全文获取类型
收费全文 | 2735篇 |
免费 | 269篇 |
国内免费 | 2篇 |
专业分类
3006篇 |
出版年
2023年 | 19篇 |
2022年 | 27篇 |
2021年 | 42篇 |
2020年 | 40篇 |
2019年 | 47篇 |
2018年 | 48篇 |
2017年 | 48篇 |
2016年 | 67篇 |
2015年 | 137篇 |
2014年 | 138篇 |
2013年 | 161篇 |
2012年 | 246篇 |
2011年 | 230篇 |
2010年 | 139篇 |
2009年 | 130篇 |
2008年 | 194篇 |
2007年 | 172篇 |
2006年 | 160篇 |
2005年 | 165篇 |
2004年 | 159篇 |
2003年 | 147篇 |
2002年 | 144篇 |
2001年 | 26篇 |
2000年 | 15篇 |
1999年 | 23篇 |
1998年 | 33篇 |
1997年 | 19篇 |
1996年 | 19篇 |
1995年 | 28篇 |
1994年 | 13篇 |
1993年 | 20篇 |
1992年 | 16篇 |
1991年 | 15篇 |
1990年 | 18篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1974年 | 4篇 |
1969年 | 5篇 |
1967年 | 2篇 |
1963年 | 2篇 |
1962年 | 3篇 |
1955年 | 2篇 |
排序方式: 共有3006条查询结果,搜索用时 15 毫秒
91.
Boehm RA Muensterer OJ Till H 《Plastic and reconstructive surgery》2004,114(3):668-73; discussion 674-5
Surgical correction of pectus excavatum in children has gained new momentum since the introduction of the new minimally invasive repair by Nuss. To date, no studies directly evaluate the outcome of the new technique versus that of the conventional technique. From 2000 to 2002, 28 patients underwent pectus excavatum correction in the authors' hospital. Twenty-one were treated by minimally invasive repair of pectus excavatum and seven patients had open correction. Intraoperative and postoperative complications, clinical outcome, and patient satisfaction were evaluated. In the minimally invasive repair of pectus excavatum group, the children were younger (14.4 +/- 2.9 versus 17.8 +/- 3.2 years), had shorter operation times (53 +/- 18 versus 125 +/- 6 minutes), and had less blood loss (minimal versus 380 +/- 175 ml). No intraoperative complications were recorded. In the conventional group, two pleural lacerations occurred. Early postoperative complications in the minimally invasive repair group included two pneumothoraces and one case of pleural effusion. In the conventional group, one pneumothorax and one case of pleural effusion occurred. Late postoperative complications in the Nuss group included one costal erosion, two bar dislocations, one severe wound infection requiring bar removal, one hematothorax, and one case of postpericardiotomy syndrome; in the conventional group, there was one severe wound infection. In both groups, the patients rated their cosmetic results as good to very good. Minimally invasive repair of pectus excavatum is a novel method with clear advantages, such as limited surgical trauma and small scars. The high rate of postoperative complications may decrease with growing experience in the future. In well-selected patients (age, symmetric deformity), the Nuss procedure may become the method of choice. However, there is still a lack of long-term follow-up. 相似文献
92.
Haumann M Barra M Loja P Löscher S Krivanek R Grundmeier A Andreasson LE Dau H 《Biochemistry》2006,45(43):13101-13107
Chloride is an important cofactor in photosynthetic water oxidation. It can be replaced by bromide with retention of the oxygen-evolving activity of photosystem II (PSII). Binding of bromide to the Mn(4)Ca complex of PSII in its dark-stable S(1) state was studied by X-ray absorption spectroscopy (XAS) at the Br K-edge in Cl(-)-depleted and Br(-)-substituted PSII membrane particles from spinach. The XAS spectra exclude the presence of metal ions in the first and second coordination spheres of Br(-). EXAFS analysis provided tentative evidence of at least one metal ion, which may be manganese or calcium, at a distance of approximately 5 A to Br(-). The native Cl(-) ion may bind at a similar distance. Accordingly, water oxidation may not require binding of a halide directly to the metal ions of the Mn complex in its S(1) state. 相似文献
93.
Lena Kathe Reiner Krmer Holger Budahn Klaus Pillen Frank Rabenstein Thomas Nothnagel 《Journal of Phytopathology》2019,167(10):558-566
Fusarium oxysporum is one of the major pathogens causing root and crown rot in asparagus. Breeding of cultivars resistant to F. oxysporum would be the most efficient strategy for pathogen control. In this study, a bioassay was developed for screening seedling resistance. The non‐destructive bioassay comprises inoculation with a highly aggressive F. oxysporum isolate, incubation in a climate chamber and quantification of disease symptoms by a digital image analysing system and a PTA‐ELISA. This bioassay is simple to implement and demonstrated high reproducibility. Subsequently, it was used to determine the resistance behaviour of 16 asparagus genotypes to F. oxysporum. The asparagus cultivars revealed different levels of susceptibility, whereas the wild relative A. densiflorus was confirmed to be resistant. 相似文献
94.
