全文获取类型
收费全文 | 46600篇 |
免费 | 3312篇 |
国内免费 | 158篇 |
专业分类
耳鼻咽喉 | 337篇 |
儿科学 | 1501篇 |
妇产科学 | 1132篇 |
基础医学 | 5640篇 |
口腔科学 | 845篇 |
临床医学 | 4849篇 |
内科学 | 9495篇 |
皮肤病学 | 792篇 |
神经病学 | 4440篇 |
特种医学 | 1622篇 |
外科学 | 6914篇 |
综合类 | 755篇 |
一般理论 | 63篇 |
预防医学 | 3930篇 |
眼科学 | 1215篇 |
药学 | 3267篇 |
中国医学 | 45篇 |
肿瘤学 | 3228篇 |
出版年
2022年 | 301篇 |
2021年 | 699篇 |
2020年 | 422篇 |
2019年 | 735篇 |
2018年 | 860篇 |
2017年 | 684篇 |
2016年 | 685篇 |
2015年 | 880篇 |
2014年 | 1270篇 |
2013年 | 1915篇 |
2012年 | 2900篇 |
2011年 | 3108篇 |
2010年 | 1784篇 |
2009年 | 1607篇 |
2008年 | 2881篇 |
2007年 | 3102篇 |
2006年 | 3067篇 |
2005年 | 3119篇 |
2004年 | 2995篇 |
2003年 | 2777篇 |
2002年 | 2751篇 |
2001年 | 613篇 |
2000年 | 467篇 |
1999年 | 636篇 |
1998年 | 691篇 |
1997年 | 528篇 |
1996年 | 465篇 |
1995年 | 408篇 |
1994年 | 354篇 |
1993年 | 354篇 |
1992年 | 380篇 |
1991年 | 377篇 |
1990年 | 355篇 |
1989年 | 333篇 |
1988年 | 310篇 |
1987年 | 288篇 |
1986年 | 302篇 |
1985年 | 335篇 |
1984年 | 378篇 |
1983年 | 329篇 |
1982年 | 361篇 |
1981年 | 328篇 |
1980年 | 328篇 |
1979年 | 232篇 |
1978年 | 201篇 |
1977年 | 200篇 |
1976年 | 170篇 |
1975年 | 160篇 |
1974年 | 176篇 |
1973年 | 168篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Facundo Davaro Jacob Roberts Allison May Coleman McFerrin Sameer Siddiqui Zachary Hamilton 《Journal of robotic surgery》2020,14(3):447-454
Partial nephrectomy is the mainstay of treatment for localized kidney cancer. A proportion of patients are upstaged post-operatively to locally advanced di 相似文献
12.
13.
14.
15.
Genomes of some parasites contain dozens of alternative and highly diverged surface antigens, of which only a single one is expressed in any cell. Individual cells occasionally change expression of their surface antigen, allowing them to escape immune surveillance. These switches appear to occur in a partly random way, creating a diverse set of antigenic variants. In spite of this diversity, the parasitemia develops as a series of outbreaks, in which each outbreak is dominated by relatively few antigenic types. Host-specific immunity eventually clears the dominant antigenic types, and a new outbreak follows from antigenic types that have apparently been present all along at low frequency. This pattern of sequential dominance by different antigenic types remains unexplained. We review the five most prominent theories, which have developed mainly from studies of the protozoans Trypanosoma and Plasmodium, and the bacterial spirochete Borrelia. The most promising theories depend on some combination of mechanisms to create favored connectivity pathways through the matrix of transitions between variants. Favored pathways may arise from biased switches at the molecular level of gene expression or from biases imposed by immune selection. We illustrate the concept of connectivity pathways by reanalysis of data on transitions between variants from Borrelia hermsii. 相似文献
16.
