首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1444246篇
  免费   117240篇
  国内免费   3378篇
耳鼻咽喉   18632篇
儿科学   47549篇
妇产科学   41725篇
基础医学   205236篇
口腔科学   38534篇
临床医学   130412篇
内科学   290738篇
皮肤病学   33763篇
神经病学   119544篇
特种医学   55207篇
外国民族医学   465篇
外科学   214967篇
综合类   33664篇
现状与发展   3篇
一般理论   509篇
预防医学   114144篇
眼科学   32162篇
药学   101394篇
  1篇
中国医学   3413篇
肿瘤学   82802篇
  2021年   11318篇
  2019年   12185篇
  2018年   17136篇
  2017年   13075篇
  2016年   14723篇
  2015年   16533篇
  2014年   23249篇
  2013年   34481篇
  2012年   46970篇
  2011年   49500篇
  2010年   29076篇
  2009年   27916篇
  2008年   45764篇
  2007年   48380篇
  2006年   48911篇
  2005年   47299篇
  2004年   45129篇
  2003年   42986篇
  2002年   41412篇
  2001年   73936篇
  2000年   75417篇
  1999年   62524篇
  1998年   17439篇
  1997年   15755篇
  1996年   15923篇
  1995年   15142篇
  1994年   13699篇
  1993年   12935篇
  1992年   46693篇
  1991年   44233篇
  1990年   42232篇
  1989年   40288篇
  1988年   36889篇
  1987年   36038篇
  1986年   33566篇
  1985年   31910篇
  1984年   24391篇
  1983年   20516篇
  1982年   12523篇
  1981年   11041篇
  1979年   21105篇
  1978年   14922篇
  1977年   12363篇
  1976年   11644篇
  1975年   11864篇
  1974年   14304篇
  1973年   13826篇
  1972年   12918篇
  1971年   11738篇
  1970年   11164篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The agar-gel precipitation test (AGPT) was compared with Enzyme Immunoassay (EIA) for the detection of Chlamydia trachomatis, 164 women being screened for chlamydial antibodies and antigens in their sera and in endocervical specimens, respectively. The AGPT showed good correlation with EIA in the 164 paired sera and endocervical specimens, resulting in 27 (16.5%) and 22 (13.4%) positive results, respectively (P greater than 0.05). The overall sensitivity of the AGPT compared to EIA was 86.4% (19 of 22), and the specificity was 94.4% (134 of 142).  相似文献   
992.
This study examined the relationship between risk factors and initiation of alcohol use over a 15-month period among a cohort of 7th graders who were abstainers at the time of initial testing. The relationship between risk factors and alcohol use was examined using a discriminant function analysis. At the univariate level, rejection of parental authority, deviant behavior, and sensation seeking were statistically significant. The discriminant function retained only three of the risk factors: rejection of parental authority, deviant behavior, and religious commitment. Implications for school-based prevention programs are discussed, particularly the need to target primary prevention programs based upon adolescents' risk.  相似文献   
993.
Stereoisomers of remacemide (racemate form) were compared for anticonvulsant efficacy and safety in mice. In the maximal electroshock seizure (MES) test for oral efficacy, the (-) stereoisomer, FPL 14145, was more potent than the racemate or the (+) stereoisomer, FPL 14144. Respective ED50 values (expressed as mg/kg) were: remacemide, 58; FPL 14145, 45; FPL 14144, 79. In 2 of 3 tests for neural impairment, FPL 14145 yielded significantly better therapeutic indices (toxic dose 50/ED50) than the racemate. The margin of safety (estimated median lethal dose ED50) was more favorable for FPL 14144: remacemide, 15.1; FPL 14144, 18.9; FPL 14145, 15.7. The duration of protection against MES indicated the stereoisomers were longer acting than the racemate. After intravenous administration the order of potency against MES was similar: FPL 14145 greater than remacemide greater than FPL 14144. Following daily administration of the oral ED98 for 4 days, with a dose response curve run on day 5, the MES ED50 values for all compounds were increased. The test indicates tolerance. In the pentylenetetrazol infusion test the racemate and FPL 14144 demonstrated more proconvulsant properties than FPL 14145. Intraperitoneal administration of 50 mg/kg or more produced changes in behavior with all compounds. At higher doses the racemate and FPL 14145 elicited more severe symptoms with death at 200 mg/kg.  相似文献   
994.
