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   23148篇
  免费   2111篇
  国内免费   42篇
耳鼻咽喉   219篇
儿科学   626篇
妇产科学   582篇
基础医学   2713篇
口腔科学   416篇
临床医学   2363篇
内科学   4769篇
皮肤病学   393篇
神经病学   2173篇
特种医学   875篇
外国民族医学   3篇
外科学   3432篇
综合类   522篇
一般理论   43篇
预防医学   2494篇
眼科学   310篇
药学   1549篇
中国医学   30篇
肿瘤学   1789篇
  2021年   351篇
  2020年   202篇
  2019年   397篇
  2018年   499篇
  2017年   344篇
  2016年   318篇
  2015年   408篇
  2014年   575篇
  2013年   846篇
  2012年   1159篇
  2011年   1188篇
  2010年   751篇
  2009年   670篇
  2008年   1108篇
  2007年   1206篇
  2006年   1198篇
  2005年   1170篇
  2004年   1071篇
  2003年   996篇
  2002年   918篇
  2001年   603篇
  2000年   631篇
  1999年   575篇
  1998年   312篇
  1997年   230篇
  1996年   234篇
  1995年   253篇
  1994年   192篇
  1993年   184篇
  1992年   426篇
  1991年   410篇
  1990年   359篇
  1989年   384篇
  1988年   344篇
  1987年   335篇
  1986年   302篇
  1985年   314篇
  1984年   261篇
  1983年   219篇
  1982年   174篇
  1981年   154篇
  1979年   243篇
  1978年   179篇
  1977年   151篇
  1975年   147篇
  1974年   150篇
  1973年   190篇
  1972年   186篇
  1971年   158篇
  1969年   148篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
81.
82.
83.
A 36-year-old woman with newly diagnosed acne rosacea is presented. Her skin changes were noticeable only under closest scrutiny, but she quit her job, became despondent about her acne, and developed suicidal ideation. The diagnosis and treatment of this patient allow a broader discussion of the somatically focused patient whose ideation reaches delusional intensity.  相似文献   
84.
Daily administration of an escalating dose of tumour necrosis factor-alpha (TNF-alpha) to female NMRI mice caused a progressive loss of body weight representing 12% of the original weight over a 6-day period. Weight loss was associated with a decreased food intake and pair-fed controls exhibited a weight loss of similar magnitude to that caused by TNF-alpha. However, weight loss in animals bearing a murine adenocarcinoma (MAC16) occurred without a change in energy intake and thus differed from that produced by TNF-alpha. Anti-TNF-alpha monoclonal antibodies at levels capable of protecting mice against lethal endotoxaemia were ineffective in reversing weight loss in animals bearing the MAC16 tumour and had no effect on the increase in tumour volume. Circulating levels of interleukin-6 were not elevated in animals bearing the MAC16 tumour and with a weight loss between 1.8 and 5.4 g. These results suggest that these cytokines are not involved in the cachexia produced by this murine tumour.  相似文献   
85.
A basic theory of nonspecific toxicity has been developed using bioconcentration as a basis and applying kinetic relationships developed in previous work. This approach has involved calculation of the critical volume fraction and critical concentration in lipid tissue of fish for a variety of organic compounds at the lethal level. Corrections to previous data sets for time period of exposure and inclusion of biodegradable compounds did not make a significant improvement in the values obtained. A new data base with compounds containing a wide range of Kow values gave results for critical volume and concentration similar to previous work. The influence of experimental procedures and methods for data development are considered. The basic theoretical derivation developed was found to provide a basis for predicting the approximate nonspecific toxicity of nondegradable lipophilic organic compounds at different exposure time periods. This requires a knowledge of the Kow value and the clearance rate constant (k2) which can be calculated from the Kow value.  相似文献   
86.
An examination of the urinary excretions of 101 normal subjects indicated that the major genetic influence on calcium excretion is a codominant pair of alleles giving rise to three phenotypes, low, intermediate and high (hypercalciuric) excretors. This inference was based on variance, Hardy-Weinberg and segregation analyses. Similar independent gene pairs also appear to influence oxalate and citrate excretion, A 3-locus Hardy-einberg table using estimates of gene frequencies derived from the study of normals suggests that only 3 or 4 leading genes are involved in oxalate stone disease. Strong candidate genes identified from molecular and physiological studies cannot be proposed at present, but it is assumed that they influence the transport of these ions in either the intestine, kidney or both organs. The identification of the genes involved should be facilitated by the reduction of dietary influences on urinary excretions through the use of formula diets.  相似文献   
87.
