全文获取类型
收费全文 | 3533篇 |
免费 | 366篇 |
国内免费 | 4篇 |
专业分类
3903篇 |
出版年
2023年 | 16篇 |
2022年 | 30篇 |
2021年 | 66篇 |
2020年 | 28篇 |
2019年 | 53篇 |
2018年 | 60篇 |
2017年 | 41篇 |
2016年 | 88篇 |
2015年 | 148篇 |
2014年 | 179篇 |
2013年 | 191篇 |
2012年 | 265篇 |
2011年 | 250篇 |
2010年 | 169篇 |
2009年 | 146篇 |
2008年 | 209篇 |
2007年 | 197篇 |
2006年 | 184篇 |
2005年 | 187篇 |
2004年 | 178篇 |
2003年 | 157篇 |
2002年 | 145篇 |
2001年 | 87篇 |
2000年 | 62篇 |
1999年 | 56篇 |
1998年 | 46篇 |
1997年 | 33篇 |
1996年 | 25篇 |
1995年 | 29篇 |
1994年 | 24篇 |
1993年 | 27篇 |
1992年 | 29篇 |
1991年 | 22篇 |
1990年 | 21篇 |
1989年 | 18篇 |
1988年 | 23篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 19篇 |
1984年 | 21篇 |
1983年 | 22篇 |
1982年 | 17篇 |
1981年 | 21篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1975年 | 18篇 |
1974年 | 14篇 |
1973年 | 17篇 |
1971年 | 20篇 |
1969年 | 22篇 |
排序方式: 共有3903条查询结果,搜索用时 15 毫秒
21.
22.
K B?hler-Sommeregger S Schuller-Petrovic R Neumann E Müller 《Plastic and reconstructive surgery》1992,90(3):436-40; discussion 441-4
Lentigo maligna denotes flat, pigmented lesions predominantly in areas of actinic damage that have the propensity to become malignant. More than 10 years may pass before lentigo maligna evolves into an invasive neoplasma. As an invasive process, it is termed lentigo maligna melanoma (LMM), and it has the potential for both lymphatic and hematogenic metastases. Because of the size and location of the lesions, cosmetically unsatisfactory scars may result from conventional surgery. Therefore, alternative means of treatment, including cryosurgery, have been employed. We report on 12 patients suffering from lentigo maligna who had been treated successfully by cryosurgery between 1984 and 1990. The average follow-up period was 51.4 months, and the recurrence rate was 8.3 percent. Knowing that microinvasive components can be demonstrated in 15 percent of lentigo maligna lesions, we retrospectively reassessed our patients by immunohistochemical procedures with S-100 protein. Although intradermal microinvasion could be confirmed in one patient, no recurrence had been observed within 61 months of follow-up. Provided that patients are selected properly and extension of cryonecrosis is monitored, cryosurgery may prove an efficient alternative to conventional surgery in the treatment of lentigo maligna. 相似文献
23.
This experiment consisted of a 2 year drylot study involving 80 multiparous, suckled beef cows (40 Angus and 40 Herefords). Experimental treatments (breed, monensin and year) were arranged in 2(3) factorial to evaluate the effect of breed and monensin on reproductive performance and lactation. Cows received 85% of the NRC total digestible nutrient (TDN) requirement for the first 56 days of the 140 day trial. Cows were synchronized with Synchro-Mate B and artificially inseminated 30 days into each trial with blood samples collected for luteinizing hormone (LH) analysis from one-half of each treatment group from 24 to 36 hours after implant removal. Progesterone determinations were made on plasma samples collected at day 9 and 16 after implant removal. On day 56, milk yield estimates were obtained by the weigh-suckle-weight technique. Following these collections, energy levels were increased by allowing ad lib consumption of forage. Calves, which were removed from the cows during feeding, were given access to a 75% TDN creep ration after day 56. Milk estimates were again evaluated at 140 days. Monensin supplementation did not result in a difference in cow weight change through the restricted energy period (first 56 days) or throughout the entire 140 day period. Milk yield estimates at 56 and 140 days and calf gains throught the trial, were unaffected by monensin supplementation. Monensin resulted in no effect on conception rate or services per conception. The time of the LH peak was shifted slightly forward by monensin although not significantly. Progesterone levels were not consistently affected by monensin supplementation. 相似文献
24.
