全文获取类型
收费全文 | 27530篇 |
免费 | 2420篇 |
国内免费 | 2745篇 |
专业分类
32695篇 |
出版年
2024年 | 53篇 |
2023年 | 286篇 |
2022年 | 628篇 |
2021年 | 1012篇 |
2020年 | 795篇 |
2019年 | 908篇 |
2018年 | 938篇 |
2017年 | 746篇 |
2016年 | 973篇 |
2015年 | 1597篇 |
2014年 | 1794篇 |
2013年 | 2047篇 |
2012年 | 2532篇 |
2011年 | 2220篇 |
2010年 | 1497篇 |
2009年 | 1397篇 |
2008年 | 1697篇 |
2007年 | 1543篇 |
2006年 | 1407篇 |
2005年 | 1305篇 |
2004年 | 1174篇 |
2003年 | 1079篇 |
2002年 | 899篇 |
2001年 | 672篇 |
2000年 | 544篇 |
1999年 | 531篇 |
1998年 | 335篇 |
1997年 | 256篇 |
1996年 | 228篇 |
1995年 | 211篇 |
1994年 | 184篇 |
1993年 | 134篇 |
1992年 | 177篇 |
1991年 | 132篇 |
1990年 | 113篇 |
1989年 | 114篇 |
1988年 | 78篇 |
1987年 | 85篇 |
1986年 | 72篇 |
1985年 | 48篇 |
1984年 | 25篇 |
1983年 | 43篇 |
1982年 | 23篇 |
1981年 | 18篇 |
1979年 | 18篇 |
1978年 | 14篇 |
1977年 | 13篇 |
1975年 | 10篇 |
1972年 | 12篇 |
1970年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Li Jing-Wei Hong Jian-Shiung Chou Wei-Ting Huang Ding-Jie Chen Kuan-Ren 《Plasmonics (Norwell, Mass.)》2018,13(6):2249-2254
Plasmonics - The funneling profile of enhanced light transmission through a subwavelength slit in a perfect electric conductor is studied with finite-difference time-domain simulation. From the... 相似文献
52.
Background
Several case-control studies have been performed to examine the association of genetic variants in lysyl oxidase (LOX) with keratoconus. However, the results remained inconclusive and great heterogeneity might exist across populations.Method
A comprehensive literature search for studies that published up to June 25, 2015 was performed. Summary odds ratios (OR) and 95% confidence intervals (CI) of each single nucleotide polymorphism (SNP) were estimated with fixed effects model when I 2<50% in the test for heterogeneity or random effects model when I 2>50%. Publication bias was evaluated using funnel plots and Egger’s test.Results
A total of four studies including 1,467 keratoconus cases and 4,490 controls were involved in this meta-analysis. SNPs rs2956540 and rs10519694 showed significant association with keratoconus, with ORs of 0.71 (95% CI: 0.63–0.80, P = 1.43E-08) and 0.77 (95% CI: 0.61–0.97, P = 0.026), respectively. In contrast, our study lacked sufficient evidences to support the association of rs1800449/rs2288393 with keratoconus across populations.Conclusion
This meta-analysis suggested that two LOX variants, rs2956540 and rs10519694, may affect individual susceptibility to keratoconus, while distinct heterogeneity existed within this locus. Larger-scale and multi-ethnic genetic studies on keratoconus are required to further validate the results. 相似文献53.
54.
55.
As studies on vehicular ad hoc networks have been conducted actively in recent years, convenient and reliable services can be provided to vehicles through traffic information, surrounding information, and file sharing. To provide services for multiple requests, road side units (RSUs) should receive requests from vehicles and provide a scheduling scheme for data transfer according to priority. In this paper, we propose a new scheduling scheme by which multiple RSUs are connected through wired networks and data is transferred through the collaboration of RSUs. The proposed scheme transfers safety and non-safety data by employing a collaborative strategy of multiple RSUs as well as reducing the deadline miss ratio and average response time. When safety data is generated, data is transferred from the previous RSU in advance, while priority is assigned considering the deadline and reception rate. Since non-safety data is an on-demand data processed by user requests, the proposed scheme provides a method that reduces the deadline miss ratio upon loads generated in RSUs. To prove the superiority of the proposed scheme, we perform a performance evaluation in which the number and velocities of vehicles were changed. It is shown through the performance evaluation that the proposed scheme has better deadline miss ratios and faster response time than the existing schemes. 相似文献
56.
Luo Q Upadhya R Zhang H Madrid-Aliste C Nieves E Kim K Angeletti RH Weiss LM 《Microbes and infection / Institut Pasteur》2011,13(14-15):1199-1210
Glycoproteins are involved in many important molecular recognition processes including invasion, adhesion, differentiation, and development. To identify the glycoproteins of Toxoplasma gondii, a proteomic analysis was undertaken. T. gondii proteins were prepared and fractioned using lectin affinity chromatography. The proteins in each fraction were then separated using SDS-PAGE and identified by tryptic in gel digestion followed by tandem mass spectrometry. Utilizing these methods 132 proteins were identified. Among the identified proteins were 17 surface proteins, 9 microneme proteins, 15 rhoptry proteins, 11 heat shock proteins (HSP), and 32 hypothetical proteins. Several proteins had 1–5 transmembrane domains (TMD) with some being as large as 608.3 kDa. Both lectin-fluorescence labeling and lectin blotting were employed to confirm the presence of carbohydrates on the surface or cytoplasm of T. gondii parasites. PCR demonstrated that selected hypothetical proteins were expressed in T. gondii tachyzoites. This data provides a large-scale analysis of the T. gondii glycoproteome. Studies of the function of glycosylation of these proteins may help elucidate mechanism(s) involved in invasion improving drug therapy as well as identify glycoproteins that may prove to be useful as vaccine candidates. 相似文献
57.
Zhi Qi Hong Lu Lin Li Xiaojuan Li Shuwen Liu 《Biochemical and biophysical research communications》2010,398(3):506-1133
HIV-1 gp41 prehairpin fusion intermediate (PFI) composed of three N-terminal heptad repeats (NHR) plays a crucial role in viral fusion and entry and represents an attractive target for anti-HIV therapeutics (e.g., enfuvirtide) and vaccines. In present study, we constructed and expressed two recombinant gp41 PFI mimetics, designated N46Fd and N46FdFc. N46Fd consists of N46 (residues 536-581) in gp41 NHR and foldon (Fd), a trimerization motif. N46FdFc is composed of N46Fd fused with human IgG Fc fragment as an immunoenhancer. We immunized mice with N46 peptide, N46Fd and N46FdFc, respectively, and found that only N46FdFc elicited neutralizing antibody response in mice against infection by HIV-1 strains IIIB (clade B, X4), 92US657 (clade B, R5), and 94UG103 (clade A, X4R5). Anti-N46FdFc antibodies inhibited PIE7 binding to PFI, blocked gp41 six-helix bundle formation, and suppressed HIV-1 mediated cell-cell fusion. These findings provide an important clue for developing recombinant gp41 PFI mimetics-based HIV vaccines. 相似文献
58.
60.
Did RNA editing in plant organellar genomes originate under natural selection or through genetic drift? 总被引:1,自引:0,他引:1