全文获取类型
收费全文 | 3530篇 |
免费 | 197篇 |
国内免费 | 47篇 |
专业分类
耳鼻咽喉 | 21篇 |
儿科学 | 146篇 |
妇产科学 | 72篇 |
基础医学 | 377篇 |
口腔科学 | 12篇 |
临床医学 | 284篇 |
内科学 | 439篇 |
皮肤病学 | 24篇 |
神经病学 | 499篇 |
特种医学 | 208篇 |
外科学 | 415篇 |
综合类 | 448篇 |
现状与发展 | 1篇 |
预防医学 | 233篇 |
眼科学 | 8篇 |
药学 | 303篇 |
3篇 | |
中国医学 | 49篇 |
肿瘤学 | 232篇 |
出版年
2023年 | 31篇 |
2022年 | 57篇 |
2021年 | 106篇 |
2020年 | 85篇 |
2019年 | 82篇 |
2018年 | 101篇 |
2017年 | 96篇 |
2016年 | 121篇 |
2015年 | 121篇 |
2014年 | 230篇 |
2013年 | 247篇 |
2012年 | 218篇 |
2011年 | 221篇 |
2010年 | 165篇 |
2009年 | 188篇 |
2008年 | 168篇 |
2007年 | 179篇 |
2006年 | 159篇 |
2005年 | 153篇 |
2004年 | 98篇 |
2003年 | 107篇 |
2002年 | 82篇 |
2001年 | 84篇 |
2000年 | 52篇 |
1999年 | 62篇 |
1998年 | 66篇 |
1997年 | 38篇 |
1996年 | 48篇 |
1995年 | 35篇 |
1994年 | 19篇 |
1993年 | 22篇 |
1992年 | 25篇 |
1991年 | 20篇 |
1990年 | 20篇 |
1989年 | 23篇 |
1988年 | 25篇 |
1987年 | 18篇 |
1986年 | 17篇 |
1985年 | 27篇 |
1984年 | 21篇 |
1983年 | 21篇 |
1982年 | 15篇 |
1981年 | 20篇 |
1980年 | 16篇 |
1979年 | 19篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1975年 | 4篇 |
1973年 | 4篇 |
排序方式: 共有3774条查询结果,搜索用时 15 毫秒
21.
We present a theoretical model of gas transport through the dead space during high-frequency ventilation (HFV) with volumes
less than dead space volume. The analysis is based on the axial distribution of transit times of gas moving through the dead
space. The model predicts that for tidal volumes (V) much less than dead space (Vd), gas exchange will be proportional to the product of frequency (f) and V2. If gas transport is analyzed in terms of Fick's law, then the effective diffusion coefficient (Deff) can be shown to be equal to fV2 times a constant, whose value equals the square of the coefficient of dispersion of axial transit times through the dead
space
. Experimental results in straight tubes fit the predictions of this model quite well. A
through the entire dead space of about 30% is more than sufficient to account for gas exchange during HFV in physical models
or in intact animals. An axial dispersion of this magnitude can be measured directly from a typical Fowler dead space determination
in healthy subjects. 相似文献
22.
Amongst adults exposed to the hepatitis B virus (HBV), the infection pursues a fulminant course more frequently in females, while conversely a chronic carrier state is more frequent in males. Because of these differences in sex ratio, we investigated the relationship between the outcome of HBV infection and serum concentrations of sex hormone-binding globulin (SHBG), a circulating glycoprotein that exerts an important influence on the balance of free sex hormones. SHBG levels were significantly elevated in females with fulminant HBV infection compared to females with either uncomplicated acute or chronic HBV infection (P less than .05 and P less than .001, respectively). That this was not a nonspecific effect of fulminant hepatitis was confirmed by the significantly higher levels in this group than in age-matched females with fulminant hepatitis unrelated to HBV (P less than .05). In contrast, four of 15 female HBsAg carriers had SHBG values in the male range, and these included three of four patients who had acquired HBV as adults. SHBG levels were normal in all male groups. These results suggested that for adults the hormonal environment may be important in determining the course of HBV infection. 相似文献
23.
