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   1346329篇
  免费   94930篇
  国内免费   2929篇
耳鼻咽喉   19780篇
儿科学   40602篇
妇产科学   38875篇
基础医学   188419篇
口腔科学   39963篇
临床医学   113815篇
内科学   264125篇
皮肤病学   30332篇
神经病学   107673篇
特种医学   54149篇
外国民族医学   435篇
外科学   209935篇
综合类   31153篇
现状与发展   6篇
一般理论   458篇
预防医学   93084篇
眼科学   31456篇
药学   100802篇
  4篇
中国医学   3012篇
肿瘤学   76110篇
  2018年   12014篇
  2015年   12087篇
  2014年   17063篇
  2013年   25763篇
  2012年   33817篇
  2011年   35695篇
  2010年   21196篇
  2009年   20653篇
  2008年   34309篇
  2007年   37379篇
  2006年   37936篇
  2005年   36718篇
  2004年   35757篇
  2003年   34700篇
  2002年   34149篇
  2001年   63703篇
  2000年   65384篇
  1999年   55462篇
  1998年   14772篇
  1997年   13548篇
  1996年   13020篇
  1995年   12303篇
  1994年   11529篇
  1992年   42813篇
  1991年   41321篇
  1990年   40586篇
  1989年   39588篇
  1988年   37016篇
  1987年   36442篇
  1986年   34931篇
  1985年   33131篇
  1984年   24864篇
  1983年   21091篇
  1982年   12703篇
  1981年   11595篇
  1980年   10806篇
  1979年   23947篇
  1978年   17088篇
  1977年   14853篇
  1976年   13406篇
  1975年   15277篇
  1974年   18091篇
  1973年   17571篇
  1972年   16824篇
  1971年   15730篇
  1970年   14919篇
  1969年   14348篇
  1968年   13463篇
  1967年   12020篇
  1966年   11260篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
As part of a larger investigation to determine the effect of animal vs. plant proteins on the vitamin B-6 requirement of young women, clinical changes during vitamin B-6 depletion were documented. Eight healthy young women were confined to a metabolic unit and fed a defined formula diet nearly devoid of vitamin B-6 (less than 0.05 mg/d). Serial electroencephalographic (EEG) tracings, peripheral nervous system tests, periodontal evaluations, and biochemical measures of vitamin B-6 status were conducted. Within 12 d on the depletion diet, two of the eight women exhibited abnormal EEG tracings. These changes were readily reversed by repletion of vitamin B-6 at the 0.5-mg/d level. Biochemical measures reflected lowered vitamin B-6 status but were not predictive of the onset of EEG changes. No detectable alterations in oral or periodontal status were found, nor did plaque flora change markedly. This study is the first report of EEG changes occurring in women undergoing vitamin B-6 depletion and the first report to document EEG changes in adults within 12 d on a vitamin B-6-depletion regimen.  相似文献   
992.
The study was undertaken to analyze the basal and metoclopramide-stimulated serum PRL levels in healthy parous women users (group 1, n = 12) and non-users (group 2, n = 12) of a TCu-380 IUD. All women had regular menses and were studied between days 18 to 22 of their cycle; none had lactated nor regularly ingested any type of medication during the last six months. After a 10-12 hour overnight fast, peripheral venous blood samples were obtained through an indwelling catheter at -30, -15 and 0 minutes and at 60, 90 and 120 minutes after oral metoclopramide (10 mg). There were no significant differences in serum PRL between both groups, in basal levels nor throughout the test, whether analyzing the mean values at each sampling time, the sum of PRL levels from 60-120 minutes, or the peak levels. No correlation was observed between PRL levels and any of the clinical or obstetric characteristics of the women in both groups. Serum progesterone was greater than or equal to 4.0 ng/ml in all women. Thus, the use of alpha TCu-380 IUD did not induce any significant changes in basal nor in stimulated serum PRL levels.  相似文献   
993.
The health care resource allocation debate. Defining our terms   总被引:1,自引:0,他引:1  
D C Hadorn  R H Brook 《JAMA》1991,266(23):3328-3331
The problem of health care distribution in the United States demands immediate action. Many different solutions have been proposed to slow rising health care costs and to improve access to care for the poor and uninsured. Debate among proponents of these various proposals might be advanced if a common language were adopted with regard to certain key terms instead of the various meanings currently assigned to these terms. For this reason, we propose and defend the following three definitions: (1) rationing is the societal toleration of inequitable access to health services acknowledged to be necessary by reference to necessary-care guidelines; (2) health care needs are desires for services that have been reasonably well demonstrated to provide significant net benefit for patients with specified clinical conditions; and (3) basic benefit plans are insurance packages that provide for all and only acknowledged health care needs, again by reference to appropriate clinical guidelines.  相似文献   
994.
