全文获取类型
收费全文 | 311546篇 |
免费 | 283113篇 |
国内免费 | 39755篇 |
专业分类
耳鼻咽喉 | 3073篇 |
儿科学 | 5400篇 |
妇产科学 | 2558篇 |
基础医学 | 91553篇 |
口腔科学 | 3754篇 |
临床医学 | 66692篇 |
内科学 | 98524篇 |
皮肤病学 | 5496篇 |
神经病学 | 22936篇 |
特种医学 | 11318篇 |
外科学 | 46558篇 |
综合类 | 71830篇 |
现状与发展 | 16篇 |
一般理论 | 6篇 |
预防医学 | 49637篇 |
眼科学 | 19115篇 |
药学 | 66357篇 |
120篇 | |
中国医学 | 52413篇 |
肿瘤学 | 17058篇 |
出版年
2022年 | 5409篇 |
2021年 | 5955篇 |
2020年 | 8346篇 |
2019年 | 13971篇 |
2018年 | 14612篇 |
2017年 | 15908篇 |
2016年 | 13949篇 |
2015年 | 15136篇 |
2014年 | 15804篇 |
2013年 | 16807篇 |
2012年 | 18691篇 |
2011年 | 20646篇 |
2010年 | 22859篇 |
2009年 | 30287篇 |
2008年 | 17656篇 |
2007年 | 13885篇 |
2006年 | 12709篇 |
2005年 | 11670篇 |
2004年 | 12516篇 |
2003年 | 11106篇 |
2002年 | 11072篇 |
2001年 | 12824篇 |
2000年 | 8170篇 |
1999年 | 12562篇 |
1998年 | 13737篇 |
1997年 | 13642篇 |
1996年 | 14714篇 |
1995年 | 14934篇 |
1994年 | 14691篇 |
1993年 | 13467篇 |
1992年 | 12751篇 |
1991年 | 12137篇 |
1990年 | 11106篇 |
1989年 | 10964篇 |
1988年 | 10529篇 |
1987年 | 9878篇 |
1986年 | 9394篇 |
1985年 | 8471篇 |
1984年 | 6552篇 |
1983年 | 6565篇 |
1982年 | 7613篇 |
1981年 | 7147篇 |
1980年 | 6819篇 |
1979年 | 6667篇 |
1978年 | 5846篇 |
1977年 | 6145篇 |
1976年 | 5767篇 |
1975年 | 5500篇 |
1974年 | 5057篇 |
1973年 | 4771篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
nm23-H1基因转染对人胆管癌细胞系QBC939体外浸润能力的影响 总被引:1,自引:0,他引:1
目的:探讨nm23-H1基因转染对人胆管癌细胞系QBC939体外浸润能力的影响。方法:将含有全长nm23-H1 cDNA的真核表达载体通过脂腩体法转染人胆管癌细胞系。结果:转染成功的QBC939细胞,其nm23-Hl基因的mRNA、蛋白表达明显增加,转染nm23-H1基因的胆管癌细胞体外浸润能力下降,穿越matrigel的细胞数明显低于亲本QBC939细胞,代表浸润能力的IV型胶原酶(MMP-9)分泌量下降。结论:nm23-Hl基因可以抑制胆管癌细胞的体外浸润能力。 相似文献
142.
In der Behandlung von Frakturen spielt die Analgesie eine wesentliche Rolle. Es stellt sich daher die Frage, ob in der Klinik h?ufig eingesetzte Analgetika wie Tramadol oder Diclofenac negative Wirkungen auf die Knochenbruchheilung haben. 相似文献
143.
144.
145.
146.
H. Nilsson J. Johansson K. Svanberg S. Svanberg G. Jori E. Reddi A. Segalla D. Gust A. L. Moore T. A. Moore 《British journal of cancer》1997,76(3):355-364
The biodistribution of two recently developed tumour markers, trimethylated (CP(Me)3) and trimethoxylated (CP(OMe)3) carotenoporphyrin, was investigated by means of laser-induced fluorescence (LIF) after i.v. injection into 38 tumour-bearing (MS-2 fibrosarcoma) female Balb/c mice. At 3, 24, 48 or 96 h after administration, the carotenoporphyrin fluorescence was measured in tumoral and peritumoral tissue, as well as in the abdominal, thoracic and cranial cavities. The fluorescence was induced by a nitrogen laser-pumped dye laser, emitting light at 425 nm, and analysed by a polychromator equipped with an image-intensified CCD camera. The fluorescence was evaluated at 490, 655 and 720 nm: the second and third wavelengths represent the carotenoporphyrin (CP)-related peaks, whereas the first one is close to the peak of the tissue autofluorescence. The tumour and the liver were the two tissue types showing the strongest carotenoporphyrin-related fluorescence, whereas the cerebral cortex and muscle consistently exhibited weak substance-related fluorescence. In most tissue types, the fluorescence intensities decreased over time. A few exceptions were observed, notably the liver, in which the intensity remained remarkably constant over the time period investigated. 相似文献
147.
