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   171142篇
  免费   9791篇
  国内免费   505篇
耳鼻咽喉   2224篇
儿科学   5568篇
妇产科学   3567篇
基础医学   23153篇
口腔科学   7524篇
临床医学   12618篇
内科学   38400篇
皮肤病学   4359篇
神经病学   14176篇
特种医学   5555篇
外国民族医学   26篇
外科学   21013篇
综合类   1412篇
现状与发展   1篇
一般理论   60篇
预防医学   17794篇
眼科学   3152篇
药学   10350篇
中国医学   688篇
肿瘤学   9798篇
  2023年   883篇
  2022年   1937篇
  2021年   3613篇
  2020年   2419篇
  2019年   3418篇
  2018年   4817篇
  2017年   3618篇
  2016年   3360篇
  2015年   3941篇
  2014年   5397篇
  2013年   6828篇
  2012年   10620篇
  2011年   11103篇
  2010年   5633篇
  2009年   5075篇
  2008年   8589篇
  2007年   9239篇
  2006年   8529篇
  2005年   8823篇
  2004年   8296篇
  2003年   7579篇
  2002年   5645篇
  2001年   4953篇
  2000年   4951篇
  1999年   4359篇
  1998年   1626篇
  1997年   1364篇
  1996年   1368篇
  1995年   1155篇
  1994年   1150篇
  1993年   1046篇
  1992年   2667篇
  1991年   2588篇
  1990年   2358篇
  1989年   2362篇
  1988年   2137篇
  1987年   1978篇
  1986年   1857篇
  1985年   1780篇
  1984年   1266篇
  1983年   1028篇
  1982年   585篇
  1981年   533篇
  1980年   508篇
  1979年   923篇
  1978年   613篇
  1977年   488篇
  1975年   549篇
  1974年   540篇
  1973年   540篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Cerebral blood flow tomography, by xenon 133 inhalation or HMPAO (99mTc-d, l-hexamethyl-propylene amine oxime) technetium Tc 99m injection, revealed a severe hypoperfusion in both frontal lobes of a 40-year-old woman with confirmed neuroacanthocytosis. This finding occurred in conjunction with neuropsychological deficits consistent with selective frontal lobe dysfunction. This observation is the first documentation of this type of dementia in neuroacanthocytosis.  相似文献   
92.
In a six-week double-blind randomized trial, preceded by a one-week period of single-blind placebo treatment, the efficacy and the side-effects of fluvoxamine (100-300 mg/d) (n = 24) and maprotiline (50-150 mg/d) (n = 24) were compared in moderately depressed outpatients with DSM-III Major Depression (n = 22) or Dysthymic Disorder (n = 26). Efficacy was measured by means of the Hamilton Depression Rating Scale, the Zung Depression Selfrating Scale, and a Clinical Global Impression of Severity Scale. Side-effects were evaluated by an Adverse Event Inventory and a Psychosomatic Symptom Scale. A statistically significant improvement was achieved in both treatment groups but success rates were modest: in both groups, 29% of the patients achieved a clinically significant improvement after six weeks of treatment. After six weeks of treatment, no difference in efficacy was found between fluvoxamine and maprotiline. Nausea was the most common complaint in the fluvoxamine group, while in the maprotiline group, it was dry mouth and constipation. One maprotiline-treated patient developed a convulsive attack.  相似文献   
93.
Two neonates who went into acute hypovolaemic shock due to a tight nuchal cord were successfully resuscitated. The occurrence of this life threatening complication in two low risk pregnancies emphasises the importance of having staff trained in resuscitation immediately available in the delivery unit.  相似文献   
94.
