全文获取类型
收费全文 | 927篇 |
免费 | 80篇 |
专业分类
1007篇 |
出版年
2021年 | 16篇 |
2019年 | 5篇 |
2018年 | 18篇 |
2016年 | 14篇 |
2015年 | 29篇 |
2014年 | 27篇 |
2013年 | 29篇 |
2012年 | 61篇 |
2011年 | 50篇 |
2010年 | 34篇 |
2009年 | 25篇 |
2008年 | 33篇 |
2007年 | 47篇 |
2006年 | 56篇 |
2005年 | 29篇 |
2004年 | 44篇 |
2003年 | 32篇 |
2002年 | 18篇 |
2001年 | 18篇 |
2000年 | 37篇 |
1999年 | 21篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 22篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 19篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 9篇 |
1976年 | 6篇 |
1975年 | 10篇 |
1974年 | 9篇 |
1972年 | 11篇 |
1969年 | 6篇 |
1967年 | 6篇 |
1966年 | 4篇 |
1882年 | 4篇 |
1877年 | 4篇 |
排序方式: 共有1007条查询结果,搜索用时 0 毫秒
71.
Kramer K Voss HP Grimbergen JA Mills PA Huetteman D Zwiers L Brockway B 《Laboratory animals》2000,34(3):272-280
This paper describes for the first time the possibility for recording the systolic pressure (SP), diastolic pressure (DP), and the mean arterial pressure (MAP) as well as the heart rate (HR) and locomotor activity (LA) in freely moving mice, using a commercially available telemetry and data acquisition system. The system comprises a new, small radio-telemetry transmitter implanted in the peritoneal cavity, a receiver board placed underneath the home cage, a multiplexer and a computer-based data acquisition system. The signals from the receiver were consolidated by the multiplexer and were stored and analysed by the computer. The telemetered pressure signals (absolute pressure) were corrected automatically for changes in atmospheric pressure measured by an ambient pressure monitor. The effects of implantation on animal behaviour, and, after the animals had recovered, the effects of handling on the SP, DP, MAP and HR were examined. The radio-telemetry system for recording the SP, DP, MAP and HR provides an accurate and reliable method for monitoring the direct effects of handling on SP, DP, MAP and HR. In addition, by using this new blood pressure (BP) transmitter, we maintain that BP measurements in freely moving mice are more efficient, reliable, and less labour-intensive than the measurement techniques described in the literature thus far. 相似文献
72.
John M. Burke Tiffany J. Voss Michael L. Arnold 《Evolution; international journal of organic evolution》1998,52(5):1304-1310
Hybridization between divergent lineages has long been assumed to give rise to unfavorable interactions between the parental genomes. These deleterious genetic interactions are further assumed to result in the production of hybrid offspring with decreased levels of viability and/or fertility. To test this assumption, we investigated the role of both nuclear and cytonuclear epistatic interactions in determining the frequencies of F2 genotypes produced in crosses between two species of Louisiana iris, Iris fulva and I. brevicaulis. Overall, these crosses revealed a significant deficit of intermediate hybrid genotypes accompanied by an excess of parental-like genotypes, suggesting that genetic interactions may promote postmating reproductive isolation between these species. However, analyses of single and multilocus segregation patterns revealed a variety of negative and positive interactions between the genomes of the parental taxa at the nuclear and cytonuclear levels. Taken together, these results indicate that the traditional view that interactions between divergent genomes are always deleterious is an oversimplification. Rather, it seems likely that crosses between divergent lineages can lead to the production of both fit and unfit hybrid genotypes. 相似文献
73.
74.
Background
Evidence based and gender specific knowledge about sickness absence following coronary revascularisation is lacking. The objective was to investigate sickness absence after a first coronary artery bypass grafting (CABG) or percutaneous coronary intervention (PCI) among women and men in a national Swedish study.Materials and Methods
All patients 30–63 years of age, who underwent a first CABG (n = 22,985, 16% women) or PCI (40,891, 22% women) in Sweden between 1994 and 2006 were included. Information on sickness absence, co-morbidity, and other patient characteristics was obtained from national registers. Long-term sickness absence (LTSA) was defined as >180 and >90 sick-leave days in the first sick-leave spell following CABG and PCI, respectively. Prevalence ratio (PR) and 95% confidence interval (CI) of LTSA were calculated.Findings
LTSA followed the interventions in 41% and 36% for CABG and PCI patients, respectively. Women had more often LTSA compared with men, (CABG PR = 1.23: 95% CI 1.19–1.28 and PCI PR = 1.19; 95% CI 1.16–1.23). A history of sickness absence the year before the intervention increased the risk for LTSA after the intervention in both genders. Among women, older age, or being self employed or unemployed was associated with a lower risk for LTSA. Among men previous cardiovascular disease, diabetes and low socio-economic position increased the risk. During the observation period, there was no change in sickness absence rates among PCI patients but an increase among CABG patients adjusting for patient characteristics.Conclusion
This national study covering a 13-year period shows that long-term sickness absence following coronary revascularisation is common in Sweden, especially among women, and is associated with socio-economic position, co-morbidity, and sickness absence during the year before the intervention. Gender specific scientific knowledge about use and effects of sickness absence following coronary revascularisation is warranted for the patients, the treating physicians, the healthcare sector, and the society. 相似文献75.
