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   1778222篇
  免费   131255篇
  国内免费   4791篇
耳鼻咽喉   22979篇
儿科学   57843篇
妇产科学   49302篇
基础医学   254352篇
口腔科学   51594篇
临床医学   157864篇
内科学   348770篇
皮肤病学   40442篇
神经病学   136958篇
特种医学   66749篇
外国民族医学   247篇
外科学   269184篇
综合类   42576篇
现状与发展   4篇
一般理论   562篇
预防医学   130762篇
眼科学   42352篇
药学   130919篇
  7篇
中国医学   5042篇
肿瘤学   105760篇
  2021年   13522篇
  2019年   14278篇
  2018年   21064篇
  2017年   15989篇
  2016年   17388篇
  2015年   19922篇
  2014年   27492篇
  2013年   39666篇
  2012年   55252篇
  2011年   58080篇
  2010年   34384篇
  2009年   32122篇
  2008年   53883篇
  2007年   57366篇
  2006年   57817篇
  2005年   54836篇
  2004年   52922篇
  2003年   50140篇
  2002年   48237篇
  2001年   96162篇
  2000年   98117篇
  1999年   80736篇
  1998年   21077篇
  1997年   18294篇
  1996年   18024篇
  1995年   17325篇
  1994年   15824篇
  1993年   14603篇
  1992年   59978篇
  1991年   57909篇
  1990年   55495篇
  1989年   53274篇
  1988年   48576篇
  1987年   47286篇
  1986年   44419篇
  1985年   42151篇
  1984年   30833篇
  1983年   26236篇
  1982年   14634篇
  1979年   27005篇
  1978年   18487篇
  1977年   15656篇
  1976年   14603篇
  1975年   15511篇
  1974年   18738篇
  1973年   18051篇
  1972年   16765篇
  1971年   15486篇
  1970年   14346篇
  1969年   13457篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
This study characterizes a Plasmodium berghei white rat model of P. falciparum malaria in the pregnant human. Seventy-day-old and 114-day-old female rats, given an infecting inoculum at time of mating, had higher parasitemias and a more severe anemia than age- and sex-matched controls. Under these experimental conditions, the parasitemia went to crisis in all animals and there were no fatal infections. In contrast, all animals died when the infection was initiated 7 days after conception, a timing that brought a coincidence of peak parasitemia and term. Pregnancy during the post-crisis subpatent period did not cause recrudescence. At the time of delivery, the parasitemia was consistently higher in the placental (crush smear) blood than in the peripheral (tail) blood. This difference was greatest in animals giving birth shortly before or 1-2 days after the parasitemic crisis. Very young, compact parasite forms predominated in the placental blood, whereas trophozoites predominated in the peripheral blood.  相似文献   
992.
993.
994.
It is well known that fibroblasts are a main source of extracellular matrix synthesis necessary for tissue repair. In addition, macrophages secrete products that are known to modulate synthesis of extracellular matrix. Accordingly, we studied the incorporation of [3H]thymidine, [3H]proline, and [35S]sulfate into macromolecules produced by fibroblasts recovered from the site of peritoneal tissue repair cultured with and without spent media from postsurgical peritoneal macrophages. Rabbits underwent resection and reanastomosis of their small intestines. Peritoneal exudative cells (PEC) were then collected on postsurgical day 5 and day 10 as well as from nonsurgical controls, separated by discontinuous Percoll gradient centrifugation, and cultured for 48 h. A second group of rabbits underwent peritoneal wall abrasion from which fibroblast tissue repair cells (TRC) were collected from the site of injury at postsurgical day 7 and maintained in culture for varying times. Incorporation of radiolabeled precursors into DNA, collagen, and sulfated proteoglycans was determined. Incorporation of [3H]thymidine and [3H]proline into untreated TRC gradually decreased with culture duration. Conversely, [35S]sulfate incorporation gradually increased during prolonged culture. Macrophage spent media increased the levels of [3H]thymidine incorporation by the TRC. [3H]Proline and [35S]sulfate incorporation into TRC were also stimulated by macrophage spent media. However, this stimulation may be due to the enhanced proliferation of TRC by macrophage spent media. In conclusion, tissue repair fibroblasts are activated for postsurgical repair at the site of injury by many factors including secretory products from postsurgical macrophages.  相似文献   
995.
The accumulation of 201Tl in tumor and inflammatory tissues were small. However, this nuclide showed a high concentration in viable tumor tissue, less in connective tissue (containing inflammatory tissue), and was not seen in necrotic tumor tissue regardless of the time after administration of 201Tl(I)-chloride. In inflammatory lesions, 201Tl accumulated in subcutaneous tissue infiltrated with neutrophils and macrophages, and quite large amounts of this nuclide were accumulated in subcutaneous tissue and sites where neutrophils were crowded. Most 201Tl existed in a free form in the fluid of tumor and inflammatory tissues regardless of the time after administration. A small amount of this nuclide was localized in the nuclear, mitochondrial and microsomal fractions in these tissues, and the nuclide was bound to protein in these fractions. The distribution of 201Tl(III)-chloride in tumor bearing animals was essentially the same as that of 201Tl(I)-chloride.  相似文献   
996.
997.
998.
A total of 42 patients with recurrent superficial bladder tumors or carcinoma in situ entered a prospective, randomized trial to compare the efficacy of bacillus Calmette-Guerin therapy with and without quarterly maintenance instillations of bacillus Calmette-Guerin. Maintenance therapy did not reduce further bladder tumor recurrence rates or the interval to recurrence in patients who responded to the initial course of therapy. However, prolongation of toxicity was observed with maintenance bacillus Calmette-Guerin therapy.  相似文献   
999.
Computed tomography of the brain in the Smith-Lemli-Opitz syndrome   总被引:1,自引:0,他引:1  
Computed tomographic (CT) scans of the brain in a child with Smith-Lemli-Opitz syndrome revealed enlargement of the ventricular system, hypoplasia of the cerebellum, and abnormal thickening of the gray matter, consistent with pachygyria. These findings have been previously noted in autopsies performed on patients with this disorder. We conclude that CT scanning is a valuable tool in the evaluation of children suspected of having the Smith-Lemli-Opitz syndrome.  相似文献   
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