全文获取类型
收费全文 | 24800篇 |
免费 | 2048篇 |
国内免费 | 64篇 |
专业分类
耳鼻咽喉 | 402篇 |
儿科学 | 744篇 |
妇产科学 | 726篇 |
基础医学 | 3225篇 |
口腔科学 | 627篇 |
临床医学 | 3031篇 |
内科学 | 4196篇 |
皮肤病学 | 203篇 |
神经病学 | 1812篇 |
特种医学 | 900篇 |
外科学 | 3715篇 |
综合类 | 543篇 |
一般理论 | 13篇 |
预防医学 | 2917篇 |
眼科学 | 435篇 |
药学 | 1740篇 |
1篇 | |
中国医学 | 45篇 |
肿瘤学 | 1637篇 |
出版年
2021年 | 345篇 |
2020年 | 217篇 |
2019年 | 357篇 |
2018年 | 410篇 |
2017年 | 301篇 |
2016年 | 297篇 |
2015年 | 365篇 |
2014年 | 491篇 |
2013年 | 753篇 |
2012年 | 1107篇 |
2011年 | 1100篇 |
2010年 | 619篇 |
2009年 | 538篇 |
2008年 | 1014篇 |
2007年 | 1120篇 |
2006年 | 974篇 |
2005年 | 962篇 |
2004年 | 997篇 |
2003年 | 909篇 |
2002年 | 865篇 |
2001年 | 874篇 |
2000年 | 871篇 |
1999年 | 720篇 |
1998年 | 378篇 |
1997年 | 346篇 |
1996年 | 329篇 |
1995年 | 318篇 |
1994年 | 229篇 |
1993年 | 200篇 |
1992年 | 605篇 |
1991年 | 525篇 |
1990年 | 507篇 |
1989年 | 493篇 |
1988年 | 490篇 |
1987年 | 436篇 |
1986年 | 472篇 |
1985年 | 455篇 |
1984年 | 364篇 |
1983年 | 306篇 |
1982年 | 208篇 |
1981年 | 193篇 |
1980年 | 212篇 |
1979年 | 346篇 |
1978年 | 236篇 |
1977年 | 223篇 |
1975年 | 189篇 |
1974年 | 227篇 |
1973年 | 204篇 |
1972年 | 199篇 |
1969年 | 198篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Prostaglandin inhibition prevents the fall in pulmonary vascular resistance as a result of rhythmic distension of the lungs in fetal lambs 总被引:1,自引:0,他引:1
Prostaglandins (PG) are vasoactive factors involved in the regulation of pulmonary vascular resistance at birth. However, their physiologic importance is unclear. We hypothesized that PG are important regulators of pulmonary vascular resistance during static and rhythmic distension of the lungs. To test this hypothesis, we studied seven near-term fetal lambs treated with meclofenamate (a PG synthetase inhibitor) and six controls. The fetal lambs were instrumented on a long-term basis with vascular catheters to measure pulmonary arterial pressures, left atrial pressures, and pulmonary blood flow (radionuclide-labeled microsphere method). The fetal airway was intubated, and the ductus arteriosus wall was infiltrated with formalin to assure full patency during the study period. Pulmonary vascular resistance was calculated during baseline and during sequential in utero static distension of the fetal lungs, rhythmic distension, and ventilation with oxygenation. We found that during rhythmic distension, inhibition of PG synthesis abolished the 4-fold decrease in pulmonary vascular resistance seen in the control group. In contrast, during static distension, pulmonary vascular resistance did not change in either group, and during ventilation with oxygenation, pulmonary vascular resistance decreased 12-fold in both groups. We conclude that PG are important regulators of pulmonary vascular resistance during rhythmic distension but are not essential for the regulation of pulmonary vascular resistance during static distension or during ventilation with oxygenation. 相似文献
42.
