首页 | 官方网站   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   37080篇
  免费   2874篇
  国内免费   1100篇
医药卫生   41054篇
  2024年   63篇
  2023年   445篇
  2022年   1007篇
  2021年   1558篇
  2020年   989篇
  2019年   1091篇
  2018年   1258篇
  2017年   1008篇
  2016年   1113篇
  2015年   1523篇
  2014年   1869篇
  2013年   1876篇
  2012年   2864篇
  2011年   2814篇
  2010年   1761篇
  2009年   1486篇
  2008年   1932篇
  2007年   1936篇
  2006年   1937篇
  2005年   1815篇
  2004年   1478篇
  2003年   1298篇
  2002年   1129篇
  2001年   971篇
  2000年   892篇
  1999年   796篇
  1998年   404篇
  1997年   350篇
  1996年   255篇
  1995年   267篇
  1994年   196篇
  1993年   161篇
  1992年   262篇
  1991年   262篇
  1990年   208篇
  1989年   199篇
  1988年   181篇
  1987年   195篇
  1986年   148篇
  1985年   136篇
  1984年   95篇
  1983年   84篇
  1982年   44篇
  1980年   44篇
  1979年   81篇
  1977年   49篇
  1974年   54篇
  1973年   49篇
  1972年   46篇
  1969年   51篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
During bone development and repair, angiogenesis, osteogenesis, and bone remodeling are closely associated processes that share some common mediators. In the present study nonadherent human bone marrow mononuclear cells under the induction of sRANKL and M-CSF, differentiated into osteoclasts with TRAP-positive staining, VNR expression, and Ca-P resorptive activity. The effects of various combinations of rhBMP-2 (0, 3, 30, and 300 ng/mL) and rhVEGF (0 and 25 ng/mL) on osteoclastogenesis potentials were examined in this experimental system. The percentages of TRAP-positive multiple nucleated cells represent osteoclast differentiation potential, and the percentages of resorptive areas in the Ca-P coated plates resemble osteoclast resorption capability. The presence of rhBMP-2 at 30 and 300 ng/mL showed inhibitory effects on osteoclast differentiation and their resorptive capability in the human osteoclast culture system. rhVEGF (25 ng/mL) enhanced the resorptive function of osteoclast whenever it was used alone or combined with 3 ng/mL rhBMP-2. However, rhVEGF-induced resorptive function was inhibited by 30 ng/mL and 300 ng/mL rhBMP-2 in a dose-dependent manner. Statistical analysis demonstrated that an interactive effect exists between rhBMP-2 and rhVEGF on human osteoclastogenesis. These findings suggested that an interactive regulation may exist between BMPs and VEGF signaling pathways during osteoclastogenesis; exact mechanisms are yet to be elucidated.  相似文献   
52.
目的观察无抽搐电痉挛(Modified Electrocnvulsive therapy,MECT)治疗精神分裂症的疗效及给予次数的关系。方法将60例诊断为精神分裂症的住院患者按治疗次数随机分为两组,进行MECT的临床资料总结分析。结果治疗次数≥6次组,显效率为83.3%,次数〈6次组显效率为76.7%,两者显效率无显著性差异(P〉0.05),每组治疗前后BPRS评分有显著差异,但两组间比较无显著差异(P〉0.05),未发现严重不良反应。结论MECF安全性高,有一定疗效,与治疗次数关系不大。  相似文献   
53.
4 cases of syringomyelia with type I Arnold Chiari malformation was seen presenting mainly with dissociated sensory loss, weakness of hands and upper motor neurone signs in the lower limbs. The first patient improved with posterior fossa decompression. The second and fourth patient appeared not to have improved after surgery, and the third case refused operation. One patient showed cord atrophy on myelogram presumably due to a collapse of the syrinx. One of the patients was unusual in that the syrinx extended down to segment T11. Magnetic resonance imaging of the posterior fossa and the cervical cord, to date, is the most useful procedure for diagnosis.  相似文献   
54.
采用180只成年小白鼠(雌雄各半),其中168只经一次总剂量为4Gy的~(60)Co—γ射线照射,造成造血放射损伤,再从其中随机选出56只膜腔注射刺五加注射液作为实验用药组,其余小白鼠随机分为盐水对照组(56只),空白对照组(56只)及正常对照组(12只)。实验结果显示。实验用药组的胸腺细胞超微结构的恢复比同期对照组快,胸腺组织DNA含量比同期对照组高。因此,我们认为刺五加可促进辐射损伤后小白鼠胸腺细胞结构的恢复。  相似文献   
55.