Paul Maschhoff Sebastian Heene Antonina Lavrentieva Thorleif Hentrop Christian Leibold Marc‐Nils Wahalla Nils Stanislawski Holger Blume Thomas Scheper Cornelia Blume 《Engineering in Life Science》2017,17(5):567-578
Cardiovascular disease is the most common cause of death, accounting for 31% of deaths worldwide. As purely synthetic grafts implicate concomitant anticoagulation and autologous veins are rare, tissue‐engineered vascular grafts are urgently needed. For successful in vitro cultivation of a bioartificial vascular graft, the suitable bioreactor should provide conditions comparable to vasculogenesis in the body. Such a system has been developed and characterized under continuous and pulsatile flow, and a variety of sensors has been integrated into the bioreactor to control parameters such as temperature, pressure up to 500 mbar, glucose up to 4.5 g/L, lactate, oxygen up to 150 mbar, and flow rate. Wireless data transfer (using the ZigBee specification based on the IEEE 802.15.4 standard) and multiple corresponding sensor signal processing platforms have been implemented as well. Ultrasound is used for touchless monitoring of the growing vascular structure as a quality control before implantation (maximally achieved ultrasound resolution 65 μm at 15 MHz). To withstand the harsh conditions of steam sterilization (120°C for 20 min), all electronics were encapsulated. With such a comprehensive physiologically conditioning, sensing, and imaging bioreactor system, all the requirements for a successful cultivation of vascular grafts are available now. 相似文献
95.
Ringseis R Heller K Kluge H Eder K 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2011,158(4):450-454
Rodents are able to lower fatty acid utilization in liver and muscle during lactation in order to spare fatty acids for the production of milk triacylglycerols, an effect which is mediated by a down-regulation of peroxisome proliferator-activated receptor α (PPARα). The present study was performed to investigate whether similar fatty acid sparing effects are developing in lactating sows. We considered PPARα and its target genes involved in fatty acid utilization in biopsy samples from muscle and adipose tissue of lactating compared to non-lactating sows. In muscle, PPARα target genes involved in fatty acid utilization were up-regulated during lactation indicating that the fatty acid utilization in muscle was increased. Activation of PPARα was probably due to increased concentrations of non-esterified fatty acids in plasma observed in the lactating sows. In contrast to muscle, PPARα and its target genes involved in β-oxidation in white adipose tissue were down-regulated in early lactation. Overall, the present study shows that sows, unlike rats, are not able to reduce the fatty acid utilization in muscle in order to spare fatty acids for milk production. However, fatty acid oxidation in adipose tissue is lowered during early lactation, an effect that might be helpful to conserve fatty acids released from adipose tissue for the delivery into other tissues, including mammary gland, via the blood. 相似文献
96.
97.
The DNA translocase RAD5A acts independently of the other main DNA repair pathways,and requires both its ATPase and RING domain for activity in Arabidopsis thaliana 下载免费PDF全文
Tobias Klemm Anja Mannuß Daniela Kobbe Alexander Knoll Oliver Trapp Annika Dorn Holger Puchta 《The Plant journal : for cell and molecular biology》2017,91(4):725-740
Multiple pathways exist to repair DNA damage induced by methylating and crosslinking agents in Arabidopsis thaliana. The SWI2/SNF2 translocase RAD5A, the functional homolog of budding yeast Rad5 that is required for the error‐free branch of post‐replicative repair, plays a surprisingly prominent role in the repair of both kinds of lesions in Arabidopsis. Here we show that both the ATPase domain and the ubiquitination function of the RING domain of the Arabidopsis protein are essential for the cellular response to different forms of DNA damage. To define the exact role of RAD5A within the complex network of DNA repair pathways, we crossed the rad5a mutant line with mutants of different known repair factors of Arabidopsis. We had previously shown that RAD5A acts independently of two main pathways of replication‐associated DNA repair defined by the helicase RECQ4A and the endonuclease MUS81. The enhanced sensitivity of all double mutants tested in this study indicates that the repair of damaged DNA by RAD5A also occurs independently of nucleotide excision repair (AtRAD1), single‐strand break repair (AtPARP1), as well as microhomology‐mediated double‐strand break repair (AtTEB). Moreover, RAD5A can partially complement for a deficient AtATM‐mediated DNA damage response in plants, as the double mutant shows phenotypic growth defects. 相似文献
98.
