全文获取类型
收费全文 | 10589篇 |
免费 | 734篇 |
国内免费 | 50篇 |
专业分类
耳鼻咽喉 | 55篇 |
儿科学 | 278篇 |
妇产科学 | 184篇 |
基础医学 | 1518篇 |
口腔科学 | 200篇 |
临床医学 | 1014篇 |
内科学 | 2406篇 |
皮肤病学 | 200篇 |
神经病学 | 844篇 |
特种医学 | 411篇 |
外科学 | 1627篇 |
综合类 | 91篇 |
一般理论 | 4篇 |
预防医学 | 829篇 |
眼科学 | 335篇 |
药学 | 652篇 |
中国医学 | 10篇 |
肿瘤学 | 715篇 |
出版年
2023年 | 35篇 |
2022年 | 161篇 |
2021年 | 279篇 |
2020年 | 121篇 |
2019年 | 215篇 |
2018年 | 287篇 |
2017年 | 186篇 |
2016年 | 193篇 |
2015年 | 231篇 |
2014年 | 295篇 |
2013年 | 466篇 |
2012年 | 706篇 |
2011年 | 735篇 |
2010年 | 421篇 |
2009年 | 361篇 |
2008年 | 638篇 |
2007年 | 692篇 |
2006年 | 619篇 |
2005年 | 695篇 |
2004年 | 613篇 |
2003年 | 568篇 |
2002年 | 577篇 |
2001年 | 119篇 |
2000年 | 137篇 |
1999年 | 144篇 |
1998年 | 133篇 |
1997年 | 123篇 |
1996年 | 87篇 |
1995年 | 103篇 |
1994年 | 83篇 |
1993年 | 91篇 |
1992年 | 96篇 |
1991年 | 109篇 |
1990年 | 85篇 |
1989年 | 86篇 |
1988年 | 74篇 |
1987年 | 68篇 |
1986年 | 51篇 |
1985年 | 52篇 |
1984年 | 64篇 |
1983年 | 54篇 |
1982年 | 55篇 |
1981年 | 47篇 |
1980年 | 45篇 |
1979年 | 25篇 |
1978年 | 29篇 |
1977年 | 31篇 |
1976年 | 19篇 |
1974年 | 19篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Parvalbumin 3 is an Abundant Ca2+ Buffer in Hair Cells 总被引:3,自引:0,他引:3
Stefan Heller Andrea M. Bell Charlotte S. Denis Yong Choe A.J. Hudspeth 《Journal of the Association for Research in Otolaryngology》2002,3(4):488-498
Ca2+ signaling serves distinct purposes in different parts of a hair cell. The Ca2+ concentration in stereocilia regulates
adaptation and, through rapid transduction-channel reclosure, underlies amplification of mechanical signals. In presynaptic
active zones, Ca2+ mediates the exocytotic release of afferent neurotransmitter. At efferent synapses, Ca2+ activates the
K+ channels that dominate the inhibitory postsynaptic potential. A copious supply of diffusible protein buffer isolates the
three signals by restricting the spread of free Ca2+ and limiting the duration of its action. Using cDNA subtraction and a
gene expression assay based on in situ hybridization, we detected abundant expression of mRNAs encoding the Ca2+ buffer parvalbumin
3 in bullfrog saccular and chicken cochlear hair cells. We cloned cDNAs encoding this protein from the corresponding inner-ear
libraries and raised antisera against recombinant bullfrog parvalbumin 3. Immunohistochemical labeling indicated that parvalbumin
3 is a prominent Ca2+-binding protein in the compact, cylindrical hair cells of the bullfrog's sacculus, and occurs as well
in the narrow, peanut-shaped hair cells of that organ. Using quantitative Western blot analysis, we ascertained that the concentration
of parvalbumin 3 in saccular hair cells is approximately 3 mM. Parvalbumin 3 is therefore a significant mobile Ca2+ buffer,
and perhaps the dominant buffer, in many types of hair cell. Moreover, parvalbumin 3 provides an early marker for developing
hair cells in the frog, chicken, and zebrafish. 相似文献
22.
