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   34544篇
  免费   1846篇
  国内免费   185篇
耳鼻咽喉   344篇
儿科学   468篇
妇产科学   370篇
基础医学   4562篇
口腔科学   1029篇
临床医学   2211篇
内科学   8404篇
皮肤病学   858篇
神经病学   2592篇
特种医学   1364篇
外科学   5976篇
综合类   165篇
一般理论   1篇
预防医学   1081篇
眼科学   662篇
药学   2578篇
中国医学   46篇
肿瘤学   3864篇
  2023年   180篇
  2022年   372篇
  2021年   642篇
  2020年   364篇
  2019年   480篇
  2018年   625篇
  2017年   535篇
  2016年   589篇
  2015年   632篇
  2014年   801篇
  2013年   998篇
  2012年   1505篇
  2011年   1645篇
  2010年   958篇
  2009年   871篇
  2008年   1457篇
  2007年   1461篇
  2006年   1521篇
  2005年   1608篇
  2004年   1475篇
  2003年   1513篇
  2002年   1399篇
  2001年   1313篇
  2000年   1358篇
  1999年   1226篇
  1998年   446篇
  1997年   358篇
  1996年   333篇
  1995年   298篇
  1994年   264篇
  1993年   260篇
  1992年   829篇
  1991年   740篇
  1990年   740篇
  1989年   713篇
  1988年   715篇
  1987年   629篇
  1986年   622篇
  1985年   614篇
  1984年   412篇
  1983年   329篇
  1982年   164篇
  1979年   323篇
  1978年   205篇
  1977年   154篇
  1975年   150篇
  1974年   220篇
  1973年   151篇
  1972年   168篇
  1971年   149篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
We have shown previously that connexin43 in the adult rat central nervous system (CNS) is predominantly localized at astrocytic gap junctions. Here we document immunohistochemically the emergence of connexin43-immunoreactive (connexin43-IR) structures and the regional patterns of connexin43 expression during postnatal maturation of the rat brain. On Western blots, connexin43 was detected in brain samples at postnatal day (P) 5, the earliest age studied. Immunohistochemically, most brain regions displayed a characteristic sequence of transient immunoreactive profiles that ultimately gave rise to the uneven distribution of the protein seen in adults. Generally, brains at P1-P5 exhibited long, fibrous connexin43-IR elements which were identified as radial glial cells. This fibrous immunostaining was considerably diminished at P5 and was replaced by short immunoreactive processes which predominated up to P10. These processes had a stellate appearance, emanated from partially stained astrocytic cell bodies and were heterogeneously distributed throughout the developing brain. By P15, there occurred only punctate immunolabelling similar to that seen in adult brain. Some brain regions including the amygdaloid complex, septohypothalamic nucleus, preoptic hypothalamus, zona incerta, ependyma and subfornical organ were exceptional in that they displayed adult immunostaining patterns at early postnatal ages suggesting a precocious maturation of gap junctions in these areas. We conclude that the highly heterogeneous distribution of connexin43-immunoreactivity among defined nuclear structures in adult brain does not reflect an antecedent requirement for connexin43 in early brain morphogenesis, but rather is related to the development of neuronal activity, the establishment of functional circuitry and the contribution of astrocytic gap junctions to glial metabolic coupling and potassium spatial buffering in the mature CNS.  相似文献   
102.
103.
During a 12-month period ending on November 30, 1988, data were collected on 2468 pediatric patients with wheezing who visited a pediatric ED. Cohort characteristics included: sex (64% male, 36% female), history of prematurity (12%), evidence of concurrent infection (82%), taking theophylline (35%), taking beta adrenergics (60%), taking cromolyn (6%), and taking corticosteroids (4%). The hospitalization rate was 10.5%. Seasonal variations, weather, air quality, and infections appeared to have significant effects on the daily variation of wheezing exacerbations. Initial oxygen saturation (OSAT) correlated with disease severity as measured by hospitalization risk and the number of bronchodilator treatments required in the ED. A suggestion for categorizing the treatment of asthma based on past history is proposed. Using this system in conjunction with pulse oximetry, wheezing severity and appropriate therapy can be more objectively determined.  相似文献   
104.