Katharina Zetterstr?m Margaretha Voss Kristina Alexanderson Torbj?rn Ivert Kenneth Pehrsson Niklas Hammar Marjan Vaez 《PloS one》2015,10(8)
Background
Although coronary revascularisation by coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI) are common procedures, little is known regarding disability pension (DP) at the time of coronary revascularisation and its association with mortality. The aim was to investigate the five-year mortality following a first coronary revascularisation among women and men on DP, compared with those not on DP at the time of intervention, accounting for socio-demographic and medical factors.Material and Methods
A nationwide prospective population-based cohort study was conducted, using national registers including 70,040 patients (80% men), aged 30–64 years, with a first CABG (n = 24,987; 36%) or PCI (n = 45,053; 64%) during 1994–2006 in Sweden, who were alive 30 days after the intervention. The main outcome was all-cause and cause-specific mortality within five years or through 31 December 2006, following CABG and PCI, and the exposure was DP at the time of a first coronary revascularisation. Information on DP, patient characteristics, date and cause of death was obtained from nationwide registers. Hazard ratios (HR) with 95% confidence intervals (CI) for the outcome were estimated, using Cox proportional hazard regression analyses. All analyses were stratified by type of intervention and gender.Findings
Four percent died following coronary revascularisation. Cardiovascular disease was the most common cause of death (54%), followed by neoplasms (25%). Regardless of type of intervention, gender and after multivariable adjustments, patients on DP had a higher HR for five-year mortality compared with those not on DP at time of revascularisation (CABG: women HR 2.14; 95% CI 1.59–2.89, men HR 2.09; 1.84–2.38, PCI: women HR 2.25; 1.78–2.83, men HR 1.95; 1.72–2.21). Young women on DP at the time of PCI had a substantially higher HR (HR 4.10; 95% CI: 2.25–7.48).Conclusion
Patients on DP at the time of first coronary revascularisation had a higher five-year risk of mortality compared with those not on DP. 相似文献76.
Zheng X Hudyma TW Martin SW Bergstrom C Ding M He F Romine J Poss MA Kadow JF Chang CH Wan J Witmer MR Morin P Camac DM Sheriff S Beno BR Rigat KL Wang YK Fridell R Lemm J Qiu D Liu M Voss S Pelosi L Roberts SB Gao M Knipe J Gentles RG 《Bioorganic & medicinal chemistry letters》2011,21(10):2925-2929
Herein, we present initial SAR studies on a series of bridged 2-arylindole-based NS5B inhibitors. The introduction of bridging elements between the indole N1 and the ortho-position of the 2-aryl moiety resulted in conformationally constrained heterocycles that possess multiple additional vectors for further exploration. The binding mode and pharmacokinetic (PK) properties of select examples, including: 13-cyclohexyl-6-oxo-6,7-dihydro-5H-indolo[2,1-d][1,4]benzodiazepine-10-carboxylic acid (7) (IC50 = 0.07 μM, %F = 18), are reported. 相似文献
77.
Kenneth A. Voss Ronald D. Plattner Charles W. Bacon William P. Norred 《Mycopathologia》1990,112(2):81-92
Fusarium moniliforme has been associated with several diseases including equine leukoencephalomalacia, human esophageal cancer and hepatotoxicity/hepatocarcinogenicity in laboratory animals. The potential health risks to animals and humans posed by F. moniliforme contaminated grains cannot be assessed until the toxins are identified and toxicologically evaluated. As part of a systematic approach to identifying the hepatotoxins produced by F. moniliforme, diets containing aqueous and chloroform/methanol (11) extracts of F. moniliforme strain MRC 826 culture material (CM) and/or the extracted CM residues were fed to male Sprague-Dawley rats for four weeks. Serum alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase activities were increased after two and four weeks and microscopic liver lesions were found in those animals fed aqueous CM extract and the CM residue after chloroform/ methanol extraction. Fumonisins B1 and B2 were extracted from the CM by water, but not chloroform/ methanol, and were present in the toxic diets at concentrations of 93–139 and 82–147 ppm, respectively. Nontoxic diets contained 22 ppm fumonisin B1 and 65 ppm fumonisin B2.Abbreviations CM
culture material
- ELEM
equine leukoencephalomalacia
Mention of a trademark, proprietory name or vendor does not imply its approval by the US Department of Agriculture to the exclusion of others that may also be suitable. 相似文献
78.
