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   18891篇
  免费   1414篇
  国内免费   42篇
耳鼻咽喉   113篇
儿科学   575篇
妇产科学   517篇
基础医学   2748篇
口腔科学   355篇
临床医学   2140篇
内科学   3835篇
皮肤病学   352篇
神经病学   1940篇
特种医学   625篇
外科学   1784篇
综合类   165篇
现状与发展   1篇
一般理论   20篇
预防医学   2033篇
眼科学   286篇
药学   1442篇
中国医学   61篇
肿瘤学   1355篇
  2024年   21篇
  2023年   233篇
  2022年   301篇
  2021年   690篇
  2020年   472篇
  2019年   741篇
  2018年   725篇
  2017年   574篇
  2016年   567篇
  2015年   616篇
  2014年   810篇
  2013年   1052篇
  2012年   1677篇
  2011年   1581篇
  2010年   813篇
  2009年   771篇
  2008年   1249篇
  2007年   1251篇
  2006年   1047篇
  2005年   1111篇
  2004年   954篇
  2003年   822篇
  2002年   782篇
  2001年   143篇
  2000年   83篇
  1999年   117篇
  1998年   134篇
  1997年   123篇
  1996年   74篇
  1995年   74篇
  1994年   68篇
  1993年   57篇
  1992年   52篇
  1991年   44篇
  1990年   49篇
  1989年   34篇
  1988年   40篇
  1987年   51篇
  1986年   43篇
  1985年   33篇
  1984年   27篇
  1983年   21篇
  1982年   32篇
  1981年   24篇
  1978年   12篇
  1977年   13篇
  1975年   15篇
  1974年   12篇
  1973年   16篇
  1972年   12篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
921.
922.

Introduction

Despite its minimally invasive approach, laparoscopic surgery can cause considerable pain. Regional analgesic techniques such as the rectus sheath block (RSB) offer improved pain management following elective umbilical hernia repair in the pediatric population. This effect has not been examined in laparoscopic single-incision surgery in children. We sought to compare the efficacy of bilateral ultrasound-guided RSB versus local anesthetic infiltration (LAI) in providing postoperative pain relief in pediatric single-incision transumbilical laparoscopic assisted appendectomy (TULA) with same-day discharge.

Methods

We retrospectively reviewed 275 children, ages 4 to 17 years old, who underwent TULA for uncomplicated appendicitis in a single institution from August 2014 to July 2015. We compared those that received preincision bilateral RSB (n = 136) with those who received LAI (n = 139). The primary outcome was narcotic administration. Secondary outcomes included initial and mean scores, time from anesthesia induction to release, operative time, time to rescue dose of analgesic in the PACU and time to PACU discharge.

Results

Total narcotic administration was significantly reduced in patients that underwent preincision RSB compared to those that received conventional LAI, with a mean of 0.112 mg/kg of morphine versus 0.290 mg/kg morphine (p < 0.0001). Patients undergoing RSB reported lower initial (0.38 vs. 2.38; p < 0.0001) and mean pain scores (1.26 vs. 1.77; p < 0.015). Time to rescue analgesia was prolonged in patients undergoing RSB compared to LAI (58.93 min vs. 41.56 min; p = 0.047).

Conclusion

Preincision RSB for TULA in uncomplicated appendicitis in children is associated with decreased opioid consumption and lower pain scores compared with LAI. As the addition of this procedure only added 6.67 min to time under anesthesia, we feel that it is a viable option for postoperative pain control in pediatric single-incision laparoscopic surgery.

Retrospective comparative study

LEVEL III EVIDENCE.  相似文献   
923.

Background

The introduction of a combined-modality approach, which added chemotherapy to local therapy (surgery and radiotherapy), has been controversial. We present our experience of the efficacy of neoadjuvant chemotherapy in patients with high-risk sarcomas and evaluate the benefit of intra-arterial (IA) chemotherapy.

Patients and methods

Forty patients with intermediate to high-grade soft tissue sarcomas (STS) were treated with neoadjuvant chemotherapy from 1994 to 2001 at the Institut Curie. Thirty-seven patients had localized tumours. Neoadjuvant intravenous (IV) chemotherapy consisted of 4–6 cycles of treatment (mainly CYVADIC, MAID). Sixteen patients (40%) received 2 cycles of IA chemotherapy with a combination of adriamycin and cisplatin. Radiotherapy was delivered in an adjuvant setting.

Results

All patients underwent limb-sparing surgical resection after neoadjuvant therapy and pathologic assessment of tumour necrosis was performed on the resected specimens. Two groups of tumours were analysed: 1–95% (28 cases), and 95–100% (10 cases) of pathological necrosis, with a survival benefit in the group with more than 95% necrosis (p = 0.07). IA chemotherapy was superior to IV chemotherapy in terms of the necrosis rate (p = 0.045). With a median follow-up of 51 months, the 2-year overall survival rate was 90% for localized tumours.

Conclusion

Neoadjuvant chemotherapy can be considered to be effective in the treatment of STS. This study demonstrates the benefit of neoadjuvant therapy for patients with a high necrosis rate (very clear tendency) and the contribution of IA chemotherapy to the response rate, but with no survival advantage.  相似文献   
924.
925.