Benyam Asefa Paul Kauler Denis Cournoyer Shirley Lehnert T. Y.-K. Chow 《Current genetics》1998,34(5):360-367
The deoxyribonucleases (DNases) have been shown genetically to be important in the vital processes of DNA repair and recombination.
The NUD1 gene, which codes for an endo-exonuclease of Saccharomyces cerevisiae, was analyzed for its role in the DNA double-strand break (DSB) repair processes. While the nud1 strain is only slightly sensitive to ionizing radiation, expression of the HO-endonuclease to introduce a DSB at the MAT locus in that strain results in cell death. Cell survival is inversely proportional to the duration of HO-endonuclease expression.
Analysis of the surviving colonies from the nud1 strain indicated that many of the survivors are sterile and that the proportion of these sterile survivors increases with
the time of HO-endonuclease expression. On the other hand, the surviving colonies from the isogenic NUD1 strain are mating-proficient. Interestingly, double mutants of nud1 rad52 are more resistant to ionizing irradiation than the rad52 strain and have a cell-survival fraction of 32% for rad52-1 nud1 and 9% for rad52::URA3 nud1 following prolonged HO-endonuclease expression, indicating that nud1 has a suppressor effect on the DSB-induced lethality in rad52. Polymerase chain reaction analysis showed that many of the nud1 survivors contained small alterations within the MAT locus, suggesting that the survivors arose through the process of non-homologous end-joining. These results suggest that
the endo-exonuclease acts at a DSB to promote DNA repair via the homologous recombination pathway.
Received: 20 July / 20 September 1998 相似文献
23.
The effect of nortriptyline-specific active immunization on amitriptyline toxicity and disposition in the rabbit 总被引:1,自引:0,他引:1
Rabbits were actively immunized by a conjugate of nortriptyline (NT) to study the effect of specific anti-NT antibodies on toxicity and disposition of amitriptyline (AT). Control and immunized rabbits received 115 mg/kg AT intraperitoneally (i.p.). The lethality dose (LD) profile exhibited a gentle slope; LD100 and LD0 were separated by 100 mg/kg. Mortality was significantly reduced from LD67 to LD43 (P less than 0.05). Total plasma concentrations of the toxin were increased in the immunized group compared to the control group. AUC0.5-24 h value was 5-fold higher in the immunized group than in the control group. Moreover, a smaller fraction of unbound toxin in plasma was observed in the immunized group than in the control group. These observations indicate that AT was actively sequestered by antibodies. The intensity of this phenomenon was a function of both the antibody affinity constant (10(9) M-1) and the neutralizing capacity (varying from 0.005 to 0.2 mg/kg) of the circulating antibodies in each immunized rabbit. Results clearly show that anti-NT antibodies are able to effectively sequestrate AT. 相似文献
24.
Denis O'Mullane PhD ; Helen P. Whelton PhD ; Pat Costelloe BDS David Clarke BDS ; Stephen McDermott MSc ; Jacinta McLoughlin MDS 《Journal of public health dentistry》1996,56(5):259-264
The visit of Dr. Trendley Dean to Dublin in the mid-1950s helped accelerate the decision to introduce water fluoridation as a public health measure in the prevention of caries in the Republic of Ireland. A challenge to the constitutional validity of the Health (Fluoridation of Water Supplies) Act 1960 failed and in 1964 the water supplies of Dublin city were fluoridated. Over the next seven to eight years all the major urban communities in the Republic of Ireland were fluoridated. Currently, 67 percent of the 3.5 million people in the country reside in fluoridated communities. Studies conducted over the last 20 years show that residents of fluoridated communities have better dental health than those in nonfluoridated communities—the mean dmft is lower in children and the number of natural teeth present in adults is higher. 相似文献
25.
