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   5580篇
  免费   631篇
  国内免费   51篇
耳鼻咽喉   88篇
儿科学   199篇
妇产科学   167篇
基础医学   688篇
口腔科学   82篇
临床医学   651篇
内科学   1554篇
皮肤病学   100篇
神经病学   617篇
特种医学   363篇
外科学   688篇
综合类   71篇
一般理论   2篇
预防医学   297篇
眼科学   136篇
药学   293篇
中国医学   3篇
肿瘤学   263篇
  2023年   61篇
  2021年   55篇
  2020年   112篇
  2019年   66篇
  2018年   136篇
  2017年   107篇
  2016年   116篇
  2015年   116篇
  2014年   152篇
  2013年   229篇
  2012年   178篇
  2011年   166篇
  2010年   156篇
  2009年   184篇
  2008年   150篇
  2007年   207篇
  2006年   188篇
  2005年   173篇
  2004年   169篇
  2003年   136篇
  2002年   144篇
  2001年   168篇
  2000年   148篇
  1999年   145篇
  1998年   131篇
  1997年   137篇
  1996年   111篇
  1995年   105篇
  1994年   83篇
  1993年   76篇
  1992年   137篇
  1991年   128篇
  1990年   136篇
  1989年   152篇
  1988年   136篇
  1987年   105篇
  1986年   118篇
  1985年   121篇
  1984年   99篇
  1983年   85篇
  1982年   62篇
  1981年   62篇
  1980年   60篇
  1979年   97篇
  1978年   73篇
  1977年   61篇
  1976年   60篇
  1975年   44篇
  1974年   67篇
  1973年   53篇
排序方式: 共有6262条查询结果,搜索用时 15 毫秒
71.
72.
The perioperative changes in the serum concentration of creatine phosphokinase (CPK) and its isoenzymes MM, MB, and BB and of lactic dehydrogenase (LDH) and its isoenzymes LDH1 to LDH5 were determined during craniotomy in order to distinguish operation-induced changes in these enzymes from those due to acute myocardial infarction and malignant hyperthermia. Twenty-eight male patients, 29 to 76 years of age (mean +/- SD = 58 +/- 13.2 years), undergoing craniotomy for tumor reseaction (n = 26) or cerebral artery aneurysm clipping (n = 2) were included in this study. Ten serial blood samples were obtained from each patient: one sample before and another after induction of anesthesia, and eight samples after the incision, over a period of 70 h. The preinduction serum CPK level of 97 +/- 32 U/L (mean +/- SD) increased gradually and significantly and reached the peak level of 542 +/- 116 U/L 34 h after incision (p <0.05). Whereas all of the CPK isoenzymes increased in terms of U/L after incision, only the MM fraction (expressed as percent of total CPK) increased, and the MB and BB fractions (expressed as percent of total CPK) decreased. The preinduction serum LDH level of 150 +/- 42 U/L (mean +/- SD) increased gradually after incision and reached the peak level of 210 +/- 32 U/L 58 h after incision (p <0.05). LDH2 as a percent of total LDH decreased significantly, but the LDH1/LDH2 ratio did not change. LDH4 and LDH5, as percents of total LDH, increased significantly. The large increases in total serum CPK and the concomitant decrease in MB percent after craniotomy may minimize and/or mask the percentage increase in the MB level following acute myocardial infarction. The perioperative serum CPK level as a marker in the diagnosis of malignant hyperthermia should be interpreted in light of the present results and in conjunction with clinical symptomatology.  相似文献   
73.
李承青  彭德民  王彩霞 《医学争鸣》2000,21(12):1439-1439
0 引言 急性乳腺炎是产后妇女的常见病 .我们采用针头挑拨治疗急性乳腺炎 32例 ,疗效显著 .1 临床资料 患者 32例 ,年龄 2 3~ 34 (平均 2 5 .3)岁 ,均为产后哺乳产妇 .其中患乳胀痛为共有症状 .伴发热 10例 ;右侧乳腺炎 14例 ,左侧乳腺炎 16例 ,双侧乳腺炎 2例 ;外上象限胀痛 6例 ,外下象限胀痛 8例 ,内上象限胀痛 7例 ,内下象限胀痛 6例 ,二象限同时胀痛 5例 .乳头均无破损 .患者取卧位 ,显露患乳 ,乳头以碘伏严密消毒后 ,术者持五号针头以指腹常规触诊患乳 ,触摸到肿胀部位后 ,沿乳腺管走行方向找到对应的乳头腺管口 ,以针尖轻轻挑拨…  相似文献   
74.