Conjugation of DNA fragments to protein carriers by glutaraldehyde: immunogenicity of oligonucleotide-hemocyanin conjugates 总被引:1,自引:0,他引:1
The practical realization of the concept of specific immunotherapy for systemic lupus erythematosus (SLE) has been hampered, thus far, by an inability to link DNA fragments to carrier protein. In this paper, a novel technique is described, in which glutaraldehyde is the linking agent. A 2-stage method was used to link oligonucleotides to a soluble protein carrier, such as keyhole limpet hemocyanin (KLH) or human gamma globulin (HGG), whereas a 1-stage technique was sufficient to link oligonucleotides to sheep red cells. Both the ultraviolet absorbance spectrum and diphenylamine assay demonstrated that oligonucleotides were coupled to soluble protein. The conjugate of oligonucleotide to protein carrier appears to be recognized by anti-DNA antibody since oligonucleotide linked to either KLH or HGG inhibited the binding of anti-DNA antibody in vitro, and oligonucleotide-coupled sheep cells are agglutinating by seropositve sera from lupus patients. In addition, oligonucleotide-KLH raised hemagglutinating antibody to denatured DNA in C57BL/6, DBA/2 or NZB mice, as well as IgG antibody as detected by SPRIA in C57BL/6 and DBA/2 mice. The significance of this new method for the development of an antigen specific therapy of SLE is discussed. 相似文献
24.
The molecular nature of the membrane antigen that is acquired from FCS-containing media by human lymphoblastoid cells has been investigated. The presence of bovine α2, macroglobulin on the surface of Namalva cells was demonstrated by radioimmunoassay using specific antisera. Alternatively, cell-bound bovine α2,M could be detected by the more sensitive heterophile rosette assay described previously. Namalva cells grown in NHS-containing media acquired bovine α2 M upon subsequent incubation with the purified protein in a dose- and time-dependent way. Acquisition of α2 M was demonstrated using both viable and formaldehyde-fixed cells. Purified fetuin, which carries a heterophile epitope shared with bovine α2 M as well as with other glycoproteins, failed to bind with the membrane of Namalva cells. The possible role of acquired α2 macroglobulin on cells has been discussed. 相似文献
25.
Morphologic evaluation of the liver in hereditary angioedema patients on long-term treatment with androgen derivatives 总被引:1,自引:0,他引:1
M Cicardi L Bergamaschini A Tucci A Agostoni G Tornaghi G Coggi R Colombi G Viale 《The Journal of allergy and clinical immunology》1983,72(3):294-298
17 alpha-Alkylated androgens are highly effective in preventing attacks in HAE patients. These drugs, however, seem to be implicated in the development of cholestatic jaundice, peliosis hepatis, and liver tumors. In order to assess the risk-benefit balance of the long-term therapy with androgen derivatives, a follow-up investigation was performed in 13 HAE patients. The results of this study indicate that long-term treatment (15 to 47 mo) with low doses of danazol or stanozolol does not induce significant hepatic damage detectable by laboratory tests or liver biopsy. However, the limited number of patients, although in a rather long period of observation, still suggests a careful control and the use of minimal effective doses. 相似文献
26.
Vesna Čapkun Davor Eterović 《European journal of nuclear medicine and molecular imaging》1985,11(4):120-122
Radionuclide-angiography (RNA_ left-to-right intracardiac-shunt quantification algorithms, based on the part-by-part fit technique and the use of a so-called gamma variate model function (GVF), were tested via simulation analysis using data obtained from normal subjects. A good bolus of radioindicator was obtained by administering it directly into the vena subclavia. Normal subjects were defined as those having pulmonary histograms (PH) with no visible distortion caused by a shunt. Pure, non-superimposed data on the downslope of the PH curves, which are lost in presence of a shunt, proved to be appropriate reference values for testing the accuracy of results of standard shunt quantification algorithms. A generalized four-parameter GVF was introduced in order to extend the flexibility of the model function. The use of the three-parametric GVF to reconstruct the downslope of the PH curve out of the upslope data proved to be inadequate. This reveals an evident source of error in algorithms that calculate the shunt contribution by fitting GVF parameters to so-called difference-curve data. It is concluded that the inherent restricted statistical weight of RNA data prevents accurate results being obtained from standard RNA-shunt-assessment algorithms. 相似文献
27.