Microdeletions encompassing 14q11.2 locus, involving SUPT16H and CHD8, were shown to cause developmental delay, intellectual disability, autism spectrum disorders and macrocephaly. Variations leading to CHD8 haploinsufficiency or loss of function were also shown to lead to a similar phenotype. Recently, a 14q11.2 microduplication syndrome, encompassing CHD8 and SUPT16H, has been described, highlighting the importance of a tight control of at least CHD8 gene-dosage for a normal development. There have been only a few reports of 14q11.2 microduplications. Patients showed variable neurodevelopmental issues of variable severity. Breakpoints of the microduplications were non-recurrent, making interpretation of the CNV and determination of their clinical relevance difficult. Here, we report on two patients with 14q11.2 microduplication encompassing CHD8 and SUPT16H, one of whom had normal intelligence. Review of previous reports describing patients with comparable microduplications allowed for a more precise delineation of the condition and widening of the phenotypic spectrum.

  相似文献   
926.
927.
When circulating 17β estradiol (E2) is elevated to proestrous levels, hippocampus‐dependent learning and memory is enhanced in female rodents, nonhuman primates, and women due to heightened synaptic function at hippocampal synapses. We previously reported that proestrous‐like levels of E2 administered to young adult ovariectomized (OVX) female rats increases the magnitude of LTP at CA3 Schaffer collateral (SC)‐CA1 synapses only when dendritic spine density, the NMDAR/AMPAR ratio, and current mediated by GluN2B‐containing NMDA receptors (NMDARs) are simultaneously increased. We also reported that this increase in GluN2B‐mediated NMDAR current in area CA1 is causally related to the E2‐induced increase in novel object recognition, tying together heightened synaptic function with improved learning and memory. In addition to SC inputs, innervation from the entorhinal cortex in the temporoammonic (TA) pathway onto CA1 distal dendrites in stratum lacunosum‐moleculare is critical for spatial memory formation and retrieval. It is not known whether E2 modulates TA‐CA1 synapses similarly to SC‐CA1 synapses. Here, we report that 24 hours post‐E2 injection, dendritic spine density on CA1 pyramidal cell distal dendrites and current mediated by GluN2B‐containing NMDARs at TA‐CA1 synapses is increased, similarly to our previous findings at SC‐CA1 synapses. However, in contrast to SC‐CA1 synapses, AMPAR transmission at TA‐CA1 synapses is significantly increased, and there is no effect on the LTP magnitude. Pharmacological blockade of GluN2B‐containing NMDARs or ERK activation, which occurs downstream of synaptic but not extrasynaptic GluN2B‐containing NMDARs, attenuates the LTP magnitude only in slices from E2‐treated rats. These data show that E2 recruits a causal role for GluN2B‐containing NMDARs and ERK signaling in the induction of LTP, cellular mechanisms not required for LTP induction at TA‐CA1 synapses in vehicle‐treated OVX female rats. © 2015 Wiley Periodicals, Inc.  相似文献   
928.
Several studies indicate that the cerebellum might play a role in experiencing and/or controlling emphatic emotions, but it remains to be determined whether there is a distinction between positive and negative emotions, and, if so, which specific parts of the cerebellum are involved in these types of emotions. Here, we visualized activations of the cerebellum and extracerebellar regions using high-field fMRI, while we asked participants to observe and imitate images with pictures of human faces expressing different emotional states or with moving geometric shapes as control. The state of the emotions could be positive (happiness and surprise), negative (anger and disgust), or neutral. The positive emotional faces only evoked mild activations of crus 2 in the cerebellum, whereas the negative emotional faces evoked prominent activations in lobules VI and VIIa in its hemispheres and lobules VIII and IX in the vermis. The cerebellar activations associated with negative emotions occurred concomitantly with activations of mirror neuron domains such as the insula and amygdala. These data suggest that the potential role of the cerebellum in control of emotions may be particularly relevant for goal-directed behavior that is required for observing and reacting to another person’s (negative) expressions.  相似文献   
929.
The mirror system, comprising cortical areas that allow the actions of others to be represented in the observer's own motor system, is thought to be crucial for the development of social cognition in humans. Despite the importance of the human mirror system, little is known about its origins. We investigated the role of sensorimotor experience in the development of the mirror system. Functional magnetic resonance imaging was used to measure neural responses to observed hand and foot actions following one of two types of training. During training, participants in the Compatible (control) group made mirror responses to observed actions (hand responses were made to hand stimuli and foot responses to foot stimuli), whereas the Incompatible group made counter-mirror responses (hand to foot and foot to hand). Comparison of these groups revealed that, after training to respond in a counter-mirror fashion, the relative action observation properties of the mirror system were reversed; areas that showed greater responses to observation of hand actions in the Compatible group responded more strongly to observation of foot actions in the Incompatible group. These results suggest that, rather than being innate or the product of unimodal visual or motor experience, the mirror properties of the mirror system are acquired through sensorimotor learning.  相似文献   
930.
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