995.
996.
During hemodialysis with cuprophan membranes, the complement system as well as leukocytes become activated. In order to clarify the role of dialyzer geometry, the effect of hollow-fiber versus flat-sheet dialyzers and of different surface areas on C3a generation and leukocyte degranulation was investigated. Plasma levels of leukocyte elastase in complex with alpha 1-proteinase inhibitor were significantly increased after 1 h (+55%) and 3 h (+62%) of hemodialysis with flat-sheet dialyzers as compared to hollow-fiber devices. In addition, plasma levels of lactoferrin, released from the specific granules of leukocytes during activation, were significantly higher (+42%) 3 h after the onset of dialysis treatment with flat-sheet than with hollow-fiber dialyzers. With respect to surface area, larger dialyzers tended to cause more release of leukocyte elastase as compared to dialyzers with smaller surface areas, irrespectively of the configuration of the dialyzer used. On the other hand, activation of the complement system, as measured by the generation of C3a-desarg, did not differ with both types of configurations. The same held true for leukopenia, which was almost identical for hollow-fiber and flat-sheet dialyzers. From these findings two lines of evidence emerge: First, not only the type of membrane material used in a dialyzer may influence its biocompatibility, but the geometry of the extracorporeal device also determines the degree of compatibility. Hence, the extent of leukocyte activation correlated with both configuration of the dialyzer and surface area of the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
997.
Idiopathic retroperitoneal fibrosis. A retrospective analysis of 60 cases   总被引:5,自引:0,他引:5  
Sixty patients with idiopathic retroperitoneal fibrosis presenting between 1965 and 1984 are reviewed. Their mean age at presentation was 56 years and the male:female ratio was 3:1. The commonest presenting symptoms were flank and abdominal pain, weight loss, nausea and polyuria. Physical examination was usually normal, expect for the presence of hypertension. Anaemia and elevation of erythrocyte sedimentation rate were usually present. Proteinuria was found in less than a third of patients at presentation and significant bacteriuria was uncommon. The correct diagnosis was made or suspected in very few patients before referral. The cumulative actuarial survival rate was 86% at 1 year and 78% at 2 years. Seventeen patients died; they were significantly older and more uraemic at the time of referral than those who survived. A few patients did well with either corticosteroid therapy or ureterolysis alone. In the majority, both operation and steroid treatment were necessary. In bilateral obstruction with residual function in both kidneys, bilateral ureterolysis proved superior to unilateral operation (each followed by steroid therapy) in conserving renal function. Operation alone or steroid therapy alone should be considered in cases where steroids or surgery respectively present particular hazards. The less traumatic unilateral operation should be considered in poor risk patients and in those whose renal function is absent on one side. In many survivors, disease activity has persisted for many years. Life-long follow-up is recommended.  相似文献   
998.
Decreased sensitivity to phalloidin of aged F344/DuCrj rat hepatocytes   总被引:1,自引:0,他引:1  
The phalloidin sensitivity of hepatocytes resulting in the formation of cytoplasmic blebs was examined with cells isolated from 73- to 74-week-old and 99- to 100-week-old F344/DuCrj rats of both sexes by a collagenase perfusion method. The cells isolated from aged rats were less sensitive to the toxin than those obtained from 10- to 14-week-old rats. The decrease in the sensitivity was more marked in males than in females, and it appeared at an earlier age in the former than in the latter. Phalloidin consumption experiments showed decreases in the cellular uptake of the toxin in aged rats, and these were more marked in males than in females. The low cellular uptake of the toxin seemed to play an important role in the low sensitivity of the cells in aged rats. Although histological and histochemical examinations showed the development of foci of altered hepatocytes in the aged rat liver, the foci were estimated to account for less than 1.5% of liver tissues. Thus, the decrease in the sensitivity of the cells isolated from whole liver tissues might mainly be attributed to the decrease in the sensitivity of otherwise normal-looking hepatocytes.  相似文献   
999.
1000.
The purpose of this study was to determine if changes in hindlimb motoneuron membrane electrical properties occur 4–6 months after spinal transection in the adult animal. Eight acute and nine chronic animals were spinalized at T12. Intracellular recordings from motoneurons innervating the triceps surae were performed. Membrane electrical properties, including resting potential, action potential peak amplitude, afterhyperpolarization duration, rheobasic current, input resistance and axonal conduction velocity were measured. There were no statistical differences found between group means or frequency distributions in the membrane properties of motoneurons assessed from acute and chronic spinal animals. Thus, alteration of motoneuron membrane properties does not appear to be a major contributing factor to the hyperexcitable hindlimb reflex activity demonstrated by chronic spinal animals.  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