A Emami-Khoyi DA Hartley RH Cruickshank LJ Boren JG Ross 《New Zealand journal of zoology.》2016,43(4):322-335
New Zealand fur seals are one of many pinniped species that survived the commercial sealing of the eighteenth and nineteenth centuries in dangerously low numbers. After the enforcement of a series of protection measures in the early twentieth century, New Zealand fur seals began to recover from the brink of extinction. We examined the New Zealand fur seal populations of Banks Peninsula, South Island, New Zealand using the mitochondrial DNA control region. We identified a panmictic population structure around Banks Peninsula. The most abundant haplotype in the area showed a slight significant aggregated structure. The Horseshoe Bay colony showed the least number of shared haplotypes with other colonies, suggesting a different origin of re-colonisation of this specific colony. The effective population size of the New Zealand fur seal population at Banks Peninsula was estimated at approximately 2500 individuals. The exponential population growth rate parameter for the area was 35, which corresponds to an expanding population. In general, samples from adjacent colonies shared 4.4 haplotypes while samples collected from colonies separated by between five and eight bays shared 1.9 haplotypes. The genetic data support the spill-over dynamics of colony expansion already suggested for this species. Approximate Bayesian computations analysis suggests re-colonisation of the area from two main clades identified across New Zealand with a most likely admixture coefficient of 0.41 to form the Banks Peninsula population. Approximate Bayesian computations analysis estimated a founder population size of approximately 372 breeding individuals for the area, which then rapidly increased in size with successive waves of external recruitment. The population of fur seals in the area is probably in the late phase of maturity in the colony expansion dynamic. 相似文献
79.
The cyanophycin synthetase gene cphA1 encoding the major cyanophycin synthetase (CphA) of Anabaena sp. strain PCC7120 was expressed in Escherichia coli conferring so far the highest specific CphA activity to E. coli (6.7 nmol arginine per min and mg protein). CphA1 and cphA genes of Synechocystis sp. strains PCC6803 and PCC6308 and Synechococcus strain MA19 were also expressed in wild types and polyhydroxyalkanoate-negative (PHA) mutants of Pseudomonas putida and Ralstonia eutropha. Recombinant strains of these bacteria expressing cphA1 accumulated generally more cyanophycin (23.0 and 20.0% of cellular dry matter, CDM, respectively) than recombinants expressing any other cphA (6.8, 9.0, or 15.8% of CDM for P. putida strains and 7.3, 12.6, or 14.1% of CDM for R. eutropha). Furthermore, PHA-negative mutants of P. putida (9.7, 10.0, 17.5, or 24.0% of CDM) and R. eutropha (8.9, 13.8, 16.0, or 22.0% of CDM) accumulated generally more cyanophycin than the corresponding PHA-positive parent strains (6.8, 9.0, 15.8, and 23.0% of CDM for P. putida strains and 7.3, 12.6, 14.1, or 20.0% of CDM for R. eutropha strains). Recombinant strains of Gram-positive bacteria (Bacillus megaterium, Corynebacterium glutamicum) were not suitable for cyanophycin production due to accumulation of less cyanophycin and retarded release of cyanophycin. PHA-negative mutants of P. putida and R. eutropha expressing cphA1 of Anabaena sp. strain PCC7120 are therefore preferred candidates for industrial production of cyanophycin. 相似文献
80.
Mansouri A Voss AK Thomas T Yokota Y Gruss P 《Development (Cambridge, England)》2000,127(11):2251-2258
The expression of the homeobox gene Uncx4.1 in the somite is restricted to the caudal half of the newly formed somite and sclerotome. Here we show that mice with a targeted mutation of the Uncx4.1 gene exhibit defects in the axial skeleton and ribs. In the absence of Uncx4.1, pedicles of the neural arches and proximal ribs are not formed. In addition, dorsal root ganglia are disorganized. Histological and marker analysis revealed that Uncx4.1 is not necessary for somite segmentation. It is required to maintain the condensation of the caudal half-sclerotome, from which the missing skeletal elements are derived. The loss of proximal ribs in Pax1/Pax9 double mutants and the data presented here argue for a role of Uncx4.1 upstream of Pax9 in the caudolateral sclerotome. Our results further indicate that Uncx4.1 may be involved in the differential cell adhesion properties of the somite. 相似文献