Recently, plasma fructosamine concentration has been used as an indication of mean plasma glucose level preceding at last 1 to 2 weeks. In the present study, to characterize the clinical significance and problems of plasma fructosamine concentration in aged subjects (greater than or equal to 65 yrs), we determined plasma fructosamine concentration as well as serum albumin, total protein, HbA1, AbA1c and fasting plasma glucose concentrations in 81 (less than 65 yrs) non-diabetic subjects (group A), 161 aged (greater than or equal to 65 yrs) non-diabetic subjects and 26 aged diabetics (group D). Aged non-diabetic subjects were further classified into 75 subjects with good ADL (group B) and 86 with poor ADL (group C). The normal limit of plasma fructosamine concentration (mean +/- 2SD) in group A was 24% higher (3.1 mmol/l) than that in group B (2.5 mmol/l) but the plasma fructosamine/serum albumin ratio (F/ALB) was similar in these two groups. Plasma fructosamine correlated negatively (p less than 0.01) with age. This aging effect was explained by the reduced serum albumin in aged subjects. However, in group C, reduced plasma albumin was not associated with reduced plasma fructosamine. Plasma fructosamine corrected by albumin (F/ALB) is a useful parameter of blood glucose control in aged subjects. In aged subjects with poor ADL, HbA1, HbA1c and plasma glucose should be determined with fructosamine.  相似文献   
105.
p = 0.0007) and tumor necrosis (TN) (HMC: p = 0.0050). Univariate analysis showed that AMC or HMC was a statistically significant predictor of overall survival in all patients ( p = 0.0086 and p = 0.0307, respectively). Multivariate analysis showed that AMC was an independent predictor of node status when we fitted a model with node status, BVI, and either AMC or HMC; but HMC was not independent. However, when we fitted a model including all 11 of the other indicators and AMC or HMC, the node status, HG, and LI were independent predictors, but AMC and HMC were not. Although AMC was a better method than HMC for evaluating angiogenesis, we cannot confirm angiogenesis as a significant independent prognostic factor associated with long-term survival in Japanese breast cancer patients.  相似文献   
106.
107.
We reviewed the radiographs of 25 hips of 20 patients who had received revisions of the acetabular components of total hip replacement supplemented by allograft for bone defects. Bone defects in 20 hips (80%) were classified into type D (cranio-central defect) according to Itoman's classification. In eight, sockets were installed directly on the allografts (group A). A metallic supporting device was used for reinforcing the grafts in 17 hips (group B). The position of the acetabular socket was measured on a radiograph, taken immediately after revision surgery and again at the latest follow-up. Using a MEM template, cranial and central migrations were determined. Mean cranial migration in hips of group A was 3.6 mm. Group B was 0.2 mm. Maintenance of thickness of the allografts was 60.6% in the cranial region and 75% in the central in group A. In the hips of group B, however, almost 100% of the initial thickness was maintained cranially and centrally. Allograft reconstruction of acetabular bone defect in revision total hip replacement is a beneficial procedure. The remaining pelvic bone is usually in poor condition, therefore, it is necessary to ensure primary fixation by the metallic supporting device.  相似文献   
108.
A case of 'low tension glaucoma' with primary empty sella is reported. The visual field defect and optic disc change were characteristic of glaucoma. The intraocular pressure was within normal limits. X-ray examination and the metrizamide-CF procedures revealed a primary empty sella. The coexistence of 'low tension glaucoma' and empty sella is discussed.  相似文献   
109.
110.
Thirty-one prolonged coma patients, who continued in a comatose state for at least 2 months, were classified electrophysiologically employing EEG, a compressed spectral array of continuous EEG frequency analysis, BSR, SEP and SSEP. The prognoses of long-term follow-up (at least 8 months) in these patients were compared with the results of such electrophysiological analysis and with the neurological gradings of the prolonged coma patients. In the continuous EEG frequency analysis, 22 cases were classified as having a changeable spectrogram, nine cases as having a slow monotonous spectrogram, and no cases as having a borderline spectrogram. We also classified the changeable spectrograms into the following three patterns: no desynchronization, slight desynchronization, and desynchronization. The nine cases with a slow monotonous spectrogram revealed severe damage of the brain stem and cerebral function with multimodality evoked potentials, and most of these cases could not survive without assisted respiration. The 22 cases with a changeable spectrogram had mild damage of the brain stem and cerebral function with multimodality evoked potentials, and these cases were identical with a persistent vegetative state. Three of the cases showed a changeable spectrogram that revealed a desynchronization pattern, normal BSR and normal N20 of SEP and SSEP, recovered spontaneously from the persistent vegetative state within 6 months after electrophysiological evaluation. We conclude that not only a neurological but also an electrophysiological classification is necessary to evaluate the brain function and prognosis of prolonged coma.  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