全文获取类型
收费全文 | 1904篇 |
免费 | 203篇 |
国内免费 | 1篇 |
专业分类
2108篇 |
出版年
2023年 | 9篇 |
2022年 | 16篇 |
2021年 | 44篇 |
2020年 | 26篇 |
2019年 | 44篇 |
2018年 | 48篇 |
2017年 | 35篇 |
2016年 | 49篇 |
2015年 | 92篇 |
2014年 | 89篇 |
2013年 | 103篇 |
2012年 | 157篇 |
2011年 | 130篇 |
2010年 | 89篇 |
2009年 | 83篇 |
2008年 | 112篇 |
2007年 | 84篇 |
2006年 | 104篇 |
2005年 | 78篇 |
2004年 | 88篇 |
2003年 | 74篇 |
2002年 | 77篇 |
2001年 | 26篇 |
2000年 | 29篇 |
1999年 | 33篇 |
1998年 | 26篇 |
1997年 | 26篇 |
1996年 | 10篇 |
1995年 | 12篇 |
1994年 | 16篇 |
1993年 | 17篇 |
1992年 | 17篇 |
1991年 | 23篇 |
1990年 | 16篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 17篇 |
1985年 | 17篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 9篇 |
1972年 | 10篇 |
排序方式: 共有2108条查询结果,搜索用时 15 毫秒
21.
Structural and functional relationships between Pasteurella multocida and enterobacterial adenylate cyclases. 总被引:3,自引:2,他引:1 下载免费PDF全文
The Pasteurella multocida adenylate cyclase gene has been cloned and expressed in Escherichia coli. The primary structure of the protein (838 amino acids) deduced from the corresponding nucleotide sequence was compared with that of E. coli. The two enzymes have similar molecular sizes and, based on sequence conservation at the protein level, are likely to be organized in two functional domains: the amino-terminal catalytic domain and the carboxy-terminal regulatory domain. It was shown that P. multocida adenylate cyclase synthesizes increased levels of cyclic AMP in E. coli strains deficient in the catabolite gene activator protein compared with wild-type strains. This increase does not occur in strains deficient in both the catabolite gene activator protein and enzyme III-glucose, indicating that a protein similar to E. coli enzyme III-glucose is involved in the regulation of P. multocida adenylate cyclase. It also indicates that the underlying process leading to enterobacterial adenylate cyclase activation has been conserved through evolution. 相似文献
22.
A gene encoding a tyrosine tRNA synthetase is located near sacS in Bacillus subtilis. 总被引:10,自引:0,他引:10
Within the frame of an attempt to sequence the whole Bacillus subtilis genome, a region of 5.5 kbp of the B. subtilis chromosome near the sacS locus has been sequenced. It contains five complete coding sequences, including the sequence of sacY, three unknown CDS and a sequence coding for a tyrosine tRNA synthetase. That the corresponding CDS encodes a functional synthetase has been demonstrated by complementation of an Escherichia coli mutant possessing a thermosensitive tRNA synthetase. Insertion of a kanamycin resistance cassette in the B. subtilis chromosome at the corresponding locus resulted, however, in no apparent phenotype, demonstrating that this synthetase is dispensable. Finally phylogenetic relationships between known tyrosine and tryptophan tRNA synthetases are discussed. 相似文献
23.
24.
J Etienne A Grüber J Polonovski 《Comptes rendus des séances de la Société de biologie et de ses filiales》1976,170(6):1159-1165
When partially purified platelet-rat lysate is injected in the rat aorta, transformation of prophospholipase into phospholipase is observed. Blood prophospholipases are activated almost entirely during about 15 minutes; aortic phospholipase are entirely activated for a longer time. 相似文献
25.
Lipoprotein lipase (EC 3.1.1.3) from rat adipose tissue was purified by affinity chromatography with heparin-Sepharose. Elution was carried out with buffered solutions of increasing NaCl molarity. Proteins without affinity for heparin were eluted with 0.5 M NaCl, while lipoprotein lipase activity was eluted as two peaks with 1.16 M NaCl (In earlier work on human adipose tissue (Etienne et al. (1974) C.R. Acad. Sc. Paris 279, 1487-1490) two fractions with lipoprotein lipase activity were also obtained). Phospholipase activity was detected in the fraction eluted with buffered 0.5 M NaCl and containing proteins without affinity for heparin. On feeding the fasting rats with fresh cream or glucose two peaks were also obtained, but the first peak had clearly increased while the second one had remained virtually unchanged. 相似文献
26.
