇
  1991年   626篇
  1990年   571篇
  1989年   521篇
  1988年   545篇
  1987年   441篇
  1986年   444篇
  1985年   434篇
  1984年   355篇
  1983年   266篇
  1982年   193篇
  1981年   160篇
  1979年   257篇
  1978年   158篇
  1977年   174篇
  1976年   158篇
  1975年   144篇
  1974年   175篇
  1972年   151篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
背景:Parkin基因(PRKN)突变可导致常染色体隐性遗传性早发帕金森病(EOPD)。目的:探讨EOPD白人家族PRKN突变的表现和基因型-表型关系。设计:对EOPD家族的3代20例成员进行基因分析,该家族有4例患者。应用直接基因组DNA测序、半定量聚合酶链反应、实时定量聚合酶链反应以及逆转录酶聚合酶链反应分析以确定PRKN突变。结果:4例早发患者(年龄30—38岁)被确定有PRKN复合杂合突变(T240M和EX5_6缺失),虽然PRKN的杂合T240M和纯合EX5_6缺失突变已有描述,但是据悉,本文为上述复合杂合突变的首次报道。患者的表型为典型常染色体隐性遗传性EOPD的表现,其特征是对左旋多巴治疗有效、相对缓慢的进展和运动障碍。所有杂合突变的基因携带者(T240M或EX5_6缺失)和1例56岁的复合杂合突变女性携带者(T240M和EX5_6缺失)无任何神经系统症状。结论:研究发现,PRKN基因复合杂合突变(T240M和EX5_6缺失)导致一个大的白人家族中4例成员发生常染色体隐性遗传性EOPD。另外1例成员具有相同的突变,比4例患者的平均发病年龄大10岁,并且无本病的临床表现。不完全的外显率对遗传咨询具有暗示作用,并且提示复杂的基因一环境交互作用在PRKN相关EOPD的发病机制中发挥作用。  相似文献   
52.
BACKGROUND/AIMS: The purpose of this work was to develop a new sensor for objective in vivo measurement of the cutaneous temperature based on micro-electro-mechanical systems (MEMS), and to compare these performances with those of a classical thermocouple. Research on this new sensor was carried out to allow the quantification of the thermal properties of the made-up skin. METHODS: Sixteen female subjects divided into two different age groups (18-35 and >50 years old) were recruited for this study. Several zones of the face and forearms were made up at random with foundations containing or not a thermoregulator raw material. The quantity of foundation applied on the skin was standardized and measurements were carried out first before make-up, and then 10 s and 5 min after make-up. The new sensor and the thermocouple were used successively on each zone. The cutaneous temperature was expressed in degrees celsius. RESULTS/CONCLUSION: The two systems are similar in terms of repeatability and reproducibility, with some differences in sensibility. The data measured by the MEMS sensor appear lower than those measured by the thermocouple. After make-up, the MEMS sensor detects a progressive increase of the temperature in time whereas the thermocouple detects a decrease. We found the same evolution on the face but in a more attenuated way. These results tend to show that the devices do not measure the same phenomenon. The thermocouple appears more sensitive to the thermal response of the made-up surface whereas the MEMS sensor appears more sensitive to the heat transfers in the interface between the skin and make-up.  相似文献   
53.
Genetically modified keratinocytes and fibroblasts are suitable for delivery of therapeutic genes capable of modifying the wound healing process. However, efficient gene delivery is a prerequisite for successful gene therapy of wounds. Whereas adenoviral vectors (Ads) exhibit superior levels of in vivo gene transfer, their transductional efficiency to cells resident within wounds may nonetheless be suboptimal, due to deficiency of the primary adenovirus receptor, coxsackie-adenovirus receptor (CAR). We explored CAR-independent transduction to fibroblasts and keratinocytes using a panel of CAR-independent fiber-modified Ads to determine enhancement of infectivity. These fiber-modified adenoviral vectors included Ad 3 knob (Ad5/3), canine Ad serotype 2 knob (Ad5CAV-2), RGD (Ad5.RGD), polylysine (Ad5.pK7), or both RGD and polylysine (Ad5.RGD.pK7). To evaluate whether transduction efficiencies of the fiber-modified adenoviral vectors correlated with the expression of their putative receptors on keratinocytes and fibroblasts, we analyzed the mRNA levels of CAR, alpha upsilon integrin, syndecan-1, and glypican-1 using quantitative polymerase chain reaction. Analysis of luciferase and green fluorescent protein transgene expression showed superior transduction efficiency of Ad5.pK7 in keratinocytes and Ad5.RGD.pK7 in fibroblasts. mRNA expression of alpha upsilon integrin, syndecan-1 and glypican-1 was significantly higher in primary fibroblasts than CAR. In keratinocytes, syndecan-1 expression was significantly higher than all the other receptors tested. Significant infectivity enhancement was achieved in keratinocytes and fibroblasts using fiber-modified adenoviral vectors. These strategies to enhance infectivity may help to achieve higher clinical efficacy of wound gene therapy.  相似文献   
54.
