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   137691篇
  免费   13657篇
  国内免费   6756篇
耳鼻咽喉   1585篇
儿科学   2146篇
妇产科学   3179篇
基础医学   13618篇
口腔科学   2826篇
临床医学   18841篇
内科学   21787篇
皮肤病学   1896篇
神经病学   7075篇
特种医学   4510篇
外国民族医学   40篇
外科学   14602篇
综合类   19662篇
现状与发展   22篇
一般理论   18篇
预防医学   11138篇
眼科学   3544篇
药学   13650篇
  116篇
中国医学   6638篇
肿瘤学   11211篇
  2024年   427篇
  2023年   2121篇
  2022年   4131篇
  2021年   5705篇
  2020年   4536篇
  2019年   3837篇
  2018年   4489篇
  2017年   4292篇
  2016年   3919篇
  2015年   5935篇
  2014年   7427篇
  2013年   7966篇
  2012年   10496篇
  2011年   11194篇
  2010年   7986篇
  2009年   6771篇
  2008年   8071篇
  2007年   7953篇
  2006年   7585篇
  2005年   6867篇
  2004年   4977篇
  2003年   4508篇
  2002年   3740篇
  2001年   3266篇
  2000年   2953篇
  1999年   2790篇
  1998年   1579篇
  1997年   1503篇
  1996年   1291篇
  1995年   1189篇
  1994年   1057篇
  1993年   621篇
  1992年   972篇
  1991年   882篇
  1990年   739篇
  1989年   657篇
  1988年   594篇
  1987年   504篇
  1986年   404篇
  1985年   335篇
  1984年   229篇
  1983年   209篇
  1982年   125篇
  1981年   137篇
  1980年   86篇
  1979年   150篇
  1978年   123篇
  1977年   98篇
  1974年   98篇
  1972年   94篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
To study micrometastasis at its earliest stages, the bacterial lacZ marker gene was introduced into human EJ Ha-ras-transformed BALB/c 3T3 cells (LZEJ), followed by their intravenous injection into nude mice. Lung micrometastases were easily identified by blue staining of lacZ-tagged cells minutes/hours after injection, permitting effective evaluation of establishment/clearance mechanisms of LZEJ cells. Different treatments were used to disable LZEJ cells (fixation, irradiation, or mitomycin C) to determine modulation of these processes--although unable to divide, these cells stain for lacZ expression for days after treatment. Fixation-killed cells generated large microfoci (> 13-15 cells/focus) with well-rounded morphologies while live, irradiated, or mitomycin-treated cells generated smaller, irregularly shaped foci (3-7 cells/focus). Fixed-cell foci were cleared more slowly from lungs than the other three classes, even when prefiltered to remove large aggregates. All foci of disabled cells were eventually cleared while a basal level of live-cell foci persisted. Co-injection of fixed and live cells (or preinjection of fixed cells, followed by live cells) resulted in complete clearance of live-cell microfoci; in contrast, preinjection of live cells (then injection of fixed cells) led to survival of live-cell micrometastases. Therefore, altered deformability and/or cell surface interactions of tumor cells modulate the effectiveness of host-clearing mechanisms in the lung and in some situations these altered cells facilitate clearance of live tumor cells that are normally tumor-progressing.  相似文献   
5.
Summary: This is the first report of the largest study of blood pressure measurement in pregnancy in a New Zealand population using standardized definitions and methodology. Over 3,800 women who delivered in an 8-month period in the Wellington region were included in the study. Blood pressure measurement and the presence of oedema and proteinuria were recorded from booking until delivery and in the puerperium. Only 2.7% of women were unable to be contacted after delivery for details on outcomes. The results established normal ranges for blood pressure throughout pregnancy. The data show that Mood pressure greater than 140/90 until 35 weeks' gestation is outside 2 standard deviations at all gestations and justifies using these measurements as the definition of hypertension in pregnancy. The fall in blood pressure in the 2nd trimester was less than 1 mm Ffg per week in both the systolic and diastolic pressures. This fall was smaller than previously recorded in other studies. Gestational hypertension was the commonest blood pressure abnormality occurring in 15.2% of the population. This represented 69% of the pregnant women with a hypertensive disorder. The overall incidence of both gestational hypertension and preeclampsia was 18.5% which is higher than reported in other parts of the world. In this study obesity was significantly associated with hypertensive disorders in pregnancy. An arm circumference of >33 cm, one of the measurements of obesity, was found in 6.8% of the study population. Even after the effect of arm circumference was taken into account, hypertensive disorders were also more common in Pacific Island women. Ankle oedema was significantly associated with the development of both gestational hypertension and preeclampsia but the incidence of oedema was noted in only 11.9% of the subjects.  相似文献   
6.
7.
8.
This study evaluates the potential for endothelial seeding of a collagen-impregnated Dacron graft with or without surface modifiers (fibronectin, heparin) to attach and retain these cells during flow. Human umbilical endothelial cells were harvested, cultured, labeled with Indium111-oxine and seeded onto 30 mm X 4 mm diameter grafts. Six graft surfaces were studied: 1) a collagen-impregnated Dacron graft, HemashieldR (C); 2) C + fibronectin (C + F); 3) C + heparin (C + H); 4) C + F + H; 5) HytrelR + F (Hyt + F); and 6) Hyt + F + H. Radioactive loss determined the percentage attachment and then percentage retention of labeled inoculum after a one-hour in vitro perfusion. Scanning electron and light microscopy demonstrated the endothelium on the graft surface following perfusion. Fibronectin-coated grafts had a significantly higher percentage attachment than those without fibronectin (ANOVA, P less than 0.05). However, the percentage retention following perfusion was similar for all Dacron grafts and statistically inferior to the HytrelR grafts studied (ANOVA, P less than 0.05). SEM evaluation of the C + F + H graft surface was qualitatively the most impressive Dacron surface for seeding, yet was inferior to the HytrelR graft. We conclude that fibronectin benefits the initial attachment of endothelium to collagen-coated Dacron rivaling the HytrelR surface. Fibronectin does not improve percentage retention of the HemashieldR surface during perfusion, therefore, some of its initial benefit is lost.  相似文献   
9.
Wall-eyed bilateral internuclear ophthalmoplegia (WEBINO) is a rarely reported syndrome. There is dispute about whether WEBINO is caused by a pontine or a midbrain lesion and whether the medial rectus subnuclei are implicated. In a study of the clinical and imaging features of four patients with WEBINO, we found that that three of four lesions involved the midbrain but not necessarily the medial rectus subnuclei.  相似文献   
10.
维持性血液透析患者血清甲状旁腺激素(Parathyroid hormone,PTH)水平显著增高,PTH与患者心功能下降、营养状态恶化以及死亡率的增加密切相关.然而,临床实践发现,部分慢性肾脏疾病(Chronic kidney disease,CKD)3-4期、甚至CKD1期的患者血清PTH水平也增高,PTH对此类患者的影响如何,目前报道较为少见.本文结合文献就FTH对非透析CKD患者的心血管系统、骨代谢、营养状况及预后的影响作一综述.  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