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   8078篇
  免费   618篇
  国内免费   13篇
耳鼻咽喉   130篇
儿科学   252篇
妇产科学   238篇
基础医学   1166篇
口腔科学   112篇
临床医学   849篇
内科学   1763篇
皮肤病学   111篇
神经病学   747篇
特种医学   192篇
外科学   914篇
综合类   135篇
一般理论   9篇
预防医学   808篇
眼科学   65篇
药学   523篇
中国医学   12篇
肿瘤学   683篇
  2023年   66篇
  2022年   71篇
  2021年   200篇
  2020年   116篇
  2019年   212篇
  2018年   248篇
  2017年   157篇
  2016年   178篇
  2015年   212篇
  2014年   270篇
  2013年   399篇
  2012年   574篇
  2011年   574篇
  2010年   314篇
  2009年   249篇
  2008年   416篇
  2007年   423篇
  2006年   405篇
  2005年   359篇
  2004年   336篇
  2003年   308篇
  2002年   300篇
  2001年   176篇
  2000年   174篇
  1999年   155篇
  1998年   75篇
  1997年   53篇
  1996年   54篇
  1995年   52篇
  1994年   60篇
  1993年   42篇
  1992年   117篇
  1991年   122篇
  1990年   94篇
  1989年   101篇
  1988年   103篇
  1987年   93篇
  1986年   93篇
  1985年   75篇
  1984年   51篇
  1983年   48篇
  1982年   34篇
  1981年   30篇
  1980年   32篇
  1979年   66篇
  1978年   50篇
  1976年   34篇
  1974年   32篇
  1970年   26篇
  1966年   26篇
排序方式: 共有8709条查询结果,搜索用时 15 毫秒
41.
15 chronic cluster headache patients in whom pain was induced by nitroglycerin received acute intravenous treatment with a calcium entry blocker. At the time of peak pain we noted a sudden decrease after the Verapamil injection. The mechanism by which the calcium entry blocker afforded relief is unlikely to have been vasodilatation in patients whose blood vessels had just been dilated by nitroglycerin. A more probable mechanism is blockade of the release of the pain-inducing neurotransmitters. The vasodilatation phase is not a primary factor in the onset of pain.
Sommario Sono stati studiati 15 soggetti affetti da Cluster cronica inducendo loro la crisi dolorosa con Trinitrina, trattandoli poi con calcio antagonista (Verapamil) per via endovenosa. Al momento dell'apice del dolore, valutato dal paziente con un analogo visivo, la somministrazione di Verapamil endovena, determina una rapida estinzione del dolore. L'azione efficace del Ca-antagonista non può sicuramente essere rapportata alla vasodilatazione poiché la crisi dolorosa insorge già in una fase di vasodilatazione per l'azione della Trinitina. Il meccanismo d'azione più probabile è il blocco del release di neurotrasmettitori inducenti l'attacco doloroso. Si sottolinea che la vasodilatazione non è il fattore primario dell'induzione del dolore.
  相似文献   
42.
Crohn''s disease is well known for its multiple intestinal complications. The chronic nature and fibrous inflammation which invariably accompanies this disease explains the relative rarity of free intestinal perforation. The true incidence of free bowel perforation is difficult to assess but 1-2% is the anticipated occurrence during the course of illness. We present a case of Crohn''s disease which presented for the first time with acute colonic perforation, an extremely rare entity, and review the current world literature.  相似文献   
43.
