全文获取类型
收费全文 | 1172篇 |
免费 | 106篇 |
国内免费 | 2篇 |
专业分类
1280篇 |
出版年
2023年 | 3篇 |
2022年 | 15篇 |
2021年 | 36篇 |
2020年 | 23篇 |
2019年 | 26篇 |
2018年 | 29篇 |
2017年 | 28篇 |
2016年 | 29篇 |
2015年 | 50篇 |
2014年 | 62篇 |
2013年 | 102篇 |
2012年 | 83篇 |
2011年 | 78篇 |
2010年 | 39篇 |
2009年 | 46篇 |
2008年 | 43篇 |
2007年 | 57篇 |
2006年 | 43篇 |
2005年 | 60篇 |
2004年 | 40篇 |
2003年 | 51篇 |
2002年 | 40篇 |
2001年 | 23篇 |
2000年 | 22篇 |
1999年 | 18篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 11篇 |
1995年 | 4篇 |
1994年 | 14篇 |
1993年 | 15篇 |
1992年 | 13篇 |
1991年 | 16篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 13篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1973年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有1280条查询结果,搜索用时 0 毫秒
81.
Essmann F Bantel H Totzke G Engels IH Sinha B Schulze-Osthoff K Jänicke RU 《Cell death and differentiation》2003,10(11):1260-1272
Recent data suggest that alpha-toxin, the major hemolysin of Staphylococcus aureus, induces cell death via the classical apoptotic pathway. Here we demonstrate, however, that although zVAD-fmk or overexpression of Bcl-2 completely abrogated caspase activation and internucleosomal DNA fragmentation, they did not significantly affect alpha-toxin-induced death of Jurkat T or MCF-7 breast carcinoma cells. Caspase inhibition had also no effect on alpha-toxin-induced lactate dehydrogenase release and ATP depletion. Furthermore, whereas early assessment of apoptosis induction by CD95 resulted solely in the generation of cells positive for active caspases that were, however, not yet permeable for propidium iodide, a substantial proportion of alpha-toxin-treated cells were positive for both active caspases and PI. Finally, electron microscopy demonstrated that even in the presence of active caspases, alpha-toxin-treated cells displayed a necrotic morphology characterized by cell swelling and cytoplasmic vacuolation. Together, our data suggest that alpha-toxin-induced cell death proceeds even in the presence of activated caspases, at least partially, in a caspase-independent, necrotic-like manner. 相似文献
82.
We show that explicit mathematical and biological relationships exist among the scaling exponents and the allometric constants (α and β, respectively) of log–log linear tree‐community size frequency distributions, plant density NT, and minimum, maximum and average stem diameters (Dmin, Dmax, and , respectively). As individuals grow in size and Dmax increases, NT is predicted to decrease as reflected by a decrease in the numerical value of α and an increase in the value of β. Our derivations further show that NT decreases as increases even if Dmin or Dmax remain unchanged. Because Dmax and the age of the largest individuals in a community are correlated, albeit weakly, we argue that the interdependent relationships among the numerical values of α, β, NT, and shed light on the extent to which communities have experienced recent global disturbance. These predicted relationships receive strong statistical support using two large datasets spanning a broad spectrum of tree‐dominated communities. 相似文献
83.
The morbidity caused by schistosomiasis has been controlled in China, Egypt and the Philippines mainly by the widespread use of the safe and efficacious drug praziquantel (PZQ), and by oxamniquin and PZQ in Brazil. To date, there is no evidence of development of clinically relevant resistance. Thanks to the commitment of national governments at the World Health Assembly in 2001, and the emergence of significant funding for control, it is predicted that there will soon be more widespread use of PZQ in sub-Saharan Africa, where morbidity due to schistosomiasis is most prevalent. There are currently no available alternative drugs to PZQ (with the possible exception of oxamniquin), although perhaps PZQ analogues could be developed. Artemether, used to control malaria, is effective against immature schistosomes, but is less effective against adult worms. The efficacy of myrrh, recently marketed as an antischistosomacide in Egypt, has not been independently confirmed. 相似文献
84.
Jahn-Hofmann K Holzhey N Ellinger T Engels JW 《Nucleosides, nucleotides & nucleic acids》2003,22(5-8):1479-1482
We will insert a cleavage site in an oligodeoxynucleotide, which can be used for a selective and quantitative cleavage. For that reason we synthesized the four 5'-S-(4,4'-dimethoxytrityl)-mercapto-2'-deoxynucleotide-3'-O-(2-cyanoethoxydiisopropylamino)-phosphites (5a-d). The cleavage of P-S and C-S bonds is described (Mag, M.; Lücking, S.; Engels, J.W. Synthesis and selective cleavage of an oligodeoxy-nucleotide containing a bridged internucleotide 5'-phosphorthioate linkage. Nucleic Acids Res. 1991, 19 (7), 1437-1441; Marriott, J.H.; Mottahedeh, M.; Reese, C.B. 9-(4-methoxyphenyl)xanthen-9-thiol: A useful reagent for the preparation of thiols. Tetrahedron Lett. 1990, 31 (51), 7485-7488; Divakar, K.J.; Mottoh, A.; Reese, C.B.; Shanghvi, Y.S. Approaches to the synthesis of 2' thio analogues of pyrimidine ribosides. J. Chem. Sc., Perkin Trans. 1 1990, 969-974). The oligodeoxynucleotides with an achiral bridged 5'-phosphorothioate linkage 5'-O-P-S-3' are synthesized by the phosphoramidite procedure. 相似文献
85.
86.
Victoria L. Wyckelsma Tomas Venckunas Peter J. Houweling Maja Schlittler Volker M. Lauschke Chrystal F. Tiong Harrison D. Wood Niklas Ivarsson Henrikas Paulauskas Nerijus Eimantas Daniel C. Andersson Kathryn N. North Marius Brazaitis Håkan Westerblad 《American journal of human genetics》2021,108(3):446-457
87.
88.
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89.
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90.
Marcano M Pugh T Cros E Morales S Portillo Páez EA Courtois B Glaszmann JC Engels JM Phillips W Astorga C Risterucci AM Fouet O González V Rosenberg K Vallat I Dagert M Lanaud C 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2007,114(5):877-884
A sound understanding of crop history can provide the basis for deriving novel genetic information through admixture mapping.
We confirmed this, by using characterization data from an international collection of cocoa, collected 25 years ago, and from
a contemporary plantation. We focus on the trees derived from three centuries of admixture between Meso-American Criollo and
South American Forastero genomes. In both cacao sets of individuals, linkage disequilibrium extended over long genetic distances
along chromosome regions, as expected in populations derived from recent admixture. Based on loose genome scans, genomic regions
involved in useful traits were identified. Fifteen genomic regions involved in seed and fruit weight variation were highlighted.
They correspond to ten previously identified QTLs and five novel ones. Admixture mapping can help to add value to genetic
resources and thus, help to encourage investment in their conservation.
Maria Marcano and Tatiana Pugh contributed equally to this work. 相似文献