全文获取类型
收费全文 | 822篇 |
免费 | 25篇 |
国内免费 | 12篇 |
专业分类
耳鼻咽喉 | 11篇 |
儿科学 | 18篇 |
妇产科学 | 27篇 |
基础医学 | 138篇 |
口腔科学 | 4篇 |
临床医学 | 37篇 |
内科学 | 203篇 |
皮肤病学 | 12篇 |
神经病学 | 72篇 |
特种医学 | 9篇 |
外科学 | 113篇 |
综合类 | 4篇 |
预防医学 | 45篇 |
眼科学 | 3篇 |
药学 | 86篇 |
中国医学 | 1篇 |
肿瘤学 | 76篇 |
出版年
2022年 | 24篇 |
2021年 | 23篇 |
2020年 | 16篇 |
2019年 | 9篇 |
2018年 | 16篇 |
2017年 | 5篇 |
2016年 | 5篇 |
2015年 | 16篇 |
2014年 | 18篇 |
2013年 | 30篇 |
2012年 | 31篇 |
2011年 | 46篇 |
2010年 | 21篇 |
2009年 | 29篇 |
2008年 | 31篇 |
2007年 | 62篇 |
2006年 | 50篇 |
2005年 | 65篇 |
2004年 | 57篇 |
2003年 | 38篇 |
2002年 | 50篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 22篇 |
1996年 | 13篇 |
1995年 | 13篇 |
1994年 | 9篇 |
1993年 | 3篇 |
1992年 | 10篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1976年 | 4篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1967年 | 5篇 |
1965年 | 3篇 |
1958年 | 2篇 |
1928年 | 2篇 |
排序方式: 共有859条查询结果,搜索用时 0 毫秒
1.
2.
3.
13C-NMR and the electron impact mass spectra of the β-carboline derivatives 1 – 18 were examined. The structure of the possible diastereomers is discussed. A quantitative relationship between the relative intensity of ions a in the mass spectra of 1 – 18 and the structure of substituents R was found. 相似文献
4.
Charles J. Coté Alfred L. Daniels Michelle Connolly Stanislaw K. Szyfelbein Charles D. Wickens 《Journal canadien d'anesthésie》1992,39(5):454-457
We undertook a prospective study of standard peripheral pulse oximetry versus a modified pulse oximeter probe applied to the tongue in order to determine the efficacy of this alternative monitoring site in children with thermal injuries. Ten patients with a mean age (± SD) of 7.5 ± 4.5 yr were studied on 15 occasions. The mean weight +- SD) was 31.4+- 13.7 kg and percent surface area burn (± SD) was 56+- 21%. A total of 1,992 min of anaesthesia time was monitored. Both sites functioned simultaneously 47% of the time; the lingual but not the peripheral site functioned 28% of the time and only the peripheral site and not the lingual functioned 22% of the time. Neither site functioned 3% of the time. The tongue oximeter provided 563 min more monitoring time than the peripheral sites. The tongue oximeter also functioned in children with peripheral vasoconstriction when the peripheral sensor failed and was less susceptible to electrocautery interference. The tongue oximeter is a reasonable adjunct but not a substitute for peripheral oximetry since its application is limited to paralyzed, intubated patients. 相似文献
5.
6.
Long-term ultraviolet-light (UV) exposure of human skin epidermis is associated with an increased risk for the development of skin cancers, such as melanoma, basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). UV radiation not only induces DNA damage in epidermal cells, it also interferes with skin homeostasis, which is maintained by a unique distribution pattern of apoptosis-inducing and -preventing molecules. If the DNA damage is not repaired or the damaged cells are not eliminated by apoptosis, the consequence can be cell transformation, uncontrolled proliferation and eventually skin tumor formation. An important "repair" gene is the p53 suppressor gene. Excessive UV exposure can mutate the p53 gene leading to the loss of its repair function and thus apoptosis resistance of the DNA-damaged cell. For BCC formation an additional pathway has been identified. Mutation of genes of the Hedgehog signaling pathway evokes the downregulation of apoptotic genes and upregulation of anti-apoptotic genes preventing the elimination of damaged cells. In addition, BCC and SCC strongly express the apoptosis-inducing Fas-ligand (FasL) which may help the tumor to escape the attack of immune effector cells. Silencing the genes involved in tumor formation by RNA interference might become a promising new approach to treat skin tumors. 相似文献
7.
