全文获取类型
收费全文 | 2539篇 |
免费 | 98篇 |
专业分类
2637篇 |
出版年
2022年 | 14篇 |
2021年 | 23篇 |
2020年 | 19篇 |
2019年 | 19篇 |
2018年 | 31篇 |
2017年 | 34篇 |
2016年 | 48篇 |
2015年 | 60篇 |
2014年 | 87篇 |
2013年 | 153篇 |
2012年 | 121篇 |
2011年 | 123篇 |
2010年 | 67篇 |
2009年 | 75篇 |
2008年 | 130篇 |
2007年 | 125篇 |
2006年 | 131篇 |
2005年 | 146篇 |
2004年 | 138篇 |
2003年 | 93篇 |
2002年 | 134篇 |
2001年 | 98篇 |
2000年 | 82篇 |
1999年 | 72篇 |
1998年 | 32篇 |
1997年 | 28篇 |
1996年 | 19篇 |
1995年 | 15篇 |
1994年 | 14篇 |
1993年 | 29篇 |
1992年 | 63篇 |
1991年 | 37篇 |
1990年 | 33篇 |
1989年 | 30篇 |
1988年 | 30篇 |
1987年 | 26篇 |
1986年 | 32篇 |
1985年 | 34篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 18篇 |
1978年 | 17篇 |
1976年 | 9篇 |
1975年 | 11篇 |
1974年 | 10篇 |
1972年 | 9篇 |
1968年 | 10篇 |
排序方式: 共有2637条查询结果,搜索用时 0 毫秒
1.
BACKGROUND: We report a successful pregnancy in a woman with severe ovarian dysfunction and infertility associated with a variant beta-subunit of luteinizing hormone (LH). METHOD/OUTCOME: A 35-year-old woman consulted our unit for infertility. Laparoscopy and ultrasonography showed obstruction of the right tube and ovulation from the right ovary only. Human menopausal gonadotrophin (hMG) therapy was used for six subsequent cycles, but did not result in conception. Subsequently, marked elevation of follicle-stimulating hormone (FSH) and testosterone, together with polycystic ovary (PCO) were noted. The patient failed to respond to ovarian stimulation by hMG. Severe ovarian dysfunction such as premature ovarian failure (POF) was strongly suspected. Sequence analysis of the LH beta-subunit gene indicated heterozygosity for point mutations Trp(8) to Arg(8) and Ile(15) to Thr(15) in the coding sequence. LH hypersecretion resembling that seen in PCO syndrome was observed. Induction of ovulation by hMG was successful in the first cycle in which the basal LH and FSH were well controlled with gonadotrophin-releasing hormone analog following estrogen-progesterone replacement. She conceived and delivered a healthy male infant at term. CONCLUSION: Clinicians should be clinically aware of patients with immunologically anomalous LH variant who might be at risk of developing ovarian failure within a relatively short time span. Pertinent treatment should be applied without delay in such cases. 相似文献
2.
Changes in the antibiotic production by co-culture of Rhizopus peka P8 and Bacillus subtilis IFO3335
Tsubasa Fukuda Shintaro Yamamoto Hiroshi Morita 《World journal of microbiology & biotechnology》2008,24(9):1893-1899
The co-culture of Bacillus subtilis IFO 3335 with Rhizopus peka P8 or Rhizopus oligosporus P12 in liquid medium was found to increase production of antibiotic activity and to alter the spectrum of activity relative
to the pure cultures. However, a mixed culture of Rhizopus
arrhizus P7 and Rhizopus oryzae P17 did not produce antibiotic activity. The concentration, ratio, and time of addition of B. subtilis to the R. peka culture was found to influence antibiotic yields. Solid-state fermentations using mixed cultures of R. peka and B. subtilis were investigated. The growth of Escherichia coli IFO 3792 as a target bacterium was inhibited by the mixed culture. These results suggest the possibility of biopreservation
of fermented foods by novel co-culture systems. 相似文献
3.
4.
Some aphid species are attended by ants, which protect aphids against enemies, but ants sometimes prey on the aphids they are attending depending on the resource conditions. A previous study indicated that the ant Lasius niger preys less on the aphid individuals that experienced ant attendance than on those that did not. This observation leads to the hypothesis that ants transfer some substances to the aphids they attend and selectively prey on the aphids without the substances. In this study, we focus on cuticular hydrocarbons (CHCs), which are used by ants as nestmate recognition substances, and test whether ants discriminate the aphids on the basis of CHCs. We confirmed that the ant Lasius fuji preyed less on the aphids that were attended by their nestmates than those that were not attended. Glass dummies treated with CHCs from attended aphids were attacked less by ants than those treated with CHCs from non-attended aphids. The CHC profiles of ant attended aphids resembled those of the ants, suggesting that ants’ CHCs are transferred to the aphids’ body surface through ant attendance. These results support the hypothesis that ants “mark” their attended aphids with their CHCs and the CHCs reduce ant predation intensity. 相似文献
5.
