全文获取类型
收费全文 | 45695篇 |
免费 | 5060篇 |
国内免费 | 152篇 |
专业分类
耳鼻咽喉 | 325篇 |
儿科学 | 1349篇 |
妇产科学 | 907篇 |
基础医学 | 6290篇 |
口腔科学 | 1235篇 |
临床医学 | 5835篇 |
内科学 | 9025篇 |
皮肤病学 | 769篇 |
神经病学 | 3636篇 |
特种医学 | 1884篇 |
外国民族医学 | 1篇 |
外科学 | 6028篇 |
综合类 | 1215篇 |
一般理论 | 26篇 |
预防医学 | 5281篇 |
眼科学 | 852篇 |
药学 | 3815篇 |
中国医学 | 80篇 |
肿瘤学 | 2354篇 |
出版年
2021年 | 588篇 |
2020年 | 361篇 |
2019年 | 647篇 |
2018年 | 736篇 |
2017年 | 532篇 |
2016年 | 604篇 |
2015年 | 713篇 |
2014年 | 959篇 |
2013年 | 1388篇 |
2012年 | 1993篇 |
2011年 | 2001篇 |
2010年 | 1147篇 |
2009年 | 1109篇 |
2008年 | 1907篇 |
2007年 | 2052篇 |
2006年 | 1973篇 |
2005年 | 1898篇 |
2004年 | 1745篇 |
2003年 | 1666篇 |
2002年 | 1628篇 |
2001年 | 1556篇 |
2000年 | 1482篇 |
1999年 | 1477篇 |
1998年 | 613篇 |
1997年 | 507篇 |
1996年 | 499篇 |
1995年 | 516篇 |
1994年 | 454篇 |
1993年 | 493篇 |
1992年 | 1223篇 |
1991年 | 1133篇 |
1990年 | 1094篇 |
1989年 | 1070篇 |
1988年 | 988篇 |
1987年 | 979篇 |
1986年 | 990篇 |
1985年 | 907篇 |
1984年 | 779篇 |
1983年 | 645篇 |
1982年 | 435篇 |
1981年 | 361篇 |
1979年 | 593篇 |
1978年 | 490篇 |
1977年 | 380篇 |
1976年 | 393篇 |
1974年 | 437篇 |
1973年 | 407篇 |
1972年 | 393篇 |
1971年 | 355篇 |
1969年 | 362篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
M Powell C Koutsia-Carouzou D Voutsinas A Seymour J D Williams 《British medical journal》1987,295(6591):176-179
Between 1 January and 31 March 1986, 2434 strains of Haemophilus influenzae collected from 23 laboratories in the United Kingdom were examined. With the same criteria as previous studies in 1977 and 1981 the prevalence of resistance was: ampicillin 7.8% (6.2% beta-lactamase producers and 1.6% non-producers), tetracycline 2.7%, chloramphenicol 1.7%, trimethoprim 4.2%, and sulphamethoxazole 3.5%. of the 87 capsulated strains, 15 produced beta-lactamase, nine were resistant to ampicillin but did not produce beta-lactamase, and two strains, one of which produced beta-lactamase, were resistant to chloramphenicol and tetracycline. Since 1977 the prevalence of resistance to ampicillin, chloramphenicol, and trimethoprim has increased significantly. During 1981-6 strains resistant to ampicillin but not producing beta-lactamase and strains resistant to trimethoprim have significantly increased. 相似文献
72.
73.
74.
The first case report of systemic evenomation by the five-ringed brown snake, Pseudonaja modesta, is presented. The patient had mild general symptoms of envenomation only, with no coagulopathy or evidence of paralysis. Data on P. modesta venom is presented, which shows an absence of a coagulant component in this venom. The venom gives a positive reaction to brown snake venom in the CSL Venom Detection Kit. 相似文献
75.
76.
