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   607篇
  免费   72篇
  国内免费   1篇
  680篇
  2022年   4篇
  2020年   6篇
  2019年   4篇
  2018年   4篇
  2017年   8篇
  2016年   17篇
  2015年   27篇
  2014年   27篇
  2013年   23篇
  2012年   44篇
  2011年   31篇
  2010年   13篇
  2009年   20篇
  2008年   32篇
  2007年   20篇
  2006年   13篇
  2005年   26篇
  2004年   16篇
  2003年   22篇
  2002年   26篇
  2001年   28篇
  2000年   15篇
  1999年   13篇
  1998年   9篇
  1997年   4篇
  1996年   8篇
  1995年   3篇
  1993年   4篇
  1992年   10篇
  1991年   13篇
  1990年   12篇
  1989年   8篇
  1988年   6篇
  1987年   14篇
  1986年   12篇
  1985年   6篇
  1984年   10篇
  1983年   14篇
  1982年   11篇
  1981年   7篇
  1980年   9篇
  1979年   11篇
  1978年   6篇
  1977年   9篇
  1976年   9篇
  1975年   3篇
  1974年   11篇
  1973年   7篇
  1972年   7篇
  1971年   3篇
排序方式: 共有680条查询结果,搜索用时 93 毫秒
1.
2.
The method includes sampling of gases from an equilibration chamber permanently installed in the soil, transferring the sample to laboratory and subsequent measurement by gas chromatography. The equilibration chamber allows sampling of the gas phase both above and below the groundwater level, which is a major advantage. After significant concentration changes in non-saturated soils, gases in chambers regain equilibrium with the surrounding soils within 1–2 days. In the most unfavourable equilibration situations,i.e. in mineral subsoils with stagnant groundwater and very low biological activity, 90% equilibrium is attained in about 15 days. N2, O2+Ar, CO2, CH4, N2O, H2 and Ne, are measured on a series/bypass multi-column system, followed by a thermal conductivity detector.  相似文献   
3.
The applicability of 2-bromoethyl glycosides in carbohydrate synthesis is demonstrated by the synthesis of glycosides of alpha-L-Fuc-(1----2)-D-Gal and beta-D-Gal-(1----4)-D-GlcNAc. The bromoethyl aglycon was transformed into the methoxycarbonylethylthioethyl spacer, which allowed coupling of the sugars to proteins (BSA and KLH).  相似文献   
4.
The effect of transport stress on the plasma levels of catecholamines, Cortisol, and corticosteroid-binding globulin were studied in 6 gilts. To assess the effect on immune status, white blood cells were also counted and the cell-mediated immunity was estimated. The adrenaline level increased significantly during transport, from a basal mean level of 0.03 ng/ml to a plateau level of 0.11 to 0.12 ng/ml. The noradrenaline level fluctuated, but not constantly, during transport. The mean plasma Cortisol level before loading was approximately 40 nmol/1 and rose immediately after the start of transport to 70 nmol/1 (p< 0.05) and to 87 nmol/1 (p< 0.01) within 10 and 30 min, respectively. After unloading the Cortisol level rapidly decreased and a minimum level was seen 4 h after the transport, whereafter the diurnal rhythm was resumed. The plasma corticosteroid-binding globulin level increased nonsignificantly during the day of transport, from 25 nmol/1 to a level of 34 nmol/1, and it continued to increase until a plateau level was reached on the second day after transportation. The total white blood cell number increased significantly (from 13.7 to 15.5 × 109 cells/1), the number of lymphocytes decreased significantly (from 8.4 to 7.0 × 109 cells/1), and the number of polymorphonuclear neutrophils increased significantly (from 4.3 to 7.2 × 109 cells/1) during transport. No significant variation in the proliferation response was seen in the whole blood cell cultures. The main results were the significant signs of simultaneous activity of both the adrenal cortex and the adrenal medulla during transport.  相似文献   
5.
Ventricular aneurysm is usually a complication of acute transmural myocardial infarction. The development of cardiac aneurysm represents a process of continued thinning and fibrosis of the necrotic tissue of the ventricular wall. Survival allows the development of a solid fibrous scar which of itself does not affect global ventricular function substantially. Hence, ventricular aneurysms can be present for up to 18 years without production of serious symptoms. The cases were reviewed of 45 patients in whom aneurysmectomy and myocardial revascularization were carried out. Surgical mortality was low (6.6 percent, 30 days); survival one year after operation was 76 percent, but at three years had fallen to 47 percent. Cause of late death was dominantly cardiac. In 19 patients post-operative study was done; although graft patency was observed in 98 percent, substantive improvement in ventricular performance was seen in a minority of patients. The outcome in patients with ventricular aneurysm is primarily related to the status of the residual myocardium and to the status of the vessels which supply it. The mechanism of clinical improvement after aneurysmectomy has not been clarified. However, the long-term results appear to be similar to those in patients with extensive myocardial infarction.  相似文献   
6.
7.
8.
Phagocytosis by neutrophils, macrophages, and other professional phagocytes requires rapid remodeling of actin. Early phagosomes are surrounded by a rim of F-actin that is disassembled during phagosomoal maturation. Breakdown of periphagosomal F-actin and phagolysosome fusion are calcium dependent processes in neutrophils interacting with serum-opsonized prey, but appears to be calcium independent in macrophages interacting with serum- or IgG-opsonized prey. In the present study, we found that calcium was necessary for phagocytosis, breakdown of periphagosomal F-actin, and phagosomal maturation in J774 macrophages interacting with unopsonized prey. We also observed that lipophosphoglycan (LPG) from Leishmania donovani promastigotes required calcium to exert its inhibitory effect on macrophage phagocytosis and periphagosomal F-actin breakdown. We conclude that calcium is essential for phagocytosis, depolymerization of periphagosomal F-actin, and phagosomal maturation in J774 macrophages interacting with unopsonized prey, as well as for proper functioning of LPG.  相似文献   
9.
10.

Introduction  

Co-morbidity and mortality due to cardiovascular disease (CVD) are increased in patients with rheumatoid arthritis (RA). Most published studies in this field are retrospective or cross sectional. We investigated the presence of traditional and disease related risk factors for CVD at the onset of RA and during the first five years following diagnosis. We also evaluated their potential for predicting a new cardiovascular event (CVE) during the five-year follow-up period and the modulatory effect of pharmacological treatment.  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