全文获取类型
收费全文 | 10491篇 |
免费 | 784篇 |
国内免费 | 4篇 |
出版年
2023年 | 56篇 |
2022年 | 58篇 |
2021年 | 223篇 |
2020年 | 183篇 |
2019年 | 224篇 |
2018年 | 288篇 |
2017年 | 236篇 |
2016年 | 354篇 |
2015年 | 592篇 |
2014年 | 602篇 |
2013年 | 727篇 |
2012年 | 896篇 |
2011年 | 834篇 |
2010年 | 545篇 |
2009年 | 497篇 |
2008年 | 608篇 |
2007年 | 575篇 |
2006年 | 568篇 |
2005年 | 510篇 |
2004年 | 470篇 |
2003年 | 396篇 |
2002年 | 367篇 |
2001年 | 106篇 |
2000年 | 78篇 |
1999年 | 102篇 |
1998年 | 128篇 |
1997年 | 104篇 |
1996年 | 72篇 |
1995年 | 63篇 |
1994年 | 71篇 |
1993年 | 68篇 |
1992年 | 50篇 |
1991年 | 55篇 |
1990年 | 67篇 |
1989年 | 49篇 |
1988年 | 41篇 |
1987年 | 35篇 |
1986年 | 28篇 |
1985年 | 37篇 |
1984年 | 41篇 |
1983年 | 28篇 |
1982年 | 29篇 |
1981年 | 30篇 |
1980年 | 20篇 |
1979年 | 17篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 14篇 |
1975年 | 16篇 |
1974年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
992.
993.
Pitanguy I Torres E Salgado F Pires Viana GA 《Plastic and reconstructive surgery》2005,115(3):729-34; discussion 735
Breast cancer is the tumor with the highest prevalence and incidence in women. Reduction mammaplasty is one of the most common procedures performed in Brazil by the plastic surgeon, and it is not uncommon for the surgeon to find a breast tumor during the operation or afterward, when the histopathological report is received. In this study, 2488 patient files were reviewed retrospectively. All patients had undergone reduction mammaplasty at the senior author's private clinic (the Ivo Pitanguy Clinic) between January of 1957 and December of 2002. Resected breast tissue was examined histopathologically. The objective of this study was to verify the occurrence of breast carcinoma found accidentally postoperatively. The senior author's team performed all of the operations and the same pathologist performed every histopathological examination. The histopathological test results were divided into two groups: benign lesions and tumors. The highest frequency of breast pathology was benign lesions, and of them, 80.8 percent involved fibrocystic changes and fibroadiposity. The tumor group was subdivided into benign tumors and malignant tumors. Among the benign tumors, fibroadenoma was the one most common, in 2.2 percent. The frequency of malignant tumors was 0.5 percent of all patients. Most of the histopathological lesions were found in patients between 30 and 50 years of age. A reduced number of patients had no lesions (3.7 percent). Lack of a pathological investigation or a cursory or hurried examination of any mammary tissue by the pathologist may overlook important lesions. In the analysis of these statistics, the concept of normal breast tissue was questioned. 相似文献
994.
Martín I Dopico B Muñoz FJ Esteban R Oomen RJ Driouich A Vincken JP Visser R Labrador E 《Plant & cell physiology》2005,46(10):1613-1622
We report the generation of Solanum tuberosum transformants expressing Cicer arietinum betaIII-Gal. betaIII-Gal is a beta-galactosidase able to degrade cell wall pectins during cell wall loosening that occurs prior to cell elongation. cDNA corresponding to the gene encoding this protein was identified among several chickpea beta-galactosidase cDNAs, and named CanBGal-3. CanBGal-3 cDNA was expressed in potato under the control of the granule-bound starch synthase promoter. Three betaIII-Gal transformants with varying levels of expression were chosen for further analysis. The transgenic plants displayed no significant altered phenotype compared to the wild type. However, beta-galactanase and beta-galactosidase activities were increased in the transgenic tuber cell walls and this affected the potato tuber pectins. A reduction in the galactosyl content of up to 50% compared to the wild type was observed in the most extreme transformant, indicating a reduction of 1,4-beta-galactan side-chains, as revealed by analysis with LM5 specific antibodies. Our results confirm the notion that the pectin-degrading activity of chickpea betaIII-Gal reported in vitro also occurs in vivo and in other plants, and confirm the involvement of betaIII-Gal in the cell wall autolysis process. An increase in the homogalacturonan content of transgenic tuber cell walls was also observed by Fourier transform infrared spectroscopy (FTIR) analysis. 相似文献
995.