Summary— KR31080 (2-butyl-5-methyl-6-(1-oxopyridin-2-yl)-3-[[2'-(1H-tetrazol-5-yl) biphenyl-4-yl]methyl]-3H-imidazo[4,5-b] pyridine) is a potent inhibitor of angiotensin type 1 (AT1 ) receptors in rabbit aorta and human recombinant AT1 receptors. In the isolated rabbit thoracic aorta, KR31080 caused a nonparallel shift to the right of the concentration-response curves to angiotensin II (All) with decreased maximal response (pD'2 = 10.1 ± 0.1), but had no effect on the contractile response induced by norepinephrine. KR31080 inhibited specific [125 I]AII binding to rabbit aortic membranes (AT, receptors) and [125 I][Sar1 , Ile8 ]AII binding to human recombinant AT1 receptors in a concentration-dependent manner with IC50 values of 0.84 ± 0.08 nM and 1.92 ± 0.15 nM, respectively, but did not inhibit specific [125 I)AII binding to bovine cerebellum membranes (ÀT2 receptors). In the Scatchard analysis, KR31080 interacted with rabbit aortic AT1 receptors in a competitive manner, similar to losartan. These results demonstrate that KR31080 is a potent and AT1 selective angiotensin receptor antagonist which exerts a competitive antagonism in the [125 I]AII binding assay and insurmountable AT1 receptor antagonism in the functional study. 相似文献
148.
149.
The 2.0-Å resolution crystal structure of a trimeric antibody fragment with noncognate VH–VL domain pairs shows a rearrangement of VH CDR3 下载免费PDF全文
Xue Y. Pei Philipp Holliger Alexey G. Murzin Roger L. Williams 《Proceedings of the National Academy of Sciences of the United States of America》1997,94(18):9637-9642
The 2.0-Å resolution x-ray crystal structure of a novel trimeric antibody fragment, a “triabody,” has been determined. The trimer is made up of polypeptides constructed in a manner identical to that previously described for some “diabodies”: a VL domain directly fused to the C terminus of a VH domain—i.e., without any linker sequence. The trimer has three Fv heads with the polypeptides arranged in a cyclic, head-to-tail fashion. For the particular structure reported here, the polypeptide was constructed with a VH domain from one antibody fused to the VL domain from an unrelated antibody giving rise to “combinatorial” Fvs upon formation of the trimer. The structure shows that the exchange of the VL domain from antibody B1-8, a Vλ domain, with the VL domain from antibody NQ11, a Vκ domain, leads to a dramatic conformational change in the VH CDR3 loop of antibody B1-8. The magnitude of this change is similar to the largest of the conformational changes observed in antibody fragments in response to antigen binding. Combinatorial pairing of VH and VL domains constitutes a major component of antibody diversity. Conformationally flexible antigen-binding sites capable of adapting to the specific CDR3 loop context created upon VH–VL pairing may be employed by the immune system to maximize the structural diversity of the immune response. 相似文献
150.
Conditionally replicating luciferase reporter phages: improved sensitivity for rapid detection and assessment of drug susceptibility of Mycobacterium tuberculosis. 总被引:7,自引:1,他引:6 下载免费PDF全文
C Carrire P F Riska O Zimhony J Kriakov S Bardarov J Burns J Chan W R Jacobs Jr 《Journal of clinical microbiology》1997,35(12):3232-3239
TM4 is a lytic mycobacteriophage which infects mycobacteria of clinical importance. A luciferase reporter phage, phAE40, has been constructed from TM4 and was previously shown to be useful for the rapid detection and drug susceptibility testing of Mycobacterium tuberculosis. However, the lytic nature of the phage results in a loss of detectable light output and limits the sensitivity of detection. We describe several strategies aimed at improving the luciferase activity generated by TM4 luciferase phages, including (i) varying the position of the luciferase gene in the phage genome, (ii) isolating host-range mutants of the phage, and (iii) introducing temperature-sensitive mutations in the phage such that it will not replicate at the infecting temperature. Several new phages generated by these methods show increased intensity of luciferase production compared to the first-generation reporter phage phAE40, and one phage, phAE88, also demonstrates an enhanced duration of luciferase activity. This has allowed the detection of as few as 120 BCG cells and the determination of drug susceptibilities of M. tuberculosis in as little as 1 day. 相似文献