Coagulase-negative staphylococci isolated from two cases of toxic shock syndrome lack superantigenic activity, but induce cytokine production 总被引:1,自引:0,他引:1
G. Lina A. Fleer J. Etienne T.B. Greenland F. Vandenesch 《FEMS immunology and medical microbiology》1996,13(1):81-86
Abstract Two strains of Staphylococcus epidermidis isolated from patients with toxic shock symptoms have been reported to carry genes related to S. aureus enterotoxins B and C by dot-blot hybridisation, although the corresponding superantigenic toxins were not detected immunologically. We here show that these strains produce no superantigens capable of stimulating proliferation of human mononuclear leukocytes or rabbit splenocytes, and that no DNA homologous to the seb or sec genes can be detected by PCR. However, stimulation of human monocytes by whole killed bacteria induced dose-dependent production of the cytokines TNFα, IL-1 β and IL-6, which may be responsible for the clinical symptoms in these patients. 相似文献
27.
Quiniou N Richard S Mourot J Etienne M 《Animal : an international journal of animal bioscience》2008,2(11):1633-1644
Two trials were carried out to compare the effects of fat or starch inclusion in sow's diet on sow and litter performance. In each trial, sows were assigned to one of two treatments. In trial 1, the sows were fed diets containing either soybean oil (5%, treatment GL5) or cornstarch (11.3%, GL0) from day 35 of gestation to weaning. Daily net energy and nutrient allowance were equalised during gestation. In trial 2, the same treatments were applied only after farrowing (treatments L5 and L0, respectively). Within each trial, a batch of piglets was studied until slaughter. In trial 1, adipose cell development and total lipid content were determined on some pigs at weaning (n = 6/treatment) and at slaughter in dorsal subcutaneous adipose tissue (n = 13/group at least) and in muscle (n = 46/group at least). Piglets' birth weight was not affected by treatment in trial 1. Survival rates at birth and after 24 h of life were higher in treatment GL5 (4.0% v. 7.5% stillborn piglets in GL0 treatment, P < 0.05; 8.7% v. 12.6% of piglets alive at 24 h of age died in treatment GL0, P = 0.06). Subsequently, overall survival rate until weaning was higher in treatment GL5 (81.4% v. 75.7% of total born piglets, P = 0.03), but litter size at weaning was not significantly affected (11.3). Litter growth rate before weaning was increased when a fat-enriched diet was provided during gestation and lactation (+140 g/day per litter; P < 0.01) and to a lower extent when provided only after farrowing (+90 g/day; P < 0.05). Energy supply through fat did not decrease the mobilisation of the sow's body reserve and backfat thickness loss was even higher with treatment GL5 (P < 0.05). After weaning, pigs' average daily gain, feed : gain ratio and carcass lean content were not affected by the energy source supplied before and/or after farrowing. At weaning, the number of adipose cells in the dorsal subcutaneous adipose tissue and in the Longissimus dorsi muscle was higher in the GL5 pigs. Muscle lipid content at weaning did not differ between treatments, but it was higher at slaughter, around 110 kg, in the GL5 pigs (3.46% v. 2.58%, P < 0.001). 相似文献
28.
Di Marco GS Alam A Dol F Corvol P Gasc JM Larger E 《Molecular medicine (Cambridge, Mass.)》2008,14(11-12):705-714
Hyperglycemia induces defects in angiogenesis without alteration in the expression of major vascular growth factors in the chicken chorioallantoic membrane (CAM) model. A direct negative effect of hyperglycemia on angiogenesis may participate in failures of "therapeutic angiogenesis" trials. Here, we tested the hypothesis that the response to pro-angiogenic molecules such as angiotensin-converting enzyme (ACE), endothelin-1 (ET-1), and vascular endothelial growth factor-A (VEGF) is altered by hyperglycemia. Transfected (Chinese hamster ovary [CHO] or human embryonic kidney [HEK]) cells overexpressing ACE, ET-1, or VEGF were deposed onto the CAM of hyperglycemic or control embryos. The proangiogenic effect was evaluated 3 d later by angiography and histological analyses. Gene expression in response to these factors was assessed by in situ hybridization. Only VEGF overexpression evoked a proangiogenic response in the CAM from hyperglycemic embryos, upregulating the expression of endogenous VEGF, VEGF-R2, and Tie-2, all of them related to activation of endothelial cells. In conclusion, in a model where hyperglycemia does not alter the major vascular growth factor expression, the negative effect of diabetes on capillary density was overcome only by VEGF overexpression, whereas responses to other vasoactive peptides were practically abolished under hyperglycemic conditions. 相似文献
29.
A PCR-Based Method for Monitoring Legionella pneumophila in Water Samples Detects Viable but Noncultivable Legionellae That Can Recover Their Cultivability 下载免费PDF全文
30.
Hans Lambers Felipe Albornoz Lukasz Kotula Etienne Laliberté Kosala Ranathunge François P. Teste Graham Zemunik 《Plant and Soil》2018,424(1-2):11-33