Stanislaw Sosnowski Stanislaw Slomkowski Stanislaw Penczek Zbigniew Florjanczyk 《Macromolecular chemistry and physics.》1991,192(7):1457-1465
The synthesis of highly uniform (1,08 ≤ M w/M n ≤ 1,13) telechelic poly(ε-caprolactone) terminated at both ends with OH groups and its derivatization leading to poly(ε-caprolactone) with pyrene end-groups are described. The synthesis, carried out in THF at room temperature, involves initiation with (CH3CH2)2AlO(CH2CH2O)3Al(CH2CH3)2, leading to poly(ε-caprolactone) macromolecules growing at both ends. The active centers were deactivated with acetic acid, giving macromolecules with OH end-groups. Reaction of α,ω-dihydroxypoly(ε-caprolactone), HO-poly(εCL)-OH, with 4-(1-pyrenyl)butyryl chloride yields α,ω-di-1-pyrenylpoly(ε-caprolactone), Py-poly(εCL)-Py. Polymers are characterized by GPC, 1H NMR, and UV spectroscopies. The UV spectra of polymers with pyrene end-groups are compared with the UV spectra of the model compound. 相似文献
8.
Irena Penczek Yur
N. Sazanov Stanislaw Penczek 《Macromolecular chemistry and physics.》1967,100(1):156-166
In the polymerization of 3,3-bis(chloromethyl)oxetane catalyzed by Aliso-C4H9/water catalyst, according to the previously reported data (FURUKAWA, SAEGUSA et al.) insoluble polymers are formed. Although neither the exact mechanism of oxetanes polymerization in the presence of AIR3/H2O catalysts nor the nature of the insoluble polymers are known it is possible to use chain transfer agents to obtain perfectly soluble polymers. The addition of low molecular weight ethers (C2H5)2O, (n-C4H9)2O, (Allyl)2O, 1,4-dioxane, (β-ClC2H4)2O, CH3OPh, and (C6H5)2O in low concentrations leads to the formation of soluble polymers with a very large range of mol. wts. (up to 106). The chain transferabilities of ethers increase with their proton-attracting powers (basicity). In the presence of a chain transfer agent the kinetics of polymerization virtually changes. On the basis of the discussion of the general kinetic behaviors of the system and the dependence of D?P? on conversion it was deduced that in this type of polymerization long living species are formed. 相似文献
9.
Acceleration of the Menstrual Cycle by Intercourse 总被引:1,自引:0,他引:1
Hazard statistics were applied to an extensive set of prospective data to test for an acceleration of the menstrual cycle by intercourse. Intercourse appeared to accelerate both the basal body temperature (BBT) shift and the onset of menses. Menses was accelerated more by a combination of follicular and luteal intercourse than by luteal intercourse alone (using the BBT shift as an ovulation indicator). The accelerator effects of intercourse therefore appear to cumulate across the menstrual cycle. 相似文献
10.
Differential Regulation of Bax, Bcl-2, and Bcl-X Proteins in Focal Cortical Ischemia in the Rat 总被引:9,自引:0,他引:9
Stefan Isenmann Guido Stoll Michael Schroeter Stanislaw Krajewski John C. Reed Mathias Bähr 《Brain pathology (Zurich, Switzerland)》1998,8(1):49-62
Focal ischemia in the parietal cortex of the rat results in massive neuronal death in the infarct zone and penumbra between 12 hours and 6 days after photothrombosis. To examine a possible role of Bcl-2 family proteins in this process of cell death, we investigated their expression by immunoblot assays and immunocytochemistry, and correlated expression patterns with TUNEL as well as morphological signs indicative of apoptosis. In the center of the lesion Bax immunostaining was increased in many degenerating neurons between 4 hours and 3 days after the induction of photothrombosis. At all time points examined, Bcl-2 and Bcl-X protein levels were markedly reduced in injured neurons as compared to the unlesioned side. At the border of the ischemic lesion, two areas were distinguished: 1 – 2 days after induction of photothrombosis, pyknotic cells located immediately adjacent to the lesion core displayed nuclear Bcl-X and Bax immunoreactivity. In contrast, large, morphologically intact neurons located more towards the healthy brain parenchyma displayed an increase in cytoplasmic Bcl-2 and Bcl-X proteins. Double staining for each of the Bcl-2 family proteins and TUNEL revealed that DNA strand breaks and nuclear fragmentation seen in cells located in the lesion core were often associated with increased levels of Bax, but not with elevated Bcl-2 or Bcl-X protein levels, suggesting a role for Bax in the induction of apoptotic death in these cells. The upregulation of Bcl-2 and Bcl-X expression in surviving neurons close to the penumbra might reflect an active survival mechanism that protects these neurons from cell death following a sublethal insult. 相似文献