Acetabular fractures. Clinical outcome of surgical treatment   总被引:16,自引:0,他引:16  
Sixty patients with acetabular fractures were treated surgically. All fractures were a result of high energy trauma, most with significant associated injuries. Fifty-three of the patients were followed up for at least 2 years. Clinical outcome was analyzed clinically using the Harris hip score and radiographically. In 41 (77.4%) of the patients, the surgical procedure was judged successful (Harris hip score greater than 80 points). Three factors were found to be statistically significant predictors of such an outcome: patient age younger than 40 years; simple fractures based on the classification of Letournel and Judet; and absence of damage to the femoral head. Possible influential factors that were not found to be statistically significant in this population included additional injuries, immediate complications, quality of reduction, heterotopic ossification, ipsilateral femoral fracture, and sciatic nerve damage. Open reduction and internal fixation of the displaced acetabular fracture, although a demanding procedure, can result in a satisfactory clinical outcome given a consistent approach with a dedicated team.  相似文献   
75.
BACKGROUND: Cost reduction has become an important fiscal aim of many hospitals and anesthetic departments, despite its inherent limitations. Volatile anesthetic agents are some of the few drugs that are amenable to such treatment because fresh gas flow rate (FGFR) can be independent of patient volatile anesthetic agent requirement. METHODS: FGFR and drug use were recorded at the temporal midpoint of 2,031 general anesthetics during a 2-month preintervention period. Staff and residents were provided with their preintervention individual mean FGFR, their peer group mean, and educational material regarding volatile agent costs and low-flow anesthesia. FGFR and drug use were remeasured over a 2-month period (postintervention) immediately after this information (N = 2,242) and again 5 months later (delayed follow-up), for a further 2-month period (N = 2,056). RESULTS: For all cases, FGFR decreased from 2.4+/-1.1 to 1.8+/-1.0 l/min (26% reduction) after the intervention and increased to 1.9+/-1.1 l/min (5% increase of preintervention FGFR) at the time of delayed follow-up. Use of more expensive volatile agents (desflurane and sevoflurane) increased during the study period (P < 0.01). In a subgroup of 44 staff members with more than five cases in all study periods, 42 members decreased their mean FGFR after intervention. At delayed follow-up, 30 members had increased their FGFR above postintervention FGFR but below their initial FGFR. After accounting for other predictors of FGFR, the effectiveness of the intervention was significantly reduced at follow-up (28% reduction), but retained a significant effect compared to preintervention FGFR (19% reduction). CONCLUSIONS: Although individual feedback and education regarding volatile agent use was effective at reducing FGFR, effectiveness was reduced without continued feedback. Use of more expensive volatile agents was not reduced by education regarding drug cost, and actually increased.  相似文献   
76.
We retrospectively reviewed the results of open or closed reduction for developmental dysplasia of the hip (DDH) in 49 children younger than 12 months old, who had 57 hip dislocations. Group A (18 hips) developed partial or complete avascular necrosis (AVN), and group B (39 hips) did not develop AVN. Thirty-eight hips were treated by closed reduction, and 17 had open reduction. One patient with bilateral hip dislocation initially had closed reductions followed by bilateral open reduction 3 months later. With the numbers available for study, there was no significant difference in the occurrence of AVN with respect to variables such as preliminary traction, closed versus open reduction, Pavlik harness use, and age at the time of operative intervention. However, the presence of the ossific nucleus before reduction, detected either by radiographs (p < 0.001) or ultrasonography (p = 0.033) was statistically significant in predicting AVN. Only one (4%) of 25 hips with an ossific nucleus developed AVN, whereas 17 (53%) of 32 hips without an ossific nucleus before reduction developed AVN. Our results suggest that the presence of the ossific nucleus before closed or open reduction for DDH may decrease the risk of AVN.  相似文献   
77.
