全文获取类型
收费全文 | 60293篇 |
免费 | 5077篇 |
国内免费 | 37篇 |
出版年
2023年 | 279篇 |
2022年 | 317篇 |
2021年 | 1162篇 |
2020年 | 871篇 |
2019年 | 952篇 |
2018年 | 1358篇 |
2017年 | 1151篇 |
2016年 | 1862篇 |
2015年 | 2645篇 |
2014年 | 2635篇 |
2013年 | 3275篇 |
2012年 | 3947篇 |
2011年 | 3607篇 |
2010年 | 2199篇 |
2009年 | 2118篇 |
2008年 | 2622篇 |
2007年 | 2530篇 |
2006年 | 2367篇 |
2005年 | 2649篇 |
2004年 | 2618篇 |
2003年 | 2170篇 |
2002年 | 1781篇 |
2001年 | 1534篇 |
2000年 | 1466篇 |
1999年 | 1340篇 |
1998年 | 633篇 |
1997年 | 604篇 |
1996年 | 616篇 |
1995年 | 494篇 |
1994年 | 506篇 |
1993年 | 473篇 |
1992年 | 967篇 |
1991年 | 870篇 |
1990年 | 793篇 |
1989年 | 792篇 |
1988年 | 789篇 |
1987年 | 704篇 |
1986年 | 677篇 |
1985年 | 645篇 |
1984年 | 596篇 |
1983年 | 459篇 |
1982年 | 357篇 |
1981年 | 353篇 |
1980年 | 324篇 |
1979年 | 446篇 |
1978年 | 377篇 |
1977年 | 304篇 |
1975年 | 307篇 |
1974年 | 308篇 |
1973年 | 307篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
991.
Inclusion bodies were previously found in Papanicolaou smears of patients infected by the human papillomavirus (HPV). To ascertain their origin, 12 biopsies from patients with colposcopic evidence of papillomatous lesions were studied by cytology and electron microscopy. In several instances, koilocytotic atypias and electron-dense masses included within epithelial cells were observed. Some of these epithelial cells appeared to be surrounded by other cells in a sort of concentric arrangement. The electron-dense masses were composed of intermediate filaments, vacuoles and electron-dense material. They seemed to be dyskeratotic cells. They can be compared with apoptotic bodies and may be related to a disturbance of the involucrin expression caused by the HPV infection. 相似文献
992.
Survival of patients with malignancy-associated effusions 总被引:1,自引:0,他引:1
For a better understanding of the prognosis after the onset of a malignancy-associated effusion in patients known or subsequently shown to have cancer, survival time was compared with the findings and the date of the first cytologic diagnosis of an effusion. The number of patients studied was 254; 171 had a pleural and 83 a peritoneal effusion. The average survival time was 25.5 weeks, which was about equal for both sites of effusions. After two years, only 6% of all patients were alive. When the cytologic diagnosis of the effusion was "malignant," only 4% survived after two years; when the cytologic diagnosis was "suspicious for malignancy" and "nonmalignant," these figures were 5% and 7%, respectively. This indicates that a cytologic diagnosis of benign or nonmalignant is not a good indicator of a better prognosis in cancer patients for whom benign causes of the effusion have been excluded. There appeared to be a prognostic relationship between the length of the interval from the initial diagnosis of cancer to the time of examination of the first sample of the effusion: a longer interval was correlated with a better survival. When survival time was viewed in relation to therapy, patients whose pleural effusions were only treated by aspiration were found to have a particularly short average survival (13.9 weeks). 相似文献
993.
