全文获取类型
收费全文 | 2059篇 |
免费 | 123篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 152篇 |
妇产科学 | 27篇 |
基础医学 | 193篇 |
口腔科学 | 56篇 |
临床医学 | 268篇 |
内科学 | 514篇 |
皮肤病学 | 25篇 |
神经病学 | 75篇 |
特种医学 | 473篇 |
外科学 | 149篇 |
综合类 | 30篇 |
预防医学 | 66篇 |
眼科学 | 13篇 |
药学 | 68篇 |
中国医学 | 3篇 |
肿瘤学 | 91篇 |
出版年
2021年 | 15篇 |
2020年 | 20篇 |
2019年 | 15篇 |
2018年 | 24篇 |
2017年 | 19篇 |
2016年 | 36篇 |
2015年 | 34篇 |
2014年 | 33篇 |
2013年 | 67篇 |
2012年 | 38篇 |
2011年 | 45篇 |
2010年 | 80篇 |
2009年 | 66篇 |
2008年 | 44篇 |
2007年 | 35篇 |
2006年 | 49篇 |
2005年 | 31篇 |
2004年 | 31篇 |
2003年 | 30篇 |
2002年 | 31篇 |
2001年 | 25篇 |
2000年 | 30篇 |
1999年 | 47篇 |
1998年 | 134篇 |
1997年 | 121篇 |
1996年 | 127篇 |
1995年 | 95篇 |
1994年 | 78篇 |
1993年 | 85篇 |
1992年 | 29篇 |
1991年 | 31篇 |
1990年 | 24篇 |
1989年 | 67篇 |
1988年 | 50篇 |
1987年 | 52篇 |
1986年 | 55篇 |
1985年 | 49篇 |
1984年 | 28篇 |
1983年 | 33篇 |
1982年 | 35篇 |
1981年 | 23篇 |
1980年 | 36篇 |
1979年 | 15篇 |
1978年 | 18篇 |
1977年 | 19篇 |
1976年 | 23篇 |
1975年 | 25篇 |
1942年 | 11篇 |
1941年 | 11篇 |
1940年 | 10篇 |
排序方式: 共有2204条查询结果,搜索用时 31 毫秒
1.
B Djuricic S R Olson H M Assaf T S Whittingham W D Lust L R Drewes 《Journal of cerebral blood flow and metabolism》1991,11(2):308-313
Free choline and ATP contents were measured in Mongolian gerbil hippocampal slices (tissue) and incubation media (media) during exposure to 30 min of aglycemia, high potassium, anoxia, or ischemia. Changes in choline levels reflected the degree of energy reduction, lower ATP levels being associated with high choline (4-fold increase during exposure to high potassium and anoxia, and 11-fold increase during ischemia). Media (extracellular) choline was particularly affected and increased about twofold during relatively mild energy depletion (e.g., aglycemia), but tissue choline content was less sensitive to energy reduction. A plot of choline vs. ATP levels indicated a nonlinear correlation, and the sharp increase in choline occurred when ATP values fell to about 2.5 nmol/mg of protein. Inhibition of acetylcholine sterase by 10 microM physostigmine during ischemia did not prevent an increase in choline contents but rather enhanced them, indicating that acetylcholine hydrolysis was not the source of free choline. Formation of free choline was Ca2+ independent. These findings suggest the involvement of phospholipase D and phosphatidylcholine hydrolysis in free choline formation during energy stress. The extent of choline formation may be an indicator of the degree of membranal damage, which in turn reflects damage to the metabolic machinery of the cell. 相似文献
2.
Elevated serum levels of keratan sulfate (KS) and hyaluronate (HA) in patients with osteoarthritis (OA) have been reported. We measured KS and HA in dogs to determine if there was an elevation of these serum glycosaminoglycans in a canine model of OA. A single intraarticular injection of 1 mg of chymopapain into a shoulder joint increased serum KS by tenfold, and HA by less than twofold, in 24 hours. Serum KS and HA levels were 3-5-fold higher in dogs younger than 2 months of age than in older dogs. Serum KS and HA concentrations and synovial fluid KS concentrations were unrelated to spontaneous cartilage degeneration in 1-year-old dogs. Higher KS levels in synovial fluid correlated with higher KS levels in serum (r = 0.54, P less than 0.025). The mean KS concentration in sera of older dogs (greater than 3 years old) with OA was 37% higher than that in disease-free controls, but the difference between the groups was not statistically significant. Thus, elevated levels of serum KS and HA do not appear to have clinical significance in this model of OA. 相似文献
3.