The effect of increasing age on quality of life, survival, and risk of reoperation was studied in 2479 patients followed up prospectively 2 to 20 years after myocardial revascularization. Quality of life was determined from annual questionnaires, which we used to calculate a health status index from the patient's symptomatic status and subjective response to the operation, which was graded between zero and 1.00 (asymptomatic). Four age groups were studied: age 49 years or less (AG40), 50 to 59 years (AG50), 60 to 69 years (AG60), and 70 years or older (AG70). Associated problems (left ventricular aneurysm, valve disease, acute myocardial infarction) necessitating treatment were present in 17% (61/361) of AG40 patients, 19% (165 of 859) of AG50 patients, 23% (213/927) of AG60 patients, and 31% (102/332) of AG70 patients. The hospital mortality rate was higher in older patients undergoing combined procedures but not in patients undergoing coronary bypass grafts only. Probability of survival and health status indexes were calculated excluding patients with valve disease and cardiogenic shock. Probability of survival was significantly better (p less than 0.001 by the Wilcoxon test) in patients less than age 60 than in those 60 years or older, but in patients with an ejection fraction greater than or equal to 0.40, probability of survival at 12 years was 0.64 (age less than 60) versus 0.62 (age greater than or equal to 60). The actuarial risk of reoperation, calculated as the difference between probability of survival and probability of survival without reoperation, progressively increased in younger patients but not in patients aged 60 years or older. At 15 years, the reoperation rates were 26% (AG40), 14% (AG50), 5% (AG60), and 7% (AG70). Mean health status index for years 1 to 5 was 0.85 in AG40 patients, 0.84 in AG50 patients, 0.89 in AG60 patients, and 0.90 in AG70 patients; for years 6 to 10, 0.81, 0.80, 0.86, and 0.89; and for years 11 to 15, 0.77, 0.78, 0.84, and 0.84, respectively. Thus quality of life after myocardial revascularization is better, improvement lasts longer, and reoperation rate is less in patients aged 60 years or older.  相似文献   
44.
Two cases, carefully selected from a longitudinal, prospective investigation of the relationship between psychosocial variables and postsurgical adjustment to a penile prosthesis implantation, were studied intensively. In both cases, the patient and sexual partner were assessed, presurgically, on a number of psychological, marital, and sexual functioning variables; their subsequent satisfaction with the prosthesis, and their psychological, marital, and sexual adjustment were measured at 6 and 12 months postsurgery. Despite many similarities in medical aspects of the surgery, for one couple a successful outcome was evidenced, whereas the other couple demonstrated a therapeutic failure despite the technical success of the surgery. Psychosocial differences between the couples were identified as they may relate to the discordant outcomes observed. Clinical implications of these results are discussed, as are the strengths and weaknesses of our methodological approach.  相似文献   
45.
A theoretical model of prevention addressing adolescents at-risk of offending was developed then utilised to assess a primary and secondary prevention program. The study of the wilderness-based practise was conducted between September 1992 and October 1994, adopting a pre-post-follow-up quasi-experimental design using waiting periods to establish treatment and control groups. Maturational changes were gauged over a 12 month period of 44 male and 18 female voluntary Australian adolescents between the ages of 15 and 25 years. Significant differences between the treatment and control groups in the psychometric areas of general self-esteem and self-actualisation were found establishing positive program effect on participants. Further, the long term effect of this program in preventing participants initial contact with court proceedings or reducing further involvement respectively, over a twelve month period was substantiated. It was shown that following this experience post program goals of employment and education for adolescents at-risk were positively influenced.  相似文献   
46.
OBJECTIVE AND DESIGN: Neutrophil-derived hypochlorous acid (PMN-HOCL) is a potent bactericidal and fungicidal agent. Neutrophils from patients with multiple organ failure (MOF) have an altered ability to inhibit Candida albicans. Conversely antifungal agents are effective in decreasing mortality in MOF patients with fungaemia. We determined the effect on the rate of production of PMN-HOCL in a series of MOF patients with C. albicans fungaemia when antifungal agents are administered. SUBJECTS AND METHODS: Eleven patients with MOF were recruited. Four patients had culture-positive C. albicans fungaemia (group 1) and 7 patients with MOF but without C. albicans fungaemia acted as controls (group 2). HOCL assays were performed on peripheral blood PMN obtained from group 1 and group 2 patients. RESULTS: The maximum PMN-HOCL production rate for group 1 increased from 0.24 nmol/million PMN/min to 0.8 nmol/million PMN/min after treatment with antifungal agents (p < 0.01) (Mann-Whitney U test) whereas the PMN-HOCL kinetic (rate) curves for group 1 post-treatment and for group 2 were similar (student's-t-test). CONCLUSIONS: These findings suggest that antifungal treatment improve PMN-HOCL production in MOF patients with C. albicans fungaemia and may improve the effectiveness in eradicating the organism.  相似文献   
47.