Lauren M. Gibbons David B. Sarwer Canice E. Crerand Anthony N. Fabricatore Robert H. Kuehnel Patti E. Lipschutz Steven E. Raper Noel N. Williams Thomas A. Wadden 《Surgery for obesity and related diseases》2006,2(2):171-164
OBJECTIVE: To describe the dieting histories of bariatric surgery candidates. RESEARCH METHODS AND PROCEDURES: One hundred seventy-seven individuals with extreme obesity who sought bariatric surgery completed the Weight and Lifestyle Inventory, a self-report instrument that assesses several variables, including weight and dieting history. Patients' dieting histories were further explored with an aided recall during a preoperative behavioral/psychological evaluation performed by a mental health professional. RESULTS: Participants who completed the Weight and Lifestyle Inventory reported an average of 4.7 +/- 2.9 successful dieting attempts, defined as those that resulted in a loss of 10 lbs (4.5 kg) or more. These individuals reported a mean total lifetime weight loss of 61.1 +/- 41.3 kg. Despite these efforts, their weight increased from 89.4 +/- 27.4 kg at the time of their first diet (age 21.2 +/- 10.1 years) to 144.5 +/- 30.8 kg at the time they underwent their behavioral/psychological evaluation (age 43.0 +/- 11.0 years). Results of the aided recall revealed that participants had made numerous other efforts to lose weight that were unsuccessful. Self-directed diets and commercial programs were used more frequently. DISCUSSION: Individuals who sought bariatric surgery reported an extensive history of dieting, beginning in adolescence, that was not successful in halting progressive weight gain. Thus, the recommendation often made by insurance companies that patients delay surgery to attempt more conservative treatment options may be unwarranted, particularly in the presence of significant obesity-related comorbidities. Weight loss histories should be routinely examined during a behavioral evaluation to determine whether additional attempts at non-surgical weight loss are advisable. Future studies also are needed to explore the potential relationship between dieting history and postoperative outcome. 相似文献
77.
T Y Nakagawa H Von Grafenstein J E Sears J Williams C A Janeway R A Flavell 《European journal of immunology》1991,21(11):2851-2855
CD4+ T cells recognize processed exogenous antigen in the form of peptides bound to syngeneic major histocompatibility complex class II molecules on antigen-presenting cells. We have developed a novel and convenient method to synthesize and map CD4+ T cell epitopes of cloned antigens using polymerase chain reaction (PCR)-directed construction of genes expressing recombinant protein fragments. Unique restriction sites incorporated into the PCR primers were employed for the unidirectional cloning of gene fragments into a bacterial expression vector that can be induced to high-level expression. The bacterial lysate could be used directly in T cell proliferation assays. Overlapping recombinant fragments spanning the entire protein were generated and tested. The length of the sequence containing the epitope was further reduced by utilizing PCR to generate 3' truncations. Finally, a small number of overlapping peptides spanning a sequence of 39 amino acids were synthesized to identify a thirteen-amino acid peptide epitope within chicken transferrin that stimulates the T helper cell clone D10.G4.1. PCR-directed construction of fragments of antigen allows for optimal design of strategies for the mapping and analysis of CD4+ T cell epitopes. 相似文献
78.
79.
80.
Influence of murine mast cell growth factor (c-kit ligand) on colony formation by mouse marrow hematopoietic progenitor cells. 总被引:7,自引:0,他引:7
H E Broxmeyer G Hangoc S Cooper D Anderson D Cosman S D Lyman D E Williams 《Experimental hematology》1991,19(2):143-146
Purified natural and recombinant murine mast cell growth factor (MGF, a c-kit ligand) were evaluated alone and in combination with other cytokines for effects in vitro on colony formation by multipotential (CFU-GEMM), erythroid (BFU-E) and granulocyte-macrophage (CFU-GM) progenitor cells from BDF1 mouse bone marrow. Both preparations stimulated Epo-dependent CFU-GEMM and enhanced Epo-dependent BFU-E colony numbers and size. MGF had some stimulating activity for CFU-GM. When used in combination with plateau concentrations of pokeweed mitogen mouse spleen cell conditioned medium or granulocyte-macrophage colony stimulating factor (CSF), MGF enhanced in greater than additive fashion colony formation by CFU-GM. MGF also enhanced the size of colonies formed, an enhancement greatest for colonies containing granulocytes and macrophages. MGF did not enhance Macrophage-CSF stimulated colony numbers or size. MGF seems to be an early acting cytokine with preferential effects on the growth of more immature hematopoietic progenitor cells. 相似文献