R S Kahn M Davidson J Hirschowitz R G Stern B M Davis S Gabriel C Moore K L Davis 《Psychiatry research》1992,41(2):155-161
Plasma growth hormone concentrations were measured at hourly intervals between 10 p.m. and 8 a.m. the next morning in 15 drug-free chronic schizophrenic male inpatients and 14 healthy males. Growth hormone secretion was significantly lower in the patients as compared with the controls. Growth hormone release peaked around 1 a.m. in the controls, but a growth hormone peak was absent in the patient group. Increased dopamine activity, increased serotonin activity, or both could explain the absence of a nocturnal growth hormone surge in the schizophrenic patients. 相似文献
43.
Adele L Boskey David J Moore Michael Amling Ernesto Canalis Anne M Delany 《Journal of bone and mineral research》2003,18(6):1005-1011
Osteonectin function in bone was investigated by infrared analysis of bones from osteonectin-null (KO) and wildtype mice (four each at 11, 17, and 36 weeks). An increase in mineral content and crystallinity in newly formed KO bone and collagen maturity at all sites was found using FTIR microspectroscopy and imaging; consistent with osteonectin's postulated role in regulating bone formation and remodeling. Mineral and matrix properties of tibias of osteonectin-null mice and their age- and background-matched wildtype controls were compared using Fourier-transform infrared microspectroscopy (FTIRM) and infrared imaging (FTIRI) at 10- and 7-mm spatial resolution, respectively. The bones came from animals that were 11, 17, and 36 weeks of age. Individual FTIRM spectra were acquired from 20 x 20 microm areas, whereas 4096 simultaneous FTIRI spectra were acquired from 400 x 400 microm areas. The FTIRM data for mineral-to-matrix, mineral crystallinity, and collagen maturity were highly correlated with the FTIRI data in similar regions. In general, the osteonectin-null mice bones had higher mineral contents and greater crystallinity (crystal size and perfection) than the age-matched wildtype controls. Specifically, the mineral content of the newly forming periosteal bone was increased in the osteonectin-null mice; the crystallinity of the cortical bone was decreased in all but the oldest animals, relative to the wildtype. The most significant finding, however, was increased collagen maturity in both the cortical and trabecular bone of the osteonectin-null mice. These spectroscopic data are consistent with a mechanism of decreased bone formation and remodeling. 相似文献
44.
In vitro effects of methotrexate on peripheral blood monocytes: modulation by folinic acid and S-adenosylmethionine. 总被引:1,自引:0,他引:1 下载免费PDF全文
The mechanism of action of low dose methotrexate in rheumatoid arthritis has not been established. It has been shown to have an anti-inflammatory effect and to inhibit neutrophil chemotaxis, but the effect on monocytes has not been widely studied. Normal donor peripheral blood monocytes were incubated with methotrexate in vitro and their superoxide production, chemotaxis, and phagocytosis subsequently assessed. Additionally, the influence of different culture media, and of folinic acid, and the methyl donor S-adenosylmethionine, and spermidine on the methotrexate mediated effects were evaluated. It was found that methotrexate in low concentrations inhibited in vitro monocyte chemotaxis and superoxide production but only after prolonged incubation. This inhibition was augmented by incubation in medium containing a low methionine concentration and was abolished by folinic acid and S-adenosylmethionine, suggesting that methotrexate may interfere with specific methylation reactions. 相似文献
45.
F D Moore 《Annals of surgery》1994,220(6):738-739
46.
Two cases of forearm compartment syndrome in neonates are presented. The compartment syndrome may be initiated before actual delivery and may appear in an advanced stage. In both children good clinical results were achieved when standard guidelines for managing compartment syndrome and established Volkmann's contracture were applied. Although uncommon, compartment syndrome should be considered in the differential diagnosis of the neonate who is unable to move an extremity. 相似文献
47.
48.
