全文获取类型
收费全文 | 2103篇 |
免费 | 118篇 |
专业分类
2221篇 |
出版年
2022年 | 7篇 |
2021年 | 23篇 |
2020年 | 12篇 |
2019年 | 19篇 |
2018年 | 26篇 |
2017年 | 26篇 |
2016年 | 34篇 |
2015年 | 63篇 |
2014年 | 70篇 |
2013年 | 86篇 |
2012年 | 132篇 |
2011年 | 119篇 |
2010年 | 74篇 |
2009年 | 70篇 |
2008年 | 100篇 |
2007年 | 77篇 |
2006年 | 93篇 |
2005年 | 101篇 |
2004年 | 106篇 |
2003年 | 87篇 |
2002年 | 69篇 |
2001年 | 39篇 |
2000年 | 53篇 |
1999年 | 49篇 |
1998年 | 37篇 |
1997年 | 28篇 |
1996年 | 33篇 |
1995年 | 25篇 |
1994年 | 21篇 |
1993年 | 20篇 |
1992年 | 39篇 |
1991年 | 23篇 |
1990年 | 36篇 |
1989年 | 44篇 |
1988年 | 43篇 |
1987年 | 35篇 |
1986年 | 31篇 |
1985年 | 39篇 |
1984年 | 31篇 |
1983年 | 28篇 |
1982年 | 21篇 |
1981年 | 20篇 |
1980年 | 12篇 |
1979年 | 17篇 |
1978年 | 17篇 |
1975年 | 10篇 |
1974年 | 10篇 |
1973年 | 11篇 |
1972年 | 7篇 |
1970年 | 13篇 |
排序方式: 共有2221条查询结果,搜索用时 0 毫秒
11.
An increase in the superoxide dismutase (SOD) activity inStreptococcus lactis was observed when the cells were grown at increased oxygen partial pressures or exposed to hyperbaric oxygen tensions. The NADH-oxidase/NADH-peroxidase activities inS. lactis increased in galactose-grown cells when cultivated in air compared with N2/CO2. This effect did not occur when glucose was the carbon source; however, an increase in the activities of these enzymes was observed in oxygen atmosphere. The correlation between SOD, NADH-oxidase/NADH-peroxidase, and the metabolic pathways involved is discussed. The effect of manganese on the SOD activity is also considered. 相似文献
12.
13.
14.
15.
The antihypertensive effect of atenolol, a new beta-1-receptor blocking agent, was studied in a double-blind trial in which 45 patients with essential hypertension were randomly assigned to placebo or atenolol treatment. Atenolol caused a statistically significant and clinically relevant reduction of blood pressure. The optimum daily dose for moderately severe hypertension was considered to be 200 mg. Several irrelevant side effects were collected by the use of a check list, but there was no difference in the number of complaints during placebo and active treatment. Atenolol has a useful antihypertensive effect and, at least theoretically, has advantages over other beta-adrenergic blocking agents. 相似文献
16.
Specific deoxyribonucleoside-activated nucleotidase (DAN) activity showed a rapid decline during the exponential increase in testis weight between 25 and 35 days of age. Specific DAN activity in Sertoli cells was dependent on the amount of cytosol in the enzyme assay. At optimal cytosol concentration the measured value was 50 units/mg of protein. Specific DAN activity in peritubular cells, primary spermatocytes and round spermatids was 13, 3.7 and 3.1 units/mg, respectively, and was independent of the cytosol concentration in the assay. 相似文献
17.
Cátia Fernandes-Cerqueira Elena Ossipova Sunithi Gunasekera Monika Hansson Linda Mathsson Anca I. Catrina Yngve Sommarin Lars Klareskog Karin Lundberg Johan R?nnelid Ulf G?ransson Per-Johan Jakobsson 《Arthritis research & therapy》2015,17(1)
IntroductionWe have previously identified endogenously citrullinated peptides derived from fibrinogen in rheumatoid arthritis (RA) synovial tissues. In this study, we have investigated the auto-antigenicity of four of those citrullinated peptides, and explored their feasibility to target anti-citrullinated protein/peptide antibodies (ACPA).MethodsThe autoantigenic potential of the fibrinogen peptides was investigated by screening 927 serum samples from the Epidemiological Investigation of RA (EIRA) cohort on a peptide microarray based on the ImmunoCAP ISAC® system. In order to assay for ACPA blocking, two independent pools of purified ACPA were incubated with the respective targeting peptide prior to binding to cyclic citrullinated peptide (CCP)2 using the CCPlus® ELISA kit.ResultsTwo peptides derived from the fibrinogen α chain, Arg573Cit (563-583) and Arg591Cit (580-600), referred to as Cit573 and Cit591, and two peptides from the fibrinogen β chain, Arg72Cit (62-81) and Arg74Cit (62-81) (Cit72 and Cit74), displayed 65 %, 15 %, 35 %, and 53 % of immune reactivity among CCP2-positive RA sera, respectively. In CCP2-negative RA sera, a positive reactivity was detected in 5 % (Cit573), 6 % (Cit591), 8 % (Cit72), and 4 % (Cit74). In the competition assay, Cit573 and Cit591 peptides reduced ACPA binding to CCP2 by a maximum of 84 % and 63 % respectively. An additive effect was observed when these peptides were combined. In contrast, Cit74 and Cit72 were less effective. Cyclization of the peptide structure containing Cit573 significantly increased the blocking efficiency.ConclusionsHere we demonstrate extensive autoantibody reactivity against in vivo citrullinated fibrinogen epitopes, and further show the potential use of these peptides for antagonizing ACPA. 相似文献
18.
19.
20.
Abstract. Vegetation changes in a semi‐natural grassland of wooded meadow type that had been grazed for centuries are described following the introduction of various management regimes: mowing each year, mowing every third year, burning, mechanical removal of woody plants, chemical treatment of woody plants, continuous grazing and abandonment. The experiment was established in southern Sweden in 1972 and has been in progress for 15 years. In 1972, 1980 and 1986 the botanical composition in these plots was investigated in permanent subplots. The study clearly demonstrates that mowing or grazing is necessary to preserve community structure and that mowing is to be preferred in cases where maintaining species richness is of primary concern. Mowing every third year delayed vegetation change and prevented woody species from spreading. Therefore, periodic mowing might be an alternative way to preserve the flora. In contrast, yearly burning does not seem to be a viable management in this type of semi‐natural grassland. To preserve the open landscape regeneration of woody plants has to be prevented. However, in plots where woody plants were removed the typical grassland flora declined. Abandonment resulted in closed forest. 相似文献