Middle latency auditory evoked responses (MLRs) were recorded in 64 premature infants; serially in 54 of them. The last recording sessions occurred at 50-52 weeks conceptional age (CA), defined as the gestational age (GA) added to the chronological age. The MLRs were analyzed for the components PO, Na and Pa, and the interpeak latency difference (IPLD) Na-PO. The detectability rate of PO and Na reached 80-90% at about 30 weeks CA. Pa reached the highest rate of about 60% at 52 weeks CA. The degree of prematurity did not result in clear differences with respect to the parameter values. Also, the side of stimulation did not influence the MLR parameter values. The latency values of the MLR components are strongly age dependent. Topographic differences were found between the sides ipsi- and contralateral to stimulation. They are, however, different for PO, Na and Pa. The influence of the state of vigilance on the parameter values could generally only be established at CA levels of about 32 and 52 weeks CA. The amplitude values at 52 weeks CA are especially sensitive for sleep or awake state. The particular pattern of age dependency of the different components and their topographic differences are consistent with a differential generation of bilateral nature. The early appearance of the response supports the generation of an early functioning subcortical structure in the auditory pathway.  相似文献   
95.
Inhibition of protein synthesis can alter cellular responsiveness to the classical anticancer drugs. The in vitro response of Chinese hamster ovary (CHO) cells to cisplatin with or without sparsomycin (Sm) was studied with the use of [3H]leucine and [methyl-3H]thymidine incorporation and clonogenic assay. Pretreatment of exponentially growing CHO cells with 1 microgram Sm/ml for 3 or 5 hours decreased [3H]leucine incorporation by 20% and resulted in significant resistance to cisplatin (P = .005). Sm in a concentration of 10 micrograms/ml reduced [3H]leucine and [methyl-3H]thymidine incorporation after 3 hours by 92 and 84%, respectively, and resulted in potentiation of the cisplatin cytotoxicity (P = .004). This effect was the same in the case of nonproliferating cells (P = .005), while protection due to Sm (1 microgram/ml) was seen only during cell proliferation. Simultaneous incubation and postincubation with Sm proved to have much less or no potentiating effect on cisplatin. The mechanisms of both protection and potentiation are still not clear, but our data indicate that Sm is a promising drug for further studies on the modulation of the cancer cell response to classical anticancer drugs.  相似文献   
96.
The diagnostic yields of bronchial washings, bronchial brushings and lung biopsy specimens were compared in 50 patients with positive Mycobacterium tuberculosis cultures. The number of positive results obtained with cultures of bronchial brushings was significantly higher than that with bronchial washings (p < 0.001). The histological study of biopsy lung material improved the rate of immediate or rapid diagnosis of tuberculosis (p<0.001).  相似文献   
97.
The use of Mixture Toxicity Indices (MTI's) is one of the more attractive approaches for describing and predicting the effects of mixtures of toxicants. For an MTI to apply to all possible mixtures of the compounds in question, it must summarize information from a model describing all possible responses of interest. A method of obtaining MTI's from response surface equations or from tolerance models similar to the toxic units model is presented. Methods of calculating several MTI's with desirable properties from multivariable probit response surfaces are demonstrated.  相似文献   
98.
Atrial electrical remodeling plays a part in recurrence of atrial fibrillation (AF). It has been related to an increase in heterogeneity of atrial refractoriness that facilitates the occurrence of multiple reentry wavelets and vulnerability to AF. AIM: To examine the relationship between dispersion of atrial refractoriness (Disp_A) and vulnerability to AF induction (A_Vuln) in patients with clinical paroxysmal AF (PAF). METHODS: Thirty-six patients (22 male; age 55+/-13 years) with > or =1 year of history of PAF (no underlying structural heart disease--n=20, systemic hypertension--n=14, mitral valve prolapse--n=1, surgically corrected pulmonary stenosis--n=1), underwent electrophysiological study (EPS) while off medication. The atrial effective refractory period (AERP) was assessed at five different sites--high (HRA) and low (LRA) lateral right atrium, high interatrial septum (IAS), proximal (pCS) and distal (dCS) coronary sinus--during a cycle length of 600 ms. AERP was taken as the longest S1-S2 interval that failed to initiate a propagation response. Disp_A was calculated as the difference between the longest and shortest AERP. A_Vuln was defined as the ability to induce AF with 1-2 extrastimuli or with incremental atrial pacing (600-300 ms) from the HRA or dCS. The EPS included analysis of focal electrical activity based on the presence of supraventricular ectopic beats (spontaneous or with provocative maneuvers). The patients were divided into group A--AF inducible (n=25) and group B--AF not inducible (n=11). Disp_A was analyzed to determine any association with A_Vuln. Disp_A and A_Vuln were also examined in those patients with documented repetitive focal activity. Logistic regression was used to determine any association of the following variables with A_Vuln: age, systemic hypertension, left ventricular hypertrophy, left atrial size, left ventricular function, duration of PAF, documented atrial flutter/tachycardia and Disp_A. RESULTS: There were no significant differences between the groups with regard to clinical characteristics and echocardiographic data. AF was inducible in 71% of the patients and noninducible in 29%. Group A had greater Disp_A compared to group B (105+/-78 ms vs. 49+/-20 ms; p=0.01). Disp_A was >40 ms in 50% of the patients without A_Vuln and in 91% of those with A_Vuln (p=0.05). Focal activity was demonstrated in 14 cases (39%), 57% of them with A_Vuln. Disp_A was 56+/-23 ms in this group and 92+/-78 ms in the others (p=0.07). Using logistic regression, the only predictor of A_Vuln was Disp_A (p=0.05). CONCLUSION: In patients with paroxysmal AF, Disp_A is a major determinant of A_Vuln. Nevertheless, the degree of nonuniformity of AERP appears to be less important as an electrophysiological substrate for AF due to focal activation.  相似文献   
99.
