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   973412篇
  免费   70876篇
  国内免费   1463篇
耳鼻咽喉   13519篇
儿科学   25526篇
妇产科学   23764篇
基础医学   138143篇
口腔科学   28720篇
临床医学   85171篇
内科学   191435篇
皮肤病学   19683篇
神经病学   76347篇
特种医学   38460篇
外国民族医学   79篇
外科学   159973篇
综合类   18380篇
现状与发展   2篇
一般理论   288篇
预防医学   65456篇
眼科学   22769篇
药学   75183篇
  3篇
中国医学   2196篇
肿瘤学   60654篇
  2021年   7442篇
  2019年   7489篇
  2018年   10810篇
  2017年   8339篇
  2016年   9068篇
  2015年   10317篇
  2014年   14076篇
  2013年   20049篇
  2012年   28073篇
  2011年   28950篇
  2010年   16870篇
  2009年   15985篇
  2008年   27327篇
  2007年   28563篇
  2006年   28909篇
  2005年   27622篇
  2004年   26497篇
  2003年   25232篇
  2002年   24566篇
  2001年   54969篇
  2000年   56768篇
  1999年   47164篇
  1998年   10991篇
  1997年   9665篇
  1996年   9747篇
  1995年   9058篇
  1994年   8383篇
  1993年   7684篇
  1992年   35605篇
  1991年   34014篇
  1990年   32812篇
  1989年   31949篇
  1988年   29068篇
  1987年   28344篇
  1986年   26363篇
  1985年   25240篇
  1984年   17914篇
  1983年   15196篇
  1982年   7856篇
  1979年   15828篇
  1978年   10644篇
  1977年   9086篇
  1976年   7899篇
  1975年   8660篇
  1974年   10501篇
  1973年   9883篇
  1972年   9384篇
  1971年   8875篇
  1970年   8447篇
  1969年   7940篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
New 2,5-dialkylpyrrolidines found in the venom of Monomorium indicum include trans-2-butyl-5-(4-pentenyl)pyrrolidine [1], trans-2-butyl-5-(6-heptenyl)pyrrolidine [4], trans-5-(5-hexenyl)-2-(4-pentenyl)pyrrolidine [6], trans-5-(6-heptenyl)-2-(5-hexenyl)pyrrolidine [8], and trans-5-heptyl-2-hexylpyrrolidine [16], whose structures were confirmed by synthesis. The concomitance of five previously reported trans-2,5-dialkyl-pyrrolidines along with small amounts of the cis isomers and N-methyl analogues makes the venom of M. indicum the most qualitatively diverse blend of alkaloids reported from an ant to date. The toxicities to termites of four of these alkaloids were determined.  相似文献   
992.
Forty samples of cord blood lymphocytes were isolated from 40 normal healthy full-term newborns. The initial 20 samples were used to determine the dose-response curve of three different thymic extracts (TP-1, bovine thymic extract; TG-15-I and TG-15-II, both porcine thymic extracts) and one of renal origin (KG-1) as a control of non-lymphoid organ extract, by measuring the E-rosette T cells. Results showed that E-rosette T cells increased significantly when the thymic extract concentration was increased to 12.5 micrograms/ml. However, there was no statistical difference between TP-1, TG-15-I and TG-15-II in the increase of E-rosette-forming cells. The remaining 20 samples were preincubated with 0, 12.5, 25 or 50 micrograms/ml of thymic extracts. It was observed that the lymphoproliferation, interleukin-2 (IL-2), gamma-interferon (IFN-gamma) and tumor necrotic factor (TNF) production were all significantly increased after thymic extract treatment. No statistical difference between these three thymic preparations in the stimulation of lymphoproliferative response was found. However, among the three thymic extracts, TP-1 appears to induce the highest amounts of IL-2, IFN-gamma and TNF. Of the TG-15-I and TG-15-II, the former stimulates higher IL-2 production whereas the latter enhances IFN-gamma and TNF production. The different immunostimulating effects and potencies that these three thymic extracts showed may reflect not only the species difference but also the difference in preparation procedures. Different components in these thymic extracts may be responsible for different biological activities. Results from these comparative studies may provide useful information in future clinical trials for the treatment of the primary immunodeficiency diseases according to their pathogenesis and may also indicate a possible beneficial effect of the combination of chemotherapy and thymic extracts.  相似文献   
993.
In summary, factors to consider in treatment are (1) the patient's age; (2) the flexibility of the condition; (3) the severity of deformity; (4) the presence of equinus; (5) abnormal shoe wear; and (6) the symptoms. When a child presents with severe flexible flatfoot one should rule out an underlying neuromuscular disorder and perform a complete biomechanical evaluation to ascertain any rotational or angular conditions of the legs that might influence the treatment. If a child is in group 1 (ages 4 to 7), a Helfet heel seat with a medial plantar wedge is usually adequate treatment. In the group II (ages 8 to 12) adolescent with flexible flatfoot, more control of the calcaneal eversion is needed. This is obtained by using a device constructed from a plaster mold taken while the foot is in neutral position. This UCBL type of device must usually extend to the metatarsal heads and be elevated on the medial and lateral sides. The group III (ages 13 to 17) adolescent usually has the additional problem of a forefoot varus, which must be controlled using a forefoot post. It is also not unusual to have to add additional wedging inside the heel of the shoe to invert the heel.  相似文献   
994.
Mycobacterium ulcerans infection in Ashanti region, Ghana   总被引:1,自引:0,他引:1  
We describe a series of 96 cases of Mycobacterium ulcerans infection (Buruli ulcer) from a new endemic focus in the Afram valley, north of Agogo, in Ghana. 63 cases were children under 13 years old. Active treatment by excision and skin grafting necessitates long stays in hospital and repeated procedures. Scarring and contracture are frequent. Eyes and other vital organs may be destroyed. In its endemic foci Buruli ulcer is a serious health burden on rural populations. Research is urgently needed, especially in prevention and non-surgical management.  相似文献   
995.
996.
997.
The value of maternal C-reactive protein (CRP) levels as predictors of fetal and maternal infective morbidity and fetal mortality was assessed prospectively over a 6-month period in all cases of premature rupture of the fetal membranes or suspected premature labour. Statistical analysis of results showed that CRP at a level of 1.32 mg/dl is a sensitive marker of infective morbidity in mother and neonate. Furthermore, there was a significant association between raised CRP levels and low-birth-weight babies, suggesting that intra-uterine infection is a major cause of prematurity in the study population.  相似文献   
998.
Following the outbreak of poliomyelitis in Gazankulu in 1982, the immunisation services in Gazankulu were thoroughly examined. As a result of this, a comprehensive immunisation policy for Gazankulu was accepted in November 1986. The broad aim of the policy is to provide effective immunisation to all Gazankulu residents against tuberculosis, diphtheria, pertussis, tetanus, poliomyelitis and measles. A specific objective is that by the end of 1987, 85% of under-5s should have been vaccinated against these six diseases and by the end of 1990 this percentage should be 97%. The detailed strategies to reach these objectives are highlighted. Within the framework of the objectives, the policy allows different areas to formulate individual strategies. Programme monitoring and community involvement are two crucial aspects of the policy and these are discussed in detail. The early successes and difficulities in implementing this policy are discussed.  相似文献   
999.
1000.
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