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   11534篇
  免费   1174篇
  国内免费   21篇
耳鼻咽喉   115篇
儿科学   415篇
妇产科学   295篇
基础医学   1662篇
口腔科学   303篇
临床医学   1471篇
内科学   2151篇
皮肤病学   119篇
神经病学   1127篇
特种医学   319篇
外国民族医学   3篇
外科学   1393篇
综合类   250篇
一般理论   12篇
预防医学   1374篇
眼科学   123篇
药学   853篇
中国医学   6篇
肿瘤学   738篇
  2022年   74篇
  2021年   179篇
  2020年   132篇
  2019年   180篇
  2018年   200篇
  2017年   140篇
  2016年   168篇
  2015年   206篇
  2014年   298篇
  2013年   390篇
  2012年   609篇
  2011年   657篇
  2010年   314篇
  2009年   342篇
  2008年   541篇
  2007年   558篇
  2006年   561篇
  2005年   567篇
  2004年   487篇
  2003年   483篇
  2002年   459篇
  2001年   369篇
  2000年   342篇
  1999年   271篇
  1998年   121篇
  1997年   119篇
  1996年   97篇
  1995年   115篇
  1994年   102篇
  1993年   97篇
  1992年   220篇
  1991年   220篇
  1990年   218篇
  1989年   191篇
  1988年   186篇
  1987年   175篇
  1986年   203篇
  1985年   193篇
  1984年   143篇
  1983年   130篇
  1982年   87篇
  1981年   90篇
  1980年   74篇
  1979年   145篇
  1978年   124篇
  1977年   104篇
  1976年   90篇
  1974年   94篇
  1973年   95篇
  1972年   84篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Phenylketonuria (PKU), an inborn error of phenylalanine metabolism, has been shown to be a risk factor for tardive dyskinesia (TD). In male psychiatric patients there was a significant relationship between TD and measures of plasma phenylalanine following ingestion of a standardized phenylalanine dose that was indicative of higher brain availability of phenylalanine in patients with TD. In addition, a medical food formulation consisting of branched chain amino acids, which compete with phenylalanine for transport across the blood-brain barrier, has been demonstrated to be an efficacious treatment for TD. Cumulatively these findings suggested that TD was related to phenylalanine metabolism and thus that sequence variants in the gene for phenylalanine hydroxylase (PAH), the rate-limiting enzyme in the catabolism of phenylalanine, could be associated with TD susceptibility. Genetic screening of PAH in a group of 123 psychiatric patients revealed ten sequence polymorphisms and two mutations, but none appeared to be a significant risk factor for TD.  相似文献   
2.
Background: Previous studies have shown that propofol and sevoflurane enhance the function of [gamma]-aminobutyric acid type A (GABAA) receptors. However, it is not known whether these two drugs modulate the same molecular pathways. In addition, little is known about receptor function in the presence of both propofol and sevoflurane. The aim of this study was to better understand the interactions of propofol and sevoflurane with the GABAA receptor.

Methods: Wild-type [alpha]1, [beta]2, [gamma]2s GABAA receptor subunit complementary DNAs were transfected into human embryonic kidney cells grown on glass coverslips using a calcium phosphate transfection method. After transfection (36-72 h), cells were whole cell patch clamped and exposed to combinations of the following: 0.3-1,000 [mu]m [gamma]-aminobutyric acid (GABA), 0-10 [mu]m propofol, and 0-1,650 [mu]m sevoflurane. Chemicals were delivered to the cells using two 10-channel infusion pumps and a rapid solution exchanger.

Results: Both propofol and sevoflurane alone enhanced the amplitude of GABAA receptor responses to submaximal concentrations of GABA in a dose-dependent manner. The enhancement was underpinned by an increase in the apparent affinity of the receptor for GABA. Coapplication of both anesthetics further enhanced the apparent affinity of the receptor for GABA.  相似文献   

