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   109134篇
  免费   9555篇
  国内免费   4726篇
耳鼻咽喉   1365篇
儿科学   1802篇
妇产科学   1750篇
基础医学   13359篇
口腔科学   2175篇
临床医学   12710篇
内科学   19789篇
皮肤病学   1865篇
神经病学   6450篇
特种医学   3922篇
外国民族医学   27篇
外科学   12106篇
综合类   12327篇
现状与发展   15篇
一般理论   14篇
预防医学   7744篇
眼科学   2559篇
药学   10484篇
  89篇
中国医学   4684篇
肿瘤学   8179篇
  2024年   291篇
  2023年   1397篇
  2022年   3342篇
  2021年   5623篇
  2020年   3999篇
  2019年   3781篇
  2018年   3994篇
  2017年   3555篇
  2016年   3293篇
  2015年   4814篇
  2014年   5927篇
  2013年   6317篇
  2012年   9239篇
  2011年   9575篇
  2010年   6195篇
  2009年   5161篇
  2008年   6558篇
  2007年   6399篇
  2006年   5769篇
  2005年   5332篇
  2004年   4049篇
  2003年   3771篇
  2002年   3099篇
  2001年   1591篇
  2000年   1491篇
  1999年   1463篇
  1998年   899篇
  1997年   857篇
  1996年   699篇
  1995年   607篇
  1994年   531篇
  1993年   336篇
  1992年   478篇
  1991年   359篇
  1990年   356篇
  1989年   316篇
  1988年   283篇
  1987年   241篇
  1986年   214篇
  1985年   171篇
  1984年   126篇
  1983年   109篇
  1982年   84篇
  1981年   101篇
  1980年   58篇
  1979年   77篇
  1978年   42篇
  1977年   54篇
  1976年   63篇
  1974年   39篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Carragee EJ  Han MY  Yang B  Kim DH  Kraemer H  Billys J 《Spine》1999,24(22):2346-2351
STUDY DESIGN: A prospective clinical trial was conducted. OBJECTIVES: To determine the feasibility of removing activity restrictions after surgery and encouraging early return to work; to ascertain the clinical and behavioral response to such a strategy; and to identify factors predictive of early return to work, preparatory to possible randomized clinical trials. SUMMARY OF BACKGROUND INFORMATION: Current practice usually entails several weeks to several months of restricted activities after lumbar discectomy to avoid disc "reinjury." Earlier work has suggested these restrictions may not be necessary. METHODS: One hundred fifty-two consecutive working patients undergoing limited open discectomy for herniated lumbar intervertebral disc were treated postoperatively with no activity restrictions. Patients were encouraged to return to full activities as soon as possible. The patients were followed for a minimum of 2 years (average follow-up time = 4.8 years). At follow-up, an independent examiner evaluated each patient and collected further postoperative data. RESULTS: One hundred forty-nine of the 152 patients (98%) returned to work. The average work loss was 1.2 weeks and 148 of 149 patients had returned to full duty by 8 weeks. Approximately one-third of the group returned to work within 1 week of surgery (32%), many the next day. Statistical analysis demonstrated very early return to work did not correlate with either recurrent sciatica, reoperation for reherniation, or ultimate clinical outcome. Seventeen patients (11.2%) had possible reherniations (recurrent sciatica) and eight underwent reoperation (5.3%). CONCLUSION: Lifting of postoperative activity restrictions after limited discectomy allowed shortened time to return to work relative to the 4 to 16 weeks commonly recommended. Complication rates appear comparable to those reported in the literature for patients under postoperative restrictions. Postoperative restrictions may not be necessary in most patients.  相似文献   
993.
Yuan Z  Ma P  Hu Y  Luo Z  Han Y  Shi K  Lu R  Wang J 《中华外科杂志》1999,37(11):682-685
目的 探讨复合基因重组人BMP2(rhBMP2)的异种骨与游离骨膜(FP)联合移植修复节段性骨缺损的效果。方法 将rhBMP2与去抗原牛松质骨载体(BCB)复合,制成rhBMP2/BCB;选用新西兰大耳白兔28只,制成烧骨干15mm缺损动物模型,分别行FP和rhBMP2/BCB复合移植(n=6)、rhBM2/BCB移植(n=6)和单纯BCB移植(n=2);术后4、8、12、16周取材,通过X线、生  相似文献   
994.
The preventive effects of green tea, tea pigments, and mixed tea (a composite of whole water extract of green tea, tea polyphenols, and tea pigments) on 7,12-dimethyl-benz[a]anthracene (DMBA)-induced oral carcinogenesis in golden Syrian hamsters were studied. The right buccal pouches of animals were topically treated with 0.5% DMBA three times per week for 15 weeks. Animals were killed separately after 6, 10, and 15 weeks of DMBA treatment. Oral tumors were counted and measured, and mean tumor burden was calculated. The incidence of preneoplastic lesions and micronucleated cells, the number and volume of silver-stained nucleolar organizer regions (AgNOR), the labeling index of proliferating cell nuclear antigen, and the level of epidermal growth factor receptor expression were studied. The results showed that oral administration of 1.5% green tea, 0.1% tea pigments, and 0.5% mixed tea as the sole source of drinking water for two weeks before initiation of the DMBA treatment and until the end of the experiment significantly reduced the mean tumor burden and the incidence of dysplasia and oral carcinoma (p < 0.01). The frequency of micronucleated cells, the number of AgNOR, the total volume of AgNORs, the labeling index of proliferating cell nuclear antigen, and the level of epidermal growth factor receptor expression in the oral mucosal cells were also significantly reduced (p < 0.01). These results clearly indicated that tea preparations could effectively inhibit DMBA-induced oral carcinogenesis in hamsters. Protection from DNA damage and suppression of cell proliferation could be important mechanisms of the anticarcinogenic effects of the tea preparations.  相似文献   
995.