Both HIV infection and methamphetamine dependence can be associated with brain dysfunction. Little is known, however, about the cognitive effects of concurrent HIV infection and methamphetamine dependence. The present study included 200 participants in 4 groups: HIV infected/methamphetamine dependent (HIV+/METH+), HIV negative/methamphetamine dependent (HIV-/METH+), HIV infected/methamphetamine nondependent (HIV+/METH-), and HIV negative/methamphetamine nondependent (HIV-/METH-). Study groups were comparable for age, education, and ethnicity, although the HIV-/METH- group had significantly more females. A comprehensive, demographically corrected neuropsychological battery was administered yielding a global performance score and scores for seven neurobehavioral domains. Rates of neuropsychological impairment were determined by cutoff scores derived from performances of a separate control group and validated with larger samples of HIV+ and HIV- participants from an independent cohort. Rates of global neuropsychological impairment were higher in the HIV+/METH+ (58%), HIV-/METH+ (40%) and HIV+/METH- (38%) groups compared to the HIV-/METH- (18%) group. Nonparametric analyses revealed a significant monotonic trend for global cognitive status across groups, with least impairment in the control group and highest prevalence of impairment in the group with concurrent HIV infection and methamphetamine dependence. The results indicate that HIV infection and methamphetamine dependence are each associated with neuropsychological deficits, and suggest that these factors in combination are associated with additive deleterious cognitive effects. This additivity may reflect common pathways to neural injury involving both cytotoxic and apoptotic mechanisms.  相似文献   
48.
Social learning theory-based models have recently provided the foundation for a series of twelve controlled human immunodeficiency virus (HIV) risk reduction intervention studies that have examined sexual behavior change. These interventions have been tested with adolescents, gay and bisexual men, inner-city women, college students, and seriously mentally ill adults. We report the first meta-analysis of these intervention studies. We found that, as expected, the mean weighted effect of HIV-risk reduction interventions on behavioral outcomes was positive and strongly significant (d+=0.25). Moreover, the studies’ effect sizes were consistently positive, ranging from 0.11 to 0.53, and were largest when the outcomes were measured close in time to the intervention. We discuss other methodological challenges that, if solved, should enhance the success of future HIV-risk reduction interventions.  相似文献   
49.
1. Subepidermal injection of histamine solutions in isotonic saline in four subjects evoked whealing after a mean delay of 2.6 min, this estimate being derived by regression modelling. 2. Wheal growth was better modelled by the logarithm of time than by time, suggesting that wheal size depends upon assisted diffusion of histamine in the dermis. 3. Wheal growth was piecemeal, not continuous, consistent with the successive involvement of neighbouring vascular territories. 4. Wheal growth was completed by 9 min after injection.  相似文献   
50.
The projections of the superficial layers of the superior colliculus to the pulvinar nucleus in Tupaia were reexamined by injecting WGA-HRP into the tectum. The main result was finding two different patterns of terminations in the pulvinar nucleus: a zone remote from the lateral geniculate nucleus, which occupies the dorsomedial and caudal poles of the pulvinar nucleus, was almost entirely filled with terminals in every case irrespective of the location of the injection site; and a second division of the pulvinar nucleus, adjacent to the lateral geniculate nucleus, contained irregular patches--much more densely populated--and the distribution of patches varied from case to case. We call the first projection "diffuse" and the patchy projection "specific." Next we injected several divisions of the extrastriate visual cortex to find the cortical target of each pathway. The diffuse path terminates in the ventral temporal area (Tv). The specific path terminates in the dorsal temporal area (Td) and area 18. We speculated about the significance of the two pathways: the specific path may be responsible for the preservation of vision after removal of the striate cortex; the diffuse path may have an important place in the evolution of the visual areas of the temporal and occipital lobe. We argued that the target of the diffuse path is in a position to relate limbic and visual impulses and relay the product of such integration to the other visual areas, striate as well as extrastriate cortex.  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