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   5239篇
  免费   488篇
  国内免费   12篇
耳鼻咽喉   114篇
儿科学   273篇
妇产科学   115篇
基础医学   614篇
口腔科学   82篇
临床医学   574篇
内科学   950篇
皮肤病学   70篇
神经病学   402篇
特种医学   392篇
外科学   691篇
综合类   88篇
一般理论   4篇
预防医学   473篇
眼科学   81篇
药学   303篇
中国医学   5篇
肿瘤学   508篇
  2021年   78篇
  2020年   47篇
  2019年   108篇
  2018年   101篇
  2017年   77篇
  2016年   62篇
  2015年   84篇
  2014年   129篇
  2013年   172篇
  2012年   245篇
  2011年   236篇
  2010年   148篇
  2009年   131篇
  2008年   208篇
  2007年   214篇
  2006年   192篇
  2005年   227篇
  2004年   210篇
  2003年   167篇
  2002年   179篇
  2001年   178篇
  2000年   164篇
  1999年   150篇
  1998年   86篇
  1997年   83篇
  1996年   76篇
  1995年   75篇
  1994年   60篇
  1993年   61篇
  1992年   122篇
  1991年   109篇
  1990年   119篇
  1989年   157篇
  1988年   136篇
  1987年   132篇
  1986年   114篇
  1985年   105篇
  1984年   83篇
  1983年   63篇
  1982年   41篇
  1981年   45篇
  1980年   36篇
  1979年   59篇
  1978年   37篇
  1977年   38篇
  1976年   41篇
  1974年   33篇
  1973年   30篇
  1972年   39篇
  1971年   29篇
排序方式: 共有5739条查询结果,搜索用时 31 毫秒
21.
22.
The prognostic significance of the tumour activities of 2 steroid receptors, those for oestrogen (ER) and for progestogen (PgR), has been studied in 372 patients with breast cancer, in whom follow-up was available for 2-6 years (median 41 months). Of 252 patients with operable disease, 75.8 per cent had ER-positive tumours and 46.4 per cent had PgR-positive tumours, though a small additional fraction (6.3 per cent) had an equivocal PgR assay result. For the 236 patients with unequivocal receptor status, the relationships between disease-free interval or overall survival and receptor activity and other factors were evaluated by univariate and multivariate analyses. The latter revealed that only tumour size, node status, menstrual status and ER status related significantly to both disease-free interval and survival, though adjuvant therapy also related to disease-free interval, and tumour grade related to survival. It is concluded that measurements of PgR activity do not add to the prognostic significance of ER status.  相似文献   
23.
Many physiological variables known or thought to affect erythrocyte Na+,K+-cotransport are altered in pregnancy. The interrelationships of Na+,K+-cotransport and pregnancy were therefore examined. Values were elevated by more than 30% in both second and third trimesters with a return towards non-pregnant levels in the postpartum period. Although pregnancy was also associated with elevated plasma cholesterol, renin activity and aldosterone, there was no significant relationship within the pregnant group between Na+,K+-cotransport and any of these factors. No change could be demonstrated in Na+,K+-cotransport values after 7 days of either high (greater than 250 mmol/day) or low (less than 50 mmol/day) sodium intake and values for those who developed pregnancy-associated hypertension (PAH, pre-eclampsia) were not significantly different from those in continuously normotensive women in either the second or the third trimesters of pregnancy.  相似文献   
24.
Several systems have been developed to monitor and feedback information about a client's responses to psychotherapy as a method of enhancing client outcome. The current study divided 1020 clients into four groups (two experimental and two control) to determine if feedback regarding client progress, when provided to a therapist, affected client outcome and number of sessions attended. Results showed that feedback increased the duration of treatment and improved outcome for clients identified as potential treatment failures thereby replicating an earlier study using nearly identical methodology. Nearly twice as many clients in the feedback group achieved clinically significant or reliable change and fewer were classified as deteriorated by the time treatment ended. For those clients who were predicted to have a positive response to treatment, feedback to therapists resulted in an equal number of treatment sessions and equivalent outcomes compared to the no feedback controls. The results are discussed in terms of quality management in routine clinical practice and the need to base treatment decisions on clients' response to treatment rather than arbitrary session limits. Suggestions for additional research aimed at enhancing the effects of feedback on client outcome are made. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
25.
