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   796篇
  免费   59篇
  国内免费   21篇
耳鼻咽喉   3篇
儿科学   16篇
妇产科学   11篇
基础医学   89篇
口腔科学   15篇
临床医学   100篇
内科学   186篇
皮肤病学   6篇
神经病学   55篇
特种医学   166篇
外科学   39篇
综合类   28篇
一般理论   1篇
预防医学   49篇
眼科学   15篇
药学   68篇
肿瘤学   29篇
  2019年   6篇
  2018年   9篇
  2016年   10篇
  2015年   21篇
  2014年   13篇
  2013年   18篇
  2012年   18篇
  2011年   21篇
  2010年   16篇
  2009年   29篇
  2008年   42篇
  2007年   44篇
  2006年   32篇
  2005年   30篇
  2004年   25篇
  2003年   16篇
  2002年   21篇
  2001年   30篇
  2000年   24篇
  1999年   30篇
  1998年   29篇
  1997年   20篇
  1996年   10篇
  1995年   14篇
  1994年   14篇
  1993年   11篇
  1992年   12篇
  1991年   14篇
  1990年   18篇
  1989年   24篇
  1988年   17篇
  1987年   21篇
  1986年   28篇
  1985年   23篇
  1984年   13篇
  1983年   15篇
  1982年   6篇
  1980年   6篇
  1979年   12篇
  1977年   5篇
  1976年   6篇
  1973年   6篇
  1972年   5篇
  1971年   6篇
  1970年   6篇
  1968年   9篇
  1966年   5篇
  1945年   5篇
  1944年   4篇
  1939年   5篇
排序方式: 共有876条查询结果,搜索用时 0 毫秒
11.
Y chromosome deletions encompassing the AZFc region have been reported in 13% of azoospermic men and 7% of severely oligozoospermic men. We examined the impact of these Y deletions on the severity of testicular defects in 51 azoospermic men undergoing intracytoplasmic sperm injection (ICSI) after testicular sperm extraction (TESE) and 30 men with severe oligozoospermia undergoing ICSI after ejaculation of spermatozoa. In addition, five azoospermic patients shown previously to have Y chromosome deletions underwent histological evaluation of their previously obtained testis biopsy specimens. A further 27 azoospermic men underwent TESE-ICSI, but not Y chromosome DNA testing. Ten of 51 azoospermic men (20%) who underwent TESE-ICSI and Y-DNA testing were found to be deleted for portions of the Y chromosome AZFc region. Of these 10, five had spermatozoa retrievable from the testis, and in two cases the wives became pregnant. Of the 41 azoospermic men with no Y chromosome deletion, 22 (54%) had spermatozoa retrievable from the testis, and in 12 cases (29%) the wives became pregnant. Four of 30 (13%) severely oligozoospermic patients were found to be deleted for AZFc and in three (75%) of these pregnancy was achieved. The other 26 severely oligozoospermic couples who had no AZFc deletions underwent ICSI, and 12 (46%) have an ongoing or delivered pregnancy. The embryo implantation rate was not significantly different for azoospermic (22%), oligozoospermic (16%), Y-deleted (14%) or Y-intact (18%) men. Of the total of 19 infertile men who had Y chromosome deletions, 14 had deletions within Y chromosome intervals 6D-6F, in the AZFc region. Twelve of those 14 had some spermatozoa (however few in number) in the ejaculate or testis. Five of the Y-deleted men had deletions that extended more proximally on the Y chromosome, and in none of these could any spermatozoa be observed in either ejaculate or testis. These results support the concept that, in azoospermic or oligozoospermic men with Y chromosome deletions limited to intervals 6D-6F (AZFc), there are generally very small numbers of testicular or ejaculated spermatozoa. Larger Y deletions, including and extending beyond the AZFc region and encompassing more Y genes, tend to be associated with a total absence of testicular spermatozoa. In those cases where spermatozoa were retrieved, the presence of Y deletions had no obvious impact on fertilization or pregnancy rate.   相似文献   
12.
13.
14.
15.
Integrated Care Plans, or Anticipated Recovery Pathways, embrace quality and efficiency concepts. They allow multidisciplinary input on patient care planning. Pathways are now being developed hospital-wide. Discusses their development and implementation.  相似文献   
16.
