全文获取类型
收费全文 | 401篇 |
免费 | 27篇 |
国内免费 | 47篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 18篇 |
妇产科学 | 1篇 |
基础医学 | 32篇 |
口腔科学 | 13篇 |
临床医学 | 69篇 |
内科学 | 87篇 |
皮肤病学 | 14篇 |
神经病学 | 6篇 |
特种医学 | 148篇 |
外科学 | 9篇 |
综合类 | 11篇 |
预防医学 | 12篇 |
药学 | 41篇 |
肿瘤学 | 13篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2016年 | 4篇 |
2015年 | 11篇 |
2014年 | 4篇 |
2013年 | 9篇 |
2012年 | 2篇 |
2011年 | 4篇 |
2010年 | 6篇 |
2009年 | 6篇 |
2008年 | 9篇 |
2007年 | 36篇 |
2006年 | 3篇 |
2005年 | 7篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 8篇 |
1999年 | 15篇 |
1998年 | 27篇 |
1997年 | 31篇 |
1996年 | 27篇 |
1995年 | 25篇 |
1994年 | 20篇 |
1993年 | 22篇 |
1992年 | 17篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 18篇 |
1988年 | 19篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 14篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1977年 | 14篇 |
1976年 | 9篇 |
1975年 | 4篇 |
排序方式: 共有475条查询结果,搜索用时 15 毫秒
81.
中药升麻的化学成分 总被引:14,自引:0,他引:14
从中药兴安升麻[Cimicifuga dahurica(Turcz.)Maxim.]的干燥根茎中分得五个化合物,其中四个为三萜木糖甙:升麻醇-3-O-β-D-吡喃木糖甙(23R,24S)(Ⅰ),25-O-乙酰升麻醇-3-O-β-D-吡喃木糖甙(23R,24S)(Ⅱ),12-羟基升麻醇-3-O-β-D-吡喃木糖甙(23R,24S)(Ⅲ),升麻醇-3-O-β-D-吡喃木糖基(3→1)-β-D-吡喃木糖甙(23R,24S)(Ⅳ),另一个为异阿魏酸(Ⅴ)。Ⅲ和Ⅳ为新化合物,通过光谱(IR,MS,1H及13C NMR)解析确定了它们的结构,分别命名为升麻甙A(cimiside A)和升麻甙B(cimiside B)。 相似文献
82.
PL Perrotta ; L Baril ; C Tead ; J Chapman ; D Dincecco ; DH Buchholz ; EL Snyder 《Transfusion》1999,39(1):63-69
BACKGROUND: Photochemical methods can effectively inactivate extracellular viruses and bacteria found in blood components. Treatment of plasma with methylene blue (MB), a phenothiazine dye, and visible light inactivates enveloped viruses including HIV-1. The effects of MB- treated plasma on cellular components stored in vitro have not been well characterized. STUDY DESIGN AND METHODS: MB-treated plasma (83 microg MB/250 mL plasma) was added to single-donor platelets, stored AS- 1 red cells (RBCs), irradiated RBCs, and frozen-deglycerolized RBCs. In vitro platelet assays performed after 1 and 5 days of storage in MB- treated plasma included pH, pO2, pCO2, HCO3, platelet number, lactate dehydrogenase, glucose, osmotic recovery, and CD62 expression. RBC components were examined at specific intervals for leakage of potassium, plasma hemoglobin level, and percentage of hemolysis. Direct antiglobulin tests, osmotic fragilities, and RBC antigen stability tests were also performed on RBCs stored in MB-treated plasma. Components stored with autologous plasma or nontreated allogeneic plasma served as controls. RESULTS: Similar storage-induced changes in pH, glucose, and platelet numbers, as well as increases in lactate dehydrogenase, CD62 expression, and lactate were seen in single-donor platelets stored with MB-treated and control plasma. Platelet morphology scores and osmotic recoveries were not altered. Plasma hemoglobin and potassium and percentage of hemolysis increased equally in the various RBC components stored with MB-treated or nontreated plasma. Osmotic fragility and RBC antigen stability were not appreciably altered by MB-treated plasma. CONCLUSION: Plasma treated by MB photoinactivation can be used for in vitro resuspension and storage of platelets or RBCs, because of the lack of influence of MB-treated plasma on a variety of in vitro platelet and RBC assays. 相似文献
83.
SA Rabacchi JM Solowska B Kruk Y Luo JA Raper DH Baird 《The Journal of neuroscience》1999,19(11):4437-4448
Most axons in the CNS innervate specific subregions or layers of their target regions and form contacts with specific types of target neurons, but the molecular basis of this process is not well understood. To determine whether collapsin-1/semaphorin-III/D, a molecule known to repel specific axons, might guide afferent axons within their cerebellar targets, we characterized its expression by in situ hybridization and observed its effects on mossy and climbing fiber extension and growth cone size in vitro. In newborn mice sema-D is expressed by cerebellar Purkinje cells in parasagittal bands located medially and in some cells of the cerebellar nuclei. Later, sema-D expression in Purkinje cells broadens such that banded expression is no longer prominent, and expression is detected in progressively more lateral regions. By postnatal day 16, expression is observed throughout the cerebellar mediolateral axis. Collapsin-1 protein, the chick ortholog of sema-D, did not inhibit the extension of neurites from explants of inferior olivary nuclei, the source of climbing fibers that innervate Purkinje cells. In contrast, when it was applied to axons extending from basilar pontine explants, a source of mossy fiber afferents of granule cells, collapsin-1 caused most pontine growth cones to collapse, as evidenced by a reduction in growth cone size of up to 59%. Moreover, 63% of pontine growth cones arrested their extension or retracted. Its effects on mossy fiber extension and its distribution suggest that sema-D prevents mossy fibers from innervating inappropriate cerebellar target regions and cell types. 相似文献
84.
