全文获取类型
收费全文 | 877篇 |
免费 | 63篇 |
国内免费 | 39篇 |
专业分类
儿科学 | 22篇 |
妇产科学 | 159篇 |
基础医学 | 58篇 |
口腔科学 | 5篇 |
临床医学 | 71篇 |
内科学 | 105篇 |
皮肤病学 | 11篇 |
神经病学 | 33篇 |
特种医学 | 126篇 |
外科学 | 220篇 |
综合类 | 17篇 |
预防医学 | 62篇 |
眼科学 | 9篇 |
药学 | 36篇 |
中国医学 | 1篇 |
肿瘤学 | 44篇 |
出版年
2020年 | 5篇 |
2015年 | 10篇 |
2014年 | 17篇 |
2013年 | 21篇 |
2012年 | 13篇 |
2011年 | 24篇 |
2010年 | 14篇 |
2009年 | 16篇 |
2008年 | 22篇 |
2007年 | 37篇 |
2006年 | 24篇 |
2005年 | 27篇 |
2004年 | 24篇 |
2003年 | 22篇 |
2002年 | 25篇 |
2001年 | 34篇 |
2000年 | 23篇 |
1999年 | 28篇 |
1998年 | 24篇 |
1997年 | 16篇 |
1996年 | 25篇 |
1995年 | 38篇 |
1994年 | 15篇 |
1993年 | 20篇 |
1992年 | 33篇 |
1991年 | 37篇 |
1990年 | 45篇 |
1989年 | 44篇 |
1988年 | 26篇 |
1987年 | 30篇 |
1986年 | 26篇 |
1985年 | 22篇 |
1984年 | 17篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 11篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1970年 | 4篇 |
1968年 | 5篇 |
1967年 | 6篇 |
1943年 | 5篇 |
1937年 | 4篇 |
1935年 | 4篇 |
排序方式: 共有979条查询结果,搜索用时 187 毫秒
81.
Mewissen MW; Erickson SJ; Foley WD; Lipchik EO; Olson DL; McCann KM; Schreiber ER 《Radiology》1989,173(1):155-157
Color Doppler flow imaging or compression ultrasound (US) was used to prospectively determine frequency of thrombosis at 54 venous insertion sites (47 in common femoral veins, seven in right internal jugular veins) after percutaneous placement of Greenfield filters for interruption of the inferior vena cava. Fifty-one filters were successfully placed in 51 patients with a dilator set or a balloon angioplasty catheter. Nine focal thrombi were detected in the common femoral vein (19%) and one in the right internal jugular vein (14%). Use of dilators induced eight thrombi (24%), compared with two (10%) from balloon catheters. The left common femoral vein had a high frequency of thrombosis, regardless of dilation technique (five of nine). Of nine patients with acute common femoral vein thrombosis, four became symptomatic within 10 days after the procedure. Patients may remain asymptomatic or have delayed symptoms; thus, US is valuable for determining patients at risk of thrombosis of the common femoral vein. 相似文献
82.
Toby Soper Pierre Mandin Nadim Majdalani Susan Gottesman Sarah A. Woodson 《Proceedings of the National Academy of Sciences of the United States of America》2010,107(21):9602-9607
Bacterial small noncoding RNAs carry out both positive and negative regulation of gene expression by pairing with mRNAs; in Escherichia coli, this regulation often requires the RNA chaperone Hfq. Three small regulatory RNAs (sRNAs), DsrA, RprA, and ArcZ, positively regulate translation of the sigma factor RpoS, each pairing with the 5′ leader to open up an inhibitory hairpin. In vitro, rpoS interaction with sRNAs depends upon an (AAN)4 Hfq-binding site upstream of the pairing region. Here we show that both Hfq and this Hfq binding site are required for RprA or ArcZ to act in vivo and to form a stable complex with rpoS mRNA in vitro; both were partially dispensable for DsrA at 37 °C. ArcZ sRNA is processed from 121 nt to a stable 56 nt species that contains the pairing region; only the 56 nt ArcZ makes a strong Hfq-dependent complex with rpoS. For each of these sRNAs, the stability of the sRNA•mRNA complexes, rather than their rate of formation, best predicted in vivo activity. These studies demonstrate that binding of Hfq to the rpoS mRNA is critical for sRNA regulation under normal conditions, but if the stability of the sRNA•mRNA complex is sufficiently high, the requirement for Hfq can be bypassed. 相似文献
83.
84.
85.
Late functional adaptation after colectomy, mucosal proctectomy, and ileal pouch-anal anastomosis 总被引:10,自引:0,他引:10
J M Becker K M McGrath M P Meagher J E Parodi D A Dunnegan N J Soper 《Surgery》1991,110(4):718-24; discussion 725
Ileal pouch-anal anastomosis (IPAA) is currently an alternative to proctocolectomy and ileostomy for patients with ulcerative colitis or familial polyposis. Some studies have suggested significant anal sphincter damage after mucosal proctectomy. Our aim was to assess prospectively late sphincter function after IPAA. In 250 patients, anorectal pressures were assessed with a pneumohydraulic perfused catheter manometry system. Each patient underwent colectomy, mucosal proctectomy, ileoanal anastomosis of a 15 cm ileal J-pouch, and loop ileostomy. Eight weeks after IPAA, anal manometry was repeated, and the ileostomy was closed. Manometry was repeated at yearly intervals. A decline in resting tone of the anal sphincter occurred early after IPAA with a gradual recovery toward control. External sphincter squeeze after pressures were not affected by IPAA and steadily increased to 8 years after operation. During this time, a progressive increase in J-pouch capacity was noted, and 24-hour stool frequency declined from 7.9 +/- 0.3 stools to 6.5 +/- 0.3 stools (p less than 0.05). We conclude that mucosal proctectomy results in internal anal sphincter trauma but is associated with long-term sphincter recovery, coupled with a significant improvement in external sphincter capacity, ileal pouch volume, and stool frequency. 相似文献
86.
