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   83766篇
  免费   5993篇
  国内免费   217篇
耳鼻咽喉   1058篇
儿科学   2475篇
妇产科学   2175篇
基础医学   12801篇
口腔科学   1933篇
临床医学   9508篇
内科学   16229篇
皮肤病学   1162篇
神经病学   7900篇
特种医学   2973篇
外国民族医学   45篇
外科学   9860篇
综合类   735篇
一般理论   168篇
预防医学   8045篇
眼科学   1913篇
药学   5613篇
中国医学   173篇
肿瘤学   5210篇
  2022年   599篇
  2021年   1321篇
  2020年   856篇
  2019年   1270篇
  2018年   1525篇
  2017年   1087篇
  2016年   1276篇
  2015年   1529篇
  2014年   1917篇
  2013年   3325篇
  2012年   4379篇
  2011年   4524篇
  2010年   3029篇
  2009年   2551篇
  2008年   4095篇
  2007年   4450篇
  2006年   4395篇
  2005年   4239篇
  2004年   4241篇
  2003年   3883篇
  2002年   3909篇
  2001年   2335篇
  2000年   2349篇
  1999年   2176篇
  1998年   1147篇
  1997年   951篇
  1996年   831篇
  1995年   828篇
  1994年   736篇
  1993年   753篇
  1992年   1552篇
  1991年   1506篇
  1990年   1431篇
  1989年   1407篇
  1988年   1176篇
  1987年   1180篇
  1986年   1123篇
  1985年   1035篇
  1984年   792篇
  1983年   752篇
  1982年   571篇
  1981年   563篇
  1980年   486篇
  1979年   690篇
  1978年   437篇
  1977年   417篇
  1975年   422篇
  1974年   455篇
  1973年   386篇
  1972年   364篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
51.
52.
Routine clinical chemical variables and parameters of the vitamin, iron and zinc status were measured in 20 female patients with anorexia nervosa (AN) and in 10 lean and 10 normal weight, healthy, female control subjects. Patients with AN had higher activities of L-gamma-glutamyl transferase (gamma-GT) and glutamate pyruvate transaminase (SGPT) and a higher concentration of prealbumin in serum and lower leucocyte and lymphocyte counts in blood. For the other routine clinical chemical parameters no significant differences between the groups were observed. AN patients had higher serum vitamin B12 and retinol levels. No significant differences were found for the status parameters of thiamin, vitamin B6, vitamin C, folate, vitamin E and vitamin D. Contradictory results were obtained for the riboflavin status: AN patients had a lower level of flavin adenine dinucleotide (FAD) in blood and a lower stimulation ratio of the glutathione reductase activity in erythrocytes (alpha-EGR). Patients with AN had higher serum ferritin concentration and lower total iron binding capacity (TIBC). However, haemoglobin (Hb), haematocrit (Ht) and iron saturation were not significantly different. No significant difference was found in the concentration of zinc in plasma. In spite of the poor intake of nutrients and energy, the results obtained did not indicate an inadequate status of vitamins, iron and zinc in patients with AN.  相似文献   
53.
54.
A new experimental model is described which can be used as an alternative to study the effects of subarachnoid hemorrhage (SAH) in rats. Vasospasm of the basilar artery is induced photochemically after transpalatal illumination of intracisternally injected rose bengal in two different rat strains. Singlet oxygen, generated in the subarachnoid space, elicits vasospasm which has been demonstrated angiographically at 90 min and 24 h after photosensitisation. Sprague Dawley rats responded better than Wistar rats. Dilution of rose bengal in water was more vasospastic than dilution of rose bengal in artificial CSF. Since the action of singlet oxygen is similar to that of free radicals, this experiment gives an argument for the hypothesis that free radicals play a leading role in the pathogenesis of cerebral vasospasm after subarachnoid hemorrhage.  相似文献   
55.
56.
In order to draw attention to this rather rare condition affecting all age groups, 4 cases of fibroepithelial polyps of the ureter are reported. Conservative surgery is mandatory after adequate preoperative work-up. The pathological findings, incidence and diagnostic and therapeutic modalities are discussed and some etiological factors proposed.  相似文献   
57.