The exact opioid-sensitive receptors participating in EtOH-seeking behaviors remains unclear. Previous studies have reported higher densities of micro-opioid receptor binding in the nucleus accumbens (NACC) of P relative to NP rats; however, no differences were seen in delta-receptor binding. In contrast to the NACC, substantially lower levels of micro-receptor binding have been observed in the ventral tegmental area (VTA) of both P and NP rats, albeit no line differences have been observed. In the present study, opioid receptors in the NACC, VTA, and hippocampus were evaluated for their capacity to regulate both EtOH- and saccharin-motivated behaviors in the genetically selected alcohol-preferring (P) rat. To accomplish this, nalmefene, an opiate antagonist with preferential binding affinity for the micro-opioid receptor was unilaterally or bilaterally infused during concurrent availability of 1 h daily EtOH (10% v/v) and saccharin (0.025 or 0.050% w/v) solutions. Rats performed under a two-lever fixed ratio (FR) schedule in which four responses on one lever produced the EtOH solution, and four on a second lever produced the saccharin solution. The results demonstrated that when responding maintained by both EtOH and saccharin are matched at basal levels, unilateral (1-60 microg) or bilateral (0.5-10 microg) microinjections of nalmefene into the NACC produced selective dose-dependent reductions on responding maintained by EtOH. Unilateral (40, 60 microg) and bilateral (10 microg) VTA infusions were also observed to selectively reduced EtOH responding; however, greater nalmefene doses were required and the magnitude of suppression on EtOH responding was markedly less compared with the NACC. The greater sensitivity of nalmefene to suppress EtOH responding in the NACC is likely due to the greater number of opioid receptors in the NACC relative to the VTA. Only bilateral infusion of the 40 microg dose in the NACC and VTA suppressed responding maintained by both EtOH and saccharin. In contrast, intrahippocampal infusions dose dependently suppressed EtOH- and saccharin-maintained responding over a range of doses (1-20 microg). The present study provides evidence that nalmefene suppresses EtOH-motivated behaviors via blockade of opioid receptors within the NACC and VTA, and under various dose conditions both reinforcer and neuroanatomical specificity can be observed.  相似文献   
26.
Normal and diseased isolated lungs: high-resolution CT   总被引:8,自引:0,他引:8  
  相似文献   
27.
The radiopacity of ingested medications   总被引:1,自引:0,他引:1  
We investigated prospectively the radiopacity of 312 pills found on a university hospital formulary by first radiographing them through 15 and 25 cm of water to duplicate the radiodensity of the human body. The pills that were radiodense through water were studied in a human cadaver model, and their densities were quantified by computed tomography (CT). Thirty-five of 312 pills were radiopaque in 15 cm or more of water, and 23 of these pills were radiopaque on a plain radiograph when placed in the stomach of a cadaver. Common mnemonics used to identify radiopaque pills were found to be incomplete and inadequate. Chloral hydrate, iron-containing preparations, calcium carbonate, iodinated compounds, acetazolamide, busulfan, and potassium preparations were consistently radiopaque. Antihistamines, phenothiazines, and tricyclic antidepressants demonstrated varying radiopacity. There was varying radiopacity among the same medications made by different manufacturers. The presence of an enteric coating did not assure that the pill would be radiopaque. Merely radiographing a pill that has been placed on a standard radiograph cassette will make pills that are actually radiolucent in the body appear radiopaque. This test cannot be used to predict radiopacity in vivo. Visibility when radiographed through 15 cm or more of water and a CT radiodensity of more than 1,300 Hounsfield units are predictors of the radiopacity of a pill in the stomach of a cadaver model on a standard KUB radiograph. Variables, such as the size of the patient, the arrangement of pills in the stomach, air contrasting a pill, and the specific composition of the enteric coating or the pillmatrix, affect the radiodensity of pills.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
28.
The oestrogen receptor (ER) is considered to be an essential component of the mechanism of response of a breast tumour to endocrine therapy, but ER measurements have proved to have only modest predictive value. In the present study, we have examined ER status by both immunocytochemical assay (ER-ICA) on a fine needle aspirate and by radioligand-binding assay (DCC) on an excised portion of tumour. There was a correlation between the ER level detected by the two assays (Spearman's r = 0.77 for DCC versus ER-ICA staining intensity, r = 0.70 for DCC versus ER-ICA percentage of cells stained, P < 0.0001, n = 137 in each case). Each assay showed an increasing proportion of ER+ve results with increasing patient age. In the case of ER+ve tissues only, while ER concentration by DCC assay increased steadily with age (r = 0.39, P < 0.0001, n = 108), the ER-ICA assay revealed that, staining intensity increased with age (r = 0.26, P = 0.001, n = 149) but the percentage of cells stained did not (r = 0.08, P = NS, n = 149). It is concluded that increasing endocrine responsiveness with advancing age could reflect the increasing proportion of ER+ve tumours with increased levels of ER per cell (as indicated by staining intensity) rather than increasing proportion of ER+ve cells.  相似文献   
29.
The development of methemoglobinemia requires rapid recognition, confirmation, and treatment. This case study describes the development, diagnosis, and management of a 63-year-old male scheduled for a laparoscopic cholecystectomy with an intraoperative cholangiogram who developed methemoglobinemia after benzocaine was given for intubation.  相似文献   
30.
Between March 1985 and December 1991, mediastinitis developed in 12 of 420 cardiac transplantation patients (2.8%). The mortality rate in this group of patients was 8.3% (1/12). Actuarial survival (1 year, 75%; and 5 years, 65%) was not significantly different from that of the group without mediastinitis (1 year, 88%; and 5 years, 75%). A higher percentage of the patients in the group with mediastinitis were listed as UNOS status 1 (50% versus 35%) and had a history of previous sternotomies (58% versus 44%). The presentation of mediastinitis was typical. Computed tomographic scanning with or without aspiration was a valuable adjunct in the diagnosis of mediastinitis. Induction immunotherapy with minimal steroids in the perioperative period was used in all patients. This may contribute to the patients' ability to mount an appropriate and effective response to infection, permitting earlier diagnosis. The debridement irrigation technique used in 8 of 12 patients had a low success rate of 33%, whereas the debridement muscle flap technique used in 4 of 12 was 100% successful in eliminating infection.  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