Coleman CC; Posalaky IP; Robinson JD; Payne WD; Vlodaver ZA; Amplatz K 《Radiology》1989,170(2):391-394
The mode of action of the Kensey catheter, a new atheroablation device, was investigated. Fresh above-the-knee amputated legs were used for recanalization of the superficial femoral artery. The variables used were identical to those of clinical trials, including a rotational speed of 50,000 rpm and an injection rate of 40 mL/min. The debris produced by the catheter was studied cytologically, and the arterial segments were examined histologically. The particle size in the debris ranged from 1 to 2,000 microns. The softer plaques produced a fine fibrin dust background with long strips of intima ranging from 10 to 2,000 microns. Complicated calcified plaques produced larger background material (10-120 microns) but smaller strips of intima (50-800 microns). Dissections and perforations occurred. Some of the debris produced by the atheroablation process was used to embolize a canine heart and kidney. Small focal infarctions were found in the heart, and large and multiple infarcts were seen in the kidney. In clinical studies the debris appears to be tolerated in the lower extremities. Its safety in the kidney and heart are questioned. 相似文献
87.
The relative frequency of pharyngeal gonococcal infection may be increased in certain prenatal populations. Therapy of penicillin-sensitive strains of Neisseria gonorrhoeae is associated with acceptable cure rates using aqueous procaine penicillin with probenecid. Infection of the oropharynx of pregnant women with penicillinase-producing strains is more problematic. The antibiotics normally used for the therapy of uncomplicated penicillinase-producing N gonorrhoeae infections, spectinomycin or cefoxitin, are not effective in the therapy of pharyngeal infection. Reported is the first case of penicillinase-producing N gonorrhoeae oropharyngeal infection during pregnancy. The patient was successfully treated with trimethoprim/sulfamethoxazole, and no maternal or neonatal morbidity was noted. 相似文献
88.
Immunochemical characterization and radioimmunometric detection of molecules shed by human ovarian cancer 总被引:1,自引:0,他引:1
F Leoni R C Bast S Canevari S Menard J T Soper M I Colnaghi 《International journal of cancer. Journal international du cancer》1987,40(5):592-597
Monoclonal antibodies (MAbs) OC125, MOv2 and MOv8 recognize the CA125, CAMOv2 and CAMOv8 epitopes, respectively, which are associated with human ovarian carcinomas and are shed by these tumors. The biochemical analysis of the recognized antigens and epitopes has been performed to investigate the possibility of exploiting their expression, if any, on the same molecules. Cross-competition experiments clearly indicated that the 3 epitopes are distinct. Biochemical analysis was performed on a cyst fluid from an ovarian cystadenoma. Heat treatment and periodate oxidation indicated that CAMOv2 and CAMOv8 are saccharidic and suggested that CA125 is a conformational epitope to which both saccharides and the protein backbone could contribute. By gel-filtration chromatography CA125 activity was eluted into 2 peaks of high molecular weight, whereas CAMOv2 and CAMOv8 activities were associated with a single broad peak which included CA125-positive fractions. Isopycnic centrifugation showed that CA125, CAMOv2 and CAMOv8 carrying molecules had the same high density (1.46 g/ml) in the first peak, whereas CA125 molecules had a lower density (1.41 g/ml) in the second peak. Double-determinant immunoradiometric assays, carried out using different combinations of the MAbs, indicated that in the cyst fluid molecules expressing both CAMOv2 and CAMOv8 could be detected, whereas CA125 was carried by different molecules. CAMOv2 and CA125 could however be expressed on the same molecule in 2 out of 9 ascitic fluids from ovarian carcinoma patients. Taken together, these data indicate that CA125 and CAMOv2-CAMOv8 were only occasionally expressed on the same molecules. Therefore, the use of the CA125-CAMOv2 combination could not increase the sensitivity achievable by using each respective simultaneous immunoradiometric assay. 相似文献
89.
90.
Extensive public health programs are often proposed without a full appreciation of their effects on the target population. There is often a problem of confusing medical care that may be of benefit to an individual with care that may be of benefit to a population: care that may be highly beneficial for a selected patient may be substantially less effective for an unselected population. Exposing a large, asymptomatic population to diagnostic screening for coronary artery disease has cost and risk ramifications far beyond those of discovering people who might benefit from treatment of previously unsuspected disease. A program to screen 20 million people, and treat the most severely affected with coronary artery bypass graft, would cost nearly +9.2 billion. About +21,000 is spent to find each person with disease, while the cost is more than +169,000 for each person surviving surgical therapy. The cost per year of life extended is over +43,000. In excess of 8,000 persons have major complications and nearly 2,000 die from diagnostic testing and therapy. About half of major complications and deaths occur in persons without disease. This model integrating epidemiologic, economic, and decision analytic methods is presented to illustrate the potential use of myriad techniques in addressing population-based medical care and policy options; it does not provide the definitive answer, however, to the complex problem. 相似文献