肋骨骨折与肺挫伤   总被引:2,自引:0,他引:2  
本文总结48例肋骨骨折合并肺挫伤。其中43例为多根多处肋骨骨折伴肺挫伤.5例为单处骨折伴肺挫伤。临床资料表明多根多处肋骨骨折(连枷胸)的伤员之呼吸窘迫症状并不经常和肋骨骨折数目成正比。连枷胸所见的呼吸窘迫,低氧血症及肺内分流增加。主要是肺挫伤导致的肺实质性损害引起,而非胸壁反常运动造成。早期充分的止痛是有效的治疗方法。  相似文献   
56.
作者对632例强直性脊柱炎并驼背畸形施行二种脊柱截骨矫治术,对其中135例病人进行了6~10年观察,结果表明:71例椎弓椎体联合截骨效果较好,驼背复发平均3.2°。而64例椎板截骨效果略差,驼背平均复发13.5°。经统计学处理,两者对比有显著的统计学意义(p<0.01)。作者认为病变未完全静止,截骨术式的选择,术中身体重心前移未彻底纠正,以及外固定时间过短等是影响远期效果的因素。  相似文献   
57.
Maintenance of the body's perfusion by a total artificial heart (TAH) may result in physiological alterations to the circulatory system. Little has been said about modifications to systemic vascular resistances (SVR) during TAH assistance. This paper reports on two patients implanted with a Jarvik - 70 cc TAH, who died after 1 and 3 days, both with an irreversible drop of SVR related to a complete loss of vascular tone but not related to sepsis. Activation of multiple cascades of inflammation, triggered by the extracorporeal circulation (ECC), is maintained during TAH support. Desperately sick patients might not be able to face the vaso-active situations created by the inflammatory response.  相似文献   
58.
79只眼底病患眼的光照黄斑部试验(MPT)结果显示:中心性浆液性脉络膜视网膜病变、老年性黄斑变性渗出型和Rieger型中心性渗出性脉络膜视网膜病变患眼的光照黄斑恢复时间显著延长,其它黄斑部病变患眼也有不同程度的延长。本文结合眼底荧光血管造影和黄斑视野域值试验对光照黄斑部试验的机理进行了探讨。  相似文献   
59.
BACKGROUND CONTEXT: In patients with spinal osteoporosis, the early achievement and maintenance of a biological bond between the pedicle screw and bone is important to avoid screw loosening complications. There are few reports of in vivo investigations involving biomechanical and histological evaluations in the osteoporotic spine. PURPOSE: To evaluate the effect of hydroxyapatite (HA)-coating on the pedicle screw in the osteoporotic lumbar spine and to investigate the relationship between resistance against the screw pull-out force and bone mineral density (BMD) of the vertebral body. STUDY DESIGN/SETTING: Mechanical and pathological investigations in the lumbar spine. METHODS: Two 24-month-old female beagle dogs were fed a calcium-free dog chow for 6 months after ovariectomy (OVX). BMD (in g/cm2) was measured by dual energy X-ray absorptiometry at pre-OVX and 6 months after OVX. Pedicle screws were placed from L1 to L6 at 6 months after OVX. Twenty-four pure titanium cortical screws (Synthes, #401-114) were used as pedicle screws (Ti-PS). Of these, 12 screws had HA-coating (HA-PS). The HA-PS screws were inserted into the right pedicles and the Ti-PS were inserted into the left pedicles. Ten days after this procedure, the lumbar spines were removed en bloc for screw pull-out testing and histological evaluation. RESULTS: The mean BMD value of the lumbar vertebrae 6 months after the OVX was 0.549+/-0.087 g/cm2, which was significantly less than the pre-OVX mean BMD of 0.603+/-0.092 g/cm2 (p < 0.001). The mean resistance against the pull-out force for the HA-PS was significantly greater at 165.6+/-26.5N than in the Ti-PS (103.1+/-30.2N, p < .001). The histological sections in the HA-PS clearly revealed new bone bonding with the apatite coating but only fibrous tissue bonding in the Ti-PS. CONCLUSIONS: The results of this study showed that the resistance to the pull-out force of HA-PS is 1.6 times that of Ti-PS. Furthermore, HA-PS has superior biological bonding to the surrounding bone, as early as 10 days after surgery in this osteoporotic spine model. Thus, in patients with osteoporosis, coating of the pedicle screw with HA may provide better stability and bonding between the pedicle screw and bone in the early postoperative period.  相似文献   
60.
G1、G2引物是对问号钩体具有特异性引物。分别用G1或G2单引物对问号钩体中国参考株进行前4个低严格度循环的PCR扩增,扩增带谱显示赖型、犬型、致热型、秋季型、澳洲型、临海型、乌尔夫型、溶血型为一类,而爪哇型、拜伦型、波摩那型、七日热型、巴叶赞型塔拉索夫型、曼耗Ⅱ型是不与以上赖型等血清型本为一类,双曲钩体atoc型及伊利尼细丝体伊利尼型的扩增带谱与问号钩体截然不同。应用苯酚法提取的高纯度钩体DNA  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-23

京公网安备 11010802026262号