HPLC法测定地西泮和艾司唑仑的血药浓度 总被引:9,自引:0,他引:9
建立HPLC法同时测定地西泮和艾司唑仑血药浓度。方法:以Ultrasphere-ODS5μm4.6mm*25cm色谱柱为分离柱,流动相:甲醇-乙腈-水(40:20:40);检测波长为254nm,以外标法峰面积定量。结论本法可用于血药浓度测定。 相似文献
85.
86.
87.
Breast cancer detection: one versus two views 总被引:2,自引:0,他引:2
Mammographic examinations of 169 patients with 172 biopsy-proved carcinomas, and of 194 healthy subjects, were interpreted independently and retrospectively by three experienced mammographers, initially as single-view oblique examinations and 6 months later as two-view oblique-cephalocaudal examinations. For the single-view examinations of the cancer patients, 67% of the cancers were correctly recommended for biopsy, additional views were requested for 23%, and a "negative" interpretation was made for 10%. For the single-view examinations of healthy subjects, biopsy was recommended for 7% and additional views were recommended for 32%. For the two-view examinations of women with cancer, 80% of the cancers were correctly recommended for biopsy, additional views were requested for 4%, and a "negative" interpretation was made for 16%. For two-view examinations of healthy subjects, biopsy was recommended for 7% and additional views were requested for only 5%. The authors conclude that single-view screening should not be performed, because it would lead to an excessive number of "call-back" examinations of healthy patients, producing additional cost and anxiety that would outweigh any theoretical benefit. 相似文献
88.
Kirsten JE Asmus-Szepesi Paul L de Vreede Anna P Nieboer Jeroen DH van Wijngaarden Ton JEM Bakker Ewout W Steyerberg Johan P Mackenbach 《BMC geriatrics》2011,11(1):1-17
Background
Elderly persons admitted to the hospital are at risk for hospital related functional loss. This evaluation aims to compare the effects of different levels of (integrated) health intervention care programs on preventing hospital related functional loss among elderly patients by comparing a new intervention program to two usual care programs.Methods/Design
This study will include an effect, process and cost evaluation using a mixed methods design of quantitative and qualitative methods. Three hospitals in the Netherlands with different levels of integrated geriatric health care will be evaluated using a quasi-experimental study design. Data collection on outcomes will take place through a prospective cohort study, which will incorporate a nested randomised controlled trial to evaluate the effects of a stay at the centre for prevention and reactivation for patients with complex problems. The study population will consist of elderly persons (65 years or older) at risk for functional loss who are admitted to one of the three hospitals. Data is prospectively collected at time of hospital admission (T0), three months (T1), and twelve months (T2) after hospital admission. Patient and informal caregiver outcomes (e.g. health related quality of life, activities of daily living, burden of care, (re-) admission in hospital or nursing homes, mortality) as well as process measures (e.g. the cooperation and collaboration of multidisciplinary teams, patient and informal caregiver satisfaction with care) will be measured. A qualitative analysis will determine the fidelity of intervention implementation as well as provide further context and explanation for quantitative outcomes. Finally, costs will be determined from a societal viewpoint to allow for cost effectiveness calculations.Discussion
It is anticipated that higher levels of integrated hospital health care for at risk elderly will result in prevention of loss of functioning and loss of quality of life after hospital discharge as well as in lower burden of care and higher quality of life for informal caregivers. Ultimately, the results of this study may contribute to the implementation of a national integrated health care program to prevent hospital related functional loss among elderly patients.Trial registration
The Netherlands National Trial Register: NTR2317 相似文献89.
Summary
This study examined the effects of quercetin on spontaneously contracting portal veins isolated from healthy young adult male and female Wistar rats (250–300 g). Quercetin (10-7–10-4 M) always produced significant biphasic effects, comprising an initial brief stimulant effect (rise in basal tone), followed by a sustained, longer-lasting secondary relaxant (inhibitory) effect on the venous tissues. The initial brief contractions of the venous muscle preparations were not modified by preincubation of the tissues with prazosin (10-6 M), suggesting that the initial upsurge in basal tone and increases in contractile frequencies of the venous tissues were probably not mediated via alpha1-adrenoceptor stimulation. However, preincubation of the tissues with nifedipine (10-7 M) significantly suppressed (p < 0.05) or attenuated the initial stimulant effect of quercetin, suggesting that the flavonoid might be activating L-type voltage-dependent calcium channels. The vasorelaxant effect of quercetin was partially but not significantly (p > 0.05) inhibited by L-NAME (100 μM) or indomethacin (10 μM), suggesting that the vasorelaxant effect of the flavonoid was unlikely to be mediated via endothelium-dependent relaxing factor (EDRF), or through prostacyclin (PGI2) pathways. N-p-tosyl-l-phenylalanine-chloromethyl-ketone (TPCK, 3 μM) significantly (p < 0.01) antagonised quercetin-induced relaxations, suggesting that cAMP-dependent protein kinases might have contributed, at least in part, towards the vasorelaxant effect of quercetin on rat isolated portal veins. 相似文献90.