全文获取类型
收费全文 | 7428篇 |
免费 | 424篇 |
国内免费 | 9篇 |
专业分类
耳鼻咽喉 | 93篇 |
儿科学 | 249篇 |
妇产科学 | 211篇 |
基础医学 | 1105篇 |
口腔科学 | 372篇 |
临床医学 | 674篇 |
内科学 | 1365篇 |
皮肤病学 | 247篇 |
神经病学 | 765篇 |
特种医学 | 337篇 |
外科学 | 1118篇 |
综合类 | 53篇 |
一般理论 | 10篇 |
预防医学 | 406篇 |
眼科学 | 56篇 |
药学 | 417篇 |
中国医学 | 9篇 |
肿瘤学 | 374篇 |
出版年
2021年 | 111篇 |
2020年 | 77篇 |
2019年 | 87篇 |
2018年 | 114篇 |
2017年 | 100篇 |
2016年 | 115篇 |
2015年 | 125篇 |
2014年 | 160篇 |
2013年 | 229篇 |
2012年 | 362篇 |
2011年 | 362篇 |
2010年 | 210篇 |
2009年 | 207篇 |
2008年 | 334篇 |
2007年 | 340篇 |
2006年 | 322篇 |
2005年 | 330篇 |
2004年 | 287篇 |
2003年 | 276篇 |
2002年 | 312篇 |
2001年 | 264篇 |
2000年 | 227篇 |
1999年 | 209篇 |
1998年 | 88篇 |
1997年 | 74篇 |
1996年 | 68篇 |
1995年 | 57篇 |
1994年 | 58篇 |
1993年 | 54篇 |
1992年 | 116篇 |
1991年 | 100篇 |
1990年 | 103篇 |
1989年 | 111篇 |
1988年 | 97篇 |
1987年 | 120篇 |
1986年 | 102篇 |
1985年 | 88篇 |
1984年 | 77篇 |
1983年 | 70篇 |
1982年 | 52篇 |
1978年 | 57篇 |
1977年 | 51篇 |
1976年 | 61篇 |
1973年 | 53篇 |
1971年 | 48篇 |
1969年 | 47篇 |
1968年 | 47篇 |
1966年 | 51篇 |
1933年 | 45篇 |
1932年 | 47篇 |
排序方式: 共有7861条查询结果,搜索用时 156 毫秒
91.
Catry B Haesebrouck F Vliegher SD Feyen B Vanrobaeys M Opsomer G Schwarz S Kruif AD 《Microbial drug resistance (Larchmont, N.Y.)》2005,11(4):387-394
To measure the level of antimicrobial resistance in potential bovine respiratory pathogens at different production types, nasal swabs were collected from 57 calves of 13 dairy herds, 150 calves of 9 beef cattle herds, and 289 calves of 5 high-density veal calf herds and investigated for the presence of Pasteurellaceae. All calves were less than 6 months old. Susceptibilities of the Pasteurella and Mannheimia isolates to eight antimicrobials were determined using an agar dilution method. P. multocida (37.3%) and hemolytic Mannheimia organisms (M. haemolytica sensu lato) (6.3%) were the most frequently detected organisms. The overall prevalence of isolates resistant to at least one antimicrobial from the dairy, beef, and veal calves were 17.6% (6/34), 21.9% (14/64), and 71.9% (64/89), respectively. In isolates obtained on the veal calf herds, acquired resistance to ampicillin, oxytetracycline, potentiated sulfonamides, gentamicin, tilmicosin, and enrofloxacin was frequently present, and 32.6% of these isolates were resistant to more than two of the tested antimicrobials. Resistance to ceftiofur and florfenicol was not detected. A substantial within-herd variability of species diversity and resistance profiles among isolates belonging to the genera Pasteurella and Mannheimia was found among the isolates of the veal calf farms. 相似文献
92.
Hans R. Kricheldorf Colin von Lossow Gert Schwarz 《Macromolecular chemistry and physics.》2004,205(7):918-924
Summary: Sarcosine‐N‐carboxyanhydride (Sar‐NCA), L ‐alanine‐NCA and D,L ‐alanine‐NCA were polymerized with benzylamine as initiator in three different solvents: dichloromethane (CH2Cl2), 1,4‐dioxane and dimethylformamide (DMF). The isolated polyaminoacids were characterized by 1H NMR spectroscopy and MALDI‐TOF mass spectrometry. High conversions and degrees of polymerization s close to the monomer‐initiator (M/I) ratios were found for all polypeptides. For polysarcosine which was soluble under the given reaction conditions a narrow monomodal frequency distribution was found. In contrast, a broad frequency distribution was observed, when L ‐alanine NCA was polymerized in dioxane and DMF. These results were attributed to a partial precipitation of oligopeptides in the β‐sheet structure, which reduces the reactivity of endgroups for steric reasons. The polymerizations of D,L ‐alanine‐NCA showed features in between the extremes of Sar‐NCA and L ‐Ala‐NCA.