996.
Laguarda-Figueras A Gutiérrez-Castro A Solís-Marín FA Durán-González A Torres-Vega J 《Revista de biología tropical》2005,53(Z3):69-108
The echinoid fauna of the Gulf of Mexico collected during three research cruises (20-1260 m depth) was surveyed from samples were taken at 43 stations. A total of 190 individuals were identified (eight orders, 11 families, 15 genera and 18 species). Six species are new records for the Gulf of Mexico: Stylocidaris lineata, Phormosoma placenta placenta, Plesiodiadema antillarum, Plethotaenia spatangoides, Brissopsis atlantica and Hypselaster limicolus. This adds to the little information available on the echinoid fauna of Tamaulipas, Veracruz, Tabasco, Campeche and Yucatan states in Mexico. 相似文献
997.
This is an updated taxonomic catalogue of neritic-benthonic Echinodermata (Asteroidea and Ophiuroidea) from Cuba, that includes locality, range, habitat and depth where each species is found. The species list is based on the collections of the Oceanology Institute; Havana; the "Felipe Poey" Museum (Havana University) and the National Museum of Natural History, Smithsonian Institution, Washington D.C. Specimens for those collections were captured by a variety of field techniques, narcotized with Cloral hydrate, fixed in formalin and stored in 70-80% alcohol. A total of 75 species have been identified from Cuban waters: Asteroidea (20 species) and Ophiuroidea (55 species). 相似文献
998.
Barcelos IS Ferreira MS Moura LP Biondi GF Costa-Cruz JM 《Memórias do Instituto Oswaldo Cruz》2005,100(4):427-429
Paired samples of cerebrospinal fluid (CSF) and serum of 30 patients--10 with active, 10 with inactive neurocysticercosis (NCC), and 10 control subjects--were evaluated by enzyme-linked immunosorbent assay (ELISA) using two Taenia crassiceps metacestode extracts as antigen in order to detect IgG antibodies. In active NCC, high levels of IgG were detected (p < 0.05). The CSF samples showed 80% (CI 72-88) of reactivity in the saline extract (S) and 90% (CI 84-95) in sodium dodecyl sulphate (SDS) and the serum samples were reactive in 90% (CI 84-95) and 100% (CI 98-100) in the S and SDS antigenic extracts, respectively. The use of the paired samples of CSF and serum in active NCC showed equivalent results suggesting that the serum samples could be used as a screening in those patients whose CSF puncture is counter-indicated. 相似文献
999.
Adaptive evolution of the insulin gene in caviomorph rodents 总被引:1,自引:0,他引:1
Insulin is a conservative molecule among mammals, maintaining both its structure and function. Rodents that belong to the Suborder Hystricognathi represent an exception, having a very divergent molecule with unusual physiological properties. In this work, we analyzed the evolutionary pattern of the insulin gene in caviomorph rodents (South American hystricomorph rodents). We found that these rodents have higher rates of nonsynonymous:synonymous substitutions (d(N)/d(S)) than nonhystricomorph rodents and that values are heterogeneous inside the group. We estimated codons under positive selection, specifically the second binding site (A13 and B17) and others related with hexamerization (B18, B20, and B22). In the monomer structure, all selected sites formed a single patch around the second binding site. In the hexamer structure, these amino acids were grouped into three major patches. In this structure, contacts between B chains involved all selected sites (except B18), and between faces in the center of the molecule, all contacts were among selected sites. While there is no clear hypothesis regarding the cause of this drastic change, experimental evidence does show that this group of rodents has some peculiarities in growth function, and, whether coincidental or not, these changes appeared together with important changes in life-history traits. 相似文献
1000.