3.
OBJECTIVES: This study investigates posttraumatic stress disorder (PTSD) and its associated risk factors in a random, national, Canadian sample of United Nations peacekeeping veterans with service-related disabilities. METHODS: Participants included 1016 male veterans (age < 65 years) who served in the Canadian Forces from 1990 to 1999 and were selected from a larger random sample of 1968 veterans who voluntarily and anonymously completed a general health survey conducted by Veterans Affairs Canada in 1999. Survey instruments included the PTSD Checklist-Military Version (PCL-M), Center for Epidemiological Studies-Depression Scale (CES-D), and questionnaires regarding life events during the past year, current stressors, sociodemographic characteristics, and military history. RESULTS: We found that rates of probable PTSD (PCL-M score > 50) among veterans were 10.92% for veterans deployed once and 14.84% for those deployed more than once. The rates of probable clinical depression (CES-D score > 16) were 30.35% for veterans deployed once and 32.62% for those deployed more than once. We found that, in multivariate analyses, probable PTSD rates and PTSD severity were associated with younger age, single marital status, and deployment frequency. CONCLUSIONS: PTSD is an important health concern in the veteran population. Understanding such risk factors as younger age and unmarried status can help predict morbidity among trauma-exposed veterans.  相似文献   
4.
SUPER IF ON     
Meyer  Harriet S. 《JAMA》2006,295(7):833
  相似文献   
5.
A murine monoclonal antibody PASE/4LJ to prostatic acid phosphatase (PAP) was used to immunostain a wide variety of sections of benign and malignant tissues (654 blocks). Non-neoplastic adult and fetal prostatic glands, primary and metastatic prostatic carcinomas, and scattered cells in prostatic and penile urethra were positive. Rat, dog and rabbit prostates were negative. Nine of 400 tumours of non-prostatic origin showed some positivity: 6/36 carcinoids, 1/9 islet cell tumours, 1/55 ovarian adenocarcinomas (serous) and one carcinosarcoma of the lung (epithelial portion). Positive staining was seen in islet cells in 4/5 specimens of normal pancreas, and in 4/9 blocks of normal pancreas surrounding a pancreatic tumour. Loops of Henle, maculae densae, and distal tubules in 10/10 fetal and 2/9 adult kidneys were also positive, with proximal tubules and collecting ducts negative. All other 159 blocks of non-neoplastic adult and fetal tissues were negative. The antibody was also affinity purified from ascitic fluid, and shown not to inhibit the enzyme activity of prostatic acid phosphatase.  相似文献   
6.
Summary Candida endocarditis is an unusual but severe complication of systemic infection caused byCandida albicans and occasionally by other fungal species. We describe seven cases that occurred during a period of 20 years in western Sweden. In four cases infections were located on prosthetic valves and in three cases native valves were involved. Three patients died of the disease in the acute phase. A definite diagnosis was established in one of four survivors. This patient had an aortic valve endocarditis and a saddle embolisation and was treated with immediate surgery, followed by intensive treatment with liposomal amphotericin B + flucytosine. Fungal endocarditis is still a serious disease with a high mortality and whenever the diagnosis is suspected, antifungal therapy must be started and transesophageal sonography should be performed to visualize vegetations. Immediate surgery should be considered.
Pilzendokarditis — Bericht über sieben Fälle und kurze Literaturübersicht
Zusammenfassung DieCandida-Endokarditis ist eine seltene, aber schwere Komplikation einer systemischen Infektion durchCandida albicans und gelegentlich auch durch andere Pilzspezies. Wir berichten über sieben Fälle, die in einem Zeitraum von 20 Jahren in Westschweden beobachtet wurden. In vier Fällen waren Klappenprothesen und in drei Fällen natürliche Klappen betroffen. Drei Patienten starben in der akuten Phase an der Krankheit. Bei einem der vier überlebenden Patienten konnte die Diagnose eindeutig gesichert werden. Dieser Patient hatte eine Aortenklappenendokarditis und einen reitenden Embolus. Er wurde sofort operiert und hochdosiert mit liposomalem Amphotericin B und mit Flucytosin behandelt. Die Pilzendokarditis ist nach wie vor eine ernste, mit hoher Letalität belastete Krankheit. Die antimykotische Therapie muß bereits beim ersten Verdacht begonnen werden. Um Vegetationen nachzuweisen, sollte die transösophageale Sonographie durchgeführt werden. Ein sofortiges chirurgisches Eingreifen ist zu erwägen.
  相似文献   
7.
8.
Bay K 8644 potentiated and augmented 5-hydroxytryptamine (5-HT)-induced contractions in the rabbit, isolated aorta preparation, as manifested in leftward shift and increase in the asymptote of 5-HT E/[A] (effect vs concentration) curves. The operational model of agonism (Black & Leff, 1983) was used to analyse this interaction and the concomitant effects of irreversible receptor alkylation by phenoxybenzamine. The competitive effects of spiperone in the presence and absence of Bay K 8644 were also examined. From these analyses it is concluded that Bay K 8644 elicits its potentiating effects by increasing the efficacy of 5-HT at the 5-HT2 receptor with no alteration in affinity. This is consistent with the known effect of Bay K 8644 of causing an increase in the functional concentration of plasmalemmal calcium channels coupled to the 5-HT2 receptors in this preparation. The positively co-operative shape of the 5-HT E/[A] curves obtained in the aorta and the quantitative nature of their potentiation by Bay K 8644 indicated that the coupling of 5-HT2 receptor occupancy to intracellular calcium concentration is linear and that the co-operativity resides in the subsequent relation between intracellular calcium and pharmacological effect. Bay K 8644 may serve as a probe for differentiating between the types of calcium channels that transduce 5-HT receptor-mediated effects in different systems. Such information would be useful in the classification of agonist interactions with 5-HT receptors.  相似文献   
9.
Total energy expenditure (TEE) was measured by doubly labeled water in 13 preoperative patients undergoing elective coronary artery surgery and compared to resting energy expenditure (REE) measured by indirect calorimetry (IC) calculated from the Harris-Benedict (HB) formula or from formulas based on midarm circumference and arm muscle circumference. Mean REE measured by IC and calculated from the HB, midarm circumference, arm muscle circumference formulas were 62, 75, 62, and 69%, respectively, of TEE measured by doubly labeled water. REE measured by IC correlated significantly with that predicted by the HB (p = 0.006) but not the anthropometric formulas. The relationship between REE derived from anthropometric predictive formulas and REE measured by IC is altered in ischemic heart disease.  相似文献   
10.
A quasi-experimental study was conducted to evaluate the effect of preoperative interviews on patients' anxiety levels. A convenience sample of 60 was assigned between two groups of equal size: a treatment group in which subjects were interviewed by a perioperative nurse or a control group in which subjects were not interviewed. All subjects completed state-trait Anxiety Inventory questionnaires. Group comparison using analysis of covariance showed subjects who were interviewed by the perioperative nurse reported significantly less anxiety than control group subjects.  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