93.
After serial passage of adenovirus type 12 in cells of the human melanoma line Nki4 virus mutants with enhanced growth potential have been isolated which carry additional sequences of regularly increasing size at the right end of the genome. DNA sequence analysis was performed'to characterize these genomic alterations as well as those of the previously described Ad12 mutants adapted to growth in the human carcinoma cell line (I. Kruczek, E. Schwarz, and H. zur Hausen (1981)Int. J. Cancer27, 139–143). Duplication of the inverted terminal repetition (ITR) emerged as the common feature of the right terminal alterations of all the mutant genomes analyzed. The sequences present between the ITR repeats were of either right-end or left-end origin, the latter suggesting that left-end sequences comprising the ITR and parts of the adjacent unique sequences have been transferred to the right end of the genome. The different sizes of the additional sequences in Ad12 Nki-4 DNA could be explained by varying degrees of amplification of a basic additional sequence of 342 base pairs. 相似文献
94.
Experimental pneumococcal meningitis: impaired clearance of bacteria from the blood due to increased apoptosis in the spleen in Bcl-2-deficient mice 下载免费PDF全文
Wellmer A von Mering M Spreer A Diem R Eiffert H Noeske C Bunkowski S Gold R Nau R 《Infection and immunity》2004,72(6):3113-3119
Necrotic and apoptotic neuronal cell death can be found in pneumococcal meningitis. We investigated the role of Bcl-2 as an antiapoptotic gene product in pneumococcal meningitis using Bcl-2 knockout (Bcl-2(-/-)) mice. By using a model of pneumococcal meningitis induced by intracerebral infection, Bcl-2-deficient mice and control littermates were assessed by clinical score and a tight rope test at 0, 12, 24, 32, and 36 h after infection. Then mice were sacrificed, the bacterial titers in blood, spleen, and cerebellar homogenates were determined, and the brain and spleen were evaluated histologically. The Bcl-2-deficient mice developed more severe clinical illness, and there were significant differences in the clinical score at 24, 32, and 36 h and in the tight rope test at 12 and 32 h. The bacterial titers in the blood were greater in Bcl-2-deficient mice than in the controls (7.46 +/- 1.93 log CFU/ml versus 5.16 +/- 0.96 log CFU/ml [mean +/- standard deviation]; P < 0.01). Neuronal damage was most prominent in the hippocampal formation, but there were no significant differences between groups. In situ tailing revealed only a few apoptotic neurons in the brain. In the spleen, however, there were significantly more apoptotic leukocytes in Bcl-2-deficient mice than in controls (5,148 +/- 3,406 leukocytes/mm2 versus 1,070 +/- 395 leukocytes/mm2; P < 0.005). Bcl-2 appears to counteract sepsis-induced apoptosis of splenic lymphocytes, thereby enhancing clearance of bacteria from the blood. 相似文献
95.
96.
Hans R. Kricheldorf Sigrid Bhme Gert Schwarz Claus‐Ludolf Schultz 《Macromolecular chemistry and physics.》2003,204(13):1636-1642
The hydrolytic interfacial polycondensation of bisphenol‐A‐bischloroformate was performed with four different phase‐transfer (PT) catalysts: N‐butylpyridinium bromide, triethylbenzylammonium (TEBA) chloride, tetrabutylammonium hydrogen sulfate, and tetraphenylphosphonium bromide. These polycondensations were conducted at 5 or 35 °C initial reaction temperature. The resulting polycarbonates were characterized by viscosity and SEC measurements and by MALDI‐TOF mass spectrometry. The four PT catalysts gave quite different results with respect to molecular weight and formation of cyclic polycarbonates. The highest molecular weights (number average, and weight average, ) were obtained with TEBA‐Cl. Lower temperatures and high feed ratios of TEBA‐Cl proved to be favorable for both high molecular weights and high fractions of cycles. Cyclic polycarbonates were detectable in the mass spectra up to 14 kDa (technical limit of the measurements). Low molecular weights in combination with unreacted chloroformate groups proved that the other PT‐catalysts were less efficient under the given reaction conditions.