Rationale: We have previously shown that during the acute response to amphetamine, a stimulant that released dopamine, behavioral sensitivity to the drug undergoes dynamic changes, as evident in the altered behavioral profile expressed to the subsequent administration of a low dose of the drug. Objective: The present studies were designed to determine if these dynamic changes in sensitivity occur with amphetamine-like stimulants that act primarily by blocking dopamine uptake. Methods: Groups of animals were primed with 40 mg/kg cocaine or 30 mg/kg methylphenidate, then during the acute response, a low, locomotor-stimulant dose of amphetamine (1.5 mg/kg) was administered to probe for changes in sensitivity. Conversely, to determine whether the manifestation of the increased responsivity is idiosyncratic to amphetamine, animals were also primed with amphetamine (4 mg/kg), then probed with low doses of cocaine (10 and 20 mg/kg) or methylphenidate (10 mg/kg). Parallel microdialysis studies were performed to assess the caudate-putamen and nucleus accumbens extracellular dopamine responses. Results: Priming with the uptake blockers each resulted in a stereotypy response to the subsequent low-dose amphetamine probe. Likewise, after priming with amphetamine, the uptake blockers each induced a pronounced stereotypy response. In each case, these changes in behavioral responsivity were expressed in the absence of corresponding changes in the probe-induced regional dopamine responses. Conclusions: Dynamic changes in behavioral sensitivity during the response to acute stimulant administration are a characteristic common to both dopamine releasers and uptake blockers. These rapid changes in sensitivity may contribute to the behaviors associated with binge patterns of drug abuse. Received: 5 April 1999 / Final version: 28 May 1999  相似文献   
78.
Key predictions of the Hubble law are inconsistent with direct observations on equitable complete samples of extragalactic sources in the optical, infrared, and x-ray wave bands-e.g., the predicted dispersion in apparent magnitude is persistently greatly in excess of its observed value, precluding an explanation via hypothetical perturbations or irregularities. In contrast, the predictions of the Lundmark (homogeneous quadratic) law are consistent with the observations. The Lundmark law moreover predicts the deviations between Hubble law predictions and observation with statistical consistency, while the Hubble law provides no explanation for the close fit of the Lundmark law. The flux-redshift law F [symbol, see text] (1 + z)/z appears consistent with observations on equitable complete samples in the entire observed redshift range, when due account is taken of flux limits by an optimal statistical method. Under the theoretical assumption that space is a fixed sphere, as in the Einstein universe, this law implies the redshift-distance relation z = tan2(r/2R), where R is the radius of the spherical space. This relation coincides with the prediction of chronometric cosmology, which estimates R as 160 +/- 40 Mpc (1 parsec = 3.09 x 10(16) m) from the proper motion to redshift relation of superluminal sources. Tangential aspects, including statistical methodology, fundamental physical theory, bright cluster galaxy samples, and proposed luminosity evolution, are briefly considered.  相似文献   
79.
The number of Africans in Johannesburg presenting with duodenal ulcers has steadily increased over the past 50 years. The characteristics of 105 patients with duodenal ulcer who presented a Baragwanath Hospital were compared with those of matched and unmatched samples of patients without gastrointestinal conditions in the same hospital. Men with duodenal ulcers were found to be significantly better educated than their controls, most had been born in the town, and more of them were employed at higher, though not the highest, educational levels. These data were used to test Susser's proposition that duodenal ulcers are associated with "early urbanisation." Johannesburg blacks with duodenal ulcer did seem to fit the pattern, but the relation between stress and duodenal ulcer remains unclear.  相似文献   
80.
The neurotoxic effects of methamphetamine (METH) have been characterized primarily from the study of high-dose binge regimens in rodents. However, this drug administration paradigm does not include a potentially important feature of stimulant abuse in humans, that is, the gradual escalation of stimulant doses that frequently occurs prior to high-dose exposure. We have argued that pretreatment with escalating doses (EDs) might significantly alter the neurotoxic profile produced by a single high-dose binge. In the present study, we tested this hypothesis by pretreating rats with saline or gradually increasing doses of METH (0.1-4.0 mg/kg over 14 days), prior to an acute METH binge (4 x 6 mg/kg at 2 h intervals). These animals, whose behavior was continuously monitored throughout drug treatment, were then killed 3 days later for determination of caudate-putamen dopamine (DA) content, levels of [(3)H]WIN 35,428 binding to the DA transporter, and levels of [(3)H]dihydrotetrabenazine ([(3)H]DTBZ) binding to the vesicular monoamine transporter. ED pretreatment markedly attenuated the stereotypy response, as well as the hyperthermia and indices of sympathetic activation associated with the acute binge. In addition, ED pretreatment prevented the decline in [(3)H]WIN 35,428 binding, and significantly diminished the decrease in DA levels, but did not affect the decrease in [(3)H]DTBZ binding associated with the acute binge. We suggest that further study of the effects produced by a regimen which includes a gradual escalation of doses prior to high-dose METH binge exposure could more accurately identify the neurochemical and behavioral changes relevant to those that occur as a consequence of high-dose METH abuse in humans.  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