26.
27.
Interleukin-2 and granulocyte-macrophage colony-stimulating factor stimulate growth of a virulent strain of Escherichia coli. 总被引:2,自引:2,他引:0
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The effect of human recombinant interleukin-2 (IL-2) and human recombinant granulocyte-macrophage colony-stimulating factor on the growth of a virulent strain of Escherichia coli in tissue culture medium and in untreated, normal mouse serum was investigated. Both of these cytokines enhanced the growth of the microorganism two- to threefold in tissue culture medium with or without additional fetal calf serum and in untreated mouse serum. IL-4 did not have any effect on the growth of this microbe under the conditions tested. That the enhancement of growth seen with recombinant IL-2 was due to the active cytokine was shown by the following data: (i) addition of an antibody to IL-2 abrogated the growth-promoting effect; (ii) the excipient buffer, which contained everything except the active cytokine, was inactive in modifying bacterial growth; and (iii) heat-inactivated recombinant IL-2 did not promote enhanced microbial growth. The enhancement of growth with IL-2 was significant with concentrations as low as 1 U/ml. Growth of an avirulent strain of E. coli was not stimulated by IL-2. Moreover, addition of IL-2 to growth virulent E. coli in tissue culture medium led to rapid removal of the cytokine from the medium. Collectively, these data suggest that cytokines may act as growth factors for some virulent bacteria. 相似文献
28.
The diffusion of ofloxacin in infected and healthy human and rabbit eyes was investigated. In the human study, cataract surgery patients were given intravenous ofloxacin either as a single 200 or 400 mg dose or as two 400 mg infusions 12 hours apart. Samples of aqueous humor and plasma were collected between 1 and 12 hours after the end of the infusion. Levels in the anterior chamber increased with the dose; peak levels, which occurred after three hours, were 0.33 mg/l after 200 mg and 1.24 mg/l after two 200 mg doses given 12 hours apart. In the rabbit study, 16 hours after experimental infection of the left eye by injection of S. epidermidis into the vitreous, animals were given an intraperitoneal injection of 20 or 50 mg/kg ofloxacin. Dosages in the various ocular tissues showed that penetration into the eye varied with race (albinos greater than pigmented) and dose. Intraocular ofloxacin levels, including in the vitreous, increased two fold when the eye was infected; however, penetration into the sclera, choroid, and retina was comparable in infected and noninfected eyes. These findings in humans and animals suggest that ofloxacin in a dose of a least 400 mg is a useful agent for the treatment of prophylaxis of ocular infections. 相似文献
29.
Further experience with radiation therapy and concomitant intravenous chemotherapy in advanced carcinoma of the lower female genital tract 总被引:4,自引:1,他引:3
William S. Roberts M.D. Mitchel S. Hoffman M.D. John J. Kavanagh M.D. James V. Fiorica M.D. Harvey Greenberg M.D. Michael A. Finan M.D. Denis Cavanagh M.D. 《Gynecologic oncology》1991,43(3):233-236
Sixty-seven patients with advanced carcinoma of the lower female genital tract (cervix, vagina, and vulva) were treated with radiation and concomitant intravenous cisplatin and/or 5-fluorouracil. Fifty-seven patients (85%) responded completely clinically. Thirty-five (61%) complete responders recurred with a median time to recurrence of 6 months. Twenty-six of the thirty-five patients who recurred had some component of local failure. The 22 complete responders who have not recurred have been followed a median of 13 months. Acute toxicity was minimal, with only 6 patients requiring interruption of therapy. Nine (13%) patients developed severe late complications and eight required surgery. The actuarial 5-year survival is 22%. This treatment regimen is disappointing in terms of both survival and local control. 相似文献
30.
Human neutrophils, activated with cytokines or not, do not kill virulent Mycobacterium tuberculosis 总被引:3,自引:0,他引:3
M Denis 《The Journal of infectious diseases》1991,163(4):919-920