Aromatase inhibition by delta 1-testolactone (Teslac, 500 mg twice daily) for 6 months in 9 patients with idiopathic oligozoospermia lowered the levels of serum estradiol (E2) and thereby sex hormone binding globulin (SHBG) (rS = +0.40, p less than 0.025) to values -35 and -25%, respectively, below the pretreatment values (P less than 0.001 and less than 0.005). The E2 decrease was accompanied by a temporary increase (+50%) in the levels of follicle stimulating hormone (FSH), not of luteinizing hormone (LH), and of 17 alpha-hydroxyprogesterone (17 alpha-OHP), but less of testosterone (T) (+30%), which led to a transient rise in the 17 alpha-OHP/T ratio. The T/E2 ratio and "free T" index (T/SHBG) almost doubled until the end of the treatment period. During delta 1-testolactone treatment the mean sperm density gradually rose from 8.1 +/- 1.3 (SEM) before to 21.3 +/- 6.7 X 10(6)/ml after 6 months (P less than 0.01), whereas the total sperm count almost threefold increased (P less than 0.05). Sperm concentrations exceeding 20 X 10(6)/ml were achieved in 4 of the 9 patients. Two of these patients' wives became pregnant. Although the data point to a pivotal role of estrogens in the pathogenesis of the spermatogenic lesion in some patients with idiopathic oligozoospermia, the lack of a beneficial effect of estrogen lowering in others points to a multicausal nature of the disease entity. 相似文献
28.
Paolo Dell’Oglio Philippa Meershoek Tobias Maurer Esther M.K. Wit Pim J. van Leeuwen Henk G. van der Poel Fijs W.B. van Leeuwen Matthias N. van Oosterom 《European urology》2021,79(1):124-132
BackgroundThe DROP-IN gamma probe was introduced to overcome the restricted manoeuvrability of traditional laparoscopic gamma probes. Through enhanced manoeuvrability and surgical autonomy, the DROP-IN promotes the implementation of radioguided surgery in the robotic setting.ObjectiveTo confirm the utility and safety profile of the DROP-IN gamma probe and to perform a comparison with the traditional laparoscopic gamma probe and fluorescence guidance.Design, setting, and participantsTwenty-five prostate cancer patients were scheduled for a robot-assisted sentinel lymph node (SN) procedure, extended pelvic lymph node dissection, and prostatectomy at a single European centre.Surgical procedureAfter intraprostatic injection of indocyanine green (ICG)-99mTc-nanocolloid (n = 12) or 99mTc-nanocolloid + ICG (n = 13), SN locations were defined using preoperative imaging. Surgical excision of SNs was performed under image guidance using the DROP-IN gamma probe, the traditional laparoscopic gamma probe, and fluorescence imaging.MeasurementsIntraoperative SN detection was assessed for the different modalities and related to anatomical locations. Patient follow-up was included (a median of 18 mo).Results and limitationsOverall, 47 SNs were pursued in vivo by the DROP-IN gamma probe, of which 100% were identified. No adverse events related to its use were observed. In vivo fluorescence imaging identified 91% of these SNs. The laparoscopic gamma probe identified only 76% of these SNs, where the detection inaccuracies appeared to be related to specific anatomical regions.ConclusionsOwing to improved manoeuvrability, the DROP-IN probe yielded improved SN detection rates compared with the traditional gamma probe and fluorescence imaging. These findings underline that the DROP-IN technology provides a valuable tool for radioguided surgery in the robotic setting.Patient summaryRadioguided robot-assisted surgery with the novel DROP-IN gamma probe is feasible and safe. It enables more efficient intraoperative identification of sentinel lymph nodes than can be achieved with a traditional laparoscopic gamma probe. The use of the DROP-IN probe in combination with fluorescence imaging allows for a complementary optical confirmation of node localisations. 相似文献
29.
Interaction of immunoglobulin with actin 总被引:8,自引:0,他引:8
Actin can form specific, direct associations with immunoglobulin resulting in soluble complexes or cross-linked matrices. This interaction can be detected by four in vitro assays using purified components: (1) actin enhances the cytophilic activity of guinea pig IgG2; (2) in solutions of low ionic strength, actin and IgG2 co-precipitate: (3) soluble complexes exist in 0.1 M KCl as revealed by the displacement of actin from its expected sedimentation pattern in a gradient of sucrose when in the presence of IgG 1, IgG2, or IgM; (4) immunoglobulin (IgG1, IgG2, BGG)‡: increases the viscosity of F-actin solutions, presumably by crosslinking F-actin filaments. These data suggest that direct interaction of a cytoskeletal protein with a cell surface receptor is possible. 相似文献
30.