Alex N. Bullock Julia Henckel Brian S. DeDecker Christopher M. Johnson Penka V. Nikolova Mark R. Proctor David P. Lane Alan R. Fersht 《Proceedings of the National Academy of Sciences of the United States of America》1997,94(26):14338-14342
Some 50% of human cancers are associated with mutations in the core domain of the tumor suppressor p53. Many mutations are thought just to destabilize the protein. To assess this and the possibility of rescue, we have set up a system to analyze the stability of the core domain and its mutants. The use of differential scanning calorimetry or spectroscopy to measure its melting temperature leads to irreversible denaturation and aggregation and so is useful as only a qualitative guide to stability. There are excellent two-state denaturation curves on the addition of urea that may be analyzed quantitatively. One Zn2+ ion remains tightly bound in the holo-form of p53 throughout the denaturation curve. The stability of wild type is 6.0 kcal (1 kcal = 4.18 kJ)/mol at 25°C and 9.8 kcal/mol at 10°C. The oncogenic mutants R175H, C242S, R248Q, R249S, and R273H are destabilized by 3.0, 2.9, 1.9, 1.9, and 0.4 kcal/mol, respectively. Under certain denaturing conditions, the wild-type domain forms an aggregate that is relatively highly fluorescent at 340 nm on excitation at 280 nm. The destabilized mutants give this fluorescence under milder denaturation conditions. 相似文献
17.
Juin Fok-Seang Linda C. Smith-Thomas Sally Meiners Elizabeth Muir Jian-Sheng Du Elizabeth Housden Alan R. Johnson Andreas Faissner Herbert M. Geller Roger J. Keynes John H. Rogers James W. Fawcett 《Brain research》1995,689(2):207
The adult mammalian central nervous system (CNS) lacks the capacity to support axonal regeneration. There is increasing evidence to suggest that astrocytes, the major glial population in the CNS, may possess both axon-growth promoting and axon-growth inhibitory properties and the latter may contribute to the poor regenerative capacity of the CNS. In order to examine the molecular differences between axon-growth permissive and axon-growth inhibitory astrocytes, a panel of astrocyte cell lines exhibiting a range of axon-growth promoting properties was generated and analysed. No clear correlation was found between the axon-growth promoting properties of these astrocyte cell lines with: (i) the expression of known neurite-outgrowth promoting molecules such as laminin, fibronectin andN-cadherin; (ii) the expression of known inhibitory molecules such tenascin and chondroitin sulphate proteoglycan; (iii) plasminogen activator and plasminogen activator inhibitor activity; and (iv) growth cone collapsing activity. EM studies on aggregates formed from astrocyte cell lines, however, revealed the presence of an abundance of extracellular matrix material associated with the more inhibitory astrocyte cell lines. When matrix deposited by astrocyte cell lines was assessed for axon-growth promoting activity, matrix from permissive lines was found to be a good substrate, whereas matrix from the inhibitory astrocyte lines was a poor substrate for neuritic growth. Our findings, taken together, suggest that the functional differences between the permissive and the inhibitory astrocyte cell lines reside largely with the ECM. 相似文献
18.
A new range of stand magnifiers has been released by the COIL company in the United Kingdom. Examination of these magnifiers reveals that they fail to deliver the rated magnifications labelled prominently on the appliances, as a result of the manufacturer's conformance with the requirements of the German DIN standard and the use of back vertex power (F'v) rather than equivalent dioptric power (Fm) of the magnifier. In this study we provide information on the optometric parameters of these new stand magnifiers that will assist the more accurate specification of improvements in vision expected from their use. 相似文献
19.
Tauseef Ahmed Alan Yagoda Howard I. Scher Cora Sternberg Robin C. Watson 《Investigational new drugs》1986,4(2):171-174
Summary Deaza-aminopterin is a folate analog which is transported more rapidly than methotrexate into cells and appears to be more active than methotrexate against human and animal tumor in vitro. Fifteen patients with advanced urothelial tract cancer were given deaza-aminopterin 30–37.5 mg/m2 IV QW. In responding patients drug was given QOW after 4–6 consecutive doses. Doses were escalated or de-escalated by 7.5 mg/m2 depending on toxicity. Twelve patients had received prior chemotherapy which included methotrexate in nine. Three patients achieved a partial remission lasting 1, 3, and 3 months respectively: all responders had previously failed methotrexate after an initial response to a methotrexate containing regimen. None of the six patients who were methotrexate naive responded to deaza-aminopterin; 3 subsequently received methotrexate without response. Mild mucositis was universal and in 5 was severe. Six patients had an increase in liver transaminases probably secondary to anti-folate hepatotoxicity. Other toxicities included diarrhea, nausea, skin rash and fever. Further studies are needed to define the precise efficacy of deaza-aminopterin in patients with urothelial tract cancers. 相似文献
20.