Between January 1976 and June 1981, 814 patients with pulmonary tuberculosis were treated for 9 months with isoniazid (INH) and rifampin (RIF), daily for 1 month and twice weekly for the other 8 months. Overall success was achieved in 95% of the 586 patients who completed therapy: in 15 patients (2.9%), sputum cultures failed to convert to negative during therapy, and 10 patients (1.7%) have relapsed since stopping the chemotherapy. Major toxic effects occurred in 22 patients; in 14 during the daily phase and in 8 during the twice-weekly phase. Hepatic toxicity occurred in 13 patients during daily and in 5 during twice-weekly treatment, and it was caused by RIF in 5, INH in 10, and was undetermined in 3. Hematologic abnormalities developed in 4 patients: in 1 during the daily and in 3 during the twice-weekly phase. Minor side effects, which were not life threatening, were encountered in 62 patients: in 35 during the daily and in 27 during the twice-weekly therapy. These were gastrointestinal intolerance in 18, drug fever in 27 (including 11 with "flu-syndrome" during twice-weekly administration), cutaneous rashes in 14, and headache, general malaise, and weakness in 3. These side effects were produced by RIF in 43, by INH in 18, and the responsible drug was not identified in 1. Hypersensitivity reactions to twice-weekly administration of RIF were infrequent. Clinical surveillance for toxicity is preferred over routine and regular biochemical monitoring.  相似文献   
17.
The effects of glutathione depletion in isolated hepatocytes have been studied. A list of compounds which depleted glutathione and induced lipid peroxidation and cell lysis is given. The effects of halogenated acetamides were studied in more detail and results of studies on the interaction of iodoacetamide with cellular constituents are presented. A single metabolite of iodoacetamide, tentatively identified as the glutathione conjugate, was excreted from the cells while less than one percent of the "parent compound" was retained, tightly bound to macromolecules. This bound component could not be associated with the cellular damage. Methionine, cysteine and alpha-tocopherol, as wellas paracetamol and ethylmorphine, were found to prevent lipid peroxidation and lysis. It is concluded that GSH deficiency per se can lead to lipid peroxidation and that this reaction caused the observed hepatocellular lysis.  相似文献   
18.
19.
Toksoz  D; Dexter  TM; Lord  BI; Wright  EG; Lajtha  LG 《Blood》1980,55(6):931-936
The isolation of a DNA synthesis inhibitor (NBME fraction IV) and stimulator (RBME fraction III) specific for the hemopoietic stem cell (CFU-s) from freshly isolated normal adult and regenerating murine bone marrow, respectively, has been well documented. We have utilized long- term liquid bone marrow cultures in a further analysis of the role of these factors in the regulation of CFU-s proliferation. Our results show that shortly after feeding, at a time when the cultured CFU-s are actively proliferating, high levels of the hemopoietic stem cell proliferation stimulator fraction III can be isolated from the culture medium. In contrast, the presence of essentially noncycling CFU-s found in cultures fed 8-10 days previously correlates with high levels of the hemopoietic stem cell inhibitor fraction IV. These results suggest that a certain balance between these factors determines CFU-s proliferation in the long-term cultures. In support of this, DNA synthesis in actively cycling CFU-s in the long-term cultures is inhibited for at least 3 days by the addition of excess NBME fraction IV (inhibitor). Furthermore, DNA synthesis in noncycling cultured CFU-s is stimulated for at least 5 days by the addition of RBME fraction III (stimulator).  相似文献   
20.
Although trace minerals are necessary constituents of enzymes, dietary requirements of these nutrients for the elderly are unknown. This study measured selenium balance in six dependent elderly men before and after five weeks daily administration of 200 micrograms organically-bound selenium; dietary selenium intake averaged 62.1 +/- 7 micrograms/day during both study periods. Selenium status was assessed not only chemically but also biologically as red cell and platelet glutathione peroxidase activities. Plasma selenium averaged 8.8 +/- 0.8 micrograms% (normal: 10 +/- 2 micrograms %) when intake derived from dietary sources alone and increased during medicinal supplementation to an average of 12.8 +/- 1.9 micrograms %. The rise in plasma selenium was not associated with an increase in red cell or platelet glutathione peroxidase activity. The effect of selenium supplementation on in vivo platelet aggregability was studied by measuring plasma levels of beta-thromboglobulin and platelet factor 4, two proteins secreted concomitant with aggregation. beta-thromboglobulin diminished 7.5 +/- 11.0 ng/ml and platelet factor 7.6 +/- 11.0 ng/ml during selenium supplementation despite no change in platelet glutathione peroxidase activity. These data support the concept that selenium nutritional status should be assessed not only by blood selenium content but also by selenium-dependent enzyme activity or selenium-dependent biologic effect.  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