BACKGROUND: We reviewed the publication record of all protocols submitted to the Capital District Health Authority Research Ethics Board (REB) in Halifax, Nova Scotia, for the period 1995-1996. Because of a heightened awareness of the issue, we hypothesized that there would be less publication bias (a failure to report negative results) and a higher publication rate from completed studies, than previously reported. METHODS: Closed studies were identified from the REB database. Publications were identified by the investigators, requests from sponsors, and a literature review. For each publication, we identified authors, title, journal, number of subjects enrolled, and whether or not the publication was a report of a randomized clinical trial. Comparisons were done using a Student's t test, the Chi-square statistic, or Fisher's exact test as appropriate. RESULTS: From the database of closed studies, 106 remained unpublished, while completed investigations resulted in 84 publications (44% publication rate). The median time to publication was 32.5 months. Publication of statistically significant results occurred in 71/84 trials. Publication of protocols submitted by departments ranged from 91% (anesthesia; 10/11) to 25% [nursing; 2/8 (P<0.05)]. Trials investigating new drugs in Phase 3 or 4 studies were more likely to be published than trials investigating agents in Phase 1 or 2 (P<0.05), and were less likely to be published if sponsored by a pharmaceutical company (P<0.05). CONCLUSIONS: Publication bias continues to be a problem, particularly for early phase investigative studies. Our results suggest that a different approach is required to reduce publication bias. The role that REBs and peer-reviewed journals might play requires further exploration.  相似文献   
100.
BACKGROUND Dermatologic procedures often cause some degree of pain. A self-warming patch containing lidocaine and tetracaine (L/T) was developed to provide topical local anesthesia prior to painful procedures.
OBJECTIVES To evaluate the safety and efficacy of a self-warming L/T patch to provide anesthesia in adult patients undergoing minor dermatologic procedures.
METHODS An active or placebo study drug was placed on adults 30 minutes prior to minor dermatologic surgical procedures in a prospectively randomized, double-blinded manner. Subcutaneous lidocaine injection was available during the procedure as a rescue medication if requested by the subject. Immediately following the procedure, the subjects, the investigator, and an independent observer rated pain intensity and adverse events were recorded.
RESULTS Patient-reported pain intensity was significantly lower in the L/T patch group (   p < .001  ). Investigators and an independent observer rated the pain in the L/T patch group to be less than in the placebo patch group (   p = .004  and   p < .001  , respectively). Forty-nine percent of patients in the placebo group required rescue subcutaneous lidocaine compared with 22% in the L/T patch study group (   p = .008  ). One patient in the L/T patch group reported a transient moderate burning sensation.
CONCLUSION The self-warming L/T patch was effective in providing clinically useful local anesthesia for minor dermatologic procedures in adult patients.
ZARS, INC., PROVIDED SUPPORT VIA A SPONSORED RESEARCH GRANT TO THE UNIVERSITY OF MIAMI.  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