全文获取类型
收费全文 | 495651篇 |
免费 | 51792篇 |
国内免费 | 171篇 |
出版年
2018年 | 5882篇 |
2017年 | 5446篇 |
2016年 | 7645篇 |
2015年 | 9989篇 |
2014年 | 11335篇 |
2013年 | 15467篇 |
2012年 | 17716篇 |
2011年 | 17544篇 |
2010年 | 11890篇 |
2009年 | 10508篇 |
2008年 | 15544篇 |
2007年 | 15840篇 |
2006年 | 15082篇 |
2005年 | 14008篇 |
2004年 | 14023篇 |
2003年 | 13031篇 |
2002年 | 12646篇 |
2001年 | 18966篇 |
2000年 | 18875篇 |
1999年 | 15032篇 |
1998年 | 5543篇 |
1997年 | 5665篇 |
1996年 | 5338篇 |
1995年 | 5011篇 |
1994年 | 4845篇 |
1993年 | 4841篇 |
1992年 | 12314篇 |
1991年 | 12207篇 |
1990年 | 11940篇 |
1989年 | 11622篇 |
1988年 | 11065篇 |
1987年 | 10664篇 |
1986年 | 9918篇 |
1985年 | 9854篇 |
1984年 | 8270篇 |
1983年 | 7168篇 |
1982年 | 5560篇 |
1981年 | 4982篇 |
1979年 | 7967篇 |
1978年 | 6284篇 |
1977年 | 5823篇 |
1976年 | 5577篇 |
1975年 | 6091篇 |
1974年 | 6836篇 |
1973年 | 6675篇 |
1972年 | 6234篇 |
1971年 | 5639篇 |
1970年 | 5089篇 |
1969年 | 5077篇 |
1968年 | 4903篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
From six to 89 months after surgery 82 patients who had been treated by radical surgery (118 excisions) for intractable hidradenitis suppurativa were reviewed. Local recurrence rates varied greatly with the disease site, being low after axillary (3%) and perianal surgery (0%) and high after inguinoperineal (37%) and submammary (50%) excision. Recurrence results from inadequate excision or an unusually wide distribution of apocrine glands, but physical factors such as obesity, local pressure, and skin maceration played a part in a few patients. Recurrence due to inadequate surgery tended to be the most troublesome. At follow up 75 (91%) of the patients were pleased with the results of their operation. A quarter of the patients developed disease at a new anatomical site after operation. Radical surgery gives good symptomatic control of severe hidradenitis suppurativa of the axilla, inguinoperineal, and perianal regions but is less satisfactory for submammary disease. 相似文献
942.
Stability of o-phthalaldehyde-derived isoindoles 总被引:1,自引:0,他引:1
The degradation of 1-alkylthio-2-alkylisoindoles, generated in situ by reaction of o-phthalaldehyde with primary alkylamines in the presence of selected thiols, was studied under conditions typical of those used in precolumn derivatization applications. In all cases, loss of isoindole followed pseudo first order kinetics and was strongly accelerated by excess o-phthalaldehyde in the reaction mixture. Reactivity toward o-phthalaldehyde was found to be influenced by a number of experimental parameters including thiol structure, thiol concentration, amine structure, solvent composition, and pH. In the absence of excess o-phthalaldehyde, the stability of all derivatives examined was excellent. These results provide a basis for optimization of reaction conditions for maximum derivative stability. 相似文献
943.
944.
Ovarian cancer G protein-coupled receptor 1 (OGR1) is a proton-sensing molecule that can detect decreases in extracellular pH that occur during inflammation. Although OGR1 has been shown to have pro-inflammatory functions in various diseases, its role in autoimmunity has not been examined. We therefore sought to determine whether OGR1 has a role in the development of T cell autoimmunity by contrasting the development of experimental autoimmune encephalomyelitis between wild type and OGR1-knockout mice. OGR1-knockout mice showed a drastically attenuated clinical course of disease that was associated with a profound reduction in the expansion of myelin oligodendrocyte glycoprotein 35-55-reactive T helper 1 (Th1) and Th17 cells in the periphery and a reduced accumulation of Th1 and Th17 effectors in the central nervous system. We determined that these impaired T cell responses in OGR1-knockout mice associated with a reduced frequency and number of dendritic cells in draining lymph nodes during EAE and a higher production of nitric oxide by macrophages. Our studies suggest that OGR1 plays a key role in regulating T cell responses during autoimmunity. 相似文献
945.
Six peripheral blood lymphoid fractions (total lymphocytes, non-T, T, Tar (autologous rosette-forming T cells/precursor), T mu (helper), and T gamma (suppressor) lymphocytes) isolated through rosetting procedures were examined for the presence of ferritin by a direct immunofluorescence technique. Although ferritin was present in all lymphoid fractions studied, a significantly higher proportion of ferritin-containing cells were detected in the T-cell fraction than in the non-T-cell fraction, (mean +/- SD = 7.9 +/- 1.6% and 5.0 +/- 1.2%, respectively). T mu- and T gamma-cell fractions showed a twofold increase in the number of ferritin-positive cells (14.1 +/- 1.4% and 15.4 +/- 2.6%, respectively), as compared with Tar (7.0 +/- 0.9%)-and total lymphocyte (6.9 +/- 1.3%)-cell fractions. These results indicate that ferritin is preferentially distributed in T mu and T gamma lymphocytes and may constitute the basis for explaining some of the roles exercised by these cells in the control of other biological systems. 相似文献
946.
A E Sukhov G M Cha?chenko 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1989,39(5):828-835
In experiments on 56 healthy subjects (18-20 years old) the quality of their activity was determined during compensatory watching the mark at complicating regimes of work. Depending on the difficulty of the task five groups of subjects were singled out with optimum working capacity in one of four working conditions: normal, ordinary and strenuous work, model of stress situation. It is established that the change of the number of significant correlative connections between main parameters of psychophysiological state of man-operator reflects the condition of his functional systems. On the basis of computation of total range of organization values of both R-R intervals of the ECG and duration of expiration, the success of the man-operator work in complex conditions of activity is predicted. 相似文献
947.
948.
949.
E. R. Hargreaves 《BMJ (Clinical research ed.)》1950,1(4658):879-883
950.