JA HYEON KU CHEOL KWAK SEUNG-JUNE OH EUNSIK LEE SANG EUN LEE JAE-SEUNG PAICK 《International journal of urology》2004,11(7):489-493
BACKGROUND: Our aims in the present study were to estimate the influences of pain and urinary symptoms on quality of life, and to determine which of these two variables has the most predictive power with respect to quality of life in young men with chronic prostatitis-like symptoms. METHODS: Chronic prostatitis-like symptoms were measured by the National Institutes of Health-Chronic Prostatitis Symptom Index. Of the 28,841 men aged 20 years who lived in the study community, 18,495 men (a response rate 64.1%) agreed to participate in the study. A total of 1057 men who complained of symptoms indicative of chronic prostatitis were included in the study. The influences of pain and urinary symptoms on quality of life were determined using logistic regression analysis. The receiver operating characteristic (ROC) curve was used to estimate the predictive ability of each of these variables with respect to quality of life. RESULTS: Results from multivariate analysis showed that both pain and urinary symptoms were associated with an increased likelihood of impaired quality of life, although pain contributed more to a reduced quality of life than urinary symptoms. Relative to men who experienced mild pain, men who experienced moderate pain had a 3.9-fold risk of poor quality of life (odds ratio [OR], 3.87; 95% confidence interval [CI], 2.86-5.23; P < 0.001) and those who experienced severe pain had a 15.7-fold risk of reduced quality of life (OR, 15.68; 95% CI, 6.59-37.35; P < 0.001). Moderate urinary symptoms were associated with a 1.4-fold risk of bother (OR, 1.41; 95% CI, 1.01-1.99; P < 0.001) and severe urinary symptoms were associated with 2.4-fold risk (OR, 2.39; 95% CI, 1.37-4.12; P < 0.001), relative to mild urinary symptoms. Comparison of the effects of pain and urinary symptoms showed that pain severity had the most predictive power for bother, quality of life, and quality-of-life impact. The areas under the ROC curves for bother, quality of life, and quality-of-life impact were 71.3%, 69.3% and 72.5%, respectively. CONCLUSION: Urinary symptoms and pain might be associated with an increased likelihood of impaired quality of life in young men with chronic prostatitis-like symptoms. In addition, our findings suggest that pain severity is the most influential variable for determining quality of life in this population. 相似文献
4.
5.
6.
7.
8.
9.
J M Lust D L Carlson R Kowles L Rollins-Smith J W Williams rd R G McKinnell 《Proceedings of the National Academy of Sciences of the United States of America》1991,88(15):6883-6887
The developmental potential of nuclei can be studied by nuclear transplantation. Although amphibian blastula nuclei and other early embryonic nuclei are totipotent, to our knowledge no nucleus from an adult cell has ever been shown to be totipotent by this procedure. Transfer of Lucké renal carcinoma nuclei into enucleated eggs results in prefeeding swimming tadpoles. Inasmuch as these tadpoles die, rescue of this pluripotential tissue was attempted by grafting fragments of triploid tumor nuclear transplant tadpoles to the tails of normal diploid Rana pipiens hosts. Grafts of tumor nuclear transplant tadpole tissue were histologically indistinguishable from grafts of normally fertilized embryos and developed normal-appearing structures such as complete eyes, well-differentiated neural tissues, kidney tubules, and gut epithelium. Moreover, histological differentiation in tumor nuclear transplant grafts was comparable to that observed in 50-day-old normal larvae. Grafting enhanced the survival of tumor nuclear transplant tissue from no more than 14 days as part of the donor tadpole to 40 days at which time the grafts were harvested as healthy tissue. Thus, both differentiation and survival of tumor nuclear transplant tissue were augmented with the grafting procedure. Cytophotometric analysis of ploidy was used to confirm the tumor origin of the donor tissue. 相似文献
10.