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   3834399篇
  免费   273992篇
  国内免费   9529篇
耳鼻咽喉   54595篇
儿科学   126024篇
妇产科学   106097篇
基础医学   552456篇
口腔科学   108451篇
临床医学   348160篇
内科学   743073篇
皮肤病学   90576篇
神经病学   309866篇
特种医学   147800篇
外国民族医学   1020篇
外科学   569489篇
综合类   82119篇
现状与发展   6篇
一般理论   1407篇
预防医学   298017篇
眼科学   89108篇
药学   279138篇
  77篇
中国医学   8131篇
肿瘤学   202310篇
  2018年   40818篇
  2017年   31298篇
  2016年   36007篇
  2015年   42331篇
  2014年   58169篇
  2013年   87717篇
  2012年   114011篇
  2011年   120827篇
  2010年   73673篇
  2009年   70495篇
  2008年   113030篇
  2007年   120208篇
  2006年   122080篇
  2005年   117161篇
  2004年   113088篇
  2003年   108060篇
  2002年   103574篇
  2001年   177203篇
  2000年   181952篇
  1999年   153126篇
  1998年   45002篇
  1997年   39773篇
  1996年   40344篇
  1995年   39140篇
  1994年   36441篇
  1993年   34060篇
  1992年   121767篇
  1991年   118222篇
  1990年   114716篇
  1989年   110732篇
  1988年   101794篇
  1987年   100036篇
  1986年   94272篇
  1985年   89923篇
  1984年   67641篇
  1983年   57324篇
  1982年   34132篇
  1981年   30702篇
  1979年   60974篇
  1978年   43579篇
  1977年   36882篇
  1976年   34386篇
  1975年   36997篇
  1974年   43877篇
  1973年   41923篇
  1972年   39192篇
  1971年   36446篇
  1970年   33826篇
  1969年   32182篇
  1968年   29465篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
Caffeine is the most widely consumed drug in Western society. The intake of caffeine-containing beverages in many adults and children often reaches levels that can induce pharmacological effects. Ninety-nine percent of ingested caffeine is absorbed and distributed to all tissues and organs. The effects of caffeine intake differ greatly according to acute or chronic intake, level of intake, and the development of tolerance. Caffeine administered acutely to non-users or recent abstainers can induce hypertension, arrhythmias, altered myocardial function, increased plasma catecholamine levels, plasma renin activity, serum cholesterol levels, increased production of urine, gastric acid secretion, and alterations in mood and sleep patterns. Tolerance to chronic caffeine intake develops in most individuals, with the cessation of its effects on the renal system, the cardiovascular system, the gastrointestinal system and, to some extent, the central nervous system. Moderate caffeine consumers probably need to have little concern for the effect of caffeine intake on their health if their other life-style habits are also moderate.  相似文献   
994.
In the first experiment, 52 sows, each having raised one litter, were randomly assigned to the five following groups: control (nongravid) for pregnancy (CP), 110 d pregnancy (P110), control (nongravid) for lactation (CL), 4-wk lactation with 8 (L8) and with 12 (L12) piglets. In a second experiment, 36 sows, each having raised three litters, were randomly assigned to the following groups: control group (nongravid) fed a low-energy-density, 1% tallow diet (CLED) and two lactating groups, one fed the low-energy-density diet (LLED) and one fed a high-energy-density, 10% tallow diet (LHED). At slaughter, the stomach, small and large intestine and cecum were excised, emptied and freed from fat. Lengths and pre- and post-defatting weights were measured. Portions of tissues were homogenized and analyzed for protein, pepsin, maltase, RNA and DNA. Pregnancy had no effect on the weights of the different components of the gastrointestinal tract. Liver and small intestine weights were larger in lactating sows than in the CL group. Sows nursing 12 piglets had heavier livers than those nursing 8. The fundic mucosa of the latter had higher total pepsin activity and total protein and RNA contents than that of L12 sows. LHED sows had heavier small intestine and lower total pepsin content of the fundic mucosa than LLED sows.  相似文献   
995.
Relatives of 22 schizotypal probands were evaluated for lifetime psychiatric diagnoses. Forty-four (N = 44) of the 97 available relatives were interviewed directly using the Diagnostic Interview Schedule. The rates of psychiatric diagnoses were compared with those of sixty-six (N = 66) of 140 relatives of 30 depressed patients. Family history of mental illness was ascertained by the informant method on the remainder of relatives of both proband groups. The rate of depression found in the relatives of schizotypal patients was 52% in those directly interviewed and 25.7% when informants' reports on unavailable relatives are pooled with direct interview data. These rates were not significantly higher than those found for the relatives of depressed probands (34.8% by direct interview and 21% including reports from informants). The high rates of depression in the relatives of schizotypal probands may indicate that schizotypal personality is associated with affective disorder and not only with schizophrenia. However, the high rates may be due to the presence of depressive character traits in relatives, which inflate the rates of dysthymic disorder and other chronic depressive disorders in the relatives of borderline patients.  相似文献   
996.
A 68 year-old woman presented with a two-week history of amaurosis fugax, ipsilateral fronto-temporal headache and jaw claudication suggesting carotid giant cell arteritis. However, this syndrome proved to be due to atherosclerosis causing complete occlusion of the external carotid artery at its origin and narrowing of the internal carotid artery. Combined external and internal carotid endarterectomy relieved the symptoms. The symptom complex of temporal arteritis may be rarely mimicked by carotid atherosclerotic occlusive disease.  相似文献   
997.
998.
Results of an examination of 39 patients are described and critically assessed. An analysis of the resolving power of the method of ultrasonic angiography in pathological formations of major vessels of the neck is given.  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