97.
Rapid tracheal intubation with vecuronium: the priming principle 总被引:4,自引:0,他引:4
Following the administration of a single 0.1 mg/kg dose of vecuronium bromide, satisfactory conditions for tracheal intubation developed in 156 +/- 12 s (mean +/- SEM), and the clinical duration of the initial dose was 36 +/- 2 min. When the initial dose of vecuronium was administered in two increments, a 0.015 mg/kg "priming" dose, followed 6 min later by a 0.050 mg/kg "intubating" dose, intubation time decreased to 61 +/- 3 s and clinical duration to 21 +/- 1 min. The priming dose that had no unpleasant effect on premedicated, awake patients could be administered 3-4 min before, and the intubating dose 2 to 3 min after induction of anesthesia. With the described technique, comparable intubating conditions could be obtained just as rapidly with vecuronium as with succinylcholine chloride, without subjecting the patients to the side effects of and the complications occasionally encountered with succinylcholine. An added advantage of the use of a priming dose is that it will reveal undiagnosed, pathologic, or idiopathic increase of sensitivity to nondepolarizing muscle relaxants. 相似文献
98.
Report on 178 rearthrotomies of the knee joint in 158 patients. Most of these rearthrotomies became necessary subsequent to meniscus operations. A review of the literature shows that these are mainly persisting or recurring complaints appearing usually under the overall pattern of "irritable knee". The principal causes were found to be leftover meniscus residues; on rarer occasions degenerative meniscus regenerates were found, or other causes such as floating cartilage, damaged cartilage of the patella, and instabilities of the condyles and of the ligaments. 相似文献
99.
Knowing the epitope specificities of our monoclonal antibodies (MCA) to human choriogonadotropin (hCG), we could design three classes of two-site immunoradiometric assays (IRMA): a combination of two MCA recognizing two separate alpha-epitopes (alpha-MCA) provides a system (i.e., an alpha-IRMA) that measures holo-hCG plus free alpha-subunits plus follitropin, lutropin, and thyrotropin, whereas a beta-IRMA, consisting of two beta-MCA, quantifies holo-hCG plus free beta-subunits. The amount of either of the two subunits can be calculated by subtracting the amount of holo-hCG determined in parallel in a holo-hCG-IRMA. In the latter, one of the alpha- or beta-MCA may be either cross-combined or, preferably, paired with an MCA specific for a conformational epitope. These analytical specificities, predicted from our previously established epitope map of hCG, could be experimentally verified. With these IRMAS we could demonstrate that in certain choriocarcinoma cell lines the earliest and quantitatively predominant tumor marker is the free alpha-subunit. Similar results showing an unbalanced secretion of hCG and its subunits were obtained for patients with related tumors. These findings challenge the present diagnostic practice of relying solely on "beta-hCG" radioimmunoassays and at the same time offer a novel analytical strategy. 相似文献
100.
Magdalena Hoffmann Christine Maria Schwarz Stefan Fürst Christina Starchl Elisabeth Lobmeyr Gerald Sendlhofer Marie-Madlen Jeitziner 《Nutrients》2021,13(1)
Critically ill patients in the intensive care unit (ICU) have a high risk of developing malnutrition, and this is associated with poorer clinical outcomes. In clinical practice, nutrition, including enteral nutrition (EN), is often not prioritized. Resulting from this, risks and safety issues for patients and healthcare professionals can emerge. The aim of this literature review, inspired by the Rapid Review Guidebook by Dobbins, 2017, was to identify risks and safety issues for patient safety in the management of EN in critically ill patients in the ICU. Three databases were used to identify studies between 2009 and 2020. We assessed 3495 studies for eligibility and included 62 in our narrative synthesis. Several risks and problems were identified: No use of clinical assessment or screening nutrition assessment, inadequate tube management, missing energy target, missing a nutritionist, bad hygiene and handling, wrong time management and speed, nutritional interruptions, wrong body position, gastrointestinal complication and infections, missing or not using guidelines, understaffing, and lack of education. Raising awareness of these risks is a central aspect in patient safety in ICU. Clinical experts can use a checklist with 12 identified top risks and the recommendations drawn up to carry out their own risk analysis in clinical practice. 相似文献