The anterior cruciate ligament has a complex fiber anatomy and is not considered to be a uniform structure. Current anterior cruciate ligament reconstructions succeed in stabilizing the knee, but they neither fully restore normal knee kinematics nor reproduce normal ligament, function. To improve the outcome of the reconstruction, it may be necessary to reproduce the complex function of the intact anterior cruciate ligament in the replacement graft. We examined the in situ forces in nine human anterior cruciate ligaments as well as the force distribution between the anteromedial and posterolateral bundles of the ligament in response to applied anterioi tibial loads ranging from 22 to 110 N at knee flexion angles of 0–90°. The analysis was performed using a robotic manipulator in conjunction with a universal force-moment sensor. The in situ forces were determined with no device attached to the ligament, while the knee was permitted to move freely in response to the applied loads. We found that the in situ forces in the anterior cruciate ligament ranged from 12.8 ± 7.3 N under 22 N of anterior tibial load applied at 90° of knee flexion to 110.6 ± 14.8 N under 110 N of applied load at 15° of flexion. The magnitude of the in situ force in the posterolateral bundle was larger than that in the anteromedial bundle at knee flexion angles between 0 and 45°, reaching a maximum of 75.2 ± 18.3 N at 15° of knee flexion under an anterior tibial load of 110 N. The magnitude of the in situ force in the posterolateral bundle was significantly affected by knee flexion angle and anterior tibial load in a fashion remarkably similar to that seen in the anterior cruciate ligament. The magnitude of the in situ force in the anteromedial bundle, in contrast, remained relatively constant, not changing with flexion angle. Significant differences in the direction of the in situ force between the anteromedial bundle and the posterolateral bundle were found only at flexion angles of 0 and 60° and only under applied anterior tibial loads greater than 66 N. We have demonstrated the nonuniformity of the anterior cruciate ligament under unconstrained anterior tibial loads. Our data further suggest that in order for the anterior cruciate ligament replacement graft to reproduce the in situ forces of the normal anterior cruciate ligament, reconstruction techniques should take into account the role of the posterolateral bundle in addition to that of the anteromedial bundle.  相似文献   
88.
In 195 elderly head-injured patients, Glasgow Coma Scale (GCS) scores (admission and 72 hours) and intracranial pressure (ICP) 0-12 days after injury were compared to 6 month Glasgow Outcome Scores. All patients remaining comatose at least 72 hours after injury died within 6 months. The mortality rate among patients with ICP greater than 20 mm Hg was higher both at 72 hours and at 6 months after injury. The 6 month mortality rate was 75% overall and 90% among patients with elevated ICP. This increased mortality in elderly patients with initially elevated ICP indicates that nurses and other health professionals should consider ICP as well as level of consciousness when counseling patients and families regarding the likely outcome after major head injuries.  相似文献   
89.
OBJECTIVE: Lp(a) lipoprotein is a distinct lipoprotein particle that recently has been found to be associated with cardiovascular disease. A study was conducted to assess the influence of cardiovascular disease risk factors on levels of Lp(a) and to evaluate the effects of age, exercise, and estrogen on these levels. STUDY DESIGN: Two studies, a cross-sectional study of older men (n = 105) and women (n = 75) (mean age 76 years) and a prospective study of younger postmenopausal women (mean age 48 years), were carried out. Lp(a) and other lipoproteins were measured in the two studies and differences were sought by statistical analysis. RESULTS: In the cross-sectional study, serum Lp(a) was similar in men and women and was not influenced by age. Lp(a) levels in men and women were higher when there was more than one cardiovascular disease risk factor present (p less than 0.028). We could not demonstrate such a relationship with other lipid and lipoprotein measurements. In the prospective study exercise alone had no influence on Lp(a) levels. Oral estrogen decreased Lp(a) levels marginally (p = 0.08). The decrease in Lp(a) with oral estrogen was associated with increases in triglycerides (p less than 0.01) and very-low-density lipoprotein (p less than 0.06). CONCLUSIONS: These data confirm that elevated Lp(a) levels are an independent risk factor for cardiovascular disease. Lp(a) levels are primarily influenced by genetic factors and it appears estrogen may have a minor influence on its hepatic synthesis.  相似文献   
90.
OBJECTIVE: Forty-six cases of subungual melanoma were reviewed to identify significant clinicopathologic prognostic factors, determine the role of DNA content analysis in the biologic assessment of these tumors, and evaluate the effectiveness of amputation level, lymph node dissection (LND), and regional limb perfusion on the survival of these patients. BACKGROUND: Subungual melanoma is a unique and rare subtype of melanoma, constituting only 1% to 3% of cases. Thus, little is known about prognostic factors and optimal management of patients with this disease. Moreover, the appropriate level of amputation and LND and limb perfusion in the management of subungual melanoma remain controversial. METHODS: Forty-six patients underwent amputation alone or in combination with LND and/or regional limb perfusion for primary subungual melanoma. The effects of these treatment modalities and the prognostic significance of patient and tumor-related variables, including DNA flow cytometric data, on overall survival were assessed. RESULTS: Univariate statistical analysis identified six factors that significantly affected patient survival. They were stage at diagnosis (p = 0.0001), percentage of aneuploid cells (p = 0.01), presence of ulceration (p = 0.02) or bone invasion (p = 0.02), thickness of the primary lesion (p = 0.03), and percentage of cells in S-phase (p = 0.03). Multivariate analyses identified tumor stage and S-phase fraction as independent prognostic factors in these patients. Survival did not differ among patients who received amputation alone or those who underwent amputation in combination with LND or perfusion (p = 0.90); however, the use of limb perfusion reduced the incidence of locally recurrent disease. The level of amputation did not affect patient survival (p = 0.74) or the incidence of local recurrence. CONCLUSIONS: The study identified several significant prognostic factors, including DNA flow cytometric parameters, in patients with subungual melanoma. In addition, it showed that conservative amputation of the affected digit at the level of the proximal interphalangeal or metacarpophalangeal/metatarsophalangeal joint appears to be safe, provided that clear margins are obtained. Although isolated limb perfusion may reduce the incidence of local recurrence, LND, or limb perfusion in the routine management of subungual melanoma remains controversial.  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