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   1276514篇
  免费   92734篇
  国内免费   1987篇
耳鼻咽喉   18185篇
儿科学   42257篇
妇产科学   37812篇
基础医学   186983篇
口腔科学   35381篇
临床医学   108104篇
内科学   251428篇
皮肤病学   26497篇
神经病学   99175篇
特种医学   49981篇
外国民族医学   366篇
外科学   197579篇
综合类   26516篇
现状与发展   1篇
一般理论   300篇
预防医学   92580篇
眼科学   29056篇
药学   97756篇
  1篇
中国医学   2496篇
肿瘤学   68781篇
  2018年   11808篇
  2015年   11610篇
  2014年   15994篇
  2013年   24347篇
  2012年   33540篇
  2011年   35937篇
  2010年   21206篇
  2009年   20013篇
  2008年   34973篇
  2007年   37942篇
  2006年   38497篇
  2005年   37791篇
  2004年   36376篇
  2003年   35366篇
  2002年   34915篇
  2001年   58093篇
  2000年   59584篇
  1999年   50686篇
  1998年   14232篇
  1997年   12809篇
  1996年   13071篇
  1995年   12345篇
  1994年   11757篇
  1993年   10860篇
  1992年   40984篇
  1991年   40358篇
  1990年   39885篇
  1989年   38706篇
  1988年   36108篇
  1987年   35349篇
  1986年   33723篇
  1985年   32134篇
  1984年   23922篇
  1983年   20818篇
  1982年   12377篇
  1981年   10927篇
  1980年   10204篇
  1979年   22635篇
  1978年   15877篇
  1977年   13729篇
  1976年   12970篇
  1975年   14201篇
  1974年   16682篇
  1973年   16076篇
  1972年   15318篇
  1971年   14229篇
  1970年   13214篇
  1969年   12731篇
  1968年   11978篇
  1967年   10478篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
961.
In a previous article we have reported our finding of an unknown vitamin derivative in the serum of cancer patients and in rats transplanted by a malignant tumor. Analysis of this compound extracted from serum of cancer patients, was carried out by I.R., U.V., mass spectrography and nuclear magnetic resonance (N.M.R.) determination. This analysis led us to the conclusion that the compound was a ketone derivative of D3 vitamin: 1-ceto-24-methyl-25-hydroxycholecalciferol, provisionally designated D3C. Enzymatic pathways involved in the biosynthesis of this substance and its possible role in normal and pathological cell division are discussed.  相似文献   
962.
To explore the concept of the young adult chronic patient as a distinct clinical entity, the author analyzed a sample of 134 chronic patients on six variables relating to style of interaction with service providers and on diagnostic and demographic variables. The results showed that the 105 younger chronic patients in the sample were more likely than the older patients to be male, to be referred to treatment for suicidal and homicidal gestures and ideation, to have a diagnosis of personality disorder, and to be overrepresented in the treatment population. The author believes the combination of these factors helps create disproportionately high visibility for young adult chronic patients and requires special provisions for their engagement in treatment.  相似文献   
963.
964.
Since variations in the electric skin impedance delta R depend on an instantaneous value R, parameters of the cutaneogalvanic reaction should be assessed in the scale of the natural logarithm lnR. Such methodology allows an adequate comparison of results obtained in many patients or in a single patient during a long-term period.  相似文献   
965.
966.
V Dave  G W Gordon  K D McCarthy 《Glia》1991,4(5):440-447
Very little information is available concerning the pharmacology of type 2 astroglia. During the past decade it has become apparent that two distinct lineages of astroglial cells can be defined in vitro. These two lineages are commonly referred to as type 1 and type 2 and are distinguished from each other on the basis of their morphological features and antigenic phenotypes. In contrast to type 1 astroglia, very little is known about the pharmacology of type 2 astroglia. The lack of information concerning the responsiveness of these cells stems primarily from difficulties encountered in isolating large numbers of type 2 astroglia free of other cell types. In the present study video- and photometer-based imaging systems were used to monitor the influence of a series of neuroligands on the intracellular calcium levels of individual cerebral type 2 astroglia in order to assess their expression of calcium-mobilizing receptors. The responses of 85 immunocytochemically identified cerebral type 2 astroglia to bradykinin (BK), norepinephrine (NE), histamine (HIST), carbachol (CARB), 2-methyl-thio ATP (2MT-ATP), glutamate (GLUT), and serotonin (5-HT) were analyzed. Approximately 50% of cerebral type 2 astroglia responded to BK, NE, HIST, CARB, and 2MT-ATP whereas only 16% and 9% of the cells responded to GLUT and 5-HT, respectively. The number of neuroligands that increased calcium in individual cells ranged from 0 to 6. These responses are quite similar to those previously demonstrated in cultured cerebral type 1 astroglia. No pattern of receptor co-expression was observed for the different neuroligands tests.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
967.
The aim of this study was to compare the effects of a physical exercise test and of voluntary hyperventilation between controls and children with absence epilepsy. Eighteen children (6 controls and 12 epileptics) were studied during rest (R), a maximal physical exercise test (15 min; PE), recovery (REC) and voluntary hyperventilation (3 min; VHPV). EEG and ECG were recorded during the experiment; respiratory parameters were measured to quantify PE; plasma levels of pH, lactate, pyruvate, glucose and antiepileptic drugs were determined. A decrease in the number of absences was observed during PE whereas an increase was observed during VHPV. We found significant positive correlations between the number of children with absences, the total number of absences for each state, frequency of absences per minute and the corresponding mean plasma pH, which demonstrate that the lower the pH is, the fewer absences occur. On the other hand, there was no relationship between the number of absences and the values of other parameters. Relations between variations of the plasma value of the pH, and thus the probable cerebral value of pH, and neuronal excitability are discussed. Our results indicate that children who suffer absence epilepsy should not be discouraged from sport practice.  相似文献   
968.
Regional cerebral blood flow (rCBF) was assessed by means of HMPAO-SPECT in two experimental groups. In a control condition both groups listened to abstract words, in the experimental condition they heard five names of objects. One group was advised to form visual images of the objects, the other group was advised to form acoustic images of the sounds made by these objects. Post-experimental questionnaires revealed that most of the subjects in the acoustic imagery condition had had visual images in addition to the acoustic ones. Both imagery conditions lead to approximately equal increases of rCBF in the left inferior occipital region and in the left thalamus. Flow increases in both hippocampal regions and the right inferior and superior temporal regions were larger in the acoustic than in the visual imagery condition. It is concluded that only the activation of left inferior occipital and left thalamic regions can be interpreted as being related to modality-specific visual aspects of imagery.  相似文献   
969.
This analysis applies methods of screening to the problem of psychosis. A probability sample of 810 individuals from the Eastern Baltimore Mental Health Survey was interviewed in the self-report modality with the Diagnostic Interview Schedule and shortly thereafter by a psychiatrist. It is shown that a configuration of responses in the self-report modality can screen moderately well for psychosis, as measured by psychiatrists in the clinical modality.  相似文献   
970.
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