6.
T Kimura K Miyazaki J Yamashita T Horio T Kakuno 《Biochimica et biophysica acta》1992,1118(3):239-248
Normal rabbit serum contained two kinds of growth-inhibitory protein, GI-I and GI-II, in latent forms. These latent inhibitors were activated by incubation at 37 degrees C for 12 h, and their activation was lowered by inhibitors for serine, cysteine and metalloproteinases. Both growth inhibitors were highly purified in active forms by successive column chromatographies. GI-I showed a major protein band with an Mr of 18,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, while GI-II showed a major protein band with an Mr of 36,000. GI-I and GI-II half-inhibited the growth of rat tumorigenic cell line (RSV-BRL) at concentrations of 0.5 ng/ml and 10 ng/ml, excess concentrations. Of the 15 cell lines tested, GI-I specifically inhibited the growth of rodent and lagomorph cells, whereas GI-II nonspecifically inhibited the growth of all cell lines tested. Specificities for cell type and malignancy were not observed with either inhibitor. These growth inhibitors were stable to a reducing reagent and proteinase inhibitors, but labile to urea, acid, organic solvents, trypsin, plasmin and heating at 95 degrees C for 5 min. These properties suggested that both growth inhibitors might be distinct from known growth-inhibitory factors. 相似文献
7.
Shimizu H Toyama O Shiota M Kim-Mitsuyama S Miyazaki H 《Journal of receptor and signal transduction research》2005,25(1):19-33
The present study examined the cellular functions of low-molecular-weight protein tyrosine phosphatase (LMW-PTP), which consists of two active isoforms IF-1 and IF-2, in vascular smooth muscle cells (VSMCs) and endothelial cells (ECs), focusing on cell growth and migration. We transduced recombinant IF-1 and IF-2, and ribozyme targeting both isoforms using an adenovirus vector in these cells. We detected the expression of IF-1 and IF-2 in both types of cells. IF-1 as well as IF-2 inhibited PDGF-induced DNA synthesis and migration in VSMCs. In contrast, both isoforms enhanced lysophosphatidic acid-stimulated cell migration without change in DNA synthesis in ECs. Whereas there is a report indicating that reactive oxygen species-dependent inactivation of LMW-PTP regulates actin cytoskeleton reorganization during cell spreading and migration, the isoforms conversely suppressed the PDGF-induced H2O2 generation with subsequent decrease in the p38 activity in VSMCs. Catalytically inactive LMW-PTP exerted the opposite and similar effects to the wild type in ECs and in VSMCs, respectively, suggesting that substrates for the phosphatase differ between these cells. Moreover, high concentrations of glucose suppressed the expression of LMW-PTP in both cells. These data suggest that LMW-PTP negatively regulates the pathogenesis of atherosclerosis and that glucose-dependent suppression of LMW-PTP expression may promote the development of atherosclerosis in diabetics. 相似文献
8.
[6, 7-3H]-17beta-Estradiol-3-glucosiduronate, [6, 7-3H]-estrone-3-glucosiduronate or [6, 7-3H]-estrone was administered intravenously into the rabbit, and analysis and identification of the urinary metabolites were carried out. In either case, the major urinary metabolite was found to be a diconjugate. The sequential enzymic hydrolysis indicated that this diconjugate was glucosiduronate-N-acetyglucosaminide of 17alpha-estradiol. From these results, the conversion of the estrogen glucosiduronate into a diconjugate was thought a rather universal phenomenon in the rabbit. 相似文献
9.
10.
Reproductive behaviors related to habitat utilization were studied in males of the damsefly,Mnais nawai, which has two male forms, territorial orange-winged males (nawai) and non-territorial pale-orange-winged males (sahoi), at the upper part of a mountain stream where they partiallycoexist with a related species,Mnais pruinosa, which also has two male forms, territorial orange-winged males (esakii) and non-territorial hyaline-winged males (strigata). These two species showed parapatric distribution; the lower part of the stream was occupied byM. nawai, and the upper part byM. pruinosa. In the present study, cross-matings occurred between bothMnais species, although normal intraspecific matings occurred more frequently than cross-matings. Territorial males of both species copulated with conspecific females that entered their territory and guarded the ovipositing females, probably to avoid sperm displacement resulting from subsequent copulations. Severe competition for oviposition sites by territorial males even occurred between the two species. On the other hand, non-territorial males of both species have alternative mating strategies (including several tactics such as sneaking, takeover and interception). The possible benefits from conflict among territorial males of both species is discussed. 相似文献