M Burgin G Hopkins B Moore J Nasser A Richardson R Minchinton 《Medical laboratory sciences》1992,49(4):265-270
This Australian study monitored the effects of monthly plasmapheresis on donor serum IgG and IgM levels in 127 new and 124 established plasma donors who donated 1014 units over a five-month period. Of the 251 donors, 3% had reduced total serum protein (TSP) levels, 7% had low IgG levels and 12% had low IgM levels prior to donation on at least one occasion over the study period. Statistical analysis showed that the TSP, IgG and IgM levels of new donors who had donated plasma on less than 10 occasions were no more likely to fall below normal than those of old donors. However, new and old donors whose IgG or IgM levels fell below normal at any time during the study had significantly lower levels of the relevant parameter on entry to the study. Followed longitudinally, IgG and IgM levels in old and new donors tended to fall, although levels fluctuated throughout the study. Statistical analysis failed to show any correlation between TSP levels and IgG or IgM levels. These parameters did not correlate significantly with the number of previous plasmaphereses, donor weight, volume collected or history of infection. This study highlighted the need for regular, specific quantitation of IgG and IgM levels as well as TSP in regular plasmapheresis donors. The frequency of testing is yet to be determined, in view of the high materials and labour costs of such a programme. 相似文献
49.
Donna White Suzanne Moore Stephen Waring Karon Cook Eugene Lai 《Movement disorders》2007,22(7):915-923
To better understand the impact of incident Parkinson's disease (PD) on the Veteran's Health Administration (VHA) and to develop methods applicable to future epidemiological research, we performed a medical record review study at a tertiary referral VHA medical center. Searching the local data base, we identified 782 veterans with diagnostic codes for PD or secondary parkinsonism (SP) between 1998 and 2000. Based on structured medical record review, a movement disorders specialist confirmed diagnoses for incident parkinsonism cases. Among the 782, 191 incident parkinsonism cases were identified (100 PD, 75 SP, and 16 Parkinson's Plus). Incident PD cases were older at diagnosis (74.5 vs. 70.4 yr; P < 0.05) and more likely to be white (81% vs. 62; P < 0.07) than incident SP cases. Diagnostic codes were insufficient to distinguish between incident PD and SP (positive predictive value, 57% and 39%, respectively), and VHA sources failed to identify 21% of confirmed deaths among the incident PD cohort by November 2004. Although the large number of incident cases identified suggests PD is an important cause of disability among elderly VHA users, observed limitations of VHA sources for identifying incident PD cases and determining their vital status should be considered when designing future studies. 相似文献
50.
We have developed a technique to render knitted Dacron prostheses totally impervious to blood leak by impregnating the cloth with collagen. These grafts were prepared by the manufacturer, sterilized, and have an indefinite shelf life. The objective of this study was to determine whether collagen impregnation has a deleterious effect on surface thrombogenicity and graft healing. The infrarenal aortas of 30 mongrel dogs were replaced with 6 cm X 6 mm Dacron grafts (15 collagen-impregnated and 15 control). The collagen-impregnated prostheses were visibly indistinguishable from the control. After blood flow was restored, no interstitial bleeding occurred in the collagen grafts, in contrast to the control grafts that initially leaked profusely. When they recovered, the dogs were divided into three groups: group I (five collagen, five control), group II (five collagen, four control), and group III (five collagen, three control). The grafts were harvested at 3, 6, and 9 months, respectively. Retroperitoneal healing response, capsular thickness and adherence, completeness of neointimal healing, surface fibrinolytic activator activity, and sections taken for light and scanning electron microscopy were studied and compared in a blinded fashion. In a separate set of experiments, experimental and control grafts were compared for in vivo surface thrombogenicity. The healing data were identical in the experimental and control prostheses in all parameters. Of particular interest was that initial capsule adherence was better and surface thrombogenicity less in the collagen-impregnated prosthesis. We conclude that collagen impregnation of a knitted Dacron prosthesis has no deleterious effect for the term of observation of this experiment. 相似文献