上海市居民吸烟与癌症及有关疾病十年前瞻性研究   总被引:27,自引:0,他引:27  
目的探讨上海市民吸烟与癌症及有关疾病的关系。方法80年代初在上海市区、市郊和郊县开展了居民吸烟状况的横断面调查。至1994年年底,市区研究对象随访了12年,郊区研究对象随访了11年。本次研究分析了40岁以上研究对象的随访资料,并用Poison回归模型估计吸烟因素的年龄调整相对危险度及其95%可信区间。结果市区分析结果表明,男女性吸烟者全死因的相对危险度分别为1.48、1.62。而所有癌症死亡的相对危险度男性为2.20,女性为2.00。相对危险度有统计学意义的癌症部位是肺癌、肝癌、食管癌(男)、胃癌(男)、胰腺癌(男)、膀胱癌(男)。脑血管疾病、慢性支气管炎、肺气肿和肺心病的相对危险度也见显著升高。市郊和郊县的结果与市区类似。我们估计了三个地区吸烟对男性某些疾病的归因危险度(PAR),所有死因吸烟的PAR(%)三地分别为20.9、18.9、16.3,所有癌症三地吸烟的PAR(%)分别为40.0、34.5、34.2,肺癌三地吸烟的PAR(%)分别为71.7、59.2、64.7。结论吸烟与一些癌症、慢性阻塞性肺部疾病、肺原性心脏病及脑血管病等的死亡有关  相似文献   
996.
The clinical performance of the new Frameless IUD was compared with the TCu380A, the most widely used copper IUD in the world today. Insertions of the Frameless IUD were conducted with a prototype inserter (Flexigard). We report on the 6-year results from a randomized comparative clinical trial conducted at the Shanghai Institute of Planned Parenthood Research, as part of an international multicenter WHO clinical trial, involving 200 women, respectively recruited for use of each device. The cumulative 6-year pregnancy rates were 0.0 per 100 women for the Frameless IUD and 3.3 for TCu380A. Termination due to partial expulsion was significantly less for the Frameless IUD as compared with TCu380A (0.0 and 4.3 per hundred women, respectively). Complete expulsion, bleeding, pain, bleeding and pain and other medical reasons for termination did not differ significantly between the two devices. The net cumulative continuation rates at six years per 100 women were 80.8 for TCu380A, and 83.0 for the Frameless IUD.Both Frameless IUD and TCu380A are highly effective, safe and acceptable contraceptive devices, because of low pregnancy rates (per 100 women), and low termination rates due to expulsion, pain, bleeding, and bleeding and pain. Due to its anchoring, the Frameless IUD is significantly more effective than the TCu380A IUD as regards proper retention of the IUD in the uterine cavity. This may also explain its lower failure rate.  相似文献   
997.
王筱芬  韩明勇 《卫生研究》1999,28(3):181-182
以全胚胎培养模型结合免疫组化和电镜技术等探讨了乙酰水杨酸和叶酸对大鼠卵黄囊及胚胎的影响。结果表明:培养基含乙酰水杨酸300μg/ml组的卵黄囊直径和胚胎体长均显著低于阴性对照组,胚胎畸形率明显增高。组织学检查发现卵黄囊厚度变薄。间质层血岛、微血管数量明显减少,血管壁细胞不连续,血管发育不良。卵黄囊内皮层细胞顶端微绒毛少见。内皮层细胞的溶酶体、内质网及核蛋白体等结构和数量均有明显改变。而60mg/kg叶酸灌胃鼠血清与乙酰水杨酸联合应用后,则卵黄囊的上述毒性作用明显减轻或消失,提示叶酸能明显拮抗乙酰水杨酸致大鼠卵黄囊的毒性作用。  相似文献   
998.
内燃机车乘务员和轮轴工外周血淋巴细胞微核观察   总被引:1,自引:0,他引:1  
本文作者对51名内燃机车乘务员和车辆维修车间的30名轮轴工外周血淋巴细胞微核进行了分析。结果表明,机车乘务员和轮轴工微核阳性检出率、微核细胞率和微核率均明显高于对照组(P<0.01),而且随着作业工龄的延长,微核细胞率和微核率有接近显著(0.05<P<0.01)或显著(P<0.05)意义的增高。对两类作业工作人员微核增高的原因进行了讨论  相似文献   
999.
疝环充填无张力疝修补术(附50例报道)   总被引:2,自引:0,他引:2  
目的 观察疝环充填无张力疝修补术的临床应用效果。方法 疝囊做高位剥离而不做高位结扎,用美国Bard公司生产的锥形疝环充填 物充填内环,再用该公司生产的成型补片于精溃后方贴补腹肥肉沟管后壁,其它步骤同传统的手术方法。结果 本组50例,手术时间为30-770分钟,平均40分钟。随访1年效果良好,未见并发症。结论 疝环充填无张力疝修补术具有疼痛轻微、复发率低以及术后恢复快等优点。  相似文献   
1000.
人体双侧对称经络电阻抗失衡与疾病的相关研究   总被引:2,自引:0,他引:2  
通过实验装置.分别测量人体双侧对称经络对称两穴位之间的电流波形,计算其电阻抗值,探讨经络的导电特性。证明了正常人双侧经络电阻抗的对称性、经络循行线的低阻性及双侧经络电阻抗失衡与其络属脏器病变的相关性等问题。  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