The metalloprotease SepA governs processing of accumulation‐associated protein and shapes intercellular adhesive surface properties in Staphylococcus epidermidis 下载免费PDF全文
Alexandra E. Paharik Marta Kotasinska Anna Both Tra‐My N. Hoang Henning Büttner Paroma Roy Paul D. Fey Alexander R. Horswill Holger Rohde 《Molecular microbiology》2017,103(5):860-874
The otherwise harmless skin inhabitant Staphylococcus epidermidis is a major cause of healthcare‐associated medical device infections. The species' selective pathogenic potential depends on its production of surface adherent biofilms. The Cell wall‐anchored protein Aap promotes biofilm formation in S. epidermidis, independently from the polysaccharide intercellular adhesin PIA. Aap requires proteolytic cleavage to act as an intercellular adhesin. Whether and which staphylococcal proteases account for Aap processing is yet unknown. Here, evidence is provided that in PIA‐negative S. epidermidis 1457Δica, the metalloprotease SepA is required for Aap‐dependent S. epidermidis biofilm formation in static and dynamic biofilm models. qRT‐PCR and protease activity assays demonstrated that under standard growth conditions, sepA is repressed by the global regulator SarA. Inactivation of sarA increased SepA production, and in turn augmented biofilm formation. Genetic and biochemical analyses demonstrated that SepA‐related induction of biofilm accumulation resulted from enhanced Aap processing. Studies using recombinant proteins demonstrated that SepA is able to cleave the A domain of Aap at residue 335 and between the A and B domains at residue 601. This study identifies the mechanism behind Aap‐mediated biofilm maturation, and also demonstrates a novel role for a secreted staphylococcal protease as a requirement for the development of a biofilm. 相似文献
99.
Miehlke S Krasz S Schneider-Brachert W Kuhlisch E Berning M Madisch A Laass MW Neumeyer M Jebens C Zekorn C Knoth H Vieth M Stolte M Lehn N Morgner A 《Helicobacter》2011,16(6):420-426
Background: Triple therapy with a proton pump inhibitor, moxifloxacin, and amoxicillin has been proven effective in first‐line treatment of Helicobacter pylori infection. Aim: To explore 1, the value of triple therapy with esomeprazole, moxifloxacin, and amoxicillin in second‐line or rescue treatment of Caucasian patients and 2, the impact of treatment duration on eradication success. Methods: H. pylori‐infected patients with at least one previous treatment failure were randomized to oral esomeprazole 20 mg b.i.d., moxifloxacin 400 mg o.d., and amoxicillin 1000 mg b.i.d. for either 7 (EMA‐7) or 14 days (EMA‐14). Eradication was confirmed by 13C urea breath test. Antimicrobial susceptibility testing was performed in all patients at baseline and in patients who failed treatment. Results: Eighty patients were randomized, and 60% had ≥2 previous treatment failures. Pretreatment resistance against clarithromycin and metronidazole was found in 70.5 and 61.5% of cases, respectively. The intention‐to‐treat eradication rate was significantly higher after EMA‐14 compared with EMA‐7 (95.0 vs 78.9%, p = .036). No independent risk factor for treatment failure could be identified. There were no serious adverse events. Five of the EMA‐14 patients (12.5%) compared with none of the EMA‐7 patients discontinued prematurely because of adverse events (p = .031). Post‐treatment resistance against moxifloxacin was found in one of seven patients with isolated organisms (14.3%). Conclusion: Second‐line/rescue H. pylori eradication therapy with esomeprazole, moxifloxacin, and amoxicillin is very effective and well tolerated. Fourteen days of treatment significantly increase the eradication rate but also the rate of adverse events. 相似文献
100.
Beck-Speier I Dayal N Karg E Maier KL Schumann G Schulz H Semmler M Takenaka S Stettmaier K Bors W Ghio A Samet JM Heyder J 《Free radical biology & medicine》2005,38(8):1080-1092
In ambient aerosols, ultrafine particles (UFP) and their agglomerates are considered to be major factors contributing to adverse health effects. Reactivity of agglomerated UFP of elemental carbon (EC), Printex 90, Printex G, and diesel exhaust particles (DEP) was evaluated by the capacity of particles to oxidize methionine in a cell-free in vitro system for determination of their innate oxidative potential and by alveolar macrophages (AMs) to determine production of arachidonic acid (AA), including formation of prostaglandin E2 (PGE2), leukotriene B4 (LTB4), reactive oxygen species (ROS), and oxidative stress marker 8-isoprostane. EC exhibiting high oxidative potential induced generation of AA, PGE2, LTB4, and 8-isoprostane in canine and human AMs. Printex 90, Printex G, and DEP, showing low oxidative capacity, still induced formation of AA and PGE2, but not that of LTB4 or 8-isoprostane. Aging of EC lowered oxidative potential while still inducing production of AA and PGE2 but not that of LTB4 and 8-isoprostane. Cellular ROS production was stimulated by all particles independent of oxidative potential. Particle-induced formation of AA metabolites and ROS was dependent on mitogen-activated protein kinase kinase 1 activation of cytosolic phospholipase A2 (cPLA2) as shown by inhibitor studies. In conclusion, cPLA2, PGE2, and ROS formation was activated by all particle types, whereas LTB4 production and 8-isoprostane were strongly dependent on particles' oxidative potential. Physical and chemical parameters of particle surface correlated with oxidative potential and stimulation of AM PGE2 and 8-isoprostane production. 相似文献