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   21639篇
  免费   1515篇
  国内免费   9篇
  2023年   112篇
  2022年   99篇
  2021年   507篇
  2020年   351篇
  2019年   471篇
  2018年   596篇
  2017年   484篇
  2016年   811篇
  2015年   1215篇
  2014年   1344篇
  2013年   1660篇
  2012年   1949篇
  2011年   1895篇
  2010年   1179篇
  2009年   1019篇
  2008年   1379篇
  2007年   1298篇
  2006年   1184篇
  2005年   1092篇
  2004年   987篇
  2003年   927篇
  2002年   752篇
  2001年   119篇
  2000年   104篇
  1999年   136篇
  1998年   116篇
  1997年   98篇
  1996年   83篇
  1995年   87篇
  1994年   90篇
  1993年   90篇
  1992年   54篇
  1991年   58篇
  1990年   62篇
  1989年   46篇
  1988年   53篇
  1987年   38篇
  1986年   44篇
  1985年   53篇
  1984年   38篇
  1983年   43篇
  1982年   32篇
  1981年   42篇
  1980年   26篇
  1979年   38篇
  1978年   31篇
  1977年   28篇
  1976年   25篇
  1975年   23篇
  1973年   18篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
21.
22.
23.
24.
25.
Molecular and Cellular Biochemistry - Glucocorticoids (GCs) regulate astrocyte function, while glutamine synthetase (GS), an enzyme highly expressed in astrocytes, is one of the most remarkable...  相似文献   
26.
The cause of sporadic amyotrophic lateral sclerosis (SALS) remains unknown. We attempted to find out if occupational exposure to toxicants plays a part in the pathogenesis of this disease. In an Australia-wide case-control study we compared the lifetime occupations of 611 SALS and 775 control individuals. Occupations were coded using country-specific as well as international classifications. The risk of SALS for each occupation was calculated with odds ratios using logistic regression. In addition, the literature was searched for possible toxicant links between our findings and previously-reported occupational associations with SALS. Male occupations in our study that required lower skills and tasks tended to have increased risks of SALS, and conversely, those occupations that required higher skills and tasks had decreased risks of SALS. Of all the occupations, only truck drivers, where exposure to diesel exhaust is common, maintained an increased risk of SALS throughout all occupational groups. Another large case-control study has also found truck drivers to be at risk of SALS, and almost two-thirds of occupations, as well as military duties, that have previously been associated with SALS have potential exposure to diesel exhaust. In conclusion, two of the largest case-control studies of SALS have now found that truck drivers have an increased risk of SALS. Since exposure to diesel exhaust is common in truck drivers, as well as in other occupations that have been linked to SALS, exposure to this toxicant may underlie some of the occupations that are associated with SALS.  相似文献   
27.
Objective: We examined predictors of weight loss with topiramate, an anticonvulsant associated with weight loss in adults. Research Methods and Procedures: In this uncontrolled, prospective clinical trial, topiramate was added to existing anticonvulsants in adults (40 to 110 kg) with partial‐onset seizures. Primary measurements were change from baseline weight after 3 months and 1 year in patients completing 1 year of topiramate treatment (N = 38). Physiological and metabolic measures were analyzed for correlation with weight loss during topiramate treatment. Results: In patients who completed 1 year of topiramate treatment, baseline weight was reduced in 82% at 3 months and in 86% at 1 year. Mean body weight was reduced 3.0 kg (3.9% of baseline) at 3 months and 5.9 kg (7.3%) at 1 year. In obese patients [body mass index (BMI) ≥ 30 kg/m2], mean weight loss was 4.2 kg (4.3%) at 3 months and 10.9 kg (11.0%) at 1 year. Weight loss was primarily caused by reduction in body fat mass. For all patients, weight loss at 3 months correlated most strongly with reduced caloric intake (p = 0.02). At 1 year, caloric intake had returned to baseline levels; weight loss correlated most strongly with higher baseline BMI (p = 0.0007). Discussion: Our results suggest that weight loss occurs in most adults treated with topiramate and is sustained for at least 1 year. Reduced caloric intake may account, in part, for weight loss during early treatment. The pattern of weight loss differs according to baseline BMI, with obese patients experiencing greater weight loss during continued therapy.  相似文献   
28.
29.
Autofluorescence spectroscopy is a promising and powerful approach for an in vivo, real time characterization of liver functional properties. In this work, preliminary results on the dependence of liver autofluorescence parameters on the nutritional status are reported, with particular attention to vitamin A and lipid accumulation in liver tissue. Normally fed and 24 h starving rats were used as animal models. Histochemical and autofluorescence analysis showed that lipids and vitamin A colocalize in the liver parenchyma. Fasting condition results in a parallel increase in both lipids and vitamin A. Autofluorescence imaging and microspectrofluorometric analysis carried out on unfixed, unstained tissue sections under 366 nm excitation, evidenced differences in both spectral shape and response to continuous irradiation between liver biopsies from fed and starving rats. As to photobleaching, in particular, fitting analysis evidenced a reduction of about 85% of the signal attributable solely to vitamin A during the first 10 s of irradiation. The tissue whole emission measured in fed and starving rat livers exhibited reductions of about 35% and 52%, respectively, that are closely related to vitamin A contents. The findings open interesting perspectives for the set up of an in situ, real time diagnostic procedure for the assessment of liver lipid accumulation, exploiting the photophysical properties of vitamin A.  相似文献   
30.
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