In the present study, we have chemically synthesized peptides which correspond to the four putative extracellular domains of the predicted substance K (SK) receptor protein and raised specific polyclonal antibodies against these peptides. These antibodies were then tested for both structural and functional recognition of epitopes on the substance P (SP) receptor on rat AR42J pancreatic cells and human IM9 lymphoblasts, which express the SP receptor, but not the SK receptor. Antibodies directed against the first, second, and fourth external domains of the predicted SK receptor recognized a 58-kDa protein on AR42J cells. This protein has a molecular weight similar to the previously demonstrated SP receptor on both AR42J cells and IM9 cells. Furthermore, antibodies against the second and fourth extracellular domains significantly inhibited specific 125I-SP binding on both AR42J and IM9 cells, and also significantly inhibited SP-induced mobilization of [Ca2+]i on AR42J cells. These data suggest that the second and fourth extracellular domains of the SK and SP receptors may share common structural motifs for ligand binding and signaling mechanism.  相似文献   
995.
996.
Demographic and clinical data are presented on 4,138 veterans assessed in the 20-site Department of Veterans Affairs (VA) Domiciliary Care for Homeless Veterans program during its first year of operation. More than two-thirds of the veterans who were screened had been hospitalized in VA medical centers during the year before assessment, and 34 percent were hospitalized at the time of assessment. Compared with veterans who were not admitted for residential treatment, veterans who were admitted were more likely to be previously involved in mental health treatment, literally homeless rather than at risk for homelessness, and without public financial support. Specialized service programs for the homeless such as the VA domiciliary care program may also be called on to play a broader role in the discharge and rehabilitative efforts of public mental health service systems.  相似文献   
997.
BACKGROUND. A health risk appraisal (HRA) is a tool for health promotion. Conversational microcomputer-based HRAs may be more cost effective than other HRA formats. The acceptability of conversational HRAs, however, has not been demonstrated for older adults. METHODS. We studied the acceptability of a conversational microcomputer-based HRA in a sample of 247 adults at the Minnesota State Fair and the Senior Options Exposition. All users were offered the appraisal via mouse or keyboard interface. Acceptability was measured in terms of user-reported helpfulness, intent to change, time of use, and willingness to view HRA health recommendations. Data on completion time and willingness to view HRA recommendations were collected for Senior Exposition users only. Regression analyses were used to examine the combined impact of interface (mouse or keyboard), location (State Fair or Senior Exposition), age, and sex on user acceptability. Results. Interface and location had no effect on helpfulness or change ratings. Older users rated the appraisal more helpful (P less than .007). Both older and female users reported more intent to change behavior (P = .016, both). Time to use the appraisal was related to interface, age, and sex. Mouse users (P less than .0001), older users (P less than .0001) and female users (P less than .05) took significantly longer to use the appraisal. Significantly more mouse users declined to see recommendations (P less than .02). CONCLUSIONS. Older users can derive as much or more value from conversational health risk appraisals as younger users; however, a mouse interface may be less effective for this age group.  相似文献   
998.
Multiphase radon generation and transport in porous materials   总被引:5,自引:0,他引:5  
Radon generation and transport in porous materials involve solid, liquid, and gas phases in the processes of emanation, diffusion, advection, absorption, and adsorption. Oversimplifications, such as representing moist soil systems by air-phase emanation and transport models, cause theoretical inconsistencies and biases in resulting calculations. Detailed Rn rate balance equations for solid, liquid, and gas phases were analyzed and combined using phase equilibrium constants to derive a single diffusive-advective rate balance equation in the traditional form. The emanation, diffusion, and permeability coefficients in the new equation have expanded definitions and interpretations to include Rn phase transfer. Radon adsorption was characterized by an exponential moisture dependence, and diffusion and permeability constants utilized previous moisture relationships. Correct boundary and interface conditions were defined, and the unified theoretical approach was applied to field data from a diffusion-dominated system and to laboratory data from an advection-dominated system. Measured 222Rn fluxes and concentrations validated the modeled values within the measurement variability in both applications.  相似文献   
999.
Thirteen patients with a malignant germ cell tumor of the ovary have been treated with a combination of vinblastine, bleomycin, and cisplatin (VBP). In 12 patients a complete remission was reached, which was maintained in 10 of these patients. One patient with large tumor residues and a partial remission became CR after surgery. The tumor recurred in 2 patients after 6 and 27 months. Overall, 11 of these patients are in long-term remission, from 14 to 84 months after the start of treatment. VBP is an effective treatment for malignant germ cell tumors of the ovary, even in patients with large tumor residuals.  相似文献   
1000.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号