The molecular basis for Duchenne versus Becker muscular dystrophy: Correlation of severity with type of deletion 总被引:82,自引:23,他引:59 下载免费PDF全文
M. Koenig A. H. Beggs M. Moyer S. Scherpf K. Heindrich T. Bettecken G. Meng C. R. Müller M. Lindl?f H. Kaariainen A. de la Chapelle A. Kiuru M.-L. Savontaus H. Gilgenkrantz D. Récan J. Chelly J.-C. Kaplan A. E. Covone N. Archidiacono G. Romeo S. Liechti-Gallati V. Schneider S. Braga H. Moser B. T. Darras P. Murphy U. Francke J. D. Chen G. Morgan M. Denton C. R. Greenberg K. Wrogemann L. A. J. Blonden H. M. B. van Paassen G. J. B. van Ommen L. M. Kunkel 《American journal of human genetics》1989,45(4):498-506
About 60% of both Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) is due to deletions of the dystrophin gene. For cases with a deletion mutation, the "reading frame" hypothesis predicts that BMD patients produce a semifunctional, internally deleted dystrophin protein, whereas DMD patients produce a severely truncated protein that would be unstable. To test the validity of this theory, we analyzed 258 independent deletions at the DMD/BMD locus. The correlation between phenotype and type of deletion mutation is in agreement with the "reading frame" theory in 92% of cases and is of diagnostic and prognostic significance. The distribution and frequency of deletions spanning the entire locus suggests that many "in-frame" deletions of the dystrophin gene are not detected because the individuals bearing them are either asymptomatic or exhibit non-DMD/non-BMD clinical features. 相似文献
994.
995.
996.
Dr. María Cristina Maldonado Ana María Strasser de Saad Danley Callieri 《Current microbiology》1989,18(5):303-306
Several recent reports have described large numbers of monoclonal antibodies that cross-react with toxins A and B ofClostridium difficile; this suggests that the toxins share major epitopes. Our results show that monoclonal antibodies (MAb) against other antigens bind nonspecifically to both toxins. Therefore, we believe that the cross-reacting MAb bind by this manner and not by a true immune reaction. 相似文献
997.
A. C. Passaquin G. Coupin W. A. Schreier P. Poindron R. A. Cole J. de Vellis 《Neurochemical research》1989,14(10):987-993
We investigated the effect of rat interferon-/ (IFN) on the expression of glycerol phosphate dehydrogenase (E.C.1.1.1.8; GPDH), in both C6 cells and pure cultures of oligodendrocytes. IFNs are naturally produced inhibitors of cell growth that can also affect differentiated cell functions. GPDH is a biochemical marker for oligodendrocytes and is known to be developmentally regulated and steroid inducible. GPDH activity is induced by hydrocortisone (HC) 3.5 fold in C6 cells and 5 fold in oligodendrocytes compared to untreated cultures. A pretreatment of these cells with 75 U/ml of rat IFN-/ resulted in an inhibition of the HC induction of GPDH enzymatic activity by 50% and 40% in C6 cells and oligodendrocytes respectively. We also found that IFN impaired the accumulation of GPDH mRNA in both cell types. These results demonstrate that IFNs are capable of modifying the cellular response to hormones in cells of neuroepithelial origin, and suggest the possibility that IFNs may be able to influence the development and function of the brain.Special issue dedicated to Dr. Paola S. Timiras 相似文献
998.
999.
G L van Rens J M Raats H P Driessen M Oldenburg J T Wijnen P M Khan W W de Jong H Bloemendal 《Gene》1989,78(2):225-233
The organization of a number of crystallin genes has already been resolved. One of the remaining genes of which the structure was hitherto unknown is the gamma s gene (formerly beta s). We determined the complete sequence of the bovine gamma s-crystallin-coding gene, apart from the middle region of the first intron. Since it contains three exons and two introns, we conclude that the former beta s, also at the gene level is gamma-crystallin-like. However, it is located on chromosome 3, in contrast to other gamma genes which occur in tandem on the human chromosome 2. 相似文献
1000.
The role of indole-3-butyric acid (IBA) in adventitious root formation was studied by analyzing the uptake and subsequent metabolism of IBA in shoots of M.26 apple (Malus pumila Mill.) rootstock grown in vitro. Roots were induced by exposing shoots to 4 M IBA and [3H]IBA for 5 days in the dark and then transferring them to plant growth regulator (PGR)-free medium in the light until roots formed. Approximately 50% of the total radioactivity applied was taken up from the agar medium by the shoots during the 5-day incubation period in IBA. Indole-3-butyric acid metabolism was studied by extraction and high-performance liquid chromatographic (HPLC) separation of [3H]IBA and metabolites from the basal sections of treated shoots. The major [3H]IBA metabolite co-eluted with authentic [14C]indole-3-acetic acid (IAA) suggesting that IBA was converted to IAA in the shoots. The proportion of newly synthesized IAA present as conjugates was higher at the end of the 5-day IBA treatment period than after 13 days in PGR-free medium. There appeared to be no conjugation of IBA at any time. 相似文献