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   16206篇
  免费   1312篇
  国内免费   65篇
耳鼻咽喉   134篇
儿科学   452篇
妇产科学   337篇
基础医学   2236篇
口腔科学   345篇
临床医学   1528篇
内科学   3401篇
皮肤病学   186篇
神经病学   1363篇
特种医学   632篇
外科学   2583篇
综合类   223篇
一般理论   16篇
预防医学   1316篇
眼科学   740篇
药学   1059篇
中国医学   50篇
肿瘤学   982篇
  2022年   89篇
  2021年   228篇
  2020年   129篇
  2019年   231篇
  2018年   237篇
  2017年   171篇
  2016年   197篇
  2015年   253篇
  2014年   382篇
  2013年   654篇
  2012年   879篇
  2011年   969篇
  2010年   519篇
  2009年   516篇
  2008年   818篇
  2007年   922篇
  2006年   891篇
  2005年   931篇
  2004年   837篇
  2003年   863篇
  2002年   835篇
  2001年   228篇
  2000年   233篇
  1999年   211篇
  1998年   214篇
  1997年   177篇
  1996年   167篇
  1995年   150篇
  1994年   145篇
  1993年   125篇
  1992年   179篇
  1991年   159篇
  1990年   163篇
  1989年   155篇
  1988年   135篇
  1987年   157篇
  1986年   115篇
  1985年   171篇
  1984年   160篇
  1983年   153篇
  1982年   166篇
  1981年   162篇
  1980年   121篇
  1979年   114篇
  1978年   128篇
  1977年   134篇
  1975年   106篇
  1974年   98篇
  1973年   104篇
  1972年   88篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
1.
Objective: To determine serotonin system abnormalities related to major depression or previous suicidal behavior.

Methods: [11C]WAY100635, [18F]altanserin and positron emission tomography were used to compare 5-HT1A and 5-HT2A binding in MDD patients divided into eight past suicide attempters (>4yrs prior to scanning) and eight lifetime non-attempters, and both groups were compared to eight healthy volunteers.

Results: The two receptor types differed in binding pattern across brain regions from each other, but there were no differences in binding between healthy volunteers and the two depressed groups or between depressed suicide attempters and non-attempters. No effects of depression severity or lifetime aggression were observed for either receptor.

Conclusion: Limitations of this study include small sample size and absence of high lethality suicide attempts in the depressed attempter group. No trait-like binding correlations with past suicide attempt or current depression were observed. Given the heterogeneity of nonfatal suicidal behavior, a larger sample study emphasizing higher lethality suicide attempts may find the serotonin biological phenotype seen in suicide decedents.  相似文献   

2.
3.
Netlines     
  相似文献   
4.
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   
5.
There is a recognized need for the early detection of gestational diabetes, and a single blood test, if reliable, would be advantageous. Because serum albumin and total protein are glycosylated and have short life spans, we investigated the usefulness of glycosylated albumin and glycosylated protein in the detection of gestational diabetes. We studied five groups, each with 20 subjects: nonpregnant and pregnant controls, nonpregnant and pregnant insulin-dependent diabetic (IDDM) patients, and gestational diabetic patients. All patients with no history of diabetes had an oral glucose tolerance test to define their carbohydrate status. Our results showed that percent glycosylated albumin and percent glycosylated protein were significantly elevated in both groups of IDDM patients compared with the other groups. However, gestational diabetic patients had glycosylated albumin and glycosylated protein values similar to those of both control groups. Both glycosylated albumin and glycosylated protein correlated well with HbA1c determinations. Thus, glycosylated albumin and glycosylated protein may be a good index of glycemic control, but they are of little value in the diagnosis of gestational diabetes because of a lack of sensitivity: 8 and 3% for glycosylated albumin and glycosylated protein, respectively.  相似文献   
6.
7.
Ischemic injury plays an important role in chronic renal transplant failure (CRTF). Down-regulation of ecto-adenosine triphosphatase (ATPase) in combination with up-regulation of ecto-5'-nucleotidase is a hallmark of ischemic injury. We studied the expression of renal ecto-5'-nucleotidase and ecto-ATPase in experimental renal transplantation. Fisher 344-to-Lewis allografted rats were either treated with an angiotensin-converting enzyme inhibitor (ACEi) or left untreated. Lewis-to-Lewis syngrafted rats served as controls. Untreated allografted rats developed proteinuria, glomerulosclerosis, and mild intimal hyperplasia. ACEi completely prevented focal and segmental glomerulosclerosis (FGS) and proteinuria, but significantly enhanced intimal hyperplasia. Untreated allografted rats revealed marked vascular ecto-5'-nucleotidase activity, which increased with ACEi. Vascular ecto-5'-nucleotidase activity was absent in syngrafted animals. Ecto-5'-nucleotidase activity correlated well with intimal hyperplasia. Glomerular ecto-ATPase expression was significantly reduced in untreated allografted rats compared to syngrafted rats and correlated well with the extent of FGS. ACEi prevented reduction in glomerular ecto-ATPase. We found de-novo expression of ecto-5'-nucleotidase at sites of renal intimal hyperplasia. Glomerular ecto-ATPase expression was markedly reduced in allografted rats and was prevented by ACEi. These enzyme expression patterns suggest local ischemic damage in experimental CRTF.  相似文献   
8.
9.
10.
A régime for the care of far advanced cancer patients is elaborated.The following considerations in therapy are discussed: the psychologic approach; nursing care; bedsores; ulcers; odors; discharges; the peculiarities of abdominal cancer; fistulae from hollow viscera; hemorrhage; intractable pain; palliative operations.The importance of treating the exact cause of the discomfort rather than loading the patient with narcotics, is emphasized.  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