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   6828篇
  免费   720篇
  国内免费   30篇
耳鼻咽喉   65篇
儿科学   332篇
妇产科学   83篇
基础医学   806篇
口腔科学   164篇
临床医学   681篇
内科学   1305篇
皮肤病学   368篇
神经病学   457篇
特种医学   470篇
外科学   990篇
综合类   178篇
一般理论   8篇
预防医学   516篇
眼科学   44篇
药学   451篇
中国医学   3篇
肿瘤学   657篇
  2021年   72篇
  2019年   78篇
  2018年   94篇
  2017年   62篇
  2016年   78篇
  2015年   84篇
  2014年   106篇
  2013年   144篇
  2012年   197篇
  2011年   201篇
  2010年   163篇
  2009年   142篇
  2008年   228篇
  2007年   253篇
  2006年   262篇
  2005年   245篇
  2004年   227篇
  2003年   243篇
  2002年   192篇
  2001年   207篇
  2000年   226篇
  1999年   213篇
  1998年   128篇
  1997年   141篇
  1996年   155篇
  1995年   123篇
  1994年   93篇
  1993年   92篇
  1992年   161篇
  1991年   192篇
  1990年   181篇
  1989年   174篇
  1988年   212篇
  1987年   186篇
  1986年   159篇
  1985年   199篇
  1984年   114篇
  1983年   123篇
  1982年   74篇
  1981年   71篇
  1980年   62篇
  1979年   109篇
  1978年   101篇
  1977年   82篇
  1976年   79篇
  1975年   72篇
  1974年   93篇
  1973年   100篇
  1972年   72篇
  1971年   72篇
排序方式: 共有7578条查询结果,搜索用时 31 毫秒
51.
52.
The primary objective of revascularization procedures in the posterior circulation is the prevention of vertebrobasilar ischemic stroke. Specific anatomical and neurophysiologic characteristics such as posterior communicating artery size affect the susceptibility to ischemia. Current indications for revascularization include symptomatic vertebrobasilar ischemia refractory to medical therapy and ischemia caused by parent vessel occlusion as treatment for complex aneurysms. Treatment options include endovascular angioplasty and stenting, surgical endarterectomy, arterial reimplantation, extracranial-to-intracranial anastomosis, and indirect bypasses. Pretreatment studies including cerebral blood flow measurements with assessment of hemodynamic reserve can affect treatment decisions. Careful blood pressure regulation, neurophysiologic monitoring, and neuroprotective measures such as mild brain hypothermia can help minimize the risks of intervention. Microscope, microinstruments and intraoperative Doppler are routinely used. The superficial temporal artery, occipital artery, and external carotid artery can be used to augment blood flow to the superior cerebellar artery, posterior cerebral artery, posterior inferior cerebellar artery, or anterior inferior cerebellar artery. Interposition venous or arterial grafts can be used to increase length. Several published series report improvement or relief of symptoms in 60 to 100% of patients with a reduction of risk of future stroke and low complication rates.  相似文献   
53.
54.
Research has shown that pregnant women who smoke cigarettes increase their risk of having low birthweight (LBW) infants. Recent randomized trials indicate that women who quit smoking early in pregnancy reduce their risk of delivering a LBW infant. Using various sources, we estimated the cost-effectiveness of a smoking cessation program for preventing LBW and perinatal mortality. Assuming the program would cost $30 a participant and that 15% of the participants would quit smoking, we determined that a program offered to all pregnant smokers would shift 5,876 LBW infants to normal birthweight and would cost about $4,000 for each LBW infant prevented. Since infants born to smokers are at 20% greater risk for a perinatal death, a smoking cessation program could prevent 338 deaths at a cost of $69,542 for each perinatal death averted. Compared with the costs of caring for these LBW infants in a neonatal intensive care unit (NICU), smoking cessation programs would save $77,807,054, or $3.31 per $1 spent. The ratio of savings to costs increases to more than six to one when we include reducing long-term care for infants with disabilities secondary to LBW in the benefits from smoking cessation programs. These findings argue for routinely including smoking cessation programs in prenatal care for smokers.  相似文献   
55.
56.
Oscillatory motion of the normal cervical spinal cord   总被引:2,自引:0,他引:2  
  相似文献   
57.
Periosteal Ewing sarcoma   总被引:3,自引:0,他引:3  
  相似文献   
58.
Although benign, pituitary adenomas may not always be curable by surgery alone. This is usually owing to dural infiltration and the technical problems of removal of involved dura in the sellar region. In such circumstances, some form of adjuvant therapy may be needed to address residual tumour and forestall recurrence. Radiotherapy and drugs, such as bromocriptine or octreotide, although effective are far from ideal adjuvant therapies and this has led to the study of the effects of photodynamic therapy on pituitary adenomas. It has been shown that photodynamic therapy using the photosensitising drugs haematoporphyrin derivative and aluminium phthalocyanine is active experimentally against these tumours. This could provide another useful weapon to use against these challenging lesions.  相似文献   
59.
60.
In a prospective, randomized study of insemination with donor semen, intracervical insemination by straw was compared with insemination using a cervical cap with an intracervical reservoir. A total of 91 patients completed 486 treatment cycles. There were no significant differences in age, parity, indication for insemination by donor, or method of cycle monitoring between women who became pregnant and those who did not conceive with either insemination method. In 236 standard intracervical insemination cycles, 14 patients became pregnant (5.9% per cycle), whereas 38 patients conceived in 250 cervical cap cycles (15.2% per cycle). Both the crude pregnancy rates and the cumulative pregnancy rates calculated by the Kaplan-Meier life-table method were significantly different (chi(2)-test, P < 0.001, and log-rank test, P < 0.005 respectively). Pregnancy rates in artificial insemination with cryopreserved donor semen may be improved by the use of a cervical cap when compared to cervical insemination by straw. The use of the cervical cap may prolong the exposure of the spermatozoa to the cervical mucus and prevent the backflow of semen into the vagina.   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