A commercially available haemagglutination inhibition test kit for routine analysis of erythropoietin was shown to be unable to detect elevated levels of serum Epo. 相似文献
25.
26.
V D Michaelis I Neumann B Schulz W Nowak W K?cher R Michael P Heinke R Reding 《Endokrinologie》1975,64(3):257-268
In 8 female patients carbohydrate tolerance was proved by means of glucose infusion test 3 days after cholecystectomy. Parameters analyzed in portal and peripheral vein blood are compared with that of 47 healthy persons. All patients demonstrate a pathological carbohydrate tolerance after cholecystectomy, further characterized by an increased lipolysis, a paradoxical rise of HGH, a diminished insulin secretion during the early and increased IRI output in the second phase. There is a significant positive correlation between portal and peripheral vein IRI concentration despite the rising portalperipheral venous IRI difference with raised portal venous IRI concentration. Corresponding differences for proinsulin concentrations can be established in the early phase only. Relations existing between blood glucose and IRI are shown by multiple regression analysis. They suggest that the altitude of IRI concentration is determined by previous blood glucose concentration. 相似文献
27.
55 patients with pathological glucose tolerance received a long term treatment with buformin (200 mg daily). In 43 of the protodiabetics the duration of treatment was one year, in 29 of them two years and in 11 three years. The age of the patients was 38 years and the mean relative body weight was 118 per cent. The effect of buformin on glucose tolerance and insulin secretion was tested with the glucose infusion test before and after the periods of treatment. After one year we found in 58 per cent, after two years in 69 per cent and after three years in 64 per cent of the protodiabetics an improvement of glucose tolerance. In these groups the results showed a rise of the IRI in the low responder and a decrease of the IRI in the high responder. The good effects on glucose tolerance were not demonstrable in the compared groups with long-term treatment of diet only. 相似文献
28.
Uncoupling photophosphorylation by detergents 总被引:4,自引:0,他引:4
29.
30.
L1 is sequentially processed by two differently activated metalloproteases and presenilin/gamma-secretase and regulates neural cell adhesion, cell migration, and neurite outgrowth 下载免费PDF全文
Maretzky T Schulte M Ludwig A Rose-John S Blobel C Hartmann D Altevogt P Saftig P Reiss K 《Molecular and cellular biology》2005,25(20):9040-9053
The immunoglobulin superfamily recognition molecule L1 plays important functional roles in the developing and adult nervous system. Metalloprotease-mediated cleavage of this adhesion molecule has been shown to stimulate cellular migration and neurite outgrowth. We demonstrate here that L1 cleavage is mediated by two distinct members of the disintegrin and metalloprotease family, ADAM10 and ADAM17. This cleavage is differently regulated and leads to the generation of a membrane bound C-terminal fragment, which is further processed through gamma-secretase activity. Pharmacological approaches with two hydroxamate-based inhibitors with different preferences in blocking ADAM10 and ADAM17, as well as loss of function and gain of function studies in murine embryonic fibroblasts, showed that constitutive shedding of L1 is mediated by ADAM10 while phorbol ester stimulation or cholesterol depletion led to ADAM17-mediated L1 cleavage. In contrast, N-methyl-d-aspartate treatment of primary neurons stimulated ADAM10-mediated L1 shedding. Both proteases were able to affect L1-mediated adhesion and haptotactic migration of neuronal cells. In particular, both proteases were involved in L1-dependent neurite outgrowth of cerebellar neurons. Thus, our data identify ADAM10 and ADAM17 as differentially regulated L1 membrane sheddases, both critically affecting the physiological functions of this adhesion protein. 相似文献