The effects of nonprotein energy source (ie, glucose only vs glucose and lipid) on nitrogen retention and total-body protein turnover were studied in 20 parenterally fed newborn infants. All infants received approximately 3 g amino acids and 80-90 kcal.kg body wt.d. Total-body protein synthesis was estimated by using three constant-infusion, end-product methods: enrichment of urinary urea and ammonia in response to a [15N]glycine label and exhaled carbon dioxide enrichment in response to a [1-13C]leucine label. No differences were seen in nitrogen retention between the two energy sources. The estimate of total-body protein turnover obtained from the 13C label was similar to that obtained with the [15N]urea label. No differences in turnover rates were observed between the two diet groups. Use of the glucose-plus-lipid fuel system enhanced energy storage and the reutilization of amino acid for protein synthesis.  相似文献   
58.
Although the revision rates for modern knee prostheses have decreased drastically, the total number of revisions a year is increasing because many more primary knee replacements are being done. At the time of revision, bone loss is common, which compromises prosthetic stability. To improve stability, intramedullary stems are often used. The aim of this study was to estimate the effects of a stem, its diameter and the interface bonding conditions on patterns of the bone remodeling in the distal femur.

We created finite element models of the distal half of a femur in which 4 types of knee prostheses were placed. The bone remodeling process was simulated using a strain-adaptive bone remodeling theory. The amount of such remodeling was determined by calculating the changes in bone mineral density in 9 regions of interest from simulated DEXA scans.

The computer simulation model showed that revision prostheses tend to cause more bone resorption than primary ones, especially in the most distal regions. Predicted long-term bone loss due to a revision prosthesis with a thin stem equalled that around a prosthesis with an intercondylar box. However, strong regional differences were found- the stemmed prostheses having more bone loss in the most distal areas and some bone gain in the more proximal ones. A prosthesis with a thick stem led to an increase in bone loss. When the prosthesis-cement interface was bonded, more bone loss was predicted than with an unbonded interface. These results suggest that a stem which increases stability initially may reduce stability in the long term. This is due to an increase in stress shielding and bone resorption.  相似文献   
59.
Evidence indicates that endogenous opioid peptides and glucocorticoids participate in the control of cardiovascular regulation during hemorrhagic shock. In the present study, we investigated a possible interaction between brain opioid peptides and adrenal corticosteroids regarding the control of arterial pressure during hemorrhage. The bleeding volumes required to lower arterial pressure to 80, 60 and 40 mmHg were studied in anesthetized sham-operated (SHAM) and adrenalectomized (ADX) rats. I.c.v. administration of 10 micrograms of naloxone resulted in a significant increase in the bleeding volume required to lower arterial pressure from 60 to 40 mmHg in SHAM animals, whereas no effect of naloxone was observed in ADX animals. Replacement therapy with a 100% corticosterone pellet (100 mg, s.c.), but not with a 12.5% corticosterone pellet (12.5 mg corticosterone and 87.5 mg cholesterol, s.c.), resulted in an effect of naloxone on the bleeding volume in ADX animals. The effect of replacement therapy could be inhibited by i.c.v. pretreatment with the synthetic glucocorticoid receptor antagonist, RU38486 (100 ng). These data suggest that (1) opioid mechanisms are involved in the regulation of blood pressure during hemorrhage, and (2) occupancy of glucocorticoid receptors is required for naloxone to exert its hemodynamic effect during hemorrhagic hypotension in ADX rats.  相似文献   
60.
1. Twenty-two patients hospitalized for treatment of depression were treated under conditions simulating those of home treatment. 2. Full doses of nortriptyline, from 100 to 150 mg/day, were started after baseline observations were made. 3. Two patients were dropped from the study, one for orthostatic hypotension, one for an aberrant response to nortriptyline. Two additional patients developed orthostasis which was easily managed. Otherwise no unusual side effects were noted. 4. After six days of treatment, 9 of 20 patients showed significant improvement with an overall reduction in scores on the Hamilton Depression Scale of 49% for the entire group. 5. Using the weight-adjusted dosage schedule, 18 of the 21 patients attained plasma concentrations of nortriptyline within the presumed therapeutic range; however, no clear relationship could be established between plasma concentrations and clinical response. 6. With proper selection of patients, it should be possible to treat at home some patients who currently are considered to require hospitalization.  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