BACKGROUND: Despite major improvement in surgical techniques and intensive care management, stroke remains one of the most devastating complications of coronary artery bypass grafting (CABG). We aimed to determine factors predicting the occurrence of stroke during CABG. A special interest was focused on preoperative therapies. METHODS: We prospectively enrolled 810 consecutive candidates for CABG alone in a specific database, including all pre- and perioperative data (history, clinical, therapeutic, cardiac catheterization, surgical and intensive care data). Univariate tests and then multiple logistic regression analysis were used to determine independent predictive factors. RESULTS: During the first postoperative month, stroke occurred in 11 cases and transient ischemic attack (TIA) in 4 additive cases (cumulative rate: 1.85%). After the multivariate analysis, the following factors remained significant (p<0.05) in the predictive model, with corresponding odds ratios between brackets: redo cardiac surgery (7.45), unstable cardiac status (4.74), past history of cerebrovascular disease (4.14), past history of peripheral arterial disease (3.55), whereas the presence of preoperative statins was protective (0.24, 95% IC: 0.07-0.78). The addition of perioperative data (aortic calcification, postoperative arrhythmia, on/off-pump surgery) did not change the final predictive model. CONCLUSION: To our knowledge, this is the first real-world observational report highlighting the interest of statins for the prevention of stroke in the very special situation of CABG. Even though according to randomized trials coronary patients have a benefit from these drugs, a special level of interest should be directed towards those presenting the above-mentioned risk factors.  相似文献   
55.
Abstract Background: Does there exist a difference in the outcome of severely injured children and severely injured healthy adults? Methods: The data of 1,566 severely injured patients, treated between May 1998 and December 2002 in our emergency department of the University Essen/Germany, were analyzed. Patients with an injury severity score (ISS) > 24 were included in the present study. Patients younger as 18 (17) years were located to the children group c. Patients aged 18 and up to the age of 54 were included in the adult group a. Results: Fifty-four children and 252 adults met the selection criteria. ISS and the Glasgow coma scale (GCS) before intubation were not statistically different in both groups. Seriously injured children stayed significantly shorter on the intensive care unit, required significantly less ventilator days. Furthermore, the incidence of single organ failure (SOF) and multiple organ failure (MOF) was significantly lower in the children group. Mortality in the children group (29.6%) was lower than that in the adult group (33.7%). There was no death due to MOF in the children group as compared to 2.4% (n = 6) in the adults. Conclusion: The incidence of SOF and MOF was significantly lower in the children group although there was no difference in ISS, GCS and injury patterns. The prognosis of severely injured children was found to be better than those of adults. Moreover, there was no death due to MOF in the children group.  相似文献   
56.
57.
Whereas decubitus ulcer in the back or hip region is a common entity in plegic or elderly patients, the occurrence in the lateral shoulder region is seldom seen. However, resulting from continuous lateral decubitus positioning or limited compliance by the patient, pressure sores may occur in almost any region of the body, but predominately, they arise in acral zones with underlying bone prominences. The deltoid area is such an anatomically critical region, especially if the underlying deltoid muscle is paralyzed. The transposition of a pedicled deltoid flap, slightly modified as a hatchet flap, is described for cover of a decubitus ulcer in the deltoid region in a paraplegic male. Although utilization of the deltoid flap as a free flap is an established procedure for selected indications [Russell et al. (1985) Extremity reconstruction using the free deltoid flap. Plast Reconstr Surg 76:586–595, Serafin D (1996) The deltoid flap. In: Serafin D (ed) Atlas of microsurgical composite tissue transplantation, chapter 19. Saunders, Philadelphia, PA, pp 153–159, Wang et al. (2003) The free deltoid flap: microscopic anatomy studies and clinical application to oral cavity reconstruction. Plast Reconstr Surg 112:404–411], transposition as a pedicled flap, to the best of our knowledge, has not been previously described in the available literature.  相似文献   
58.
Nestin is an intermediate filament protein typical for neural precursor cells that is down-regulated in the post-natal rodent brain. Re-expression of nestin has been observed in reactive astrocytes after injury. In this study, organotypic slice cultures from rat cortex were examined for expression of nestin and glial fibrillary acidic protein between 2 and 8 weeks in culture. Immunoreactivity for nestin and glial fibrillary acidic protein was seen in astrocytes which persisted throughout the observation period. Immunofluorescence double labeling showed widespread co-localization of nestin and glial fibrillary acidic protein. Image analysis revealed that levels of nestin-immunoreactivity plateaued after 5 weeks in culture. By comparison nestin immunoreactivity was absent from glial cells of the cortex in mature rats. These immunohistochemical findings of a persistent expression of nestin in glial cells of organotypic slice culture of the rat cortex indicate a different time course of glial maturation in vitro. This difference could be related to the altered trophic stimulation in vitro; differences in neuronal maturation, activity or survival; slow degeneration of the vasculature; or intrinsic properties of astrocytes.  相似文献   
59.
60.
Chronicsofttissuelesionisaspeciallymedicalterm,andanimportantpathologicalchangesofdiseases,suchaschronicoveruseinjuriesandconversionofacuteinjuriesinlowbackorfrominter-vertebraldiscprotrusion,anddislocationofintervertebraljointsaswell,whichmainlycauseseverepaininlowback犤1犦.Manypresentmethods(oralmedicine,massage,anestheticblock,physicalthera-piesetc.)havebeenusedforrelievingthepain,whichdemandsagreatfiscalsupportannually.Unfortunately,thereportsonthemechanismsandeffectofthem…  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